ML20246G279
| ML20246G279 | |
| Person / Time | |
|---|---|
| Issue date: | 12/12/1988 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-2610, NUDOCS 8905150248 | |
| Download: ML20246G279 (30) | |
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12/12/88 ma ACRS Subcommittee Meeting Summary / Minutes For Containment Systems December 6, 1988 Bethesda, Maryland Purpose The ACRS Subcommittee on Containment Systems met on December 6, 1988 in Bethesda,. Maryland. The purpose of this meeting was to discuss the NRC Steff's proposed final recommendations for containment performance and improvements for BWR Mark Is. Copies of the agenda and selected slides from the presentation are attached. The meeting began at 8:30 a.m. and adjourned at 3:30 p.m. and was held entirely in open session. The principal attendees were as follows:
Attendees ACRS NRC/RES D. Ward, Chairman T. Speis W. Kerr, Member W. Beckner P. Shewmon, Member L. Shoffer C. Siess, Member J. Ridgely I. Catton, Consultant J. Dallman, Contractor M. Corradini, Consultant D. Houston, Staff NRC/NRR G. Thomas R. Jones C. Tinkler I
Discussion l
The principal documents for discussion at this meeting were:
(1)a proposed SECY paper entitled, " Mark I Containment Performance Improve-ment Program," provided by the Staff on November 18,1988,(2) the seven enclosures with the SECY, especially the proposed generic letter,
" Propose Severe Accident Requirements For Plants With Mark I
[50/
DESIGNATED ORIGINAL I
j 8905150248 881212 0
i
'Containemnt Systems Minutes December 6, 1988 Containments," and (3) the General Electric Topical Report NED0-31331,
" Emergency Procedure Guidelines, Revision 4," March 1987, as prepared by the BWR Owners Group (BWROG).
T. Speis (RES) discussed the historical background for the Mark I containment improvements program and indicated where this issue fit into the RES severe accident integration plan. He further discussed some insights gained from PRAs on BWRs. He emphasized that:
(1)theoverall risk is low, (2) Mark I plants are not risk outliers as a class (3) i some postulated containment failure modes are highly uncertain, espe-cially liner melt-through.
He indicated that the core melt frequencies (CMF) for BWRs was (IE-4 and that the conditional containment failure (CCF) for Mark Is was significantly lower than 50%. He stated that the basis for the ir.provements was to decrease the risks even though risks were low and all plants met the safety goal.
G. Thomas (NRR) discussed containment venting, mostly venting procedures as they appear in the emergency procedure guidelines (EPGs), Revision 4.
Venting guidelines were first approved by the Staff in 1983 with Re-vision 2, EPGs. Venting procedures based on the primary containment pressure limit (PCPL) and hydrogen control were discussed.
T. Spets (RES) sunsrarized the risk implications of venting as given in 1
NUREG/CR-5225. He discussed some accident sequences (TW, SBO) in which l
containment venting reduced the probability of core damage.
He also indicated that external filters would not significantly reduce risk.
In regard to liner melt-through, T. Speis indicated that a variety of views exist on the subject. He discussed the benefits of adding water to the drywell and indicated that RES will pursue research to confirm 4
I that liner melt-through is unlikely in the presence of water.
.., -...s.
en Containemnt Systems Minutes December 6, 1988 L. Shoffer (RES) discussed their balanced approach to reduce overall risk and summarized the Staff recommendations for the Mark Is. These improvements were as follows:
(1) accelerate implementation of station blackout rule, (2) require alternate water supply and electrical power for drywell spray / vessel injection, (3) require hardened venting capability from wetwell, (4) require enhanced ADS reliability, and (5) require implementation of EPGs, Revision 4.
He indicated that the Staff was still reviewing the need/ suitability of
.a rupture disk in the hardened vent system.
He reviewed the efforts by-industry - the EpG work by BWROG and the planned modifications at two Mark Is, Vermont-Yankee and pilgrim.
