Regulatory Guide 5.27: Difference between revisions

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{{Adams
{{Adams
| number = ML14290A268
| number = ML003740050
| issue date = 07/23/2015
| issue date = 06/30/1974
| title = Rev. 1, Special Nuclear Material Doorway Monitors
| title = Special Nuclear Material Doorway Monitors
| author name = Tardiff A
| author name =  
| author affiliation = NRC/NSIR
| author affiliation = NRC/RES
| addressee name =  
| addressee name =  
| addressee affiliation =  
| addressee affiliation =  
| docket =  
| docket =  
| license number =  
| license number =  
| contact person = Jervey R
| contact person =  
| case reference number = DG-5038
| document report number = RG-5.27
| document report number = RG-5.027 Rev 1
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 14
| page count = 12
}}
}}
{{#Wiki_filter:U.S. NUCLEAR REGULATORY COMMISSION                                                                  July 2015 OFFICE OF NUCLEAR REGULATORY RESEARCH                                                                 Revision 1 REGULATORY GUIDE                                                                              Technical Lead A. Tardiff REGULATORY GUIDE 5.27 (Draft was issued as DG-5038, dated March 2014)
{{#Wiki_filter:June 1974 U.S. ATOMIC ENERGY COMMISSION
        SPECIAL NUCLEAR MATERIAL DOORWAY MONITORS
                              REGULATORY                                                                                     GUIDE
                              DIRECTORATE OF REGULATORY STANDARDS
                                                                 REGULATORY GUIDE 5.27 SPECIAL NUCLEAR MATERIAL DOORWAY MONITORS


==A. INTRODUCTION==
==A. INTRODUCTION==
Purpose The U.S. Nuclear Regulatory Commission (NRC) developed this regulatory guide (RG) to describe a method that the NRC staff considers acceptable to implement the search requirement for concealed special nuclear material (SNM) applied to personnel, vehicles, packages and all other materials exiting a material access area (MAA).
2. General Characteristics Typically, the detectors of a doorway monitor are Paragraph (b), "Exit Requirement," of § 73.60, "Ad                                NaI(Tl) scintillators or solid or liquid organic scintilla ditional Requirements for the Physical Protection of                                 tors. Geiger-Mueller detectors have also been used in this Special Nuclear Material at Fixed Sites," of 10 CFR Part                             application, although the lower intrinsic efficiency of
          For holders of a reactor license under Title 10 of the Code of Federal Regulations (10 CFR)
73, "Physical Protection of Plants and Materials,"
Part 50, Domestic Licensing of Production and Utilization Facilities (Ref. 1), a combined license under
                                                                                      these detectors renders them less suitable than scintilla requires that individuals exiting from material access tion detectors.
10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants (Ref. 2), or a fuel cycle facility license under 10 CFR Part 76, Certification of Gaseous Diffusion Plants (Ref. 3), having the need to possess or use SNM within their facility, the NRC typically has included in their license a condition granting a general license to use SNM under 10 CFR Part 70, Domestic Licensing of Special Nuclear Material.


Applicable Rules and Regulations The requirements for physical protection found within 10 CFR Parts 50, 52, 70, and 76 refer to the physical protection requirements of 10 CFR Part 73, Physical Protection of Plants and Materials.
areas be searched for concealed special nuclear material Detectors are arranged such that a detection area is (SNM). This guide describes means acceptable to the Regulatory staff for employing SNM doorway monitors defined by a plane perpendicular to the line of passage of individuals through the doorway monitor. Various to comply with that requirement.


Part 73 (Ref. 4) requires, in part, in 10 CFR 73.46(d)(9) and 10 CFR 73.60(b), that each individual, package, materials and vehicle exiting an MAA is searched for concealed SNM. Specific testing and maintenance requirements, as stated in 10 CFR 73.20(b)(4), 10 CFR 73.46(g), and 10 CFR 73.60(d)(1)
arrangements of the detectors are possible; however, specific placement of detectors is usually dictated by the  
also apply.
 
Related Guidance
      *    Regulatory Guide 5.7, Entry/Exit Control of Personnel Access to Protected Areas, Vital Areas, and Material Access Areas (Ref. 5)
      *    NUREG 1964, Access Control Systems: Technical Information for NRC Licensees (Ref. 6)
Written suggestions regarding this guide or development of new guides may be submitted through the NRCs public Web site under the Regulatory Guides document collection of the NRC Library at http://www.nrc.gov/reading-rm/doc-collections/reg-guides/contactus.html.
 
Electronic copies of this regulatory guide, previous versions of this guide, and other recently issued guides are available through the NRCs public Web site under the Regulatory Guides document collection of the NRC Library at http://www.nrc.gov/reading-rm/doc-collections/. The regulatory guide is also available through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under ADAMS Accession No. ML14290A268. The regulatory analysis may be found in ADAMS
under Accession No. ML12237A124 and the staff responses to the public comments on DG-5038 may be found under ADAMS Accession No.
 
ML14288A653.
 
Purpose of Regulatory Guides The NRC issues RGs to describe to the public methods that the staff considers acceptable for use in implementing specific parts of the agencys regulations, to explain techniques that the staff uses in evaluating specific problems or postulated accidents, and to provide guidance to applicants. Regulatory guides are not substitutes for regulations and compliance with them is not required. Methods and solutions that differ from those set forth in RGs will be deemed acceptable if they provide a basis for the findings required for the issuance or continuance of a permit or license by the Commission.
 
Information Collection Requirements This RG contains information collection requirements covered by 10 CFR Part 73, Physical Protection of Plants and Materials, that the Office of Management and Budget (OMB) approved under OMB control number 3150-0002. The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number.


==B. DISCUSSION==
==B. DISCUSSION==
Reason for Revision This RG is being revised because it was out-of-date with current related guidance and references in the CFR. Related specifications and standards for SNM monitors and metal detectors have been updated or developed since the previous revision was issued in 1974. This revision has been developed to provide detection practices and criteria that licensees may use to demonstrate compliance with NRC
need to eliminate dead spots.
regulations in 10 CFR Part 73 and to augment programmatic information within the general reference, NUREG-1964, Access Control Systems: Technical Information for NRC Licensees, (Ref. 6) issued in April of 2011.


Background Special nuclear material doorway monitors provide an efficient, sensitive, and reasonably unobtrusive way of searching individuals for concealed SNM upon exit from an MAA. With proper installation and operation, gram quantities or less of SNM can be detected with a high level of reliability while maintaining a low false alarm rate. Portal type walk-through metal detectors are often used in conjunction with radiation detection to assure that personnel entering or leaving MAAs are screened for metallic nuclear shielding materials.
Special nuclear material doorway monitors provide an                                   Some commercially available doorway monitors are efficient, sensitive, and reasonably unobtrusive means of                             equipped with an automatic background updating searching individuals exiting from a material access area                              system. The automatic background updating system for concealed SNM. With proper installation and opera                                  periodically monitors and averages the background. A
tion, gram quantities or less of SNM can be detected                                   doorway monitor equipped with an automatic back with a high level of reliability while maintaining a low                               ground updating system is also provided with a treadle false alarm rate.                                                                     pad or beam-break system to indicate that the sensitive area is occupied. When the sensitive area is occupied, the I. Theory of Operation                                                                radiation level detected by the doorway monitor is The doorway monitor is composed of a detector                                      compared with the mean background. If the level is unit(s), associated electronics, and alarm logic. The                                  "significantly" greater than the mean background, an detector unit(s) is sensitive to the radiations which                                  alarm condition ensues. Significance is usually deter emanate from the SNM and responds to these radiations                                  mined by comparing the radiation level when the (usually gamma rays) by generating current pulses. These                              sensitive area is occupied with the mean background plus pulses are amplified, filtered, and fed to alarm logic                                some multiple of the square root of the mean back v'hich interprets the number (or rate) of pulses in some                              ground*
period of time, for example, one second. The alarm logic may be either a digital or analog system; in either case, if                          *The square root of the mean of a Poisson-distributed quantity the number (or rate) of pulses exceeds a set level, an                                  is the unbiased estimate of the standard deviation of that alarm condition ensues.                                                                  quantity.


Theory of Operation The doorway monitor comprises one or more detector unit(s), associated electronics, and alarm logic. The detector units are sensitive to the SNM radiation and responds to the emitted radiation (gamma rays and neutrons) by generating electronic current pulses. These pulses are amplified, filtered, and fed to alarm logic circuits that interpret the number (or rate) of pulses during a sampling. The alarm logic may be either a digital or analog system. In either case, if the rate of pulses exceed a set level, the alarm is triggered. Additional information pertaining to detector theory can be found in Knolls, Radiation Detection and Measurement. (Ref.7)
USAEC REGULATORY GUIDES                                      Copies of published guides may be obtained by request indicating the divisions desired to the US. Atomic Energy Commission, Washington, D.C. 20545, Regulatory Guides are issued to describe and make available to the public          Attention: Director of Regulatory Standards. Comments and suggestions for methods acceptable to the AEC Regulatory staff of implementing sPecific parts of   improvements in these guides ae encouraged and should be sent to the Secretary the Commission's regulations, to delineate techniques .ned by the staff in          of the Commission, US. Atomic Energy Commission, Washington, D.C. 20545, evaluating specific problems or postulated accidents, or to provide guidance to    Attention: Chief, Public Proceedings Staff.
                                            RG 5.27, Rev. 1, Page 2


General Characteristics Doorway Monitors Doorway monitors detect gamma-ray radiation using scintillation or semiconductor detectors. To detect neutrons, plastic scintillators or gas-filled proportional counters are used. Geiger-Mueller counters have been used in this application; however, their lower intrinsic efficiency renders them less suitable than scintillation detectors. Scintillation detectors are often used for discriminating pulses based on imparted energy. Plastic scintillation detectors have the advantage of responding well to gamma-ray and energetic neutrons whereas the sodium iodide thallium-activated NaI(Tl) scintillation detectors have good gamma-ray sensitivity but poor neutron response. Helium-3 (He-3) gas is used in tubes as a proportional counter for neutron detection. The trend in industry is to use both scintillation detectors and He-3 detectors for doorway monitor systems.
applicants. Regulatory Guides are not substitutes for regulations and compliance with them is not required. Methods and solutions different from those set out in    The guides ae issued in the following ten broad divisions:
the guides will be acceptable if they provide a basis for the findings requisite to                                             6. Products the imuance or ontinuance of a permit or license by the Commissio


Detectors are arranged so that a detection area is defined by a plane perpendicular to the line of passage of individuals through the doorway monitor. Various arrangements of the detectors are possible.
====n.     ====


However, specific placement of detectors should be based on the need to eliminate areas of no detection.
===1. Power Reactors===
                                                                                      2.  Reaseerd  enidTest Reactors           


Commercially available doorway monitors are equipped with an automatic radiation background updating system that periodically monitors and averages the background count rate. A doorway monitor equipped with an automatic radiation background updating system is also provided with a treadle pad or beam break system to indicate that the zone of detection is occupied. When the zone of detection is occupied, the radiation level detected by the doorway monitor is compared to the mean background. If the level is greater than the mean background by a predetermined trigger level, an alarm is actuated.
===7. Transportation===
                                                                                      3.  Fuels and Materials Facilities        8. Occupational Health Published guidas will be revised periodically, asappropriate, to accommodate        4. Environmental and Siting              9. Antitrust Review comments amd to refloct new informeaion or experience.                               5. Materials and Plant Protection        1


Alarm actuation point is usually determined by comparing the radiation levels within the zone of detection while occupied to the sum of the mean background while unoccupied and a factor to account for predetermined statistical accuracy.1 Thus, the condition for an alarm can be written as:
===0. General===
                              G>B+n(B) 1/2 Where B is the mean background, G is the radiation level within the zone of detection while occupied and n is a multiplier, usually between 4 and 10.2 Although the automatic background updating system allows unattended use of the doorway monitor, for technical reasons, the system may be less effective in certain situations. Techniques to prevent this are provided in the regulatory position.


