ML20210V187

Summary of 860911 Meeting W/Util,Ge,State of Ny,Pirg,Nutech & Bechtel in Bethesda,Md Re Mark I Containment Safety Study. List of Attendees & Viewgraphs Encl

ML20210V187
Person / Time
Site:	Vermont Yankee
Issue date:	10/03/1986
From:	Rooney V Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8610100574
Download: ML20210V187 (38)

Text

October 3, 1986 e- .

Docket No. 50-271 LICENSEES: Vermont Yankee Nuclear Power Corporation FACILIlY: Vermont-Yankee Nuclear Power Station SUBJECI: SEPTEMBER'11, 1986 MEETING WITH THE VERMONI YANKEE NUCLEAR POWER CORP 0HAIION (VYNPC)

RE: Containment Safety Study On September'11, 1986,' a meeting was held at the NRC headquarters in Bethesda, Maryland to discuss the completed Vermont Yankee Mark I Containment Safety Study. Enclosure 1 is a list of individuals that attended the meeting.

Enclosure 2 is a handout of the slides presented by VPNPC at the meeting.

The study had been submitted on the Vermont Yankee docket by letter dated September 2, 1986, prior to the meeting. VYNPC described the contents of the study and answered various specific technical questions.

lhe staff acknowledged the receipt of the rcport and comented that plant specific information was provided which was expected to be useful in the generic BWR Containment Requirements effort. Furthermore, the staff noted that, considering the timing of the study, Vermont Yankee dovetails neatly as a sample case for generic containment requirements activities. Consistent with this purpose, the staff intends to review and comment on the study by late October to the extent of identifying significant areas of agreement and disagreement and providing questions. VYNPC comented that in order to provide timely response to questions, the continuation of this level of effort might conflict with certain other schedule commitments to NRR. The staff advised VYNPC to identity such cases to Project Management for discussion.

o Wi .!sd by Vernon L. Rooney, Project Manager BWR Project Directorate #2 Division of BWR Licensing

Enclosures:

DISTRIBUTION As stated R icYetvFile, 1 RBernero NRC PDR'~ " ~ DMuller cc w/ enclosures: Local PDR OGC - Bethesda See next page PD#2 Reading EJordan VRooney BGrimes ACRS (10) 0FFICIAL RECORD COPY DBL:PD#2 VRooney:cb h0100574861003 p DOCK 05000271 PDR

f D Kr. R. W. Capstick Vermont Yankee Nuclear Power Vermont Yankee Nuclear Power Corporation Station CC*

Mr. J. G. Weigand Mr. W. P. Murphy, Vice President &

President & Chief Executive Officer Manager of Operations Vermont Yankee Nuclear Power Corp. Vermont Yankee Nuclear Power Corp.

R. D. 5, Box 169 R. D. 5, Box 169 Ferry Road Ferry Road Brattleboro, Vermont 05301 Brattleboro, Vermont 05301 Mr. Donald Hunter, Vice President Mr. Gerald Tarrant, Commissioner Vermont Yankee Nuclear Power Corp. Vermont Department of Public Service 1071 Korcester Road 120 State Street Framingham, Massachusetts 01701 Montpelier, Vermont 0500E New England Coalition on Public Service Board Nuclear Pollution State of Vermont Hill and Dale Farm 120 State Street R. D. 2, Box 223 Montpelier, Vermont 05602 Putney, Vermont 05346 Vermont Yankee Decommissioning Mr. Walter Zaluzny Alliance Chairman, Board of Selectman Box 53 Post Office Box 116 Montpelier, Vermont 05602-0053 Vernon, Vermont 05345 Resident Inspector Mr. J. P. Pelletier, Plant Manager U. S. Nuclear Regulatory Commission Vermont Yankee Nuclear Power Corp. Post Office Box 176 Post Office Box 157 Vernon, Vermont 05354 Vernon, Vermont 05354 Vermont Public Interest Mr. Raymond N. McCandless Research Group, Inc.

