ML20138P157
| ML20138P157 | |
| Person / Time | |
|---|---|
| Issue date: | 11/01/1985 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Asselstine, Palladino, Roberts NRC COMMISSION (OCM) |
| References | |
| REF-GTECI-A-44, REF-GTECI-EL, TASK-A-44, TASK-OR NUDOCS 8511060451 | |
| Download: ML20138P157 (64) | |
Text
/# *** %\, . UNITED 87 ATE 8 t f
/ NUCLEAR REGULATORY COMMISSION i wasmenorom. o. c. aseos
,,,,, NOV 01 m MEMORANDUM FOR: Chairman Palladino Comissioner Roberts Comissioner Asselstine Comissioner Bernthal Comissioner Zech FROM:
- William J. Dircks Executive Director for Operations
SUBJECT:
US! A-44, STATIM BLACK 0UT The staff has received questions on US! A-44, Station Blackout, from a
Comissioners Asselstine, Bernthal, Roberts and Zech. The enclosure to this memo provides the staff's response to thtse questions.
Egned! W4am 1. ~ . .a William J. Dircks Executive Director for Operations Encisoure:
As Stated Above cc w/encli SECY OGC OPE CONTACT: Alan M. Rubin, NRR // o (, O V W YA x28303 f.> 4L Cons ( COLL fni. i
f QUESTION 1. BOTH THE ACRS AND THE CRGR RECOMMEND THAT GREATER EMPHASIS BE PLACED ON COORDINATING THE RESOLUTION OF OTHER SAFF.TY ISSUES WITH THE STATION BLACKOUT ISSUE. IS IT NECESSARY AND AS COST EFFECTIVE TO APPROACH THE PROBLEM PIECEMEAL RATHER THAN AFTER THE OTHER ISSUES ARE RESOLVED 7 ANSWER.
ON FEBRUARY 26, 1985, THE STAFF MET WITH AN ACRS SUBCOMMITTEE TO DISCUSS THE PROPOSED RESOLUTION OF US! A-44 AND TO ADDRESS PREVIOUS COMMENTS FROM ACRS. AFTER THIS MEETING, THE ACRS SENT A ,
LETTER TO THE ED0 DATED MARCH 12, 1985, STATING THAT THEY BELIEVE THE NRC STAFF HAS TAKEN APPROPRIATE ACCOUNT OF ACRS RECOMMENDA-TIONS INCLUDING A RECOMMENDATION TO COORDINATE RELATED ISSUES.
THE COORDINATION BETWEEN USI A-44 AND RELATED GENERIC SAFETY ISSUES IS DISCUSSED ON PAGES 30 THROUGH 37 0F NUREG-1109. WE BELIEVE THAT THIS COORDINATION WILL BE EFFECTIVE IN ACCOM-PLISHING THE FOLLOWING OBJECTIVES: (1) A TIMELY RESOLUTION OF IMPORTANT GENERIC SAFETY ISSUES, AND (2) AVOIDING INCONSISTENT AND/OR OVERLAPPING REQUIREMENTS AND THE EXPENDITURE OF UNNECES-SARY RESOURCES BY BOTH NRC AND INDUSTRY.
ROBERTS /EDO 10/10/85
f QUESTION 2. THE CRGR RECOMMENDS THAT A ZERO-HOUR DURATION CATEGORY BE INCLUDED, YET THE STAFF HAS ELECTED ONLY FOUR-HOUR AND EIGHT-HOUR CATEGORIES. WHY7 ANSWER.
THE DRAFT REGULATORY GUIDE PROVIDES RECOMMENDATIONS FOR MIN! MUM STATION BLACKOUT COPING CAPABILITY OF FOUR OR EIGHT HOURS DEPENDING ON SPECIFIC PLANT CHARACTERISTICS. THE APPROACH WAS TAKEN SO THAT LICENSEES WOULD HAVE A RELATIVELY SIMPLE METHOD i TO DETERMINE A STATION BLACKOUT COPING CAPABILITY TO COMPLY WITH THE PROPOSED RULE. USE OF THIS METHOD WOULD RESULT IN STATION BLACK 09T BEING A RELATIVELY SMALL CONTRIBUTOR TO TOTAL CORE MELT FREQUENCY. OTHER METHODS COULD BE USED BY LICENSEES TO DETERMINE AN ACCEPTABLE COPING CAPABILITY. IN FACT, THE GUIDE SPECIFICALLY STATES THAT TIMES OTHER THAN FOUR OR EIGHT HOURS COULD BE ACCEPTABLE.
THE REASONS FOR NOT INCLUDING A "ZERO-HOUR" CATEGORY ARE DISCUSSED BELOW.
t ROBERTS /EDO 10/10/85
f QUESTION 2. (CONTINUED) 0 A REVIEW OF THE TECHNICAL ANALYSIS AND ESTIMATES OF CORE MELT FREQUENCIES AND THE RESULTING SEVCRE CONSEQUENCES FOR STATION BLACKOUT EVENTS, INCLUDING UNCERTAINTIES, LED TO THE STAFF'S RECOMMENDATION THAT, FOR ADDITIONAL DEFENSE-IN-DEPTH, ALL PLANTS SHOULD BE ABLE TO COPE WITH A STATION BLACK 0UT FOR SOME MINIMUM DURATION AND THAT PROCEDURES AND TRAINING FOR STATION BLACKOUT EVENTS OF THAT DURATION BE IMPLEMENTED.
O EVEN FOR PLANTS WITH UNUSUALLY HIGH REDUNDANCY OF ONSITE ,
EMERGENCY AC POWER SYSTEMS WHICH MIGHT BE INCLINED TO JUSTIFY A ZERO-DURATION, COMMON MODE FAILURES CAN NOT BE IGNORED. SUCH FAILURES HAVE OCCURRED IN THE PAST, AND THEY CAN NOT BE ELIMINATED ENTIRELY IN THE FUTURE. THE PROPOSED RESOLUTION OF USI A-44 ORIGINALLY INCLUDED GUIDANCE TO REVIEW THE OFFSITE AND ONSITE AC POWER SYSTEMS FOR POTENTIAL SINGLC POINT VULNERABILITIES TO MINIMlZE COMMON MODE FAILURES. CRGR RECOMMENDED THA1 THIS DE TAKEN OUT OF THE " REGULATORY POSITION" GECTION OF THE REGULATORY GulDE BECAUSE LICENSEES HAVE ALREADY DEEN REQUIRED TO, PROVIDE REDUNDANT AND INDEPENDENT ONSITE EMERGENCY AC POWER SYSTEMS. THE STAFF AGREED WITH THE RECOMMENDATION.
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f l
QUESTION 2. (CONTINUED)
HOWEVER, IT IS IMPORTANT TO NOTE THAT EVEN IF COMMON MODE FAILURES FROM COMPONENT OR SYSTEM DESIGN ARE REDUCED TO THE EXTENT PRACTICAL, OTHER WAYS OF COMMON MODE FAILURE INCLUDING MAINTENANCE AND EXTERNAL EVENTS STILL REMAIN AS A THREAT. THE STAFF !$ AWARE, THROUGH LERS AND OTHER REPORTS, THAT SINGLE POINT VULNERABILITIES HAVE BEEN IDENTIFIED, AND WHEN IDENTIFIED, THEY ARE CORRECTED. IF UNCORRECTED OR UNIDENTIFIED, SUCH FAILURES COULD LEAD TO LARGER ESTIMATES OF CORE MELT FREQUENCY AT SPECIFIC PLANTS THAN ASSUMED IN THE STAFF'S ESTIMATES IN NUREG-1032. ,
I O ALL PLANTS ALREADY HAVE THE ABILITY TO COPE WITH A STATION BLACK 0UT FOR SOME PERIOD OF TIME. MEETING SOME MINIMUM "NON-ZER0" DURATION WOULD NOT BE DIFFICULT TO SHOW.
, em i
l ROBERTS /EDO 10/10/85 i
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t QUESTION 3. THE STAFF HAS CONCLUDED, ACCORDING TO SLIDE 6, THAT THE RULE WOULD PROVIDE A SUBSTANTIAL INCREASE IN THE OVERALL PROTECTION OF THE PUBLIC HEALTH AND SAFETY, PAGE 1 0F THE STAFF'S REGULATORY l
ANALYSIS (ENCLOSURE 2 TO SECY-85-163) INDICATES l THAT FOR SOME PLANTS STATION BLACKOUT CAN BE AN IMPORTANT CONTRIBUTOR TO A TOTAL 8118 THAT IS ITSELF SMALL. PAGE 2 INDICATES THAT THIS RISK COULD BE AS HIGH AS 10-4 PER REACTOR YEAR FOR i SOME PLANTS. PAGE 3 INDICATES THAT THE GENERAL OBJECTIVE OF THE PROPOSED RULE IS TO REDUCE THE -
TOTAL RISK BY MAKING STATION BLACKOUT A t
l RELATIVELY SMALL CONTRIBUTOR. IF, AS I UNDERSTAND TO BE THE CASE, OTHER RELATIVELY IMPORTANT CONTRIBUTORS TO RISK WILL CONTINUE TO EXIST AFTER THIS ONE IS REDUCED, HOW DOES REDUCING THIS ONE ALONE PROVIDE A SUBSTANTIAL INCREASE IN OVERALL PROTECTION 7 a.M.
THE PROPOSED RESOLUTION OF US! A-44'WOULD PROVIDE A SUBSTANTIAL INCREASE IN PROTECTION FROM STATION BLACKOUT EVENTS. SINCE STATION BLACKOUT CAN BE A DOMINANT CONTRIBUTOR TO CORE DAMAGE ROBERTS /EDO 10/10/85
't QUESTION 3. (CONTINUED)
FREQUENCY, AND CONTAINMENT HEAT REMOVAL SYSTEMS ARE UNAVAILABLE WITHOUT AC POWER, THERE WOULD BE AN OVERALL INCREASE IN PUBLIC HEALTH AND SAFETY. IT IS CORRECT THAT OTHER NON-STATION BLACK 0UT RISK CONTRIBUTORS WOULD CONTINUE TO EXIST. FOR ADDITIONAL l
DISCUSSION ON THIS QUESTION, SEE THE RESPONSE TO QUESTION l NUMBER 1.A FROM COMMISSIONER ZECH.
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t QUESTION 4. IT APPEARS THAT THE STAFF IN MAKING ITS COST-BENEFIT ANALYSIS HAS ASSUMED THAT ALL PLANTS CAN PRESENTLY COPE WITH A STATION BLACKOUT FOR ONLY TWO HOURS. DOESN'T THAT ASSUMPTION BIAS THE COST-BENEFIT ANALYSIS AGAINST PLANTS ALREADY HAVING A LONGER COPING CAPABILITY?
ANSWER.
ALTHOUGH PLANTS MAY HAVE THE CAPABILITY TO COPE WITH A STATION BLACK 0UT FOR A SPECIFIC DURATION (I.E., "HAVING THE CAPABILITY" MEANS NO HARDWARE MODIFICATIONS ARE NECESSARY TO COPE FOR THAT ,
PERIOD OF TIME), CERTAIN OPERATOR ACTIONS WOULD BE NECESSARY TO ASSURE THE PLANT COULD SUCCESSFULLY COPE WITH, AND RECOVER FROM, A STATION BLACKOUT. WITHOUT ADEQUATE PROCEDURES AND TRAINING, THE LIKELIHOOD OF PROPER OPERATOR ACTIONS IS UNCERTAIN.
THEREFORE, THE STAFF ASSUMED IN ITS COST-BENEFIT ANALYSIS THAT PROCEDURES AND TRAINING WOULD MINIMIZE OPERATOR ERRORS AND THEREBY WOULD SIGNIFICANTLY IMPROVE THE PROBABILITY OF SUCCESS-FULLY COPING WITH A STATION BLACK 0UT EVENT. THIS ASSUMPTION DOES NOT BIAS THE COST-BENEFIT ANALYSIS AGAINST PLANTS HAVING LONGER COPING CAPABILITY, UNLESS PROCEDURES ARE ALREADY IN PLACE FOR THE LONGER DURATION. IF SUCH PROCEDURES DO EXIST FOR THE STATION BLACK 0UT DURATION, NOTHING MORE WOULD BE REQUIRED OF THOSE LICENSEES TO COMPLY WITH THE PROPOSED RULE.
