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
{{#Wiki_filter:June 1974 U.S. ATOMIC ENERGY COMMISSION  
July 2015 OFFICE OF NUCLEAR REGULATORY RESEARCH
REGULATORY GUIDE
Revision 1 REGULATORY GUIDE
DIRECTORATE OF REGULATORY STANDARDS
  Technical Lead A. Tardiff  Written suggestions regarding this guide or development of new guides may be submitted through the NRC's public Web site under the Regulatory Guides document collection of the NRC Library at http://www.nrc.gov/reading
REGULATORY GUIDE 5.27 SPECIAL NUCLEAR MATERIAL DOORWAY MONITORS
-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 NRC's 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 NRC's 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.  REGULATORY GUIDE 5.27 (Draft was issued as DG
-5038, dated March 2014)
  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). 
Paragraph (b), "Exit Requirement," of § 73.60, "Ad ditional Requirements for the Physical Protection of Special Nuclear Material at Fixed Sites," of 10 CFR Part  
 
73, "Physical Protection of Plants and Materials,"  
For holders of a reactor license under Title 10 of the Code of Federal Regulations (10 CFR)
requires that individuals exiting from material access areas be searched for concealed special nuclear material (SNM). This guide describes means acceptable to the Regulatory staff for employing SNM doorway monitors to comply with that requirement.
Part 50, "Domestic Licensing of Production and Utilization Facilities" (Ref. 1), a combined license under
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." 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) 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)
 
RG 5.27, Rev. 1, Page 2  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 agency
's 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
Special nuclear material doorway monitors provide an efficient, sensitive, and reasonably unobtrusive means of searching individuals exiting from a material access area for concealed SNM. With proper installation and opera tion, gram quantities or less of SNM can be detected with a high level of reliability while maintaining a low false alarm rate.
-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 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 rat
 
====e. 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.
 
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 Knoll's, "Radiation Detection and Measurement." (Ref.7)   
RG 5.27, Rev. 1, Page 3  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 use


====d. Geiger====
I. Theory of Operation The doorway monitor is composed of a detector unit(s), associated electronics, and alarm logic. The detector unit(s) is sensitive to the radiations which emanate from the SNM and responds to these radiations (usually gamma rays) by generating current pulses. These pulses are amplified, filtered, and fed to alarm logic v'hich interprets the number (or rate) of pulses in some period of time, for example, one second. The alarm logic may be either a digital or analog system; in either case, if the number (or rate) of pulses exceeds a set level, an alarm condition ensues.
-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 o n 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 respons


====e. Helium====
2. General Characteristics Typically, the detectors of a doorway monitor are NaI(Tl) scintillators or solid or liquid organic scintilla tors. Geiger-Mueller detectors have also been used in this application, although the lower intrinsic efficiency of these detectors renders them less suitable than scintilla tion detectors.
-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.


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.
Detectors are arranged such 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; however, specific placement of detectors is usually dictated by the need to eliminate dead spots.


However, specific placement of detectors should be based on the need to eliminate areas of no detection
Some commercially available doorway monitors are equipped with an automatic background updating system. The automatic background updating system periodically monitors and averages the background. A  
.  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.  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
doorway monitor equipped with an automatic back ground updating system is also provided with a treadle pad or beam-break system to indicate that the sensitive area is occupied. When the sensitive area is occupied, the radiation level detected by the doorway monitor is compared with the mean backgroun
.1 Thus, the condition for an alarm can be written as
:      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.
====d. If the level is ====
"significantly" greater than the mean background, an alarm condition ensues. Significance is usually deter mined by comparing the radiation level when the sensitive area is occupied with the mean background plus some multiple of the square root of the mean back ground*
*The square root of the mean of a Poisson-distributed quantity is the unbiased estimate of the standard deviation of that quantity.


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
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.


1  The square root of the mean of a Poisson
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:
-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:
the guides will be acceptable if they provide a basis for the findings requisite to the imuance or ontinuance of a permit or license by the Commission.
    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 4  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
===1. Power Reactors ===
-throughput capability associated with processing many personnel through the detection system on a daily basis, walk
-through pedestrian monitors are the primary SNM 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
===6. Products ===
-held monitor is essential.  The operator must scan an individual in the correct way for a hand
2. Reaseerd enid Test Reactors
-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.


Radioisotope identification systems that detect radiation with high purity germanium (HPGe) detectors can be hand
===7. Transportation ===
-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
3. Fuels and Materials Facilities
-weight design useful as a hand held detection system.
8. Occupational Health Published guidas will be revised periodically, as appropriate, to accommodate
4. Environmental and Siting
9. Antitrust Review comments amd to refloct new informeaion or experience.


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.
5. Materials and Plant Protection
1


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.
===0. General===


Vehicle Monitors
Thus the condition for an alarm can be written as G > B + n, where B is the mean background, G is the radiation level with the sensitive area occupied, and n is a multiplier, usually an integer between 4 and 10.* The value of n directly affects the false alarm rate, and the combination of B and n affect the sensitivity.


Two types of automatic vehicle monitors presently in use are the vehicle monitoring station and the drive-through vehicle monitor. Commercially available vehicle drive
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 des cribed in the Regulatory Position.
-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 var y 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
Doorway monitors not equipped with an automatic background updating system either must rely on the inherent sensitivity of the instrument and low back ground variation to ensure that concealed SNM will be detected or must be attended so that a measurement of background can be taken immediately prior to use and the alarm level set to maintain the desired sensitivity to concealed SNM. As with the doorway monitor equipped with an automatic background updating system, a doorway monitor not so equipped compares the activity with the detection area occupied with some set value, usually the measurement of background taken just prior to use. In any case, the expression above can be used as a condition of alarm by replacing B + nr'Wwith the set level.


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:                                           
Whether or not a doorway monitor is equipped with an automatic background updating system, high back ground activity will decrease sensitivity. Measuring activ ity for longer periods will somewhat compensate for high background; however, longer measurement periods will make use of the doorway monitor less convenient.
    3  LA-UR-96-4505: "An Optimized International Vehicle Monitor," (Ref. 8)


RG 5.27, Rev. 1, Page 5  ASTM C1189
==C. REGULATORY POSITION==
-11, "Standard Guide to Procedures for Calibrating Automatic Pedestrian SNM Monitors." (Ref.
1. Minimum Qualifications for SNM Doorway Monitors  


9)    ASTM C1112
====a. General ====
-99 (2005), "Standard Guide for Application of Radiation Monitors to the Control and Physical Security of Special Nuclear Material." (Ref.
(1) SNM Doorway monitors should be used in conjunction with a metal detector and should be installed in a passageway (see Regulatory Guide 5.7,  
"Control of Personnel Access to Protected Areas, Vital
*Note that, in general, for a count rate system, the condition for afarm should be modified to account for the response time of the instrument as follows:
G > B + n1]0l - e-t/7)
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.


10)    ASTM C1237
Areas, and Material Access Areas,") in such a manner that objects cannot be passed over, around, or under the detection area.
-99 (2005), "Standard Guide to In
-Plant Performance Evaluation of Hand
-Held SNM Monitors." (Ref.


11)    ASTM C993-97 (2012), "Standard Guide for In
. (2) The detector elements should be designed and positioned so that detection sensitivity is as uniform as possible over the detection area; in no case should any areas where SNM is not detectible be permitted.
-Plant Performance Evaluation of Automatic Pedestrian SNM Monitors." (Ref. 1
2)     ASTM C1270
-97 (2012), "Standard Practice for Detection Sensitivity Mapping of In
-Plant Walk Through Metal Detectors." (Ref. 1
3)    ASTM C1269
-97 (2012), "Standard Practice for Adjusting the Operational Sensitivity Setting of In
-Plant Walk
-Through Metal Detectors." (Ref. 1
4)    ASTM C1309
-97 (2012), "Standard Practice for Performance Evaluation of In
-Plant Walk-Through Metal Detectors." (Ref. 1
5)    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.
(3) Power, sensitivity, and other controls of the doorway monitor should be tamper-safed when unat tended.


RG 5.27, Rev. 1, Page 6  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.
(4) Signal lines connecting alarm relays to the alarm monitor should be supervised.