Whether or not a doorway monitor is equipped with an automatic background updating system, high background activity will decrease sensitivity. Measuring activity in the zone of detection for longer
Thus the condition for an alarm can be written as                      Areas, and Material Access Areas,") in such a manner that objects cannot be passed over, around, or under the G > B + n,                                              detection area.
1      The square root of the mean of a Poisson-distributed quantity is the unbiased estimate of the standard deviation of that quantity.


2       Note that, in general, for a count rate system, the condition for alarm should be modified to account for the response time of the instrument as follows:
. (2) The detector elements should be designed and where B is the mean background, G is the radiation level                   positioned so that detection sensitivity is as uniform as with the sensitive area occupied, and n is a multiplier,                   possible over the detection area; in no case should any usually an integer between 4 and 10.* The value of n                        areas where SNM is not detectible be permitted.
                   G>B+n(B)1/2 (1-e-t/r)
        Where t is the counting time and r is the time constant of the instrument. If, as should be the case, t/r>5, the added factor is essentially unity.


RG 5.27, Rev. 1, Page 3
directly affects the false alarm rate, and the combination                        (3) Power, sensitivity, and other controls of the of B and n affect the sensitivity.                                         doorway monitor should be tamper-safed when unat tended.


periods of time will compensate somewhat for a high radiation background. However, longer measurement periods can make the use of the doorway monitor less convenient. Because of the adequate radiation detection sensitivity and high-throughput capability associated with processing many personnel through the detection system on a daily basis, walk-through pedestrian monitors are the primary SNM
Although the automatic background updating system                            (4) Signal lines connecting alarm relays to the allows unattended use of the doorway monitor, for                          alarm monitor should be supervised.
detection system used in personnel portals at MAAs.


Hand-Held Monitors Hand-held monitors can use detectors made of NaI(Tl), plastic scintillators, semiconductors, or He-3 gas-filled tubes. Commercially available systems have rechargeable batteries that assist in ensuring continuous availability. Training the operator of a hand-held monitor is essential. The operator must scan an individual in the correct way for a hand-held monitor to be fully effective. In addition, the operator must understand the capabilities of the equipment, when the equipment is working within acceptable parameters and when it is not.
technical reasons, the system may be less effective in                            (5) Some doorway monitors may require an indi certain situations. Techniques to prevent this are des                      vidual to occupy the detection area for a specified time, cribed in the Regulatory Position.                                          longer than a normal walking pace would provide. If this is the case, the doorway monitor should be provided Doorway monitors not equipped with an automatic                        with a treadle pad and a "clock" device to assure that background updating system either must rely on the                          the detection area is occupied for the requisite time. An inherent sensitivity of the instrument and low back                        aural and visual indication should be given if an ground variation to ensure that concealed SNM will be                      individual being searched does not occupy the area detected or must be attended so that a measurement of                      sufficiently long.


Radioisotope identification systems that detect radiation with high purity germanium (HPGe)
background can be taken immediately prior to use and                            b. System Specification the alarm level set to maintain the desired sensitivity to                        (1) Plutonium-239. A doorway monitor used to concealed SNM. As with the doorway monitor equipped                        detect plutonium should be capable of detecting a with an automatic background updating system, a                             minimum of 0.5 gram of plutonium-239 encased in a doorway monitor not so equipped compares the activity                      minimum of 3 mm of brass at a 90% confidence limit.
detectors can be hand-held. These monitors are commercially available and may have a special cooling device, instead of a cryogenic bath, to cool the semiconductor HPGe crystal. Special cooling devices (e.g., Stirling cooler) allow a light-weight design useful as a hand held detection system.


Hand-held monitors complement SNM search operations by enabling a more thorough search of an individual to locate the radiation source after a doorway monitor has alarmed, enabling pedestrian searches to continue when a doorway monitor is inoperative and, if technically outfitted to do so, identify specific radionuclide(s) causing a doorway alarm.
with the detection area occupied with some set value,                      The false alarm rate should be less than 0.1% (Appendix usually the measurement of background taken just prior                      C).
to use. In any case, the expression above can be used as a                         (2) Uranium-233. A doorway monitor used to condition of alarm by replacing B + nr'Wwith the set                        detect uranium-233 should be capable of detecting level.                                                                      within 4 hours of purification* a minimum of 1 gram of uranium-233 containing between 7 and 10 ppm of Whether or not a doorway monitor is equipped with                      uranium-232 encased in a minimum of 3 mm of brass at an automatic background updating system, high back                          a 90% confidence limit. The false alarm rate should be ground activity will decrease sensitivity. Measuring activ                  less than 0.1% (Appendix C).
ity for longer periods will somewhat compensate for                                (3) Uranium-235. A doorway monitor used to high background; however, longer measurement periods                        detect uranium-235 should be capable of detecting a will make use of the doorway monitor less convenient.                       minimum of 3 grams of uranium-235 contained in uranium enriched to 20% or more in the uranium-235


Because of the time required to scan an individual with a hand-held monitor, it is used as a secondary SNM detection system at an MAA personnel portal.
==C. REGULATORY POSITION==
 
isotope encased in a minimum of 3 mm of brass at a 50%
Vehicle Monitors Two types of automatic vehicle monitors presently in use are the vehicle monitoring station and the drive-through vehicle monitor. Commercially available vehicle drive-through SNM portals generally consist of two vertical cabinets containing both large plastic scintillators and decision -making electronics. These scintillators continuously measure the gamma ray background intensity and adjust the alarm threshold to maintain a constant nuisance alarm rate. The sensitivity of SNM vehicle monitors vary for different types of vehicles and depends on the size, spacing, and number of detectors. For an individual detector configuration and vehicle, two of the dominate sensitivity factors are the occupancy background suppression and shielding provided by the components of the vehicle.3 Standards Associated with Monitoring Selection of equipment, setup, operation calibration, testing and performance evaluation of portal monitoring systems should be performed using procedures designed for the specific facility and configuration. Guidance that pertains to the use of radiation detection and metal detection instrumentation is available from several standards organizations. The NRC staff finds that the following guidance, which has been successfully used by SNM licensees and is available from the American Society for Testing and Materials (ASTM), Conshohocken, Pennsylvania, acceptable for use:
                                                                            confidence limit. The false alarm rate should be less than
3        LA-UR-96-4505: An Optimized International Vehicle Monitor, (Ref. 8)
1. Minimum Qualifications for SNM Doorway Monitors                         0.1% (Appendix C).
                                            RG 5.27, Rev. 1, Page 4
 
*        ASTM C1189-11, Standard Guide to Procedures for Calibrating Automatic Pedestrian SNM Monitors. (Ref. 9)
        *        ASTM C1112-99 (2005), Standard Guide for Application of Radiation Monitors to the Control and Physical Security of Special Nuclear Material. (Ref. 10)
        *        ASTM C1237-99 (2005), Standard Guide to In-Plant Performance Evaluation of Hand- Held SNM Monitors. (Ref. 11)
        *        ASTM C993-97 (2012), Standard Guide for In-Plant Performance Evaluation of Automatic Pedestrian SNM Monitors. (Ref. 12)
        *        ASTM C1270-97 (2012), Standard Practice for Detection Sensitivity Mapping of In- Plant Walk Through Metal Detectors. (Ref. 13)
        *        ASTM C1269-97 (2012), Standard Practice for Adjusting the Operational Sensitivity Setting of In-Plant Walk-Through Metal Detectors. (Ref. 14)
        *        ASTM C1309-97 (2012), Standard Practice for Performance Evaluation of In-Plant Walk-Through Metal Detectors. (Ref. 15)
        In addition, ASTM C1236-99 (2005), Standard Guide for In-Plant Performance Evaluation of Automatic Vehicle SNM Monitors (Ref. 16) was withdrawn in 2014, but can be used by licensees as a development tool.
 
Harmonization with International Standards The International Atomic Energy Agency (IAEA) has established a series of safety guides and standards constituting a high level of safety for protecting people and the environment. IAEA safety guides present international good practices and increasingly reflects best practices to help users striving to achieve high levels of safety. Pertinent to this RG, IAEA Nuclear Security Series No. 13, Nuclear Security Recommendations on Physical Protection of Nuclear Material and Nuclear Facilities, issued January 2011, (Ref. 17) et. al., addresses considerations necessary for a nuclear material security program.
 
While the NRC has an interest in facilitating the harmonization of standards used domestically and internationally, the NRC does not specifically endorse the IAEA document, and is only acknowledging that it may be useful as a reference for general information.
 
RG 5.27, Rev. 1, Page 5
 
Documents Discussed in Staff Regulatory Guidance This RG endorses the use of one or more codes or standards developed by external organizations, and other third party guidance documents. These codes, standards and third party guidance documents may contain references to other codes, standards or third party guidance documents (secondary references). If a secondary reference has itself been incorporated by reference into NRC regulations as a requirement, then licensees and applicants must comply with that standard as set forth in the regulation. If the secondary reference has been endorsed in a RG as an acceptable approach for meeting an NRC requirement, then the standard constitutes a method acceptable to the NRC staff for meeting that regulatory requirement as described in the specific RG. If the secondary reference has neither been incorporated by reference into NRC regulations nor endorsed in a RG, then the secondary reference is neither a legally-binding requirement nor a generic NRC approval as an acceptable approach for meeting an NRC requirement. However, licensees and applicants may consider and use the information in the secondary reference, if appropriately justified and consistent with current regulatory practice, consistent with applicable NRC requirements such as 10 CFR 50.59.
 
C. STAFF REGULATORY GUIDANCE
1.      Considerations for SNM Doorway Monitors


====a. General====
====a. General====
        (1)     Metal detectors should be used in conjunction with an SNM doorway monitor as an SNM
        (1) SNM Doorway monitors should be used in                           2. Use of Doorway Monitors conjunction with a metal detector and should be                               In general, doorway monitors should be used in installed in a passageway (see Regulatory Guide 5.7,                         locations of minimum background and minimum back
                detection system and can be one of the two required separate searches for concealed SNM (10 CFR 73.46(d)(9)). The metal detector unit should be installed in the pedestrian passageway as described in RG 5.7, Entry/Exit Control of Personnel Access to Protected Areas, Vital Areas, and Material Access Areas with the SNM monitor in such a way that objects cannot be passed over, around, or under the detection area without being appropriately searched. The entire process begins when the individual, package, or other item approaches the monitoring area and ends when the individual, package or other item is exiting the monitoring area after the completion of a monitoring event.
"Control of Personnel Access to Protected Areas, Vital                      ground fluctation. If circumstances dictate use of a doorway monitor in an area of high background,
 
*Note that, in general, for a count rate system, the condition for          sufficient shielding should be provided to maintain afarm should be modified to account for the response time of               necessary sensitivity.
(2)    Alarm actuation for detectable metal mass should be the amount necessary to shield SNM
                that would allow a protracted theft of a formula quantity of strategic SNM to occur before the inventory process identifies it as missing.
 
(3)    The detector elements should be designed and positioned so that detection sensitivity is as uniform as possible over the zone of detection; in no case should any area within the zone of detection not be able to detect SNM.
 
(4)    Power, sensitivity, and other controls of the doorway monitor and metal detector should be tamper-safe when unattended. Doorway monitors and metal detectors that are secured behind locked and alarmed doors when unattended is an acceptable alternative measure to implementing tamper- safe devices on the SNM monitoring system.
 
(5)    Metal and SNM detection equipment should be provided with uninterruptible power sources and/or emergency generator power.
 
(6)    Signal lines connecting alarm relays to the alarm monitors for both metal and SNM
                detectors should be supervised electronically or by direct surveillance to detect tampering.
 
RG 5.27, Rev. 1, Page 6
 
(7) Some doorway monitors may require an individual to occupy the detection area for a specified time (e.g., longer than what a normal walking pace would provide). In this case, the doorway monitor should be provided with a treadle pad and a timer to ensure that the zone of detection is occupied for the requisite time. Audible and visual alarms should actuate if the individual being searched does not occupy the detection area for the entire count period.
 
(8) The doorway monitor should be equipped with a high-background radiation alarm, which will announce if the measurement of the radiation background exceeds the appropriate maximum permissible background. The doorway monitor should not be used during periods of high background radiation. Calibration and determination of allowable background thresholds should be done in accordance with ASTM C1189-11, (Ref. 9)
(9) System specifications guidance for specific radioisotopes are identified below. See ASTM C1112-99(2005), (Ref. 10) for supporting information.
 
