RS-11-010, Response to Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink

Response to Request for Additional Information Related to License Amendment Regarding Ultimate Heat Sink

ML110310612
Person / Time
Site:	Byron
Issue date:	01/31/2011
From:	Hansen J Exelon Generation Co, Exelon Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-11-010, TAC ME1669, TAC ME1670
Download: ML110310612 (6)

Text

Exelon Generation Exelon 4300 Generation Winfield Road 4300 Winfield Road www.exeloncorp.com www.exeloncorp.com Nuclear Nuclear Warrenville, IL Warrenville, IL 60555 60555 RS-11-010 RS-11-010 10 CFR 10 CFR 50.90 50.90 January January 31, 31, 2011 2011 U.S. Nuclear Regulatory U.S. Nuclear Regulatory Commission Commission ATTN: Document ATTN: Document ControlControl Desk Desk Washington, DC Washington, DC 20555-001 20555-001 Byron Station, Units Byron Station, Units 1 1 and and 2 2

Facility Operating Facility Operating License License Nos.

Nos. NPF-37 NPF-37 and and NPF-66 NPF-66 NRC Docket NRC Docket Nos.

Nos. STNSTN 50-454 50-454 and and STN STN 50-455 50-455

Subject:

Response

Response to to Request Request for for Additional Additional Information Information Related Related to to License License Amendment Amendment Regarding Ultimate Regarding Ultimate Heat Heat Sink Sink

References:

1. Letter

1. from P.

Letter from P. R.

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

to u. S. Nuclear Nuclear Regulatory Commission, Regulatory Commission, "License "License Amendment Amendment Regarding Regarding Ultimate Ultimate Heat Heat Sink,"

Sink,"

dated June dated June 30,2009 30,2009

2. Letter

2. from P.

Letter from P. R.

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

to u. S. Nuclear Nuclear Regulatory Commission, Regulatory Commission, "Additional "Additional Information Information Supporting Supporting Request Request for for License Amendment License Amendment Regarding Regarding Ultimate Ultimate Heat Heat Sink, Sink, dated II II dated January January 25, 25, 2010 2010

3. Letter

3. from J.

Letter from J. L.

L. Hansen Hansen (Exelon (Exelon Generation Generation Company, Company, LLC) LLC) to u. S.

to u. S. Nuclear Nuclear Regulatory Commission, Regulatory Commission, "Additional'nformation "Additional'nformation Supporting Supporting Request Request for for License Amendment License Amendment Regarding Regarding Ultimate Ultimate Heat Sink,1I dated Heat Sink,1I dated July July 1,2010 1,2010

4. Letter

4. from J.

Letter from J. L.

L. Hansen Hansen (Exelon (Exelon Generation Generation Company, Company, LLC) LLC) to u. S.

to u. S. Nuclear Nuclear Regulatory Commission, Regulatory Commission, "Additional "Additional Information Information Supporting Supporting Request Request for for License Amendment License Amendment Regarding Regarding Ultimate Ultimate Heat Heat Sink,"

Sink," dated November 8, dated November 8, 2010 2010

5. Letter

5. from N.

Letter from N. J.

J. DiFrancesco DiFrancesco (U.(U. S.

S. Nuclear Nuclear Regulatory Regulatory Commission)

Commission) to to M. J.

M. J. Pacilio Pacilio (Exelon (Exelon Generation Generation Company, Company, LLC),

LLC), "Byron "Byron Station, Station, Unit Unit Nos.

Nos. 1 1 and 2 and 2 -- Request Request For For Additional Additional Information Information Related Related toto License License Amendment Amendment Regarding Ultimate Regarding Ultimate Heat Heat Sink Sink (TAC (TAC Nos.

