ML20207S165
| ML20207S165 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 03/13/1987 |
| From: | Donohew J Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8703190069 | |
| Download: ML20207S165 (25) | |
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! pug UNITED STATES o,j NUCLEAR REGULATORY COMMISSION g&
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9 e WASHINGTON. D. C. 20555
%, +%#....e March 13, 1987 Docket No. 50-219 LICENSEES:
GPU Nuclear Corporation Jersey Central Power and Light Company FACILITY:
Oyster Creek Nuclear Generating Station
SUBJECT:
JANUARY 20, 1987, FINUTES OF MEETING WITH BWR OWNEP,S GROUP TO DISCUSS SYSTEMS FOR COMBUSTIBLE GAS CONTROL DilRING A LOSS 0F COOLANT ACCIDENT On Tuesday. January 20, 1987, a meeting was held at NRC, Bethesda, Meryland, with representatives from GPU Nuclear (GPUN), Commonwealth Edison, Northeast Utilities and Nebraska Public Power District (NPPD) on the systems used in their Mark I containment (Mark-1) plants for combustible gas control. These licensees have the following boiling water reactor (EWR) plants: presden 2/3 and Quad Cities 1/?. (Commonwealth Edison), Cooper (NPPD), Millstone 1 (Northeast Utilities) and Oyster Creek (GPUN).
. is the meeting summary which describes the significant items discussed and the actions, if any, taken or proposed. Attachment 2 is the list of the participants that attended the meeting. Attachment 3 centains the bandout from the licensees for their presentation. The handout is arranged in the order of the licensees' presentation.
The staff recuested that each licensee submit its plant-specific position on its compliance to 10 CFR 50.44(g). This submittal should include the assumptions made by the licensees to.4ustify their position en 10 CFR 50.44 This submittal should also include the information discussed during the meeting on the reliability and capability of the containment inerting system and the window of accident sequences for which this system would be effective in controlling combustible gases. The staff stated that a pas;ive system, such as the inerted containment, is not sufficient to meet 10 CFR 50.44(g) and that an active system, such as the containment inerting system, is required. The staff further stated that the reliability and capability of the e:'isting containment inerting systems may be sufficient to meet, as a minimum, the intent of the GDC 41, 42 and 43 of i
10 CFR 50.44(g). This is because the RG 1.7 hydrogen and oxygen source term
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indicative of large metal-water reactions may show that the licensee has sufficient time to respond with the existir.g system to the increasing combustible gasses concentrations in the containment from radiolysis of water before the acceptable limits are exceeded.
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The time available until unacceptable concentrations are reached would allow the licensee to overcome the lack of redundancy in components and in providing power to the system. This time period for the plant and the actions taken by the licensee should be discussed in the licensee's justification of the reliability of its conteinment inerting system.
i
/ <Jc N. Donoh
, Jr., Pro,iect Manager U BWR Project Directorate #1 Division of BWR Licensing Attachments:
1.
Summary 2.
List of Attendees 3.
Licensees' Handout for Meeting cc w/ attachments:
See next page i
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Distribution for Meetina Sumary dated: March 13, 1987 Facility: Oyster Creek Nuclear Generating Station *
, Docket: File 250419 2'"
.NRC PDR
. Local PDR
.BWD1 Reading J. Zwolinski J. Donohew C. Jamerson 0GC-BETH (Info only)
E. Jordan B. Grimes ACRS (10)
R. Bernero G. Lainas J. Hulman J. Kudrick J. Stang J. Shea W. Long T. Rotella OC file
- Copies sent to persons on facility service list i
1.
m.
Oyster Creek Nuclear Generating Station cc:
Mr. Ernest L. Blake, Jr.
Resident Inspector Shaw, Pittman, Potts and Trowbridge c/o U.S. NRC 2300 N Street,ilW Post Office Box 445 Washington, D.C.
