RS-13-051, Additional Information Supporting License Amendment Request to Revise Technical Specification 3.7.3, Ultimate Heat Sink

Additional Information Supporting License Amendment Request to Revise Technical Specification 3.7.3, Ultimate Heat Sink

ML13042A405
Person / Time
Site:	LaSalle
Issue date:	02/11/2013
From:	Gullott D Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-13-051, TAC ME9076, TAC ME9077
Download: ML13042A405 (10)

Text

1 4300 4300 Winfield W!nfeld Road Road W3rrenville, Warrenvllle,!LL60555 60555 Exelon Exeton Generation Generation, 630 630 657 6572000 2000 Office Office RS-13-051 RS-13-051 10 10 CFR CFR 50.90 50.90 February 11, February 11, 2013 U. S. Nuclear U. Nuclear Regulatory Regulatory Commission Commission Document Control ATTN: Document Control Desk Desk Washington,DC Washington, DC 20555-001 LaSalle County Station, Units 1 and 2 LaSalle FacilityOperating Facility Operating License License Nos. NPF-1 NPF-111 and and NPF-18 NRC Docket NRC Docket Nos.

Nos. 50-373 50-373 andand 50-374

Subject:

AdditionalInformation Additional InformationSupporting SupportingLicenseLicenseAmendment Amendment Request Request to Revise Revise Technical Specification 3.7.3, "Ultimate "Ultimate Heat Heat Sink" Sink"

References:

Letter from

1) Letter from D.D. M.

M.Gullott Gullott(Exelon (Exelon Generation Generation Company, LLC) LLC) to u. U. S. Nuclear Nuclear Regulatory Commission, Regulatory Commission, "Request for for aa License Amendment to to LaSalle LaSalle County County Station, Units 1 and 2, 2, Technical Technical Specification Specification3.7.3, 3.7.3,'Ultimate

'UltimateHeat HeatSink,"'

Sink,'11 dated July July 12,2012 12, 2012

2) Letter Letter from from D.

D. M.

M. Gullott Gullott(Exelon (Exelon Generation Generation Company, LLC) LLC) to U. u. S. Nuclear Nuclear Regulatory Commission, "Supplemental "Supplemental Information Related to License Information Related License Amendment Request to to LaSalle LaSalle County County Station, Units 1 and 2 Technical Technical Specification 3.7.3, 3.7.3, 'Ultimate

'Ultimate Heat Sink,"' datedSeptember Sink,'" dated September 17, 2012 17,2012

3) Letter fromN.

Letter from N.J.J.DiFrancesco DiFrancesco (U. (U. S. Nuclear Regulatory Commission) to to M. J. Pacilio (Exelon Generation M. Generation Company, Company,LLC), LLC), "LaSalle "LaSalle CountyCounty Station, Station, Units 1 and 22 -- Request Requestfor forAdditional AdditionalInformation Information Related Related to to License License Request to Amendment Request to Technical Technical Specification Specification3.7.3 3.7.3Ultimate UltimateHeat HeatSinkSink (TAC Nos.

Nos. ME9076 and ME9077),"

ME9077)," dated January 9,2013 9, 2013

4) Letter from P.

Letter from P. R.

R. Simpson Simpson (Exelon (Exelon Generation Generation Company, Company, LLC) to U. u. S.

S. Nuclear Nuclear Commission,"Response Regulatory Commission, "ResponsetotoRequest Request forfor AdditionalInformation Additional Information Related to License License Amendment Amendment Request Requestto to Technical Technical Specification Specification 3.7.3, 3.7.3,

'Ultimate Sink,"'dated

'Ultimate Heat Sink,'" dated January January 18, 18, 2013 2013 In In Reference 1, 1, Exelon Exelon Generation Company, Company, LLC, (EGC) requested LLC, (EGC) requested an amendment amendmentto to the the Technical Technical Specifications Specifications(TS)

(TS) of of Facility Facility Operating Operating License LicenseNos.

Nos.NPF-1 NPF-11 1 and andNPF-18 NPF-18for forLaSalle LaSalle County County Station, Units 1 and 2 (LSCS).(LSCS). TheThe license licenseamendment amendmentwould wouldallow allow the the TSTStemperature temperature limit of the limit of the cooling cooling water water supplied to the plant plant from from the the Ultimate Ultimate Heat HeatSinkSink(UHS)

(UHS) to to vary vary with with the the observed observed diurnal diurnal cycle. EGCEGC supplemented supplementedReferenceReference11with with aaletter letterdated datedSeptember September17, 17,2012 2012 (Reference (Reference2). 2).

February 11, 11, 2013 U. S.