Nos. ME1669 ME1669 and and ME1670),"

ME1670)," dated dated December 28, December 28, 2010 2010 In Reference 1, In Reference 1, Exelon Exelon Generation Generation Company, Company, LLC,LLC, (EGC)

(EGC) requested requested a a license license amendment amendment for for Byron Station, Byron Station, Units Units 11 and and 2, 2, to to revise revise Technical Technical Specifications Specifications (TS)

(TS) to to add add additional additional essential essential service water service water (SX) (SX) cooling cooling tower tower fanfan requirements requirements asas aa function function ofof SX SX pump pump discharge discharge temperature to temperature to reflect reflect results results ofof aa revised revised analysis analysis for for the the ultimate ultimate heat heat sink sink (UHS).

(UHS).

EGC supplemented EGC supplemented Reference Reference 1 1 by by letters letters dated dated January January 25, 25, July July 1, 1, and November 8,2010 and November 8,2010 (References (References 2, 2, 3, 3, and and 4).

4).

January January 31, 2011 31, 2011 U. S.

U. S. Nuclear Nuclear Regulatory Regulatory Commission Commission Page 2 Page 2 In Reference In Reference 5, 5, the the NRC NRC requested requested that that EGC EGC provide provide additional additional information information in in support support of of its its review review of of Reference Reference 1. 1. Attachment Attachment 1 1 provides provides thethe requested requested information, information, with with the the exception exception of of Question 1.a Question 1.a of of Reference Reference 5. 5. As As discussed discussed withwith the the NRC NRC on on January January 27,2011, 27,2011, a a separate separate submittal will submittal will be be required required to to provide provide additional additional information information basedbased on on aa conference conference callcall held held on on January 20, January 20, 2011, 2011, between between the the NRC NRC andand EGC.

EGC. This This separate separate submittal submittal will will include include a a revision revision to to TS 3.7.9 TS 3.7.9 and and the the revised revised markup markup ofof the the TS TS 83.7.9 83.7.9 8ases.

8ases.

EGC has EGC has reviewed reviewed the the information information supporting supporting a a finding finding of of no no significant significant hazards hazards consideration consideration and and thethe environmental environmental consideration consideration thatthat were were previously previously provided provided to to the the NRC NRC in in Attachment Attachment 1 1 of of Reference 1.

Reference 1. The The additional additional information information provided provided in in this this submittal submittal does does notnot affect affect the the bases bases for for concluding that concluding that the the proposed proposed license license amendment amendment does does notnot involve involve a a significant significant hazards hazards consideration. In consideration. In addition, addition, the the additional additional information information provided provided in in this this submittal submittal does does notnot affect affect the the bases for bases for concluding concluding that that neither neither an an environmental environmental impactimpact statement statement nor an environmental nor an environmental assessment needs assessment needs to to be be prepared prepared inin connection connection withwith the the proposed proposed amendment.

amendment.

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

consultation," paragraph paragraph (b), (b),

a copy of a copy of this this letter letter and and its its attachments attachments are are being being provided provided to to the the designated designated State State of of Illinois Illinois official.

official.

There There are are nono regulatory regulatory commitments commitments contained contained in in this this letter.

letter. Should Should youyou have have anyany questions questions concerning this concerning this letter, letter, please please contact contact Ms.

Ms. Lisa A. Schofield Lisa A. Schofield at at (630)

(630) 657-2815.

657-2815.

II declare declare under under penalty penalty of of perjury perjury that that the the foregoing foregoing is is true true and and correct.

correct. Executed Executed on on the the 3131 st st day day of January 2011 of January 2011 ..

nsen nsen Manag -- Licensing Manag Licensing Exelon Generation Exelon Generation Company, Company, LLC LLC

Attachment:

Response to to Request Request for for Additional Additional Information Information cc:

cc: NRC Regional NRC Regional Administrator, Administrator, Region III Region III NRC Senior Resident NRC Senior Resident Inspector, Inspector, 8yron 8yron Station Station NRC Project NRC Project Manager, Manager, NRR NRR -- 8yron 8yron Station Station Illinois Emergency Illinois Emergency Management Management AgencyAgency -- Division Division of of Nuclear Nuclear Safety Safety

ATTACHMENT ATTACHMENT

Response

Response to to Request Request for for Additional Additional Information Information By By letter letter to to the the Nuclear Nuclear Regulatory Regulatory Commission Commission (NRC) (NRC) dated dated June June 30, 30, 2009, 2009, Exelon Exelon Generation Generation Company, Company, LLC, LLC, (EGC)