These codes, standards and third party guidance documents may contain references to other codes, standards or third party guidance documents ("secondary references").
(5) Some doorway monitors may require an indi vidual to occupy the detection area for a specified time, longer than a normal walking pace would provide. If this is the case, the doorway monitor should be provided with a treadle pad and a "clock" device to assure that the detection area is occupied for the requisite time. An aural and visual indication should be given if an individual being searched does not occupy the area sufficiently long.
  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
b. System Specification
-binding requirement nor a "generic" NRC approval as an acceptable approach for meeting an NRC requirement.
(1) Plutonium-239. A doorway monitor used to detect plutonium should be capable of detecting a minimum of 0.5 gram of plutonium-239 encased in a minimum of 3 mm of brass at a 90% confidence limit.


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
The false alarm rate should be less than 0.1% (Appendix C).   
10 CFR 50.59.  C.  STAFF REGULATORY GUIDANCE
(2) Uranium-233. A doorway monitor used to detect uranium-233 should be capable of detecting within 4 hours of purification* a minimum of 1 gram of uranium-233 containing between 7 and 10 ppm of uranium-232 encased in a minimum of 3 mm of brass at a 90% confidence limit. The false alarm rate should be less than 0.1% (Appendix C). 
  1. Considerations for SNM Doorway Monitors a. General  (1) Metal detectors should be used in conjunction with an SNM doorway monitor as an SNM 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.
(3) Uranium-235. A doorway monitor used to detect uranium-235 should be capable of detecting a minimum of 3 grams of uranium-235 contained in uranium enriched to 20% or more in the uranium-235 isotope encased in a minimum of 3 mm of brass at a 50%
confidence limit. The false alarm rate should be less than
0.1% (Appendix C). 
2. Use of Doorway Monitors In general, doorway monitors should be used in locations of minimum background and minimum back ground fluctation. If circumstances dictate use of a doorway monitor in an area of high background, sufficient shielding should be provided to maintain 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
a. Attended Doorway Monitor
. (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.
(1) If the doorway monitor is attended during use, it need not be equipped with an automatic
*Purification means removal of all decay products.


(4) Power, sensitivity, and other controls of the doorway monitor and metal detector should be tamper-safe when unattended.
5.27-2


Doorway monitors and metal detectors that are secured behind locked and alarmed doors when unattended is an acceptable alternative measure to implementing tamper
background updating system, although such capability is preferred.
- 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
(2) Prior to each use* of a doorway monitor not equipped with an automatic background updating system, a measurement of background should be taken, and the alarm threshold should be set to the proper value listed in Table I for the measured background and the proper n value as determined in Appendix B. Each individual to be checked should, in turn, enter the detection area and be required to remain sufficiently long for the device to operate properly. During use, the background should be checked and the alarm threshold reset at least each 15 minutes.
detectors should be supervised electronically or by direct surveillance to detect tampering.


RG 5.27, Rev. 1, Page 7  (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
(3) With the individual being checked in the detection area, an alarm should sound if the activity in the detection area exceeds the alarm threshold T, as such a situation would indicate the presence of SNM.
-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
(4) The doorway monitor should be equipped with a high-background alarm which will sound if the measurement of background exceeds the appropriate maximum permissible background level listed in Table II
93 percent Pu
as determined in Appendix C. The doorway monitor should not be used during such periods of high back ground.
-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 cub


====e. The impact of Am====
b. Unattended Doorway Monitor
-241, a Pu decay product that will build up over time and emit increasing amounts of 60
(1) If the doorway monitor is unattended, an automatic background update system should be incor porated into the doorway monitor electronics and alarm logic. The control circuitry, if possible, should be located at the central alarm station (or other monitoring point).   
-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 rulecm 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
(2) Door interlocks and closed-circuit TV in combination with beam breaks, motion detectors, and/
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
or treadle pads, should be employed to:
-235 (U-235) should be capable of detecting highly enriched (i.e., 20
(a) Indicate to the person manning the central alarm station that an individual has entered the secure access passageway and/or is approaching the doorway monitor, (b) Allow observation of the individual ap proaching the doorway monitor, (c) Preclude a slow approach to the sensitive area of the doorway monitor, and
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
*By use is meant an individual or several individuals, each, in turn, being checked for SNM by the doorway monitor. The maximum period between threshold sets while the doorway monitor is in use is determined by the stability of local background and may necessarily be more frequent than every
. 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
15 minutes.
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 8  2. Operations with Doorway and Hand
(d) Activate the electronics and alarm logic when an individual is within the detection area and initiate operation of the doorway monitor.
-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
(3) An alarm should sound in the central alarm station if, when occupied, the activity in the detection area exceeds the internally set threshold level (the mean background plus some multiple times the square root of the mean background), as such a situation would indicate the presence of SNM upon the individual being checked.
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
(4) The doorway monitor should be equipped with a high-background alarm which will sound if the average background at the location of the doorway monitor exceeds the appropriate maximum permissible background level listed in Table II as determined in Appendix C. The doorway monitor should not be used during such periods of high background. Other moni tored exits should be used.
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.
3. Testing and Calibration a. Testing Doorway monitors should be tested by passing an appropriate source of the amount and isotope specified in Regulatory Position C.l.b. through the doorway monitor no less frequently than once per day.* In addition, a functional performance test should be carried out at least once per week. An acceptable functional performance test procedure is discussed in Appendix A
of this guide b. Calibration Doorway monitors should be calibrated with a source of the amount, configuration, and variety of SNM
to be detected (e.g., 0.5 gram Pu in 3 mm of brass). 
Calibration should be carried out according to a proce dure such as that in Appendix B.


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.
c. Operating Instructions Operating instructions should be posted near the doorway monitor,* if attended, or at the monitoring point if the doorway monitor is unattended. The instructions should clearly indicate the procedure for use of the doorway monitor and the procedure for setting thresholds, if appropriate. In addition, the operating instructions should indicate what corrective action is to be taken and who is to be notified in the event of a malfunction.


Doorway monitors should be attended at non
*Doorway monitors used to search for concealed U-233 should be tested according to §6 of Appendix A.
-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.
5.27-3


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


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
TABLE I (Cont'd)
-held monitor, as described in ASTM C1237
ALARM THRESHOLD
-99 (2005), (Ref. 11) to locate and identify the source of the signa
T
B
n =
4
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
4000
4200
4400
4600
4800
5000
5200
5400
5600
5800
6000
6200
6400
6600
6800
7000
7200
7400
7600
7800
8000
8200
8400
8600
8800
9000
9200
9400
9600
9800
1126
1339
1550
1760
1970
2179
2388
2596
2804
3012
3219
3426
3633
3840
4047
4253
4459
4665
4871
5077
5283
5483
5694
5899
6105
6310
6515
6720
6925
7130
7335
7539
7744
7949
8153
8358
8562
8767
8971
9175
9379
9584
9788
9992
10196
5
1158
1373
1587
1800
2012
2224
2435
2645
2855
3065
3274
3483
3692
3900
4108
4316
4524
4732
4939
5146
5354
5561
5767
5974
6181
6387
6594
6800
7006
7212
7418
7624
7830
8036
8242
8447
8653
8858
9064
9269
9474
9680
9885
10090
10295
5.27-5
9
6
1190
1408
1624
1840
2055
2268
2481
2694
2906
3117
3329
3539
3750
3960
4170
4379
4589
4798
5007
5216
5424
5633
5841
6049
6257
6465
6672
6880
7087
7295
7502
7709
7916
8123
8330
8537
8743
8950
9156
9363
9569
9775
9932
10188
10394
7
1221
1442
1662
1880
2097
2313
2528
2743
2957
3170
3383
3596
3808
4020
4232
4443
4654
4864
5075
5285
5495
5705
5914
6124
6333
6542
6751
6960
7169
7377
7586
7794
8002
8210
8418
8626
8834
9042
9249
9457
9664
9871
10079
10286
10493
8
1253
1477
1699
1920
2139
2358
2575
2792
3008
3223
3438
3653
3866
4080
4293
4506
4718
4931
5143
5354
5566
5777
5988
6199
6409
6620
6830
7040
7250
7460
7669
7879
8088
8297
8507
8716
8924
9133
9342
9550
9759
9967
10176
10384
10592
1285
1512
1737
1960
2182
2402
2622
2841
3059
3276
3493
3709
3925
4140
4355
4569
4783
4997
5210
5424
5636
5849
6061
6273
6485
6697
6909
7120
7331
7542
7753
7964
8174
8385
8595
8805
9015
9225
9435
9644
9854
10063
10273
10482
10691
1316
1546
1774
2000
2224
2447
2669
289C
3110
3329
3548
3766
3983
4200
4416
4632
4848
5063
5278
5493
5707
5921
6135
6348
6562
6775
6987
7200
7412
7625
7837
8049
8260
8472
8683
8894
9106
9317
9527
9738
9949
10159
10370
10580
10790


====l. If the hand====
TABLE II
-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.
MAXIMUM PERMISSIBL


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.
==E. BACKGROUND==
a = 0,  
Pa = 50%
B
n=
4
100
120
140
160
180.