U. S. Nuclear Regulatory Commission Page 2 In Reference In Reference 3, the U. U. S. Nuclear Nuclear Regulatory Regulatory Commission Commission (NRC) (NRC) requested requestedadditional additional information information to complete its its review reviewof ofthe theproposed proposed license license amendment amendment request. Attachments Attachments 1, 1, 22and and33of of Reference 44 provided provided the requested requestedinformation, information, withwith the the exception exception ofof Questions Questions33and and55ofof Reference 3. As As discussed discussedwith with the the NRC NRC on on January January17, 17, 2013 2013andanddocumented documentedininReference Reference4,4, those responses responseswould would be be provided provided in a separate separate submittal.

submittal.

The Attachment of this this submittal submittal provides provides the requested requested information information for Questions 33 and and 55of of Reference 3.

EGC has has reviewed reviewed thethe information information supporting supporting aafinding finding ofof no no significant significant hazards hazardsconsideration consideration that was previously previously provided to the NRC NRC in Attachment 1 of of Reference 2. TheTheadditional additional information provided information provided ininthis thissubmittal submittaldoes does not not affect affect the the bases bases for concluding that the proposed proposed license amendments amendments do do not not involve involve aa significant hazards consideration.

significant hazards consideration.

In accordance In accordance with with 1010 CFR CFR 50.91, 50.91, "Notice IINotice for for public comment; State State consultation,"

consultation,1I paragraph paragraph(b), (b),

a copy of thisthis letter letter and and its its attachments are are being being provided provided to the designated designatedState StateofofIllinois Illinois official.

There are no regulatory commitments contained in in this this submittal.

submittal.

Should you have any questionsquestions concerning concerning this this letter, letter, please pleasecontact contactMs.Ms.Lisa LisaA.A. Simpson Simpson at at (630) 657-2815.

(630)

II declare declare under penalty of perjuryperjury that that the the foregoing foregoing isistrue true and and correct.

correct. Executed Executed on on the the 11th 11 th day day of February 2013.

Respectfully, David M. M. Gullott Manager -- Licensing Licensing Exelon Generation Company, LLC

Attachment:

Additional InformationSupporting Additional Information Supporting License License Amendment Amendment Request Request to to Revise Revise Technical Specification 3.7.3, "Ultimate Heat Specification 3.7.3, IIUltimate Heat Sinkll Sink" cc: Illinois Emergency Management Agency - Division Division of ofNuclear NuclearSafety Safety

ATTACHMENT Additional Information Supporting License Amendment Request Request to to Revise Technical Specification 3.7.3, "Ultimate "Ultimate HeatHeatSink" Sink" In aa letter In letter dated January January 9, 2013, the 9,2013, theNRCNRCrequested requestedthat thatEGC EGGprovide provideadditional additionalinformation information related to the LaSalle County Station (LSGS)

County Station (LSCS) proposed proposed license amendment amendment request requestsubmitted submitted July 12, 2012. This This Attachment Attachment providesprovides the requested requestedinformation information for Questions Questions 33 and and 55of of the the January 9, January 9, 2013, 2013, letter.

letter.

NRC Question 3: 3:

Review of WeatherWeather Screening

Background:

The purpose of

Background:

of the LakeT-PC LakeT-PC model model analysis analysis is is to to ensure that the temperature of of the UHS during the design basis basis event eventwillwill not result in in the UHS UHS exceeding exceeding thethedesign designlimitlimit for for the cooling cooling waterwater supplied supplied to tothe the plant plantsafety safetysystems.

systems. Attachment Attachment 1 to the proposed license license amendment request amendment request (LAR)

(LAR) states that that the the transit transit time of the plant accident energy energy through through the the UHS is UHS is approximately approximately30 30hours.

hours. Section 4.0 4.0 of of the proposed proposed LAR LAR describes describes the the selection selection of of the the worst-case meteorological worst-case meteorological conditions conditions for 1-day and 30-day 3~-day periods.

periods.

Request: Justify Justify the the selection selection and and use useof of aa24-hour 24-hour worst-case worst-casemeteorological meteorological period period when analyzing a 30-hour 30-hour transit transit time.

time.

EGC Response to to Question Question 3: 3:

As documented in in Reference Reference 11and andinin the theLSCS LSCSUFSAR, UFSAR, LSCS LSCSisiscommitted committed to toRegulatory Regulatory Guide (RG) Revision 1. Section (RG) 1.27, Revision Section C.1.b C.1.bof ofthe theRegulatory RegulatoryGuide Guidestates, states,ininpart, part,"Analysis "Analysisofof the temperature problem problem should use use thethe worst worst 1-day 1-dayandandworst worst 30-day 30-dayperiods periodsof of meteorological record in meteorological in the the region region resulting resulting in in minimum minimumheat heat transfer transfer to to the the atmosphere atmosphere and and maximum plant maximum plant intake intake temperature.

temperature."II LSCS's LSCS*sUHS UHS analysis analysiSisisconsistent consistentwith withthis thisregulatory regulatory guidance.

