ANSI HPS N13.3-2013 Dosimetry for Criticality Accidents.pdf

1、 American National Standard ANSI/HPS N13.3-2013 Dosimetry for Criticality Accidents Approved December 20, 2013 American National Standards Institute, Inc. Published by Health Physics Society 1313 Dolley Madison Blvd. Suite 402 McLean, VA 22101 Copyright 2013 by the Health Physics Society. All rights

2、 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 N13.3-2013 iii The ANSI/HPS N13.3 Working Group responsible for this standard had

3、the following members: Dann C. Ward, Chairperson Sandia National Laboratories Milan Gadd Los Alamos National Laboratory David Hickman Lawrence Livermore National Laboratory David Heinrichs Lawrence Livermore National Laboratory Andrew Wysong Lawrence Livermore National Laboratory Ken Veinot Y-12 Nat

4、ional Security Complex Ken Crase Savannah River SiteRetired Robin Hill Dade Moeller thus = dN/dA. The unit of fluence is m-2. Kerma (K): The kerma is the quotient of dEtr by dm, where dEtr is the sum of the initial kinetic energies of all the charged particles liberated by uncharged particles in a m

5、ass of dm of material, thus K = dEtr/dm. Kerma is often used as an approximation of the ab-sorbed dose. The unit of kerma is joule per kilogram (J kg-1) and has the special unit Gy in SI or rad in traditional units. Personal Absorbed Dose Dp(10): The absorbed dose in soft tissue at a depth of 10 mm

6、below a specified point in the body. The unit of personal absorbed dose is Gy in SI or rad in the traditional units. Personnel Nuclear Accident Dosimeter (PNAD): One or more detectors worn on the body to provide information following a criti-cality accident that can be used to measure the level of r

7、adiation dose received by an individual. ANSI/HPS N13.3-2013 3 Quick Sort: An initial sorting method, typically using portable radiation survey instrumentation and measureable levels of activated materials to identify criticality exposed individuals. Total Absorbed Dose: In mixed neutron and photon

8、radiation fields, the total absorbed dose is the sum of the absorbed doses resulting from incident neutron and photon radiations. In this standard the following definitions apply. The word shall is used to denote a requirement. The word should is used to denote a recommendation. The word may denotes

9、 something that is permitted or allowable but is neither a requirement nor a recommendation. 4.0 Basic Requirements A criticality accident dosimetry system, henceforth referred to as a system, shall be established for areas and operations where there is a potential for a criticality accident. In gen

10、eral, the system should be established for operations for which criticality safety controls and criticality alarm systems are employed (ANSI 2007). Systems may consist of a combination of one or more of the following components and the associated data collection and processing instruments and techni

11、ques: personnel dosimeters, dosimeters deployed in fixed facility locations, biological materials, and mathematical models. The extent and complexity of the system should be commensurate with the nature of operations. System design should address identification and assessment of doses to organs or e

12、xtremities for cases of partial-body or non-uniform dose distributions. Provisions of this standard are meant to apply to any criticality accident dosimetry system used to determine the dose to individuals due to a criticality accident. 4.1 Application of System The system shall be capable of achiev

13、ing the following performance requirements. 4.1.1 Rapid Identification of Exposed Individuals. A quick sort process shall be able to identify exposed individuals with total absorbed doses exceeding 0.5 Gy (50 rad) and sort exposed individuals by estimated dose level during the initial response to th

14、e accident. This sort process should be initiated upon individual exit from the area where there is the potential for additional dose from the criticality. The purpose of this sort is to identify individuals requiring medical treatment and guide that treatment, prioritize additional dosimeter proces

15、sing, and identify the need for additional measurements. 4.1.2 Preliminary Total Absorbed Dose Information. Preliminary total absorbed dose information (neutron plus photon) shall be provided within 24 hours of dosimeter retrieval and may be revised as more information becomes available. Preliminary

16、 doses are primarily intended to guide the follow-on treatment of exposed individuals. 4.1.3 Minimum Throughput of Dosimeters. The system shall be capable of providing a predetermined minimum throughput of preliminary total absorbed dose determinations for the anticipated number of significantly exp

17、osed individuals based on facility design, work practices, and criteria in Sections 4.1.1 and 4.1.2. Throughput considerations shall be documented in the system technical basis documentation (STBD). 4.2 System Design 4.2.1 Documentation. The system design shall be documented including the system com

18、ponents, technical basis, proper applica-tion, and limitations. 4.2.2 Neutron Fluence and Dose. The sys-tem shall be capable of evaluating total neu-tron dose in the range of neutron energies of concern. The system should be capable of evaluating neutron fluence in the range of energies of concern.