Vermont Division of Occupational 43 State Street

& Radiological Health Montpelier, Vermont 05602 Administration Building .

10 Baldwin Street Regional Administrator, Region I Montpelier, Vermont 05602 U. S. Nuclear Regulatory Commission 631 Park Avenue

Honorable John J. Easton King of Prussia, Pennsylvania 19406 Attorney General State of Vermont i 109 State Street l Montpelier, Vermont 05602 John A. Ritscher, Esquire Ropes & Gray i 225 Franklin Street i Boston, Massachusetts 02110 l

i l

i O Enclosure 1 LIST OF MEETING ATTENDEES VERMONT YANKEE CONTAINMENT SAFETY STUDY September 11, 1986 Name Organization D. Muller NRR/ DBL /PD#2 V. Rooney NRR/ DBL /PD#2 E. Wenzinger, Sr. NRC Region I J. Hulman NRR/ DBL /PSB D. Vassallo NRR/ DBL / FOB R. Houston NRR/ DBL M. Thadani NRR/ DBL /PD#2 D. Shum NRR/ DBL /F0B G. Lainas NRR/ DBL F. Eltawila NRR/DSR0/ RIB W. Hodges NRR/ DBL /RSB F. Lodwick VYNPC J. Thayer Yankee Atomic Electric Co.

S. Schultz Yankee Atomic Electric Co.

W. Murphy VYNPC J. Goetz Wa:hington L. Marinos Reporting Service T. Landers New York Power Authority J. Gray, Jr. New York Power Authority L. Clifford GE S. Floyd Carolina Power & Light Co.

K. Holtzclau GE N. Edwards NUTECH T. Pickens Northern States Power M. Jmay TVA-BFN R. Bachmann NRC/0GC S. Markiewicz State of Massachusetts K. Campe NRR/ DBL /PSB J. Coats Vermont Public Interest Research Group E. Weiss Harman & Weiss Union of Concerned Scientists S. Murphy Nud. Information & Resource Service E. Fotoponlos Bechtel S. Bokim NRR/ DBL /PSB F. Coffman NRR/ SORI 4

A. Notafrancesco NRR/ DBL /PSB C. Reid Bechtel

0. Scott Southern Co. Services J. Kudrick NRR/ DBL /PSB i

i I

, __ , ~...,_,.__._s _ _ . _ _ . _ _ _ _ . _ . _ . _ . , . _ _ _ . . . . _. . . _ _ __

4 4' g e Enclosura 2 e

VERMONT YANKEE CONTAINMENT SAFETY STUDY O

\

VERMONT YANKEE CONTAINMENT SAFETY STUDY 1 INTRODUCTION PERSPECTIVE SCOPE RESULTS

SUMMARY

11 MARK I CONTAINMENT DESIGN REVIEW 111 SEVERE ACCIDENT ANALYSIS AND QUANTIFICATION BWR DOMINANT SEQUENCES CONTAINMENT CONDITIONAL FAILURE PROBABILITY o METHODOLOGY o ACCIDENT SEQUENCE QUANTIFICATION o INITIATING EVENT FREQUENCIES o CORE MELT FREQUENCIES o CONTAINMENT EVENT TREES o CONTAINMENT PERFORMANCE RESULTS IV MARK I CONTAINMENT POLICY ISSUES o HYDR 0 GEN CONTROL o DRYWELL SPRAY CAPABILITY o CONTAINMENT VENTING o CORE DEBRIS CONTROL o SEVERE ACCIDENT TRAINING PROCEDURE V DECISION ANALYSIS FOR RECOMMENDATIONS o RECOMMENDATIONS AND INSIGHTS

PERSPECTIVE e INITIATED - TO RESPOND TO QUOTED STATEMENT

-THAT MARK I CONTAINMENTS HAVE A 90%

CORTAINMENT CONDITIONAL FAILURE PROBABILITY e AGREED UPON BY VERMONT YANKEE, THE NRC AND THE GOVERN 0R OF THE STATE OF VERMONT ON JUNE 30,1986 e PROGRESS.