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


RG 5.27, Rev. 1, Page 9  3.  Physical Searches and Training a. A physical search for concealed SNM should be conducted as necessary.
TABLE II
(Cont'd)
MAXIMUM PERMISSIBL


b. To enhance the probability of detection, random search es for concealed SNM at the protected area boundary may be conducted, including search es of hand-carried items.
==E. BACKGROUND==
B
G
n =
4
1000
1200
1400
1600
1000
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
4000
4200
4400
4600
4800
5000
5200
5400
5600
5800
6000
6200
6400
6600
6800
7000
7200
7400
7600
7800
8000
8200
8400
8600
8800
9000
9200
9400
9600
9800
881
1069
1258
1448
1638
1829
2020
2212
2404
2596
2789
29S2
3175
3368
3561
3755
3949
4143
4337
4531
4725
4919
5114
5309
5503
5698
5893
6088
6283
6478
6673
6868
7064
7259
7455
7650
7846
8041
8237
8433
8628
8824
9020
9216
9412
5
854
1039
1225
1412
1600
1789
1978
2167
2357
2548
2738
2929
3121
3312
3504
3696
3888
4081
4273
4466
4659
4852
5045
5238
5432
5625'
5819
6012
6206
6400
6594
6788
6982
7176
7371
7565
7760
7954
8149
8343
8538
8733
8928
9122
9317 a -'0,  
Pa = 50Z
6
827
1009
1193
1377
1563
1749
1936
2124
2312
2500
2689
2878
3068
3258
3448
3638
3829
4020
4211
4402
4593
4785
4977
5169
5361
5553
5745
5938
6130
6323
6516
6709
6902
7095
7288
7481
7674
7868
8061
8255
8449
8642
8836
9030
9224
7
802
981
1161
1343
1527
1710
1895
2081
2267
2453
2640
2828
3016
3204
3392
3581
3770
3960
4149
4339
4529
4719
4910
5100
5291
5482
5673
5864
6055
6247
6438
6630
6822
7014
7206
7398
7590
7782
7975
8167
8360
8553
8745
8938
9131
8
777
953
1131
1310
1491
1673
1855
2039
2223
2407
2593
2778
2964
3151
3338
3525
3713
3900
4088
4277
4465
4654
4843
5032
5222
5411
5601
5791
5981
6172
6362
6552
6743
6934
7125
7316
7507
7698
7889
8081
8272
8464
8656
8348
9039
5.27-7
9
753
926
1101
1278
1457
1636
1816
199D
2180
2363
2546
2730
2914
3099
3284
3470
3656
3842
4029
4216
4403
4590
4778
4966
5154
5342
5531
5719
5908
60'97
6286
6476
6665
6855
7045
7234
7425
7615
7805
7995
8186
8376
8567
8758
8949
10
730
900
1073
1247
1423
1600
1778
1958
2138
2318
2500
2682
2865
3048
3232
3416
3600
3785
3970
4155
4341
4527
4713
4900
5087
5274
5461
5648
5836
6024
6212
6400
6588
6777
6965
7154
7343
7532
7721
7911
8100
8290
8479
8669
8859


c. At facilities with formula quantities of strategic SNM, personnel having search duties and responsibilities must be trained and qualified
TABLE II
.(10 C FR 73.45(g)(1)(i)).
(Cont'd)
    Pedestrian in Monitoring Zone Sets Off Alarm at First and Second Pass Hand-Held Detector Search for Source Nuclide?SNM?Tactical Response by Security Release Pedestrian Release Pedestrian Document False Alarm for Later Investigation Yes No Yes No Document Type of Nuclide Detected Figure 1  Flow diagram for SNM searches
MAXIMUM PERMISSIBL


RG 5.27, Rev. 1, Page 10 4. Calibration, Testing, Maintenance, and Operating Instructions a. Calibration Doorway and hand
==E. BACKGROUND==
-held monitors should be calibrated with a source of the amount, configuration, and variety of SNM to be detecte
B
G
n
4
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
400
420
440
460
480
500
520
540
560
580
600
620
640
660
680
700
720
740
760
780
800
820
840
860
880
900
920
940
960
980
57
72
87
103
119
135
151
168
185
201
218
235
252
270
287
304
322
339
357
374
392
409
427
445
463
480
498
516
534
552
570
588
606
624
642
660
679
697
715
733
751
770
788
806
824
5  
51
65
80
95
110
126
141
157
173
189
206
222
239
255
272
289
306
323
340
357
374
391
409
426
443
461
478
496
513
531
549
566
584
602
619
637
655
673
690
708
726
744
762
780
798
6
46
59
73
87
102
117
132
147
163
178
194
210
226
242
258
275
291
308
324
341
357
374
391
408
425
442
459
476
493
511
528
545
562
580
597
614
632
649
667
684
702
720
737
755
773 S= 1.3, Pa = 90%
7
42
54
67
81
95
109
123
138
153
168
183
198
214
229
245
261
277
293
309
325
342
358
374
391
407
424
441
457
474
491
508
525
542
559
576
593
610
627
644
661
679
696
713
731
748
9
8
38
49
62
75
88
101
115
129
143
158
172
187
202
217
233
248
263
279
295
311
326
342
358
374
391
407
423
439
456
472
489
505
522
539
555
572
589
605
622
639
656
673
690
707
724
5.27-8
34
45
57
69
81
94
107
121
135
149
163
177
191
206
221
236
251
266
281
297
312
327
343
359
375
390
406
422
438
454
470
487
503
519
535
552
568
585
601
618
634
651
668
684
701
10
31
41
52
64
76 FS
100
113
127
1L0
154
167
181
196
210
224
22S
254
268
283
298
313
329
344
359
375
390
406
421
437
453
469
485
500
516
532
549
565
581
597
613
630
646
662
679


====d. Doorway and hand====
TABLE II
-held monitor calibration should be conducted in accordance with Reference
(Cont'd)
7 or as recommended by the manufacturer.  Calibration should be conducted before initial use and after monitor repair or maintenance.  Calibration should be conducted at least every three months.
MAXIMUM PERMISSIBL