19、The range of energies of concern shall be defined in the STBD. 4.2.3 Analytical Techniques and Instru-mentation. Analytical techniques and in-strumentation necessary to perform system ANSI/HPS N13.3-2013 4 functions shall be documented, maintained, and readily available. Techniques shall be designed

20、 to minimize measurement uncer-tainties. Facilities shall be sufficient to perform system functions within the established criteria defined in Section 4.1. 4.2.4 Training of Personnel. Personnel responsible for operating components of the system shall be trained in their necessary tasks. 4.2.5 Locat

21、ion of Dosimetry System Processing Facilities. Facilities used to perform system functions should be separated from areas where a criticality accident may occur to minimize the effects of potentially elevated ground radiation levels and restricted access following a criticality accident. Considerati

22、ons and preparations shall be made for alternate operations if it is credible that system processing facilities could be unavailable at the time of a criticality accident. Facilities used to evaluate system components should be located at an appropriate distance and/or shielded (as appropriate) from

23、 facilities/areas where irradiated components are staged and/or prepared for evaluation to mitigate the effects of elevated background radiation. 4.2.6 Orientation of Exposed Individuals. Provision should be made to determine and adjust for the orientation of exposed individ-uals with respect to the

24、 location of the criti-cality accident. 4.2.7 Periodic Maintenance and Evalua-tion of System Components. Procedures for the system shall establish routine inspec-tion, maintenance, and replacement re-quirements for components. The procedures shall establish the frequency of inspection and replacemen

25、t to assure that significant material degradation or accumulation of background radiation does not occur. 5.0 Program Requirements 5.1 Training Requirements Provisions shall be made to ensure that per-sonnel needed to perform system functions are properly trained and that sufficient trained personne

26、l are available at all times such that the requirements contained in Section 4.1 can be met. The training pro-gram shall document the training process (initial training, periodic retraining, and re-medial retraining), training requirements, and training results. 5.2 Technical Basis Requirements The

27、criticality accident dosimetry program shall maintain the STBD. The STBD shall in-clude technical principles, design basis, wearing/placement methods, component tolerances, computation methods used, and associated uncertainties for the system. The STBD shall define limitations of the ma-terials and

28、computations used for criticality accident dosimetry. The STBD shall also define the construction of the system and required maintenance activities. See Section 7.0 for additional criteria. 5.3 Procedures Procedures shall be established and main-tained to govern the conduct of the program. These pro

29、cedures shall address (at a mini-mum): Determination and documentation of the date and time of the criticality accident. Compilation of information about the nature of the criticality accident (such as type and form of material). Methods to evaluate shielding of indi-viduals and dosimeters. Determin

30、ation and documentation of distances of individuals and FNAD, if applicable, from the criticality accident. Collection of information regarding the event and individuals present at the time of the event. Guidance for the proper use and appli-cation of the system, including quality control practices.

31、 Methods of periodic inspection to assure that materials used in the dosimeters conform to specification and have main-tained their integrity. 5.4 Quality Assurance A documented QA program shall be implemented which includes process and ANSI/HPS N13.3-2013 5 maintenance procedures for all components

32、 of the system. Procedures, methods and training requirements shall be documented, reviewed, approved, and updated in accordance with the facilitys QA program. If a facility adopts a dosimetry system from a vendor, then the facility using the dosimetry system shall have a QA program. Included in the

33、se procedures shall be actions taken to prevent contamination, both of the samples and by the samples. Maintenance procedures shall include at a minimum inspection of all dosimeters (personal and fixed) and related equipment, as defined in the STBD, at least every three years. 6.0 Performance Criter