ROBERTS /EDO 10/10/85
t QUESTION 5. THE STAFF PROPOSES ONLY TWO CHOICES FOR COPING DURATION, FOUR HOURS OR EIGHT HOURS, AND WOULD REQUIRE JUSTIFICATION, INCLUDING A COST-BENEFIT ANALYSIS, FOR COPING TIMES OF SHORTER DURATION.
. DOES THIS NOT STAND BACKFIT CONSIDERATIONS ON THEIR HEAD? THE BACKFIT RULE IS INTENDED TO ASSURE THAT EXCEPT FOR THOSE NECESSARY TO RESOLVE AN IMMEDIATE AND REAL THREAT TO PUBLIC HEALTH AND SAFETY, ONLY THOSE REGULATORY REQUIREMENTS DEMONSTRATED BY THE COMMISSION TO PROVIDE A SUBSTANTIAL INCREASE IN OVERALL PROTECTION AND TO BE COST-BENEFICIAL WILL BE IMPOSED. IT WAS NOT INTENDED TO REQUIRE THAT LICENSEES JUSTIFY THAT GREATER REQUIREMENTS ARE NEITHER NECESSARY NOR' COST-BENEFICIAL.
ANSWER, a
THE APPROACH TO THE STAFF'S PROPOSED RESOLUTION OF USI A-44, WHICH WOULD REDUCE THE RISK FROM STATION BLACK 0UT EVENTS, IS TO REQUIRE PLANTS TO BE ABLE TO COPE WITH A STATION BLACK 0UT OF SOME DURATION. THE PROPOSED RULE SPECIFIES THIS REQUIREMENT, BUT THE RULE'IS NOT SPECIFIC AS TO A REQUIRED DURATION. THE DRAFT REGULATORY GUIDE PROVIDES A SIMPLE METHOD THAT LICENSEES ROBERTS /ED0 10/10/85 1
QUESTION 5. (CONTINUED)
MAY USE TO DETERMINE THE DURATION. LICENSEES MAY CHOOSE TO USE ALTERNATE METHODS AND JUSTIFY OTHER DURATIONS AS WELL. THIS DOES NOT APPEAR TO CONFLICT WITH THE BACKFIT RULE. IN DEVELOPING THE FOUR AND EIGHT-HOUR CATEGORIES FOR COPING WITH STATION BLACK 0UT EVENTS IN THE DRAFT REGULATORY GUIDE, THE STAFF UTILIZED THE BEST INFORMATION AVAILABLE TO ANALYZE SIGNIFICANT FACTORS AND TO ESTIMATE THE FREQUENCY OF LOSSES OF ALL AC POWER. THIS INCLUDED ACTUAL ,
LOSS-OF-OFFSITE-POWER EXPERIENCE AND THE RELIABILITY OF ONSITE EMERGENCY AC POWER SYSTEMS. AC POWER RELIABILITY, AND THE ABILITY TO RESTORE AC POWER IF IT WERE LOST FROM PREFERRED SOURCES, ALSO DEPENDS IN PART ON THE AVAILABILITY OF OTHER NEARBY OR ONSITE NON-SAFETY-RELATED POWER SOURCES (E.G.,
PEAKING GAS TURBINES). FOR MOST PLANTS, NRC DOES NOT HAVE INFORMATION ON THE AVAILABILITY OF THESE ALTERNATE SOURCES OF AC POWER SINCE THEY ARE NOT SAFETY-RELATED AND ARE NOT PART OF THE NORMAL PLANT REVIEW BY NRC STAFF. THE STAFF BELIEVES A STATION BLACKOUT COPING CAPABILITY OF LESS THAN FOUR HOURS COULD BE ACCEPTABLE FOR SOME PLANTS BASED ON THE AVAILABILITY OF ALTERNATE SOURCES OF AC POWER-AS WELL AS THE EXISTENCE QF PROCEDURES TO RESTORE POWER FROM THESE SOURCES. HOWEVER, BECAUSE OF SIGNIFICANT DIFFERENCES BETWEEN THE NUMBER ROBERTS /ED0 10/10/85
t
-QUESTION 5. (CONTINUED)
AND AVAILABILITY OF THESE. SOURCES FROM PLANT TO PLANT, THE STAFF BELIEVES DURATIONS OF LESS THAN FOUR HOURS SHOULD BE DETERMINED BY LICENSEES ON A PLANT-BY-PLANT BASIS, i
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.a ROBERTS /EDO 6
10/10/85 ,
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- 1. THE REGULATORY ANALYSIS PROVIDED WITH THE SECY PAPER SEEMS TO HAVE CONFLICTING STATEMENTS.
ONE QUOTE INDICATES A SB0 COULD BE AN IMPORTANT CONTRIBUTOR TO THE TOTAL RICK FROM NUCLEAR POWER PLANT ACCIDENTS. IT THEN INDICATES THE TOTAL RISK WAS FOUND TO
- BE SMALL, BUT THE RELATIVE IMPORTANCE OF THE SB0 RISK WAS ESTABLISHED.
ANOTHER QUOTE INDICATES IF DURATION TIMES ARE ESTABLISHED, IT CAN SIGNIFICANTLY REDUCE CdRE MELT FREQUENCY.
i ZECH/ED0 !
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QUESTION 1A. IF WE ARE DEALING WITH VERY SMALL RISKS OF CORE DAMAGE TO BEGIN WITH, HOW SHOULD THE COMMISSION INTERPRET THE USE OF TERMS LIKE " RELATIVE IMPORTANCE" AND "SIGNIFICANTLY REDUCE"?
ANSWER.
THE,FIRST QUOTE ABOVE IS TAKEN FROM THE BACKGROUND INFORMATION PROVIDED IN THE REGULATORY ANALYSIS AND REFERS TO ONE OF THE CONCLUSIONS FROM THE " REACTOR SAFETY STUDY" (WASH - 1400, OCTOBER 1975). A MORE COMPLETE ANALYSIS OF RISKS FROM STATION
" BLACK 0UT EVENTS IS PUBLISHED IN DRAFT NUREG-1032, " EVALUATION OF STATION BLAC;;0UT ACCIDENTS AT NUCLEAR POWER PLANTS, TECHNICAL FINDINGS RELATED TO USI A-44," MAY 1985. THE NUREG-1032 ANALYSIS INCLUDES SPECIFIC STATION BLACKOUT ACCIDENT SEQUENCES THAT WERE OMITTED IN WASH-1400 (E.G. TIME-DEPENDENT' SEQUENCES SUCH AS NOT RESTORING AC POWER BEFORE DC POWER SUPPLIES ARE DEPLETED). THE RESULTS IN NUREG-1032 PRESENT THE STAFF'S CURRENT UNDERSTANDING OF IMPORTANT CONTRIBUTORS TO RISK FROM STATION BLACK 0UT EVENTS. THIS ANALYSIS SHOWS THAT THE ESTIMATED FREQUENCY OF CORE DAMAGE ASSOCIATED WITH STATION BLACK 0UT IS, FOR MANY PLANTS, A SIGNIFICANT CONTRIBUTOR TO TOTAL CORE DAMAGE FREQUENCY. FOR SOME PLANTS, THIS FREQUENCY COULD BE AS HIGH AS l
s ZECH/EDO 10/10/85 i
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t QUESTION 1A. (CONTINUED) 10-4 PER YEAR FROM STATION BLACKOUT ALONE, WHICH WOULD MAKE STATION BLACKOUT A MAJOR CONTRIBUTOR TO TOTAL RISK. FOR SUCH PLANTS, IMPLEMENTING THE STAFF'S PROPOSED RESOLUTION WOULD SIGNIFICANTLY REDUCE THE TOTAL RISK BY REDUCING THE ESTIMATED FREQUENCY OF CORE DAMAGE FROM STATION BLACK 0UT BY APPROXIMATELY AN ORDER OF MAGNITUDE (I.E., TO ABOUT 10-5 PER YEAR).
N ZECH/EDO 10/10/85
QUESTION IB. WHY HAS THE STAFF DECIDED TO SUPPORT A GOAL OF ATTAINING 10 MINUS 5 IN THIS STUDY, INSTEAD OF 10 MINUS 4 WHICH IS THE NUMBER THAT HAS BEEN NORMALLY DISCUSSED FOR A SAFETY G0AL?
ANSWER.
AN ESTIMATED FREQUENCY OF CORE MELT OF LESS THAN 10-4 PER REACTOR-YEAR HAS BEEN DISCUSSED AS A PROPOSED PLANT PERFOR-MANCE DESIGN OBJECTIVE IN NUREG-0880, REv. 1, " SAFETY G0ALS FOR NUCLEAR POWER PLANT OPERATION." THIS DESIGN OBJECTIVE ENCOM-PASSES TOTAL CORE MELT FREQUENCY FROM ALL ACCIDENT SEQUENCES.
THE STAFF AND ACRS BELIEVE THAT THE ACCIDENT SEQUENCES ASSO-CIATED WITH STATION BLACKOUT SHOULD NOT BE A MAJOR FRACTION OF THIS TOTAL CORE MELT FREQUENCY. IN FACT, IN A LETTER DATED JULY 17, 1985, FROM ACRS TO CHAIRMAN PALLADINO ON THE SUBJECT "ACRS COMMENTS ON PROPOSED NRC SAFETY GOAL EVALUATION REPORT,"
THE ACRS STATED, "WE SUPPORT THE GENERAL PRINCIPLE THAT NO MORE THAN ABOUT 10 PERCENT OF ANY QUANTITATIVE DESIGN OBJECTIVE SHOULD BE ACCOUNTED FOR BY A SINGLE MAJOR ISSUE OR ACCIDENT." THE STAFF BELIEVES A TARGET OF ESTIMATED CORE MELT FOR STATION BLACK 0UT EVENTS OF 10-5 PER REACTOR-YEAR WOULD BE CONSISTENT WITH THE SAFETY GOAL OBJECTIVES.
ZECH/ED0 10/10/85
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QUESTION IC. DOES THE STAFF, CRGR, ACRS, AND OPE FEEL THAT THE COMMISSION WILL BE ABLE TO DEMONSTRATE THAT THE PROPOSED RULE WILL RESULT IN A SUBSTANTIAL INCREASE IN OVERALL PROTECTION OF THE PUBLIC HEALTH AND SAFETY?
ANSWER.
THE STAFF BELIEVES THAT IMPLEMENTING THE PROPOSED RULE WOULD RESULT IN STATION BLACK 0UT BEING A RELATIVELY SMALL CONTRIBUTOR TO TOTAL CORE DAMAGE FREQUENCY AND WOULD SUBSTANTIALLY INCREASE THE OVERALL PROTECTION OF THE PUBLIC HEALTH AND SAFETY. NUREG-1109,
" REGULATORY ANALYSIS FOR THE RESOLUTION OF USI A-44," DOCUMENTS THE STAFF'S VALUE-!MPACT ANALYSIS THAT INCLUDES THE STAFF'S ESTIMATE OF PUBLIC RISK REDUCTION ASSOCIATED WITH THE PROPOSED RULE.
IN A LETTER TO THE EDO DATED MARCH 12, 1985, THE ACRS STATED, "WE BELIEVE THAT IF FOLLOWED, THEY [I.E., THE NRC STAFF'S PROPOSED RECOMMENDATIONS] WILL REDUCE RISK TO THE PUBLIC AND TO OPERATING PLANTS."