20037 Forked River, New Jersey 08731 e
J.B. Liberman, Esquire Commissioner Bishop, Liberman, Cook, et al.
flew Jersey Department of Energy 1155 Avenue of the Americas 101 Concerce Street New York, New York 10036 flewark, New Jersey 07102 Mr. David M. Scott, Acting Chief Regional Administrator, Region I Pureau of Nuclear Engineering U.S. Nuclear Pegulatory Commission Department of Environmental Protection 631 Park Avenue CN 411 King of Prussia, Pennsylvania 19406 Trenton, New Jersey 08625 L
BWR Licensing Manager Mr. P. B. Fiedler f
GPU Nuclear Corporation Vice President & Director i Upper Pond Road Oyster Creek Nuclear Generating Parsippany, New Jersey 07054 Station Post Office Box 388 Deputy Attorney General Forked River, New Jersey 08731 State of New Jersey Department of Law and Public Safety 36 Vest State Street - CN 112 Trenton, New Jersey 08625 Mayor Lacey Township 818 West Lacey Road Forked River, t'ew Jersey 08731 Licensing Manager Oyster Creek Nuclear Generating Station Mail Stop:
Site Emergency Bldg.
P. O. Rox 388 Forked River, New Jersey 08731
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I i
ATTACHMENT 1
SUMMARY
OF JANUARY 20, 1987 MEETING WITH BWR OWNERS GROUP INVOLVING COMBUSTIBLE GAS CONTROL t
The licensees began their presentation with a history of the licensing activity concerning combustible l gas control systems. These are pages 1 through 5 in the handout. The regulations governing the standards for these systems are contained in 10 CFR 50.44 These regulations are discussed below:
Paragraph 50.44(c)(3)(i) requires each Mark I containment be normally inerted during power operation., All these plants meet this requirement and the containments are inerted for power operation except for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> during startup to inert and shutdown to deinert.
Paragraph 50.44(c)(31(ii) requires plants relying on a purge /repressurization system as the primary means of combustible gas control shall have an installed recombiner capebility. The Comissior determined in Generic Letter 84-09 dated May 8, 1984, that Mark I plants did not have to have tH s capability if I
the plant met the 3 technical criteria listed in the letter. The 3 criteria are given on pace 3 of the handout.
Paragraph 50.44(g) re Design Criteria (GDC) quires alll combustible gas control systems to meet General 41, 4? and 43. This regulation applies only to those plants which have the notice ofihearing on its application for the construction permit published on or before December 22, 1968. All of the plants involved 4
in this meeting meet this condition end paragraph 50.44(g) applies to them.
The GDC are in Appendix A to 10:CFR Part 50.
The licensees stated that their. plants comply with the above regulations. The containments tre inerted during: power operation except briefly (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) during startup and shutdown. This is allowed by the plant Technical Specifi-cations (TS).
It is the licensees' position that the primary means of combustible gas control is the inerted containment and not a purge /repressurization system, and the licensees have addressed in submittals to NRC how the 3 criteria in GL 84-09 are met at their plants. Therefore, the licensees stated that a hydrogen recombiner capabilit system of Faragraph 50.44(g) y is not reouired, the combustible gas control is the inerted containment and it meets GDC 41 to i
- 43. The basis for the licensees' conclusion that the inerted containment is l
sufficient to assure peak combustible gas concentrations are below acceptable limits without the need to take any action to purge, repressurize or provide a recombiner is General Electric Report NEDO-??155, " Generation and Mitigation of Combustible Gas Mixtures in Inerted BWR Mark I Containments" dated 1982.
The licensees stated that the NRC has identified some concerns in its review of NEDO-22155. This report was part of the NRC staff's basis for and was
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indirectly addressed in GL 84-09. The licensees explained that these concerns, j
listed in page 5 of the handout were addressed in a subnittal dated November 5, l
1982, from Millstone 1 which had additional information not given in NED0-22155.
This additional information was not discussed in this meeting.
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The licensees discussed the typical system used to inert or de-inert the certainment at their plants. The figure on page 6 is a typical containment inerting system for these plants. This system is operated during startup to inert the containment with nitrogen. This is through the nitrogen (N )
2 makeup line and purging the containment through the ventilation exhaust lire.