(EGC) requested requested a a license license amendment amendment for for Byron Byron Station, Station, Units Units 1 1 and and 2,2, to to revise Technical revise Technical Specifications Specifications (TS) (TS) toto add add additional additional essential essential service service water water (SX)

(SX) cooling cooling tower tower fan requirements fan requirements as as aa function function of of SX SX pump pump discharge discharge temperature temperature to to reflect reflect results results ofof a revised a revised analysis for analysis for the the ultimate ultimate heat heat sink sink (UHS).

(UHS). EGC EGC supplemented supplemented this this request request byby letters letters dated dated January 25, January 25, July July 1,1, and November 8,2010.

and November 8,2010.

In a In a letter letter dated dated December December 28, 28, 2010, 2010, the the NRC NRC requested requested that that EGC EGC provide provide additional additional information related to information related to the the June June 30, 30, 2009, 2009, request.

request.

NRC Question NRC Question 1: 1:

The The EGCEGC request request dated dated June June 30,2009, 30,2009, provided provided revisedrevised TS TS 3.7.9, 3.7.9, IIUltimate IIUltimate Heat Heat Sink,"

Sink," andand revised TS the revised the TS B3.7.9 B3.7.9 Bases Bases for for a a cross cross tied tied SX SX system.

system. The The letter letter dated November 8,2010, dated November 8,2010, includes new includes new proposed proposed TS TS 3.7.9 3.7.9 for for split split SXSX system, system, but but did did not not include include thethe new new TS TS Bases.

Bases.

a) Please a) Please provide provide the the complete complete TS TS B3.7.9 B3.7.9 BasesBases for for clarity.

clarity.

b) Please b) Please explain explain why why and and how how oftenoften the the SXSX trains trains are are operated operated splitsplit for for one one and/or and/or bothboth units.

units.

Response to Response to Question Question 1.a: 1.a:

The response The response to to Question Question 1.a 1.a will will be be provided provided in in aa separate separate submittal.

submittal.

Response to Response to Question Question 1.b: 1.b:

The SX The SX trains trains are are not not normally normally operated operated with with thethe trains trains split.

split. The The normal normal operating operating procedures procedures do not contain do not contain steps steps forfor operations operations with with the the trains trains split.

split. The The SX SX trains trains maymay bebe split split to to support support maintenance or maintenance or in in response response to to postulated postulated flood events caused flood events caused by by leakage leakage from from SX SX piping.

piping. A A review of review of the the Operating Operating Logs Logs and and Maintenance Maintenance Rule Rule Program Program data data indicated indicated no no occurrences occurrences of of SX trains SX trains split split concurrent concurrent with with a a service service water water cooling cooling tower tower (SXCT)

(SXCT) cell cell out out of service or of service or inoperable in inoperable in the the last last three three years.

years.

NRC Question NRC Question 2: 2:

The uprate heat The uprate heat load load forfor the the scenarios scenarios presented presented in in the the letter letter dated November 8,2010, dated November 8,2010, for for the the scenarios where scenarios where SX SX isis split, split, show show a a constant constant heat heat loadload to to the the UHS UHS for for approximately approximately the the first first 19 minutes 19 minutes afterafter loss-of-coolant loss-of-coolant accident.accident. These These heat heat loads loads differ differ from from the the heat heat loads loads inin the the scenarios presented scenarios presented in in your your letter letter dated dated JuneJune 30, 30, 2009.

2009. The The staff staff recognizes recognizes differences differences in in heat heat loads to loads to the the UHS UHS basedbased on on one one train train ofof SX SX in in the the letter letter dated November 8, dated November 8, 2010, versus two 2010, versus two trains of trains of operating operating SX SX in in your your letter letter dated dated JuneJune 30, 30, 2009.

2009.

a) Please a) explain the Please explain the reasons reasons for for differences differences in in the the heat heat load load profiles profiles forfor your your letters letters dated dated June 30, June 30, 2009, 2009, and November 8, and November 8, 2010.

