ML20155B071

Summary of 880518 Meeting W/Tva Re Resolution of Restart Item Identified as Plant Pra.List of Attendees & Slides Encl

ML20155B071
Person / Time
Site:	Browns Ferry
Issue date:	05/27/1988
From:	Gears G NRC OFFICE OF SPECIAL PROJECTS
To:	NRC OFFICE OF SPECIAL PROJECTS
References
TAC-63178, NUDOCS 8806130068
Download: ML20155B071 (21)

Text

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1. 'o UNITED STATES

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!" c g NUCLEAR REGULATORY COMMISSION 5 W ASHINGTO N, 0, C. 20555 1

/ l May 27, 1988  !

I Docket No. 50-260 LICENSEE: Tennessee Valley Authority FACILITY: Browns Ferry Nuclear Plant, Units 1, 2 and 3 l

SUMMARY

OF MAY 18, 1988 MEETING WITH THE TENNESSEE VALLEY AUTHORITY l (TAC NO. 63178)

On May 18, 1988, members of the Office of Special Projects met with representatives of the Tennesset Valley Authority (TVA or the licensee). The purpose of the meeting was to discuss the resolution of a Restart Item identified as the Browns Ferry's Probabilistic Risk Assessment (PRA).

Specifically, the meeting discussed the staff's letters to the licensee dated October 1, 1987 and May 11, 1988.

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Enclosure 1 is a list of attendees. The slides used by TVA in its presentation are contained in Enclosure 2. j The primary focus of the licensee's presentation was to discuss issues raised by the staff's October 1, 1987 letter. In particular, TVA presented slides with revisions to Tables 1 and 2 of the staff's letter based upon a September 1987 revision to the draft PRA. This draft has not yet been approved by TVA management or subjected to peer review and, therefore, has not been requested or provided to the NRC. The staff's October 1, 1987 letter provided a limited scope review of an earlier draft version of the PRA. The revised Tables from the September 1987 draft PRA showed a substantive reduction in the estimated core melt frequency when compared to the earlier draft version.

The staff's major concern for Unit 2 restart is whether the Browns Ferry plant as modeled in the earlier draft PRA staff is an outlier in terms of core melt frequency when compared to similar plants of similar vintage. The staff believes that resolution of this issue requires a review of the changes in the September 1987 draft PRA as outlined in TVA's presentation (Tables 1 and 2). The staff indicated that timely resolution of its concerns is contingent upon the licensee providing sufficient supporting documentation on the revised Tables 1 and 2 using the revised September 1987 PRA.

The staff requested the following from TVA:

Provide TVA's rationale for concluding that the revised PRA will 4 reflect the configuration of Unit 2 at the time of restart. l Provide a sumary document indicating the changes made between the January 1986 draft PRA reviewed by the staff in its October 1, 1987 l letter and the September 1987 revision. l i

I 8906130060 080527 PDR ADOCK 05000259 P ppy

I May 27, 1988 Because the development of NRC guidance concerning the use of an Individual Plant Examination (IPE) using the 10COR methodology (i.e., licensee's letters dated June 9, 1987 and Febrausry 4, 1988) is still under way, the staff's review and assessment of the above information will be needed prior to restart. The staff and TVA discussed in details the level of informational requirements needed in the above responses. Based upon TVA's understanding of the staff's needs, TVA comitted to provide this infonnation no latar than August 30, 1988. Upon completion of its scoping review of the licensee's submittal, the staff will conduct an audit of the September 1987 revised draft PRA and supporting documentation. This review audit is scheduled to occur approximately one month after the receipt of the licensee's August 30, 1988 submittal.

Gerald E. Gears, Project Manager TVA Projects Division Office of Special Projects

Enclosures:

1. List of Attendees

2. TVA Slides Used in Presentation cc w/ enclosures:

See next page Distribution Docket File NRC PDR Local PDR Those on Attached List i

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$tL TVAfhP SBlack MSims:as 5/ /88 q/88 5/g88 l

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l S a-O c e, DISTRIBUTION FOR MEE_ TING

SUMMARY

DATE0: May 27, 1988 Facility: Browns Ferry Nuclear Plant, Units 1, 2 and 1*

. Docket File...s NRC POR Local POR Projects Reading S. Ebneter J. Axelrad S. Richardson S. Black B. D. Liaw G. Gears D. Moran J. Kelly M. Sims OGC J. Rutberg F. Miraglia E. Jordan '

J. Partlow __

t A. Marinos J. A. Murphy E. Chelliah ACRS(10)