Although Although not not committed committed to to RG RG 1.27, Revision 2, LSCS performed performed aa sensitivity sensitivity evaluation evaluation consistent with consistent with the regulatory regulatory guidance guidance in in section sectionB, B, which which states, states,ininpart, part,"Alternatively, "Alternatively, the the worst 36-consecutive-day period from historical climatological from historical climatologicaldata data may may bebe used as as the the design design basis. This Thisperiod periodmay mayor or maymaynot notinclude includethe theworst worst5-day, 5-day,1-day, 1-day,oror30-day 30-dayperiod."

period. II Consistent with this guidance with this guidance and the the LSCS LSGS 30-hour 30-hour UHS UHS transit transit time, time, the the worst worst 774 774 consecutive hours (30 hour3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> + 24 hour ++ 30 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 30 days) days) was was used to evaluate the responseresponseof of the the UHS UHS during the during the design design event.

event. The The worst worst 774-hour 774-hour period was determined by the screening process process described in in Reference Reference 44 for for the the historical historical environmental environmental periodperiod that created createdthethehighest highestrunning running average UHS UHS temperature for 774 continuous for 774 continuous hours.hours. Note Note this this screening screening did did not not consider the transit time time in in selecting selecting the the worst worst 774-hour 774-hour period, period, but but used used the the period period that created the highest highest running temperature running temperature averageaverage for 774 continuous hours. This evaluation demonstrated demonstrated Figure Figure 33 of Reference 11 remains of remains limiting limiting (i.e.,

(Le., the limiting temperature at 06:00 would limiting temperature would be be more more than than3.5°F 3.5°F greater than greater than the the Reference Reference11limit limitofof 101.25°F).

101.25°F).

Additionally,LSGS Additionally, LSCShas has completed completed aa sensitivity sensitivity evaluation evaluation of ofthe the UHS UHS response response considering considering the the effects of of the the accident energy transit time time though though thethe UHS.

UHS. ThisThis evaluation is further described in the in the response response to to Question Question 5. 5.

Page 1 of 8

ATTACHMENT Additional Information Additional InformationSupporting Supporting License License Amendment Request to Revise Technical Specification 3.7.3, "Ultimate "Ultimate Heat Heat Sink" Sink" NRC Question Question 5: 5:

Review of UHS Transient Heatup Heatup

Background:

The The licensee licensee has hasstated statedthat thatthe thetransit transittimetimefor forcore corestandby standbycoolingcooling systemsystem (CSCS) flow flow across across the UHS pond during during a design-basis design-basis accident accidentloss-of-coolant loss-of-coolant accident accident (DBA-LOCA)

(DBA-LOCA)isis30 30hours hours withwiththe the UHS sediment level of 1.5 feet. InInthe UHS sediment theDBA-LOCA DBA-LOCA analysis, analysis, the licensee licensee considered consideredthe theworst worst24-hour 24-hourperiod periodofofmeteorological meteorologicalconditions conditionsfor forcontrolling controlling parameters parameters in in determining determining peak peak UHS UHS temperature.

temperature. By Byconsidering consideringthe theworst worst24-hour 24-hourperiod,period, the licensee's licensee's analysis analysisshowed showedthat thatthe thepeak peaktemperature temperatureofofthe theUHSUHSafter aftera aLOCA, LOCA,which which started started at at 6:00 6:00 a.m.,

a.m., would would be beapproximately approximately12 12hours hoursafter afterthe theLOCA, LOCA, which which occurs occurs 18 18hours hours before any of the UHS water that is affected by accident heat heat input input enters enters the the plant plant intake.

intake.

Attachments II [Figure Attachments [Figure 17.7]

17.7] and LL [Appendix L9.4] L9.4] of of Calculation L-002457, "LaSalle County County Station Ultimate Heat Sink Analysis, Analysis," II show show the the effects of of the the heat addedadded to to the theUHS UHS by by thethe DBA-LOCA,whose DBA-LOCA, whose effects effects do do not reach the the UHS UHS outlet outletto tothe theplant plantuntil until3030hours hoursafter afterthe theDBA-DBA-LOCA.

LOCA. Figure 17.7 17.7 shows temperatures temperaturesnear near140 140 OF initially entering ofinitially entering the theUHS UHSimmediately immediatelyafter after the DBA DBA and shows shows the the UHS UHS inlet inlet temperature temperaturetotobe bewell wellaboveabove120 120OF offorfor most mostof of the the first first day day after the DBA-LOCA, DBA-LOCA, yet, yet, thethe UHS UHS outlet outlet to to the the plant plant hashas already peaked peakedat at107107OF about of at about 3:00 p.m. on the the first first day. According According to to Figure Figure 44 of of the the LAR,LAR, the maximum temperature temperature of of the UHS outlet UHS outlet temperature temperature on the second second day day isis below below the the maximum maximum temperature temperature on on the thefirst first day, day, indicating indicating thatthat the heat heat added addedby bythe theDBA-LOCA DBA-LOCA has has little little effect on the UHS UHS outlet temperature.

temperature.