INITIATED JULY 1, 1986 i

INTERIM STATUS MEETING IN BETHESDA ON AUGUST 6, 1986

^

i FINAL REPORT COMPLETE AND TRANSMITTED TO NRC AND STATE OF VERMONT ON SEPTEMBER 2, 1986 t

4

- = - . - - -,r-. -

- . , , . . . . _ .- ~,.-r- -

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STUDY SCOPE e MARK I CONTAINMENT DESIGN REVIEW e QUANTIFY A VERMONT YANKEE SPECIFIC CONTAINMENT CONDITIONAL FAILURE PROBABILITY GIVEN A SCENARIO LEADING TO CORE MELT e ADDRESS MARK I CONTAINMENT POLICY ISSUES HYDR 0 GEN CONTROL DRYWELL SPRAY CAPABILITY CONTAINMENT VENTING

~~~

CORE DEBRIS CONTROL SEVERE ACCIDENT TRAINING AND PROCEDURES i

l 0 , . I STUDY RESULTS e VERMONT YANKEE CONDITIONAL CONTAINMENT FAILURE PROBABILITY OF 7%

e CONTAINMENT CAPABILITY IMPROVEMENTS IDENTIFIED PROCEDURE CHANGES / ENHANCEMENTS ISSUES FOR FURTHER EVALUATION INSIGHTS BASED ON SEVERE ACCIDENT SEQUENCES t

i G

i

. . . - _ . - _ . . ~ . . . . , , . - - _ _ _ . - . . . . . . _ . - _ . - . _ _ _ _ . - , . _ _ _ - _ - . . - . _ _ _ _ _ , - - ~ _ , . - - , _ - _ - _ . _ _ . _

o , ..

MARK I CONTAINMENT DESIGN REVIEW e SCOPE: COMPARE VERMONT YANKEE WITH THE MARK I REFERENCE PLANT T0 IDENTIFY DESIGN AND OPERATIONAL FEATURE DIFFERENCES SIGNIFICANT TO CONTAINMENT PERFORMANCE DURING SEVERE ACCIDENT SEQUENCES e

RESULTS: 4 SIGNIFICANT DESIGN FEATURES WERE IDENTIFIED RATIO 0F CONTAINMENT SIZE TO REACTOR POWER

- ELECTRICAL PLANT DIVERSITY DIESEL GENERATORS TIE LINE TO ADJACENT HYDROELECTRIC STATIONS

- CONNECTION FROM DIESEL FIRE PUMP TO LPCl/

CONTAINMENT SPRAY 8

l

CONTAINMENT FAILURE PROBABILITY EVALUATION e BACKGROUND

- WASH - 1400 (90%)

- DEFINITION OF CCFP e VERMONT YANKEE ANALYSES

- APPROACH

- ACCIDENT SEQUENCE IDENTIFICATION

- ACCIDENT SEQUENCE QUANTIFICATION

- CONTAINMENT EVENT TREE DEVELOPMENT

- CET QUANTIFICATION e

SUMMARY

OF RESULTS i

i Graphic Display of Containment' Performance

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i NORMAL OPERATIONS l

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w I: R:s e Ii DESGN BAS!S ACCIDENTS i:i:i. ~

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g i DURING 1HE UFE OF THE POTENTIAL CORE DAMAGE SCENARIOS D Ps. ANT 3 (SEVERE ACCIDENTS) ,

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.1 .2 .3 .4 .5 .6 .7 .8 .9 1.0

' CONTAINMENT fan.URE PROBASIUTY l