Hon. M. Lloyd Hon. J. Cooper Hon. D. Sundquiest Hon. A. Gore Dr. Henry Myers Mr. R. King, GA0 P. Gwynn J. Scarborough G. Marcus C. Miller >

T. Elsasser C. Ader TVA-Rockville BFN Rdg. File

• cc: Licensee / Applicant and Service List f

IY ENCLOSVRE 1 TVA/NRC MEETING l l

BROWNS FERRY PRA MAY 18, 198 F Name Organization Don L. Williams TVA - DNLRA B. D. Liaw NRC - OSP l I

Gerry Gears NRC - OSP Mark A. Linn TVA - RPS Wang Lau TVA - RPS Phil Polk TVA - Rockville Fred L. Moreadith TVA - Engr. Mgr. I M. J. May TVA - BFN - Licensing Hugo Pomrehn TVA - S.D. - BFN Jane Axelrad NRC - OSP Steve Richardson NRC - OSP Angelo Marinos NRC - OSP ~

J. A. Murphy NRC - RES _

E. Chelliah NRC - RES J. P. Stapleton TVA - 500 I

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. 1 Ef1 CLOSURE 2

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.i j , TVA/NRC STAFF DISCUSSION OF

! THE BROWNS FERRY NUCLEAR PLANT (BFN)

PROBABILISTIC RISK ASSESSMENT (PRA) 1 J .

ROCKVILLE, MARYLAND i

i MAY 18, 1988 i

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',. EFN PRA - TVA/NRC MEETING

. . .i PURPOSE i

i DISCUSS OCTOBER 1, 1987, NRC LETTER AND

! PROVIDE RESPONSES TO TABLES 1, 2, AND 3 i

i IN SUPPORT OF BFN RESTART 1

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BFN PRA - TVA/NRC MEETING i

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1 AGENDA s

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1. INTRODUCTION TVA/NRC l

i i 2. PRESENTATION TVA

,I 3. DISCUSSION TVA/NRC 4

4. CONCLUSION i

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2 MAY 18, 1988

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BFN PRA - IVA/NRC MEETING RESPONSE TO OCTOBER 1. 1987. NRC 1ETTER NRC COMMENT (1) "TilERE IS NO REASON TO SUSPECT TilAT ADDITIONAL IMMEDIATE REGULATORY ACTION IS WARRANTED, BECAUSE Tile PRA DID NOT IDENTIFY SIGNIFICANT SAFETY PROBLEMS. Il0 WEVER, Tile ASSESSED CORE DAMAGE FREQUENCY IS VERY llIGli AND WE ENC 0URAGE RAPID SUBMITTAL OF. Tile REVISED AND UPDATED FINAL PRA."

TVA RESPONSE Tile CURRENT BFN CORE DAMAGE FREQUENCY IS WITilIN INDUSTRY VALUES FOR SIMILAR PLANTS AND IS NOT AN OUTLIER.

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BFN PRA - TVA/NRC MEETING -

RESPONSE TO OCTOBER 1, 1987. NRC IFTTER

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NRC COMMENT (2) "FROM AN INITIAL READING OF Tile PRA, Tile STAFF DID NOT IDENTIFY ANY NEW SIGNIFICANT GENERIC SAFETY ISSUES. Tile STAFF'S FINAL REVIEW 0F i Tile FINAL PRA COULD POTENTIALLY IDENTIFY NEW GENERIC SAFETY ISSUES, IF TilEY EXIST. Il0 WEVER, THIS CONCLUSION IS TENTATIVE AND COULD CilANGE AFTER OUR DETAILED REVIEW."

I TVA RESPONSE NO NEW GENERIC SAFETY ISSUES IIAVE BEEN IDENTIFIED IN Tile CURRENT ANALYSES.

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BFN PRA - TVA/NRC MEETING RESPONSE TO OCTOBER 1. 1987. NRC LETTER

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NRC COMMENT (3) "THE BROWNS FERRY PRA PROVIDES EXTENSIVE SAFETY INFORMATION ON DOMINANT POTENTIAL CORE DAMAGE SEQUENCES. BECAUSE TilESE DOMINANT SEQUENCES ORIGINATE FROM SYSTEM DEPENDENCIES, THE STAFF llAS GAINED A SIGNIFICANT OVERVIEW 0F THE BROWNS FERRY PLANT SAFETY AND UNDERSTANDING OF THOSE IMPROVEMENTS WHICil COULD REDUCE Tile DOMINANT SEQUENCE FREQUENCY."

TVA RESPONSE TVA AGREES TilAT Tile BFN PRA PROVIDES EXTENSIVE INFORMATION REGARDING DOMINANT CORE DAMAGE SEQUENCES AND RISK-IMPORTANT EQUIPMENT. Tills INFORMATION IS BEING USED TO IMPROVE BFN SAFETY AND PERFORMANCE.