(a)      Plutonium-239. A doorway monitor used to detect plutonium (Pu) should be capable of detecting 0.5grams of plutonium with an isotopic content of at least
            93 percent Pu-239 and less than 6.5 percent Pu-240. The Pu should contain less than 0.5 percent impurities. The form of the material should be a metallic sphere or cube. The impact of Am-241, a Pu decay product that will build up over time and emit increasing amounts of 60-keV gamma radiation, must be minimized by including a cadmium filter 0.04 cm to 0.08 cm thick as part of the source encapsulation. Protective encapsulation should be in as many layers as local rules require of a material such as aluminum (0.32 cm thickness) or thin (0.16 cm thickness) stainless steel or nickel that minimize unnecessary radiation absorption. The source should be encased in a minimum of 3 mm brass and detected at a 50 percent probability of detection with a 95 percent confidence limit. The false alarm rate should be less than 0.1 percent.
 
(b)      Uranium-235. A doorway monitor used to detect uranium-235 (U-235) should be capable of detecting highly enriched (i.e., 20 percent or more) uranium containing at least 93 percent U-235 and less than 0.25 percent impurities. The form of the material should be a metallic sphere or cube. Encapsulation should be applied in such manner that it minimizes unnecessary radiation absorption in the encapsulation. The source should be encased in a minimum of 3 mm brass and detected at a 50 percent probability of detection with a 95 percent confidence limit. The false alarm rate should be less than 0.1 percent.
 
(c)      Uranium-233. Adequate sensitivity for uranium-233 (U-233) may be demonstrated by meeting the detection requirements for U-235.
 
RG 5.27, Rev. 1, Page 7
 
2. Operations with Doorway and Hand-Held Monitors In general, doorway monitors are the primary method used to search for concealed SNM,
  hand-held monitors are secondary, and a physical search is tertiary. Doorway monitors should be used in locations with minimum background radiation and minimum background radiation fluctuation. If circumstances dictate the use of a doorway monitor in an area of high background radiation, sufficient shielding should be provided to maintain necessary sensitivity.
 
a. The procedures, or changes to procedures developed to implement requirements of 10 CFR 73.46 should be prepared sufficiently in advance of intended implementation to provide verification of satisfactory performance.
 
b. The plan for metal detection equipment functionality and performance testing periodicity, procedures, and test sources should be submitted to the NRC for approval within 360 days for licensed operating facilities, 180 days before revising existing licensee SNM search programs, and 180 days before initial start of operations for newly licensed facilities.
 
c. During use, the doorway monitor system should check the radiation background and adjust the measurement offset at least every 15 minutes.
 
d. Doorway monitors shall be attended by two armed guards at an MAA (10 CFR 73.46 (d)(9))
  within a facility containing a formula quantity of strategic SNM. The two armed guards may consist of a guard manning the SNM monitoring system and the other providing oversight of the SNM monitoring system activities by residing in an adjacent protective enclosure. Doorway monitors should be attended at non-power reactors.
 
e. Each individual to be checked should, in turn, enter the doorway monitor detection area and be required to remain still long enough for the device to operate properly.
 
f. With the individual in the doorway monitor detection area, an alarm should audibly and visually announce in the vicinity of the monitor if the activity in the detection area exceeds the set alarm threshold for radiation, possibly indicating the presence of SNM.
 
g. When a doorway monitor signals an alarm, the individual generating the alarm should pass through the monitor a second time to confirm the signal. If the second pass through the SNM
  monitor does not result in a detection, then a third pass through the monitor should be conducted to verify no detection. If the second pass through the monitor also generates an alarm, the individual should be retained and subjected to a body search, typically with a hand-held monitor, as described in ASTM C1237-99 (2005), (Ref. 11) to locate and identify the source of the signal.
 
If the hand-held monitor does not confirm the alarm signals generated by the doorway monitor, the hand-held monitor should be tested against a known source to confirm it is working properly.
 
If it responds to the source in the anticipated manner, it should be concluded that the doorway monitor should be tested, repaired if necessary, and retested before returning to service. The individual generating the alarm should be released after confirmation that no SNM was detected.
 
If detection is suspected to be from SNM contamination, health physics personnel should verify this finding. A monitoring flow diagram is provided in Figure 1.
 
h. A hand-held SNM monitor should be used when the doorway monitor is not functioning as intended. Search personnel should be trained on the correct use of the hand-held monitoring. A
  hand-held monitor should have the capability to identify specific radioisotopes.
 
RG 5.27, Rev. 1, Page 8
 
3. Physical Searches and Training a. A physical search for concealed SNM should be conducted as necessary.
 
b. To enhance the probability of detection, random searches for concealed SNM at the protected area boundary may be conducted, including searches of hand-carried items.
 
c. At facilities with formula quantities of strategic SNM, personnel having search duties and responsibilities must be trained and qualified.(10 CFR 73.45(g)(1)(i)).
                                            Pedestrian in Monitoring Zone Sets Off Alarm at First and Second Pass Hand-Held Detector Search for Source Release No            Nuclide?
            Pedestrian Document False Yes Alarm for Later Investigation Release SNM?          No Pedestrian Yes                    Document Type of Nuclide Detected Tactical Response by Security Figure 1 Flow diagram for SNM searches RG 5.27, Rev. 1, Page 9
 
4. Calibration, Testing, Maintenance, and Operating Instructions a. Calibration Doorway and hand-held monitors should be calibrated with a source of the amount, configuration, and variety of SNM to be detected. Doorway and hand-held monitor calibration should be conducted in accordance with Reference 7 or as recommended by the manufacturer.


Calibration should be conducted before initial use and after monitor repair or maintenance.
the instrument as follows:
                                                                                a. Attended Doorway Monitor G > B + n1]0l - e-t/7)                                        (1) If the doorway monitor is attended during where t is the counting time and r is the time constant of the            use, it need not be equipped with an automatic instrument. If, as should be the case, t/,r > 5 the added factor is essentially unity.                                                        *Purification means removal of all decay products.


Calibration should be conducted at least every three months. As a quality assurance measure, consideration should be given to having SNM calibration standards traceable to certified reference standards or materials.
5.27-2


====b. Testing====
(d) Activate the electronics and alarm logic background updating system, although such capability is                when an individual is within the detection area and preferred.                                                            initiate operation of the doorway monitor.
  (1)     Doorway, Hand-Held and Vehicle SNM Monitors Methods of performance testing doorway and hand-held monitors are found within ASTM C993-97(2012), (Ref. 12) and Reference 9 (as well as reference 13). These references may be used to develop instructions for testing SNM monitors to assure system specifications are met. Daily testing should be a simple functional test (i.e.


operational test) to assure the detector is working. Daily testing should be performed during each shift, or once per day if there is only one shift. Reference 9 describes an acceptable approach for daily testing. As described in reference 9 and reference 11, testing sources may be different than those used during calibration.
(2) Prior to each use* of a doorway monitor not                        (3) An alarm should sound in the central alarm equipped with an automatic background updating                        station if, when occupied, the activity in the detection system, a measurement of background should be taken,                   area exceeds the internally set threshold level (the mean and the alarm threshold should be set to the proper                    background plus some multiple times the square root of value listed in Table I for the measured background and                the mean background), as such a situation would the proper n value as determined in Appendix B. Each                  indicate the presence of SNM upon the individual being individual to be checked should, in turn, enter the                    checked.


(2)    Metal Detectors Sensitivity mapping and operational sensitivity testing methods are described within ASTM C1270-97 (2012), (Ref. 13), ASTM C1269-97 (2012), (Ref 14) and ASTM
detection area and be required to remain sufficiently                        (4) The doorway monitor should be equipped long for the device to operate properly. During use, the              with a high-background alarm which will sound if the background should be checked and the alarm threshold                  average background at the location of the doorway reset at least each 15 minutes.                                      monitor exceeds the appropriate maximum permissible
          C1309-97 (2012), (Ref 15). The references may be used to develop instructions for performance testing the metal detection system used to search for concealed, shielded strategic SNM. The metal detection system should be capable of detecting the minimum metal shielding concealed anywhere on an individual three times out of three trials.
        (3) With the individual being checked in the                  background level listed in Table II as determined in detection area, an alarm should sound if the activity in              Appendix C. The doorway monitor should not be used the detection area exceeds the alarm threshold T, as such              during such periods of high background. Other moni a situation would indicate the presence of SNM.                       tored exits should be used.


Performance testing should be conducted at least once every three months. The performance testing should include passing the minimum metal test source through a honeycomb configuration test apparatus that covers the entire detection area as described in references 13, 14 and 15. The honeycomb channels should be a maximum of 6 inches by 6 inches in dimension. The test source should be passed through the detection area as close as possible to the same rate (speed) as a pedestrian walking through the metal detector unit. Attaching the metal test source to a wooden dowel rod to conduct this test can facilitate the effective rate of passage of the metal source through the honeycomb test apparatus. A detection of the metal test source in each of the honeycomb test channels constitutes an acceptable performance test. Daily operability testing should be conducted once per shift, or at least daily.
(4) The doorway monitor should be equipped with a high-background alarm which will sound if the                  3. Testing and Calibration measurement of background exceeds the appropriate                          a. Testing maximum permissible background level listed in Table II                        Doorway monitors should be tested by passing an as determined in Appendix C. The doorway monitor appropriate source of the amount and isotope specified should not be used during such periods of high back                    in Regulatory Position C.l.b. through the doorway ground.                                                              monitor no less frequently than once per day.* In b. Unattended Doorway Monitor addition, a functional performance test should be carried
          (1) If the doorway monitor is unattended, an                  out at least once per week. An acceptable functional automatic background update system should be incor                    performance test procedure is discussed in Appendix A
  porated into the doorway monitor electronics and alarm                of this guide logic. The control circuitry, if possible, should be located              b. Calibration at the central alarm station (or other monitoring point).                    Doorway monitors should be calibrated with a
          (2) Door interlocks and closed-circuit TV in                  source of the amount, configuration, and variety of SNM
  combination with beam breaks, motion detectors, and/                  to be detected (e.g., 0.5 gram Pu in 3 mm of brass).
  or treadle pads, should be employed to:                                Calibration should be carried out according to a proce (a) Indicate to the person manning the central              dure such as that in Appendix B.


c. Maintenance Metal detection and SNM monitoring equipment shall be maintained to be operable and effective as intended (10 CFR 73.20(4), 10 CFR 73.46(g), and 10 CFR 73.60(d)(1)).
alarm station that an individual has entered the secure                    c. Operating Instructions access passageway and/or is approaching the doorway                          Operating instructions should be posted near the monitor,                                                              doorway monitor,* if attended, or at the monitoring (b) Allow observation of the individual ap                  point if the doorway monitor is unattended. The proaching the doorway monitor,                                       instructions should clearly indicate the procedure for use (c) Preclude a slow approach to the sensitive              of the doorway monitor and the procedure for setting area of the doorway monitor, and                                     thresholds, if appropriate. In addition, the operating instructions should indicate what corrective action is to
                                    RG 5.27, Rev. 1, Page 10
  *By use is meant an individual or several individuals, each, in be taken and who is to be notified in the event of a turn, being checked for SNM by the doorway monitor. The              malfunction.


d.      Operating Instructions Operating instructions should be available near the search activity. The procedural elements listed below should be included in the procedures for the search activity. A management system shall provide for the development, revision, implementation, and enforcement of security procedures (10 CFR 73.46 (b)(3)). Written procedures detailing the duties of search personnel for operation of SNM monitors and metal detection equipment shall be developed
maximum period between threshold sets while the doorway monitor is in use is determined by the stability of local            *Doorway monitors used to search for concealed U-233 should background and may necessarily be more frequent than every            be tested according to §6 of Appendix A.
        (10 CFR 73.46 (b)(3)(i)). Procedures should address the following:
              *    metal detection threshold criteria,
              *    test sources and their use,
              *    monitor background reduction and sensitivity,
              *    searching pedestrians with doorway and hand-held monitors,
              *    recording, retention, and analysis of monitor performance data,
              *    recording and resolution of alarm events,
              *    quarterly performance testing,
              *    daily operational testing,
              *    environmental operating constraints (e.g., temperature and humidity),
              *    search operations during an emergency or loss of power,
              *    maintenance of monitors and metal detection equipment,
              *    security for the system equipment, communications, software, and data,
              *    training for operating personnel, and
              *    documentation requirements for authorized removals of SNM.