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I 1

DEFINITION OF "90%"

WASH-1400 ASSUMPTIONS e ALL SEQUENCES (MEll/NON-MELT) ARE ASSOCIATED WITH CONTAINMENT FAI e CORE MELT RELEASE CATEGORIES

1. STEAM EXPLOSION

2. OVERPRESSURE FAILURE DIRECT TO ATMOSPHERE

3. OVERPRESSURE FAILURE THROUGH REACTOR BUILDING

4. ISOLATION FAILURE e RELEASE CATEGORIES 2 & 3 DOMINATE RISK l

e SEQUENCES WHICH CONTRIBUTE COMPRISE 90%

ATWS LOSS OF RESIDUAL CORE HEAT REMOVAL CURREN1' STUDY e DIFFERENT DOMINANT SEQUENCES IDENTIFIED e KNOWLEDGE OF CONTAINMEN1 FAILURE PHENOMENA AND CRITERIA HAS EVULVED

1 CONTAINMENT CONDITIONAL FAILURE PROBABILITY e CALCULATE THE CONTRIBUTION OF EACH ACCIDENT CLASS TO TOTAL LIKELlH00D OF CORE MELT e DETERMINE THE CONDITIONAL FAILURE PROBABILITY OF CONTAINMENT FOR EACH ACCIDENT CLASS e CALCULATE THE WEIGHTED AVERAGE OF PRIMARY CONTAINMENT FAILURE PROBABILITY T

4 0

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- - - . . - -.=- - . , _ _ _ . - _ , , . - _ _ - - _ _ . - , _ _ . , - - - , - - - . - . - - - . - - . - _ . - _ - _ - . . - , _ _ , - _ - - - _ , . , , _ _. . - , , .. - _ . - .

COND1110NAL CONI AINMENT FAILURE PROPABill1Y 00AN11FICAll0N DOMINANT FRACTIONAL CONTAINMEliT CONTRIBUTION AcclDENT CONTRIBUTION FAILURE IO WElGHTED SE0VENCE _( CORE MELT) PRosasitiTy AvEnacE LOSS OF COOLANT MKEUP A A AxA LOSS OF i CONTAINtENT HEAT REM] VAL s B sxB 1

LOCA c C cxC ATWS o D oxD 1.0 E( ) = CFFP WHERE CCFP = CONDIT10NAL CONTAINMENT FAILURE PROBABillIY

. e CALCULATION PROCESS FLOW CHART i

/ .

i IDENhrY lDENTirY THE DEVELOP THE

! DOWINANT ACCIDENT SEQUENCE CONTAINWENT SEQUENCE TWES FREQUENQES EVENT TREE LEADING TO U  ? FOR THE OCAR PLANT SEWRE ACCIDENT CONTAINWENT CONDITIONS RESPONSE W UNTOUE FEATURES) 1 1

1 I CALCULATE THE COND110NAL QUANEFY FAILURE THE O PR08A51UTY

. CET OF CONTA!NWENT l

i l

l SYSTEM ^"

PHENOMENOLOGICAL STRENGTH AND utilCAMON CALCULAh0NS WLNERABluTY gyggy EVALUAMON

BWR DOMINANT ACCIDENT SEQUENCES CLASS I LOSS OF COOLANT MAKEUP IA HIGH PRESSURE IB STATION BLACK 0UT IC ATWS ID LOW PRESSURE lE LOSS OF DC CLASS 11 LOSS OF CONTAINMENT HEAT REMOVAL CLASS l'Il LOCA CLASS IV ATWS 1

DOMINANT ACCIDENT SEQUENCE QUANTIFICATION ALTERNATIVES e PLANT - SPECIFIC PRA e VY INDIVIDUAL PLANT EVALUATION e MODIFICATION OF REFERENCE BWR MARK I PRA TO ACCOUNT FOR KEY DIFFERENCES v

PEACHBOTTOM BWR IPE ANALYSIS UTILIZED AS THE REFERENCE POINT