The cortainment atmosphere is reduced to less than 4% oxygen for power operation. During shutdown, the containment atmosphere is increased to atmospheric conditions using the nitrogen purge line and the ventilation exhaust line. The containment is inerted during startup and de-inerted during shutdown to allow personnel to be in containment with a breathable etmosphere and conduct needed surveillance of the reactor coolant system while the reactor is et high temperature and pressure. This period of time is restricted by TS to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for startup and 74 hours8.564815e-4 days <br />0.0206 hours <br />1.223545e-4 weeks <br />2.8157e-5 months <br /> for shutdown.
The licensees explained that this containment inerting system is a backup to the inerted containment for controlling combustible gases during a LOCA. This system could be used to purge the containment of sucF gases or to pressurize the containment to dilute the concentration of the gases. The licensees presented page 8 of the handout which compares the inerted containment and the containment inerting system to GDC 41, 42 and 43 o' 10 CFR 50.44(g). The licensees concluded that the containment inerting system almost meets these GDC J
except for icss of power to the system and lack of some redundancy in components.
The " features" referred to on page 8 are the plant-specific features in the systems at each plant. These features might he different for each plant. The licensees explained that the containment inerting system is used continually during power operation. Pesides startup and shutdown, thes.
ystems are used during pcwer operation to maintain pressure in the atmosphere at about 1 psi gcuge and to reduce containment pressure for the monthly tests of the torus-to-dryvell vacuum breakers. The licensees stated that no additional surveillance should be needed for these systems to meet GDC 47 and 43.
The licensees further explained that the difference between the existing inerting system and a system meeting GDC 41 is the lack of redundancy in components end in supplying power. The existing inerting systems do not meet GDC 41 on single failure.
The staff stated that it did not consider the containment inerting system as a backup to the inerted containment. This system could not itself deal with the metal water reaction which generates large quartities of hydrocen at a high rate at the beginning of an accident. The production rate of hydrogen is too high for the current inerting system alone to keep combustible gases within acceptable limits. The inerted contairment is the safety system to keep the hydrogen from the metal water reaction vithin acceptable limits.
For the duration of an accident, an active combustible gas control system is required to maintain the hydrogen and oxygen concentrations from the radiolysis of water within acceptable limits.
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The licensees continued their presentation with a discussiori on when the inerting systems would be effective during accidents. This is paces 9 Wo 15 of the handout. The' licensees stated that these systems are effective only for accident sequences where the metal water reaction is bJtween 1% and 10%_of the fuel cladding and channels in the core. The licensees explained that.this is based on the. report NED0-22155 which shows that for above 10% the amount of hydrogen in containment will suppress the generation of oxygen and hydrogen generated from the radiolysis of water. This would be through the recombination of oxygen and hydrogen.
s The licensees' conclusions of this discussion are on pages 14 and 15 of the handout. Page 14 is the accident event tree for the_ containment inerting system i
for Millstone Unit 1.
The system is effective for, only 1.7% of all core damage accident seouences.
For this 1.7%, the system is effective 99.5% of the time. The existing system failure rate with core damage is only 2.6 x 104 events / year.
The licensees stated that requiring the existing containment inarting system to meet 10 CFR 50.44(g) could at best only raise the effectiveress of the system by 0.5% from 99.5% to 100.0%,
The licensees concluded their presentation with 'the following:,)(4) the Mar plants meet 10 CFR 50.44(g) with the inerted containment and (2 the existing 4
non-safety containment inerting sy tems are sufficient for addressing those accident sequences where the metal water reaction is betfeen 1% and 10%.
This is page 16 of the" handout.
.J The staff stated that the window of accide'nt sequehces where?thE containment N
inerting system is effective may be too small.
It further stated that the arguments presented had been reviewed wher./ the staff reviewed NED0a22155 prior to issuing GL 84-09. The staff did not agree with the report conclusion that i
.above 10% metal water reaction the hydrogen generated suppressed the 'further i
generation of oxygen and hydrogen from the radiolysis of water.