==D. IMPLEMENTATION==
15 minutes.
The purpose of this section is to provide information on how applicants and licensees4 may use this guide and information regarding the NRCs plans for using this RG. In addition, it describes how the NRC staff complies with the Backfit Rule found in 10 CFR 50.109(a)(1), 10 CFR 70.76(a)(1), and
10 CFR 76.76(a)(1) or any applicable finality provisions in 10 CFR Part 52.


Use by Applicants and Licensees Applicants and licensees may voluntarily5 use the guidance in this document to demonstrate compliance with the underlying NRC regulations. Methods or solutions that differ from those described in this RG may be deemed acceptable if they provide sufficient basis and information for the NRC staff to verify that the proposed alternative demonstrates compliance with the appropriate NRC regulations.
5.27-3


Current licensees may continue to use guidance the NRC found acceptable for complying with the identified regulations as long as their current licensing basis remains unchanged. The acceptable guidance may be a previous version of this RG.
TABLE I
                  ALARM THRESHOLD
                      T
  B n=    4    5          6      7    8    9    10
100      140  150      160      170  180  190  200
120      164  175      186      197  208  219  230
140      .187  199      211      223  235  246  258
160      211  223        236      249  261  274  286
180      234  247        260      274  287  301  314
200      257  271        285      299  313  327  341
220      279  294        309      324  339  353  368
240      302  317        333      348  364  379  395
260      324  341        357      373  389  405  421
280      347  364        380      397  414  431  447
300      369  387        404      421  439  456  473
320      392  409        427      445  463  481  499
340      414  432        451      469  488  506  524
360      436  455        474      493  512  531  550
380      458  477        497      516  536  555  575
400      480  500        520      540  560  580  600
420      502  522        543      563  584  604  625
440      524  545        566      587  608  629  650
460      546  567        589      610  632  653  674
480      568  590        611      633  655  677  699
500      589  612        634      657  679  701  724
520      611  634        657      680  702  725  748
540      633  656        679      703  726  749  772
560      655  678        702      726  749  773  797
580      676  700        724      749  773  797  821
600      698  722        747      771  796  820  845
620      720  744        769      794  819  844  869
640      741  766        792      817  842  868  893
660      763  788        814      840  866  891  917
680      784  810        836      863  889  915  941
700      806  832        859      885  912  938  965
720      827  854        881      908  935  961  988
740      849  876        903      930  958  985 1012
760      870  898        925      953  981  1008 1036
780      892  920        948      975  1003  1031 1059
800      913  941        970      998  1026  1055 1083
820      935  963        992    1020  1049  1078 1106
840      956  985      1014    1043  1072  1101 1130
860      977  1007      1036    1065  1095  1124 1153
880      999  1028      1058    1088  1117  1147 1177
900    1020  1050      1080    1110  1140  1170 1200
920    1041  1072      1102    1132  1163  1193 1223
940    1063  1093      1124    1155  1185  1216 1247
960    1084  1115      1146    1177  1208  1239 1270
980    1105  1137      1168    1199  1230  1262 1293
                          5.27-4


Licensees may use the information in this RG for actions which do not require NRC review and approval. However, voluntarily using the subject matter in the guidance may change the facilities
TABLE I (Cont'd)
4        In this section, licensees refers to holders of, and the term applicants refers to applicants for, the following: (1)
                      ALARM THRESHOLD
        special nuclear material licenses under 10 CFR Part 70; (2) operating licenses under 10 CFR Part 50; (3) combined licenses under 10 CFR Part 52; and (4) certificates of compliance or approvals of a compliance plan for gaseous diffusion plants under 10 CFR Part 76.
                      T
  B  n =    4     5       6          7    8      9
1000      1126  1158    1190      1221  1253  1285  1316
1200      1339  1373    1408      1442  1477  1512  1546
1400      1550  1587    1624      1662  1699  1737  1774
1600      1760  1800    1840      1880  1920  1960  2000
1800      1970  2012    2055      2097  2139  2182  2224
2000      2179  2224    2268      2313  2358  2402  2447
2200      2388  2435    2481      2528  2575  2622  2669
2400      2596  2645    2694      2743  2792  2841  289C
2600      2804  2855    2906      2957  3008  3059  3110
2800      3012  3065    3117      3170  3223  3276  3329
3000      3219  3274    3329      3383  3438  3493  3548
3200      3426  3483    3539      3596  3653  3709  3766
3400      3633  3692    3750      3808  3866  3925  3983
3600      3840  3900    3960      4020  4080  4140  4200
3800      4047  4108    4170      4232  4293  4355  4416
4000      4253  4316    4379      4443  4506  4569  4632
4200      4459  4524    4589      4654  4718  4783  4848
4400      4665  4732    4798      4864  4931  4997  5063
4600      4871  4939    5007      5075  5143  5210  5278
4800      5077  5146    5216      5285  5354  5424  5493
5000      5283  5354    5424      5495  5566  5636  5707
5200      5483  5561    5633      5705  5777  5849  5921
5400      5694  5767    5841      5914  5988  6061  6135
5600      5899  5974    6049      6124  6199  6273  6348
5800      6105  6181    6257      6333  6409  6485  6562
6000      6310  6387    6465      6542  6620  6697  6775
6200      6515  6594    6672      6751  6830  6909  6987
6400      6720  6800    6880      6960  7040  7120  7200
6600      6925  7006    7087      7169  7250  7331  7412
6800      7130  7212    7295      7377  7460  7542  7625
7000      7335  7418    7502      7586  7669  7753  7837
7200      7539  7624    7709      7794  7879  7964  8049
7400      7744  7830    7916      8002  8088  8174  8260
7600      7949  8036    8123      8210  8297  8385  8472
7800      8153  8242    8330      8418  8507  8595  8683
8000      8358  8447    8537      8626  8716  8805  8894
8200      8562  8653    8743      8834  8924  9015  9106
8400      8767  8858    8950      9042  9133  9225  9317
8600      8971  9064    9156      9249  9342  9435  9527
8800      9175  9269    9363      9457  9550  9644  9738
9000      9379  9474    9569      9664  9759  9854  9949
9200      9584  9680      9775      9871  9967 10063 10159
9400      9788  9885      9932    10079 10176  10273 10370
9600      9992 10090    10188      10286 10384  10482 10580
9800    10196 10295    10394      10493 10592  10691 10790
                            5.27-5


5        In this section, voluntary and voluntarily means that the licensee is seeking the action of its own accord, without the force of a legally binding requirement or an NRC representation of further licensing or enforcement action.
TABLE II
      MAXIMUM PERMISSIBL


RG 5.27, Rev. 1, Page 11
==E. BACKGROUND==
a = 0,  Pa = 50%
                              B
    G  n=      4        5          6        7        8            10
                                                                  9
100          67      61          55        50      46        42  38
120          83      76          70        64      59      54    50
140          100      92          85        78      72        67  62
160        117      108        100        93      86        80  74
180.          134      124        116      107      100        93    87
200          151      141        131      123      114      107  100
220          168      157        147      138      129      121  113
240          186      174        163      153      144      135  127
260          203      191        180      169      159      150  141
280          221      208        196      185      174      165  155
300          238      225        213      201      190      179  170
320          256      242        229      217      205      194  184
340          274      259        246      233      221      210  199
360          292      277        263      249      237      225  214
380          310      294        280      266      253      240  229
400          328      312        297      282      269      256  244
420          346      329        314      299      285      272  259
440          364      347        331      316      301      287  274
460          382      365        348      332      317      303  290
480          400      382        365      349      334      319  305
500          418      400        383      366      350      335  321
520          436      418        400      383      367      351  337
540          455      436        417      400      383      367  352
560          473      454        435      417      400      384  368
580          491      471        452      434      417      400  384
600          510      489        470      451      433      416  400
620          528      507        488      468      450      433  416
640          546      525        505      486      467      449  432
660          565      543        523      503      484      466  448
680          583      562        541      520      501      482  464
700          602      580        558      538      518      499  481
720          620      598        576      555      535      516  497
740          639      616        594      573      552      532  513
760          657      634        612      590      569      549  530
780          676      652        629      607      586      566  546
800          695      671        647      625      603      583  563
820          713      689        665      643      621      600  579
840          732      707        683      660      638      617  596
860          750      725        701      678      655      633  613
880          769      744        719      695      673      650  629
900          788      762        737      713      690      667  646
920          806      780        755      731      707      685  663
940          825      799        773      748      725      702  679
960          844      817        791      766      742      719  696
980          863      835        809      784      760      736  713
                                    5.27-6


security plan such that NRC review may be required under the provisions of 10 CFR Part 50.54,
TABLE II  (Cont'd)
10 CFR Part 70.32 or 10 CFR Part 76.68, and should be evaluated prior to incorporating the methods into the security plans. Licensees may use the information in this RG or applicable parts to resolve regulatory or inspection issues.
    MAXIMUM PERMISSIBL


Use by NRC Staff The NRC staff does not intend or approve any imposition or backfitting of the guidance in this RG. The NRC staff does not expect any existing licensee to use or commit to using the guidance in this RG, unless the licensee makes a change to its licensing basis. The NRC staff does not expect or plan to request licensees to voluntarily adopt this RG to resolve a generic regulatory issue. The NRC staff does not expect or plan to initiate NRC regulatory action which would require the use of this RG. Examples of such unplanned NRC regulatory actions include issuance of an order requiring the use of the RG, generic communication, or promulgation of a rule requiring the use of this RG without further backfit consideration.
==E. BACKGROUND==
a -'0,   Pa = 50Z
                              B
  G    n =    4        5        6        7      8          9  10
1000          881      854      827      802      777      753  730
1200        1069      1039      1009      981      953      926  900
1400        1258      1225      1193    1161    1131      1101  1073
1600        1448      1412      1377    1343    1310      1278  1247
1000        1638      1600      1563    1527    1491      1457  1423
2000        1829      1789      1749    1710    1673      1636  1600
2200        2020      1978      1936    1895    1855      1816  1778
2400        2212      2167      2124    2081    2039      199D  1958
2600        2404      2357      2312    2267    2223      2180  2138
2800        2596      2548      2500    2453    2407      2363  2318
3000        2789      2738      2689    2640    2593      2546  2500
3200        29S2      2929      2878    2828    2778      2730  2682
3400        3175      3121      3068    3016    2964      2914  2865
3600        3368    3312      3258    3204    3151      3099  3048
3800        3561    3504      3448    3392    3338      3284  3232
4000        3755      3696      3638    3581    3525      3470  3416
4200        3949      3888      3829    3770    3713      3656  3600
4400        4143      4081      4020    3960    3900      3842  3785
4600        4337      4273      4211    4149    4088      4029  3970
4800        4531      4466      4402    4339    4277      4216  4155
5000        4725      4659      4593    4529    4465      4403  4341
5200        4919      4852      4785    4719    4654      4590  4527
5400        5114      5045      4977    4910    4843      4778  4713
5600        5309      5238      5169    5100    5032      4966  4900
5800        5503      5432      5361    5291    5222      5154  5087
6000        5698      5625'    5553    5482    5411      5342  5274
6200        5893      5819      5745    5673    5601      5531  5461
6400        6088      6012      5938    5864    5791      5719  5648
6600        6283      6206      6130    6055    5981      5908  5836
6800        6478      6400      6323    6247    6172      60'97 6024
7000        6673      6594      6516    6438    6362      6286  6212
7200        6868      6788      6709    6630    6552      6476  6400
7400        7064      6982      6902    6822    6743      6665  6588
7600        7259      7176      7095    7014    6934      6855  6777
7800        7455      7371      7288    7206    7125      7045  6965
8000        7650      7565      7481    7398    7316      7234  7154
8200        7846      7760      7674    7590    7507      7425  7343
8400        8041      7954      7868    7782    7698      7615  7532
8600        8237      8149      8061    7975    7889    7805  7721
8800        8433      8343      8255    8167    8081      7995  7911
9000        8628      8538      8449    8360    8272      8186  8100
9200        8824      8733      8642    8553    8464      8376  8290
9400        9020      8928      8836    8745    8656      8567  8479
9600        9216      9122      9030    8938    8348      8758  8669
9800        9412      9317      9224    9131    9039      8949  8859
                                  5.27-7