/

INITIATING EVENT FREQUENCIES Number of Vermont Yankee Events in Best Estimate Category Types of Events Frequency Data Base (yr-1) 1 Transients Resulting in 20 Reactor Scram with Bypass 1.62 Potentially Available 2

Events Bounded by Loss of 2 Feedwater 0.16 3

MSIV Closure 4 0.32 4

Events with Bypass Not 8 Available 0.65 5

Inadvertent Opening of One 0 or More SRVs 0.062 6

Loss of Off-site Power 1 0.071 l

1 l

1 l

4 DERIVATION OF VERMONT YANKEE SEVERE ACCIDENT SEQUENCE FREQUENCIES

, VERMONT YANKEE SURROCATE PLANT VERMONT YANKEE DOMINANT DOMINANT SEQUENCES UNIQUE FEATURES ACCIDENT SEQUENCES AND FREQUENCIES DESIGNATOR FREQUENCY FEATURE DELTA DESIGNATOR FREQUENCY (per Rx yr) *

(per RK yr)

Class IB Class IB TgQUV PHASE I 1E-6 -Initiator (x.044/.05) K.35 TgQUV PHASE I 3.5E-7 2 D/G (x2)

-Hydro Plant (45 Phase I, 6.6 Phase II, 10 Phase III, IV)

-No. of Switchyards

-Underground transmission t

TEQUV PHASE II 2E-6

-No Event Specific K.52 TgQUV PHASE II 1.0E-6 Station Blackout Procedures (Approx. same Phase II) Phase III, IV (K3)

TEQUV PHASE III 4E-6

-Battery Life K1.1 TgQUV PHASE III 4.4E-6 (Approx. same)

Phase II, III, IV TEQUV PHASE IV I.6E-6 HPCI Potential Larger K.26 T EQUV PHASE IV 4.2E-7 DC Power Reqm't (K2)

Phase II, III TOTAL Class IB = 6.2E-6 i

i

. . l

SUMMARY

OF CORE MELT FREQUENCY TYPES AT VERMONT YANKEE Class Description Frequency Fraction

~

(yr )

IA Loss of Makeup; RPV 1.33E-5 .43 at high pressure IB Loss of Makeup: 6.2E-6 .20 Station Blackout IC Loss of Makeup: 2.6E-6 .08 ATWS ID Loss of Makeup: 3.9E-6 .12 RPV at low pressure IE Loss of Makeup: 2.4E-7 .01 Loss of DC buses II Loss of Containment 2.~1E-6 .07 Heat Removal III LOCAs 7.3E-7 .02 IV ATWS 2.2E-6 .07 i

V -Interfacing LOCA Netlitible Negligible  !

TOTAL 3.1E-5 100%

CONTAINMENT EVENT TREE DEVELOPMENT e CORE MELT ACCIDENT CLASS (ENTRY STATE) e CONTAINMENT MITIGATING SYSTEM RESPONSE e CONTAINMENT RESPONSE-FAILURE PATH & SIZE e REACTOR / AUXILIARY BUILDING RESPONSE

1 CONTAINMENT EVENT TREE END STATES TIMING T (BEYOND CORE MELT)

EARLY (E) T< 10 HOURS INTERMEDIATE (1) 10 < T< 24 HOURS LATE (L) T> 24 HOURS NO CONTAINMENT FAILURE (NCF) INTACT RELEASE QUANTITIES I (EQUIVALENT IODINE) PLils NOBLE GASES _

HIGH (H) I> 10%

MEDIUM (M) 0.1 < I < 10%

LOW (L) I< 0.1%