MAY 18, 1988

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BFN PRA - TVA/NRC MEEllNG RESPONSE TO OCTOBER 1. 1987. NRC l_ETTER i

NRC COMMENT (4) "OUR INITIAL READING OF Tile PRA INDICATES THAT CORE DAMAGE IS MORE LIKELY TO BE INDUCED BY MEANS OF SCRAM FAILURE EVENTS TilAN BY OTilER EVENTS . . . . BASED ON OUR CURRENT KNOWLEDGE OF lilE ADVERSE CONSEQUENCES OF ATWS INDUCED CORE DAMAGE EVENTS AND MARK I l CONTAINMENT CAPABILITY TO WITilSTAND Tile ATWS EVENTS, IT IS PRUDENT

TO EXPEDITE ATWS RELATED MGDIFICATIONS (USI A-9) AND TO CONSIDER CAREFULLY Tile STAFF'S RECOMMENDATIONS OUTLINED IN TABLE 3."

) TVA RESPONSE i

Tile ATWS EVENTS NO LONGER REPRESENT A SIGNIFICANT CONTRIBUTOR TO CORE MELT FREQUENCY. SCRAM FREQUENCY REDUCTION PROGRAM IS BEING IMPLEMENTED.

SPECIFIC COMMENTS RELATED TO ATWS MODIFICATIONS ARE ADDRESSED IN TVA'S RESPONSE TO TABLE 3.

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BFN PRA - TVA/NRC MEETING RESPONSE TO OCTOBER 1. 1987. NRC IETTER t

NRC COMMENT (S) "WE FIND TilAT Tile AIR SYSTEM (A SUPPORT SYSTEM) PLAYS A MAJOR ROLE IN Tile BROWNS FERRY PLANT OPERATION. Tile PRA INDICATES TilAT IT IS NOT A lilGilLY RELIABLE SYSTEM, AND IT PROVIDES A WIDE RANGE OF INTERSYSTEM LEPENDENCIES RESULTING IN Tile LOSS OF SAFETY FUNCTIONS.

SIMILAR ISSUES RELATED TO AIR SYSTEM PROBLEMS WERE BROUGilT TO Tile ATTENTION OF Tile INDUSTRY AND ARE DOCUMENTED IN "NRC INFORMATION NOTICE NO. 87-28: AIR SYSTEMS PROBLEMS TO U.S. LIGitT WATER REACTORS " DATED JUNE 22, 1987. TilUS, Tile STAFF BELIEVES TilAT TIIE i AIR SYSTEM DEPENDENCIES COULD BE MINIMIZED (REFER 10 TABLE 3 i IMPROVEMENTS) BY DESIGN IMPROVEMENTS, IF NECESSARY."

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i TVA RESPONSE

AIR SYSTEM N'O LONGER PLAYS A MAJOR ROLE IN THE BFN DOMINANT SEQUENCES.

(DISCUSSED FURTilER IN TVA RESPONSE TO ITEM 4 0F TABLE 3).

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BFN PRA - TVA/NRC MEETING l RESPONSE TO OCTOBER 1. 1987. NRC IETTER I

NRC COMMENT (6) "IT APPEARS THAT Tile TVA MANAGEMENT AND ITS STAFF ARE MAKING USE OF j Tile PRA-BASED SYSTEMS INFORMATION TO FACILITATE THE RESOLUTION OF -

Tile PLANT CONFIGURATION MANAGEMENT PROBLEMS AND-T0 ESTABLISil SOME 4

PRIORITIZATION METHODS NEEDED FOR RESOURCE' ALLOCATION PURPOSES.

B0Til Tile TVA AND OSP STAFFS COULD ENCOURAGE AND MONITOR CLOSELY Tile l

USE OF PRA BY THE LICENSEE."

i I TVA RESPONSE PRA CONSIDERATIONS IIAVE BEEN FACTORED INTO BFN RESTART EFFORTS.

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BFN PRA - TVA/NRC MEETING RESUI.TS_

(UPDATE OF TABLE 1 Ci .0Cf0BER 1,1987, NRC LEITER)

, CORE MELT FREQUENCY (EVENT 5/REACf0R YFAR) l JANUARY 86 CURRDff*

! INTERNAL EVINIS 1.5 E-3 4.7 E-4 j

SEISMIC LNEN'IS 1.4 E-4 3.7 E-5 FIRES 1.5 E-4 7.7 E-5 INTERNAL FLOODING 1.2 E-6 1.2 E-6 j

TOTAL 1.8 E-3 5.85 E-4 l

l NO SEQUENCE CONTRIBlffES GREATER TilAN St TO CORE MELT FREQUENCY.