During regulatory discussions on plant specific operational issues, the staff may discuss with licensees various actions consistent with staff positions in this RG, as one acceptable means of meeting the underlying NRC regulatory requirement. Such discussions would not ordinarily be considered backfitting even if prior versions of this RG are part of the licensing basis of the facility. However, unless this RG is part of the licensing basis for a facility, the staff may not represent to the licensee that the licensees failure to comply with the positions in this RG constitutes a violation.
TABLE II  (Cont'd)
    MAXIMUM PERMISSIBL


If an existing licensee voluntarily seeks a license amendment or change and (1) the NRC staffs consideration of the request involves a regulatory issue directly relevant to this revised RG and (2) the specific subject matter of this RG is an essential consideration in the staffs determination of the acceptability of the licensees request, then the staff may request that the licensee either follow the guidance in this RG or provide an equivalent alternative process that demonstrates compliance with the underlying NRC regulatory requirements. This is not considered backfitting as defined in
==E. BACKGROUND==
10 CFR 50.109(a)(1), 10 CFR 70.76(a)(1), or 10 CFR 76.76(a)(1) or any applicable finality provisions in
S= 1.3, Pa = 90%
10 CFR Part 52.
                            B
  G    n      4        5        6        7        8        9  10
100          57        51        46        42      38      34  31
120          72        65        59        54      49      45  41
140          87        80        73        67      62      57  52
160          103        95        87        81      75      69  64
180        119      110      102        95      88      81  76
200        135      126      117      109      101      94  FS
220          151      141      132      123      115    107  100
240          168      157      147      138      129    121  113
260          185      173      163      153      143      135 127
280          201      189      178      168      158    149  1L0
300        218      206      194      183      172      163 154
320          235      222      210      198      187      177 167
340        252      239      226      214      202      191 181
360          270      255      242      229      217      206 196
380        287      272      258      245      233      221 210
400          304      289      275      261      248      236 224
420          322      306      291      277      263      251 22S
440          339      323      308      293      279      266 254
460          357      340      324      309      295      281 268
480          374      357      341      325      311    297  283
500          392      374      357      342      326      312 298
520          409      391      374      358      342      327 313
540          427      409      391      374      358      343 329
560          445      426      408      391      374      359 344
580          463      443      425      407      391      375 359
600          480      461      442      424      407      390 375
620          498      478      459      441      423      406 390
640          516      496      476      457      439      422 406
660          534      513      493      474      456      438 421
680          552      531      511      491      472      454 437
700          570      549      528      508      489      470 453
720          588      566      545      525      505      487 469
740          606      584      562      542      522      503 485
760          624      602      580      559      539      519 500
780          642      619      597      576      555      535 516
800          660      637      614      593      572      552 532
820          679      655      632      610      589      568 549
840          697      673      649      627      605      585 565
860          715      690      667      644      622      601 581
880          733      708      684      661      639      618 597
900          751      726        702      679      656      634 613
920          770      744      720      696      673      651 630
940          788      762      737      713      690      668 646
960          806      780      755      731      707      684 662
980          824      798      773      748      724      701 679
                                  5.27-8


If a licensee believes that the NRC is either using this RG or requesting or requiring the licensee to implement the methods or processes in this RG in a manner inconsistent with the discussion in this Implementation section, then the licensee may file a backfit appeal with the NRC in accordance with the guidance in NUREG-1409, Backfitting Guidelines, (Ref. 18) and the NRC Management Directive 8.4, Management of Facility-Specific Backfitting and Information Collection (Ref 19).
TABLE II  (Cont'd)
                                          RG 5.27, Rev. 1, Page 12
        MAXIMUM PERMISSIBL


REFERENCES6
==E. BACKGROUND==
1.  U.S. Code of Federal Regulations, Domestic Licensing of Production and Utilization Facilities, Part 50 (10 CFR 50), Title 10, Energy.
a = 1.3, P= = 90%
    G n=      4        5          6          7        8      9    10
1000        843      816        790        765      741    718  695
1200      1027      997        968        940      913    887  861
1400      1212    1180        1148      1117    1088    1059  1030
1600      1398    1363        1329      1296    1264    1232  1201
1800      1536    it48        1512      1476      1441    1407  1374
2000      1773    1734        1695      1657      1620    1584  1548
2200      1962    1920        1879      1839      1800    1761  1724
2400      2151    2107        2064      2022      1980    1940  1900
2600      2340    2294        2249      2205      2162    2119  2078
2800      2530    2482        2435      2389      2344    2300  2256
3000      2720    2670        2622      2574      2527    2481  2435
3200      2911    2859        2808      2759      2710    2662  2615
3400      3101    3048        2996      2944      2894    2844  2795
3600      3292    3238        3183      3130      3078    3027  2976
3800      3484    3427        3371      3317      3263    3210  3158
4000      3675    3617        3560      3503      3448    3393  3340
4200      3867    3807        3748      3691      3634    3577  3522
4400      4059    3998        3937      3878      3319    3762  3705
4600      4251    4188        4126      4066      4006    3946  3888
4800      4443    4379        4316      4253      4192    4131  4072
5000      4636    4570        4505      4442      4379    4317  4256
5200      4828    4761        4695      4630      4566    4502  4440
5400      5021    4953        4885      4819      4753    4688  4624
5600      5214    5144        5075      5007      4940    4874  4809:
5S00      5407    5336        5266      5196      5128    5061  4994
6000      5600    5528        5456      5386      5316    5247  5180
6200      5793    5720        5647      5575      5504    5434  5365
6400      5987    5912        5S38      5765      5692    5621  5551
6600      6180    6104        6029      5954      5831    580G  5737
6800      6373    6296        6220      6144      6070    5996  5923
7000      6567    6488        6411      6334      6258    6184  6110
7200      6761    6681        6602      6524      6447    6371  6296
7400      r9955    6874        6794      6715      6636    6559  6483
7600      7148    7066      6985      6905      6826    6747  6670
7800      7342    7259        7177      7096      7015    6936  6857
8000      7536    7452        7369      7286      7205    7124  7044
8200      7731    7645        7561      7477      7394    7313  7232
8400      7925    7838        7753      7668      7584    7501  7419
8600      8119    8031        7945      7859      7774    7690  7607
8800      3313    8225        8137      8050      7964    7879  7795
9000      8508    8418        8329      8241      8154    8063  7983
9200      8702    8611        8521      8433      8345    8257  8171
9400      8897    8805        8714      8624      8535    8447  8360
9600      9091    8998        8906      8815      8725    8636  8548
98-00    9286    9192        9099      9007      8916    8826  8737
                                5.27-9


2.  10 CFR 52, Licenses, Certifications, and Approvals for Nuclear Power Plants, Title 10,
APPENDIX A
    Energy
                        PROCEDURE FOR TESTING SNM DOORWAY MONITORS
3. 10 CFR 76, Physical Protection of Plants and Materials, Title 10, Energy
                                                              FOR
4. 10 CFR 73, Certification of Gaseous Diffusion Plants, Title 10, Energy
                                          FUNCTIONAL PERFORMANCE
5. U.S. Nuclear Regulatory Commission (NRC), Entry/Exit Control of Personnel Access to Protected Areas, Vital Areas, and Material Access Areas, Regulatory Guide (RG) 5.7, Washington, DC, Agencywide Document Access and Management System (ADAMS)
    Doorway monitors should be tested by employing a                background taken immediately after the test varies by test source of the same isotope of SNM the doorway                  more than 2vN from the background taken before the monitor is used to detect as follows:                              test, the test should be repeated, for such a difference indicates nonrandom fluctuations of the background or
    Accession No. ML003739976.
1. With the detection area unoccupied, measure and                  equipment malfunction. The probability of such an record background.                                                 occurrence due to the randomness of the background is less than 8%.
2. Determine alarm threshold T from Table I (see Appendix B).                                                         5. A calibration source (Appendix B) should be carried repeatedly to various places within the detection area of
3. Place a test source in the detection area of the                  the doorway monitor in simulation of actual use to doorway monitor. The test source should be such that                verify that the SNM can be detected everywhere within the activity in the detection area slightly exceeds the T            the detection area and to assure proper operation of level.* The doorway monitor should go into an alarm                  treadle pads, beam-break, or similar devices if the condition if operating properly.                                     doorway monitor is so equipped.


6. NRC, Access Control Systems: Technical Information for NRC Licensees, NUREG-1964, Washington, DC. (ML1115A078)
4. Remove test source to its original location and                  6. Doorway monitors used to search for concealed measure background once again. If the measurement of                uranium-233 should be tested with each uranium purification run, but no more frequently than daily. The
7.  Knoll, Glenn F., Radiation Detection and Measurement, 4th ed., John Wiley and Sons7, 2010.
*The test source may be improvised by partially shielding the        test source should be freshly purified uranium-233 calibration source.                                               (within four hours of removal of decay products).
                                                            5.27-10


8.  LA-UR-96-4505, An Optimized International Vehicle Monitor, R. L. York, D. A. Close, and P.
APPENDIX B
            PROCEDURE FOR DETERMINING MAXIMUM PERMISSIBL


E. Fehlau, Los Alamos National Labs, Los Alamos, NM (1997).8
==E. BACKGROUND==
9.  American Society for Testing and Materials (ASTM) C1189-11, Standard Guide to Procedures for Calibrating Automatic Pedestrian SNM Monitors, West Conshohocken, PA. 9
Background should be measured over several work                found from Table II, the sensitivity of the doorway shifts to determine the setpoints for alarm threshold              monitor will generally be below that specified as (with or without automatic background updating) to                 minimum in Regulatory Position C.l.b of this guide.
10. ASTM, C1112-99(2005), Standard Guide for Application of Radiation Monitors to the Control and Physical Security of Special Nuclear Material, West Conshohocken, PA.


11. ASTM C1237-99(2005), Standard Guide to In-Plant Performance Evaluation of Hand-Held SNM Monitors, West Conshohocken, PA.
assure that normal operation will be minimally affected by alarms due to high background.                                        The parameter n is a function of the background variation and the permissible false alarm rate and is The doorway monitor should be calibrated with the              calculated from amount of the appropriate isotope specified in Regula tory Positions C.l.b(1), (2), or (3) of this guide (e.g., 0.5                                                1 /2 gram plutonium-239 in 3 mm of brass).                                                    n >3.1 (var B)                          (2)
    The calibration procedure described below is essen tially a means of determining maximum permissible                      Generally, n is taken as an integer. If n satisfies the background for effective operation of the doorway                    above expression, the expected false alarm rate (Appen monitor.                                                            dix C) due to background fluctuations should be less than 0.1%. Larger values of n will decrease the expected
1. Place a calibration source variously about the detec            false alarm rate; however, the maximum allowable tion area and take readings to determine the least                  background for a given G will also decrease.


12. ASTM C993-97(2012), Standard Guide for In-Plant Performance Evaluation of Automatic Pedestrian SNM Monitors, West Conshohocken, PA.
sensitive point. This location of minimum sensitivity should be maintained as the calibration point.                      4. For doorway monitors equipped with automatic background updating systems, the alarm threshold is
2. Measure background over several workshifts to deter mine the periods of high background and the range of                                    Counts > B + nVii,                      (3)
background. A minimum of 20 measurements should be taken. The variance of the background is given by                  where n should be derived from expression (2), and the instrument set accordingly.


6  Publicly available NRC published documents are available electronically through the NRC Library on the NRCs public Web site at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html The documents can also be viewed online or printed for a fee in the NRCs Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD. For problems with ADAMS, contact the PDR staff at 301-415-4737 or (800) 397-4209; fax (301) 415-3548; or e-mail pdr.resource@nrc.gov.
N
              Var B      1 N*-       (Bi-B)2                (1)       5. The high-background alarm should be set at the B
                                                                    value given in Table II for the measured G and calculated n values.


