Regulatory Guide 8.14

Revison 1, Personnel Neutron Dosimeters.

ML13064A088
Person / Time
Issue date:	08/31/1977
From:	NRC/OSD, Office of Nuclear Regulatory Research
To:
References
RG-8.014, Rev 1
Download: ML13064A088 (3)

Revision I

U.S. NUCLEAR REGULATORY COMMISSION August 1977 REGULATORY GUOIDE

OFFICE OF STANDARDS DEVELOPMENT

REGULATORY GUIDE 8.14 PERSONNEL NEUTRON DOSIMETERS

A. INTRODUCTION

whole body dose of more than about 300 millirems in a quarter year. Many neutron dosimeters have dif- Section 20.202, "Personnel Monitoring," of 10 ficulty measuring neutron doses of this magnitude.

CFR Part 20, "Standards for Protection Against The problem is even more severe in a mixed radiation Radiation," requires that licensees supply personnel field where neutrons contribute only a portion of the monitoring equipment and require its use by specified 300 millirems. Thus the regulations may require per- individuals. This guide provides guidance acceptable sonnel monitoring when the neutron dose is less than to the NRC staff on the use of personnel neutron 300 millirems in a quarter, but the standard only re- dosimeters where exposure to neutrons occurs. quires the dosimeters to detect 300 millirems per quarter (paragraph 4.1 of the standard). This

B. DISCUSSION

problem is discussed in regulatory position C.I.

The American National Standards Institute has

C. REGULATORY POSITION

approved a standard entitled "Personnel Neutron ANSI N319-1976, "Personnel Neutron Dosi- Dosimeters. (Neutron Energies Less than 20 MeV)" meters (Neutron Energies Less than 20 MeV),"'

and designated ANSI N319-1976.' This standard provides guidance acceptable to the NRC staff on the gives performance criteria, use factors, and dosimetry use of personnel neutron dosimeters, as sup- system calibration criteria for neutron dosimetry plemented and modified below.

systems. Accuracy criteria are not included among the performance criteria, however. 1. When Neutron Dosimeters Should Be Worn This guide supplements the standard by adding an Neutron dosimeters should be worn whenever the accuracy requirement. The guide also provides sub- neutron dose equivalent is likely to exceed 300 mrem stitutes for certain of the standard's performance re- in a quarter (the minimum sensitivity required of a quirements because data from a test performed by the neutron dosimeter in paragraph 4.1 of the standard).

Battelle Pacific Northwest Laboratory showed that If personnel monitoring is required by §20.202 the requirements of the standard could not be met by because of the total radiation exposure but the NTA film or thermoluminescence dosimeter systems. neutron dose equivalent is not likely to exceed 300

A copy of the Battelle data is available by writing to mrem in a quarter, the following alternatives are ac- the Occupational Health Standards Branch, Office of ceptable with regard to personnel neutron dosimetry:

Standards Development, U.S. Nuclear Regulatory Commission, Washington, D.C. 20555. a. Using higher sensitivity dosimeters. The licensee may use a dosimeter with a sensitivity greater than One problem in neutron dosimetry is that neutron that required in the standard. Albedo neutron dosimeters are less sensitive than gamma dosimeters. dosimeters generally are believed to be more sensitive Section 20.202 of the NRC regulations requires per- than required by the standard. Film may be accep- sonnel monitoring if a worker is likely to receive a table if fading due to humidity can be controlled, if the neutron spectrum has a small proportion of

'Copies may be obtained from the American National Standards neutrons below the neutron energy threshold of the Institute, Inc., 1430 Broadway, New York, New York 10018. film (about 0.7 MeV), and if the tracks are counted

• Lines indicate substantive changes from previous issue. on a large area of film.

USNRC-REGULATORY GUIDES Comments shou!d be sent to the Secretary of the Commission, US. Nuclear Regs.

latory Commission, Washington, D.C. 20555, Attention: Docketing and Service Regulatory Guides are issued to describe and make available to the public methods rranch.

acceptable to the N RC staff of implementing specific Darts of the Commission's reeulatio-s, to delineate techniques used by the staff in evaluating specific ,"roblemns The guides are issued in the following ton broad divisions:

or Postut3ted accidents, or to provide guidance to applicants. Regulatory Guides arc not subslitutes for regulations, and compliance with them is not required. 1. Power Reactors 6. Products Methods and soiullons diflerent from those set out in the nuides will be accept. 2. Research and Test Reactors 7. Transportation able if they provide a basis for the findings requisite to the isruance or continuance 3. Fuels and Materials Facilities 8. Occupational Health of a permit or license by the Commission 4. Environmental end Siting

9. Antitrust Review

5. Materials and Plant Protection 10. General Comments and suggestions for improvements in these guides ar. encouireg*d* at all Requests for single copies of issued guides lwhich may be reoroduced) or for place- times; and guides will be revised, as appropriate, to accommodate cominents and rlent on an automatic dristribution fist tor single copies o! future guides in Specific to reflect new information or experience. This guide was revisad as a result of divisions should be made in writing to the US. Nuclear Regulatory Commission, substantive comment; receved from the Public and additional staff revyew. Washington. D.C. 20555, Attention: Director, Division of Document Control.

b. Calculated neutron dose equivalent to supplement normal background in mrems for a single reading."

