ML20215L166
| ML20215L166 | |
| Person / Time | |
|---|---|
| Issue date: | 10/09/1986 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-2461, NUDOCS 8610280509 | |
| Download: ML20215L166 (36) | |
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h L3 ACRS Subcommittee Meeting Sumary/ Minutes 10 h D for Containment Requirements September 23, 1986 Washington, DC Purpose The ACRS Subcommittee on Containment Requirements met on September 23, 1986 at Washington, DC. The purpose of this meeting was to discuss:
(1) the status of the development of a Containment Performance Design Objective (CPD0) as part of the Safety Goal Policy, and (2) the develop-ment of a proposed requirements for BWR Mark I containment. The Subcom-mittee heard presentations from members of NRC Research on Item 1 and members of NRC/NRR and BWR Owners Group (BWROG) on Item 2.
Copies of the agenda and selected slides from the presentations are attached. The meeting began at 9:00 am and adjourned at 4:50 pm and was held entirely in open session. The principal attendees were as follows:
Attendees ACRS NRC BWROG C. Mark, Member G. Burdick, RES T. Pickens, NSP J. Ebersole, Member P. K. Niyogi, RES R. Diederich, PEC0 W. Kerr, Member (pm only)
J. Martin, RES K. Holtzclaw, GE D. Okrent, Member J. Costello, RES C. Siess, Member M. Taylor, ED0 C. Wylie, Member J. Hulman, NRR M. Plesset, Consultant R. Bernero, NRR D. Houston, Staff Discussion Two separate and distinct topics were reviewed at the Subcommittee meeting:
(1) the status of the development of a Containment Performance Design Objective (CPD0) as part of the Safety Goal Policy, and (2) the development of proposed requirements for BWR Mark I containment. The discussion that follows will be separated by topic subject.
0610280509 86IOGY III ACRS
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Containment Requirements Minutes September 23, 1986 4
Containment Performance Design Objective (CPD0)
G. Burdick (RES) discussed the status of the development of a CPDO. The major areas covered in his presentation were:
(1)theconclusionsofa Workshop held in May 1986, (2) the guidance given in the Safety Goal Policy, (3) the definition of a large release, (4) considerations for venting, and (5) the current form of a CPD0 under consideration. A final form revision of the CPD0 is tentatively scheduled to be issued during the First Quarter of 1987.
Burdick indicated that the CPD0 should be consistent with the Safety Goal Policy and achievable. The large release, as defined (200 Rem at one mile), would satisfy the early fatality safety goal. The overall mean frequency of a large release to the environment from a reactor accident should be less than 10-6/ year of operation. Releases by controlled venting would be restricted to 10 CFR 100 limits. RES is still considering many options in the development of a final CPDO. A future Subcommittee meeting will be scheduled to consider the final CPDO.
Subcommittee members expressed the following concerns or opinions about the CPD0 development:
(1)
C. Mark questioned whether the CPD0 was clearly for LWRs of present and advance design or would include future designs. He indicated that the CPD0 needs to be specific and that it should not address containment per se but consider the characteristics of what is contained within.
l (2)
J. Ebersole indicated that separate implementation guidelines should be developed for BWRs and PWRs. He questioned the data base from containment leak tests on the basis of pre-test preparation to l
assure the tests would pass.
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Centainment Requirements Minutes September 23, 1986 (3)
D. Okrent questioned whether the Staff had suitably considered steam explosions and whether programs are in-place to provide the He also inquired necessary information regarding this phenomena.
about the understanding of management strategies for the various He recommended that the Staff give high types of containment.
priority to the comprehensive assessment of containment failure modes, considering both internal and external events.
(4)
C. Siess suggested that any CPD0 be both achievable and demonstra-He questioned where the specific request for a CPD0 was ble.
He stated that it would be difficult written in past references.
to develop an acceptable CPD0 unless it can be defined why a CPD0 is wanted.