It stated that the uncertainties listed on paoe 5 of the handout were the ' oasis for the staff's position that Regulatory Guide (RG) 1.7 should be used to. calculate the generation of combustible gases during an LOCA.
In response to the staff, the licensaes stated that if RG 1.7 were used, the j
number of accident sequences in which the inerting system could be used does
}
increase. The licensee further stated that the existing system should be sufficiently reliable to handle these additfor.al sequences; however,if this increase in accident sequences is high enough, it would be the justification for having the system meet GDC 41, 42 and 43.
/
The staff requested that each licensee submit its plant-specific position on its compliance to 10 CFR 50.44(g). This submittal should include the assumptions made by the licenrees to justify their position on 10 CFR 50.44.
This submittal should also include the information discussed during the meeting on the reliability and capability of the containment inerting system and the window of accident sequences for which this's'ystem would be effective in controlling combustible gases. The staff stated that a passive system, such as the inerted containment, is not sufficient to meet 10 CFR 50.44(g) and j
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,g l-that an active system, such as the containment inerting system, is required.
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The staff further stated that the reliability and capability of the existing containment inerting systems may be sufficient to meet, as a minimum, the intent of the EDC.41, 42 end 43 of 10 CFR 50.44(g). This is because the RG 1.7 hydrogen and o'xygen source terms indicative of large metal-water reactions may show that the licensee has sufficient time to respond with the existing system J
to the increasing combustible casses concentrations in the containment from radiolysis of water before the acceptable limits are exceeded. The time available until ur. acceptable concentrations are reached would allow the licensee to overcome the lack of redundancy in components and in providing power to the system. This time period for the plant and the actions taken by the licensee should be discussed in the licensee's justification of the reliability of its containment inerting system.
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ATTACHMENT 2 MINC-Ok'TOS MEETING TO DISCUSS SYSTEMS FOR CCFFUSTIBLE GAS CONTROL JANUARY 20, 1987 t
NAME ORGANIZATION
' T. Rotella NRC/NPR/ DBL /BWD1 I.' Johnson CECO-Nuclear Licensing
- 4. Zwolinski NRC/NRR/ DBL /BWD1 D. Farrar CECO-Nuclear Licnesing E. Powley Ceco-Engineering R. Benero NRC/NRR/ DBL G. Lainas NRC/NPR/ DBL J. Donohew NRC/NRR/ DBL /BWD1 T. Pickens NSP-Licensing L. Nexbitt GE San Jose Engineering J. Lachcreayer GPUN G. Smith YPPD Licensing C. Grimes NRC/NRR/DFLB/ISAPD P. Blasioli NU-Licensina J. Stang NRC/NRR/ DEL /BWD1 J. Shea NRC/NRR/DPLB C. Wright GE-Licensing P. Hearn NPC/fiRR/ DBL /PSB J. Kudrick NRC/NRR/ DBL /PSB J. Hulman NRC/NPR/ DBL /PSB L. Gifford GE-Licensing M. Laggart GPUN Commonwealth Edisor (CECO)
GPU Nuclear (GPUN)
Nebraska Public Power District (NPPD)
-Northern States Power (NSP)
Northeast Utilities (NU)
/
6 i
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ATTACHMENT S e>
LICENSINGHISTORY o
1978-Issuanceof10CFR50.44(g)ACombustibleGasControl System.
-Purgesystemisacceptableifradiationdoselimitsaremet anddesigned-inconformancewithGDC41,42and43.
Otherwise,
-Anothertypeofcombustiblegassystemcontrolin conformancewithGDC41,42and43shallbeprovided o
1981-Issuanceof10CFR50.44(c)(3)(ii?
-Requiredeitheraninternalrecombiperorthecapabilityto installanexternalrecombinerforthosereactorsthatrely uponapurge/repressurizationsystemastheprimarymeans forcombustiblegascontrol.
s
,A.
o 1982NED0-22155"GenerationandMitigationofCombustibleGas MixturesinInertedBWRMarkIContainments"wasprepared.