7  Copies of this publication and, or current edition are available thru the Wiley website at: http://www.wiley.com/
where N is the number of measurements, B is the mean ith of the background measurements, and Bi is the                      6. For doorway monitors not equipped with an auto background measurement.                                             matic background update, the value of n determined above should be employed in the use of the doorway
8  Copies of this publication are available thru the US Department of Energy, Office of Scientific and Technical Information (OSTI) website at: http://www.osti.gov/scitech/servlets/purl/444040
3. With the calibration source at the calibration point,            monitor according to Regulatory Position C.2.a.
9  Copies of American Society for Testing and Materials (ASTM) standards may be purchased from ASTM, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; telephone 610-832-9585. Purchase information is available through the ASTM Web site at http://www.astm.org.


RG 5.27, Rev. 1, Page 13
the mean gross counts G should be determined during a                *The false alarm rate is estimated by the probability that an period of high background to establish the upper                      observation of a quantity distributed normally about some operating range of the doorway monitor. Table II lists                value X will exceed X by n(Std. deviation of X). The factor 3.1 various maximum permissible background levels for a                  limits the false alarm rate to 0.1%, while the factor given value of G for values of the parameters n and a.               (Var B/B) 1 /2 compensates for observed deviations in the During periods when the background exceeds the value                  background distribution from Poisson.


13. ASTM C1270-97(2012), Standard Practice for Detection Sensitivity Mapping of In-Plant Walk Through Metal Detectors, West Conshohocken, PA.
5.27-11


14. ASTM C1270-97(2012), Standard Practice for Detection Sensitivity Mapping of In-Plant Walk Through Metal Detectors, West Conshohocken, PA.
APPENDIX C
                                DETECTION CONFIDENCE LIMITS, THRESHOLDS,
                                  AND MAXIMUM PERMISSIBL


15. ASTM C1269-97(2012), Standard Practice for Adjusting the Operational Sensitivity Setting of In-Plant Walk-Through Metal Detectors, West Conshohocken, PA
==E. BACKGROUND==
16. ASTM C1309-97(2012), Standard Practice for Performance Evaluation of In-Plant Walk-Through Metal Detectors, West Conshohocken, PA
With a calibration source at the calibration point, the            The condition for a false alarm* is written as condition for an alarm is, in general, b= B +j      a-'"B> T                  (4)
17. ASTM C1236-99(2005), Standard Guide for In-Plant Performance Evaluation of Automatic Vehicle SNM Monitors, (Withdrawn 2014) West Conshohocken, PA
                  g> T = B + m/Va' B                  (1)       where b is a single measurement without the source and
18. International Atomic Energy Agency (IAEA), IAEA Nuclear Security Series No. 13, Nuclear Security Recommendations on Physical Protection of Nuclear Material and Nuclear Facilities, Vienna, Austria, January 2011.10
                                                                  0 is a number corresponding to a false alarm probability Pp. For P = 0.1%, 0 = 3.1. Hence the necessary where g is a single measurement of G (the mean                    condition for maintaining a false alarm rate below Pp is radiation level with the source), B is the mean back ground, and m is some multiplier. The detection                                  b= B+      -"B    < B+ m ar.                 (5)
19. NRC, Backfitting Guidelines, NUREG-1409, Washington, DC. (ML032230247)
confidence limit is the probability that with the calibra However, the doorway monitor actually compares b iton source at the calibration point, any single determin with B + ni, hence the condition on n becomes ation of G will exceed a threshold T, i.e., the above inequality will be satisfied. For any given probability Pa.,                       orV        < rn'VaTr    = nvff              (6)
20. NRC, Management of Facility-specific Backfitting and Information Collection, Management Directive 8.4, Washington, DC. (ML12059A460)
there exists a value a such that                                  or g > G-                             (2)                            n>0 ( Va B ) 1/2                        (7)
10  Copies of International Atomic Energy Agency (IAEA) documents may be obtained through their Web site:
                                                                      In Table I threshold values of T were determined by with a probability of Pa, where g is any single measure          substituting equation (6) into equation (3):
    WWW.IAEA.Org/ or by writing the International Atomic Energy Agency P.O. Box 100 Wagramer Strasse 5, A-1400
ment of the quantity G. Hence the condition for a detection confidence limit of Pais                                                          T = B + nv'r The values of B in Table II were then calculated for G- &      _-r*-G > T = B + m,,/'r B.       (3)       a = 1.3 and a = 0 from equation (3) assuming that, for the determination of G, the background should be reasonably stable and therefore \/Var G -\
    Vienna, Austria. Telephone (+431) 2600-0, Fax (+431) 2600-7, or E-Mail at Official.Mail@IAEA.Org RG 5.27, Rev. 1, Page 14
For a given value of G, solving (3) gives the maximum permissible B at which the doorway monitor will detect            *False alarm means an alarm condition generated by statistical the source with a confidence Pr-For Pa = 90%, a = 1.3,             fluctuations in the background radiation or by instabilities of the electronics which appear as background fluctuations when and for Pa = 50%, a = 0.                                           the detection area is occupied.


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Revision as of 10:21, 28 March 2020

Special Nuclear Material Doorway Monitors
ML003740050
Person / Time
Issue date: 06/30/1974
From:
Office of Nuclear Regulatory Research
To:
References
RG-5.27
Download: ML003740050 (12)
v • d • e


June 1974 U.S. ATOMIC ENERGY COMMISSION

REGULATORY GUIDE

DIRECTORATE OF REGULATORY STANDARDS

REGULATORY GUIDE 5.27 SPECIAL NUCLEAR MATERIAL DOORWAY MONITORS

A. INTRODUCTION

2. General Characteristics Typically, the detectors of a doorway monitor are Paragraph (b), "Exit Requirement," of § 73.60, "Ad NaI(Tl) scintillators or solid or liquid organic scintilla ditional Requirements for the Physical Protection of tors. Geiger-Mueller detectors have also been used in this Special Nuclear Material at Fixed Sites," of 10 CFR Part application, although the lower intrinsic efficiency of

73, "Physical Protection of Plants and Materials,"

these detectors renders them less suitable than scintilla requires that individuals exiting from material access tion detectors.

areas be searched for concealed special nuclear material Detectors are arranged such that a detection area is (SNM). This guide describes means acceptable to the Regulatory staff for employing SNM doorway monitors defined by a plane perpendicular to the line of passage of individuals through the doorway monitor. Various to comply with that requirement.

arrangements of the detectors are possible; however, specific placement of detectors is usually dictated by the

B. DISCUSSION

need to eliminate dead spots.

Special nuclear material doorway monitors provide an Some commercially available doorway monitors are efficient, sensitive, and reasonably unobtrusive means of equipped with an automatic background updating searching individuals exiting from a material access area system. The automatic background updating system for concealed SNM. With proper installation and opera periodically monitors and averages the background. A

tion, gram quantities or less of SNM can be detected doorway monitor equipped with an automatic back with a high level of reliability while maintaining a low ground updating system is also provided with a treadle false alarm rate. pad or beam-break system to indicate that the sensitive area is occupied. When the sensitive area is occupied, the I. Theory of Operation radiation level detected by the doorway monitor is The doorway monitor is composed of a detector compared with the mean background. If the level is unit(s), associated electronics, and alarm logic. The "significantly" greater than the mean background, an detector unit(s) is sensitive to the radiations which alarm condition ensues. Significance is usually deter emanate from the SNM and responds to these radiations mined by comparing the radiation level when the (usually gamma rays) by generating current pulses. These sensitive area is occupied with the mean background plus pulses are amplified, filtered, and fed to alarm logic some multiple of the square root of the mean back v'hich interprets the number (or rate) of pulses in some ground*

period of time, for example, one second. The alarm logic may be either a digital or analog system; in either case, if *The square root of the mean of a Poisson-distributed quantity the number (or rate) of pulses exceeds a set level, an is the unbiased estimate of the standard deviation of that alarm condition ensues. quantity.

USAEC REGULATORY GUIDES Copies of published guides may be obtained by request indicating the divisions desired to the US. Atomic Energy Commission, Washington, D.C. 20545, Regulatory Guides are issued to describe and make available to the public Attention: Director of Regulatory Standards. Comments and suggestions for methods acceptable to the AEC Regulatory staff of implementing sPecific parts of improvements in these guides ae encouraged and should be sent to the Secretary the Commission's regulations, to delineate techniques .ned by the staff in of the Commission, US. Atomic Energy Commission, Washington, D.C. 20545, evaluating specific problems or postulated accidents, or to provide guidance to Attention: Chief, Public Proceedings Staff.

applicants. Regulatory Guides are not substitutes for regulations and compliance with them is not required. Methods and solutions different from those set out in The guides ae issued in the following ten broad divisions:

the guides will be acceptable if they provide a basis for the findings requisite to 6. Products the imuance or ontinuance of a permit or license by the Commissio

n.

1. Power Reactors

2. Reaseerd enidTest Reactors

7. Transportation

3. Fuels and Materials Facilities 8. Occupational Health Published guidas will be revised periodically, asappropriate, to accommodate 4. Environmental and Siting 9. Antitrust Review comments amd to refloct new informeaion or experience. 5. Materials and Plant Protection 1

0. General

Thus the condition for an alarm can be written as Areas, and Material Access Areas,") in such a manner that objects cannot be passed over, around, or under the G > B + n, detection area.

. (2) The detector elements should be designed and where B is the mean background, G is the radiation level positioned so that detection sensitivity is as uniform as with the sensitive area occupied, and n is a multiplier, possible over the detection area; in no case should any usually an integer between 4 and 10.* The value of n areas where SNM is not detectible be permitted.

directly affects the false alarm rate, and the combination (3) Power, sensitivity, and other controls of the of B and n affect the sensitivity. doorway monitor should be tamper-safed when unat tended.

Although the automatic background updating system (4) Signal lines connecting alarm relays to the allows unattended use of the doorway monitor, for alarm monitor should be supervised.

technical reasons, the system may be less effective in (5) Some doorway monitors may require an indi certain situations. Techniques to prevent this are des vidual to occupy the detection area for a specified time, cribed in the Regulatory Position. longer than a normal walking pace would provide. If this is the case, the doorway monitor should be provided Doorway monitors not equipped with an automatic with a treadle pad and a "clock" device to assure that background updating system either must rely on the the detection area is occupied for the requisite time. An inherent sensitivity of the instrument and low back aural and visual indication should be given if an ground variation to ensure that concealed SNM will be individual being searched does not occupy the area detected or must be attended so that a measurement of sufficiently long.

background can be taken immediately prior to use and b. System Specification the alarm level set to maintain the desired sensitivity to (1) Plutonium-239. A doorway monitor used to concealed SNM. As with the doorway monitor equipped detect plutonium should be capable of detecting a with an automatic background updating system, a minimum of 0.5 gram of plutonium-239 encased in a doorway monitor not so equipped compares the activity minimum of 3 mm of brass at a 90% confidence limit.

with the detection area occupied with some set value, The false alarm rate should be less than 0.1% (Appendix usually the measurement of background taken just prior C).

to use. In any case, the expression above can be used as a (2) Uranium-233. A doorway monitor used to condition of alarm by replacing B + nr'Wwith the set detect uranium-233 should be capable of detecting level. within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of purification* a minimum of 1 gram of uranium-233 containing between 7 and 10 ppm of Whether or not a doorway monitor is equipped with uranium-232 encased in a minimum of 3 mm of brass at an automatic background updating system, high back a 90% confidence limit. The false alarm rate should be ground activity will decrease sensitivity. Measuring activ less than 0.1% (Appendix C).

ity for longer periods will somewhat compensate for (3) Uranium-235. A doorway monitor used to high background; however, longer measurement periods detect uranium-235 should be capable of detecting a will make use of the doorway monitor less convenient. minimum of 3 grams of uranium-235 contained in uranium enriched to 20% or more in the uranium-235

C. REGULATORY POSITION

isotope encased in a minimum of 3 mm of brass at a 50%

confidence limit. The false alarm rate should be less than

1. Minimum Qualifications for SNM Doorway Monitors 0.1% (Appendix C).

a. General

(1) SNM Doorway monitors should be used in 2. Use of Doorway Monitors conjunction with a metal detector and should be In general, doorway monitors should be used in installed in a passageway (see Regulatory Guide 5.7, locations of minimum background and minimum back

"Control of Personnel Access to Protected Areas, Vital ground fluctation. If circumstances dictate use of a doorway monitor in an area of high background,

  • Note that, in general, for a count rate system, the condition for sufficient shielding should be provided to maintain afarm should be modified to account for the response time of necessary sensitivity.

the instrument as follows:

a. Attended Doorway Monitor G > B + n1]0l - e-t/7) (1) If the doorway monitor is attended during where t is the counting time and r is the time constant of the use, it need not be equipped with an automatic instrument. If, as should be the case, t/,r > 5 the added factor is essentially unity. *Purification means removal of all decay products.