34、ia 6.1 Verification and Testing Performance of the system shall be verified in a mixed neutron and photon field. The field should have characteristics similar to a criticality accident. Important characteristics include delivered absorbed dose over the range of 0.1 to 10 Gy (101000 rad) to a phantom

35、. The energy spectra shall be well characterized. Performance testing shall replicate the configuration of normal use, e.g., on phantom or free-in-air. 6.2 Frequency of Verification and Testing Performance of the system, as identified in the STBD, shall be conducted at least every three years. 6.3 P

36、erformance Testing Criteria During performance testing the system shall provide total absorbed dose results within the criteria given in Table 1. The performance statistic, B, is calculated using Equation 1: = ( ) 100 (1) 6.4 Quick Sort Performance The system shall be capable of providing positive i

37、ndication of total absorbed doses exceeding 0.5 Gy (50 rad) during the initial incident response. The system should be capable of sorting individuals by estimated total absorbed dose. 7.0 Specific Considerations for Criticality Accident Dosimetry Several issues can affect the dose determination of t

38、he neutron and photon doses as well as the ability to measure the dose from a criticality accident. The most important issues include use of fixed dosimeters, directional response of the dosimeter materials, nonuniform radiation fields, partial-body exposure, and variation in the spectral response o

39、f the dosimeters. The system design and implementation shall consider these special situations and document them in the STBD. Guidance and additional information can be found in Annex A for these special considerations. 7.1 FNADs The requirements in this section do not apply if FNADs are not part of

40、 the system. 7.1.1 Application. FNADs should be used at any facility where a CAAS is required. FNADs can provide supplemental information to that from personnel dosimeters including indications of neutron-to-photon absorbed dose ratios and total absorbed dose measurement. Table 1. Performance testin

41、g criteria of criticality accident dosimeter systems Total absorbed dose range B 0.1 to 1 Gy (10 to 100 rad) 50% 1 to 10 Gy (100 to 1000 rad) 25% 10 Gy (1000 rad) Must give positive indication of 10 Gy (1000 rad)ANSI/HPS N13.3-2013 6 7.1.2 Placement FNADs should be placed such that there is as littl

42、e intervening shielding and obstruction as practicable between the dosimeters and areas where criticality accidents are possible. The FNAD units shall be placed at distances from the areas they are intended to cover such that the dose at that location is within the response range of the unit for the

43、 range of postulated fission events appropriate to that unit. The placement of FNADs shall be documented and documentation made available to response personnel. The placement of FNAD units shall permit easy retrieval, or retrieval upon exit, with minimum hazard to the retrieving personnel. 7.2 Orien

44、tational Response The response of the system for personnel and dosimeter orientation shall be evaluated and documented in the STBD. Corrections for orientation in total absorbed dose estimates should be made and should provide a conservative or upper bound determination of the dose. 7.3 Partial-Body

45、 Exposure Methods for evaluating partial-body irradia-tion should be established and documented in the STBD. Health and safety personnel (e.g., radiation protection personnel, medical personnel, and first responders) should be trained in identifying conditions that may indicate partial-body irradiat

46、ion. 7.4 Radiation Field Response Response characteristics of the system as-sociated with expected facility and reference neutron and photon radiation fields shall be evaluated and documented in the STBD. 7.5 Criticality Dosimetry Methods Other Than Nuclear Activation Dosimeters The system should co

47、nsider the use and evaluation of biological materials for total absorbed dose estimation. Such methods can be used in cases where exposed individuals did not have dosimetry or to supplement information from dosimeters. If used, such systems shall be documented in the STBD. 7.6 Backup Capabilities Al

48、ternative plans and agreements shall be preestablished in the event the primary system is unavailable. These considerations should include (1) maintaining portable analytical equipment that can be positioned and used at sufficient distances away from the criticality accident, (2) backup power suppli

49、es that assure continued operation in the event of loss of power, or (3) an agreement with a backup processor. 7.7 Radiological and Nonradiological Hazards Component processing procedures shall incorporate methods for minimizing exposure of personnel to radiation and hazardous materials. 8.0 Normative References American National Standards Institute (ANSI). Criticality accident alarm system. American Nuclear Society: La Grange Park, IL; ANSI/ANS 8.3-1997 (R2003; R2012); 1997.