The seeming lack lack of influence influence upon upon peak peak UHS UHS temperature temperature by by the the accident heat and the meteorological conditions conditions of of second second day day after after the the accident accidentcould could be beattributed attributedto toaarelatively relatively cool, cloudy, or or windy windy day dayafter afterthe thefirst firstday dayfollowing followingthe theDBA-LOCA, DBA-LOCA, which which isisthe thefirst firstday dayofof the 30-day 30-day critical critical period.

Issues: HeatHeat waves waves where weather extremes extremes have have persisted persistedfor for multiple multiple consecutive consecutive days are are not uncommon. Considering Consideringthat thataaheat heatwave waveisisininprogress progressand andthethefirst firstcritical criticaltimetimeperiod period of of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> as as used used by by the the licensee, licensee,the thefirstfirst day day ofof the the worst worst 30-day period period may not be representative of representative of the the actual actual second second day after after an accident. Also, Also, in in aaletter letter dated dated May 6, 2011, May 6,2011, the licensee stated that high licensee stated that high temperaturestemperatures and humidity humidity during during the daytime, in in conjunction with conjunction with minimal cooling minimal cooling at night and little precipitation during little precipitation duringthe thesummer summer months, months, results in in elevated elevated water temperatures in in the LSCS UHS. UHS.

The NRC staff staff is is not not certain certain that that the licensee has has chosen chosenappropriate appropriatecritical critical time time periods periods unique to the specific design of the CSCS pond. pond. According According to to Regulatory Regulatory PositionPosition 11 of of Regulatory Guide (RG) (RG) 1.27, 1.27, "the "the meteorological meteorologicalconditions conditionsresulting resultingininminimum minimumwater watercoolingcooling should be be the the worst worst combination combination of of controlling controlling parameters, parameters,including including diurnal diurnal variations variations where where appropriate, for for the critical period(s) unique to the critical time period(s} the specific specific design designof of the thesink,"

sink," and and "sufficientconservatism "sufficient conservatism should should be provided to ensure ensure that that aa30-day3~-daycooling cooling supply supply isis available available and that design basis basis temperatures temperatures of of safety safety related related equipment equipment are not not exceeded." In In RG RG 1.27 1.27 it also states states that that"meteorological "meteorological conditionsconditions considered considered in in the the design design of of the the UHSUHS should should be be selected selected withwith respect respect to to the thecontrolling controlling parameters parameters(i.e., (i.e.,windwind speed, speed,humidity, humidity, dew dewpoint,point, air air temperature, solar temperature, solarradiation, radiation, etc.)."

etc.}."

The licensee licensee selected selectedaafirst firstcritical critical time time period period of of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, hours, independent independentof ofthe thetimetimeof of the the accident and and thethe UHS UHS transit transit time.

time. However, However,the theNRCNRCstaff staffbelieves believesthat thatthe thefirst firstcritical critical timetime period would would be be 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> or or greater, greater, dependent dependentupon upontime timeofofaccident accidentinitiation initiation and andUHS UHStransittransit Page 2 of 8

ATTACHMENT Additional Information Additional InformationSupportingSupporting License License Amendment Request Request to to Revise Technical Revise Technical Specification 3.7.3, "Ultimate "Ultimate Heat Heat Sink" Sink" Using these time. Using these variable variable and and first first critical time periods would critical time would yieldyield more more limiting limitingand and accurate accurate results. The staff also believes believes thatthatthe thefirst first critical critical time period should be be verified verified by by assuming assuming greater first criticaltime first critical timeperiods periodsand andperforming performingthe theanalysis analysisand andcomparing comparingresults. results. The staff also believes that the analysis for each assumed assumed accident accidentstart starttime, time, i.e.,

i.e., 6:00 6:00 a.m.a.m. -- 99 a.m.,

a.m.,

etc., would would have its its own set set of of worst-weather worst-weather data dataforfor its its particular particular critical critical time period.

Request:

a. The NRC staff staff requests requests that that the the licensee licenseejustifyjustify their their selection of of weather weather data dataandandcritical critical time periods time periods or or propose propose new analysis that would would address address the NRC staff staff concerns concerns presented presented in Issues in Issues above.

EGC Response to Question 5a:

RG 1.27, Revision 1, Regulatory Position C.1.b states, RG states, in in part, part, "Analysis "Analysis of the temperature temperature problem should use problem use the the worst worst 1-day 1-day andandworstworst30-day30-dayperiods periodsof ofmeteorological meteorological record recordinin the region resulting in minimum minimum heat heat transfer to the atmosphere atmosphere and andmaximum maximumplant plantintake intake temperature... Applicants Applicants shouldshould be be assured assuredthat thateither eitheraanormalnormal or or emergency emergency shutdown shutdown during the worst 1-day and and 30-day 30-day period period of of record record willwill not result in plant intake water temperatures exceeding design basis temperatures." temperatures." This This was was thethe basis basis for for LSCS's selection of weather data.