As a quality assurance measure, consideration should be given to having SNM calibration standards traceable to certified reference standards or materials. b. Testing (1) Doorway , Hand-Held and Vehicle SNM Monitors Methods of performance testing doorway and hand
==E. BACKGROUND==
-held monitors are found within ASTM C993-97(2012), (Ref. 12) and Reference 9 (as well as reference
G
1 3).  The se 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.
n=
4
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
4000
4200
4400
4600
4800
5000
5200
5400
5600
5S00
6000
6200
6400
6600
6800
7000
7200
7400
7600
7800
8000
8200
8400
8600
8800
9000
9200
9400
9600
98-00
843
1027
1212
1398
1536
1773
1962
2151
2340
2530
2720
2911
3101
3292
3484
3675
3867
4059
4251
4443
4636
4828
5021
5214
5407
5600
5793
5987
6180
6373
6567
6761 r9955
7148
7342
7536
7731
7925
8119
3313
8508
8702
8897
9091
9286
5
816
997
1180
1363 it48
1734
1920
2107
2294
2482
2670
2859
3048
3238
3427
3617
3807
3998
4188
4379
4570
4761
4953
5144
5336
5528
5720
5912
6104
6296
6488
6681
6874
7066
7259
7452
7645
7838
8031
8225
8418
8611
8805
8998
9192
6
790
968
1148
1329
1512
1695
1879
2064
2249
2435
2622
2808
2996
3183
3371
3560
3748
3937
4126
4316
4505
4695
4885
5075
5266
5456
5647
5S38
6029
6220
6411
6602
6794
6985
7177
7369
7561
7753
7945
8137
8329
8521
8714
8906
9099
5.27-9 a = 1.3, P= = 90%
7
765
940
1117
1296
1476
1657
1839
2022
2205
2389
2574
2759
2944
3130
3317
3503
3691
3878
4066
4253
4442
4630
4819
5007
5196
5386
5575
5765
5954
6144
6334
6524
6715
6905
7096
7286
7477
7668
7859
8050
8241
8433
8624
8815
9007
8
741
913
1088
1264
1441
1620
1800
1980
2162
2344
2527
2710
2894
3078
3263
3448
3634
3319
4006
4192
4379
4566
4753
4940
5128
5316
5504
5692
5831
6070
6258
6447
6636
6826
7015
7205
7394
7584
7774
7964
8154
8345
8535
8725
8916
9
718
887
1059
1232
1407
1584
1761
1940
2119
2300
2481
2662
2844
3027
3210
3393
3577
3762
3946
4131
4317
4502
4688
4874
5061
5247
5434
5621
580G
5996
6184
6371
6559
6747
6936
7124
7313
7501
7690
7879
8063
8257
8447
8636
8826
10
695
861
1030
1201
1374
1548
1724
1900
2078
2256
2435
2615
2795
2976
3158
3340
3522
3705
3888
4072
4256
4440
4624
4809:
4994
5180
5365
5551
5737
5923
6110
6296
6483
6670
6857
7044
7232
7419
7607
7795
7983
8171
8360
8548
8737


Daily testing should be performe d during each shift, or once per day if there is only one shift. Reference 9 describes an acceptable approach for daily testing.
APPENDIX A
PROCEDURE FOR TESTING SNM DOORWAY MONITORS
FOR
FUNCTIONAL PERFORMANCE
Doorway monitors should be tested by employing a test source of the same isotope of SNM the doorway monitor is used to detect as follows:
1. With the detection area unoccupied, measure and record background.


As described in reference
2. Determine alarm threshold T from Table I (see Appendix B). 
9 and reference 1
3. Place a test source in the detection area of the doorway monitor. The test source should be such that the activity in the detection area slightly exceeds the T
1 , testing sources may be different than those used during calibration.
level.* The doorway monitor should go into an alarm condition if operating properly.


(2) Metal Detectors Sensitivity mapping and operational sensitivity testing methods are described within ASTM C1270
4. Remove test source to its original location and measure background once again. If the measurement of
-97 (2012), (Ref. 13), ASTM C1269-97 (2012), (Ref 14) and ASTM 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.  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
*The test source may be improvised by partially shielding the calibration source.


in references 1 3 , 1 4 and 1 5.  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.
background taken immediately after the test varies by more than 2vN
from the background taken before the test, the test should be repeated, for such a difference indicates nonrandom fluctuations of the background or equipment malfunction. The probability of such an occurrence due to the randomness of the background is less than 8%.   
5. A calibration source (Appendix B) should be carried repeatedly to various places within the detection area of the doorway monitor in simulation of actual use to verify that the SNM can be detected everywhere within the detection area and to assure proper operation of treadle pads, beam-break, or similar devices if the doorway monitor is so equipped.


Daily operability testing should be conducted once per shift, or at least daily.
6. Doorway monitors used to search for concealed uranium-233 should be tested with each uranium purification run, but no more frequently than daily. The test source should be freshly purified uranium-233 (within four hours of removal of decay products).
5.27-10


c. Maintenance Metal detection and SNM monitoring equipment shall be maintained to be operable and effectiv e as intended (10 CFR 73.20(4), 10 CFR 73.46(g), and
APPENDIX B
10 CFR 73.60(d)(1)). 
PROCEDURE FOR DETERMINING MAXIMUM PERMISSIBL
RG 5.27, Rev. 1, Page 11  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 (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==
==E. BACKGROUND==
The purpose of this section is to provide information on how applicants and licensees
Background should be measured over several work shifts to determine the setpoints for alarm threshold (with or without automatic background updating) to assure that normal operation will be minimally affected by alarms due to high background.
4 may use this guide and information regarding the NRC's 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 voluntarily
5 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.


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.   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
The doorway monitor should be calibrated with the amount of the appropriate isotope specified in Regula tory Positions C.l.b(1), (2), or (3) of this guide (e.g., 0.5 gram plutonium-239 in 3 mm of brass).   
The calibration procedure described below is essen tially a means of determining maximum permissible background for effective operation of the doorway monitor.


4  In this section, "licensees" refers to holders of, and the term "applicants" refers to applicants for, the following: (1) special nuclear material licenses under
1. Place a calibration source variously about the detec tion area and take readings to determine the least sensitive point. This location of minimum sensitivity should be maintained as the calibration point.
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.


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.
2. Measure background over several workshifts to deter mine the periods of high background and the range of background. A minimum of 20 measurements should be taken. The variance of the background is given by N
Var B N*-
1 (Bi-B)2 
(1)
where N is the number of measurements, B is the mean of the background measurements, and Bi is the ith background measurement.


RG 5.27, Rev. 1, Page 12  security plan such that NRC review may be required under the provisions of
3. With the calibration source at the calibration point, the mean gross counts G should be determined during a period of high background to establish the upper operating range of the doorway monitor. Table II lists various maximum permissible background levels for a given value of G for values of the parameters n and a.
10 CFR Part 50.54, 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.


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.
During periods when the background exceeds the value found from Table II, the sensitivity of the doorway monitor will generally be below that specified as minimum in Regulatory Position C.l.b of this guide.


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 licensee's failure to comply with the positions in this RG constitutes a violation.
The parameter n is a function of the background variation and the permissible false alarm rate and is calculated from n >3.1 (var B) 1/2
(2)
Generally, n is taken as an integer. If n satisfies the above expression, the expected false alarm rate (Appen dix C) due to background fluctuations should be less than 0.1%. Larger values of n will decrease the expected false alarm rate; however, the maximum allowable background for a given G will also decrease.


If an existing licensee voluntarily seeks a license amendment or change and (1) the NRC staff's 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 staff's determination of the acceptability of the licensee's 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
4. For doorway monitors equipped with automatic background updating systems, the alarm threshold is Counts > B + nVii,
10 CFR 50.109(a)(1), 10 CFR 70.76(a)(1), or 10 CFR 76.76(a)(1)
(3)
or any applicable finality provisions in
where n should be derived from expression (2), and the instrument set accordingly.
10 CFR Part 52. 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).       
RG 5.27, Rev. 1, Page 13  REFERENCES
6 1. U.S. Code of Federal Regulations , "Domestic Licensing of Production and Utilization Facilities
," Part 50 (10
CFR 50), Title 10, "Energy."  2. 10 CFR 52 , "Licenses, Certifications, and Approvals for Nuclear Power Plants," Title 10, "Energy"    3. 10 CFR 76, "Physical Protection of Plants and Materials," Title 10, "Energy"    4. 10 CFR 73, "Certification of Gaseous Diffusion Plants," Title 10, "Energy"    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)  Accession No.


ML003739976
5. The high-background alarm should be set at the B
.  6. NRC, "Access Control Systems:  Technical Information for NRC Licensees," NUREG-1964, Washington, DC. (ML1115A078)
value given in Table II for the measured G and calculated n values.
  7. Knoll, Glenn F., "Radiation Detection and Measurement," 4th ed., John Wiley and Sons
7 , 20 10.  8. LA-UR-96-4505, "An Optimized International Vehicle Monitor," R. L. York, D. A. Close, and P. E. Fehlau, Los Alamos National Labs, Los Alamos, NM (1997).
8  9. American Society for Testing and Materials (ASTM)
C1189-11, "Standard Guide to Procedures for Calibrating Automatic Pedestrian SNM Monitors," West Conshohocken, PA.


9  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.
6. For doorway monitors not equipped with an auto matic background update, the value of n determined above should be employed in the use of the doorway monitor according to Regulatory Position C.2.a.