5.27-2

(d) Activate the electronics and alarm logic background updating system, although such capability is when an individual is within the detection area and preferred. initiate operation of the doorway monitor.

(2) Prior to each use* of a doorway monitor not (3) An alarm should sound in the central alarm equipped with an automatic background updating station if, when occupied, the activity in the detection system, a measurement of background should be taken, area exceeds the internally set threshold level (the mean and the alarm threshold should be set to the proper background plus some multiple times the square root of value listed in Table I for the measured background and the mean background), as such a situation would the proper n value as determined in Appendix B. Each indicate the presence of SNM upon the individual being individual to be checked should, in turn, enter the checked.

detection area and be required to remain sufficiently (4) The doorway monitor should be equipped long for the device to operate properly. During use, the with a high-background alarm which will sound if the background should be checked and the alarm threshold average background at the location of the doorway reset at least each 15 minutes. monitor exceeds the appropriate maximum permissible

(3) With the individual being checked in the background level listed in Table II as determined in detection area, an alarm should sound if the activity in Appendix C. The doorway monitor should not be used the detection area exceeds the alarm threshold T, as such during such periods of high background. Other moni a situation would indicate the presence of SNM. tored exits should be used.

(4) The doorway monitor should be equipped with a high-background alarm which will sound if the 3. Testing and Calibration measurement of background exceeds the appropriate a. Testing maximum permissible background level listed in Table II Doorway monitors should be tested by passing an as determined in Appendix C. The doorway monitor appropriate source of the amount and isotope specified should not be used during such periods of high back in Regulatory Position C.l.b. through the doorway ground. monitor no less frequently than once per day.* In b. Unattended Doorway Monitor addition, a functional performance test should be carried

(1) If the doorway monitor is unattended, an out at least once per week. An acceptable functional automatic background update system should be incor performance test procedure is discussed in Appendix A

porated into the doorway monitor electronics and alarm of this guide logic. The control circuitry, if possible, should be located b. Calibration at the central alarm station (or other monitoring point). Doorway monitors should be calibrated with a

(2) Door interlocks and closed-circuit TV in source of the amount, configuration, and variety of SNM

combination with beam breaks, motion detectors, and/ to be detected (e.g., 0.5 gram Pu in 3 mm of brass).

or treadle pads, should be employed to: Calibration should be carried out according to a proce (a) Indicate to the person manning the central dure such as that in Appendix B.

alarm station that an individual has entered the secure c. Operating Instructions access passageway and/or is approaching the doorway Operating instructions should be posted near the monitor, doorway monitor,* if attended, or at the monitoring (b) Allow observation of the individual ap point if the doorway monitor is unattended. The proaching the doorway monitor, instructions should clearly indicate the procedure for use (c) Preclude a slow approach to the sensitive of the doorway monitor and the procedure for setting area of the doorway monitor, and thresholds, if appropriate. In addition, the operating instructions should indicate what corrective action is to

  • By use is meant an individual or several individuals, each, in be taken and who is to be notified in the event of a turn, being checked for SNM by the doorway monitor. The malfunction.

maximum period between threshold sets while the doorway monitor is in use is determined by the stability of local *Doorway monitors used to search for concealed U-233 should background and may necessarily be more frequent than every be tested according to §6 of Appendix A.

15 minutes.

5.27-3

TABLE I

ALARM THRESHOLD

T

B n= 4 5 6 7 8 9 10

100 140 150 160 170 180 190 200

120 164 175 186 197 208 219 230

140 .187 199 211 223 235 246 258

160 211 223 236 249 261 274 286

180 234 247 260 274 287 301 314

200 257 271 285 299 313 327 341

220 279 294 309 324 339 353 368

240 302 317 333 348 364 379 395

260 324 341 357 373 389 405 421

280 347 364 380 397 414 431 447

300 369 387 404 421 439 456 473

320 392 409 427 445 463 481 499

340 414 432 451 469 488 506 524

360 436 455 474 493 512 531 550

380 458 477 497 516 536 555 575

400 480 500 520 540 560 580 600

420 502 522 543 563 584 604 625

440 524 545 566 587 608 629 650

460 546 567 589 610 632 653 674

480 568 590 611 633 655 677 699

500 589 612 634 657 679 701 724

520 611 634 657 680 702 725 748

540 633 656 679 703 726 749 772

560 655 678 702 726 749 773 797

580 676 700 724 749 773 797 821

600 698 722 747 771 796 820 845

620 720 744 769 794 819 844 869

640 741 766 792 817 842 868 893

660 763 788 814 840 866 891 917

680 784 810 836 863 889 915 941

700 806 832 859 885 912 938 965

720 827 854 881 908 935 961 988

740 849 876 903 930 958 985 1012

760 870 898 925 953 981 1008 1036

780 892 920 948 975 1003 1031 1059

800 913 941 970 998 1026 1055 1083

820 935 963 992 1020 1049 1078 1106

840 956 985 1014 1043 1072 1101 1130

860 977 1007 1036 1065 1095 1124 1153

880 999 1028 1058 1088 1117 1147 1177

900 1020 1050 1080 1110 1140 1170 1200

920 1041 1072 1102 1132 1163 1193 1223

940 1063 1093 1124 1155 1185 1216 1247

960 1084 1115 1146 1177 1208 1239 1270

980 1105 1137 1168 1199 1230 1262 1293

5.27-4

TABLE I (Cont'd)

ALARM THRESHOLD

T

B n = 4 5 6 7 8 9

1000 1126 1158 1190 1221 1253 1285 1316

1200 1339 1373 1408 1442 1477 1512 1546

1400 1550 1587 1624 1662 1699 1737 1774

1600 1760 1800 1840 1880 1920 1960 2000

1800 1970 2012 2055 2097 2139 2182 2224

2000 2179 2224 2268 2313 2358 2402 2447

2200 2388 2435 2481 2528 2575 2622 2669

2400 2596 2645 2694 2743 2792 2841 289C

2600 2804 2855 2906 2957 3008 3059 3110

2800 3012 3065 3117 3170 3223 3276 3329

3000 3219 3274 3329 3383 3438 3493 3548

3200 3426 3483 3539 3596 3653 3709 3766

3400 3633 3692 3750 3808 3866 3925 3983

3600 3840 3900 3960 4020 4080 4140 4200

3800 4047 4108 4170 4232 4293 4355 4416

4000 4253 4316 4379 4443 4506 4569 4632

4200 4459 4524 4589 4654 4718 4783 4848

4400 4665 4732 4798 4864 4931 4997 5063

4600 4871 4939 5007 5075 5143 5210 5278

4800 5077 5146 5216 5285 5354 5424 5493

5000 5283 5354 5424 5495 5566 5636 5707

5200 5483 5561 5633 5705 5777 5849 5921

5400 5694 5767 5841 5914 5988 6061 6135

5600 5899 5974 6049 6124 6199 6273 6348

5800 6105 6181 6257 6333 6409 6485 6562

6000 6310 6387 6465 6542 6620 6697 6775

6200 6515 6594 6672 6751 6830 6909 6987

6400 6720 6800 6880 6960 7040 7120 7200

6600 6925 7006 7087 7169 7250 7331 7412

6800 7130 7212 7295 7377 7460 7542 7625

7000 7335 7418 7502 7586 7669 7753 7837

7200 7539 7624 7709 7794 7879 7964 8049

7400 7744 7830 7916 8002 8088 8174 8260

7600 7949 8036 8123 8210 8297 8385 8472

7800 8153 8242 8330 8418 8507 8595 8683

8000 8358 8447 8537 8626 8716 8805 8894

8200 8562 8653 8743 8834 8924 9015 9106

8400 8767 8858 8950 9042 9133 9225 9317

8600 8971 9064 9156 9249 9342 9435 9527

8800 9175 9269 9363 9457 9550 9644 9738

9000 9379 9474 9569 9664 9759 9854 9949

9200 9584 9680 9775 9871 9967 10063 10159

9400 9788 9885 9932 10079 10176 10273 10370

9600 9992 10090 10188 10286 10384 10482 10580

9800 10196 10295 10394 10493 10592 10691 10790

5.27-5

TABLE II

MAXIMUM PERMISSIBL

E. BACKGROUND

a = 0, Pa = 50%

B

G n= 4 5 6 7 8 10

9

100 67 61 55 50 46 42 38

120 83 76 70 64 59 54 50

140 100 92 85 78 72 67 62

160 117 108 100 93 86 80 74

180. 134 124 116 107 100 93 87

200 151 141 131 123 114 107 100

220 168 157 147 138 129 121 113

240 186 174 163 153 144 135 127

260 203 191 180 169 159 150 141

280 221 208 196 185 174 165 155

300 238 225 213 201 190 179 170

320 256 242 229 217 205 194 184

340 274 259 246 233 221 210 199

360 292 277 263 249 237 225 214

380 310 294 280 266 253 240 229

400 328 312 297 282 269 256 244

420 346 329 314 299 285 272 259

440 364 347 331 316 301 287 274

460 382 365 348 332 317 303 290

480 400 382 365 349 334 319 305

500 418 400 383 366 350 335 321

520 436 418 400 383 367 351 337

540 455 436 417 400 383 367 352

560 473 454 435 417 400 384 368

580 491 471 452 434 417 400 384

600 510 489 470 451 433 416 400

620 528 507 488 468 450 433 416

640 546 525 505 486 467 449 432

660 565 543 523 503 484 466 448

680 583 562 541 520 501 482 464

700 602 580 558 538 518 499 481

720 620 598 576 555 535 516 497

740 639 616 594 573 552 532 513

760 657 634 612 590 569 549 530

780 676 652 629 607 586 566 546

800 695 671 647 625 603 583 563

820 713 689 665 643 621 600 579

840 732 707 683 660 638 617 596

860 750 725 701 678 655 633 613

880 769 744 719 695 673 650 629

900 788 762 737 713 690 667 646

920 806 780 755 731 707 685 663

940 825 799 773 748 725 702 679

960 844 817 791 766 742 719 696

980 863 835 809 784 760 736 713

5.27-6

TABLE II (Cont'd)