RNCTIONAL EVENTS: CONTAINTNT EVENT T E e CONTAltNENT ISOLATION AND INITIAL INTEGRITY

. eACTIVEMmGATIM: DRYWEU.T/PCONTROL e PASSIVE MITIGATION: CONTAlfEENTOFDEBRIS e CONTAlfNENT HEAT RBOVAL

-VIR

- VENTING e CONTAlfEENT BREACH SIZE f.AKAGE

- INERPRESSURE FAILURES e CONTAlfEENT BREACH 1.0 CATION YWEU.

LL AIRSPACE e REACTOR BUILDING EFFECTIVENESS

e CONTAINMENT EVENT TREES TOP EVENTS ACTIVE plTICATION CONTA!NWiNT N1[CRITY ACODCNT CON TAINgty1 WITICATION PASSVE CONTANWENTCONTAINW[N1 NO NO DRTMLL MTwEtt REACTOR CLASS ISOLATION ttWPotATUR[ WITICAfl0N NEAT PRESS *;RE IIANACE OVER- FNLURE A!R5 PACE BU:LDNC ENTRY & HlflAL CONTROL REMOVAL CONTROL PRESSURE STATE NTECRITY (WKCTFnd) (VENTINC) FAILURE cu et Y P W V D c W J R CLASSI + II l

ACQDENT CONhNUED ORWELL ActVE c0HTANWD81 NO NO OVDt- ORWELL M TWELL COOLANT EN MMCAMON PASSW PEACfDR CLASS E

ENTRY P[g LEAKACE PRES 5URE FAILURE AR5 PACE MAKEUP

{

MITICA110N BUILDNC sTA1E (WNTINC) FMLURE TO RPV WTECRITY

~

(NKCTION)

Cu v (o) (C) (H) (J) c a 1 P R r

IV l

1 I

CONTAINMENT EVENT TREE QUANTIFICATION BASES e PAST PRA EXPERIENCE e DETERMINISTIC EVALUATIONS (VY)

- MARCH /RMA

- MAAP

- HAND CALCULATIONS e IDCOR TECHNICAL REPORT INFORMATION e_ ENGINEERING JUDGMENT

s

SUMMARY

OF RELEASE FREQUENCY OF EACH RELEASE TYPE FOR EACH ACCIDENT CLASS: BASE CASE i "BEST ESTIMATE" CASE Accident Class Release Frequency (yr" ) of Release Type Designator Core Melt Frequency (yr _g) EH EN EL LM LL NCF IA 1.33E-05 7.38E-09 2.5BE-08 1.25E-07 6.89E-08 1.81E-07 1.29E-05 IB 6.20E-06 7.07E-09 1.11E-07 5.07E-07 3.56E-07 9.03E-07 4.31E-06 IC 2.60E-06 5.27E-07 2.83E-07 1.61E-08 9.31E-09 2.44E-08 1.74E-06 1

ID 3.90E-06 3.32E-09 4.60E-08 2.86E-08 5.44E-07 1.54E-06 1.74E-06 II 2.10E-06 4.73E-10 5.39E-07 1.56E-06 - - -

1 1

III 7.30E-07 .

5.53E-10 9.06E-10 6.56E-09 4.55E-08 1.28E-07 5.49E-07 IV 2.20E-06 5.44E-09 6.55E-07 1.54E-06 - - -

Sum 3.10E-05 5.51E-07 1.66E-06 3.78E-06 1.02E-06 2.78E-06 2.12E-05 i

% of Total Core Melt Frequency 100% '7.1% 12% 3.3% 9.0% 6EL

. CONTAINMENT CONDITIONAL FAILURE PROBABILITY (D BASE AND SENSITIVITY CASE RESULTS CATAGORIZATION EH/M . EL_ LM LL 3CE BASE 7 12 4 9 68 S1 10 12 3 9 66 S2 3 9 4 10 74 S3 1 3 6 16 74 WHERE:

S1 -

.EARLY CONTAINMENT FAILURE INCREASE FOR BOTH HIGH AND LOW PRESSURE MELT DOWNS S2 -

INCREASED OPERATOR ACTION CREDIT FOR ATWS EVENTS S3 -

S2 PLUS CLASSIFICATION OF TW CLASS AS LATE VERSUS EARLY RELEASE