11. ASTM C1237
*The false alarm rate is estimated by the probability that an observation of a quantity distributed normally about some value X will exceed X by n(Std. deviation of X). The factor 3.1 limits the false alarm rate to 0.1%, while the factor (Var B/B) 1/2 compensates for observed deviations in the background distribution from Poisson.
-99(2005), "Standard Guide to In
-Plant Performance Evaluation of Hand
-Held SNM Monitors," West Conshohocken, PA.


12. ASTM C993-97(2012), "Standard Guide for In
5.27-11
-Plant Performance Evaluation of Automatic Pedestrian SNM Monitors," West Conshohocken, PA.


6  Publicly available NRC published documents are available electronically through the NRC Library on the NRC's public Web site at http://www.nrc.gov/reading
APPENDIX C
-rm/doc-collections/
DETECTION CONFIDENCE LIMITS, THRESHOLDS,  
and through the NRC's Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading
AND MAXIMUM PERMISSIBL
-rm/adams.html The documents can also be viewed online or printed for a fee in the NRC's 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
. 
7  Copies of this publication and, or current edition are available thru the Wiley website at: http://www.wiley.com/
  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


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
==E. BACKGROUND==
-2959; telephone 610
With a calibration source at the calibration point, the condition for an alarm is, in general, g> T = B + m/Va' B
-832-9585. Purchase information is available through the ASTM Web site at http://www.astm.org
(1)
.
where g is a single measurement of G (the mean radiation level with the source), B is the mean back ground, and m is some multiplier. The detection confidence limit is the probability that with the calibra iton source at the calibration point, any single determin ation of G will exceed a threshold T, i.e., the above inequality will be satisfied. For any given probability Pa.,  
RG 5.27, Rev. 1, Page 14  13. ASTM C1270
there exists a value a such that g > G-  
-97(2012), "Standard Practice for Detection Sensitivity Mapping of In
(2)  
-Plant Walk Through Metal Detectors," West Conshohocken, PA.
with a probability of Pa, where g is any single measure ment of the quantity G. Hence the condition for a detection confidence limit of Pais G - &
_-r*-G > T = B + m,,/'r B.


14. ASTM C1270
(3)  
-97(2012), "Standard Practice for Detection Sensitivity Mapping of In
For a given value of G, solving (3) gives the maximum permissible B at which the doorway monitor will detect the source with a confidence Pr- For Pa = 90%, a = 1.3, and for Pa = 50%, a = 0.
-Plant Walk Through Metal Detectors," West Conshohocken, PA.  15. ASTM C1269
-97(2012), "Standard Practice for Adjusting the Operational Sensitivity Setting of In-Plant Walk
-Through Metal Detectors," West Conshohocken, PA
  16. ASTM C1309
-97(2012), "Standard Practice for Performance Evaluation of In
-Plant Walk-Through Metal Detectors,"  West Conshohocken, PA
  17. ASTM C1236
-99(2005), "Standard Guide for In
-Plant Performance Evaluation of Automatic Vehicle SNM Monitors," (Withdrawn 2014) West Conshohocken, PA
  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  19. NRC, "Backfitting Guidelines,"
The condition for a false alarm* is written as b = B + j a-'"B> T
NUREG-1409 , Washington, DC. (ML032230247)
(4)
  20. NRC, "Management of Facility
where b is a single measurement without the source and  
-specific Backfitting and Information Collection
0 is a number corresponding to a false alarm probability P
," Management Directive 8.4, Washington, DC.


(ML12059A460)
====p. For P ====
= 0.1%, 0 = 3.1. Hence the necessary condition for maintaining a false alarm rate below Pp is b = B +
-"B
< B + m ar.


10  Copies of International Atomic Energy Agency (IAEA) documents may be obtained through their Web site: WWW.IAEA.Org/
(5)  
or by writing the International Atomic Energy Agency P.O. Box 100 Wagramer Strasse 5, A
However, the doorway monitor actually compares b with B + ni, hence the condition on n becomes orV
-1400 Vienna, Austria.  Telephone (+431) 2600
< rn'VaTr
-0, Fax (+431) 2600
= nvff
-7, or E-Mail at Official.Mail@IAEA.Org
(6)  
or n>0 ( Va B ) 1/2
(7)
In Table I threshold values of T were determined by substituting equation (6) into equation (3):
T = B + nv'r The values of B in Table II were then calculated for 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 -\\
*False alarm means an alarm condition generated by statistical fluctuations in the background radiation or by instabilities of the electronics which appear as background fluctuations when the detection area is occupied.


RG 5.27, Rev. 1, Page 15}}
5.27-12}}


{{RG-Nav}}
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Latest revision as of 02:07, 17 January 2025

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

Paragraph (b), "Exit Requirement," of § 73.60, "Ad ditional Requirements for the Physical Protection of Special Nuclear Material at Fixed Sites," of 10 CFR Part

73, "Physical Protection of Plants and Materials,"

requires that individuals exiting from material access areas be searched for concealed special nuclear material (SNM). This guide describes means acceptable to the Regulatory staff for employing SNM doorway monitors to comply with that requirement.

B. DISCUSSION

Special nuclear material doorway monitors provide an efficient, sensitive, and reasonably unobtrusive means of searching individuals exiting from a material access area for concealed SNM. With proper installation and opera tion, gram quantities or less of SNM can be detected with a high level of reliability while maintaining a low false alarm rate.

I. Theory of Operation The doorway monitor is composed of a detector unit(s), associated electronics, and alarm logic. The detector unit(s) is sensitive to the radiations which emanate from the SNM and responds to these radiations (usually gamma rays) by generating current pulses. These pulses are amplified, filtered, and fed to alarm logic v'hich interprets the number (or rate) of pulses in some period of time, for example, one second. The alarm logic may be either a digital or analog system; in either case, if the number (or rate) of pulses exceeds a set level, an alarm condition ensues.

2. General Characteristics Typically, the detectors of a doorway monitor are NaI(Tl) scintillators or solid or liquid organic scintilla tors. Geiger-Mueller detectors have also been used in this application, although the lower intrinsic efficiency of these detectors renders them less suitable than scintilla tion detectors.

Detectors are arranged such 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; however, specific placement of detectors is usually dictated by the need to eliminate dead spots.

Some commercially available doorway monitors are equipped with an automatic background updating system. The automatic background updating system periodically monitors and averages the background. A

doorway monitor equipped with an automatic back ground updating system is also provided with a treadle pad or beam-break system to indicate that the sensitive area is occupied. When the sensitive area is occupied, the radiation level detected by the doorway monitor is compared with the mean backgroun

d. If the level is

"significantly" greater than the mean background, an alarm condition ensues. Significance is usually deter mined by comparing the radiation level when the sensitive area is occupied with the mean background plus some multiple of the square root of the mean back ground*

  • The square root of the mean of a Poisson-distributed quantity is the unbiased estimate of the standard deviation of that 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 the imuance or ontinuance of a permit or license by the Commission.

1. Power Reactors

6. Products

2. Reaseerd enid Test Reactors

7. Transportation

3. Fuels and Materials Facilities

8. Occupational Health Published guidas will be revised periodically, as appropriate, 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 G > B + n, where B is the mean background, G is the radiation level with the sensitive area occupied, and n is a multiplier, usually an integer between 4 and 10.* The value of n directly affects the false alarm rate, and the combination of B and n affect the sensitivity.

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 des cribed in the Regulatory Position.

Doorway monitors not equipped with an automatic background updating system either must rely on the inherent sensitivity of the instrument and low back ground variation to ensure that concealed SNM will be detected or must be attended so that a measurement of background can be taken immediately prior to use and the alarm level set to maintain the desired sensitivity to concealed SNM. As with the doorway monitor equipped with an automatic background updating system, a doorway monitor not so equipped compares the activity with the detection area occupied with some set value, usually the measurement of background taken just prior to use. In any case, the expression above can be used as a condition of alarm by replacing B + nr'Wwith the set level.

Whether or not a doorway monitor is equipped with an automatic background updating system, high back ground activity will decrease sensitivity. Measuring activ ity for longer periods will somewhat compensate for high background; however, longer measurement periods will make use of the doorway monitor less convenient.