J. Ridgely (RES) discussed the backfit considerations for the required improvements and presented some cost-benefit values for them. His estimated costs were questionably low but as such, supported the imple-j mentation of the proposed improvements.
During the presentations, Subcommittee Members and Consultants discussed various aspects of the proposed improvements and the containment venting concepts / procedures. The following comments and concerns were expressed during the discussion (random order):
(1) With liner melt-through highly uncertain and BWR Mark I risks reportedly low, what is the motivation for pursuing generic improvements? Also, why are Mark Is being singled out on a i
l L2--_----_--
.. u Containemnt Systems Minutes December 6, 1988 l
higher priority? The RES response addressed only a lowering l
of risk, one that was similar to other containment / plant types
)
and one that met the safety goal.
(2) The implementation of the Mark I improvements is ta be com-pleted 30 months from the time of the issuance of the generic l
letter (January-February 1989). The IPE letter was issued in November 1988 and requests that the studies be completed in 36 months. A concern was expressed that the Mark I matter could 1
be better handled within the scope of the IPE program. The Staff commented that perhaps better fixes would come from the IPE effort.
(3) The legality of containment venting procedures was questioned and the Staff was asked if an environmental impact statement (EIS) was required. The Staff indicated that an EIS would be prepared for rulemaking on the Mark I issues. The Staff was also asked if training for venting would be given to senior utility managers as well as operating personnel.
(4) The Staff was asked to give high priority to those research programs directed toward answering the questions on liner melt-through.
(5) The Staff was also asked to concentrate their efforts on items of lower uncertainty (ADS, water injection) rather than higher uncertainty items like liner melt-through.
(6) The details of the cost-benefit study were a matter of concern especially the obvious low estimated costs versus those actually incurred at Pilgrim as well as other assumptions made by the Staff.
RES indicated that only the installation of a hardened vent system could be justified by value impact analysis.
~
Containemnt Systems Minutes December 6, 1988 (7) A concern was expressed as to the goal of the proposed im-
.provements. As written, the generic letter.would require all Mark Is to implement these items even those with extremely low core melt frequencies. The Staff was requested to quantify what value of ris.k is acceptable.
At the conclusion of the meeting, plans for a Staff presentation to the Full Committee in December 1988 were discussed. The Staff was requested to present:
(1).a condensed overall description of the improvements for-Mark Is, and (2) a brief overall description of EPGs, Revision 4 NOTE:
Additional meet *ng details can be obtained from a transcript of this meeting available in the NRC Public Document Room, 2120 L Street, N.W., Washington, D.C. 20006,(202).634-3273, or can be purchased from Heritage Reporting Corporation, 1220 L Street, N.W.,-Suite 600, Washington, D.C. 20005,(202) 628-4888.
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.2' i
i ACRS Subcommittee Meeting on Containment Systems December 6, 1988 l
Bethesda, Maryland
_ Proposed' Agenda -
1.
. Subcommittee Chairman D. Ward 8:30 am Opening Remarks.
2.
. Introduction / Background T.Speis(RES) 8:45 am-Background (1986 Initiative, Workshop, etc.)
- ' Severe Accident Integration Plan (SECY-88-147)
- Relation of Mark I Containment Perfoniance Improvement to Integra-tien Plan Role of IPE's 3.
FRA Insights RES 9:30 am
- Insights from PRA's
' Mark I Challenges and Failure Podes
- BREAK ***
10:00 - 10:15 am 10:15 am 4.
Containment Venting and EPG's (Venting, Hydrogen Control, Decision to Vent)
- Yenting Risk Implica-RES tions (Positive /
NegativeAttributes) 5.
Status on Liner Melt--
RES 11:15 am Through-
- LUNCH ***
12:00 - 1:00 pm
__________m__.__
- L.
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Containment Systems Proposed Agenda December 6, 1988 1
1
' 00 pm.
