ML15125A319

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3/18/2015, Meeting Slide for Tennessee Valley Authority Presentation on GDC 5 Strategy for Watts Bar Unit 2
ML15125A319
Person / Time
Site: Watts Bar Tennessee Valley Authority icon.png
Issue date: 03/18/2015
From:
Tennessee Valley Authority
To:
Plant Licensing Branch II
Minarik A J, NRR/DORL/LPLWB, 415-6185
Shared Package
ML15125A344 List:
References
Download: ML15125A319 (12)


Text

General Desi g n Criterion 5 gLicensing Open Item 91 -GDC-5

  • TVA should update the FSAR with information describing how WBN Unit 2 meets GDC 5, assuming the worst case single failure and a Loss of Offsite

Power"*GDC 5 -Sharing of structures, systems, and components.Structuressystemsandcomponentsimportanttosafetyshallnotbeshared Structures , systems , and components important to safety shall not be shared among nuclear power units unless it can be shown that such sharing will not significantly impair their ability to perform their safety functions, including, in

the event of an accident in one unit, an orderly shutdown and cooldown of thiiit th e rema i n i ng un it s.1 General Design Criterion 5*Design BasisWBN designed as a Hot Standbyplant Standby plant*One unit in accident*Second unit can remain fliHtStdb sa f e l y i n H o t St an db yWBN has the capability to safely handle one unit in an accidentandbringsecondunit accident and bring second unit to cold shutdown within approx

72 hours
8.333333e-4 days
0.02 hours
1.190476e-4 weeks
2.7396e-5 months

2 General Design Criterion 5*ERCW system has 8 pumps serving two units4 train A, 4 train BTwo pumps (on one train) required to safely shutdown two unitsProvides cooling to CCS, Containment Spray, Safety related HVAC, diesel generators, etc.

g*CCS system has 5 pumps and three heat exchangersProvides cooling to Emergency core cooling systems, Residual heat removalheatexchangersspentfuelpoolcoolingetc removal heat exchangers , spent fuel pool cooling , etc.3 General Desi g n Criterion 5 g 4 General Desi g n Criterion 5*Two principal scenarios for GDC5One unit proceeding to Shutdown, Second unit undergoes LOCA gOne unit proceeding to Shutdown, Second unit has emergency Shutdown*Example Limiting LOCA scenario for GDC 5LOCAinoneunitsecondunitprogressingtocoldshutdown LOCA in one unit , second unit progressing to cold shutdownLoss of Offsite PowerFailure of both train A diesels (train A power single failure)Loss of Downstream dam85 oF river water temperature (Technical Specification limit)Heat exchangers -max foulingECRW and CCS Pumps at minimum performance*This results in the single B train CCS heat exchanger (HX-C) serving both the accident and non-accident unit using the C-S CCS pump 5

General Desi g n Criterion 5*Analysis of this limiting event showsAccident unit can be cooled safely gNon-accident unit can be brought to cold shutdown in

72 hours
8.333333e-4 days
0.02 hours
1.190476e-4 weeks
2.7396e-5 months

for GDC 5 complianceLimitation is non -accident unit remains in Hot Standb y (safe shutdown y(state) for

48 hours
5.555556e-4 days
0.0133 hours
7.936508e-5 weeks
1.8264e-5 months

prior to entering RHR coolingAuxiliary feedwater to steam generatorsSteamingfromSteamGenPORVorsafeties Steaming from Steam Gen PORV or safetiesIf non-accident unit is already on RHR in less than

48 hours
5.555556e-4 days
0.0133 hours
7.936508e-5 weeks
1.8264e-5 months

it may be necessary to return unit to Hot StandbyAllowsdecayheattosubsidepriortoaddingloadtoCCSAllows decay heat to subside prior to adding load to CCS 6 General Desi g n Criterion 5*Final Safety Analysis Report was revised describing compliance*Staff RAIs were answered g*Open item closed by NRC in SSER 27*Remaining actionTechnicalSpecificationrevisiontoallowreturntoMode3fornon -accident Technical Specification revision to allow return to Mode 3 for non accident unit for

48 hour
5.555556e-4 days
0.0133 hours
7.936508e-5 weeks
1.8264e-5 months

sRejected by NRC Tech Spec Branch 7

General Design Criterion 5 Options Options1.Do nothing 2CreditUHStemperature 2.Credit UHS temperature below 85 o F3.Credit parallel B CCS pump for non-accident unit with

C-S pump4.Credit adding second ERCW pump to shutdown

unit B EDG 8

General Design Criterion 5 Options Options 5. Credit adding second ERCW pump to shutdown unit A EDGRlt R esu lt s*After reviewing options and several combination of options, the followingwasselected following was selected. *3+4+5-No delay in RHR cooldown. Revised Design

Basis. Acce p table Mar g in for pgDiesel generator while 3 rd ERCW pump loaded 9

General Design Criterion 5 10 General Design Criterion 5

  • Option 3+4+5 gives plant most flexibility*Thin gs to do g*Diesel Generator loading and margin calcs (prelim OK) *Develop Licensing Approach for 3 out of 4 ERCW in Mode 5 (Need both train A and both Train B pumps operable for non-accident unit)*Procedure changes (parallel B CCS pump, 3 rdERCW available in Mode5for48hours)

Mode 5 for

48 hours
5.555556e-4 days
0.0133 hours
7.936508e-5 weeks
1.8264e-5 months

)*20 minute action outside control room (override ERCW interlock) 11 General Design Criterion 5*Mission dose for operator actionFSARchanges(ThreeERCWpumpsrequired)

  • FSAR changes (Three ERCW pumps required--)*System Description changes*U1 and U2 revised Containment Analysis (U2 in-work, initial QA results 3/13/15.)*ReviseERCWandCCSflowanalyses
  • Revise ERCW and CCS flow analyses*Confirm X-tie Valves are useableDCN to Implement new ERCW / CCS Flow Requirements*DCN to install ERCW interlock override (online) 12*Provides side benefit of 90% ERCW acceptability