neutron dosimeter. A licensee may use a personnel (This definition of LLD was chosen to be consistent neutron dosimeter but may substitute a calculated with the NRC position previously stated in Tables 1 neutron dose equivalent for the measured dose and 3 of Regulatory Guide 4.8, "Environmental equivalent if the measured dose equivalent cannot be Technical Specifications for Nuclear Power Plants."

reliably determined because of the lack of sensitivity The basis for the definition is given in USERDA

of the dosimeter. Calculated dose equivalents may be report HASL-300, p. D-08-01.)

based on measured neutron/gamma ratios or on Instead of the 10% limit on the standard deviation neutron dose equivalents measured with portable or in paragraph 4.4 of the standard on precision, a limit fixed monitoring instruments and known personnel of 30% should be used.

occupancy times. More information on determining neutron dose equivalents by neutron/gamma ratios is The following accuracy requirement should be ad- given in Regulatory Guide 8.4, "Direct-Reading and ded: "When exposed to an unmoderated californium- indirect-Reading Pocket Dosimeters." 252 source; the average accuracy of a set of 10

dosimeters exposed in the range from 100 mrems to 3 c. Calculated neutron dose equivalent in place of rems should be +/-50%."

neutron dosimeter. If the individual is not likely to receive a neutron dose equivalent in excess of 100 The tests necessary to verify that the dosimetry mrem in a quarter but wouid still have to have some system meets the requirements in the standard may sort of monitoring under §20.202 (e.g., gamma be performed by the licensee or by someone selected monitoring), a personnel neutron dosimeter may be by him. The tests may be performed on a system just omitted. The neutron dose equivalent should then be once to demonstrate that it can meet the require- estimated by the methods in regulatory position ments of Section 4 of the standard.

C.L.b above. This procedure is discussed in more detail in regulatory position C.3 of Regulatory Guide In the case of film, each different type of packaging

8.4. should be considered a different system to be tested separately. Tests should also be repeated any time d. Neutron dose equivalent much smaller than gam- changes are made in the dosimetry system (i.e.,

ma dose equivalent. If the neutron whole body dose processing the dosimeters differently). A licensee fol- equivalent is not likely to exceed 10% of the gamma lowing the recommendations of this guide should plus x-ray dose equivalent, neutron dosimeters may maintain records to show that his neutron dosimeters be omitted and the neutron dose equivalent may be have been tested and meet the perforrriance require- assumed equal to zero. ments of Section 4 of the standard.

e. Negligible neutron dose equivalent. If the 3. Meeting the Fading Requirements of the Standard.

neutron dose equivalent is not likely to exceed 30 To meet the fading requirements in paragraphs 5.3 mrem per quarter, or 10 mrem per quarter for in- and 5.4 of the standard, the licensee should irradiate dividuals under 18 years of age, neutron dosimeters four dosimeters with a neutron dose equivalent of at may be omitted and the neutron dose equivalent as- least 0.5 rem. The dosimeters should then be stored sumed equal to zero. The determination that an in- for an entire dosimeter exchange period at a humidity dividual is not likely to receive a neutron dose similar to that expected in normal use. The equivalent of 30 mrem per quarter should not be dosimeters should then be read to verify that, on the based on previous NTA film badge readings since average, they meet the fading criterion (paragraph 5.3 NTA film is not suffficiently sensitive to detect this of the standard). If humidity is a significant cause of dose equivalent rate. fading, the test should be performed during a period

2. Performance Requirements of high humidity.

Section 4 of the standard contains -several perfor- mance requirements on the dosimetry system. 4. Dosimetry System Calibration Instead of paragraph 4.1 of the standard on lower Section 6 of the standard gives suggestions on limit of detection, the following should be used: dosimetry system calibration. Calibration of dosimeter response may. be performed by the ex-

"The lower limit of detection of the dosimetry posure of the dosimeter and a reference monitoring system shall not exceed 300 mrem per quarter. The instrument in the actual locations where significant quarterly lower limit of detection (LLD) in mrems at neutron exposure occurs. The spherical (Hankins)

the 95% confidence level is defined as "rem-meter," the Anderson-Braun rem counter, or other similar instruments may be -used as reference LLD = 4.66/s S

monitoring instruments. These monitoring instruý

where N is the number of dosimetry exchange periods ments should be calibrated by sources whose calibra- in a quarter and S is the standard deviation of the tion is traceable to the National Bureau of Standards. I

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Calibrations of dosimeter response may also be

D. IMPLEMENTATION

performed by the dosimeter processor. The processor should use a calibration factor applicable to the dose The purpose of this section is to provide informa- spectrum delivered to the individuals wearing the tion to applicants regarding the NRC staff's plans for dosimeters. The calibration may be performed by the using this regulatory guide.

licensee or by someone selected by him, and records describing the dosimeter calibration should be main- Except in those cases in which the applicant tained by the licensee. The dosimeter calibration proposes an acceptable alternative method for com- should be repeated any time the licensee has reason to plying with §20.202 of the Commission's regulations, believe the neutron spectrum has changed and the the method herein will be used in the evaluation of previous calibration might not be valid. submittals in connection with license applications

5. Maintaining Body Contact docketed after November 1, 1977.

Albedo neutron systems usually require close body If an applicant wishes to use this regulatory guide contact at all times during usage. Sizable errors can in developing submittals for applications docketed on occur if close body contact is not maintained. Albedo or before November 1, 1977, the pertinent portions of neutron dosimeters should have a means to maintain the application will be evaluated on the basis of this this necessary close contact with the body. guide.

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