BWR Mark 1 Containment Requirements (Proposed)
R. Bernero (NRR) discussed a proposed generic lette,r on BWR containment performance, specifically concerned with Mark I containments but gener-He indicated that ically applicable to all BWR and PWR containments.
the regulatory basis for his proposal was contained in GDC 16, GDC 50 and the Severe Accident Policy Statement. The key elements of the proposed requirements are as follows:
(1) Hydrogencontrol-restrictiononoperationwhendeinerted(MarksI and II) and uninterruptable/ highly reliable power supply for hydrogenignitors(MarkIII).
(2) Drywell sprays - flow reduction to prevent flooding of ECCS compo-nents.
(3) Venting - to prevent containment overpressurization.
Core debris - barriers to confine or direct molten core flow.
(4)
.-.._. = ~
i Containment Requirements Minutes September 23, 1986 (5) Emergency procedures and training for above items.
Bernero indicated that he would not be influenced by on going analytical studies. He had arbitrarily (with divine guidance) decided that core melt frequencies would be at least 10'4/yr, that Mark I containment failure probabilities would be at least 50% under severe accident 1
conditions and that his simple recommended plant enhancements would only cost $1-2 million to implement. This expense level was stated to be in i
the noise level of the annual operating costs for the plant, thus obviously should be acceptable to the utilities. After implementation, I
the core melt frequency would remain unchanged (10'4/yr) while the containment failure probability was reduced to 2%. He discussed some results from a recent study at Vermont-Yankee: core melt frequency of 3 x 10-5 and containment failure probability of 7%. NRR intends to j
develop a draft generic letter on the containment requirement issue by November 19, 1986.
T. Pickens (BWROG) discussed the industry's evaluation of the proposed NRR containment requirements. The BWROG had agreed to:
(1) implement Revision 4 of Emergency Procedure Guidelines (EPGs) - scheduled for October / November 1986, (2) perform a severe accident insight review of Rev.4-EPGs,and(3)continueworkingwithNRCtobetterdefineissues for resolution. NUMARC had been requested and had accepted to review the containment issue as a generic industry issue. The Owners Group had evaluated a small number of plants, had found a wide variation in estimated costs and had identified benefits and negative impacts associ-ated with the requirements. Bernero had apparently assumed costs on the l
basis of non-safety grade, non-environmentally qualified and non-seismic equipment. The Owners Group reported that this was not possible due to the placement of this equipment in the drywell adjacent to safety systems or electrically sharing of safety grade circuits. Thus, the costs would be higher than Bernero's estimate, more on the order of
$5-20 million depending upon plant specifics.
For drywell sprays, the
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Containment Requirements Minutes September 23, 1986 Owners Group had perfonned flow tests and detennined that the spray function was lost at the recommended lower flows but that the deluge function would be retained to quench core debris.
For venting, numerous designs are still under review. Negative impacts for venting were stated to be secondary containment contamination, creation of possible explosive conditions and the deliberate release of radioactive material.
For core debris, concepts are still being studied.
Subcommittee members expressed the following concerns or opinions about the BWR Mark I containment requirements:
(1)
W. Kerr questioned the applicability of GDC 16 and GDC 50 as the basis for this effort. He was disturbed that so much emphasis is being put on the worst possible situation. He felt that more consideration should be given to reopening of MSIVs in the ATWS sequence.
(2)
D. Okrent expressed concerns that the ACRS review was being fac-tored in late, after NRR had formulated and published their posi-tion. He intends to ask the Full Committee for their feeling on this matter. He inquired about the seismic qualification of certain equipment and indicated that the seismic contribution to risk may be appreciable. He asked whether the individual utilities had enough detailed knowledge and understanding to make the deci-sion on venting during a severe accident. He asked NRR specifical-ly if a written document existed which addressed the adequacy of the phenomenological issues under consideration, including steam explosions.
(3)
J. Ebersole asked about venting guidelines to prevent core damage.
He further discussed the capability of filling the drywell solid.
L
. September 23, 1986 J
Containment Requirements Minutes C. Mark expressed a concern that the stated value of contain-(4) ment failure probability (50-90%) is not well founded and that subsequent requirements based on this should be thoroughly He also indicated that the event at Chernobyl evaluated.
should not be used to motivate the development of these requirements.