6.
Staff Approach to Reduce RES 1:
Overall Risk
' Br. lanced Approach i
"' Discussion of. Individual P. recommendations
- Alternate water supply
- Enhanced ADS reliability
- Inproved venting
- Procedures and training
~(EPG's. Pev. 4) 7.
Backfit Considerations RES 2:00 pm Benefits, Costs, Cost-Benefit Results, Safety Goal'
'8.
Conclusions and Recommenda-T. Speis 2:45 pm tions t
- Conclusions Proposed Implementation 9.
Subcommittee Discussion and D. Ward 3:15 pm Plans
- 10. Adjourn 3:45 pm d
_L__-_.__----__.--_______---_-__._
i BRIEFING ON BWR MARK 1 CONTAINMENT IMPROVEMENT PROGRAM BEFORE ACRS SUBCOMMITTEE ON CONTAINMENT SYSTEMS DECEMBER 6, 1988
'THEMIS P. SPEIS WILLIAM.D. BECKNER LEONARD SOFFER JOHN N. RIDGELY OFFICE OF NUCLEAR REGULATORY RESEARCH U.S. NUCLEAR REGULATORY COMMISSION 1
- O
^i BACKGROUND o
JUNE 1986, STAFF PROPOSED 5 ELEMENT PROGRAM FOR MARK 1 CONTAINMENT PERFORMANCE ENHANCEMENT o
JUNE-JULY 1987, TWO LICENSEES INFORMED THE STAFF 0F THEIR INTENTION TO INVESTIGATE CONTAINMENT AND SAFETY ENHANCEMENT o
JULY 1987, STAFF BRIEFED COMMISSION ON A' PLAN FOR q
CLOSURE OF SEVERE ACCIDENT ISSUES l
DECEMBER 1987, " MARK 1 CONTAINMENT PERFORMANCE PROGRAM 0
PLAN",(SECY-87-297) o FEBRUARY 1988, WORKSHOP ON MARK 1 ISSUES MAY 1988, " INTEGRATION PLAN FOR CLOSURE OF SEVERE o
ACCIDENT ISSUES", (SECY-88-147)
JULY 1988, " STATUS OF MARK 1 CONTAINMENT PERFORMANCE o
EVALUATION", (SECY-88-206) 1 1
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DOMINAi,T ACCIDBU INITIATORS (ItMAL) AE:
STATION BLACKOUT (SBO)
AES LOSS OF DECAY HEAT REMOVAL (TW)+
WIDE VARIATION IN ACCIDBU LIKEllHODD OVERALL RISK LOW FURTHER REDUCTIONS IN SEVERE ACCIDBU RISK VIA ACCIDB6 PFN0510N, VANAGBM, MITIGAT10t1 (BALAt1CED APPROACH) POSSIBLE It'PLBEATION OF ADEQUATE VBUlllG PROCEDURES CAN REDUC ELT FREQUBICY FOR TW SE0tJENCES BY Att ORDER OF FAGt11
+1N THE ABSENCE OF WEIKELL VENTING
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____..____.___._.-_-_______.____.______.-______.____.-_____________m_
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- BWR MARK 1-CONTAltlMENT CHALLENGES if
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. CONTAINMENT COULD BE CHALLENGED.BY LARGE SCALE CORE MELT, PRINCIPALLY DUE TO SMALLER SIZE o
SEVERAL EARLY' CONTAINMENT FAILURE MODES IDENTIFIED BUT, MUST EMPHASIZE THAT o
BWR MARK 1 PLANTS ARE E I RISK OUTLIERS'AS A CLASS, AND o
SOME' POSTULATED CONTAINMENT FAlLURE MODES ARE HIGHLY UNCERTAIN, ESPECIALLY LINER MELT-THROUGH 1
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0VERVIEW 0F BWR MARK I CONTAINMENT VENTING RISK IMPLICATIONS (NUREG/CR-5225) o VENTING FOR TW SEQUENCE REDUCES THE PROBABILITY OF CORE DAMAGE ACCIDENTS o