THE DIRECTOR, OPE, STATED IN A LETTER TO THE COMMISSIONERS ON SEPTEMBER 5, 1985, "0VERALL, WE FEEL THAT THE STAFF HAS MADE A ZECH/ED0 10/10/85
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QUESTION IC. (CONTINUED)
REASONABLE ASSESSMENT OF THE POSSIBLE COST OF IMPLEMENTING THE RULE AND ASSESSING THE BENEFITS IN TERMS OF REDUCED RISK TO THE PUBLIC." IN CONCLUSION OPE STATED, " BASED ON OUR REVIEW, WE RECOMMEND THAT THE PROPOSED RULE BE PUBLISHED FOR COMMENT. WE BELIEVE, FIRST, THAT THERE IS ADEQUATE JUSTIFICATION TO SUPPORT RULEMAKING TO REDUCE THE RISK OF SEVERE ACCIDENTS POSED BY STATION BLACK 0UT AND, SECOND, THAT THERE IS SUFFICIENT COORDINATION OF EFFORTS BETWEEN USI A-44 AND USI A-45 AND OTHER GENERIC ISSUES, SUCH THAT A DELAY IN PUBLISHING THE PROPOSED STATION BLACK 0UT RULE IN ORDER TO BETTER INTEGRATE THESE EFFORTS IS NOT JUSTIFIED."
(NOTE: THE FOLLOWING PART OF THE RESPONSE TO THIS QUESTION WAS PROVIDED BY CRGR).
DURING SEVERAL MEETINGS, CRGR REVIEWED THE STAFF'S PROPOSED RESOLUTIONS OF USI A-44 AND THE ESTIMATED RISK REDUCTION
.a-BENEFITS IN THE PUBLIC HEALTH AND SAFETY. AS REFLECTED IN THE MINUTES OF CRGR MEETING NO. 60 (MAY 8, 1984), THE CRGR DID RAISE SOME ISSUES WITH THE STRUCTURE OF, AND IMMEDIATE NEED FOR, THE RULE AND ITS OVERALL BENEFITS.
ZECH/ED0 10/10/85
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QUESTION IC. (CONTINUED)
CRGR AGREES THAT SOME INCREMENTAL REDUCTION IN THE PUBLIC RISK SHOULD ACCURE FROM THE STAFF'S PROPOSED RESOLUTION OF USI A-44, BUT IT IS DIFFICULT TO CONCLUDE THAT THIS SEPARATE INCREMENT WOULD REPRESENT A SUBSTANTIAL INCREASE IN THE OVERALL PROTECTION OF THE PUBIC HEALTH AND SAFETY FOR MANY OF THE
- EXISTING REACTORS WITHOUT CONSIDERING THE OUTCOME OF RELATED ACTIVITIES. THE STAFF'S REGULATORY ANALYSIS DID ON THE OTHER HAND INDICATE THAT THE PROPOSED RULE REQUIREMENTS SHOULD BE COMMENSURATE WITH THIS COST. .
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- 2. THE REGULATORY ANALYSIS AND THE DRAFT REG GUIDE MAKE REFERENCE TO THE ESTABLISHMENT OF A RELIABILITY PROGRAM.
QUESTION 2A, IS THIS A NEW REQUIREMENT, AN OLD REQUIRE-MENT WITH NEW ASPECTS, OR JUST THE RECENTLY REVISED AGENCY METHOD TO ENSURE EMERGENCY DIESEL GENERATOR RELIABILITY VIA THE
, SURVEILLANCE TESTING PROGRAM? IF NEW REQUIRE-MENTS ARE BEING IMPOSED,,WHAT ARE THE BASIS FOR THE REQUIREMENTS?
ANSWER.
THE DRAFT REGULATORY GUIDE ON STATION BLACK 0UT RECOMMENDS THAT EMERGENCY DIESEL GENERATOR (EDG) RELIABILITY BE MAINTAINED ABOVE CERTAIN MINIMUM LEVELS. THE BASIS FOR THIS RECOMMENDATION IS THAT RELIABILITY LEVELS BELOW THESE MINIMUM VALUES WOULD RESULT IN HIGHER ESTIMATED CORE DAMAGE FREQUENCY THAN ASSUMED IN THE STAFF'S ANALYSIS OF STATION BLACK 0UT EVENTS.
THE RELIABILITY PROGRAM IS NOT A NEW REQUIREMENT. IT IS A REVISED METHOD TO ENSURE THAT MINIMUM EDG RELIABILITY LEVELS ARE ZECH/ED0 10/10/85
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QUESTION 2A. (CONTINUED) 1 BEING MAINTAINED. CURRENTLY, REG. GUIDE 1.108, " PERIODIC
. TESTING OF DIESEL GENERATOR UNITS USED AS ONSITE ELECTRICAL POWER SYSTEM AT NUCLEAR POWER PLANTS," ESTABLISHES A RELIABILITY !
GOAL OF 0.99 FOR EDG'S, IF EDG RELIABILITY FALLS BELOW THIS LEVEL, THE GUIDE CALLS FOR MORE FREQUENT EDG TESTING. CURRENTLY, LESS THAN HALF OF THE OPERATING NUCLEAR PLANTS IN THE V.S.
(I.E., THOSE LICENSED SINCE 1977) HAVE STANDARD TECHNICAL SPECIFICATIONS THAT INCLUDE THE DIESEL GENERATOR RELIABILITY G0AL. PLANTS LICENSED BEFORE 1977 DO NOT HAVE ANY SUCH GOAL.
THEESTAFF HAS FOUND THAT A.0.99 RELIABILITY GOAL MAY BE DIFFICULT FOR LICENSEES TO ACHIEVE. THE INDUSTRY AVERAGE DIESEL GENERATOR RELIABILITY IS CLOSE TO 0.98, WITH A RANGE OF FROM SLIGHTLY LESS 1
THAN 0.90 TO 1.0, WHILE SPECIFIC MINIMUM RELIABILITY LEVELS ARE PART OF THE PROPOSED RESOLUTION OF USI A-44, THE DEVELOPMENT OF AN ACCEPTABLE EDG RELIABILITY PROGRAM IS PART OF GENERIC ISSUE B-56. (THIS PROGRAM IS CLOSELY COORDINATED WITH USI A-44.)
SUCH A PROGRAM WOULD PROVIDE ASSURANCE THAT MINIMUM EDG RELIABILITY LEVELS WERE BEING MAINTAINED; AND IF EDG RELIABILITY DROPPED BELOW THESE LEVELS, ACTIONS WOULD BE TAKEN TO IMPROVE THE RELIABILITY. IT SHOULD ALSO BE NOTED THAT THE NUGSB0 PROPOSAL RECOMMENDS THAT INDUSTRY DEVELOP PROGRAMS TO
. IMPROVE ONSITE EMERGENCY AC POWER SYSTEMS RELIABILITY.
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- 3. THERE APPEARS TO BE VARYING OPINIONS AS TO THE COST ASSOCI-ATED WITH THE ANALYSIS AND ANY PROPOSED MODIFICATIONS THAT MAY BE NECESSARY TO COMPLY WITH THE PROPOSED RULE.
THE STAFF CONSULTANT ESTIMATED AN AVERAGE OF $600,000 PER PLANT AND A RECENT NUGSB0 LETTER INDICATES THE NUMBER WOULD ACTUALLY BE IN THE MILLIONS.
QUESTION 3A. WHAT ARE THE RESULTS OF COST BENEFIT AND VALUE IMPACT ANALYSIS WHEN APPLIED OVER THE RANGE (HIGH TO LOW) 0F COSTS AS DETERMINED BY THE STAFF AND BY THE INDUSTRY?
ANSWER.
THE STAFF HAS NOT RECEIVED SPECIFIC COMMENTS FROM NUGSB0 l REGARDING ESTIMATED COSTS FOR MODIFICATIONS TO COMPLY WITH THE PROPOSED RULE. THEREFORE, WE CAN NOT COMMENT ON THE NUGSB0 COST ESTIMATES REFERRED TO ABOVE.
A
SUMMARY
OF THE STAFF'S ESTIMATES OF THE VALUE IMPACT RATIO FOR HIGH, LOW AND BEST ESTIMATE CASES IS PRESENTED IN TABLE 8, ON ZECH/ED0
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QUESTION 3A. (CONTINUED)
PAGE 25 0F NUREG 1109. FOR THE HIGH AND LOW ESTIMATES, THE RATIOS ARE 1,300 AND 3,600 PERSON-REM AVERTED PER MILLION DOLLARS; THE BEST ESTIMATE IS 2,100 PERSON-REM AVERTED PER MILLION DOLLARS.
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THE RANGE OF VALUES FOR THIS RATIO IS BASED ON THE FOLLOWING SPECIFIC COST ESTIMATES PER PLANT (SEE TABLE 6 0F NUREG 1109):
l ASSESS ABILITY TO COPE WITH STATI.ON BLACK 0UT - $100 TO 200 THOUSAND.
DEVELOP PROCEDURES AND TRAINING - $50 TO 100 THOUSAND.
IMPROVE DIESEL GENERATOR RELIABILITY (IF NEEDED) - $250 ,
THOUSAND TO $2.8 MILLION. '
INCREASE CAPABILITY TO COPE WITH A STATION BLACK 0UT (IF NEEDED) - $500 THOUSAND TO $2 MILLION.
THERE ARE MANY PLANT-SPECIFIC DIFFERENCES THAT COULD RESULT-IN :
t SIGNIFICANT DIFFERENCES IN COSTS FROM PLANT TO PLANT TO COMPLY WITH THE PROPOSED RULE (E.G., DIFFERENCES IN DESIGN AND NEED TO MAKE MODIFICATIONS), BUT THE ABOVE COSTS ARE EXPECTED TO BE REASONABLE ESTIMATES FOR MOST PLANTS. AN INDEPENDENT REVIEW OF j THE STAFF'S ESTIMATED COSTS WAS PERFORMED BY THE COST ANALYSIS c GROUP IN THE DIVISION OF BUDGET ANALYSIS. IN A MEMO DATED i
i r
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QUESTION 3A. (CONTINUED)
APRIL 12, 1985, TO THE DIRECTOR, NRR, THE DIRECTOR, RM/B, STATED THAT "THE COST ANALYSIS GROUP'S REVIEW INDICATED THAT THE (STAFF'S) COST ESTIMATES ARE REASONABLE AND TEND TO BE CONSERVATIVELY HIGH IN MEASURING THE LIKELY COST IMPACT (FOR USI A-44)."
INDUSTRY COMMENTS ON SIGNIFICANTLY HIGHER COSTS COULD BE BASED ON THEIR ASSUMPTIONS, FOR EXAMPLE, REGARDING THE SCOPE AND DEPTH OF THE ANALYSIS TO ASSESS THE ABILITY TO COPE WITH STATION BLACK 0UT. THE STAFF'S GUIDANCE ON THIS ANALYSIS, WHICH IS INCLUDED IN THE DRAFT REGULATORY GUIDE AND THE DRAFT ANS STANDARD, SPECIFIES THAT THIS SHOULD BE A REALISTIC ANALYSIS.
IT IS HIGHLY UNLIKELY THAT DETAILED THERMAL-HYDRAULIC ANALYSES, SUCH AS REQUIRED FOR APPENDIX K TYPE LOCA CALCULATIONS, WOULD BE REQUIRED FOR A STATION BLACK 0UT COPING STUDY.
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ZECH/EDO 10/10/85
t QUESTION 1. STAFF SUGGESTS THAT VALUE/ IMPACT IS FAVORABLE TO GOING AHEAD WITH THE STATION BLACK 0UT RULE. AT
$1,000/ MAN-REM, THE BENEFIT / COST RATIO IS 2. IS THIS VIEWED BY THE STAFF AS SUFFICIENTLY FAVORABLE TO ALLOW THE STATEMENTS ON PAGE 6 0F THE SEPTEMBER 11, 1985, VIEWGRAPHS? WHAT ARE THE UNCERTAINTIES ASSOCIATED WITH THIS VALUE?
ANSWER.
