ANS 2 21-2012 Criteria for Assessing Atmospheric Effects on the Ultimate Heat Sink.pdf

1、ANSI/ANS-2.21-2012criteria for assessing atmosphericeffects on the ultimate heat sinkANSI/ANS-2.21-2012ANSI/ANS-2.21-2012American National StandardCriteria for Assessing AtmosphericEffects on the Ultimate Heat SinkSecretariatAmerican Nuclear SocietyPrepared by theAmerican Nuclear SocietyStandards Co

2、mmitteeWorking Group ANS-2.21Published by theAmerican Nuclear Society555 North Kensington AvenueLa Grange Park, Illinois 60526 USAApproved June 5, 2012by theAmerican National Standards Institute, Inc.AmericanNationalStandardDesignation of this document as an American National Standard attests thatth

3、e principles of openness and due process have been followed in the approvalprocedure and that a consensus of those directly and materially affected bythe standard has been achieved.This standard was developed under the procedures of the Standards Commit-tee of the American Nuclear Society; these pro

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10、his standard are encouraged and should be sent to SocietyHeadquarters.Published byAmerican Nuclear Society555 North Kensington AvenueLa Grange Park, Illinois 60526 USACopyright 2012 by American Nuclear Society. All rights reserved.Any part of this standard may be quoted. Credit lines, should read “E

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14、n,facility, or other unique situation only, and therefore is not intended for genericapplication.Responses to inquiries on standards are published in ANSs magazine, NuclearNews, and are available publicly on the ANS Web site or by contacting the ANSStandards Administrator.INQUIRYFORMATInquiry reques

15、ts must include the following:1! the name, company name if applicable, mailing address, and telephonenumber of the inquirer;2! reference to the applicable standard edition, section, paragraph, figure,and0or table;3! the purposes of the inquiry;4! the inquiry stated in a clear, concise manner;5! a pr

16、oposed reply, if the inquirer is in a position to offer one.Inquiries should be addressed toAmerican Nuclear SocietyATTN: Standards Administrator555 N. Kensington AvenueLa Grange Park, IL 60526or standardsans.orgForewordThis Foreword is not a part of American National Standard “Criteria for Assessin

17、gAtmospheric Effects on the Ultimate Heat Sink,” ANSI0ANS-2.21-2012.!Code of Federal Regulations, Title 10, “Energy,” Part 50, “Domestic Licensing ofProduction and Utilization Facilities” 10 CFR 50!, Appendix A, “General DesignCriteria for Nuclear Power Plants,” Criterion 44, “Cooling Water,” requir

18、es suit-able redundancy in the cooling water system features of nuclear power plants toensure that its safety function is accomplished. 10 CFR 50,AppendixA, Criterion2, “Design Bases for Protection Against Natural Phenomena,” requires thatsystems, structures, and components important to safety be de

19、signed to with-stand the effects of natural phenomena without loss of capability to perform itssafety function. The redundancy features of the cooling water system of nuclearpower plants are referred to as the ultimate heat sink. The ultimate heat sink isthe complex of water sources, including neces

20、sary retaining structures e.g., apond or river with its dam!, and the canals or conduits connecting the sourceswith, but not including, the cooling water system intake structures for a nuclearpower unit. The sink constitutes the source of essential service water supplynecessary to safely operate, sh

21、ut down, and cool down a nuclear plant.There is a need to provide consistency to calculations of atmospheric effects toultimate heat sinks at nuclear facilities. Existing regulatory guidance i.e., Reg-ulatory Guide 1.27, “Ultimate Heat Sink for Nuclear Power Plants”! is dated1970s vintage! and does

22、not provide guidance on how to calculate effects toultimate heat sinks using atmospheric parameters.This standard establishes criteria for use of meteorological data collected atnuclear facilities to evaluate the atmospheric effects from meteorological param-eters e.g., dry-bulb temperature0wet-bulb

23、 temperature differential, precipita-tion, wind speed, short wave radiation, incoming solari.e., short wave!radiation,surface water temperature, and atmospheric pressure# on ultimate heat sinks.This standard might reference documents and other standards that have beensuperseded or withdrawn at the t

24、ime the standard is applied. A statement hasbeen included in the references section that provides guidance on the use ofreferences.The ANS-2.21 Working Group of the American Nuclear Society Standards Com-mittee had the following membership:S. A. Vigeant, Chair, Shaw Environmental the word “should”is

25、 used to denote a recommendation; and theword “may” is used to denote permission, nei-ther a requirement nor a recommendation.ultimate heat sink: The complex of watersources, including necessary retaining struc-tures e.g., a pond or river with its dam!, andthe canals or conduits connecting the sourc

26、eswith, but not including, the cooling water sys-tem intake structures for a nuclear power unit.The sink constitutes the source of service wa-ter supply necessary to safely operate, shutdown, or cool down a plant following a design-basis accident.wet-bulb temperature: The temperature ofa wet-bulb th

27、ermometer when the heat leav-ing the wet bulb from evaporative cooling isequal to the heat transferred to the wet bulbby convective heat transfer from the surround-ing air.3 Ultimate heat sink functionThe ultimate heat sink function is to ensurethat design-basis temperatures of the plantssafety-rela

28、ted equipment are not exceeded. Ul-timate heat sinks shall be designed to have thecooling capacity to provide sufficient coolingwater at the maximum allowable inlet temper-ature under the most adverse meteorologicalconditions expected for the power plant cli-matic regime.Ultimate heat sink design sh

29、all be based ondevelopment of numerical models of a coolinglake or cooling tower using meteorological datarepresentative of the site taken at or near thepower plant. The numerical models shall bevalidated using data taken at locations withclimates similar to the climate of the site of theproposed po