VENTING PROVIDES A SCRUBBED RELEASE FOR-ALL SEQUENCES WHERE THE CONTAINMENT REMAINS INTACT o
HARD PIPE VENT-PREVENTS POTENTIAL REACTOR BUILDING CONTAMINATION DUE TO DUCT FAILURE AND PERMITS BUILDING RE-ENTRY AND REPAIR ACTIVITIES o
PRE-EMPTIVE VENTING REDUCES RISK FOR LONG-TERM SB0, INCREASES RISK FOR SHORT-TERM SB0 o
VENTING BENEFITS LIMITED BY EARLY CONTAINMENT FAILURES (E.G., VIA LINER MELT-THROUGH AND/0R OVERPRESSURE FAILURES) o ADDITIONAL EXTERNAL FILTERS (LIKE THE FILTRA DESIGN)
WOULD NOT SIGNIFICANTLY REDUCE RISK VENTING WITH ENHANCED ADS RELIABILITY AND ALTERNATE WATER o
INJECTION REDUCES CORE MF.LT LIKEllH00D FOR SB0 EVENTS.
10 j
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SUMMARY
OF FEB. 24-26, 1988 BWR MARK I WORKSHOP _
THREE-DAY MEETING WITH 150 INDUSTRY, RESEARCHER, STAFF AND PUBLIC REPRESENTATIVES INDUSTRY EMPHASIS ON PREVENTION.
ANY FIXES SHOULD BE PLANT SPECIFIC FROM IPE.
VARIETY OF VIEWS ON PR0BABILITY OF LINER MELT-THROUGH MANNER OF VESSEL FAILURE AND RELEASE OF DEBRIS IMPORTANT INDUSTRY BELIEVES WATER CAN PREVENT LINER MELT-THROUGH WATER BENEFICIAL, BUT NO CONSENSUS FROM NRC RESEARCHERS ON WHETHER LINER FAILS AND WHEN GENERAL AGREEMENT--WATER IN DRYWELL USEFUL TO DELAY /
PREVENT SHELL FAILURE AND TO REDUCE FISSION PRODUCT RELEASES AGREEMENT THAT ADS RELIABILITY IMPORTANT.IMPROVEMENTS ACHIEVABLE AT MODEST COST.
POTENTIAL POSITIVE AND NEGATIVE SAFETY IMPACTS OF VENTING REDUCE CORE-MELT LIKEllH00D, REDUCE CONSEQUENCES, BUY TIME POTENTIAL FOR UNNECESSARY RELEASE, INCREASE CORE-MELT LIKEllH00D FOR SOME SEQUENCES MORE FOCUSED RESEARCH NEEDED ON VESSEL FAILURE AND DEBRIS RELEASE VESSEL FAILURE CHARACTERISTICS AND LIKEllH00D j
0F LINER MELT-THROUGH WITH WATER
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RECENT STUDIES L
o NRC SPONSORED STUDIES
- HUREG-1150 EXPERT ELICITATION AND SUPPORTING ANALYSES
- ORNL BWRSAR/CONTAIN CALCULATIONS BNL SMALL SCALE MELT SPREADING EXPERIMENTS
'* IMPACT OF WATER DEPTH
- IMPACT OF MELT. MASS SUPERHEAT
- EXPERittENTS RELATED TO MELT / LINEAR HEAT TRANSFER
- SNL WITCH-LINER TESTS TO STUDY HEAT TRANSFER FROM BUBBLE-AGITATED LIQUID TO VERTICAL WALL.
i
- UCSB WATER-AIR TESTS TO STUDY THE IMPACT OF INCLINED LINER o
INDUSTRY SPONSORED STUDIES
- GE ANALYTICAL STUDIES
- FAl/EPRI EXPERIMENTAL STilDIES CONCLUDING STRONG ENERGY REMOVAL RATE BY WATER FAR EXCEEDING THE CRITICAL HEAT FLUX VALUE.
f o
OTHERS
- MIT ANALYTICAL STUDIES CONCLUDING LOW LIKEllH00D 0F LINER ATTACK ESPECIALLY FOR LOW MEDIUM SUPERHEAT, OX1DIC MELTS UNDER WATER.