ALTHOUGH THE STAFF'S BEST ESTIMATE OF THE OVERALL VALUE-IMPACT RATIO FOR THE PROPOSED RESOLUTION OF USI A-44 IS FAVORABLE (I.E., APPROXIMATELY $500 PER PERSON-REM AVERTED), IT IS IMPORTANT TO NOTE THAT THIS WAS NOT THE ONLY BASIS FOR THE STAFF'S RECOMMENDATIONS. OTHER FACTORS WERE CONSIDERED, AND
.THESE CONSIDERATIONS SUPPORT THE STAFF'S CONCLUSION THAT THE ADDITIONAL DEFENSE-IN-DEPTH PROVIDED BY THE ABILITY OF A PLANT TO COPE WITH A STATION BLACK 0UT WOULD REDUCE THE RISKS ASSOCIATED WITH STATION BLACKOUT. THESE CONSIDERATIONS INCLUDE (1) THE POTENTIALLY SEVERE CONSEQUENCES OF STATION BLACK 0UT EVENTS BECAUSE MITIGATING FEATURES, SUCH AS CONTAINMENT HEAT REMOVAL SYSTEMS, ARE INOPERABLE WITHOUT AC POWER AVAILABLE, (2) UNCERTAINTIES IN THE ANALYSES RELATED TO USING POINT ESTIMATES
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BERNTHAL/EDO 10/10/85
QUESTION 1. (CONTINUED)
FOR CORE DAMAGE FREQUENCIES, AND (3) POTENTIAL COMMON CAUSE FAILURES OF AC POWER SYSTEMS. EACH OF THESE ITEMS IS DISCUSSED MORE THOROUGHLY IN NUREG-1109 (ENCLOSURE 2 0F SECY-85-163).
THE HIGH AND LOW VALUE-IMPACT RATIO ESTIMATES FROM TABLE 8 IN NUREG-1109 ARE 1,300 AND 3,600 PERSON-REM AVERTED PER MILLION DOLLARS RESPECTIVELY. SINCE "BEST ESTIMATES" WERE USED IN THIS EVALUATION, THERE IS ABOUT AN EQUAL PROBABILITY THAT THE VALUE-IMPACT RATIO WOULD BE EITHER HIGHER OR LOWER THAN THE BEST
' ESTIMATE OF 2,100 PERSON-REM AVERTED PER MILLION DOLLARS.
BERNTHAL/EDO 10/10/85
CUESTION 2. SINCE $1,000/ MAN-REM IS A 3URROGATE FOR MANY OFFSITE CONSEQUENCES, HOW WOULD THE BENEFIT / COST RATIO CHANGE IF OFFSITE PROPERTY DAMAGE WAS EXCLUDED, AND AN APPROPRIATELY ADJUSTED $/ MAN-REM RELATION USED? CAN STAFF ESTIMATE THE SIMILAR BENEFIT / COST RATIO IF AVERTED ON-SITE DAMAGE IS TAKEN INTO ACCOUNT?
ANSWER.
THE STAFF'S VALUE-IMPACT ANALYSIS IS BASED ON BEST ESTIMATES
.FOR 67 REACTORS OF THE TOTAL PUBLIC RISK REDUCTION OVER THE LIFE i OF THESE PLANTS (80,000 PERSON-REM) AND THE TOTAL COST FOR THE ,
SAME NUMBER OF PLANTS TO COMPLY WITH THE PROPOSED RULE ($40 MILLION). THE VALUE-IMPACT RATIO, WHICH IS CALCULATED DIRECTLY BY DIVIDING THESE TWO NUMBERS, RESULTS IN ABOUT 2,000 PERSON-REM AVERTED PER MILLION DOLLARS. THE STAFF PRACTICE IS TO CLASSIFY AVERTED OFFSITE DAMAGE COSTS AS A BENEFIT (OR VALUE) BUT IN MOST CASES, INCLUDING THE USI A-44 ANALYSIS, THEY ARE NOT EXPLICITLY INCLUDED IN THE VALUE-IMPACT RATIO. THE RATIO IS USUALLY COMPARED TO THE PROPOSED BENEFIT-COST GUIDELINES IN NUREG-0880 0F $1,000 PER PERSON-REM AVERTED (I.E., 1,000 PERSON-REM AVERTED '
PER MILLION DOLLARS). THIS PROPOSED BENEFIT-COST GUIDELINE
($1,000 PER PERSON-REM) IMPLICITLY INCLUDES POTENTIAL OFFSITE BERNTHAL/ED0 ,
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QUESTION 2. (CONTINUED)
PROPERTY DAMAGE. IF 0FFSITE PROPERTY DAMAGE WERE EXCLUDED FROM THE GUIDELINES, THE " YARDSTICK" WHICH IS USED TO COMPARE TO ESTIMATES OF BENEFIT-COST RATIOS FOR PROPOSED BACKFITS WOULD BE l REDUCED SOMEWHAT (I.E., WOULD BE LESS THAN $1000/ PERSON-REM).
l POSTULATED RELEASES ASSOCIATED WITH STATION BLACK 0UT ACCIDENTS ARE POTENTIALLY OF HIGH SEVERITY. FOR SUCH RELEASES, THE l
OFFSITE PROPERTY DAMAGE WOULD BE SMALL COMPARED TO THE
- $1000/ PERSON-REM GUIDELINE WHICH REPRESENTS BOTH HEALTH-EFFECTS RISK AND OFFSITE PROPERTY DAMAGE FOR RADI0 ACTIVE RELEASES.
THEREFORE, THE $1,000/ PERSON-REM FIGURE USED AS A " YARDSTICK" N :
WOULD NOT CHANGE SUBSTANTIALLY EVEN IF 0FFSITE PROPERTY DAMAGE WERE EXCLUDED.
THE STAFF HAS INCLUDED ESTIMATES OF THE BENEFIT-COST RATIO IF AVERTED ONSITE DAMAGE IS TAKEN INTO ACCOUNT. THE OVERALL VALUE-IMPACT RATIO WOULD IMPROVE BY ABOUT A FACTOR OF FOUR TO 8,000 PERSON-REM AVERTED PER MILLION DOLLARS (SEE PAGES 23 AND 24 0F NUREG-1109).
BERNTHAL/EDO 10/10/85
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QUESTION 3. WHAT DESIGN CHARACTERISTICS ENABLE FRENCH PLANTS TO HAVE A 20-HOUR STATION BLACKOUT CAPABILITY?
ANSWER.
THE NEW FRENCH 1300 MWE NUCLEAR POWER PLANTS ARE DESIGNED WITH A GOAL OF COPING WITH A STATION BLOCK 0UT FOR AT LEAST 20 HOURS. IN PRACTICE, THE DESIGN FEATURES THAT PROVIDE THIS CAPABILITY (LISTED BELOW) PERMIT THE PLANT TO WITHSTAND A STATION BLOCK 00T FOR THREE DAYS.
O A STEAM-DRIVEN GENERATOR PROVIDES POWER FOR A SMALL POSITIVE DISPLACEMENT PUMP THAT SUPPLIES COOLING FOR REACTOR COOLANT PUMP (RCP) SEALS AND ALSO PROVIDES POWER FOR INSTRUMENTATION AND CONTROLS AND CONTROL ROOM LIGHTING NECESSARY TO WITHSTAND A STATION BLACKOUT. THIS DESIGN FEATURE, WHICH IS ALSO BEING BACKFIT ON ALL OPERATING 900 MWE NUCLEAR PLANTS IN FRANCE, ADDRESSES TWO FACTORS THAT IMPACT THE ABILITY TO COPE WITH A STATION BLACKOUT - RCP SEAL COOLING WITH AC POWER UNAVAILABLE AND BATTERY DEPLETION.
O TWO TURBINE-DRIVEN AUXILIARY FEEDWATER (AFW) PUMPS ARE INCLUDED IN THE 1300 MWE FRENCH DESIGN IN ADDITION TO TWO MOTOR-DRIVEN AFW PUMPS. MOST U.S. PWRS HAVE ONE BERNTHAL/ED0 10/10/85
r QUESTION 3. (CONTINUED)
TURBINE-DRIVEN AFW PUMP IN ADDITION TO TWO MOTOR-DRIVEN PUMPS. THEREFORE, THE FRENCH DESIGN PROVIDES ADDITIONAL
! REDUNDANCY IN THE AC-INDEPENDENT TRAINS OF THE AFW SYSTEM l 0 GRAVITY FEED BACK-UP WATER SUPPLY FROM THE DEMINERALIZED I WATER STORAGE TANK TO THE CONDENSATE STORAGE TANK PROVIDES ADDITIONAL WATER FOR DECAY HEAT REMOVAL VIA THE AFW SYSTEM FOR LONG-DURATION STATION BLACKOUT EVENTS (I.E., UP TO THREE DAYS).
THIS THREE-DAY STATION BLOCK 0VT CAPABILITY WOULD PERMIT l
l SUFFICIENT TIME TO CONNECT A MOBILE GAS TURBINE GENERATOR TO PROVIDE POWER IF AC POWER COULD NOT BE RESTORED FROM OTHER PERFERRED SOURCES. A MOBILE GAS TURBINE GENERATOR IS LOCATED AT, OR IN THE REGION OF, EVERY NUCLEAR POWER PLANT SITE IN FRANCE.
es.
BERNTHAL/EDO 10/10/85
t QUESTION 4. WHAT UNIQUE COPING FEATURES ARE BUILT INTO THE SIZEWELL PWR?
ANSWER.
IN ADDITION TO EQMR DIESEL GENERATOR 0 TO SUPPLY EMERGENCY ONSITE AC POWER (U.S. PLANTS TYPICALLY H,iVE TWO DIESEL
- GENERATORS PER REACTOR), THE SIZEWELL DESIGN INCLUDES TWO STEAM-DRIVEN POSITIVE DISPLACEMENT CHARGING PUMPS TO PROVIDE SEAL INJECTION FOR RCP SEAL COOLING IN THE EVENT OF A STATION BLACKOUT. 1 O
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QUESTION 5. WHAT ARE THE RESULTS OF THE FRENCH TESTS OR ANY OTHER TESTS EXPLORING THE ISSUE OF REACTOR COOLANT PUMP SEAL INTEGRITY AND WHAT ARE THE IMPLICATIONS FOR THIS ISSUE?
ANSWER.
THERE HAVE BEEN SEVERAL TESTS IN THE U.S. AND FRANCE OF REACTOR COOLANT PUMP (RCP) SEAL INTEGRITY DURING A STATION BLACK 0UT.
THE MOST RECENT TEST WAS PERFORMED IN MAY 1985 IN FRANCE. WE ONLY HAVE PRELIMINARY RESULTS FROM THIS TEST OF THE FRENCH 7" HYDROSTATIC REACTOR COOLANT PUMP SEAL. UNTIL THE COMPLETE DETAILS OF THIS TEST, AS WELL AS THE SEAL DESIGN, ARE MADE AVAILABLE, WE CANNOT DETERMINE THE SIGNIFICANCE OF THE TESTS WITH RESPECT TO STATION BLACKOUT IN U.S. PLANTS. THERE ARE A NUMBER OF DIFFERENCES BETWEEN THE WESTINGHOUSE 8" HYDROSTATIC SEAL IN CURRENT USE IN U.S. PLANTS AND THE OLDER DESIGN 7" FRENCH SEAL. THESE DIFFERENCES APPARENTLY INCLUDE MATERIAL DIFFERENCES IN THE COMPOUNDING CF THE SECONDARY SEALS. THE FRENCH RCP SEAL DID SURVIVE THE SIMULATED STATION BLAC'K0VT TEST. THE LATEST FRENCH TEST DIFFERS FROM RESULTS FROM EARLIER FRENCH RCP SEAL TESTS OF SHORTER DURATION THAT INDICATED TO THE FRENCH THAT THE RCP SEALS WOULD FAIL DURING A STATION BLACKOUT.
