1、ANSI/ANS-2.15-2013criteria for modeling and calculatingatmospheric dispersion of routine radiologicalreleases from nuclear facilitiesANSI/ANS-2.15-2013ANSI/ANS-2.15-2013American National StandardCriteria for Modeling and Calculating AtmosphericDispersion of Routine Radiological Releasesfrom Nuclear
2、FacilitiesSecretariatAmerican Nuclear SocietyPrepared by theAmerican Nuclear SocietyStandards CommitteeWorking Group ANS-2.15Published by theAmerican Nuclear Society555 North Kensington AvenueLa Grange Park, Illinois 60526 USAApproved February 27, 2013by theAmerican National Standards Institute, Inc
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17、ueLa Grange Park, IL 60526or standardsans.orgForewordThis Foreword is not a part of American National Standard “Criteria for Modeling andCalculating Atmospheric Dispersion of Routine Radiological Releases from Nuclear Facil-ities,” ANSI0ANS-2.15-2013.!Atmospheric dispersion modeling is the mathemati
18、cal simulation of atmosphericprocesses involving the release, transport, diffusion, and fate of airborne pollut-ants. Computer programs and systems that implement atmospheric dispersionmodeling have been in widespread use for decades. As a result, there are manycommon practices among model users. Ho
19、wever, a national standard does notexist that provides criteria for model selection and use for different types ofmodeling applications e.g., assessment of annual releases, accidental releaseevents! or for different types of modeling domains e.g., flat terrain, mountain0valley areas, water0land envi
20、ronments!. Instead, atmospheric dispersion model-ing practices are often based on a diverse set of regulatory guidance and otherdocuments that date from the 1970s and 1980s.Since the publication of these guidance documents, considerable advances haveoccurred in our understanding of the atmospheric p
21、rocesses that govern thetransport, diffusion, and deposition of atmospheric pollutants. Dramatic improve-ments in computer technologies have resulted in the significant increase incomputational processing speeds and information sharing capabilities of avail-able models. Also, technological advances
22、have occurred in the areas of meteo-rological monitoring, data collection, and data sharing that can greatly expandthe capabilities of atmospheric dispersion models. As a result of these changes,atmospheric dispersion modeling selection and usage practices need to be up-dated to incorporate the scie
23、ntific and technological enhancements, improvemodeling results, and support greater consistency among model users.Subject matter experts from the Nuclear Utilities Meteorological Data UsersGroup, the U.S. Department of Energys Meteorological Coordinating Council,and other organizations began working
24、 together in 2004 to define and standard-ize practices that can be used to address the atmospheric dispersion modeling ofradiological releases from nuclear facilities. The working group decided thatseveral standards were needed, based on end-use considerations:ANS-2.15, addressing atmospheric disper
25、sion modeling of routine releases;ANS-2.16, addressing atmospheric dispersion modeling of design-basis accidents;ANS-3.8.10, addressing atmospheric dispersion modeling of accidental re-leases for emergency response.This document, on the modeling of routine releases, is the first of these disper-sion
26、 modeling standards. The working group decided to create all three stan-dards in sequence to take advantage of their similarities, to achieve consistencyamong the standards, and to incorporate the lessons learned from one in pre-paring the next.This standard might reference documents and other stand
27、ards that have beensuperseded or withdrawn at the time the standard is applied. A statement hasbeen included in the references section that provides guidance on the use ofreferences.This standard does not incorporate the concepts of generating risk-informedinsights, performance-based requirements, o
28、r a graded approach to quality as-surance. The user is advised that one or more of these techniques could enhancethe application of this standard.This standard was developed by the ANS-2.15 Working Group of the StandardsCommittee of theAmerican Nuclear Society, which had the following membership:iJ.