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CORE DEBRIS CONTROLS o
TELHNICAL FEASIBILITY OF CURBS IN DRYWELL AND/0R CURBS OR WEIR WALLS IN TORUS ROOM NOT YET ESTABLISHED.
o INSTALLATION COSTS, OCCUPATIONAL EXPOSURE BELIEVED SIGNIFICANT o
GROWING BELIEF THAT WATER IN DRYWELL MAY HELP TO
~
PREVENT OR AT LEAST DELAY LINER MELT-THROUGH o
WATER IS EFFECTIVE IN REMOVING (SCRUBBING) FISSION PRODUCT AEROSOLS l
STAFF WILL PURSUE RESEARCH TO CONFIRM THAT LINER 0
MELT-THROUGH IS UNLIKELY IN THE PRESENCE OF WATER EXCEPT FOR MASSIVE POUR RATES OF LARGE METALLIC CONTENT AT HIGH SUPERHEAT 13
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SUhflARY OF STAFF 1
RECOMMEt1DAT10NS i
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o ACCELERATE IMPLEMENTATION OF STATION BLACK 00T' RULE o.
REQUIRE ALTERNATE WATER SUPPLY FOR DRYWELL SPRAY / VESSEL INJECTION WITH PUMPlNG CAPABILITY INDEPENDENT OF NORMAL AND EMERGENCY'AC o
REQUIRE HARDEllED VENTING CAPABILITY FROM WETWELL (ABLE TO WITHSTAND SEVERE ACCIDENT PRESSURES).
ISOLAT1011 VALVES TO BE REMOTELY OPERABLE INDEPENDENT OF 140RMAL AND EMERGENCY AC.
o REQUIRE EllHANCED ADS RELIABILITY.
ADDITIONAL POWER AND/0R NITROGEN SUPPLY AtiD CABLE RELIABILITY o
REQUIRE IMPLEMENTATION OF IMPROVED EPG'S (REV. 4 0F BWROG) l 15
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ALTERNATE WATER SUPPLY ALTERNATE SUPPLY OF WATER PLUS PUMPING CAPABILITY.
INDEPENDENT OF NORMAL AND EMERGENCY AC POWER-WATER DEllVERY AVAILABLE EITHER INTO REACTOR VESSEL (VIA RHR SYSTEM) OR TO DRYWELL SPRAYS ALTERNATE SOURCE OF WATER INJECTION INTO REACTOR VESSEL REDUCES LIKEllH00D OF CORE NELT AND PROVIDES ADDITIONAL IN-VESSEL ACCIDENT MANAGEMENT CAPABILITY WATER FOR DRYWELL SPRAY PROVIDES SIGNIFICANT MITIGATION CAPABILITY TO COOL CORE DEBRIS, COOL CONTAINMENT LINER, AND SCRUB AIRBORNE FISSION PRODUCTS 16 4-_-_________-
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IMPROVED VENTING CAPABILITY l
VENTING CURRENTLY INCLUDED IN BWR EMERGENCY OPERATING PROCEDURES HARD PIPE VENT WOULD REPLACE PRESENT SHEETMETAL DUCT.
CAN WITHSTAND SEVERE ACCIDENT PRESSURES l
VENT ISOLATION VALVES TO BE REMOTELY OPERABLE FROM CONTROL ROOM VENTING CAN REDUCE LIKEllH00D OF CORE MELT FROM LOSS OF LONG-TERM DECAY HEAT REMOVAL 1
VENTING VIA SUPPRESSION POOL WILL SCRUB NON NOBLE GAS
.I FISSION PRODUCTS PRIOR TO RELEASE l
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i ENHANCED ADS RELIABILITY o
TO INCREASE RELIABILITY, ADDITIONAL DC POWER SOURCE NEEDED.