In In order order toto address address the NRC's NRC's issues issues presented presentedabove, above,LSCS LSCSperformed performedaasensitivity sensitivity evaluation of evaluation of the the response response of of the UHSUHS considering the accident energy energy transit transit time time through the UHS.

UHS. As As described described in in Reference Reference 1, 1, the the time time required required at at the the start start of of anan accident accident for for safety-related cooling water returned to the UHS UHS from from the plant to traverse the the UHS UHS andand enter the plant plant intake intake is is approximately approximately 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

screened historical LSCS screened historical environmental environmental data data as as described in in Reference Reference 22 for for the 30-hour 30-hour periods of timetime creating creating the the highest highest running runningaverage average UHS UHS temperatures.

temperatures. These Theseperiods periodsof of time are then applied to the design design event eventto todetermine determinethe theworst worstperiod period (i.e.,

(Le.,thetheperiod periodthat that creates creates thethe highest highest UHS UHS temperature).

temperature). For For example, example, the the period period from from JuneJune 22,2009, 22, 2009, to to June 23,23, 2009, 2009,had hadthethesecond secondhighest highestrunning runningaverageaveragefor for3030hours hoursfor foran anaccident accidentstarting starting at 0600 during the 0600 during the screening process. However,this process. However, thistime time period period generated generated the the highest highest UHS temperature temperature when when applied applied to to the the design design basis event. event. Therefore, Therefore,the theworst worst30-hour 30-hour environmental environmental period periodwas was determined determinedto to exist exist from from0600 0600 JuneJune 22,2009, 22, 2009, to to 1200 1200 June 23, 2009, for 23,2009, for the 0600 event.event. The Thesame samescreening screeningprocess processwas wasperformed performedfor for accidents starting accidents starting at each each three-hour three-hour increment increment in a 24-hour period. Additional Additional screenings screenings were performed performed for for transit transittimes times (or (orfirst firstcritical critical times)ofof33, times) 33,36, 36,andand39 39hours.

hours. These These additional screenings demonstrated additional screenings demonstrated the June the June 22, 2009, to to June 23, 2009, periodremained June 23, 2009, period remained limiting forall limiting for allconsidered considered accident accident starting starting timestimes and and transit transittimes.

times. A A review review of of plant plant data data revealed the environmental environmental period periodfrom from0800 0800June June22,2009, 22, 2009, to to 0200 June 24, 24, 2009, 2009, resulted in in the LSCS LSCS cooling cooling lake lakeincreasing increasinginintemperature temperaturefrom from 89 89°F

° F toto 98°F. Consistent 98°F. Consistent with the guidance with the guidance of of RG RG 1.271.27 Revision Revision 2 (as described described in in the response response to toQuestion Question3), 3),the the 774-consecutive-hour period starting starting with with the the worst 30-hour periods on 30-hour periods on June June 22, 2009 were 22, 2009 were evaluated.

Excessive Excessive conservatism conservatism in in the existing methodology was existing methodology was assessed assessed and andreduced reducedfor forthe the sensitivity evaluation. The sensitivity evaluation. The accident accident energy energyrelease releaseprofile profileto tothe theUHSUHSand andthe the LAKET-PC Page Page 33 of of 88

ATTACHMENT Additional Information Additional InformationSupporting SupportingLicense License Amendment Amendment Request to ll Revise Technical Specification 3.7.3, 3.7.3, "Ultimate "Ultimate Heat Sink Sink" wind function wind functionwere wereboth bothaltered alteredtotoreducereduceexcessive excessive conservatism.

conservatism. The The accident accident energyenergy release toto the the UHS UHS in in the existing existing design design analysis analysisfollows follows the the profile profile of the reactor reactor core core decay heatheat curve curve - exponentially exponentially decreasing decreasingfunction function with with time. The Thelargest largestcontributor contributor to to the accident energy is the reactor core decay decay heatheat from from both units. Accident Accident energyenergy in in additionto addition tothe thedecay decay heatheat transferred transferred to tothe the UHS UHSisisassumed assumed to to be be added added at a constant rate

-- pump pump heat, area area cooling cooling heat, and and sensible sensible heatheatfromfrom the the reactor reactor pressure pressurevesselvesseland andfuelfuel (assumed constant constant for for the first first six hours of the event). This modeling results in This modeling results in the largest the largest amount of accident energy energy being being transferred transferred to to the theUHSUHSin in the thefirst first hour hour and andrapidly rapidly decreasing with time. This is considered to be excessively with time. excessively conservative.

conservative. AA realistic realistic model model of the of the accident accident energy transfer to the UHS would would show show the the reactor core decay decay heatheat andand sensible heat heat first beingbeing transferred transferred to to the the suppression pool and then released released to to the the UHS UHS by operation by operation of ofthe the RHRRHRsystem.

system. This results in a more steady steady accident accident energy energy transfer transfer to the UHS as opposedopposed to to the the exponential exponential transfer transferof of the the existing existing design designanalysis.

analysis.