Additional meeting details can be obtained from a transcript NOTE:
of this meeting available in the NRC Public Document Room, 1717 H Street, N.W., Washington, D.C., or can be purchased from ACE-Federal Reporters, 444 North Capitol Street, Wash-l ington, DC 20001, (202) 347-3700.
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- 8 REVISED:
9/18/86 ACRS Containment Requirements Subcommittee Meeting September 23, 1986 Washington, DC
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Tentative Presentation Schedule -
i I.
Containment Performance Design Objective A.
Subcommittee Chairman Remarks C. Mark 9:00 am i
j B.
Containment Performance Design Gary Burdick 9:10 am Objective RES 4
- Status Report on Draft Position Paper
- Highlights of Workshop i
- BREAK ***
10:30 - 10:40 am i
C.
Subcommittee Remarks C. Mark 11:30 am i
- LUNCH ***
12:00 - 1:00 pm II.
BWR Mark I Containment Requirements i
i D. ' Subcommittee Chairman Remarks C. Mark 1:00 pm i
E.
NRR BWR Mark I Containment R. Bernero 1:10 pm 1
Requirements - Draft Generic Letter NRR
- BREAK ***
2:30 - 2:40 pm I
F.
BWROG/IDCOR Assessment Terry Pickens 3:30 pm i
NSP/BWROG I
G.
Subcommittee Remarks C. Mark 4:45 pm i
- ADJOURN ***
5:00 pm i
Contact:
Dean Houston l
(202)634-3267 l
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BACKGROUND ED0 MEMORANDUM TO RES/NRR TO INITIATE A PLAN FOR DEVELOPING A CPD0 - JULY 29, 1985 DRAFT CPD0 PROGRAM PLAN TO RES, NRR, ACRS - OCTOBER,1985 BRIEFING TO ACRS SUBCOMMITTEE ON SAFETY PHILOSOPHY, TECHNOLOGY AND CRITERIA - OCTOBER 9, 1985 INTERVIEW 0F SELECTED EXPERTS FOR THEIR VIEWS ON CPD0 -
NOVEMBER 1985 - JANUARY 1986
'l INITIAL DRAFT CPD0 OPTIONS AND FRAMEWORK OF IMPLEMENTATION AFPROACH FOR REVIEW - FEBPUARY 1986 CPD0 PLAN TO ED0 - MARCH 1986 ACRS SUBCOV.MITTEE BRIEFING - MARCH 12, 1986 CPD0 WORKSHOP AT HARPERS FERRY - MAY 12-13, 1986 COMMISSION POLICY STATEMENT ON SAFETY G0ALS - JUNE 1986 ED0 MEMO TO RES/NPR IN RESPONSE TO THE CPD0 PROGRAM PLAN:
i CONF 0PM THE CPD0 PROGRAM TO THE SAFETY G0AL POLICY STATEMENT GUIDANCE - JULY 30, 1986 i
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CPD0 WORKSHOP MAJOR CONCLUSIONS CONTAINMENT IS A NECESSARY ELEMENT OF A DEFEFSE-IN-DEPTH PHILOSOPHY l
A MINIMUM CONTAINMENT PERFORMANCE LEVEL NEEDS TO BE SPECIFIED A QUANTITATIVE,
- AND, TO THE EXTENT FEASIBLE, MECHANISTIC CPD0 IS PREFERABLE CPD0 AND ASPECTS PERTAINIflG TO IT SHOULD BE WELL-DEFINED AND UNAMBIGUOUS ONE OF THE PROPOSED CPD0 OPTIONS WAS CONSIDERED PROMISING AS A BASIS FOR FURTHER WORK 89
IMPORTANT ISSUES i
DEFINITION OF A LARGE RELEASE CONSISTENCY AMONG THE SAFETY G0ALS AND THE CPD0 DEFENSE IN DEPTH CRITERIA FOR VENTING ACHIEVABILITY 1
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d DEFINITION OF LARGE RELEASE RATIONALE:
O PPOMPT FATALITY SAFETY GOAL:
AVERAGE INDIVIDUAL RISK WITHIN A MILE FPOM SITE BOUNDARY < 5X10-/(EF)/RY (EARLY FATALITIES PER REACTOR YEAR) 0 IF R IS THE LARGE RELEASE LOWER LIMIT RISK TO INDIVIDUALS IN THE DOWNWIND SECTOR TO BE IN CONFORMANCE WE MUST HAVE R_ 1 5X10-7(EF)/RY 16 OR, R 1 8X10-6(gg)fgy ASSUMING UNIFORM POPULATION AND 16 SECTORS.