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• SEPTEMBER 1987 REVISION: SUBJECF TO COMPLEfl0N OF TVA MANAGEMENT l- AND PEER REVIEWS.

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UFN PRA - TVA/NRC MEEFING .

DOMINANT SEQUENCES (REVISED TABLE 2 0F OCf0BER 1,1987, NRC LEITER)

FREQUENCY *

1. LOSS OF FEEDWATER TRANSIENT, FAILURE OF llPCI 2.25 E-5/ YEAR AND RCIC, FAILURE OF MANUAL ADS BLOWDOWN, ELECTRIC POWER STATE 16, CAS STATE 1. NO RECOVERY.

,I 2 SMALL LOCA, FAILURE OF TORUS COOLING, ELECTRIC 2.05 E-5/ YEAR POWER SfKfE 16, CAS STATE 1, NO RECOVERY .

3. MAIN STEAM ISOLATION VALVE CLOSURE, FAILURE OF 2.04 E-5/ YEAR llPCI AND RCIC, FAILURE OF MANUAL ADS DLOWDOWN, 4

ELECTRIC POWER STATE 16, CAS STATE 1, NO RECOVERY

4. TRANSIENT WITil 1-3 SIUCK OPEN RELIEF VALVES, 1.58 E-5/ YEAR FAILURE OF TORUS COOLING, ELECTRIC POWER STATE 16, CAS STATE 1, NO RECOVERY

5. LOSS OF OFFSITE POWER, FAILURE OF IIPCI AND RCIC, 1.25 E-5/ YEAR FAILURE OF LPCI INJECTION, FAILURli 0F TORUS l COOLING, FAILURE OF CORE SPRAY, ELECfRIC POWER STATE 1, CAS SfKfE 1, RECOVERY 4

• SUBJECf TO COMPLEfl0N OF TVA MANAGEMENT AND PEEP REVIEWS MAY 18, 1988

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l BFN PRA - TVA/NRC MEETING -

DOMINANT SEQUENCES

(REVISED TABLE 2 0F OCf0BER 1,1987, NRC LEITER)

FREQUENCY *

6. PRESSURE REGULATOR fails CLOSED, FAILURE OF IIPCI 1.09 E-5/ YEAR 1 AND RCIC, FAILURE OF MANUAL ADS BLOWDOWN, ELECTRIC PWOER STATE 16, CAS STATE 1, NO RECOVERY

7. LOSS OF CONDENSER VACUUM, FAILURE OF llPCI AND RCIC, 9.91 E-6/ YEAR

AND FAILURE OF MANUAL ADS BLOWDOWN, ELECTRIC POWER

STATE 16, CAS STATE 1, NO RECOVERY 1

j 8. LOSS OF OFFSITE POWER RESULTING IN 1-3 STUCK OPI:N 9.37 E-6/ YEAR RELIEF VALVES, FAILURE OF EECW, ELECIRIC POWER STATE 3, CAS STKfE 1, RECO 2'

9. MAIN STEAM IS01ATION VALVE CLOSUlm, FAILURE OF 8.67 E-6/ YEAR 3

IIPCI AND RCIC, FAILURE OF Tile CONDENSATE SYSTEM, AND FAILURE OF MANUAL ADS BLOWDOWN, ELECTRIC i POWER STKfE 16, CAS STATE 1, NO RECOVERY

10. 'IRANSIENT WITil 1-3 S'IUCK OPEN RELIEF VALVES, 8.09 E-6/ YEAR FAILURE OF llPCI, FAILURE OF CORE SPRAY, AND a FAILURE OF RIIR, ELECTRIC POWER STATE 16, CAS '

} STKfE 3, RECOVERY i

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• SUBJECf TO COMPLEFION OF TVA MANAGEMINT AND PEER REVIEWS i

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BFN PRA - TVA/NRC MEETING

SUMMARY

OF POSSIBl_E PI_ ANT IMPROVEMENTS (TABLE 3 0F OCTOBER 1, 1987, NRC LETTER)

EDSSIBl_E PLANT IMPROVEMENT -

TVA RESPONSE i -

1. CilANGES TO MSIV ISOLATION CHANGES BEING INSTALLED AT SETPOINTS (L2 TO L1). PLANT. PRA DOES NOT TAKE CREDil.

CONSERVATIVE ESTIMATES OF AVAILABILITY OF POWER CONVERSION SYSTEM IN PRA.