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l QUESTION 5. (CONTINUED) l OTHER RCP SEAL OR SEAL COMPONENT TESTS WHICH ARE RELATED TO STATION BLACKOUT ARE THE BYRON-JACKSON (BJ) 50-HOUR LOSS-OF-SEAL-COOLING TEST ON A SEAL CARTRIDGE ASSEMBLY FROM THE '
ST. LUCIE PLANT AND THE SAN ONOFRE 30-MINUTE LOSS-OF-COOLING TEST PERFORMED ON THE COMPLETE BJ PUMPS WHILE RUNNING. NEITHER 0F THESE TESTS RESULTED IN SEAL FAILURES. THE BJ PUMP USES A HYDRODYNAMIC TYPE OF SEAL.
RE3ULTS OF THE ATOMIC ENERGY OF CANADA LIMITED (AECL) STUDY FOR ,
NRC " REACTOR COOLANT PUMP SHAFT LEAK BEHAVIOR DURING STATION BLACKOUT" (NUREG/CR-4077) INDICATE A NUMBER OF POTENTIAL RCP SEAL PROBLEMS ASSOCIATED WITH STATION BLACKOUT. THE MOST SERIOUS CONCERNS UNDER STATION BLACKOUT CONDITIONS ARE THE l POSSIBILITY OF THE SEAL FACES " POPPING OPEN" OR FAILURE OF THE ELASTOMER SECONDARY 0-RING SEALS. " POPPING OPEN" IS POSSIBLE FOR CURRENT SEAL DESIGNS IF SUFFICIENT FLASHING OCCURS BETWEEN SEAL FACES. IF THIS OCCURS, LEAK RATES OF GREATER THAN 100 GALLONS PER MINUTE PER PUMP ARE LIKELY.
AS A RESULT OF THE AECL TEST PROGRAM, THE WESTINGHOUSE OWNERS f GROUP HAS DECIDED TO CHANGE THE 0-RING MATERIAL PRESENTLY USED IN WESTINGHOUSE RCP SEALS TO A MORE TEMPERATURE-RESISTANT ,
! BERNTHAL/EDO 10/10/85 !
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l QUESTION 5. (CONTINUED)
MATERIAL TO REDUCE THE LIKELIHOOD OF SEAL FAILURE DURING A STATION BLACKOUT.
THE STAFF IS CONTINUING ITS STUDY OF THE RCP STATION BLACK 0UT SEAL FAILURE PROBLEM AS PART OF GENERIC ISSUE 23, REACTOR COOLANT PUMP SEAL FAILURES. ADDITIONAL TECHNICAL STUDIES ON RCP SEAL BEHAVIOR, AS WELL AS THE RESULTS OF THE RECENT FRENCH RCP CEAL TEST WILL BE REVIEWED BY THE STAFF BEFORE ANY ADDITIONAL CONCLUSIONS CAN BE REACHED REGARDING RCP SEAL
.. FAILURES DURING STATION BLACKOUT. THESE RESULTS AND ,
CONCLUSIONS WILL PROVIDE INFORMATION TO THE STAFF FOR THEIR REVIEW OF LICENSEES' RESPONSES TO THE PROPOSED STATION BLACKOUT RULE (1.E., ASSESSMENTS OF PLANT COPING CAPABILITY IN THE EVENT OF A STATION BLACKOUT).
BERNTHAL/EDO 10/10/85
THE FOLLOWING QUESTIONS REFERENCE ENCLOSURE 1 TO THE SECY PAPER (NOTICE OF PROPOSED RULEMAKING):
QUESTION 6. PAGE 2, 4TH LINE FROM BOTTOM: WHAT WERE THE "0RIGINALLY ANTICIPATED" RELIABILITIES?
ANSWER.
WHEN GENERAL DESIGN CRITERION (GDC) 17, " ELECTRIC POWER SYSTEMS," WAS WRITTEN, THE REQUIREMENTS FOR INDEPENDENCE AND REDUNDANCY OF BOTH THE OFFSITE AND ONSITE AC ELECTRIC POWER SUPPLIES WERE FELT TO BE SUFFICIENT TO ASSURE THAT CORE COOLING ,
AND CONTAINMENT INTEGRITY COULD BE MAINTAINED IN THE EVENT OF POSTULATED ACCIDENTS. NO SPECIFIC SYSTEM RELIABILITIES WERE ASSUMED IN DEVELOPING GDC 17. THE STAFF FELT, ON A DETERMINISTIC BASIS, THAT PROVIDING A REDUNDANT EMERGENCY DIESEL GENERATOR WOULD BE AN ACCEPTABLE DESIGN FROM A PUBLIC HEALTH AND SAFETY STANDPOINT. RESULTS OF PRAS WERE LIMITED AT i
THAT TIME, ESPECIALLY COMPARED TO THE STAFF'S PRESENT l . UNDERSTANDING OF RISK FACTORS ASSOCIATED WITH STATION BLACKOUT EVENTS. RESULTS OF PRAS HAVE SHOWN THAT EVEN THOUGH PLANTS
. MEET CURRENT NRC REGULATIONS FOR THE DESIGN OF OFFSITE AND -
1 l _,
~ 0NSITE AC POWER SYSTEMS, STATION BLACKOUT CAN STILL BE A l
SIGNIFICANT CONTRIBUTOR TO OVERALL PLANT RISK. THE BERNTHAL/ED0 10/10/85
t QUESTION 6. (CONTINUED) ;
RELIABILITIES OF THE AC POWER SYSTEMS HAVE BEEN STUDIED EXTENSIVELY,-AND RESULTS OF THESE STUDIES HAVE BEEN FACTORED INTO THE PRAS.
BECAUSE OF CONCERN ABOUT RELIABILITY OF ONSITE AC POWER SYSTEMS, REVISION 1 0F REGULATORY GUIDE 1.108 WAS ISSUED IN 1977. THIS GUIDE ESTABLISHED A RELIABILITY GOAL FOR EMERGENCY DIESEL GENERATORS OF 0.99. AS STATED IN RESPONSE TO QUESTION 2.A FROM COMMISSIONER ZECH, LESS THAN HALF 0F THE OPERATING
. PLANTS IN THE U.S. HAVE STANDARD TECHNICAL SPECIFICATIONS THAT INCLUDE THE REGULATORY GUIDE GOAL OF 0.99. THE STAFF BELIEVES
.THAT, IN LIGHT OF EXPERIENCE, THIS MAY NOT,BE A REALISTIC GOAL.
THE CURRENT APPROACH IS TO HAVE EACH LICENSEE DEVELOP AN ACCEPTABLE EDG RELIABILITY PROGRAM (AS THE RESOLUTION OF GENERIC ISSUE B-56, " DIESEL GENERATOR REL,IABIL.ITY") AND SELECT A DIESEL 3
GENERATOR RELIABILITY THAT THE~ LICENSEE WOULD COMMIT TO MAINTAIN
.m.IN MEETING THE COPING REQUIREMENTS OF THE STATION BLACK 0UT RULE (0.95 OR 0.97 ARE THE SUGG7.STED RELIABILITY VALUES IN THE PROPOSED REGULATORY GUIDE WHICH SUPPORTS THE RULE).
BERNTHAL/EDO 10/10/85
QUESTION 7. PAGE 10, 4TH LINE FROM BOTTOM: WHAT PLANTS ARE OUTSIDE THE SCOPE OF THIS RULE?
l ANSWER.
THE PROPOSED RULE WAS LIMITED IN SCOPE S0 THAT THE RULE WOULD NOT APPLY TO A PLANT FOR WHICH STATION BLACKOUT ALREADY HAS BEEN
- LITIGATED DURING THE PROCEEDINGS TO LICENSE THE PLANT AND A SPECIFIC STATION BLACKOUT COPING CAPABILITY HAS BEEN CONSIDERED AND SPECIFIED AS A BASIS FOR LICENSING THE PLANT. AS FAR AS THE STAFF IS AWARE, THIS EXEMPTION WOULD APPLY ONLY TO ONE PLANT, ST, LUCIE, HOWEVER, THE LANGUAGE IN THE RULE WAS WRITTEN GENERALLY TO ACCOUNT FOR THE POSSIBILITY THAT SIMILAR ACTIONS COULD TAKE PLACE'AT OTHER PLANTS PENDING PROMULGATION OF THE FINAL RULE, 4
BERNTHAL/ED0 10/10/85
QUESTION 8. PAGE 11, LINES 7 AND 8: WHAT IS THE STAFF DEFINITION OF ADEQUATE " CORE COOLING" THAT NUST BE MAINTAINED? WHAT IS THE STAFF DEFINITION OF
" CONTAINMENT INTEGRITY" THAT WILL HAVE TO BE MAINTAINED?
ANSWER.
THE ABILITY TO ADEQUATELY COOL THE CORE DURING A STATION BLACK 0UT MEANS THAT REACTOR COOLANT INVENTORY (BOTH FLOW AND WATER LEVEL) SHALL BE SUFFICIENT TO REMOVE DECAY HEAT FROM THE o
REACTOR CORE TO A HEAT SINK (E.G., STEAM GENERATORS FOR PWRS AND SUPPRESSION POOL OR ISOLATION CONDENSER FOR BWRS) FOR THE DURATION OF THE STATION BLACK 0UT AND DURING THE PERIOD OF TIME AFTER AC POWER IS RESTORED UNTIL NORMAL OR SAFE SHUTDOWN COOLING SYSTEMS ARE RESTORED.
l MAINTAINING CONTAINMENT INTEGRITY MEANS A CONTAINMENT BOUNDARY l SHALL BE AVAILABLE AND THE CONTAINMENT CAN BE ISOLATED, IF NEEDED, IN ORDER TO PREVENT OR LIMIT THE ESCAPE OF
- RADI0 ACTIVITY DURING A STATION BLACK 0UT.
BERNTHAL/EDO 10/10/85
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QUESTION 1.. WHAT COSTS AND WHAT BENEFITS WERE INCLUDED IN THE COST-BENEFIT ANALYSIS ASSOCIATED WITH THIS PROPOSED RULE? FOR KNOWN COSTS AND KNOWN BENEFITS NOT INCLUDED, WHAT WAS THE RATIONALE FOR EXCLUDING THEM? PLEASE INDICATE WHETHER THE MAGNITUDE OF EACH EXCLUDED FACTOR IS HIGHER OR LOWER THAN THOSE FACTORS THAT WERE INCLUDED.
ANSWER.
THE COSTS FOR INDUSTRY TO COMPLY WITH THE PROPOSED RULE INCLUDE THE COSTS REQUIRED TO (1) ASSESS THE PLANT CAPABILITY TO COPE ,
WITH STATION BLACKOUT, (2) DEVELOP PROCEDURES FOR HANDLING.
STATION BLACK 0UT AND PROVIDING TRAINING'IN THOSE PROCEDURES, (3) IMPROVE EMERGENCY DIESEL GENERATOR (EDG) RELIABILITY THROUGH A RELIABILITY INVESTIGATION AND ANY NECESSARY HARDWARE CHANGES TO IMPROVE RELIABILITY AND (4) INCREASE CAPABILITY TO COPE WITH
. STATION BLACK 0UT BY MAKING THE NECESSARY HARDWARE CHANGES TO STATION BATTERIES, CONDENSATE STORAGE, AND/OR INSTRUMENT AIR.
THE INDUSTRY COSTS FOR OPERATION AND MAINTENANCE OF ANY ADDITIONAL EQUIPMENT WERE ALSO INCLUDED. THE COSTS FOR NRC REVIEW 0F THE RULE IMPLEMENTATION WERE INCLUDED.
4 ASSELSTINE/EDO 10/10/85
r QUESTION 1. (CONTINUED)
THE BENEFITS CONSIDERED WERE THE REDUCTION IN RISK TO THE PUBLIC AS WELL AS REDUCED OCCUPATIONAL EXPOSURE FOR POST ACCIDENT CLEANUP AND REPAIR WHICH WOULD RESULT FROM THE ESTIMATED REDUCED FREQUENCY OF STATION BLACK 0UT ACCIDENTS IF THE PROPOSED RULE WERE IMPLEMENTED (SEE NUREG-1109, FOR COMMENT, SECTION I4)
IN A SUPPLEMENTARY CONSIDERATION, THE STAFF ALSO INCLUDED THE BENEFIT FROM AVERTED ONSITE PROPERTY DAMAGE TO ASSESS ITS EFFECT ON THE COST-BENEFIT ANALYSIS. IF THIS BENEFIT WERE INCLUDED, THE OVERALL VALUE-IMPACT RATIO WOULD BE ABOUT 8,000 PERSON-REM ,
AVERTED PER MILLION DOLLARS (COMPARED TO ABOUT 2000 PERSON-REM AVERTED PER MILLION DOLLARS IF ONSITE PROPERTY DAMAGE WERE NOT INCLUDED).