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DEFINITION OF LARGE RELEASE RATIONALE (CONT.):
FOR DEFENSE-IN-DEPTH AND CPD0 PURPOSES WE COULD TAKE R =
AND HAVE:
DEFINITION:
A LARGE RELEASE IS ANY PELEASE OF RADIONUCLIDES TO THE ENVIRONMENT WHICH WOULD LIKELY CAUSE ONE OR MORE EARLY FATALITIES.
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l EF THE LARGE PELEASE THUS DEFINED SATISFIES THE PROMPT FATALITY SG BY ABOUT AN ORDER OF MAGNITUDE AND COMPLIES WITH SG IMPLEMENTATION GUIDELINE ON FREQUENCY OF LARGE RELEASE.
0THER CONSIDERATIONS VENTING SEVERAL VENTING-RELATED ACTIVITIES ARE UNDER WAY IF THE AGENCY.
RESULTS WILL BE INCORPORATED INTO THE CPDO.
LIMITING VENTING LEVELS ARE BEING STUDIED.
IDEALLY, VENTING SHOULD PREVENT HIGH PRESSURE BUILD UP AND VENTS SHOULD BE CLOSED WITH HIGH RELIABILITY BEFORE CORE DAMAGE OCCURS.
STAFF CONFIDENT THAT EARLY FATALITIES VERY UNLIKELY FROM RELEASE OF 0.1% OF NONNOBLE INVENTORY.
RELEASE OF NOBLE GAS INVENTORY LIKELY IN SEVERE ACCIDENTS.
NOBLE GAS INVENTORY RELEASE APPFARS WITHIN PPOMPT FATALITY GOAL.
POLITICAL,
- LEGAL, AND OTHER
(?)
QUESTIONS INVOLVED WITH NOBLE GAS VENTING.
DEFENSE IN DEPTH 4
THE DEGREE TO WHICH PRVENTION VS MITIGATION TRADEOFFS COUL D BE MADE.
THE CURRENTLY CONSIDERED CPD0 1.
CONTAINMENTS SHOULD SURVIVE ALL BUT HIGHLY UNLIKELY SEVERE ACCIDENTS WITHOUT OCCURRENCE OF A
LARGE RELEASE.
THE AGGREGATE FREQUENCY OF A "LARGE RELEASE" 0F RADIONUCLIDES TO THE ATMOSPHERE FOR ALL SEVERE CORE DAMAGE ACCIDENT SEQUENCES SHOULD NOT EXCEED ONE IN A MILLION REACTOR YEARS A "LARGE RELEASE" IS DEFINED AS RELEASE OF RADIONUCLIDES TO THE ENVIRONMENT THAT WOULD LIKELY RESULT IN EARLY FATALITIES.
EQUIVALENTLY, "LARGE RELEASE" CAN BE TAKEN TO MEAN " LIFE THREATENING RELEASE."
2.
CONTROLLED VENTING OF CONTAINMENT SHOULD BE SUCH THAT PELEASE OF RADIONUCLIDE SPECIES TO THE ATMOSPHERE NOT EXCEED 10 CFR 100 LIMITS.
1 3.
EMPHASIS ON DEFENSE-IN-DEPTH SHOULD BE RETAINED.