2010.

b) Please b) explain why Please explain why the the heat heat loadload isis constant constant in in your November 8,2010, your November 8,2010, submittal submittal for for the the first 19 first 19 minutes, minutes, whereas whereas the the corresponding corresponding heat heat loadload forfor the the first first 19-20 19-20 minutes minutes is is not not constant for constant for the the scenarios scenarios in in the the letter letter dated dated JuneJune 30,2009.

30,2009.

Page 1 Page 1 ofof 44

ATTACHMENT ATTACHMENT Response to Response Request for to Request for Additional Additional Information Information Response to Response to Question Question 2.a: 2.a:

The EGC The EGC letters letters dated dated JuneJune 30,2009, 30,2009, and and November November 8,2010, 8,2010, provided provided analysis analysis for for different different scenarios.

scenarios. The The June June 30, 30, 2009, 2009, letter letter provided provided scenarios scenarios associated associated with with postulated postulated passivepassive breaker failures breaker failures that that result result inin the the loss loss ofof two two SXCT SXCT fans. fans. The The November November 8, 8, 2010, 2010, letter letter provided provided additional analysis additional analysis withwith scenarios scenarios associated associated with with the the SXSX trains trains separated separated and and a a failure failure of of one one of the of the SX SX pumps pumps or or EDG EDG on on the the accident accident unit unit resulting resulting in in SX SX flowflow to to only only one one train train of of the the SXSX system and system and oneone cooling cooling tower.

tower.

The following The following differences differences exist exist between between the the two two heat heat load load profiles:

profiles:

i)i) For For thethe June June 30,2009, 30,2009, heat heat loadload profile, profile, the the accident accident unit unit heat heat load load isis based based on on four four reactor containment reactor containment fan fan coolers coolers (RCFCs)

(RCFCs) in in operation operation for for the the first first 1,299 1,299 seconds seconds (21.6 minutes). At (21.6 minutes). At 1,299 1,299 seconds, seconds, operatoroperator actionaction is is assumed assumed to to shed shed heatheat loadload by by securing two securing two ofof the the four four RCFCs, RCFCs, which which reduces reduces the the accident accident unitunit heat heat input input rate.

rate. For For the the November 8,2010, November 8,2010, heat heat load load profile, profile, thethe SX SX trains trains areare separated, separated, and and a a failure failure is is assumed, which assumed, which results results in in SXSX flow flow to to only only one one train train of of equipment equipment on on the the accident accident unit. unit.

Thus, the Thus, the accident accident unit unit heat heat loadload isis based based on on only only twotwo RCFCs RCFCs in in operation operation for for thethe event.

event.

ii) For ii) For thethe June June 30,2009, 30,2009, heat heat loadload profile, profile, the the accident accident unit unit heat heat load load isis based based on on safety safety injection switchover injection switchover to to cold cold leg leg recirculation recirculation at at 695 695 seconds seconds (Le., (Le., RHRH HX HX heat heat input input toto the the UHS starts UHS starts at = 695 at tt = 695 seconds).

seconds). For For the the November November 8,2010, 8,2010, heat heat load load profile, profile, only only one one train of train of ECCS ECCS is is operating operating which which delays delays switchswitch over.

over. With With oneone train train ofof ECCS ECCS in in operation operation during the during the injection injection phase, phase, the the switchover switchover time time andand RH RH HX HX input input toto the the UHS UHS startsstarts atat tt ==

1110 seconds.

1110 seconds.