THE STAFF DID NOT EXPLICITLY ESTIMATE THE MAGNITUDE OF OTHER BENEFITS OR COSTS BECAUSE WE BELIEVE THEIR EFFECT ON THE VALUE/ IMPACT RATIO WOULD BE SMALL. EXAMPLES OF SUCH ADDITIONAL ITEMS THAT COULD BE CONSIDERED ARE THE BENEFIT THAT WOULD ACCRUE FROM IMPROVED AVAILABILITY OF THE PLANT (FEWER SHUTDOWNS DUE TO EDG UNAVAILABILITY) AND THE BENEFIT THAT WOULD RESULT FROM THE AVERTED COST OF 0FFSITE INTERDICTION AND DECONTAMINATION FOLLOWING A STATION BLACK 0UT ACCIDENT.
ASSELSTINE/ED0 10/10/85
QUESTION 2. WHAT STATION BLACK 0UT PROBABILITY DOES THE CRGR BELIEVE SUPPORTS A ZER0-HOUR COPING CAPABILITY?
WHAT WOULD CRGR REQUIRE TO ENSURE THAT THAT PROBABILITY IS MAINTAINED? WHAT UNCERTAINTIES IN PROBABILISTIC ANALYSES DID CRGR CONSIDER, WHAT DOES CRGR BELIEVE THEIR RELATIVE IMPORTANCE TO BE, AND HOW WOULD CRGR TREAT THEM TO ENSURE THEY ARE NOT IMPORTANT CONTRIBUTORS TO STATION BLACKOUT RISKS IF ITS RECOMMENDATION TO HAVE A ZER0-HOUR DURATION CATEGORY WERE ADOPTED?
ANSWER (NOTE: THE RESPONSE TO THIS QUESTION WAS PROVIDED BY CRGR).
CRGR, AS PART OF ITS DELIBERATIONS ON THE PROPOSED STATION BLACKOUT RULE (USI A-44) PRESENTED FOR ITS REVIEW (IN MEETINGS NOS. 59, 60 AND 61), INQUIRED OF THE STAFF WHETHER A "ZERO-HOUR" COPING CAPABILITY COULD BE FOUND ACCEPTABLE. IN ESSENCE, CRGR WAS ASKING THE STAFF THIS SAME QUESTION: I.E., IF OR WHETHER THERE EXISTED ANY COMPLEMENT AND CONFIGURATION OF AC POWER SUPPLIES OF SUFFICIENT REDUNDANCY AND/0R RELIABILITY THAT THE STAFF COULD FIND ACCEPTABLE WITHOUT A LICENSEE HAVING TO JUSTIFY AN EXTENDED COPING CAPABILITY OF 4, 8, OR 16-HOUR DURATION. THE ASSELSTINE/ED0 10/10/85
t QUESTION 2. (CONTINUED)
STAFF ESTABLISHED AN AIMING POINT VALUE OF 10-5/ REACTOR-YEAR AS AN ACCEPTABLE FREQUENCY LEVEL FOR A CORE DAMAGE / CORE MELT ACCIDENT THAT COULD RESULT FROM SEQUENCES INITIATED BY A STATION BLACK 0UT (LOSS OF l
ALLAC). -THE ACRS HAD ALSO RECOMMENDED USE OF SUCH AN AIMING POINT-(ALBEIT LOWER) FOR THE USI A-44 RESOLUTION. THIS PROBABILISTICALLY-BASED GOAL WAS QUITE COMPARABLE TO THAT PREVIOUSLY USED BY-THE STAFF IN OTHER USI RESOLUTIONS (SUCH AS ATWS). CRGR TOOK NO ISSUE WITH THIS PROPOSAL, NOR DID IT SUGGEST ANY ALTERNATIVE PROBABILISTIC GOALS, UNCERTAINTY ANALYSES OR DIFFERENT FORMULATIONS FOR COMMON-MODE CONTRIBUTIONS. RATHER, ,
CRGR DID RECOGNIZE THAT SOME LICENSEES COULD PROVIDE, OR MAY-ACTUALLY HAVE IN PLACE, ALTERNATIVE WAYS THAT WOULD SIGNIFICANTLY ENHANCE THE OVERALL AC POWER RELIABILITY AND COULD REDUCE THE CHANCE OF COMMON-CAUSED FAILURES DISABLING ALL OF THE AC SUPPLIES
'(SUCH AS ADDITIONAL DIESEL OR GAS TURBINE DRIVEN GENERATORS,
" BLACK-START" CAPABILITIES, OR PERHAPS CROSS-CONNECT OPTIONS AT TWO-UNIT SITES THAT COULD SERVE AS A ONE-OF-FOUR EMERGENCY in-DIESEL GENERATOR CONFIGURATION RATHER THAN ONE-0F-TWO). THESE ALTERNATIVE WAYS'0F ENHANCING THE OVERALL AC POWER RELIABILITY MAY NOT HAVE BEEN PREVIOUSLY RECOGNIZED (NOR CREDITED) BY THE STAFF IN ITS REVIEW 0F THE AC POWER SYSTEMS AVAILABLE AND ITS PROPOSED RESOLUTION FOR THE USI A-44 ISSUE.
ASSELSTINE/EDO 10/10/85
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QUESTION 2. (CONTINUED)
IN ESPOUSING THIS OPTION FOR A "ZER0-HOUR" COPING CAPABILITY, CRGR NOTED ITS CONCERN THAT THE PROPOSED RULE STRUCTURE WAS INFLEXIBLE AND GAVE CONSIDERABLE EMPHASIS TO THE MITIGATION, RATHER THAN PREVENTION, OF THE SAFETY PROBLEM AT ISSUE. THE RULE APPEARED TO FORECLOSE ANY CREDIT FOR OR DISCOURAGE INCENTIVES
- BY LICENSEES TO TAKE ADDITIONAL PREVENTION STEPS THAT MIGHT BENEFIT THE OVERALL RELIABILITY OF AC POWER. THIS LOGIC SEEMED SOMEWHAT INCONSISTENT WITH THE USUAL PREFERENCE BY NRC TO EMPHASIZE A PREVENTIVE SAFETY PHILOSOPHY IN ADDRESSING A SAFETY ISSUE LIKE USI A-44. IF THE RULE STRUCTURE WOULD PERMIT THE STAFF, TO ACCEPT ARGUMENTS ON THE "ZERO-HOUR" COPING CAPABILITY, THEN CRGR VIEWED IT AS REASONABLE TO EXPECT THAT COMMON CAUSE FAILURE CONCE'RNS MIGHT BE FURTHER REDUCED BY HAVING THE LICENSEE EXPLORE ALTERNATIVE AC POWER CONFIGURATIONS, REDUNDANCIES, DIVERSITIES AND RESTORATION OPTIONS. IT IS ALSO NOTED THAT APPLICATION OF THE STAFF'S PRA TECHNIQUES BY NUGSB0 INDICATES THAT FOR THE MORE VULNERABLE PLANTS THE~ EXTENSION OF COPING CAPABILITY FROM ABOUT A 2-HOUR TO A 4-HOUR DURATION WOULD (IF SUCCESSFUL) WOULD ACHIEVE PERHAPS A FACTOR OF 2.5 REDUCTION IN PROBABILITY OF THOSE CORE MELT SEQUENCES INITIATED BY A STATION BLACKOUT. A LESSER REDUCTION FACTOR SHOULD BE EXPECTED FOR THE OVERALL CORE MELT FREQUENCY FOR MOST OF THE PLANTS. FURTHER, IT IS NOT ASSELSTINE/ED0 10/10/85
r QUESTION 2. (CONTINUED)
UNREASONABLE TO NOTE THAT THE NEW SOURCE TERM WORK ALREADY HAS INDICATED AN EQUIVALENT FACTOR OF REDUCTION IN PUBLIC RISK RELATIVE TO THAT PREDICTED BY THE PROPOSED STATION BLACK 0UT RULE. THIS RELATIVELY SMALL INCREMENTAL REDUCTION IN THE FREQUENCY OF THE BLACKOUT INITIATED CORE MELT SEQUENCES AND IN THE PUBLIC RISK FROM THESE SEQUENCES WOULD ALSO APPEAR ACHIEVABLE FROM ENHANCING THE " FRONT-END" RELIABILITY OF THE AC POWER SOURCES.
IN SUM, CRGR DID NOT SET FORTH ANY ALTERNATIVE PROBABILISTIC GOALS, ALTERNATIVE DATA ASSESSMENTS OR ITS OWN ANALYSIS OF PRA ,
UNCERTAINTIES. CRGR GENERALLY ACCEPTED THE STAFF'S PRA ASSESSMENTS AS BEING REASONABLE. IT ALSO ACCEPTED THE STAFF'S VIEW THAT MOST PLANTS WERE EXPECTED TO ALREADY HAVE ABOUT A 2-HOUR COPING CAPABILITY GIVEN THE STATION BLACK 0UT EVENT. IT SHOULD BE NOTED THAT CURRENT NRC REQUIREMENTS SPECIFY THE AVAILABILITY OF A DIVERSE (INDEPENDENT OF BULK AC POWER) MEANS OF DECAY HEAT REMOVAL AND THE CRGR WAS NOT CHALLENGING THIS REQUIREMENT FOR DIVERSITY IN ITS ESPOUSAL OF THE "ZERO HOUR" COPING CAPABILITY.
CRGR ALSO QUESTIONED THE IMMEDIATE NEED FOR THE RULE AND THE OVERALL BENEFITS AND COST EFFECTIVENESS OF " PIECEMEAL" RESOLUTION CONSIDERING THAT OTHER GENERIC ISSUES COULD BE VIEWED TO BE INTEGRALLY RELATED TO THE SEVERE ACCIDENT POLICY AND THE l ASSELSTINE/ED0 10/10/85 4
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QUESTION 2. (CONTINUED)
RESOLUTION'0F USI A-44. .TO RESTATE: THE "ZERO HOUR" COPING CAPABILITY WAS RELATED TO A CONCERN ABOUT THE FUNDAMENTAL RULE ,
STRUCTURE AND ITS LOGIC, NOT TO THE PRA DETAILS. ^
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i QUESTION 3. IF THE PROPOSED RULE WERE IMPLEMENTED, WHAT WOULD STAFF BELIEVE THE MEAN PROBABILITY OF A STATION BLACK 0UT EVENT TO BE AND WHAT WOULD BE THE RANGE OF PROBABILITIES ENCOMPASSING ALL PLANTS?
ANSWER.
