1、ANSI/ANS-8.3-1997criticality accident alarm systemANSI/ANS-8.3-1997This standard has been reviewed and reaffirmed with the recognition that it may reference other standards and documents that may have been superseded or withdrawn. The requirements of this document will be met by using the version of
2、 the standards and documents referenced herein. It is the responsibility of the user to review each of the references and to determine whether the use of the original references or more recent versions is appropriate for the facility. Variations from the standards and documents referenced in this st
3、andard should be evaluated and documented. This standard does not necessarily reflect recent industry initiatives for risk informed decision-making or a graded approach to quality assurance. Users should consider the use of these industry initiatives in the application of this standard. REAFFIRMED J
4、uly 26, 2012 ANSI/ANS-8.3-1997 (R2012) REAFFIRMED June 12, 2003 ANSI/ANS-8.3-1997 (R2003) ANSI/ANS-8.3-1997American National StandardCriticality Accident Alarm SystemSecretariatAmerican Nuclear SocietyPrepared by theAmerican Nuclear SocietyStandards CommitteeWorking Group ANS-8.3Published by theAmer
5、ican Nuclear Society555 North Kensington AvenueLa Grange Park, Illinois 60526 USAApproved May 28, 1997by theAmerican National Standards Institute, Inc.AmericanNationalStandardDesignation of this document as an American National Standard attests thatthe principles of openness and due process have bee
6、n followed in the approvalprocedure and that a consensus of those directly and materially affected bythe standard has been achieved.This standard was developed under procedures of the Standards Committee ofthe American Nuclear Society; these procedures are accredited by the Amer-ican National Standa
7、rds Institute, Inc., as meeting the criteria for AmericanNational Standards. The consensus committee that approved the standardwas balanced to ensure that competent, concerned, and varied interests havehad an opportunity to participate.An American National Standard is intended to aid industry, consu
8、mers,governmental agencies, and general interest groups. Its use is entirely volun-tary. The existence of an American National Standard, in and of itself, doesnot preclude anyone from manufacturing, marketing, purchasing, or usingproducts, processes, or procedures not conforming to the standard.By p
9、ublication of this standard, the American Nuclear Society does not insureanyone utilizing the standard against liability allegedly arising from or afterits use. The content of this standard reflects acceptable practice at the time ofits approval and publication. Changes, if any, occurring through de
10、velop-ments in the state of the art, may be considered at the time that the standardis subjected to periodic review. It may be reaffirmed, revised, or withdrawn atany time in accordance with established procedures. Users of this standardare cautioned to determine the validity of copies in their poss
11、ession and toestablish that they are of the latest issue.The American Nuclear Society accepts no responsibility for interpretations ofthis standard made by any individual or by any ad hoc group of individuals.Requests for interpretation should be sent to the Standards Department atSociety Headquarte
12、rs. Action will be taken to provide appropriate response inaccordance with established procedures that ensure consensus on the inter-pretation.Comments on this standard are encouraged and should be sent to SocietyHeadquarters.Published byAmerican Nuclear Society555 North Kensington AvenueLa Grange P
13、ark, Illinois 60526 USACopyright 1997 by American Nuclear Society. All rights reserved.Any part of this standard may be quoted. Credit lines should read “Extracted fromAmerican National Standard ANSI0ANS-8.3-1997 with permission of the publisher, theAmerican Nuclear Society.” Reproduction prohibited
14、 under copyright convention unlesswritten permission is granted by the American Nuclear Society.Printed in the United States of AmericaForewordThis Foreword is not part of American National Standard Criticality Accident Alarm System, ANSI0ANS-8.3-1997.!The usefulness and protective features of criti
15、cality accident alarm systems have beendemonstrated in instances of accidental criticality that have occurred during the processingof fissionable materials. This standard provides guidance for the establishment and main-tenance of an alarm system to initiate personnel protective actions in the event
16、 of inad-vertent criticality.Preparation of the standard, begun in 1966, resulted in the issuance of N16.2-1969, and aninitial revision was issued in 1979. A second revision, issued in 1986, incorporated relevantfeatures of American National Standard Immediate Evacuation Signal for Use in Industrial
17、Applications, ANSI N2.3-1979. The 1986 revision also deleted the section that addressedemergency planning; such guidance is now provided in American National StandardAdministrative Practices for Nuclear Criticality Safety, ANSI0ANS-8.19-1996.Most of the changes incorporated into this revision of ANS