MAY NEED ADDITIONAL NITROGEN SUPPLY NEED TO REVIEW CABLE PERFORMANCE o
BENEFITS
^
-WITH' LOW PRESSURE SOURCE OF WATER, HAVE' ADDITIONAL SOURCE OF CORE COOLING FOR HIGH PRESSURE SEQUENCES (E.G., STATION BLACK 0UT)
-REDUCED REACTOR PRESSURE REDUCES LIKEllH00D OF HIGH PRESSURE MELT EJECTION IN EVENT OF PRESSURE VESSEL FAILURE l
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1 EMERGENCY PROCEDURES AND TRAINING REPRESF1TS MAJOR ELEMENT IN MARK 1 CONTAINMENT PERFORMANCE o
IMPROVEMENT PROGRAM STAFF RECENTLY APPROVED REV. 4 0F SWROG EPG's.
SIGNIFICANT o
IMPROVEMENT OVER EARLIER VERSIONS.
NEW EPG's EXTEND WELL DEYOND DESIGN BASIS EVENTS, INCLUDE MANY ACTIONS APPROPRIATE FOR SEVERE ACCIDENT MANAGEMENT IMPROVEMENT IN EPG's HAS TO BE REFLECTED IN PLANT-SPECIFIC E o
AND IN OPERATOR ' TRAINING.
IMPLEMENTATION PRESENTLY VOLUNTARY.
PROPOSE TO MAKE MANDATORY.
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INDUSTRY EFFORTS i
l-o f1RC STAFF RECENTLY APPROVED REVISION 14 TO THE EPG's, q
PROPOSED BY BWROG.
THESE INCLUDE VENTING 0F CONTAINMENT l
0 VERM0llT YANKEE PLANtilNG CHANGES DURING 1989 REFUELING OUTAGE, INCLUDING:
- USE OF DIESEL FIRE PUMP FOR DECAY HEAT REMOVAL
- DIESEL DRIVEN AIR COMPRESSOR TO SRV's
- MODIFICATION OF E0P's
- UPGRADE OF SIMULATOR PILGRIM HAS DEVELOPED A SAFETY ENHANCEMENT PROGRAM WHICH o
INCLUDES:
- HARD PIPE VENT FROM TORUS TO STACK (PRESENTLY NOT CONNECTED)
- THIRD ONSITE DIESEL GENERATOR
- BACKUP NITROGEN SUPPLY FOR ADS AND MAINTAINING CONTAINMENT INSERTED
- USE OF FIRE PROTECTION DIESEL PUMPS FOR DECAY HEAT REMOVAL L
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I BEllEFIT OF IMPROVEMENTS
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MAJOR BENEFIT IS REDUCTION IN CORE MELT FREQUENCY OF-ABOUT.
ONE ORDER OF NAGNITUDE l
0 LARGE PORTION 0F CORE MELT REDUCTION DUE T0 IMPROVED VENTING
. o-ACCIDENT MITIGATION ALSO SIGNIFICANT VEllTING PREVENTS CONTAINMENT FAILURE RESULTING FROM SLOW OVER-PRESSURE.
- VENTING VIA SUPPRESSION POOL PROVIDES FISSION PRODUCT SCRUBBING
- WATER IN DRYWELL MAY COOL DEBRIS, DELAY LINER FAILURE, SCRUB FISSION PRODUCT RELEASES I
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ESTlMATED COSTS AND BENEFITS ESTIMATED COSTS * (PER PLANT) l c
RANGE - 1,6 TO 3.1 MILLION DOLLARS BEST ESTIMATE - 2.0 MILLION DOLLARS ESTIMATED BENEFITS ** (PER PLANT)
RANGE - 2.9 TO 23 MILLION DOLLARS SIMILAR IMPROVEMENTS AT ONE MARK 1 PLANT MAY HAVE COST ABOUT 7.3 NILLION DOLLARS.