THE STAFF ESTIMATES THAT THE PROBABILITY OF CORE MELT DUE TO STATION BLACKOUT FOR INDIVIDUAL PLANTS IS CURRENTLY IN THE RANGE FROM 10-4 TO NEAR 10-6/ REACTOR-YEAR. IMPLEMENTATION OF THE BLACKOUT RULE IS EXPECTED TO HAVE LITTLE IMPACT ON THOSE PLANTS :
ALREADY AT THE LOWER END OF THE SPECTRUM EXCEPT TO PROVIDE GREATER ASSURANCE THAT THE CAPABILITY TO COPE ALREADY DESIGNED INTO THOSE PLANTS WILL BE READILY AVAILABLE, BUT WOULD LOWER THE PROBABILITY TO APPROXIMATELY 10-5/ REACTOR-YEAR FOR PLANTS AT THE UPPER END. THE RESULTING MEAN PROBABILITY FOR THE TOTAL POPULATION OF PLANTS IS DIFFICULT TO ESTIMATE SINCE IT IS DEPENDENT UPON THE COPING CAPABILITY FOR EACH FACILITY, AND THE PLANT-SPECIFIC INFORMATION NECESSARY TO MAKE THIS EVALUATION IS NOT AVAILABLE TO THE STAFF. HOWEVER, IT SHOULD BE BETWEEN 10-5 AND 10-6 PER REACTOR-YEAR.
l ASSELSTINE/ED0 10/10/85 l
t
t QUESTION 4. THIS RULE APPEARS TO BE PREMISED ON MAKING BLACKOUT AND ANY OTHER ACCIDENT SEQUENCE A 10-5 EVENT PER YEAR. WHAT MORE WOULD HAVE TO BE REQUIRED IF INDIVIDUAL ACCIDENT SEQUENCES WERE TO HAVE A PROBABILITY OF NO MORE THAN 10-6 PER YEAR CONSISTENT WITH THE DIRECTOR OF NRR RECOMMENDATION ON THE SAFETY GOAL?
ANSWER.
A REDUCTION IN THE CORE MELT FREQUENCY FROM STATION BLACK 0UT CAN BE ACHIEVED BY INCREASING OFFSITE POWER RELIABILITY, ,
INCREASING ONSITE EMERGENCY AC POWER RELIABILITY, INCREASING REDUNDANCY IN ONSITE EMERGENCY POWER SOURCES, OR INCREASING THE COPING CAPABILITY FOR STATION BLACK 0UT OR SOME COMBINATION OF THESE. IMPROVEMENTS HAVE BEEN, AND ARE BEING, MADE IN SWITCHYARDS PRONE TO SINGLE FAILURE TO REDUCE PLANT-CENTERED LOSSES OF 0FFSITE POWER. THERE HAVE BEEN MANY EFFORTS, PARTIALLY SUCCESSFUL, TO IMPROVE THE RELIABILITY OF EDGS. THE ADDITION OF AN ONSITE GAS-TURBINE GENERATOR THAT CAN PROVIDE POWER DIRECTLY TO EMERGENCY BUSSES WOULD BE AN EFFECTIVE, BUT COSTLY, ADDITION.
THE EXTENSION OF COPING TIME BEYOND THAT PRESENTLY CONSIDERED IN l
ASSELSTINE/EDO 10/10/85 1
l t
, QUESTION 4. (CONTINUED)
THE REGULATORY GUIDE IS FEASIBLE AND WOULD BE EFFECTIVE IN REDUCING FURTHER THE ESTIMATED CORE MELT FREQUENCY FROM STATION BLACKOUT.
A SIMPLIFIED METHOD TO ESTIMATE STATION BLACK 0UT CORE DAMAGE FREQUENCY IS PRESENTED IN APPENDIX C OF NUREG-1032, " EVALUATION OF STATION BLACK 0UT ACCIDENTS AT NUCLEAR POWER PLANTS". TABLE C.4 PROVIDES ESTIMATES OF THE CORE DAMAGE' FREQUENCY (PER REACTOR-YEAR) AS A FUNCTION OF DIESEL GENERATOR CONFIGURATION, DIESEL UNRELIABILITY, OFFSITE POWER CLUSTER AND COPING CAPABILITY , .
(HOURS). THESE TABLES INDICATE THAT MOST PLANTS WOULD MEET THE VALUE OF 10~0 PER YEAR IF THEY HAD A DIESEL RELIABILITY OF 0.99 AND COPING CAPABILITY OF 16 HOURS.
=ar ASSELSTINE/EDO 10/10/85
QUESTION 5. WHAT ARE THE ROOT CAUSES OF STATION BLACKOUT AND HOW WOULD THIS PROPOSED RULE CORRECT THE ROOT CAUSES?
ANSWER.
THE ROOT CAUSES OF STATION BLACK 0UT ARE THE VARIOUS FACTORS THAT
- ADVERSELY AFFECT THE RELIABILITY OF BOTH THE OFFSITE AND ONSITE EMERGENCY AC POWER SYSTEMS. THE AVERAiE FREQUENCY FOR THE LOSS OF OFFSITE POWER IS 0.1 PER SITE-YEAR, AND THE AVERAGE DIESEL GENERATOR RELIABILITY IS 0.98 PER DEMAND, WITH A RANGE FROM 0.90 .
TO 1.0 PER DEMAND. THESE DATA ARE DERIVED FROM MANY YEARS OF OPERATING EXPERIENCE. ALTHOUGH THERE HAS BEEN SOME IMPROVEMENT IN RELIABILITY, BOTH FOR OFFSITE POWER AND ONSITE DIE 3EL GENERATORS, IT HAS NOT BEEN SUFFICIENT TO ELIMINATE THE CONCERN FOR STATION BLACKOUT.
THE PROPOSED RULE ITSELF DOES NOT ADDRESS THE ROOT CAUSES, BUT ENSURES THAT EACH PLANT WOULD HAVE THE CAPABILITY FOR COPING WITH A STATION BLACK 0UT FOR A MINIMUM DURATION. THE DURATION OF THE COPING CAPABILITY DERIVES DIRECTLY FROM THE EXPERIENCE DATA BASE WHICH SHOWS THAT THE PROBABILITY OF RESTORING OFFSITE POWER (AND ONSITE POWER) INCREASES SIGNIFICANTLY OVER A MATTER OF HOURS. BY FORMALIZING A REQUIREMENT FOR AN A.C.-INDEPENDENT ASSELSTINE/ED0 10/10/85
QUESTION 5. (CONTINUED)
DECAY HEAT REMOVAL SYSTEM ALREADY INCLUDED IN NUCLEAR POWER PLANTS, AND ADDING IMPROVEMENTS, AS NECESSARY, FOR BATTERY POWER, CONDENSATE STORAGE, COMPRESSED AIR STORAGE, EQUIPMENT COOLING, AND REACTOR COOLANT PUMP SEAL INTEGRITY, A SEPARATE AND DIVERSE RESOLUTION OF THE STATION BLACK 0UT ISSUE IS ACHIEVED.
THE DRAFT REGULATORY GUIDE DOES PROVIDE GUIDANCE ON MINIMIZING, OR RECOVERING FROM, LOSSES OF AC POWER. MINIMUM RECOMMENDED DIESEL GENERATOR RELIABILITIES ARE SPECIFIED. AS DISCUSSED IN SECY-85-163, A PROGRAM TO IMPROVE DIESEL RELIABILITY IS BEING :
DEVELOPED UNDER GENERIC ISSUE B-56, " DIESEL GENERATOR RELIABILITY".
THIS PROGRAM WILL ESTABLISH A BASIS FOR MAINTAINING AND DETERMINING THE RELIABILITY OF EMERGENCY DIESEL GENERATORS. WITH REGARD TO OFFSITE POWER, THE PROPOSED REGULATORY GUIDE STATES THAT PROCEDURES SHOULD INCLUDE ALL ACTIONS NECESSARY TO RESTORE OFFSITE POWER AND USE NEARBY POWER SOURCES WHEN OFFSITE POWER IS UNAVAILABLE.
AN ALTERNATIVE, BUT LESS COST-EFFECTIVE RESOLUTION, WOULD BE TO REQUIRE MORE SOURCES OF ONSITE EMERGENCY POWER (DIESEL GENERATORS OR GAS TURBINES) TO PROVIDE POWER TO THE SAFETY BUSSES. SHOULD A LICENSEE DECIDE THAT SUCH ADDITIONAL POWER ASSELSTINE/ED0 10/10/85
' QUESTION 5. (CONTINUED)
SOURCES WERE COST EFFECTIVE BECAUSE OF OTHER BENEFITS (E.G.
IMPROVED PLANT AVAILABILITY), THEN A SHORTER COPING DURATION COULD BE JUSTIFIED UNDER THE PROPOSED RULE.
e P
ASSELSTINE/ED0 10/10/85
r QUESTION 6. WITH REGARD TO VIEWGRAPH 34, WHAT ARE THE UNCERTAINTY BOUNDS ON THE RISK REDUCTION FACTOR AND WHAT IS THE BASIS FOR SELECTING 80,000 MAN-REM FOR USE IN THE COST / BENEFIT ANALYSIS?
ANSWER.
THE 80,000 MAN-REM VALUE IS DETERMINED BY SUMMING THE ESTIMATED REDUCTION IN OFFSITE EXPOSURE FOR A STATION BLACK 0UT EVENT FOR THE NUMBER OF OPERATING PLANTS TIMES THE AVERAGE REMAINING LIFE OF THE PLANT (SEE NUREG-1109, FOR COMMENT, SECTION 4). THE ESTIMATED OFFSITE EXPOSURE IS A FUNCTION OF PLANT SIZE AND POPULATION DENSITY, AND RANGED FROM ABOUT 0.5 TO 7X10 6 MAN-REM / PLANT; THE AVERAGE VALUE IS APPROXIMATELY 2X106 MAN-REM / PLANT. THE MEAN REDUCTION IN CORE MELT FREQUNCY FOR ALL PLANTS IS APPROXIMATELY 3X10-5 PER REACTOR-YEAR, AND A VALUE OF 25 YEARS WAS ASSUMED FOR THE AVERAGE REMAINING PLANT LIFE. A POPULATION OF 67 OPERATING PLANTS WAS USED AND THE PLANTS WERE GROUPED BY SIMILAR CHARACTERISTICS (E.G. EDG CONFIGURATION, LOSS OF OFFSITE POWER CATEGORY). THE ANALYSIS USED 67 PLANTS BECAUSE SIGNIFICANT OPERATING EXPERIENCE WAS AVAILABLE FOR THIS GROUP ALONG WITH INFORMATION REGARDING OFFSITE POWER AND ONSITE POWER DESIGN CONFIGURATION. THE l
ASSELSTINE/ED0 10/10/85 l
\
QUESTION 6. (CONTINUED)
RESULTANT MAN-REM EXPOSURE REDUCTION WAS OBTAINED BY SUMMING THE CONTRIBUTION FOR EACH GROUP OF PLANTS RATHER THAN PERFORMING THE CALCULATION FOR EACH PLANT AND SUMMING THE RESULT.
THE 80,000 MAN-REM VALUE IS A BEST ESTIMATE CALCULATION AND COULD VARY EQUALLY ON EITHER THE HIGHER OR LOWER SIDE. BASED ON ESTIMATES AND SENSITIVITY ANALYSES IN NUREG-1032, THE ACTUAL CORE DAMAGE FREQUENCY COULD VARY BY ABOUT AN ORDER OF MAGNITUDE (HIGHER OR LOWER) FROM THE BEST ESTIMATE DEPENDING ON THE ACTUAL PLANT-SPECIFIC RELIABILITY PARAMETERS.
! ASSELSTINE/ED0 10/10/85
t QUESTION 7. PLEASE PROVIDE THE NUMERICAL SCALES FOR THE GRAPHS ON VIEWGRAPHS 20 AND 26 AND AN EXPLANATION OF HOW THE UPPER AND LOWER BOUNDS WERE DETERMINED.
RESPONSE.
THE INFORMATION PRESENTED ON VIEWGRAPHS 20 AND 26 WAS INTENDED TO CONVEY GENERAL CONCLUSIONS AND WAS NOT INTENDED TO BE QUANTITATIVE. ALTHOUGH THESE GRAPHS WERE QUALITATIVE IN NATURC, THEY WERE BASED ON INFORMATION IN APPENDIX A 0F NUREG-1032.
VIEWGRAPH 20 WAS INTENDED TO DISPLAY THE RANGE OF DATA ON FIGURE A-14 WHICH SHOWS THE FREQUENCY OF LOSS OF 0FFSITE POWER FOR DIFFERENT PLANT DESIGN AND SITE CHARACTERISTICS. VIEWGRAPHS 26 IS A COMPOSITE OF THE DATA GIVEN ON FIGURES 8.1, 8.2, AND 8.3 SHOWING THE ESTIMATED CORE DAMAGE FREQUENCY AS A FUNCTION OF STATION BLACKOUT COPING CAPABILITY AND THREE OTHER PARAMETERS, OFFSITE POWER CHARACTERISTICS, DIESEL GENERATOR RELIABILITY, AND DIESEL GENERATOR CONFIGURATION RESPECTIVELY. THE REFERENCED FIGURES FROM NUREG-1032 ARE ATTACHED.