THE CONDITIONAL PROBABILITY OF A LARGE RELEASE" FROM A CORE DAMAGE ACCIDENT SHOULD NOT EXCEED 0.1 (0.01 FOR NEW PLANTS),
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3 GENERIC LETTER ON BWR CONTAINMENT PERFORMANCE THE SETTING:
PLANT EVALUATIONS UNDER THE SEVERE ACCIDENT POLICY STATEMENT THE KEY REGULATIONS:
GDC 16 AND GDC 50 THE SUBJECTS:
37 BWRS WITH PRESSURE SUPPRESSION CONTAINMENTS THE METHOD:
A GENERIC LETTER OF REQUIREMENTS TO IMPLEMENT CHANGES BASED ON GENERIC EVALUATION e
4
7 A BWR - MARK I FOR REFERENCE BEFORE e
CORE MELT FREQUENCY:
1x10-4/YR A FULL SPECTRUM 0F SEQUENCES INCLUDING BLACK 0UTS e
CONTAINMENT CAPABILITY:
UNCERTAIN AND VARIABLE BUT ASSUME 1 OUT OF 2 CORE MELTS GIVES FAIRLY LARGE RELEASE AFTER e
CORE MELT FREQUENCY:
1x10-4/HR IPE FOR FRONT END MAY REDUCE BUT NO CREDIT IS TAKEN HERE-e CONTAINMENT CARABILITY:
SUBSTANTIAL ASSURANCE THAT CONTAINMENT WILL MITIGATE CONSEQUENCES, DEGREE VARIABLE FROM PLANT TO PLANT BUT 1 OUT OF 50 CORE MELTS GIVING A FAIRLY LARGE RELEASE SHOULD BE REPRESENTATIVE
8 HYDROGEN CONTROL PROPOSED REQUIREMENTS CHANGE TECH. SPEC. AT END OF OPERATION FROM 24, HOUR e
ALLOWANCE TO 12-HOUR ALLOWANCE OF NON-INERTED OPERATION AI REDUCED POWER e
PERMIT 12-H0VR PERIOD AT REDUCED POWER WITHIN THE OPERATING CYCLE TO SEARCH FOR UNIDENTIFIED LEAKAGE MTIONALE e
DEINERTING TYPICALLY TAKES 4-8 HOURS e
LEAKAGE INSPECTION AND MINOR REPAIR CAN BE REASONABLY ACHIEVED IN 4-8 HOURS e
REDUCED POWER ( 6 33%) SUBSTANTIALLY REDUCES SHORT-LIVED l
FISSION PRODUCT INVENTORY AND DYNAMICS OF POSSIBLE ACCIDENTS' l
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- e DRYWELL SPRAY PROPOSED REQUIREMENTS e
REDUCE DESIGN SPRAY RATE (CHANGE N0ZZLES) TO AB.0VT 10% OF PRESENT VALUE e
PROVIDE AC-POWERED BACKUP WATER SUPPLY FOR SPRAY AND AC-INDEPENDENT WATER SUPPLY, AVAILABILITY BY REMOTE MANUAL OPERATION OR BY SIMPLE RELIABLE PROCEDURE DESIRABLE e
MAKE ALTERNATE WATER SOURCES AVAILABLE TO COOL CORE DIRECTLY e
90/10 MODE OF RHR OPERATION RATIONALE a
e WATER SUPPLIES AND EQUIPMENT ARE ALREADY AVAILABLE FOR LOWER FLOWS e
LOWER FLOWS PROVIDE ALL BENEFITS EXCEPT LOW 21 T DECAY HEAT REMOVAL AND DO NOT RAPIDLY FLOOD CONTAINMENT e
ASSURED DRYWELL SPRAY SUBSTANTIALLY REDUCES PROBABILITY AND SIGNIFICANCE OF DRYWELL FAILURE OR SUPPRESSION POOL BYPASS
,+
10 PRESSURE CONTROL PROPOSED REQUIREMENTS e
RELIABLE CAPABILITY TO VENT WETWELL AT EPG PRESSURE LEVEL WITH OR WITHOUT AC POWER.
