ANSI HPS N13.37-2014 Environmental Dosimetry - Criteria for System Design and Implementation.pdf

1、 American National Standard ANSI/HPS N13.37-2014 Environmental Dosimetry Criteria for System Design and Implementation Approved April 8, 2014 American National Standards Institute, Inc. Published by Health Physics Society 1313 Dolley Madison Blvd. Suite 402 McLean, VA 22101 Copyright 2014 by the Hea

2、lth Physics Society. All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher. Printed in the United States of America ANSI/HPS N13.37-2014 The ANSI/HPS N13.37 working group respo

3、nsible for the development of this standard had the following members and consultant: Gladys A. Klemic, Chair U.S. Department of Homeland Security Steven Garry U.S. Nuclear Regulatory Commission Wayne M. Glines Dade Moeller Section 7.2 addresses these types of errors. Keywords: environmental radiati

4、on, environmental monitoring, thermoluminescence dosimetry, TLD, optically stimulated luminescence, OSL, passive dosimeters, facility monitoring, external dosimetry AMERICAN NATIONAL STANDARD ANSI/HPS N13.37-2014 1 Environmental DosimetryCriteria for System Design and Implementation 1.0 Purpose and

5、Scope 1.1 Purpose This standard provides performance test methods and criteria for system design and implementation of environmental radiation dosimetry systems used to measure exter-nal photon radiation. 1.2 Scope This standard is applicable to passive envi-ronmental dosimetry systems used to moni-

6、tor areas surrounding radiological facilities to assess potential facility-related radiation doses and to verify compliance with public dose limits. Such environmental dosimetry systems include dosimeters which accumu-late radiation dose and any readout device required to process the dosimeters. Pas

7、sive dosimeters include thermoluminescence dosimeters (TLDs), optically stimulated lu-minescence (OSL) dosimeters, and direct ion-storage dosimeters, which are deployed at field locations around a facility and ex-changed periodically (e.g., quarterly). Dosimeters could be processed at the facility o

8、r off-site. Sections 1 through 4 of this standard cover the overview, definitions, general considera-tions and a summary of requirements and recommendations. Sections 5 and 6 de-scribe laboratory type tests to determine the fundamental performance characteristics of a specified dosimetry system desi

9、gn and establish criteria that will enable a level of bias and precision in field measurements suitable for quantifying the radiological im-pact of facility operations on members of the public and the surrounding environment. Section 7 of this standard provides imple-mentation performance objectives

10、, require-ments, and recommendations for field measurements using a dosimetry system that has satisfied the performance criteria in Section 5 and 6. Establishing conformance with this standard requires fully documenting the system de-sign. The system design is defined to in-clude the dosimeters, rea

11、dout equipment and other processing hardware as well as the equipment configuration, operating/pro-cessing procedures, and dose calculation methods used for type testing. All of these play a significant role in determining system performance.1 If a specific documented sys-tem design has been tested

12、and shown to meet the performance criteria in Sections 5 and 6, then the test results are applicable to any processor implementing the same sys-tem design. It is important to note that the type tests in Sections 5 and 6 are not intended as tests of a particular processor but rather as tests of a spe

13、cific system design. Some manufac-turers may offer turn-key systems (hardware and software) and recommended operating procedures that have been optimized for environmental monitoring. Others offer sys-tems with flexibility in configuration and op-eration that allow the processor to design a system t

14、ailored to their needs. It is ultimately the processor who determines the final sys-tem design that is implemented and which is the subject of the type tests in this stand-ard.2 It is recognized that the end user must sometimes take certain actions that alter the system design that has been tested (

15、e.g., additional dosimeter packaging or field 1 For example, with TLD and OSL systems, depending on the particular detector material used, the pre-irradiation anneal treatment and readout protocols (e.g., time-temperature profile for TLD, or optical stimulation wavelength, power, and duration for OS

16、L) can significantly impact the sensitivity, reproducibility, and minimum quantifiable dose for a system, as well as the fading characteristics of the system. The dose calculation algorithms used can significantly influence the angular and energy dependence of dose results. Because routine dose calc

17、ulation methods are called for in many of the type tests, details of those methods shall be included in the documentation of the system design that is tested. 2 The distinctions between manufacturer and processor and processor and end user are not always clear. In some cases, the manufacturer and pr