-ConclusionsfromReport
-Peak 0xygenconcentrationsforMarkIplantswithinerted 4
containmentsisbelowtheRegulatoryGuide1.7 combustible gasconcentrationlimitwithouttheneedforcontainment venting.
-TheexistinginertedMarkIcontainmentdesignis sufficienttoassurepeakcombustiblegasconcentrations whicharebelowallowablelimitswithouttheneedtovent the containment, repressurize the containment or to install recombiner capability.
-Ownersprovidedevaluationsdemonstratingapplicabilityof NED0-22155 totheirplants
-ConclusionsarevalidfortheDesignBasisAccidentLOCA whichincludesthatdescribedin10CFR50.44
o 1984GenericLetter84-09wasissued 1
- The Commission has determined that a Mark I M plant will befoundtonotrelyuponpurge,repressurizationsystemsas theprimarymeansofhydrogencontrol,ifcertaintechnical criteriaaresatisfied.
1.
Theplanthastechnicalspecifications(limiting conditionsforoperation)requiringthat,whenthe containmentisrequiredtobeinerted,thecontainment atmospherebelessthanfourpercentoxygen,and 2.
Theplanthasonlynitrogenorrecycledcontainment atmosphereforuseinallpneumaticcontrolsystems withincontainment,and 3.
Therearenopotentialsourcesofoxygenincontainment otherthanthatresultingfromradiolysisofthe reactor coolant.
Consideration of potential sources of inleakageofairandoxygenintocontainmentshould includeconsiderationofnotonlynormalplant operatingconditionsbutalsopostulated i
loss-of-coolant-accident conditions.
These potential sourcesofinleakageshouldincludeinstrumentair systems,serviceairsystems,MSIVleakagecontrol systems,purgelines,penetrationspressurizedwithair andinflatabledoorseals.
o)
UtilityCompliancewithRegulations TheprimarymeansofcombustiblegascontrolforMarkI containmentsisaninertedcontainment.
-Utilitieshaveaddressedthe3criteriainGenericLetter 84-09,thereforehydrogenrecombinercapabilityisnot required.
-Regulationdoesnotlimittheoptiontohydrogenrecombiners g a purge repressurization system that meets cr'iteria 41, 42and43ofAppendixA.
-InertedMarkIcontainmentsconstituteameansof combustiblegascontrolasrequiredby10CFR50.44(g).
Y
1986 RECENT NRC CORRESPONDENCE o
NRC HAS IDENTIFIED SOME CONCERNS FOR WHICH A NARROW BAND OF ACCIDENT SEQUENCES COULD RESULT IN ADDITIONAL OXYGEN GENERATED.
AMONG THESE ARE:
f 1.
DURATION OF BOILING WITHIN THE CORE 2.
DEGREE OF FUEL R0D DAMAGE 3.
EFFECT OF WATER CONTAMINATION ON THE OXYGEN GENERATION PROCESS J
o WITHIN THE ENVELOPE OF 10 CFR 50.44 THESE CONCERNS WERE ADDRESSED BY THE filLLSTONE SUBf1ITTAL IN 1982]
MwemhngLW2
~JhigpSouflid Y a)OlgncS Qimdie M k kDo-drcament.