FOR VENTING WITHOUT AC POWER MANUAL PROCEDURE IN ADVANCE MAY BE USED IF NITROGEN PURGE IS AVAILABLE e
VENT OF 18-INCH DIAMETER OR GREATER DESIRABLE
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e ABILITY TO VENT SLOWER SEQUENCES THROUGH STANDBY GAS TREATMENT SYSTEM e
BURST RESISTANCE DUCTING IN REACTOR BUILDING TO MINIMIZE COMPLICATIONS RATIONALE e
RELIABLE VENTING PREVENTS UNCONTROLLED OVERPRESSURE FAILURE WHICH CAN CAUSE CORE MELT e
VENTING WITH DRYWELL SPRAY GIVES GREAT ASSURANCE OF RELEASE MITIGATION l
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11 CORE DEBRIS PROPOSED REQUIREMENTS e
ASSURE RETENTION OF WATER AT LEAST 3 FEET DEEP IN TORUS ROOM IF TORUS LEAKS ENTIRE CONTENTS DESIRABLE e
CONCRETE CURBS OR OTHER BARRIERS WHICH WOULD RETARD DEBRIS ATTACK OF DRYWELL SHELL e
AVOID LOSS OF REC 0VERY SYSTEMS FROM WETTING BY TORUS ROOM WATER l
RATIONALE e
DRYWELL FAILURE BY DEBRIS ATTACK IS MADE LESS LIKELY AND LESS SIGNIFICANT BY DRYWELL SPRAY AND VENTING e
RETENTION OF TORUS WATER ENSURES DEBRIS QUENCHING AND SHOULD FACIFITATEACCIDENTRECOVERY
)
CHRONOLOGY e
JUNE 16, 1986:
MEETING WITH BWROG/IDCOR PROPOSED A GENERIC LETTER, PRESCRIPTIVE SOLUTION, BY BACKFIT e
JUNE 30, 1986:
VERMONT YANKEE COMMITS TO GOV. KUNIN TO DO A SPECIAL 60-DAY CONTAINMENT STUDY e
JULY 25, 1986:
BOSTON EDISON COMPANY BOARD ANNOUNCEMENT ON PILGRIM CONTAINMENT e
SEPTEMBER 11, 1986:
MEETING WITH BWROG TO COMPARE BACKFIT NOTES AND STRAWMAN GENERIC REQUIREMENTS e
SEPTEMBER 11, 1986:
MEETING WITH VERMONT YANKEE TO REVIEW CONTAINMENT STUDY e
SEPTEMBER 23, 1986:
NRC/IDCOR MEETING ON BWR/ MARK I ANALYSES e
SEPTEMBER 23, 1986:
ACRS SUBCOMMITTEE ON CONTAINMENT PERFORMANCE TO DISCUSS HARPERS FERRY WORKSHOP RESULTS AND BWR CONTAINMENT GENERIC APPROACH i
e SEPTEMBER 24, 1986:
ACRS SUBCOMMITTEE ON CLASS 9 ACCIDENTS TO DICUSS BWR/ MARK I ANALYSES AND SEVERE ACCIDENT PROGRAM l
e OCTOBER 23, 1986:
NRC LETTERiTO VERMONT YANKEE WITH COMMENTS AND QUESTIONS ON LICENSEE'S CONTAINMENT STUDY NOVE(BEQ 13, 1986 (MORNING):
TECHNICAL INTERCHANGE MEETING e
WITH;'BW$0G PRIOR TO CRGR BRIEFING
i e
NOVEMBER 13, 1986 (AFTERNOON):
VERMONT YANKEE MEETING WIT.l NRC TO RESPOND TO NRC QUESTIONS e
NOVEMBER 19, 1986:
CRGR REVIEW OF DRAFT GENERIC LETTER ON BWR CONTAINMENT REQUIREMENTS (T0 BE PUBLISHED FOR COMMENT) e DECEMBER 17, 1986:
ISSUE DRAFT GENERIC LETTER ON BWR CONTAINMENT REQUIREMENTS FOR PUBLIC COMMENT e
DECEMBER 24, 1986:
NRC LETTER TO VERMONT YANKEE TO GIVE TENTATIVE FINAL REVIEW BASED ON POSITION OF DRAFT GENERIC LETTER e
APRIL 1987:
ISSUE FINAL GENERIC LETTER ON BWR CONTAINMENT REQUIREMENTS l
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SEVERE ACCIDENT CONTAINMENT POLICY INDUSTRY EVALUATIONS l
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SEPTEMBER 23, 1986 WASHINGTON, DC 1
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IDCOR/BWROG/ UTILITY EVALUATIONS:
o WIDE VARIATION IN ESTIMATED COST o EVALUATIONS PERFORMED ON SMALL NUMBER OF PLANTS o OBJECTIVES APPEAR GENERIC - ENHANCEMENTS APPEAR PLANT SPECIFIC o QUALITATIVE ASSESSMENT 3 OF BENEFITS AND NEGATIVE IMPACTS PERFORMED i
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ELEMENT 1 - HYDR 0 GEN OBJECTIVE:
PREVENT HYDROGEN COPSUSTION CAUSED FAI LURE REQUIREMENTS:
A.