18、ocessor may be one and the same, or have a close working relationship. In other cases (e.g., “in-house” dosimetry programs) the processor and end user may be one and the same, or have a close working relationship. The term “processor” is used generically here to refer to the laboratory in which dosi

19、meters are prepared and processed (i.e., readout and results reported to end user). ANSI/HPS N13.37-2014 2 mounting hardware). When this is the case, the end user shall document that those changes have not altered the basic performance characteristics that were determined in the type tests. 2.0 Defi

20、nitions Air kerma (Ka): The quotient of dEtr by dm, where dEtr is the sum of the initial kinetic energies of all the charged particles (e.g., electrons) liberated by uncharged particles (e.g., photons) in mass, dm, of air at a point of interest in air, thus: Ka = dEtr/dm (1) Note 1: The Internationa

21、l System (SI) unit for air kerma is joules per kilogram (J kg-1). The special name for this unit of air kerma is gray (Gy) where 1 Gy = 1 J kg-1. Note 2: The traditional unit of air kerma is ergs per gram (ergs g-1). The name for this unit of air kerma is rad where 1 rad = 100 ergs g-1 (1 rad = 10-2

22、 Gy). Ambient dose equivalent H*(d): The dose equivalent at a point in a radiation field that would be produced by the corresponding expanded and aligned field, in the International Commission on Radiation Units and Measurements (ICRU) sphere at a depth, d, on the radius opposing the direction of th

23、e aligned field 1. Note 1: Dose equivalent is the product of D and Q at a point in a given mass, where D is the absorbed dose and Q is the quality factor at that point, thus H = DQ (2) Note 2: The SI unit for dose equivalent (and ambient dose equivalent) is joule per kilogram (J kg-1). The special n

24、ame for this unit of dose equivalent is sievert (Sv) where 1 Sv = 1 J kg-1. Note 3: The traditional unit of dose equivalent (and ambient dose equivalent) is ergs per gram (ergs g-1). The name for this unit of dose equivalent is rem where 1 rem = 100 ergs g-1. (1 rem = 10-2 Sv) Note 4: The recommende

25、d value of d for strongly penetrating radiation is 10 mm. Assessment: A review, evaluation, inspection, test, check, surveillance, or audit to determine and document whether items, processes, systems, or services meet specific requirements and are performing effectively. Background radiation: Radiat

26、ion from naturally occurring radioactive materials which have not been technologically enhanced (i.e., not increased by or as a result of past or present human practices above levels encountered in the natural state). Background radiation also includes radiation from the following: 1. Cosmic and ter

27、restrial sources. 2. Global fallout as it exists in the environment (such as from the testing of nuclear explosive devices or from past nuclear accidents which have a global impact e.g., Chernobyl). 3. Radon and its progeny in concentrations or levels existing in buildings or the environment which h

28、ave not been technologically enhanced or elevated as a result of current or prior human activities. 4. Consumer products containing nominal amounts of radioactive material or producing nominal amounts of radiation. Baseline background dose (BQ or BA): The estimated mean background radiation dose at

29、each field monitoring location in a specified time period (e.g., quarterly BQ or annually BA) based on historical measurements, excluding any dose contribution from the monitored facility. Bias: The mean deviation from the conventionally true value, expressed as a fraction of the conventionally true

30、 value, that remains constant over replicated measurements within the statistical precision of the measurement. Note: Also referred to as deterministic error, fixed error, and systematic error. Coefficient of determination (R2): The measure of the proportion of the variance accounted for by an indep

31、endent variable in predicting the dependent variable. The greater the coefficient, the more account is ANSI/HPS N13.37-2014 3 taken for the variance. It can range from 0 to 1, and is calculated as follows: R2 = 1 explained variationtotal variation = 1 ( est)2()2 (3) where Y are the observed values f

32、or the dependent variable, is the mean of these observed values, and Yest are the predicted or estimated values of the dependent variable. When used in linear regression, the better the linear regression fits the data, the closer the value of R2 is to one. Coefficient of variation (CV): The quotient

33、 of the estimated standard deviation of a series of measurements, x1, x2, . . .xi, . . . xN, of a variable divided by the mean value, , of the measurements; or, for a single measurement, the quotient of the estimate of the standard deviation divided by the value of the single measurement. CV = 1 1(1