Response to Response to Question Question 2.b: 2.b:

For the For the November November 8, 8, 2010, 2010, heat heat load load profile, profile, thethe RCFC RCFC heat heat loadload was was conservatively conservatively assumed assumed to be constant to be constant untiluntil the the start start of RH HX of RH HX input input (i.e.,

(i.e., safety safety injection injection switchover switchover to to cold cold leg leg recirculation). With recirculation). With twotwo RCFCs RCFCs in in operation, operation, the the LOCA LOCA Mass Mass and and Energy Energy Analysis Analysis indicates indicates that containment that containment steam steam temperatures temperatures and and RCFCRCFC heat heat removal removal rates rates are are relatively relatively constant constant untiluntil RH HX the RH the HX is is placed placed in in service.

service. Whereas, Whereas, for for the the June June 30, 30, 2009, 2009, heatheat load load profile, profile, with with four four RCFCs in RCFCs in operation, operation, the the LOCA LOCA Mass Mass and and Energy Energy Analysis Analysis indicates indicates the the containment containment steam steam temperature drops temperature drops from from a a peak peak of of approximately approximately 261 261 °° FF to to approximately approximately 208.3° 208.3° F F atat 1,199 seconds 1,199 seconds (20 (20 minutes).

minutes). The The following following plot plot shows shows the the containment containment steam steam temperature temperature for for the two the two cases.

cases.

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ATTACHMENT ATTACHMENT

Response

Response to to Request Request for for Additional Additional Information Information Containment Steam Containment Steam Temperature Temperature 160 160 140 140 120 120 +----~--'-~-+--~<...---J.~-t--'--~~__+_~-'--~"__t~---'--~~~~~_'___1 o

o 200 200 400 400 600 600 800 800 1000 1000 1200 1200 Time (seconds)

Time (seconds)

The RCFC The RCFC heat heat removal removal raterate varies varies with with thethe temperature temperature difference difference betweenbetween the the SX SX water water temperature temperature and and the the containment containment steam steam temperature.

temperature.

NRC Question NRC Question 3: 3:

The proposed The proposed TS TS Limiting Limiting Condition Condition forfor Operation Operation (LCO) (LCO) 3.7.9 3.7.9 use use "SX "SX pump pump discharge discharge temperature region,1I to temperature region,1I to define define the the LCO.

LCO. As As this this temperature temperature varies, varies, the the requirements requirements of of the the LCO change LCO change and and require require operator operator action.

action.

a) Please a) explain how Please explain how the the operators operators willwill become become aware aware that the IISX that the IISX pump pump discharge discharge temperature region,1I temperature region,1I has has changed changed and and that that operator operator action action is is necessary.

necessary.

b) Indicated b) Indicated SX SX pump pump discharge discharge temperature temperature may may be be different different than than actual actual temperature. temperature. How How has the has the temperature temperature instrument instrument andand looploop uncertainty/inaccuracy uncertainty/inaccuracy been been factored factored into into the the proposed TS proposed TS LCO LCO revision?

revision?

Response to Response to Question Question 3.a: 3.a:

SX pump discharge SX pump discharge temperature temperature is is monitored monitored by by the the control control room room operators.

operators. Each Each Unit Unit Nuclear Nuclear Station Operator Station Operator monitors monitors SX SX pump pump discharge discharge temperature temperature during during control control board board walk walk downs.

downs.

The upper The upper limit limit of of green green band band for for the the control control board board temperature temperature indicators indicators is is currently currently set set at at F, which 78° F, 78° which is is at at the the current current SX SX pump pump discharge discharge high high temperature temperature alarm alarm of of 78° 78° F.

F. In In response response to changing to changing temperatures temperatures the the operators operators utilize utilize procedural procedural guidance guidance to to taketake the the appropriate appropriate action(s) to action(s) to control control basin basin temperatures.

temperatures.

Page 3 Page 3 of of 44

ATTACHMENT ATTACHMENT

Response

Response to to Request Request for for Additional Additional Information Information Procedure OBOSR Procedure OBOSR 0.1-0, 0.1-0, "UNIT "UNIT COMMONCOMMON ALL ALL MODES/ALL MODES/ALL TIMES TIMES SHIFTL SHIFTLY Y AND AND DAILY DAILY OPERATING SURVEILLANCE," implements OPERATING SURVEILLANCE," implements Surveillance Surveillance Requirement Requirement (SR) (SR) 3.7.9.2.

3.7.9.2. Although Although the required the required SR SR frequency frequency is is 2424 hours0.0281 days <br />0.673 hours <br />0.00401 weeks <br />9.22332e-4 months <br />, hours, the the SX SX pump pump discharge discharge temperatures temperatures are are currently currently verified as verified as acceptable acceptable threethree times times per per day.

day.