w -u..

4-MARK 1 CONTAINMENT POLICY ISSUES e HYDROGEN CONTROL e

DRYWELL SPRAY CAPABILITY e CONTAINMENT VENTING e CORE DEBRIS CONTROL e

SEVERE ACCIDENT TRAlHING AND PROCEDURES 5

't

-.,.,,...------r- -

. , , , , , , - - - , , --- , ,-, - -- a

HYDR 0 GEN CONTROL e OBJECTIVE: PREVENT HYDR 0 GEN COMBUSTION FOLLOWING SEVERE ACCIDENTS e VY STATUS CONTAINMENT INERTED DE-INERT TIME CONTROLLED BY TECHNICAL SPECIFICATIONS OPERATING HISTORY INDICATES DE-INERT TIME IS 1.1% OF TIME PLANT IS IN RUN MODE VY RECENTLY CONVERTED TO N 2 CAD e EVALUATION: CURRENT VY PERFORMANCE AND DESIGN MEETS OBJECTIVE e RECOMMENDATIONS: NONE h

i

DRYWELL SPRAY CAPABILITY e

OBJECTIVE: PROVIDE AC INDEPENDENT CAPABILITY TO SPRAY DRYWELL TO LOWER PRESSURE AND TEMPERATURE e VY STATUS:

- NORMAL CAPABILITY FROM RHR, BACKED UP BY SERVICE WATER (DEPENDENT ON AC POWER)

DIESEL DRIVEN FIRE PUMP CAPABLE OF BEING ALIGNED TO LPC1/

CONTAINMENT SPRAY (AC INDEPENDENT)

- WATER SUPPLY FROM COOLING TOWER DEEP BASIN (AC DEPENDENT) e EVALUATION: CURRENT CAPABILITY ACCEPTABLE, ENHANCEMENTS POSSIBLE 10 INCREASE RELIABILITY OF SUPPLY FROM DIESEL FIRE PUMP e REC 0MMENDATIONS:

- ENHANCE THE OPERATION OF THE DIESEL FIRE PUMP TO DRYWELL SPRAY FLOW PATH

- IMPROVE ABILITY TO RESTORE AC POWER

CONTAINMENT VENTING e OBJECTIVE: PREVENT UNCONTROLLED LOSS OF CONTAINMENT INTEGRITY e VY STATUS:

ONLY VERY SMALL VENTING PATHWAY PROCEDURALIZED STUDY IDENTIFIES 6 VENTING PATHWAYS

- RISKS OF VENTING DISCUSSED e EVALVATION: CAPABILITY FOR WETWELL VENTING, 10 ACHIEVE FISSION PRODUCT SCRUBBING, SHOULD BE ENHANCED e RECOMMENDATIONS:

ENGINEERING EVALUATION OF UPGRADING WETWELL VENTING TO BE INITIATED

, VENTING GUIDELINE DOCUMENT PREPARED OUTLINING 32 POTENTIAL VENT PATHS, REQUIREMENTS FOR USE, ACCESS, ETC.

o s 8-CORE DEBRIS CONTROL e OBJECTIVE:

PRECLUDE CONTAINMENT FAILURL DUE TO SHELL CONTACT e VY STATUS:

SMALL CORE VOLUME IN LARGE DRYWELL PRO WILL NOT MIGRATE TO DRYWELL SHELL

- DRYWELL SPRAYS WILL " REFREEZE" CORIUM e EVALUATION:

CURRENT VY CONFIGURATION MEETS OBJECTIVE e

RECOMMENDATIONS: NONE

~

. i SEVEERE ACC' DENT TRAINING AND PROCEDURES e OBJECTIVE:

ENSURE OPERATORS READY TO USE PLANT FE BEST ADVANTAGE IN SEVERE ACCIDENTS e VY STATUS:

- VY HAS IMPLEMENTED E0P's BASED ON REV. 3 0F THE e

EVALUATION: VY MEETS CURRENT GUIDANCE e RECOMMENDATION:

IMPLEMENT REV. 4 0F EPG's WHEN AVAILABLE

- CONSIDER REVISION TO EXISTING E0P's FOR:

o STATION BLACK 0UT o CONTAINMENT VENTING o DRYWELL SPRAY USING DIESEL FIRE PUMP o GUIDANCE TO SUPPLY CST VIA FIRE SYSTEM o SAMPLE SUPPRESSION POOL BEFORE TRANSFER TO CST o PROCEDURALIZE 22H /0 CONTROL o COMPLETE DEVELOPMENT OF VY SPECIFIC LEVEL /

DECISION ANALYSIS FOR RECOMMENDATIONS e TWO PART TEST

- WHICH SEVERE ACCIDENTS WARRANT CONSIDERATION?

- WHAT IS ACCEPTABLE CONTAINMENT PERFORMANCE?

e SEVERE ACCIDENT SEQUENCES

- MOST CRITICAL TO CONTAINMENT PERFORMANCE ARE:

STATION BLACK 0UT ATWS WITH MSIV CLOSURE e ACCEPTABLE CONTAINMENT PERFORMANCE

- CONTAINMENT SHOULD REMAIN INTACT, WITHOUT EXCESSIVE LEAKAGE FOR 24 HOURS FOLLOWING EVENT INITIATION e RECOMMENDATIONS REPRESENT THE CONCENSUS OF THE STUDY TEAM REGARDING PROCEDURAL AND DESIGN ENHANCEMENTS T0 IMPROVE CONTAINKENT PERFORMANCE.

- MAXIMlZE USE OF EXISTING PLANT FEATURES

- AUGMENT EXISTING DESIGN WHERE CLEAR BENEFIT IS APPARENT

RECOMMENDATIONS e PROCEDURE ADDITIONS / ENHANCEMENTS e- ISSUES FOR FURTHER EVALUATION e INSIGHTS BASED ON SEVERE ACCIDENT SEQUENCES J

O

PROCEDURE ADDITIONS / ENHANCEMENTS e

PROVIDE PROCEDURAL GUIDANCE FOR RESTORATION OF AC POWER FOL A STATION BLACK 0UT e

PROVIDE A REPAIR PROCEDURE OUTLINING THE RESTORATION OF TH TIE LINE IF DAMAGE SHOULD OCCUR e

PROVIDE PROCEDURAL GUIDANCE FOR OPTIMlZATION OF DC POWER SOUR FOLLOWING A STATION BLACK 0UT f

e PROVIDE PROCEDURAL GUIDANCE FOR USE OF THE SRV's FOR MANUAL DEPRESSURIZATION FOLLOWING A STATION BLACK 0UT e

PRGVIDE PROCEDURAL GUIDANCE 10 ALIGN THE DIESEL FIRE PUMP FOLLOWING STATION BLACK 0UT e PROVIDE LEVEL / POWER GUIDANCE FOR ATWS

- - - , - , - _ _ , - - _ . - - - - - _ _ _ . - - . - - -- s--- . +

ISSUES FOR FURTHER EVALUATION e UPGRADE E0P's TO REV. I4 0F EPG's e UPGRADE SELECTED VALVE OPERATORS IN FLOW PATH FROM DIESEL FIRE PUMP TO LPC1/ CONTAINMENT SPRAY e ENHANCE RELIABILITY AND CAPABILITY OF CONTAINMENT WETWELL VENT O

4

'I

.1 INSIGHTS BASED ON SEVERE ACCIDENT SE0VENCES e

PROVIDE ADDITIONAL EVALUATION, GUIDANCE AND OPERATOR TRAINING ON RESPONSE OF THE RHR PUMPS TO HIGH SUPPRESSION P TEMPERATURES e

IMPROVE RELIABILITY OF THE NITROGEN SUPPLY TO THE A e

EVALUATE DESIGN AND POST-ACCIDENT RELIABILITY OF TH WATER SYSTEM e

EVALUATE STANDBY LIQUID CONTROL SYSTEM DESIGN AN

.