ASSELSTINE/ED0 10/10/85 i
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10
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Figure 8.1 Sensitivity of estimated station blackout-core damage frequency to offsite power cluster, AC-independent decay heat removal reliability, and station blackout coping capability !
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Figure 8.2 Sensitivity of estimated station bla :kou'.-core damage frequency to emergency diesel genera ;or reliability, AC-independent decay heat removal reliability, and station blackout coping capability NUREG-1032 8-4
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figure 8.3 Sensitivity of estimated station blackcst-core damage frequency to emergency AC power configurations, AC-independent decay heat removal reliability, and station blackout coping capability NUREG-1032 8-5
f OVEST'ON 8. WHAT IS THE BASIS FOR THE ASSUMPTION THAT ALL PLANTS CAN NOW COPE WITH STATION BLACK 0UT FOR TWO HOURS? IF THE RULE WOULD REQUIRE A MINIMUM OF FOUR HOURS OF COPING CAPABILITY, WHAT IS THE RELEVANCE OF THE ABOVE ASSUMPTION't ANSWER.
THE MAIN CONSIDERATIONS FOR COPING WITH A STATION BLACKOUT ARE THE CAPACITY OF THE WATER SUPPLIES (E.G. CONDENSATE STORAGE TANK) THAT CAN BE USED TO REMOVE DECAY HEAT, THE CAPACITY OF THE DC POWER SYSTEM FOR THE OPERATION OF ESSENTIAL INSTRUMENTATION, CONTROLS AND LIGHTING, AND THE POTENTIAL LOSS OF PRIMARY SYSTEM COOLANT (DUE TO POTENTIAL REACTOR COOLANT PUMP SEAL LEAKAGE).
STAFF REVIEWS FOR PWRS UNDER TMI ACTION PLAN ITEM ll.E.1.1,
" AUXILIARY FEEDWATER SYSTEM EVALUATION", HAVE SHOWN THAT A WATER SUPPLY FOR AT LEAST TWO HOURS IS AVAILABLE UNDER STATION BLACKOUT CONDITIONS. FOR BWRS, SIMILAR REVIEWS HAVE SHOWN THAT A COMPARABLE CAPABILITY EXISTS FOR PLANTS WITH REACTOR CORE ISOLATION COOLING (RCIC) AND/OR HIGH PRESSURE CORE INJECTION (HPCI) SYSTEMS. FOR THE TWO BWR FACILITIES WITH l ASSELSTINE/ED0 10/10/85
t QUESTION 8. (CONTINUED)
ISOLATION CONDENSERS AND NO RCIC OR HPCI, AS LONG AS WATER IS ADDED TO THE ISOLATION CONDENSER, THE CORE COOLING CAPABILITY CAN BE MAINTAINED.
STAFF REVIEWS OF THE DC BATTERY CAPABILITY FOR BWRS AND PWRS ALSO SHOW A BATTERY CAPACITY OF AT LEAST TWO HOURS. THIS DURATION COULD PROBABLY BE EXTENDED BY SHEDDING NON-ESSENTIAL LOADS UNDER STATION BLACKOUT CONDITIONS.
THE EFFECT OF REACTOR COOLANT LOSS HAS BEEN EVALUATED BY THE LICENSEE FOR THE ST. LUCIE FACILITIES. THESE EVALUATIONS INDICATE THAT CORE COOLING IS MAINTAINED FOR APPROXIMATELY FOUR HOURS ASSUMING A PRIMARY SYSTEM LEAKAGE RATE OF 16 GPM.
CONSEQUENTLY, IT IS EXPECTED THAT MOST PWRS SHOULD HAVE AT LEAST A TWO-HOUR CAPABILITY.
THE RULE DOES NOT INCLUDE A SPECIFIC REQUIREMENT OF TIME FOR im COPING CAPABILITY. THE REGULATORY GUIDE PROVIDES AN EASILY USED METHOD THAT A LICENSEE CAN USE TO SELECT EITHER A FOUR-HOUR CAPABILITY OR AN EIGHT-HOUR CAPABILITY WHICH WOULD BE ACCEPTABLE TO THE STAFF IN MEETING THE REQUIREMENTS OF THE RULE. THE GUIDE ALSO PROVIDES FOR LICENSEES WHO WISH TO MAKE A ASSELSTINE/ED0 10/10/85
QUESTION 8 (CONTINUED)
SEPARATE ARGUMENT FOR A SHORTER TIME PERIOD BASED ON THE SPECIFIC CAPABILITIES OF THEIR PLANT. (THIS IS BECAUSE THE OBJECTIVE OF STATION BLACKOUT FREQUENCY OF ABOUT 10-5/ REACTOR-YEAR OR LESS CAN BE ACHIEVED FOR SOME DESIGNS AND SITE-CONFIGURATIONS WITH COPING CAPABILITY OF LESS THAN FOUR HOURS.)
e THE RELEVANCE OF THE INFORMATION REGARDING EXISTING COPING CAPABILITY IS IN ESTIMATING THE COST OF IMPLEMENTING THE RULE.
SYSTEMS FOR COPING WITH STATION BLACKOUT FOR SOME DURATION ARE ,
l ALREADY IN PLACE. THE PROPOSED RULE AND ASSOCIATED REGULATORY t
l GUIDE WOULD ASSURE THAT THE LENGTH OF TIME THAT THE NECESSARY SYSTEMS WILL FUNCTION IS SUCH THAT STATION BLACKOUT IS A RELATIVELY SMALL CONTRIBUTOR TO TOTAL CORE MELT FREQUENCY.
t l
i 4
ASSELSTINE/ED0
, 10/10/85 T
4
f QUESTION 9. REGARDING THE FOREIGN EXPERIENCE IDENTIFIED ON VIEWGRAPH 7 0F THE STAFF BRIEFING PACKAGE: A)
WHICH COUNTRIES REQUIRE GREATER PROTECTION (IN TERMS OF PREVENTION AND/OR MITIGATION) FOR ,
STATION BLACKOUT THAN CALLED FOR IN THE STAFF PROPOSED RULE 7 B) WHAT IS THE RATIONALE FOR NOT 3
REQUIRING A SIMILAR LEVEL OF PROTECTION AT THE U.S. PLANTS AS THAT APPARENTLY BEING ACHIEVED AT FOREIGN PLANTS 7 C) WHAT STATION BLACKOUT l
REQUIREMENTS HAVE BEEN BACKFITTED AT FOREIGN -
PLANTS 7 D) WHAT DOES THE STAFF KNOW ABOUT THE
. FOREIGN COST-BENEFIT ANALYSES ASSOCIATED WITH DECISIONS ON WHETHER TO LOWER THE STATION BLACKOUT RISKS 7 1 ANSWER.
THE FOLLOWING PROVIDES OUR UNDERSTANDING OF THE FOREIGN EXPERIENCE WITH THE STATION BLACKOUT ISSUE:
A) IN FRANCE, NUCLEAR POWER STATIONS ARE ABLE TO COPE WITH A STATION BLACKOUT LASTING THREE DAYS. (SEE RESPONSE TO QUESTION 3 FROM COMMISSIONER BERNTHAL FOR ADDITIONAL INFORMATION.) IN BRITAIN, THE SIZEWELL B l
ASSELSTINE/EDO 10/10/85 t
t QUESTION 9. (CONTINUED)
FACILITY INCLUDES A SEPARATE AC-INDEPENDENT CHARGING PUMP FOR REACTOR COOLANT PUMP SEAL COOLING. IN ADDITION, MANY EUROPEAN FACILITIES HAVE MORE REDUNDANT ONSITE AC POWER SUPPLIES (DIESELS) THAN IN THIS COUNTRY.
B) THE STAFF BELIEVES THAT IMPLEME!!TATION OF THE PROPOSED RULE WILL REDUCE THE RISK FROM STATION BLACKOUT S0 THAT IT IS NO LONGER A SIGNIFICANT CONTRIBUTOR.
- REQUIRING FURTHER IMPROVEMENTS FOR STATION BLACK 0UT BEYOND THE STAFF'S RECOMMENDATIONS MAY NOT BE COST EFFECTIVE.
C) THE FRENCH ARE BACKFITTING THEIR 900 MWE PLANTS WITH A STEAM-DRIVEN GENERATOR THAT CAN PROVIDE POWER FOR A PUMP TO COOL THE REACTOR COOLANT PUMP SEALS AND POWER FOR ESSENTIAL INSTRUMENTATION AND CONTROLS DURING A STATION BLACK 0Li.
1 D) THE STAFF HAS NO DETAILED INFORMATION ON FOREIGN
! COST-BENEFIT ANALYSES. HOWEVER, THE BACKFIT ON FRENCH PWRS IS ESTIMATED BY THE FRENCH TO COST ABOUT
$600 THOUSAND PER PLANT.
ASSELSTINE/ED0 10/10/85
i QUESTION 10. THE FRENCH HAVE EVIDENTLY ADOPTED THE FOLLOWING SAFETY GOAL AND BACKFITTING REGULATION:
"THE FREQUENCY OF OCCURRENCE OF ACCIDENTS BEYOND DESIGN THAT POTENTIALLY INVOLVE FUEL DAMAGE MUST BE IN THE ORDER OF 10-7 PER REACTOR YEAR (RY) OR LESS TO BE ADMISSIBLE WITHOUT ANY MITIGATION ACTION. IF THE PROBABILITY WERE HIGHER, MITIGATING ACTIONS WOULD BE REQUIRED ACCORDING TO THE FRENCH NUCLEAR SAFETY REGULATION,"
(EMPHASIS ADDED) (SEE, NUCLEAR SAFETY 26 [4]
JULY-AUGUST 1985, P. 427). ,
THE FRENCH HAVE EVIDENTLY APPLIED THESE PRINCIPLES IN DECIDING TO BACKFIT THEIR REACTORS WITH RESPECT TO STATION BLACK 0UT AND OTHER SAFETY ISSUES. THUS, IT APPEARS THAT THE FRENCH, AND PERHAPS MANY OTHER FOREIGN COUNTRIES, ARE REQUIRING AND ACHIEVING A SIGNIFICALLY GREATER LEVEL OF SAFETY THAN THE U.S. REACTORS. IS MY PERCEPTION CORRECT?
ASSELSTINE/EDO 10/10/85
QUESTION-10.' (CONTINUED)
ANSWER.
THE FRENCH GOAL FOR CORE UNC0VERY OR CORE MELT PER IS 10-7 REACTOR-YEAR FOR STATION BLACKOUT EVENTS AND OTHER " FAMILIES OF EVENTS" SUCH AS TOTAL LOSS OF FEEDWATER. THIS IS LESS THAN THE U.S. OBJECTIVE OF 10-5 PER REACTOR-YEAR FOR STATION BLACK 0UT.
THE U.S. OBJECTIVE WOULD MAKE STATION BLACKOUT A SMALL CONTRIBUTOR TO TOTAL CORE DAMAGE, FREQUENCY, WHEREAS IF THE FRENCH GOAL IS ACHIEVED, IT WOULD BE AN INSIGNIFICANT CONTRIBUTOR. HOWEVER, THERE COULD BE SUBSTANTIALLY INCREASED COSTS TO ACHIEVE THE :
LOWER GOAL. THIS MONEY COULD POSSIBLY BE SPENT MORE EFFECTIVELY TO REDUCE RISKS FROM OTHER ACCIDENT SEQUENCES WITH CORE DAMAGE FREQUENCIES GREATER THAN 10-5 PER REACTOR-YEAR.
ASSELSTINE/Eu0 10/10/85
_-