Control room Control room alarms alarms 1-2-B2 1-2-B2 and and 2-2-B2, 2-2-B2, "SX "SX Pump Pump Discharge Discharge Header Header Temperature Temperature High High Low,"

Low,"

currently provide a currently provide a high high temperature temperature alarm alarm at at 78° 78° F. F. The The current current alarm alarm setpoint setpoint waswas selected selected to to alert operators alert operators of of high high pump pump discharge discharge temperatures temperatures prior prior to to reaching reaching the the current current Technical Technical Specifications temperature Specifications temperature limit limit ofof 80° 80° F F where where action action isis needed needed to to run run all all required required cooling cooling tower tower fans on fans on high high speed.

speed.

It should It should be be noted noted that that during during normal normal operation operation the the heat heat load load onon the the SXCT SXCT is is relatively relatively constant.

constant.

Thus ifif no Thus no changes changes are are made made to to the the tower tower configuration configuration the the SXSX pump pump discharge discharge temperature temperature tends to tends to follow follow the the outside outside airair wetwet bulb bulb temperature.

temperature. Outside Outside air air wet wet bulb bulb temperature temperature changes changes are relatively are relatively slow slow providing providing adequate adequate time time for for the the operators operators to to recognize recognize and and toto take take action action to to put additional put additional SXCTSXCT fansfans into into service service when when needed.

needed.

The The SX SX pump pump discharge discharge header header temperature temperature high high alarm alarm setpoint setpoint will will be be evaluated evaluated and and potentially changed potentially changed duringduring implementation implementation of of the the revised revised Technical Technical Specifications.

Specifications.

Response to Response to Question Question 3.b: 3.b:

As described As described in in the the EGCEGC June June 30,2009, 30,2009, License License Amendment Amendment Request:Request:

To ensure To ensure thatthat the the actual actual UHS UHS temperature temperature does does not not exceed exceed the the TSTS surveillance surveillance limit, limit, the surveillance procedure the surveillance procedure used used to to demonstrate demonstrate compliance compliance with with the the TSTS surveillance surveillance limit will limit be revised will be revised toto accommodate accommodate instrument instrument uncertainty.

uncertainty.

To ensure that To ensure that the the indicated indicated UHS UHS temperature temperature does does notnot exceed exceed the the TS TS surveillance surveillance limit, limit, temperature corrections temperature corrections havehave been been factored factored intointo the the UHS UHS surveillance surveillance procedures.

procedures. The The SXSX pump discharge pump discharge temperatures temperatures in in the the current current UHSUHS surveillance surveillance procedures procedures OBOSR OBOSR 0.1-0, 0.1-0, "UNIT "UNIT COMMON ALL COMMON ALL MODES/ALL MODES/ALL TIMES TIMES SHIFTL SHIFTL Y Y AND AND DAILY DAILY OPERATING OPERATING SURVEILLANCE,"

SURVEILLANCE,"

Revision 35, Revision 35, and OBOL 7.9, and OBOL 7.9, "LCOAR "LCOAR ULTIMATE ULTIMATE HEAT HEAT SINK SINK (UHS)

(UHS) TECH TECH SPEC SPEC LCOLCO ## 3.7.9,"

3.7.9,"

Revision 12, Revision 12, were were previously previously reduced reduced by by 2° 2° FF to to account account for for instrument instrument measurement measurement uncertainties. Additionally, uncertainties. Additionally, procedure procedure BOP BOP SX-T2, SX-T2, "SX "SX TOWER TOWER OPERATION OPERATION GUIDELINES,"

GUIDELINES,"

Revision 14, Revision 14, applies applies thethe same same temperature temperature requirements requirements as as the the surveillance surveillance procedures procedures (i.e., the (i.e., the normal normal operating operating procedure procedure has has thethe operators operators keep keep the the indicated indicated basin basin temperature temperature 2° F 2° F below below the the required required Technical Technical Specification Specification temperature).

temperature).

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