29、 Ciolek Chair!, AlphaTRAC, Inc.M. Abrams, ABS GroupT. Bellinger, Y-12 National Security ComplexD. Brown, U.S. Nuclear Regulatory CommissionM. Carroll, Murray the word “should”is used to denote a recommendation; and theword “may” is used to denote permission, nei-ther a requirement nor a recommendati
30、on.simple terrain: Any site where terrain ef-fects on meteorological measurements arenonsignificant.sodar: A wind profiling system that employssound to probe the atmosphere.stability: A measure of the degree of resis-tance of a layer of air to vertical motion. It isused to define the amount of turbu
31、lent mixingin the atmosphere, which directly influencesatmospheric dispersion.stagnation: An atmospheric condition that sup-presses the dispersion of airborne material.transport: The movement of gaseous and0orparticulate matter through the atmosphere.turbulence: Atmospheric motions in which lo-cal v
32、elocities and pressures fluctuate irregu-larly, in a random manner, to form swirlingeddies that can cause rapid mixing 2#.variable-trajectory model: An atmosphericdispersion model where plumes follow complexflow fields usually in three or four dimensions.volume source: The initial configuration of a
33、plume or puff of material within a dispersionmodel that represents a three-dimensionalvolume.3 The modeling processWhen modeling the airborne impacts from rou-tine releases of radiological material, the pro-cessdepictedinFig.1whichexplicitlyconsidersrequirements,QApractices,andthepotentialforcomplex
34、 flow effectsshall be followed.Requirements bound the scope of the modelingproject and provide a metric for determiningsuccessful completion. Quality assurance pro-cesses reduce errors in the course of the mod-eling effort. Complex atmospheric effects, suchas recirculation and stagnation, can signif
35、i-cantly increase the consequences from routineairborne releases of radiological material seeAppendix A!. Therefore, if consequences from astraight-line Gaussian model are .10% of reg-ulatory limits and the site resides in a domainthat experiences complex flow.15% of the year,the complex effects sha
36、ll be explicitly treatedusing variable-trajectory models.Sections 3.1 through 3.12 contain instructionsfor navigating the flowchart contained in Fig. 1.3.1 Step 1: Determine requirements.The first step in any modeling project is tospecify requirements for the project. Require-ments shall be written
37、and shall include clearlyachievable actions that can be objectively testedat the end of the project to demonstrate suc-cessful completion of work. Requirements shallbe uniquely identified and tracked throughoutthe modeling process to allow for verificationof completion. Requirements may come fromout
38、side regulatory agencies or from internalsources.At a minimum, the following shall be includedwhen specifying requirements:regulatory agencies governing atmosphericmodeling studies for the site;applicable regulatory limits associated withthe modeling process;model selection requirementssee Sec. 3.12
39、!;timescale requirements see Sec. 5!;release mode requirements see Sec. 6!;removal mechanism requirements seeSec. 7!;input data requirementssee Secs. 8, 9, and10!;definition of the modeling domain to bestudied;modeling objectives;QA requirements see Sec. 11!.3.2 Step 2: Determine QA components.A for
40、mal QA program shall be incorporated aspart of the modeling process. Since not all com-ponents of a QA program are relevant to allprocesses, the components that are relevant toAmerican National Standard ANSI0ANS-2.15-20133Figure 1 Modeling process for routine releases of radiological materialAmerica
41、n National Standard ANSI0ANS-2.15-20134the modeling process shall be explicitly identi-fied. The QA components that are determinedto be relevant shall be completed. Section 11provides more instructions on QA.3.3 Question 1: Any need orrequirement for variable-trajectorymodels?If project requirements
42、 specify use of variable-trajectory models, the user shall proceed to step4 Sec. 3.8!.3.4 Step 3: Perform straight-lineGaussian modeling.If there are no explicit requirements to usevariable-trajectory models from step 1Sec. 3.1!, then a straight-line Gaussian modelmay be used to assess routine relea
43、ses. How-ever, at the completion of the modeling effort,it shall be determined if use of more complexvariable-trajectory models is required by pro-ceeding through the flowchart depicted in Fig. 1,which considers the severity of projected im-pacts and the existence and frequency of com-plex flow with
44、in the region. Straight-lineGaussian models shall incorporate the effectsof radiological decay and deposition, since theseprocesses are important when comparing mod-eling results against regulatory limits.3.5 Question 2: Are results .10% ofregulatory limits?Results of straight-line Gaussian model ou
45、tputshall be compared to applicable regulatory lim-its defined in step 1 Sec. 3.1!. If results of thestraight-line Gaussian modeling process in step3 Sec. 3.4! produce off-site impacts that are.10% of regulatory limits, it shall be deter-mined if complex flow occurs within that do-main by proceeding
46、 to question 3 Sec. 3.6!.Ifoff-site modeling results do not exceed 10% ofregulatory limits, the next question to answershould be question 5 Sec. 3.9!.3.6 Question 3: Does the domainexperience complex flow?If output from straight-line Gaussian models is.10% of regulatory limits off-site, then the pre
47、s-ence of complex flow within the domain shallbe determined by one of two acceptable ways:1! Documented flow:Ameteorologist or otherindividual with equivalent knowledge of re-gional flow features should identify complexflow regimes within the domain;2! Topographical features: It should be de-termine
48、d if the domain is subject to complexflow based on the existence of any of thefollowing topographical features within thedomain:a! Large bodies of water: If the model-ing domain contains any portion of a bodyof water with a surface area .500 km2,the domain is subject to complex flowsee Appendix A!,b
49、! Mountains: If the domain contains amountain or mountain range, the do-main is subject to complex flow. Moun-tains,150 m493 ft! tallrelative to thedomain! need not be considered unlessthey are within 2 km 1.2 miles! of therelease location,c! Valleys: If the domain is within a val-ley, it is subject to complex flow. Shallowvalleys ,50 m ,164 ft! deep relative tothe domain! that do not have steep sidewalls are not typically considered to havethe potential for complex flow.The rationale behind the determination shallbe documented. If the domain do
