ML032180348

Meeting Handouts for Meeting to Discuss TVAs Potential Amendment Regarding a Proposed Modification to the Ultimate Heat Sink Temperature

ML032180348
Person / Time
Site:	Watts Bar
Issue date:	08/05/2003
From:	Jabbour K NRC/NRR/DLPM/LPD2
To:
References
TAC MC0106
Download: ML032180348 (19)

Text

NRC FORM 658 U.S. NUCLEAR REGULATORY COMMISSION (9-1999)

TRANSMITTAL OF MEETING HANDOUT MATERIALS FOR IMMEDIATE PLACEMENT IN THE PUBLIC DOMAIN This form is to be filled out (typed or hand-printed) by the person who announced the meeting (i.e., the person who issued the meeting notice). The completed form, and the attached copy of meeting handout materials, wil be sent to the Document Control Desk on the same day of the meeting; under no circumstances will this be done later than the working day after the meeting.

Do not Include proprietary materials.

DATE OF MEETING The attached document(s), which waslwere handed out in this meeting, is/are to be placed 08/05/2003 in the public domain as soon as possible. The minutes of the meeting will be issued in the near future. Following are administrative details regarding this meeting:

Docket Number(s) 50-390 Plant/Facility Name Watts Bar Nuclear Plant, Unit I TAC Number(s) (if available)

MC0106 Reference Meeting Notice Dated July 24, 2003 ADAMS Accession ML032050102 Purpose of Meeting (copy from meeting notice)

To discuss TVA's potential amendment regarding a proposed modification to the ultimate heat sink temperature NAME OF PERSON WHO ISSUED MEETING NOTICE TITLE Kahtan Jabbour Senior Project Manager OFFICE NRR DIVISION DLPM BRANCH PDI1-2 Distribution of this form and attachments:

Docket File/Central File PUBLIC 7i ii NRC FORM 658 (t-1999)

PRINTED ON RECYCLED PAPER This form was designed using InFwms

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Agenda Introduction and Purpose Current UHS Technical Specification (TS) Requirements UHS Temperature History and Challenges UHS / Essential Raw Cooling Water (ERCW) Design Basis Analysis Methodology And Results Precedents Conclusions 2

I

'l Introduction and Purpose Peak river water (ERCW) temperatures in recent summers have approached UHS Limits in Watts Bar Technical Specifications WBN plans to submit a TS Change which will increase UHS temperature limit from 850F to 880 F TS submittal expected August 2003 Approval to be requested before Summer 2004 3

Current UHS TS Requirements LCO 3.7.9 - Ultimate Heat Sink UHS is the TN River, also known as Chickamauga Lake Requires UHS to be Operable in Modes 1-4 Surveillance Requirement (SR) 3.7.9.1 (Perform every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />):

"Verify average water temperature of the UHS is < 850F" Surveillance Instruction (SI) SI-0-2B

• Temperature measured daily (with installed instrumentation) at each of four supply headers in the Auxiliary Building, indicated on the plant computer, averaged, and compared to the limit

• Current limit is < 84TF to account for instrument uncertainty (more accurate instrumentation is being installed)

• Limit is close to 85TF if using precision M&TE 4

UHS Temperature History & Challenges E

The region is generally experiencing hotter than normal summers RSO&E Monitoring Station Intake Water Temperature for WBN 90

-Maxdmum 1996-2002 U TYUIN Ma~~~~~~~-Wimum 1996-2002 August 2, 2002 UHS

-inmum 1996 2002 temperature approached T/S

80.

limit of 850F 70 1.4....

Maximum general river water temperatures for 1996-2002 approximately 83F E

0 TVA River Systems Operations can 50 manipulate river temperature by special operations of larger &

cooler upstream reservoirs, but with 40 limited success 30 Jin Fb M.,

A 4,

May iJun i

Aug Sep Out Nun i eu Can involve significant operating expenses &

coordination difficulties with unpredictable results -

influenced by weather 5

UHS/ERCW Design Basis UHS - Defined as the TN River, including the TVA controlled dams upstream of the intake structure, Chickamauga Dam (nearest downstream dam), and the plant intake channel (Reference WBN UFSAR Section 9.2.5)

Provides a heat sink for removing heat from safety-related components during transients or accidents as well as normal operation The maximum UHS temperature of 850F ensures adequate heat load removal capacity for a minimum of 30 days after reactor shutdown or following an accident, including worst case LOCA The system is designed in accordance with RG-1.27, Revision 1, March, 1974 6

UHS/ERCW Design Basis Design basis of ERCW is for one train (2 ERCW pumps & associated piping, etc.) in conjunction with component cooling, containment spray, & RHR to remove core decay heat following a LOCA Assumes simultaneous LOCA, with loss of downstream dam, loss of offsite power, with a worst case single failure Design basis worst case lake level assumptions have not changed - Assumes Watts Bar Hydro water release of 2,000 CFS Maximum post-accident LOCA heat load occurs approximately 20 minutes after accident Worst-case heat load results during RHR cool-down following shutdown from 100 percent power UHS impacts post-LOCA containment pressure response UHS and ERCW design basis requirements continue to be satisfied with the subject change in TS temperature limit from 850F to 880F 7