0XYGEN CONTROL (f%RK I AND f%RK II)
B.
HYDROGEN CONTRO L (MARK III)
IDCOR/BWROG EVALUATIONS:
o 0XYGEN CONTROL BY NITROGEN INERTING ADEQUATE FOR fMRK I AND MARK IIs.
o LIMITING THE TIME DEINERTED UNDER REVIEW.
o MARK III HYDR 0 GEN CONTROL BEING ADDRESSED BY HYDROGEN CONTROL OWNERS' GROUP (HC0G).
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O.
BOOG PROFOSAL 1EDG to supply the design criteria for a backup power supply to the hydrogen igniters.
- Backup power supply need not be safety related
- Identify impact of addressing Severe Accidents on the design of a backup power supply.
- Ntznber of igniters required in the event of an SB0
- Make use of existing data base and criteria
- Additional testing, only if necessary, to follow ompletion of current Test Program - end of this year Responsibility of individual Mark III owners with support of POOG as required.
- Define backup power supply source
- Define associated costs
- Meet and discuss with the NRC the details of the design, costs, and benefits of a backup power supply to the igniters
- Decision and timing for proceeding
,_m
ELEMENT 2 - SPRAYS GJECTIVE:
SPRAY WATER TO:
1.
QUENCH DEBRIS (PRIMARY) 2.
SCRUB AEROSOLS (SECONDARY) 3.
LWER PRESSURE (SECONDARY) 4.
COOL VULNERABLE EQUIPMENT (SECONDARY)
REQUIREMENTS:
1.
SPRAY IN DRYWELL 2.
BACKUP WATER SOURCES AND PUMPS
- HOSE CONNECTIONS
- USE OF FIREl% INS IDCOR/BWROG EVALUATIONS:
o TYPICAL SPRAY CAPACITY 5 - 10,000 GPM/ HEADER O
CONCEPTS CONSIDERED o
CONNECTIm TO H0SE STATIM IN REACTm BUILDING
- APPRMIMATE FLN PROVIDED 200 GPM i
- DES NOT PROVIDE SPRAY l
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ELEMENT 2 - SPRAYS (Continued) o CROSS TIES FROM DIESEL FIRE PUMPS TO RHR
- APPR0XIMATE FLCW PROVIDED 1/2 0F FIRE PUMP RATING
- CLOSE OFF APPR0XIMATELY 70% T N0ZZLES TO ACHIEVE SPRAY o
FLOW RATES IDENTIFIED APPEAR ADEQUATE o
DEBRIS QUENCHING DOES NOT REQUIRE SPRAY o
POTENTIAL BENEFIT / RISK WARRANTS FURTHER STUDY
ELEMENT 3 - PRESSURE OBJECTIVES:
1.
AVERT UNCONTROLLED OVERPRESSURE FAILURE 2.
CONTROL RELEASE PATH (SCRUBBING)
REQUIREMENTS:
1.
SUBSTANTIAL CAPABILITY TO VENT WETWELL 2.
REMOTE / RELIABLE CONTROL OF VENT VALVE 3.