The response response to to Question Question 22 of of Reference Reference55describes describesthe LAKET ~PC Hefner theLAKET-PC Hefner and and Ryan Ryan wind wind functions application functions application in in the the existing existing design design analysis. When the calculated UHS UHS temperature within 2.5°F is within 2.5°F of ofthe the natural natural UHS UHS temperature, temperature, the the Lake-Hefner Lake*Hefner wind wind function function is used used in in the the evaporative and conductive/convective cooling terms. When the calculated calculated UHS UHS temperature is is 2.5°F greater greater than than thethe natural natural UHSUHS temperature, temperature, the theRyan Ryanwindwind function function is is used. As described in the response to Question 2 of Reference As described in the response to Question 2 of Reference 5 and NUREG*0693, this 5 and NUREG-0693, this application of application of the the Lake*Hefner Lake-Hefner wind windfunction functionisisconservative conservative-- decreases decreases the theamount amountofof energy lost to the environment environment from the UHS water when the the UHS UHS temperature temperatureisiswithin within 2.5°F ofof the the natural natural UHS UHStemperature.

temperature. ReferenceReference 33 describes describesthe theuse useofofthetheLakeLakeHefner Hefner wind function for wind function for aa natural natural water surface surface andanduse useofofthe theRyanRyanwindwindfunction functionfor forananartificially artificially heated water water surface.

surface. LSCS's LSCS'sUHS UHSwould wouldbe beconsidered consideredananartificially artificially heated heatedwater watersurface surface at the beginning of of the the design event due due to to either either thethe residual residual normal normal plantplant heat heatrejection rejection to to the UHS or the forced UHS initial temperature UHS or the forced UHS initial temperature used in LAKET*PC. used in LAKET-PC.

Application of Application ofthethe Lake*Hefner Lake-Hefner wind wind function function is is not part of the NUREG-0693 NUREG*0693 described described methodology. NUREG-0693 methodology. NUREG*0693 states, states,ininpart, part,"The liTheformulation formulation of of the the heat heattransfer transferformulae formulae used has has aanumber numberof ofbuilt-in built*in conservatisms, which which tend to to overestimate overestimate pond pond temperature.

temperature.

One of the larger conservatisms conservatisms isis the the choice choice of of aa wind wind dependence dependencef(U). f(U). The TheBrady Bradywind wind function employed function employed seems seems to underestimate underestimate the evaporative flux, even when comparedto the evaporative flux, even when compared to own data. Brady's Brady's own Brady'swind wind function function is is derived derived empirically empirically from from large large lake data. AA more more accurate, but but less lessconservative conservativeformula formulaby byRyan Ryanon onfirmer firmer physical physical grounds: (NUREG~0693 grounds:(NUREG-0693 then presents presentsthe theRyanRyanwind windfunction function used usedininthe theexisting existingLAKET-PC LAKET-PC design design analysis).

analysis). This This formulae formulae accounts for an expected expected increase increaseinin natural naturalconvection convection with with increasing pond pond temperature, whereas whereas Brady'sBrady's wind wind function function is not temperature dependent." dependent. The 1I TheLake-Lake-Hefner wind function wind function used in LAKET-PC is similar in LAKET-PC is similar to the to the Brady wind function, but even more wind function, but conservative for low wind speeds low wind speeds as as shown shownas asfollows:

follows:

Brady wind function:

function: f(U) == 70 0.7U 2 70 ++0.7U2 Lake- Hefner wind Lake-Hefner wind function:

function: f(U) = 17U 17U Where U U == wind wind speedspeed LAKET-LAKET-PC PC input input was was altered to use useonlyonlythe theRyan Ryanwind windfunction functionfor forcritical critical periods periods of of interest (approximately the first two days first two days of the event) event) whenwhenperforming performing the thesubject subject Page Page 44 of of 88

ATTACHMENT ATTACHMENT Additional Information Supporting License Amendment Information Supporting Amendment Request Requestto to Revise Revise Technical TechnicalSpecification Specification3.7.3, 3.7.3,"Ultimate IIUltimateHeat HeatSink" Sink ll sensitivity sensitivity evaluations. This This results resultsininthe theevaporative evaporativeand andconductive/convective conductive/convectivecoolingcooling terms remaining remaining consistent consistentwith with the the methodology methodology described describedin in NUREG-0693.

NUREG-0693.