BASED UPON 1000 DOLLARS PER PERSON-REM AND A REMAINING PLANT LIFE 0F 20 YEARS 23
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I CONCLUSIONS PROPOSED Ef1HANCEMENTS PROVIDE SUBSTANTIAL INCREASE 11)
PROTECT 10N OF PUBLIC HEALTH AND SAFETY 1
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PROPOSED ENHANCEMEf4TS ARE GEllERALLY COST BENEFICIAL' I
BACKFIT OF PROPOSED ENHAf1 CEMENTS IS WARRANTED FOR ALL MARK 1-PLAf4TS l
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l STAFF RECOMMENDATIONS o.
ACCELERATE IMPLEMENTATION OF STATION BLACK 0UT RE0VIREMENTS (ATWS IMPLEMENTATION TO BE' ESSENTIALLY COMPLETE BY 1/89)
IMPLEMENT IMPROVED EMERGENCY OPERATING PROCEDURES o
'AND TRAINING.
ISSUE GENERIC LETTER TO ALL BWR MARK 1 LICENSEES o
PREPARE RULE REQUIRING CONTAINMENT IMPROVEMENTS o
FOR ALL MARK 1 PLANTS CONTINUE CONFIRMATORY RESEARCH ON MARK 1 VESSEL o
FAILURE PROGRESSION, THE POTENTIAL FOR LINER MELT THROUGH, AND ASSOCIATED SOURCE TERMS.
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BW EERGENCY PROCFDUPE GillDEl.lMFS (FKM GMAlttDT \\UITING PRESENTATION TO ACRS SURCfttiiTTEE MEETING DECB 9ER 6, 1988 GEORGETHnPAS REACT 0P SYSTEMS BRAPrF D!t'ISION OF EMG!EERIFr a SYST95 TFCHNOLOGY OFFICF. OF MJCLEAR REACTOP PFGIILATim i
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PRIMARY CONTAINMENT PRESSURE LIMIT (PCPL)
. REVISION 3 - PCPL WAS TWICE THE CONTAINMENT DESIGN PRESSURE e
IF REVISION.5 VENT AFTER CONTAINMENT PRESSllRE EXCEEDS PCPL e-i REVISION 4 PROVIDES PETTER GUIDANCE FOR DETERMINING PCPL e
e PCPL IS DEFINED TO BE THE LOWEST OF I
(1)
PRESSURE CAPABILITY OF THE CONTAINMENT OP (2)
VENT VALVES OPERABILITY OR (3)
SRVs OPERABILITY OR (11)
PPV VENT VALVE OPERABILITY
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e' VENT BEFORE CONTAINMENT PRESSilRE REACHES PCPL L
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f,,.y - ^ STAFF POSITION 0N VENTING e-STAFF FINDS VENTING TO PROVIDE A SAFETY ENHANCEMENT e LAST RES0RT, BUT STAFF RECOGNIZES THAT TliE PROCEDURES ALLOW VENTIt'C BEFORE CONTAINMENT PRESSURE REACPES PCPL a STAFF F*iASIZE IMPORTANCE OF TRAINit!G TO PREVENT PREMATURE VENTING s LICENSEES ARE Et'COURAGED TO VENT AT A PRESSURE AS HIGH AS . PRACTICAL - WE PECOMMEND VENTING AT PESIGN PRE!:SURE AS A MINIMUM l e PllRSUE ACTIOPS TO IMPROVE VENT PATil CAPABILTTY 4 e ___-______.________-____m____.____._________.-_-___________-________._________.m__- ________--._--_-__-_-___________._._______m________ ____}}