C. REGULATORY POSITION

1. Minimum Qualifications for SNM Doorway Monitors

a. General

(1) SNM Doorway monitors should be used in conjunction with a metal detector and should be installed in a passageway (see Regulatory Guide 5.7,

"Control of Personnel Access to Protected Areas, Vital

  • Note that, in general, for a count rate system, the condition for afarm should be modified to account for the response time of the instrument as follows:

G > B + n1]0l - e-t/7)

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.

Areas, and Material Access Areas,") in such a manner that objects cannot be passed over, around, or under the detection area.

. (2) The detector elements should be designed and positioned so that detection sensitivity is as uniform as possible over the detection area; in no case should any areas where SNM is not detectible be permitted.

(3) Power, sensitivity, and other controls of the doorway monitor should be tamper-safed when unat tended.

(4) Signal lines connecting alarm relays to the alarm monitor should be supervised.

(5) Some doorway monitors may require an indi vidual to occupy the detection area for a specified time, longer than a normal walking pace would provide. If this is the case, the doorway monitor should be provided with a treadle pad and a "clock" device to assure that the detection area is occupied for the requisite time. An aural and visual indication should be given if an individual being searched does not occupy the area sufficiently long.

b. System Specification

(1) Plutonium-239. A doorway monitor used to detect plutonium should be capable of detecting a minimum of 0.5 gram of plutonium-239 encased in a minimum of 3 mm of brass at a 90% confidence limit.

The false alarm rate should be less than 0.1% (Appendix C).

(2) Uranium-233. A doorway monitor used to detect uranium-233 should be capable of detecting 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 uranium-232 encased in a minimum of 3 mm of brass at a 90% confidence limit. The false alarm rate should be less than 0.1% (Appendix C).

(3) Uranium-235. A doorway monitor used to detect uranium-235 should be capable of detecting a minimum of 3 grams of uranium-235 contained in uranium enriched to 20% or more in the uranium-235 isotope encased in a minimum of 3 mm of brass at a 50%

confidence limit. The false alarm rate should be less than

0.1% (Appendix C).

2. Use of Doorway Monitors In general, doorway monitors should be used in locations of minimum background and minimum back ground fluctation. If circumstances dictate use of a doorway monitor in an area of high background, sufficient shielding should be provided to maintain necessary sensitivity.

a. Attended Doorway Monitor

(1) If the doorway monitor is attended during use, it need not be equipped with an automatic

  • Purification means removal of all decay products.

5.27-2

background updating system, although such capability is preferred.

(2) Prior to each use* of a doorway monitor not equipped with an automatic background updating system, a measurement of background should be taken, and the alarm threshold should be set to the proper value listed in Table I for the measured background and the proper n value as determined in Appendix B. Each individual to be checked should, in turn, enter the detection area and be required to remain sufficiently long for the device to operate properly. During use, the background should be checked and the alarm threshold reset at least each 15 minutes.

(3) With the individual being checked in the detection area, an alarm should sound if the activity in the detection area exceeds the alarm threshold T, as such a situation would indicate the presence of SNM.

(4) The doorway monitor should be equipped with a high-background alarm which will sound if the measurement of background exceeds the appropriate maximum permissible background level listed in Table II

as determined in Appendix C. The doorway monitor should not be used during such periods of high back ground.

b. Unattended Doorway Monitor

(1) If the doorway monitor is unattended, an automatic background update system should be incor porated into the doorway monitor electronics and alarm logic. The control circuitry, if possible, should be located at the central alarm station (or other monitoring point).

(2) Door interlocks and closed-circuit TV in combination with beam breaks, motion detectors, and/

or treadle pads, should be employed to:

(a) Indicate to the person manning the central alarm station that an individual has entered the secure access passageway and/or is approaching the doorway monitor, (b) Allow observation of the individual ap proaching the doorway monitor, (c) Preclude a slow approach to the sensitive area of the doorway monitor, and

  • By use is meant an individual or several individuals, each, in turn, being checked for SNM by the doorway monitor. The maximum period between threshold sets while the doorway monitor is in use is determined by the stability of local background and may necessarily be more frequent than every

15 minutes.

(d) Activate the electronics and alarm logic when an individual is within the detection area and initiate operation of the doorway monitor.

(3) An alarm should sound in the central alarm station if, when occupied, the activity in the detection area exceeds the internally set threshold level (the mean background plus some multiple times the square root of the mean background), as such a situation would indicate the presence of SNM upon the individual being checked.

(4) The doorway monitor should be equipped with a high-background alarm which will sound if the average background at the location of the doorway monitor exceeds the appropriate maximum permissible background level listed in Table II as determined in Appendix C. The doorway monitor should not be used during such periods of high background. Other moni tored exits should be used.

3. Testing and Calibration a. Testing Doorway monitors should be tested by passing an appropriate source of the amount and isotope specified in Regulatory Position C.l.b. through the doorway monitor no less frequently than once per day.* In addition, a functional performance test should be carried out at least once per week. An acceptable functional performance test procedure is discussed in Appendix A

of this guide b. Calibration Doorway monitors should be calibrated with a source of the amount, configuration, and variety of SNM

to be detected (e.g., 0.5 gram Pu in 3 mm of brass).

Calibration should be carried out according to a proce dure such as that in Appendix B.

c. Operating Instructions Operating instructions should be posted near the doorway monitor,* if attended, or at the monitoring point if the doorway monitor is unattended. The instructions should clearly indicate the procedure for use of the doorway monitor and the procedure for setting thresholds, if appropriate. In addition, the operating instructions should indicate what corrective action is to be taken and who is to be notified in the event of a malfunction.

  • Doorway monitors used to search for concealed U-233 should be tested according to §6 of Appendix A.

5.27-3

TABLE I

ALARM THRESHOLD

T

B

n=

4

5

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

520

540

560

580

600

620

640

660

680

700

720

740

760

780

800

820

840

860

880

900

920

940

960

980

6

140

164

.187

211

234

257

279

302

324

347

369

392

414

436

458

480

502

524

546

568

589

611

633

655

676

698

720

741

763

784

806

827

849

870

892

913

935

956

977

999

1020

1041

1063

1084

1105

5.27-4

7

8

150

175

199

223

247

271

294

317

341

364

387

409

432

455

477

500

522

545

567

590

612

634

656

678

700

722

744

766

788

810

832

854

876

898

920

941

963

985

1007

1028

1050

1072

1093

1115

1137

160

186

211

236

260

285

309

333

357

380

404

427

451

474

497

520

543

566

589

611

634

657

679

702

724

747

769

792

814

836

859

881

903

925

948

970

992

1014

1036

1058

1080

1102

1124

1146

1168

170

197

223

249

274

299

324

348

373

397

421

445

469

493

516

540

563

587

610

633

657

680

703

726

749

771

794

817

840

863

885

908

930

953

975

998

1020

1043

1065

1088

1110

1132

1155

1177

1199

180

208

235

261

287

313

339

364

389

414

439

463

488

512

536

560

584

608

632

655

679

702

726

749

773

796

819

842

866

889

912

935

958

981

1003

1026

1049

1072

1095

1117

1140

1163

1185

1208

1230

9

190

219

246

274

301

327

353

379

405

431

456

481

506

531

555

580

604

629

653

677

701

725

749

773

797

820

844

868

891

915

938

961

985

1008

1031

1055

1078

1101

1124

1147

1170

1193

1216

1239

1262

10

200

230

258

286

314

341

368

395

421

447

473

499

524

550

575

600

625

650

674

699

724

748

772

797

821

845

869

893

917

941

965

988

1012

1036

1059

1083

1106

1130

1153

1177

1200

1223

1247

1270

1293

TABLE I (Cont'd)