2. CllANGES TO PROVIDE ONLINE TEST CilANGES NOT PLANNED AT PLANT.

CAPABILITY OF Tile SBLC SYSTEM. 'PRA DOES-NOT TAKE CREDIT.

IMPORTANCE OF ATWS AND SBLC GREATLY REDUCED FROM INITIAL WORK. REDUCTION OF SBLC UNAVAILABILITY NOT lilGil PRIORifY.

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BFN PRA - TVA/NRC MEETING

SUMMARY

OF POSSIBlE PLANT IMPROVEMENTS (TABLE 3 0F OCTOBER 1, 1987, NRC LETTER)

- TVA RESPONSE POSSIBIE PLANT IMPROVEMENT CilANGES TO BE INSTALLED

3. CilANGES TO FACILITATE AUTOMATIC AT PLANT. PRA DOES NOT TAKE ADS ACTUATION UPON LOW WATER QR 111 611 DRYWELL PRESSURE CREDIT.

PRA REFLECTS CURRENT DESIGN AND EMERGENCY OPERATING PROCEDURES.

CilANGES TO PROVIDE MINIMIZED AIR SYSTEM DESIGN BEING ft .

CONTROL AIR SYSTEM DEPENDENCE REVIEWED BY IVA. PRA MORE CLOSELY REFLECTS CURRENT PLANT CONFIGURATION.

IMPORTANCE OF AIR SYSTEM llAS BEEN GREATLY REDUCED DUE TO INCORPORATION OF SOME EXISTING PLANT FEATURES IN PRA MODEL.

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BFN PRA - TVA/NRC MEEFING

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, CONCLUSIONS

e BFN is NOT an outlier with respect to severe accidents.

j e TVA undertaking voluntary actions to implement changes to the 2

Pl ant to improve plant reliability.

Scram Reduction .

Maintenance Upgrade i

May 18, 1988 i

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1 May 27, 1988 Because the development of HRC guidance concerning the use of an Individual i Plant Examination (IPE) using the IDCOR methodology (i.e., licensee's letters dated June 9, 1987 and Febrausry 4, 1988) is still under way, the staff's review and assessment of the above information will be needed prior to restart. The staff and TVA discussed in details the level of informational requirements needed in the above responses. Based upon TVA's understanding of the staff's needs, TVA committed to provide this information no later than August 30, 1988. Upon completion of its scoping review of the licensee's l submittal, the staff will conduct an audit of the September 1987 revised draft PRA and supporting documentation. This review audit is scheduled to occur approximately one month after the receipt of the licensee's August 30, 1988 submittal. l Gerald E. Gears, Project Manager TVA Projects Division _

Office of Special Projects _.

Enclosures:

l

1. List of Attendees

2. TVA Slides Used in Presentation cc w/ enclosures:

See next page l

l Distribution i Docket File NRC PDR 1

Local PDR l

Those on Attached List OSP:TVA/A/LA p TV .

SBlac P

MSims :;.s 's:as 5/ /88 88 5/47 88

e Browns Ferry Nuclear Plant, l l

Units 1, 2 and 3 cc:

General Counsel Regional Administrator, Region 11 Tennessee Valley Authority U.S. Nuclear Regulatory Comission 101 Marietta Street, N.W.

400 West Suamit Hill Drive Atlanta, Georgia 30323 l E11 B33 l Knoxville, Tennessee 37902 Resident Inspector / Browns Ferry NP Mr. R. L. Gridley U.S. Nuclear Regulatory Comission Tennessee Valley Authority Route 12, Box 637 SN 157B Lookout Place Athens, Alabaira 35611 Chattanooga, Tennessee 37402-2801 Mr. Richard King Mr. H. P. Pomrehn c/o U.S. GAO  ;

Tennessee Valley Authority 1111 North Shore Drive l Browns Ferry Nuclear Plant Suite 225, Box 194 P.O. Box 2000 Knoxville, Tennessee 37919 Decatur, Alabama 35602 Dr. Henry Myers, Science Advisor -

Mr. M. J. May Comittee on Interior Tennessee Valley Authority and Insular Affairs Browns Ferry Nuclear Plant U.S. House of Representatives P.O. Box 2000 Washington, D.C. 20515 Decatur, Alabama 35602 Mr. D. L. Williams Mr. S. A. White Tennessee Valley Authority Manager of Nuclear Power 400 West Summit Hill Drive Tennessee Valley Authority W10 885 6N 38A Lookout Place

' Knoxville, Tennessee 37902 1101 Market Street Chairman, Limestone County Comission P.O. Box 188 Athens, Alabama 35611 Claude Earl Fox, M.D. ,

1 State Health Officer State Department of Public Health State Office Building Montgomery, Alabama 36130 1

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