30、wer plant. NUREG-0693 1#1!andNUREG-0733 2# give detailed instructions on1!Numbers in brackets refer to corresponding numbers in Sec. 8, “References.”1computer programs used in analyzing small cool-ing and spray ponds, respectively. The tech-niques presented in these reports outline theways in which

31、long-term, off-site meteorologi-cal records can be a! scanned to find the mostadverse conditions,b!correlated to on-site data,c! analyzed statistically, and d! used to pre-dict the highest temperature and water loss.Two other examples of ultimate heat sink mod-els are provided in 3# and 4#. The deta

32、ils ofthe model validation are not within the scopeof this standard.Hourly meteorological data representative ofthe site collected over a minimum period of 10years and extending to as much as 30 years ifdata are available!shall be used to ensure thatinterannual variability of the weather is cap-ture

33、d in the database. On-site data are pre-ferred over off-site National Weather ServiceNWS! data. This is particularly important forultimate heat sink assessments because the ex-treme conditions that will test the design lim-its of the ultimate heat sink will not occurevery year. If a suitable i.e., 1

34、0 years or lon-ger!long-term database cannot be found, it shallbe necessary to use expert judgment to con-struct a meteorological database for the numer-ical model that contains what are believed tobe the most limiting credible set of meteorolog-ical conditions that the power plant operatorswould en

35、counter over the lifetime of the plant.The results of the 10-yearorlonger simula-tion with several extreme events shall be usedto perform extreme value statistical analysesthat project the most extreme weather condi-tions for the expected license period of the powerplant, which could be 60 years or

36、more. Notincluded in this standard is ultimate heat sinkdesign that is unrelated to meteorological datasuch as downstream dam failure.4 Critical time periodThe critical time period for plant operation dur-ing extreme meteorological conditions variesaccording to the type of ultimate heat sink be-ing

37、used and the particular parameter beinganalyzed. The large volumes of cooling lakescause them to respond more slowly to extremeconditions than cooling towers. Thus, the mostextreme conditions for cooling tower tempera-ture performance would be a short period ofextremely high temperature and humidity

38、,whereas for a cooling lake it will be a longerperiod that may not have absolute extremes ashigh as the cooling tower assessment data setbut that will have a longer period of adverseconditions.The U.S. Nuclear Regulatory Commission2!pro-vides guidance5# in regard to the critical timeperiod. In the c

39、ase of a cooling lake, the laketemperature may reach a maximum in 5 daysfollowing a shutdown. Therefore, three criticaltime periods to be included in the assessmentare 5 days, 1 day, and 30 days to ensure theavailability of a 30-day cooling supply. The threeperiods need not occur contiguously but ma

40、y becombined to produce a synthetic 36-day periodthat may be used as the design basis for thelake. In the case of a wet cooling tower, themeteorological conditions resulting in maxi-mum evaporation and drift losses shall be theworst 30-day combination of the controlling pa-rameters such as wet-bulb

41、temperature andwind speed.The critical time period shall be contained inthe 10-yearorlonger database, along with sev-eral other periods of weather that are almostas extreme as the critical time period. The datashall be analyzed using an extreme value prob-ability distribution function such as the We

42、ibullor Fisher-Tippett functions 6,7# to obtain pa-rameter values with a mean recurrence inter-val of 100 years or more.5 Meteorological data input5.1 Cooling lakes/spray pondsThe meteorological data used as input to thenumerical performance model of the heat sinkdiffer, depending on which heat sink

43、 is beingmodeled. For cooling lake and river simula-tions, the required data shall consist of thefollowing: dry-bulb temperature, dew point tem-perature, wind speed, wind direction, solar2!U.S. Nuclear Regulatory Commission, Office of Standards Development, Regulatory Guide 1.27, “UltimateHeat Sink

44、for Nuclear Power Plants,” Revision 2, January 1976 5#.American National Standard ANSI0ANS-2.21-20122radiation including cloud cover!, atmosphericpressure and profiles of temperature, precipi-tation, and humidity as a function of heightabove the ground. These profiles shall be usedfor more accurate

45、computations of net thermalradiation in the surface energy balance modelfor the cooling lake air-water interface. Onemethodology is described in NUREG0CR-41208#.Precipitation is usually reported at NWS sta-tions in the United States and may be added tothecoolinglakesimulation.However,precipita-tion

46、typically does not have a significant effecton the performance of the cooling lake, whichnormally has a stream feeding into it or someother source of makeup water. No credit shouldbetakenformakeupwaterincreaseinwaterin-ventoryunlessthemakeupwatersystemssafetyandqualityclassificationiscommensuratewit

47、hthe ultimate heat sink classification. The largethermal inertia of cooling lakes ensures that in-dividual errors in the meteorological databasehave little effect on the results of the numericalsimulation.5.2 Cooling towersSince cooling towers have low thermal inertiaand respond rapidly to extreme w

48、eather con-ditions, meteorological data sets shall be usedto simulate cooling tower performance. Qual-ity assurance as described in ANSI0ANS-3.11-2005 R2010!9# and Regulatory Guide 1.2310# shall be applied. The meteorological dataused as input to the numerical performancemodel of the heat sink requi

49、red for coolingtowers are much more limited, consisting ofdry-bulb temperature, dew point temperature,and atmospheric pressure. These three vari-ables shall be used to compute wet-bulb tem-perature 11#, which is the single atmosphericvariable required for cooling tower simula-tions along with tower design specifications!.For both mechanical and natural draft coolingtowers, a correction factor shall be added tothe ambient design wet-bulb temperature toaccount for interference effects of nearby tow-ers or other structures. An increase of 18Ftothe de