ALARM THRESHOLD

T

B

n =

4

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

4200

4400

4600

4800

5000

5200

5400

5600

5800

6000

6200

6400

6600

6800

7000

7200

7400

7600

7800

8000

8200

8400

8600

8800

9000

9200

9400

9600

9800

1126

1339

1550

1760

1970

2179

2388

2596

2804

3012

3219

3426

3633

3840

4047

4253

4459

4665

4871

5077

5283

5483

5694

5899

6105

6310

6515

6720

6925

7130

7335

7539

7744

7949

8153

8358

8562

8767

8971

9175

9379

9584

9788

9992

10196

5

1158

1373

1587

1800

2012

2224

2435

2645

2855

3065

3274

3483

3692

3900

4108

4316

4524

4732

4939

5146

5354

5561

5767

5974

6181

6387

6594

6800

7006

7212

7418

7624

7830

8036

8242

8447

8653

8858

9064

9269

9474

9680

9885

10090

10295

5.27-5

9

6

1190

1408

1624

1840

2055

2268

2481

2694

2906

3117

3329

3539

3750

3960

4170

4379

4589

4798

5007

5216

5424

5633

5841

6049

6257

6465

6672

6880

7087

7295

7502

7709

7916

8123

8330

8537

8743

8950

9156

9363

9569

9775

9932

10188

10394

7

1221

1442

1662

1880

2097

2313

2528

2743

2957

3170

3383

3596

3808

4020

4232

4443

4654

4864

5075

5285

5495

5705

5914

6124

6333

6542

6751

6960

7169

7377

7586

7794

8002

8210

8418

8626

8834

9042

9249

9457

9664

9871

10079

10286

10493

8

1253

1477

1699

1920

2139

2358

2575

2792

3008

3223

3438

3653

3866

4080

4293

4506

4718

4931

5143

5354

5566

5777

5988

6199

6409

6620

6830

7040

7250

7460

7669

7879

8088

8297

8507

8716

8924

9133

9342

9550

9759

9967

10176

10384

10592

1285

1512

1737

1960

2182

2402

2622

2841

3059

3276

3493

3709

3925

4140

4355

4569

4783

4997

5210

5424

5636

5849

6061

6273

6485

6697

6909

7120

7331

7542

7753

7964

8174

8385

8595

8805

9015

9225

9435

9644

9854

10063

10273

10482

10691

1316

1546

1774

2000

2224

2447

2669

289C

3110

3329

3548

3766

3983

4200

4416

4632

4848

5063

5278

5493

5707

5921

6135

6348

6562

6775

6987

7200

7412

7625

7837

8049

8260

8472

8683

8894

9106

9317

9527

9738

9949

10159

10370

10580

10790

TABLE II

MAXIMUM PERMISSIBL

E. BACKGROUND

a = 0,

Pa = 50%

B

n=

4

100

120

140

160

180.

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

520

540

560

580

600

620

640

660

680

700

720

740

760

780

800

820

840

860

880

900

920

940

960

980

5

67

83

100

117

134

151

168

186

203

221

238

256

274

292

310

328

346

364

382

400

418

436

455

473

491

510

528

546

565

583

602

620

639

657

676

695

713

732

750

769

788

806

825

844

863 G

61

76

92

108

124

141

157

174

191

208

225

242

259

277

294

312

329

347

365

382

400

418

436

454

471

489

507

525

543

562

580

598

616

634

652

671

689

707

725

744

762

780

799

817

835

6

55

70

85

100

116

131

147

163

180

196

213

229

246

263

280

297

314

331

348

365

383

400

417

435

452

470

488

505

523

541

558

576

594

612

629

647

665

683

701

719

737

755

773

791

809

5.27-6

7

50

64

78

93

107

123

138

153

169

185

201

217

233

249

266

282

299

316

332

349

366

383

400

417

434

451

468

486

503

520

538

555

573

590

607

625

643

660

678

695

713

731

748

766

784

9

10

8

46

59

72

86

100

114

129

144

159

174

190

205

221

237

253

269

285

301

317

334

350

367

383

400

417

433

450

467

484

501

518

535

552

569

586

603

621

638

655

673

690

707

725

742

760

42

54

67

80

93

107

121

135

150

165

179

194

210

225

240

256

272

287

303

319

335

351

367

384

400

416

433

449

466

482

499

516

532

549

566

583

600

617

633

650

667

685

702

719

736

38

50

62

74

87

100

113

127

141

155

170

184

199

214

229

244

259

274

290

305

321

337

352

368

384

400

416

432

448

464

481

497

513

530

546

563

579

596

613

629

646

663

679

696

713

TABLE II

(Cont'd)

MAXIMUM PERMISSIBL

E. BACKGROUND

B

G

n =

4

1000

1200

1400

1600

1000

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

4200

4400

4600

4800

5000

5200

5400

5600

5800

6000

6200

6400

6600

6800

7000

7200

7400

7600

7800

8000

8200

8400

8600

8800

9000

9200

9400

9600

9800

881

1069

1258

1448

1638

1829

2020

2212

2404

2596

2789

29S2

3175

3368

3561

3755

3949

4143

4337

4531

4725

4919

5114

5309

5503

5698

5893

6088

6283

6478

6673

6868

7064

7259

7455

7650

7846

8041

8237

8433

8628

8824

9020

9216

9412

5

854

1039

1225

1412

1600

1789

1978

2167

2357

2548

2738

2929

3121

3312

3504

3696

3888

4081

4273

4466

4659

4852

5045

5238

5432

5625'

5819

6012

6206

6400

6594

6788

6982

7176

7371

7565

7760

7954

8149

8343

8538

8733

8928

9122

9317 a -'0,

Pa = 50Z

6

827

1009

1193

1377

1563

1749

1936

2124

2312

2500

2689

2878

3068

3258

3448

3638

3829

4020

4211

4402

4593

4785

4977

5169

5361

5553

5745

5938

6130

6323

6516

6709

6902

7095

7288

7481

7674

7868

8061

8255

8449

8642

8836

9030

9224

7

802

981

1161

1343

1527

1710

1895

2081

2267

2453

2640

2828

3016

3204

3392

3581

3770

3960

4149

4339

4529

4719

4910

5100

5291

5482

5673

5864

6055

6247

6438

6630

6822

7014

7206

7398

7590

7782

7975

8167

8360

8553

8745

8938

9131

8

777

953

1131

1310

1491

1673

1855

2039

2223

2407

2593

2778

2964

3151

3338

3525

3713

3900

4088

4277

4465

4654

4843

5032

5222

5411

5601

5791

5981

6172

6362

6552

6743

6934

7125

7316

7507

7698

7889

8081

8272

8464

8656

8348

9039

5.27-7

9

753

926

1101

1278

1457

1636

1816

199D

2180

2363

2546

2730

2914

3099

3284

3470

3656

3842

4029

4216

4403

4590

4778

4966

5154

5342

5531

5719

5908

60'97

6286

6476

6665

6855

7045

7234

7425

7615

7805

7995

8186

8376

8567

8758

8949

10

730

900

1073

1247

1423

1600

1778

1958

2138

2318

2500

2682

2865

3048

3232

3416

3600

3785

3970

4155

4341

4527

4713

4900

5087

5274

5461

5648

5836

6024

6212

6400

6588

6777

6965

7154

7343

7532

7721

7911

8100

8290

8479

8669

8859

TABLE II

(Cont'd)

MAXIMUM PERMISSIBL

E. BACKGROUND

B

G

n

4

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

520

540

560

580

600

620

640

660

680

700

720

740

760

780

800

820

840

860

880

900

920

940

960

980

57

72

87

103

119

135

151

168

185

201

218

235

252

270

287

304

322

339

357

374

392

409

427

445

463

480

498

516

534

552

570

588

606

624

642

660

679

697

715

733

751

770

788

806

824

5

51

65

80

95

110

126

141

157

173

189

206

222

239

255

272

289

306

323

340

357

374

391

409

426

443

461

478

496

513

531

549

566

584

602

619

637

655

673

690

708

726

744

762

780

798

6

46

59

73

87

102

117

132

147

163

178

194

210

226

242

258

275

291

308

324

341

357

374

391

408

425

442

459

476

493

511

528

545

562

580

597

614

632

649

667

684

702

720

737

755

773 S= 1.3, Pa = 90%

7

42

54

67

81

95

109

123

138

153

168

183

198

214

229

245

261

277

293

309

325

342

358

374

391

407

424

441

457

474

491

508

525

542

559

576

593

610

627

644

661

679

696

713

731

748

9

8

38

49

62

75

88

101

115

129

143

158

172

187

202

217

233

248

263

279

295

311

326

342

358

374

391

407

423

439

456

472

489

505

522

539

555

572

589

605

622

639

656

673

690

707

724

5.27-8

34

45

57

69

81

94

107

121

135

149

163

177

191

206

221

236

251

266

281

297

312

327

343

359

375

390

406

422

438

454

470

487

503

519

535

552

568

585

601

618

634

651

668

684

701

10

31

41

52

64

76 FS

100

113

127

1L0

154

167

181

196

210

224

22S

254

268

283

298

313

329

344

359

375

390

406

421

437

453

469

485

500

516

532

549

565

581

597

613

630

646

662

679

TABLE II

(Cont'd)