ABILITY TO RECLOSE VENT IDCOR/BWROG EVALUATIONS:
o CONCEPTS CONSIDERED o
UPGRADE DUCTING AND STANDBY GAS TREATMENT SYSTEM (SBGTS) TO CONTAINMENT DESIGN PRESSURE CAPABILITY
- NOT FEASIBLE TO UPGRADE SBGTS o
HARDPIPED BYPASS AROUND SBGTS o
1%RDPIPED DEDICATED VENT o
COSTS ARE C WPARABLE FOR HARDPIPED WTIWS
ELEMENT 3 - PRESSURE (Continued)
O VENT SIZING UNDER REVIEW o
ATWS o
DHR o
NEGATIVE IMPACTS NEEDING FURTHER REVIEW o
SECONDARY CONTAINMENT CONTAMINATION o
DELIBERATE RELEASE i
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o ELEMENT 4 - C WE DEBRIS OBJECTIVE:
REDUCE LIKELIHOOD E FAILURE BY DIRECT ATTACK REQUIREMENTS:
1.
USE PRACTICAL DEBRIS RETARDING BARRIERS 2.
CWSERVE SUPPRESSIm P0OL WATER AS A QUENCHING POOL IDC m/BWROG EVA LUATIONS:
o DRYWELL o
CONCEPTS CONSIDERED PLljG IN PEDESTAL OPENING INCREASE SUMP SIZE INSIDE PEDESTA L CURB OJTSIDE PEDESTA L OPENING CURB AT DRYWELL LINER /FLOCR JUNCTION ADDITIWAL PEDESTA L OPENINGS TO PROMOTE EVEN DISTRIBUTION o
NEGATIVE IMPACTS LOCA CWSIDERATIONS SEISMIC INTERACTIWS ALAPA CWCERNS
ELEMENT 4 - CORE DEBRIS (Continued) c OVA LITATIVE BENEFIT LOW DEPENDENT ON ANALYTICAL MODELS OF DEBRIS
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MOBILITY WHICH ARE VERY UICERTAIN o
WETWELL o
MCST PLANTS CURRENTLY HAVE CAPABILITIES TO HOLD WATER IN TORUS CHAMBER OR PROVIDE PROTECTIm TO CRITICAL EQUIPMENT IN C GNER R0mS o
QUALITATIVE BENEFITS LOW o
NO NEGATIVE IMPACTS o
NO FURTHER STUDY WARRANTED l
l
r, ELEMENT 5 - TRAINING AND PROCEDURES CBJECTIVE:
ENSURE OPERATCRS ARE READY TO USE PLANT FEATURES TO BEST ADVANTAGE IN SEVERE ACCIDENTS REQUIREMENTS:
C U:4R SYMPTCM BASED STRATEGIES (INTEGRATED) 1.
J 2.
REMOVAL OF UNNECESSARY INHIBITICNS 3.
TRAINING / PROCEDURES IDCOR/BWROG EVALUATIONS:
o REV. 4 IMPLEMENTATION BY ALL UTILJTIES C CNSISTENT WITH PREVIOJS PGT-TMI COMMITMENT o
PROPCSE REVIEW 0F REV. 4 WITH INSIGHTS FRCM SEVERE ACCIDENT STUDIES i
I,.
CONCLUSIONS - BWR EXECUTIVE MEETING o
AUGUST 19 MEETING - 20 0F 23 BWROG UTILITIES REPRESENTED o
CONTINUE CONSTRUCTIVE DIALOGUE WITH NRC o
AGREEMENTS:
COMMIT TO IMPLEMENTATION OF REVISION 4 TO EPGS NUMARC CONTACTED TO CONSIDER SEVERE ACCIDENT CONTAINMENT ISSUE AS A GENERIC INDUSTRY ISSUE CONTINUE WORKING WITH NRC TO BETTER DEFINE ISSUES
)
FOR RESOLUTION PROPOSE TO BWROG SEVERE ACCIDENT INSIGHT REVIEW 0F EPG REV. 4 l
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