UHS/ERCW Design Basis WBN Design Bases will be revised to reflect UHS limit of 880F for:

Containment Accident Analysis

• Containment integrity analysis

• Long-term cooling analysis Residual Heat Removal Cooldown Analysis WBN Design Bases will continue to reflect UHS limit of 850 for:

UHS Design ERCW Design Future modifications will address impact of revised UHS limit of 880F 8

Simplified Diagram - Primary ERCW Users I Return 88 OF Discharge IF 4

4' 9

Analysis Methodology and Results Containment Pressurization Re-analysis Westinghouse performed based on 88TF ERCW No changes in analysis assumptions or methods ERCW is a minor contributor during ice melt phase Pressure increased from 10.64 psig to 10.90 psig Insignificant reduction in ice melt time (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> nominal)

Containment Cooling Re-analysis Westinghouse performed based on 88TF ERCW No changes in analysis assumptions or methods Results acceptable - No long-term impact on equipment environmental qualification 10

1 Containment Pressure

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Analysis Methodology and Results Residual Heat Removal (RHR) - Shutdown And Cooldown Westinghouse performed based on 880F ERCW No changes in analysis methods; Revised assumptions/procedural controls Required (See Below) 2 Train cooldown within 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> of shutdown can be achieved 1 Train cooldown within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> of shutdown (as required by Tech Specs) can be achieved if:

• Remaining RCP secured at 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> after shutdown

• Securing RCP during cooldown is consistent with current operational practices during a Loss of Offsite Power event

• SFP heat exchanger isolation limited to five hours (Previously 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br />) 13

Analysis Methodology and Results Evaluation of Other Major Components Three critical areas were evaluated for impact:

• Major safety related component heat transfer adequacy

• Room / Area cooling capability

• Impact on piping and piping support analyses Margin was obtained using ERCW flows based on pre-operational test data, where necessary The lowest preoperational test flow value was used (either from Appendix R or LOCA test configuration)

Sensitivity studies were performed on Aux Building temperature using TMG analysis Piping / support analyses were evaluated at revised higher temperatures; significant margin existed in the few civil problems in which the analyzed temperature was exceeded.

Cooling capability analytically evaluated for Emergency Diesel Generators, Component Cooling System A, Containment Spray System Hx Additional margin realized but not credited based on updated dam breach criteria. Resulted in revised WBH water release of 14,000 CFS, additional 7 feet of head above analysis basis.

14

Analysis Methodology and Results Results - Evaluation of Other Major Components Emergency Diesel Generator Jacket Water Heat Exchanger (Hx) Cooling Analysis performed at 880F ERCW - results were sensitive to fouling assumptions Analysis utilized ERCW flow margin, a relaxed maximum temperature limit, and revised maximum heat loads Marginal performance at design fouling at 850F Analysis performed using actual fouling trends over a cleaning cycle period Annual spring cleaning of EDG Hx will result in acceptable summer operation at 880F (procedure change planned)

Room/Area Cooling - Safety Related Chillers SR Chillers are greatly oversized; therefore a loss of efficiency was not a concern MCR & EBR chillers (screw compressors) were determined to be acceptable up to 950F Safety-Related Equipment Room & Area Coolers - Acceptable based on margins for ERCW flow and more accurate heat loads SDBR chiller compressors require re-gearing:

• 880F ERCW was determined by vendor to be unacceptable for SDBR chiller operation

• Effort underway to re-gear and derate the SDBR chiller and revise design

-basis documentation

• Both compressors to be rebuilt before 880F TS is implemented 15

Analysis Methodology and Results Environmental Qualification 100 days is still assumed for EQ; however, margin is realized due to hypothetical nature of ERCW temperature remaining elevated at 880F for a 100 day duration TMG analysis of Auxiliary Building areas - Maximum EQ temperature not exceeded Maximum containment temperature not impacted based on Westinghouse analysis No impact on EQ Binders or program Other Major Areas Evaluated Acceptably Acceptable evaluation results achieved for the following:

ERCW Design Basis Events (LOOP, SBO, pipe breaks, etc.)

Auxiliary Feedwater Appendix-R Safe Shutdown Spent Fuel Pool Cooling Flood Mode Operations Tritium Production 16

Precedents TVA reviewed the submittals approved for Cooper, Palisades, and Braidwood WBN approach is similar TVA's submittal will addresses evaluation/analytical methods, assumptions, results TVA's submittal to provide detail list of components/calculations affected and basis for conclusions TVA reviewed TSTF-330 (Adoption of 24-hour temperature averaging) for UHS - Does not provide adequate relief for postulated, sustained high temperature conditions for UHS 17

Conclusions WBN will submit a TS Change to increase UHS temperature from 850F to 880F Effects of proposed change have been examined in detail on equipment, components, systems, and safety-analyses. Included reviews of over 140 design documents and calculations Analysis methodologies and assumptions for major analyses (Containment and RHR cool-down) have not changed Component evaluations considered available margins and included sensitivity studies Modification of SDBR chiller compressors required prior to implementation Procedural controls to be revised as required (e.g., single-train RHR cool-down)

Emergency Diesel Generators will require annual spring cleaning Proposed change is acceptable. No adverse affect on the safety of plant operations or the public 18