18、-8.3 are oriented towards clar-ification, rather than change, of existing standard requirements and recommendations.Where concern exists for accidents of smaller magnitude than alarm systems have tra-ditionally been designed to detect, additional guidance is now provided.Use of portable instruments
19、to augment an installed accident alarm system is now morespecifically addressed. The term “immediate evacuation” has been replaced with “person-nel protective action” since for some shielded facilities or locations, proper immediate re-sponse by some personnel may be to remain at their current locat
20、ion rather than to evac-uate.This standard is compatible with ISO 7753, Nuclear energyPerformance and testingrequirements for criticality detection and alarm systems. IEC 860, Warning equipment forcriticality accidents, contains useful information regarding electrical characteristics andtesting proc
21、edures for alarm equipment.Appendix B has been extensively revised to provide analytical methods and exampleapplications for determining detector placement.Working Group ANS-8.3, which revised this document, had the following membership:D. A. Reed, Chairman, Oak Ridge National LaboratoryR. E. Anders
22、on, Los Alamos National LaboratoryW. A. Blyckert, Mohr however, this riskcannot be eliminated. Where a criticality acci-dent may lead to an excessive radiation dose, itis important to provide a means of alertingpersonnel and a procedure for their promptevacuation, or other protective actions to limi
23、ttheir exposure to radiation.2. ScopeThis standard is applicable to all operations in-volving fissionable materials in which inadver-tent criticality can occur and cause personnel toreceive unacceptable exposure to radiation.This standard is not applicable to detection ofcriticality events where no
24、excessive exposureto personnel is credible, nor to nuclear reactorsor critical experiments. This standard does notinclude details of administrative actions or ofemergency response actions that occur afteralarm activation.3. Definitions3.1 Limitations. The following definitions areof a restricted nat
25、ure for the purpose of thisstandard. Other specialized terms are definedin the Glossary of Terms in Nuclear Scienceand Technology 2#.3.2 Shall, Should, and May. The word “shall”is used to denote a requirement, the word“should” to denote a recommendation, and theword “may” to denote permission, neith
26、er arequirement nor a recommendation. To con-form with this standard, all operations shall beperformed in accordance with its requirementsbut not necessarily with its recommendations.3.3 Glossary of Termscriticality accident. The release of energyas a result of accidental production of a self-sustai
27、ning or divergent neutron chain reaction.excessive radiation dose. Any dose to per-sonnel corresponding to an absorbed dose fromneutrons and gamma rays equal to or greaterthan 0.12 Gy 12 rad! in free air.minimum accident of concern. The small-est accident, in terms of fission yield and doserate, tha
28、t a criticality alarm system is re-quired to detect.4. General Principles4.1 General4.1.1. Installation of an alarm system im-plies a nontrivial risk of criticality. Wherealarm systems are installed, emergency pro-cedures shall be maintained. Guidance for thepreparation of emergency plans is provide
29、d inAmerican National Standard AdministrativePractices for Nuclear Criticality Safety, ANSI0ANS-8.19-1996 3#.4.1.2. Process equipment used in areas fromwhich immediate evacuation is required shouldbe so designed that leaving the equipmentwill not introduce significant risk.4.1.3. The purpose of an a
30、larm system is toreduce risk to personnel. Evaluation of theoverall risk should recognize that hazards mayresult from false alarms and subsequent sud-den interruption of operations and relocationof personnel.4.2 Coverage4.2.1. The need for criticality alarm systemsshall be evaluated for all activiti
31、es in which theinventory of fissionable materials in individ-ual unrelated areas exceeds 700 g of U-235, 500 gof U-233, 450 g of Pu-239, or 450 g of any com-1Numbers in brackets refer to corresponding numbers in Section 8, References.1bination of these three isotopes.2For opera-tions involving signi
32、ficant quantities of otherfissionable isotopes, this evaluation shall bemade whenever quantities exceed the subcrit-ical mass limits specified in American Na-tional Standard Nuclear Criticality Control ofSpecial Actinide Elements, ANSI0ANS-8.15-1981 R1995!4#. Also, this evaluation shall bemade for a
33、ll processes in which neutron mod-erators or reflectors more effective than waterare present, or unique material configurationsexist such that critical mass requirements maybe less than the typical subcritical mass limitsnoted above.For this evaluation, individual areas may beconsidered unrelated wh