The results ofof the sensitivity evaluation demonstrate LSCS's UHS sensitivity evaluation UHS design basisbasis temperature temperature of 107°F will willnot notbebe exceeded exceeded when the the worst worst environmental environmental period period is is applied starting starting on on June June 22, 22, 2009, 2009, and and continuing continuing for 774 hours0.00896 days <br />0.215 hours <br />0.00128 weeks <br />2.94507e-4 months <br />. The The margin margin to to the the design design temperature temperature ofof 107°F with the initial with the initial UHS UHStemperature temperature at the proposed proposed TS TSlimiting limiting temperature temperature isisshown showninin the following following table:

Table 1 - UHS Temperature Response UHS Temperature Response forfor 18" 18 11 Sedimentation Sedimentation Time ofof Initial UHS Calculated Calculated Day Temperature 774-hour Margin (°F)

(OF)

Design (OF)

(°F) Post to UHS Basis (Proposed Design Design Event TS limit limit +

+ Event Temperature Occurs 0.75°F for Maximum of 107°F.

107°F.

Instrument UHS Uncertainty) Temp Temp(OF)(OF) 00:00 104.53 104.53 104.53 2.47 03:00 102.72 102.72 104.96 2.04 06:00 102.00 105.39 1.61 09:00 103.19 105.69 1.31 12:00 104.75 104.75 105.05 1.95 15:00 104.75 104.75 2.25 18:00 104.75 104.75 2.25 21:00 104.75 104.75 2.25 24:00 104.53 104.53 2.47 Figures 1 and 2 show the response responseof ofthe theUHS UHS for for the design design event eventoccurring occurring at at 0600 0600 for for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> (Figure (Figure 1) and forfor the continuous continuous 774774 hours hours (Figure (Figure 2).2).

Page 5 of 8

ATTACHMENT ATTACHMENT Additional Additional Information Supporting License Information Supporting License Amendment Request Request to to Technical Specification Revise Technical Revise Specification 3.7.3, 3.7.3, "Ultimate "UltimateHeat HeatSink"Sink" Figure Figure 1 -- 48 Hour Hour UHS Response UHS Response 18" 18" Sedimentation, Sedimentation,66AMAM Start, Start, New New Heat Heat Load, Load, Ryan Ryan Wind Wind Function Function 106 104+---------------------------------------------4-------~~----------_4 104 102+-----~~--~--------~~------------------_+------------~~------~

102 u:-

~100+-------------------------~----------------~----------------~----~

~

.aE 8.

E 98+-----------------------------~------------+_--------------------~~

~

96+---------------------------------~------~------------------------~

96 94+-------------------------------------------------------------------~

94 92+-------~----~------~------~------~------~------~------~----~

92 12:00 AM 12:00 AM 6:00AM 6:00 AM 12:00 PM 12:00 PM 6:00 PM 6:00 PM 12:00 AM 12:00 AM 6:00AM 6:00 AM PM 12:00 PM 6:00 PM 6:00 PM 12:00 AM 12:00 AM 6;00 AM 6:00 AM Time Figure 2 - 774 Hour Hour UHS Response

Response

18" Sedimentation, 6AM Start, New Heat Load, Ryan 18" Ryan Wind Function Function 110 105 100 95 t CD 90 e CD 85 c.

E CD I-80 75 70 65 60 00 5 10 10 15 15 20 20 25 25 30 30 Day Day Page 6 of 8 Page

ATTACHMENT ATTACHMENT Additional Information Additional InformationSupportingSupportingLicenseLicense Amendment Amendment Request Request to Revise Technical Specification Revise Specification3.7.3, 3.7.3,"Ultimate "Ultimate HeatHeat Sink" Sink" These results demonstrate These demonstrate the the UHS UHS design design temperature temperatureof of 107°F 107°F will not be will not be exceeded exceeded using the proposed the proposed TS TS limiting limiting initial UHStemperatures initial UHS temperatures of of Attachment 11 Figure Figure 33 of of Reference Reference1.1.

The analytical The analytical modeling modeling includes consideration of the combination of of accident energy transit time through time through the the UHS and the historical historical worst environmental period to create the the maximum maximum anticipated UHS anticipated UHS temperature.

temperature. The Themodel model alsoalsoincludes includesremoval removal of of excessively excessivelyconservative conservative characteristics of characteristics of the the existing existingdesign design analysis analysis described described above (accident energy release and and wind function wind function application).

application). ReferRefer to Reference Reference1,1,Attachment Attachment1,1,"Analysis "AnalysisAssumptions" Assumptions for ll for additional conservative additional conservative assumptions assumptions that thatcontinue continueto toexist existinin this this sensitivity sensitivity evaluation.

evaluation.

The worst The worst 30*day 30-day evaporation evaporation weather weather period period remains remains the the same same as as determined determined in in Reference 1. 1. The Thesensitivity sensitivityevaluation evaluationdetermined determinedaanegligible negligibleeffect effectinininventory inventory loss lossdue due to the changes to changes in in accident accident energy energyrelease releaseand andwind windfunction function application.

application.