34、) ( )2=1 (4) where = 1 =1 (5) Note: Sometimes expressed as a percentage; i.e., value of coefficient of variation multiplied by 100. Control dosimeter: A dosimeter that accompanies a field dosimeter to account for extraneous dose received before or after field deployment, such as during transit from

35、and to a dosimeter processor, and/or to and from the field location. Conventionally true value (D): The best estimate of the delivered radiation dose, determined by (1) a primary standard, (2) a transfer standard that is traceable to a primary standard, or (3) a reference instrument that has been ca

36、librated against a primary or a transfer standard. Coverage factor: A numerical factor used as a multiplier of the combined standard uncertainty in order to obtain an expanded uncertainty. Note 1: A coverage factor is typically in the range 2 to 3. Note 2: In case of a normal distribution, using a c

37、overage factor of 2 results in an expanded uncertainty that defines an interval around the result of a measurement that contains approximately 95% of the distribution of values that could reasonably be attributed to the measurand. For other distributions, the coverage factor may be larger. Detector:

38、 The radiation sensitive component or material which can be processed to provide a numerical measure of the incident radiation dose, such as an individual TLD element. See definition for dosimeter. Directional dose equivalent H (d, ): The dose equivalent at a point in a radiation field that would be

39、 produced by the corresponding expanded field, in the ICRU sphere at a depth, d, on a radius in a specified direction, . Note 1: The units and names of units for directional dose equivalent are the same as for ambient dose equivalent. Note 2: The recommended value of d for weakly penetrating radiati

40、on is 0.07 mm. Note 3: When not specified, is assumed to be zero degrees or of normal incidence. Dose (radiation dose): A generic term that means absorbed dose, dose equivalent, ambient dose equivalent, or directional dose equivalent, dependent upon context, as defined elsewhere in this standard. Do

41、simeter: Device consisting of one or more detectors, which can be mounted in one or more holders functioning as a single unit (appropriate for the application), intended to be placed in a location in the environment for the purpose of measuring ambient dose equivalent at the location where it is pla

42、ced. Dosimetry system: The dosimeters, related data collection and processing instruments, and techniques required to evaluate the dose received by environmental dosimeters. End user: The entity that uses the dosimeters for environmental monitoring purposes, including field deployment and ANSI/HPS N

43、13.37-2014 4 collection of dosimeters. Where processing is done off-site, the end user also handles receipt of dosimeters from and submission back to the processor. Environmental monitoring: The measurement of external photon dose using field dosimeters positioned at fixed outdoor locations. Exposur

44、e (X): Exposure, X, is the quotient of dQ by dm where dQ is the absolute value of the total charge of the ions of one sign produced in air when all of the electrons and positrons liberated or created by photons in air of mass dm are completely stopped in air. The SI unit of exposure is C kg-1 and th

45、e traditional unit is the roentgen (R) with the conversion of 1 R = 2.58 10-4 C kg-1. Air kerma, Ka, has replaced exposure as the reference quantity used to establish traceability to the U.S. National Institute of Standards and Technology (NIST). Extraneous dose: The dose accumulated on a dosimeter

46、prior to and after field deployment from radiation other than that at the field monitoring location. The extraneous dose includes any dose received during transit to or at the monitored facility; e.g., natural terrestrial background radiation, cosmic sources, elevated dose from transport at high alt

47、itudes, any manmade sources potentially encountered in transit or at the facility, such as shipments of medical or other radioisotopes or facility sources. The extraneous dose is subtracted from the field dosimeter reading in order to determine the field dose. Facility-related dose (FQ or FA): The d

48、ose received by a field dosimeter at a monitoring location due to radiation from the monitored facility. Facility-related dose excludes the background radiation dose, which is estimated by use of the baseline background dose. The facility-related dose can be calculated for those monitoring locations

49、 where the normalized quarterly field doses MQ (or normalized annual dose MA) exceed the baseline background dose by more than the quarterly minimum differential dose (MDDQ) (or annual MDDA) as follows. Quarterly facility-related dose (FQ): If MQ (BQ+MDDQ) then FQ = MQ BQ If MQ (BQ+MDDQ) then FQ = not detected Annual facility-related dose (FA): If MA (BA + MDDA) then FA = MA BA If MA (BA + MDDA) then FA = not detected Field dosimeter: A dosimeter designated for deployment at a field monitoring loc