34、en the boundaries be-tween the areas are such that there can be nouncontrolled transfer of materials betweenareas, the minimum separation between mate-rial in adjacent areas is 10 cm, and the arealdensity of fissile material averaged over eachindividual area is less than 50 g0m2. This stip-ulation i
35、s applicable only to the three specificisotopes noted aboveU-235, U-233, and Pu-239!.4.2.2. A criticality alarm system meeting therequirements of this standard shall be in-stalled in areas where personnel would be sub-ject to an excessive radiation dose. For thispurpose, the maximum fission yield in
36、tegratedover the duration of the accident may be as-sumed not to exceed 2.0 H11003 1019fissions. Thebasis for a different maximum fission yieldshall be documented.If criticality accidents of lesser magnitude thanthe minimum accident of concern given in 5.6are of concern, then other detection methods
37、e.g., audible personnel dosimetry! should beconsidered. These other detection methods arenot considered as criticality accident alarm sys-tems and are not covered by this standard.4.2.3. In areas in which criticality alarm cov-erage is required, a means shall be provided todetect a criticality accid
38、ent and to signal thatprompt protective action is required.4.3 Criticality Alarm4.3.1. Criticality alarm signals shall be forprompt evacuation or other protective actions.The criticality alarm signals should be uni-form throughout the system. The signals shallbe distinctive from other signals or ala
39、rms whichrequire a response different from that neces-sary in the event of a criticality accident.4.3.2. The signal generators shall be auto-matically and promptly actuated upon detec-tion of a criticality accident.4.3.3. After actuation, the signal genera-tors shall continue to function as required
40、 byemergency procedures, even if the radiationfalls below the alarm point. Manual resets,with limited access, should be provided out-side areas that require evacuation.4.3.4. A means for manual actuation of thecriticality alarm signal may be provided.4.3.5. For all occupied areas where person-nel pr
41、otective action is required in the eventof criticality accident detection, the numberand placement of criticality alarm signal gen-erators shall be such that the signals are ad-equate to notify personnel promptly throughoutthose areas.4.3.6. The audio generators should producean overall sound pressu
42、re level of at least 75dB, but not less than 10 dB above the maxi-mum ambient noise level typical of each areafor which audio coverage is to be provided.34.3.7. Because excessive noise levels can beinjurious to personnel, the audio generatorsshould not produce an A-weighted sound levelin excess of 1
43、15 dB at the ear of an individual.4.3.8. In areas with very high audio back-ground or mandatory hearing protection, vi-sual signals or other alarm means should beconsidered.4.4 Dependability4.4.1. Consideration shall be given to theavoidance of false alarms. This may be accom-2These fissionable mate
44、rial limits are the single parameter subcritical masses for nonuniform mixtures in ANSI0ANS-8.l-1983R1988!.3Appendix C provides information to assist in the determination of desired signal characteristics.American National Standard ANSI0ANS-8.3-19972plished by providing reliable single detectorchann
45、els or by requiring concurrent responseof two or more detectors to initiate the alarm.In redundant systems, failure of any single chan-nel shall not prevent compliance with the de-tection criterion specified in 5.6.4.4.2. Portable instruments may be used inspecial situations to augment an installed
46、crit-icality accident alarm system. Examples ofsuch situations include alarm system mainte-nance or testing, evacuation drills, activitiesin areas not normally occupied by personnel,or other special operations. Where portableinstruments are used to meet the intent ofthis standard, the usage shall be
47、 evaluated todetermine appropriate criteria of this stan-dard. Criteria for such use of portable instru-ments shall be specified in procedures.4.4.3. Process areas in which activities willcontinue during power outages shall have emer-gency power supplies for alarm systems, or suchactivities shall be
48、 monitored continuously withportable instruments.4.4.4. Adequate sensitivity of the alarm sys-tem to respond to the minimum accident ofconcern is addressed in 5.6. The system shallbe sufficiently robust as to actuate the alarmsignal when exposed to the maximum radia-tion expected.5. Criteria for Sys
49、tem Design5.1 Reliability. The system shall be de-signed for high reliability and should utilizecomponents that do not require frequent ser-vicing, such as lubrication or cleaning. Thesystem should be designed to minimize theeffects of non-use, deterioration, power surges,and other adverse conditions. The design ofthe system should be as simple as is consis-tent with the objectives of ensuring reliableactuation of the criticality alarm signal andavoidance of false alarms.5.2 System Vulnerability. All components ofthe system should be located or protected tominimize damage in case