Request:

Justify the

b. Justify the constant transit time time across across thethe UHS UHS pond pond thatthat is is used usedin in your your analysis, analysis, since since reduction in reduction in UHS UHS volume volume overover thethe 30-day recovery period would would cause cause transit time to decrease. IfIfthe decrease. thedecrease decreaseinintransit transittime timeisismodeled, modeled,justify justifywhether whetherthe theeffective effective UHS UHS volumes, surfaces, and andtransit transit times times predicted predicted in in Attachment Attachment JJ remainremain applicable.

applicable.

EGC Response to Question 5b: 5b:

The transit time of approximately 30.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> hours given given in in Section Section3.3 3.3ofofL-002457 L-002457(Reference (Reference4)4) refers to the the initial initial transit time immediately following following an an accident. LAKET-PC LAKET-PC takes takesinto into account the decrease decreaseinintransit transittime time due dueto tothe thereduction reductioninin UHS UHS volume.

volume. UHS UHStransit transittime time as taken taken from from the output output of Case Case 3a_6am 3a_6amof ofReference Reference44isispresented presentedininFigureFigure33below.

below.

Please Please note notethatthatLAKET-PC LAKET-PC reports reports transit transit time time inin integer integervalues valuesonly.only.

The total initial initialUHS UHSvolume volumeand andsurface surface area area are reduced due due toto the the transient transient reduction reduction in in UHS volume inventory.

UHS volume inventory. The effective effective UHS UHS volume volume and and surface surface area are are subsequently subsequently reduced by by constant constant effective effective percentages percentagesdetermined determinedininAttachment Attachment JJof of Reference Reference4.4.

Changes in Changes in UHS UHS volume and surface surface area occur evenly over the entire UHS; therefore, area occur evenly over the entire UHS; therefore, the the effective UHS volumes effective UHS volumes and and surfaces percentages remain applicable.

percentages remain applicable.

Page Page 77 of of 88

ATTACHMENT ATTACHMENT AdditionalInformation Additional InformationSupporting SupportingLicenseLicenseAmendment AmendmentRequest Request to to Revise Technical Specification Revise Specification3.7.3,3.7.3,"Ultimate IIUltimate Heat Heat Sink" Sink ll Figure Figure 33 -- UHS UHS Transit Transit TimeTime Following Following Accident Accident 357 30 30~ _ _----------------------------------------------------~

25 25~----------~-- __--------------------------------------~

!201-------------------------------~--__----------~--------~

CD e

i=

.1::

~

~15~--------------"--------~------------------------------~

0 O~------~------~------~------~------~------~------~

o 0 5 10 15 20 20 25 25 30 30 35 35 Days Following Pays Following Accident Accident

References:

Letter from 1)

D. M.Letter Gullottfrom (Exelon Generation D. M. Gullott Company, (Exelon Generation LLC)LLC)

Company, to U. to S. Nuclear U. S. Nuclear Regulatory Commission, IIRequest for a License Commission, "Request License Amendment Amendment to to LaSalle LaSalle County County Station, Station, Specification 3.7.3, Units 1 and 2, Technical Specification 3.7.3, 'Ultimate

'Ultimate HeatHeat Sink,"'

Sink,'11 dated dated July July12, 12,2012 2012

2) Letter from from D. M. Gullatt D. M. Gullott (Exelon (Exelon Generation Generation Company, Company, LLC) LLC) to U. u. S.S. Nuclear Nuclear Regulatory Commission, "Supplemental "Supplemental Information Information Related Related toto License LicenseAmendment Amendment Request to Request to LaSalle LaSalle County County Station, Station,Units Units11and and22Technical TechnicalSpecification Specification3.7.3, 3.7.3,'Ultimate

'Ultimate Heat Sink,"' dated September Sink,1II dated September 17, 17, 2012 2012 3)

3) MIT Report 161, "An MIT Report Analyticaland "An Analytical and Experimental Experimental Study of of Transient Cooling Pond Pond Behavior,"

Behavior," Ryan Ryan and Harleman, Massachusetts MassachusettsInstitute Instituteofof Technology, Technology, Cambridge Cambridge Massachusetts, Massachusetts, 1973 1973 4)

4) Calculation Calculation L-002457, L-002457, "LaSalle "LaSalle County County Ultimate Ultimate Heat Heat Sink Sink Analysis,"

Analysis," Revision Revision 77 5)

5) Letter Letter fromfrom P. R. Simpson Simpson (Exelon (Exelon Generation Generation Company, Company,LLC) LLC) to u. S.

to U. S. Nuclear Nuclear Regulatory Commission, Regulatory "ResponsetotoRequest Commission, "Response Requestfor forAdditional AdditionalInformation InformationRelated Relatedtoto License Amendment License Amendment Request RequesttotoTechnical TechnicalSpecification Specification3.7.3,3.7.3,'Ultimate

'UltimateHeatHeatSink,"'

Sink,"'

dated January 18, dated January 18, 2013 2013 Page88of Page of 88