MAXIMUM PERMISSIBL

E. BACKGROUND

a -'0, Pa = 50Z

B

G n = 4 5 6 7 8 9 10

1000 881 854 827 802 777 753 730

1200 1069 1039 1009 981 953 926 900

1400 1258 1225 1193 1161 1131 1101 1073

1600 1448 1412 1377 1343 1310 1278 1247

1000 1638 1600 1563 1527 1491 1457 1423

2000 1829 1789 1749 1710 1673 1636 1600

2200 2020 1978 1936 1895 1855 1816 1778

2400 2212 2167 2124 2081 2039 199D 1958

2600 2404 2357 2312 2267 2223 2180 2138

2800 2596 2548 2500 2453 2407 2363 2318

3000 2789 2738 2689 2640 2593 2546 2500

3200 29S2 2929 2878 2828 2778 2730 2682

3400 3175 3121 3068 3016 2964 2914 2865

3600 3368 3312 3258 3204 3151 3099 3048

3800 3561 3504 3448 3392 3338 3284 3232

4000 3755 3696 3638 3581 3525 3470 3416

4200 3949 3888 3829 3770 3713 3656 3600

4400 4143 4081 4020 3960 3900 3842 3785

4600 4337 4273 4211 4149 4088 4029 3970

4800 4531 4466 4402 4339 4277 4216 4155

5000 4725 4659 4593 4529 4465 4403 4341

5200 4919 4852 4785 4719 4654 4590 4527

5400 5114 5045 4977 4910 4843 4778 4713

5600 5309 5238 5169 5100 5032 4966 4900

5800 5503 5432 5361 5291 5222 5154 5087

6000 5698 5625' 5553 5482 5411 5342 5274

6200 5893 5819 5745 5673 5601 5531 5461

6400 6088 6012 5938 5864 5791 5719 5648

6600 6283 6206 6130 6055 5981 5908 5836

6800 6478 6400 6323 6247 6172 60'97 6024

7000 6673 6594 6516 6438 6362 6286 6212

7200 6868 6788 6709 6630 6552 6476 6400

7400 7064 6982 6902 6822 6743 6665 6588

7600 7259 7176 7095 7014 6934 6855 6777

7800 7455 7371 7288 7206 7125 7045 6965

8000 7650 7565 7481 7398 7316 7234 7154

8200 7846 7760 7674 7590 7507 7425 7343

8400 8041 7954 7868 7782 7698 7615 7532

8600 8237 8149 8061 7975 7889 7805 7721

8800 8433 8343 8255 8167 8081 7995 7911

9000 8628 8538 8449 8360 8272 8186 8100

9200 8824 8733 8642 8553 8464 8376 8290

9400 9020 8928 8836 8745 8656 8567 8479

9600 9216 9122 9030 8938 8348 8758 8669

9800 9412 9317 9224 9131 9039 8949 8859

5.27-7

TABLE II (Cont'd)

MAXIMUM PERMISSIBL

E. BACKGROUND

S= 1.3, Pa = 90%

B

G n 4 5 6 7 8 9 10

100 57 51 46 42 38 34 31

120 72 65 59 54 49 45 41

140 87 80 73 67 62 57 52

160 103 95 87 81 75 69 64

180 119 110 102 95 88 81 76

200 135 126 117 109 101 94 FS

220 151 141 132 123 115 107 100

240 168 157 147 138 129 121 113

260 185 173 163 153 143 135 127

280 201 189 178 168 158 149 1L0

300 218 206 194 183 172 163 154

320 235 222 210 198 187 177 167

340 252 239 226 214 202 191 181

360 270 255 242 229 217 206 196

380 287 272 258 245 233 221 210

400 304 289 275 261 248 236 224

420 322 306 291 277 263 251 22S

440 339 323 308 293 279 266 254

460 357 340 324 309 295 281 268

480 374 357 341 325 311 297 283

500 392 374 357 342 326 312 298

520 409 391 374 358 342 327 313

540 427 409 391 374 358 343 329

560 445 426 408 391 374 359 344

580 463 443 425 407 391 375 359

600 480 461 442 424 407 390 375

620 498 478 459 441 423 406 390

640 516 496 476 457 439 422 406

660 534 513 493 474 456 438 421

680 552 531 511 491 472 454 437

700 570 549 528 508 489 470 453

720 588 566 545 525 505 487 469

740 606 584 562 542 522 503 485

760 624 602 580 559 539 519 500

780 642 619 597 576 555 535 516

800 660 637 614 593 572 552 532

820 679 655 632 610 589 568 549

840 697 673 649 627 605 585 565

860 715 690 667 644 622 601 581

880 733 708 684 661 639 618 597

900 751 726 702 679 656 634 613

920 770 744 720 696 673 651 630

940 788 762 737 713 690 668 646

960 806 780 755 731 707 684 662

980 824 798 773 748 724 701 679

5.27-8

TABLE II (Cont'd)

MAXIMUM PERMISSIBL

E. BACKGROUND

a = 1.3, P= = 90%

G n= 4 5 6 7 8 9 10

1000 843 816 790 765 741 718 695

1200 1027 997 968 940 913 887 861

1400 1212 1180 1148 1117 1088 1059 1030

1600 1398 1363 1329 1296 1264 1232 1201

1800 1536 it48 1512 1476 1441 1407 1374

2000 1773 1734 1695 1657 1620 1584 1548

2200 1962 1920 1879 1839 1800 1761 1724

2400 2151 2107 2064 2022 1980 1940 1900

2600 2340 2294 2249 2205 2162 2119 2078

2800 2530 2482 2435 2389 2344 2300 2256

3000 2720 2670 2622 2574 2527 2481 2435

3200 2911 2859 2808 2759 2710 2662 2615

3400 3101 3048 2996 2944 2894 2844 2795

3600 3292 3238 3183 3130 3078 3027 2976

3800 3484 3427 3371 3317 3263 3210 3158

4000 3675 3617 3560 3503 3448 3393 3340

4200 3867 3807 3748 3691 3634 3577 3522

4400 4059 3998 3937 3878 3319 3762 3705

4600 4251 4188 4126 4066 4006 3946 3888

4800 4443 4379 4316 4253 4192 4131 4072

5000 4636 4570 4505 4442 4379 4317 4256

5200 4828 4761 4695 4630 4566 4502 4440

5400 5021 4953 4885 4819 4753 4688 4624

5600 5214 5144 5075 5007 4940 4874 4809:

5S00 5407 5336 5266 5196 5128 5061 4994

6000 5600 5528 5456 5386 5316 5247 5180

6200 5793 5720 5647 5575 5504 5434 5365

6400 5987 5912 5S38 5765 5692 5621 5551

6600 6180 6104 6029 5954 5831 580G 5737

6800 6373 6296 6220 6144 6070 5996 5923

7000 6567 6488 6411 6334 6258 6184 6110

7200 6761 6681 6602 6524 6447 6371 6296

7400 r9955 6874 6794 6715 6636 6559 6483

7600 7148 7066 6985 6905 6826 6747 6670

7800 7342 7259 7177 7096 7015 6936 6857

8000 7536 7452 7369 7286 7205 7124 7044

8200 7731 7645 7561 7477 7394 7313 7232

8400 7925 7838 7753 7668 7584 7501 7419

8600 8119 8031 7945 7859 7774 7690 7607

8800 3313 8225 8137 8050 7964 7879 7795

9000 8508 8418 8329 8241 8154 8063 7983

9200 8702 8611 8521 8433 8345 8257 8171

9400 8897 8805 8714 8624 8535 8447 8360

9600 9091 8998 8906 8815 8725 8636 8548

98-00 9286 9192 9099 9007 8916 8826 8737

5.27-9

APPENDIX A

PROCEDURE FOR TESTING SNM DOORWAY MONITORS

FOR

FUNCTIONAL PERFORMANCE

Doorway monitors should be tested by employing a background taken immediately after the test varies by test source of the same isotope of SNM the doorway more than 2vN from the background taken before the monitor is used to detect as follows: test, the test should be repeated, for such a difference indicates nonrandom fluctuations of the background or

1. With the detection area unoccupied, measure and equipment malfunction. The probability of such an record background. occurrence due to the randomness of the background is less than 8%.

2. Determine alarm threshold T from Table I (see Appendix B). 5. A calibration source (Appendix B) should be carried repeatedly to various places within the detection area of

3. Place a test source in the detection area of the the doorway monitor in simulation of actual use to doorway monitor. The test source should be such that verify that the SNM can be detected everywhere within the activity in the detection area slightly exceeds the T the detection area and to assure proper operation of level.* The doorway monitor should go into an alarm treadle pads, beam-break, or similar devices if the condition if operating properly. doorway monitor is so equipped.

4. Remove test source to its original location and 6. Doorway monitors used to search for concealed measure background once again. If the measurement of uranium-233 should be tested with each uranium purification run, but no more frequently than daily. The

  • The test source may be improvised by partially shielding the test source should be freshly purified uranium-233 calibration source. (within four hours of removal of decay products).

5.27-10

APPENDIX B

PROCEDURE FOR DETERMINING MAXIMUM PERMISSIBL

E. BACKGROUND

Background should be measured over several work found from Table II, the sensitivity of the doorway shifts to determine the setpoints for alarm threshold monitor will generally be below that specified as (with or without automatic background updating) to minimum in Regulatory Position C.l.b of this guide.

assure that normal operation will be minimally affected by alarms due to high background. The parameter n is a function of the background variation and the permissible false alarm rate and is The doorway monitor should be calibrated with the calculated from amount of the appropriate isotope specified in Regula tory Positions C.l.b(1), (2), or (3) of this guide (e.g., 0.5 1 /2 gram plutonium-239 in 3 mm of brass). n >3.1 (var B) (2)

The calibration procedure described below is essen tially a means of determining maximum permissible Generally, n is taken as an integer. If n satisfies the background for effective operation of the doorway above expression, the expected false alarm rate (Appen monitor. dix C) due to background fluctuations should be less than 0.1%. Larger values of n will decrease the expected

1. Place a calibration source variously about the detec false alarm rate; however, the maximum allowable tion area and take readings to determine the least background for a given G will also decrease.

sensitive point. This location of minimum sensitivity should be maintained as the calibration point. 4. For doorway monitors equipped with automatic background updating systems, the alarm threshold is

2. Measure background over several workshifts to deter mine the periods of high background and the range of Counts > B + nVii, (3)

background. A minimum of 20 measurements should be taken. The variance of the background is given by where n should be derived from expression (2), and the instrument set accordingly.

N

Var B 1 N*- (Bi-B)2 (1) 5. The high-background alarm should be set at the B

value given in Table II for the measured G and calculated n values.

where N is the number of measurements, B is the mean ith of the background measurements, and Bi is the 6. For doorway monitors not equipped with an auto background measurement. matic background update, the value of n determined above should be employed in the use of the doorway

3. With the calibration source at the calibration point, monitor according to Regulatory Position C.2.a.

the mean gross counts G should be determined during a *The false alarm rate is estimated by the probability that an period of high background to establish the upper observation of a quantity distributed normally about some operating range of the doorway monitor. Table II lists value X will exceed X by n(Std. deviation of X). The factor 3.1 various maximum permissible background levels for a limits the false alarm rate to 0.1%, while the factor given value of G for values of the parameters n and a. (Var B/B) 1 /2 compensates for observed deviations in the During periods when the background exceeds the value background distribution from Poisson.

5.27-11

APPENDIX C

DETECTION CONFIDENCE LIMITS, THRESHOLDS,

AND MAXIMUM PERMISSIBL

E. BACKGROUND

With a calibration source at the calibration point, the The condition for a false alarm* is written as condition for an alarm is, in general, b= B +j a-'"B> T (4)

g> T = B + m/Va' B (1) where b is a single measurement without the source and

0 is a number corresponding to a false alarm probability Pp. For P = 0.1%, 0 = 3.1. Hence the necessary where g is a single measurement of G (the mean condition for maintaining a false alarm rate below Pp is radiation level with the source), B is the mean back ground, and m is some multiplier. The detection b= B+ -"B < B+ m ar. (5)

confidence limit is the probability that with the calibra However, the doorway monitor actually compares b iton source at the calibration point, any single determin with B + ni, hence the condition on n becomes ation of G will exceed a threshold T, i.e., the above inequality will be satisfied. For any given probability Pa., orV < rn'VaTr = nvff (6)

there exists a value a such that or g > G- (2) n>0 ( Va B ) 1/2 (7)

In Table I threshold values of T were determined by with a probability of Pa, where g is any single measure substituting equation (6) into equation (3):

ment of the quantity G. Hence the condition for a detection confidence limit of Pais T = B + nv'r The values of B in Table II were then calculated for G- & _-r*-G > T = B + m,,/'r B. (3) a = 1.3 and a = 0 from equation (3) assuming that, for the determination of G, the background should be reasonably stable and therefore \/Var G -\

For a given value of G, solving (3) gives the maximum permissible B at which the doorway monitor will detect *False alarm means an alarm condition generated by statistical the source with a confidence Pr-For Pa = 90%, a = 1.3, fluctuations in the background radiation or by instabilities of the electronics which appear as background fluctuations when and for Pa = 50%, a = 0. the detection area is occupied.

5.27-12


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