MAXIMUM PERMISSIBL

E. BACKGROUND

G

n=

4

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

4200

4400

4600

4800

5000

5200

5400

5600

5S00

6000

6200

6400

6600

6800

7000

7200

7400

7600

7800

8000

8200

8400

8600

8800

9000

9200

9400

9600

98-00

843

1027

1212

1398

1536

1773

1962

2151

2340

2530

2720

2911

3101

3292

3484

3675

3867

4059

4251

4443

4636

4828

5021

5214

5407

5600

5793

5987

6180

6373

6567

6761 r9955

7148

7342

7536

7731

7925

8119

3313

8508

8702

8897

9091

9286

5

816

997

1180

1363 it48

1734

1920

2107

2294

2482

2670

2859

3048

3238

3427

3617

3807

3998

4188

4379

4570

4761

4953

5144

5336

5528

5720

5912

6104

6296

6488

6681

6874

7066

7259

7452

7645

7838

8031

8225

8418

8611

8805

8998

9192

6

790

968

1148

1329

1512

1695

1879

2064

2249

2435

2622

2808

2996

3183

3371

3560

3748

3937

4126

4316

4505

4695

4885

5075

5266

5456

5647

5S38

6029

6220

6411

6602

6794

6985

7177

7369

7561

7753

7945

8137

8329

8521

8714

8906

9099

5.27-9 a = 1.3, P= = 90%

7

765

940

1117

1296

1476

1657

1839

2022

2205

2389

2574

2759

2944

3130

3317

3503

3691

3878

4066

4253

4442

4630

4819

5007

5196

5386

5575

5765

5954

6144

6334

6524

6715

6905

7096

7286

7477

7668

7859

8050

8241

8433

8624

8815

9007

8

741

913

1088

1264

1441

1620

1800

1980

2162

2344

2527

2710

2894

3078

3263

3448

3634

3319

4006

4192

4379

4566

4753

4940

5128

5316

5504

5692

5831

6070

6258

6447

6636

6826

7015

7205

7394

7584

7774

7964

8154

8345

8535

8725

8916

9

718

887

1059

1232

1407

1584

1761

1940

2119

2300

2481

2662

2844

3027

3210

3393

3577

3762

3946

4131

4317

4502

4688

4874

5061

5247

5434

5621

580G

5996

6184

6371

6559

6747

6936

7124

7313

7501

7690

7879

8063

8257

8447

8636

8826

10

695

861

1030

1201

1374

1548

1724

1900

2078

2256

2435

2615

2795

2976

3158

3340

3522

3705

3888

4072

4256

4440

4624

4809:

4994

5180

5365

5551

5737

5923

6110

6296

6483

6670

6857

7044

7232

7419

7607

7795

7983

8171

8360

8548

8737

APPENDIX A

PROCEDURE FOR TESTING SNM DOORWAY MONITORS

FOR

FUNCTIONAL PERFORMANCE

Doorway monitors should be tested by employing a test source of the same isotope of SNM the doorway monitor is used to detect as follows:

1. With the detection area unoccupied, measure and record background.

2. Determine alarm threshold T from Table I (see Appendix B).

3. Place a test source in the detection area of the doorway monitor. The test source should be such that the activity in the detection area slightly exceeds the T

level.* The doorway monitor should go into an alarm condition if operating properly.

4. Remove test source to its original location and measure background once again. If the measurement of

  • The test source may be improvised by partially shielding the calibration source.

background taken immediately after the test varies by more than 2vN

from the background taken before the test, the test should be repeated, for such a difference indicates nonrandom fluctuations of the background or equipment malfunction. The probability of such an occurrence due to the randomness of the background is less than 8%.

5. A calibration source (Appendix B) should be carried repeatedly to various places within the detection area of the doorway monitor in simulation of actual use to verify that the SNM can be detected everywhere within the detection area and to assure proper operation of treadle pads, beam-break, or similar devices if the doorway monitor is so equipped.

6. Doorway monitors used to search for concealed uranium-233 should be tested with each uranium purification run, but no more frequently than daily. The test source should be freshly purified uranium-233 (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 shifts to determine the setpoints for alarm threshold (with or without automatic background updating) to assure that normal operation will be minimally affected by alarms due to high background.

The doorway monitor should be calibrated with the amount of the appropriate isotope specified in Regula tory Positions C.l.b(1), (2), or (3) of this guide (e.g., 0.5 gram plutonium-239 in 3 mm of brass).

The calibration procedure described below is essen tially a means of determining maximum permissible background for effective operation of the doorway monitor.

1. Place a calibration source variously about the detec tion area and take readings to determine the least sensitive point. This location of minimum sensitivity should be maintained as the calibration point.

2. Measure background over several workshifts to deter mine the periods of high background and the range of background. A minimum of 20 measurements should be taken. The variance of the background is given by N

Var B N*-

1 (Bi-B)2

(1)

where N is the number of measurements, B is the mean of the background measurements, and Bi is the ith background measurement.

3. With the calibration source at the calibration point, the mean gross counts G should be determined during a period of high background to establish the upper operating range of the doorway monitor. Table II lists various maximum permissible background levels for a given value of G for values of the parameters n and a.

During periods when the background exceeds the value found from Table II, the sensitivity of the doorway monitor will generally be below that specified as minimum in Regulatory Position C.l.b of this guide.

The parameter n is a function of the background variation and the permissible false alarm rate and is calculated from n >3.1 (var B) 1/2

(2)

Generally, n is taken as an integer. If n satisfies the above expression, the expected false alarm rate (Appen dix C) due to background fluctuations should be less than 0.1%. Larger values of n will decrease the expected false alarm rate; however, the maximum allowable background for a given G will also decrease.

4. For doorway monitors equipped with automatic background updating systems, the alarm threshold is Counts > B + nVii,

(3)

where n should be derived from expression (2), and the instrument set accordingly.

5. The high-background alarm should be set at the B

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

6. For doorway monitors not equipped with an auto matic background update, the value of n determined above should be employed in the use of the doorway monitor according to Regulatory Position C.2.a.

  • The false alarm rate is estimated by the probability that an observation of a quantity distributed normally about some value X will exceed X by n(Std. deviation of X). The factor 3.1 limits the false alarm rate to 0.1%, while the factor (Var B/B) 1/2 compensates for observed deviations in the 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 condition for an alarm is, in general, g> T = B + m/Va' B

(1)

where g is a single measurement of G (the mean radiation level with the source), B is the mean back ground, and m is some multiplier. The detection confidence limit is the probability that with the calibra iton source at the calibration point, any single determin ation of G will exceed a threshold T, i.e., the above inequality will be satisfied. For any given probability Pa.,

there exists a value a such that g > G-

(2)

with a probability of Pa, where g is any single measure ment of the quantity G. Hence the condition for a detection confidence limit of Pais G - &

_-r*-G > T = B + m,,/'r B.

(3)

For a given value of G, solving (3) gives the maximum permissible B at which the doorway monitor will detect the source with a confidence Pr- For Pa = 90%, a = 1.3, and for Pa = 50%, a = 0.

The condition for a false alarm* is written as b = B + j a-'"B> T

(4)

where b is a single measurement without the source and

0 is a number corresponding to a false alarm probability P

p. For P

= 0.1%, 0 = 3.1. Hence the necessary condition for maintaining a false alarm rate below Pp is b = B +

-"B

< B + m ar.

(5)

However, the doorway monitor actually compares b with B + ni, hence the condition on n becomes orV

< rn'VaTr

= nvff

(6)

or n>0 ( Va B ) 1/2

(7)

In Table I threshold values of T were determined by substituting equation (6) into equation (3):

T = B + nv'r The values of B in Table II were then calculated for 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 -\\

  • False alarm means an alarm condition generated by statistical fluctuations in the background radiation or by instabilities of the electronics which appear as background fluctuations when the detection area is occupied.

5.27-12


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