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FROM REACTOR BLOG. ATMOSPHERE 4
1 4
4
CONTAINMENT INERTING SYSTEM
- i o
DESIGNED TO INERT CONTAINMENT WITHIN 24 HOURS o
SUPPLY SYSTEM (TORUS & DRYWELL)
LIQUID NITROGEN TANK MANUAL CONNECTION FOR TUBE TRAILER HOOK-UP o
FILL SYSTEM (TORUS & DRYWELL)
PURGE LINE MAKE UP LINE o
VENTING SYSTEM (TORUS & DRYWELL)
REACTOR BUILDING VENTILATION STAND BY GAS TREATMENT (SAFETY RELATED) l REDUNDANT CONTAINMENT ISOLATION VALVES ON ALL LINES NORMALLY OPERATED SYSTEM L
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3 CRITERIA 41 PRIMARY SYSTEM BACKUP SYSTEM CONTAINMEh! ATMOSPHERIC CLEANUP CONT I NT VENT & PURGE
- CONTROL 0: HYDR 0 GEN & 0XYGEN COMPLY FEATURES PROVIDED
- REDUNDAhtY IN COMPONENTS AND FEATinES N/A FEATURES PROVIDED
- LEAK OETECTION COMPLY FEATURES PROVIDED
- ISOLATION AND CONTAINMENT CAPABILITIES COMPLY FEATURES PROVIDED
- ACCOMPLISH SAFETY FUNCTION WITH:
LOSS OF ON-SITE AND OFF-SITE POWER ASSUMING SINGLE FAILURE COMPLY FEATURES NOT PROVIDED
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O CRITERIA 42 INSPECTION OF CONTAINMENT ATMOSPHERIC CLEANUP SYSTEMS
- DESIGNED TO PERMIT INSPECTION OF COMPONENTS COMPLY FEATURES PROVIDED o
CRITERIA 43 TESTING OF CONTAINMENT ATMOSPHERIC CLEANUP SYSTEMS
- DESIGNED TO PERMIT APPROPRIATE PERIODIC TESTING COMPLY OPERATIONALLY TESTED
VENT AND PURGE SYSTEMS ARE EFFECTIVE FOR THOSE ACCIDENT SEQUENCES WHERE METAL WATER REACTION IS 71% BUT410% OF CLADDI.NG AND CHANNELS (APPR0XIMATELY 2% To 20% OF ACTIVE FUEL CLADDING).
4 AB0VE 10% THE AMOUNT OF HYDROGEN SUPPRESSES ANY OXYGEN FROM RADIOLYSIS.
TIME DURATIONS TO REACH 1% AND 10% MWR BASED ON MARCH CODE ANALYSIS AND ENGINEERING JUDGEMENT EVENTS:
1% MWR 10% MWR A)
REACTOR ISOLATION WITH LOSS OF ALL RPV COOLANT 45 MIN.
60 MIN.
INJECTION AT TIME ZERO.
B)
REACTOR ISOLATION WITH LOSS OF COOLANT INJECTION 510 MIN.
540 MIN' AT 6 HOURS FROM SCRAM 6
- ExcludedScenarios:
Eventsforwhichcontainmentwilleventuallyfaildueto overpressurization(LossofResidualHeatRemovalandATWS).
LineBreakLOCAevents--Coredamagecouldstartwithinfirst 15 minutes.
1 Thoseeventswheretimedurationisfrom510 min.to540 min.--Verysmallcontributiontocoredamagefrequencydue tohighprobabilityofpowerrecoveryandsuccessful mitigationduringthe.first6 hours.
I0
TransientAccidentsequencesaremostlikelytoberecovered before 10% MWR is reached.
These sequences have the following characteristics:
-Lossofcoolantinjection
-Recoverytimedurationisintheorderof15 min.to30 min.
4 after1/2 hour
-Recoveryfromhardwarefailuresisunlikelyduetotheshort timelimit
-Recoveryactionsbyplantpersonnelwithintheshorttime windowaredifficult
-Scenarioswhichrequireelectricalpowerrecoveryarethemost probable
- SequenceswhereVentandPurgesystemiseffectivearethose initiatedbylossofoff-sitepowerfollowedbyfailureof IsolationCondenser,FeedwaterandDepressurizationFunction.
(NUREG/CR-3085-Chapter 8) l l
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ConservativeCoreDamagefrequency(CDF)of3xE-4 events (MillstonePlant) 3,4'5oftotalaccidentsequenceshaveachanceofbeing recovered in the l'5 to 10's MWR range.
(Sequences where Vent and Purgesystemsareeffective)
Probabilityofrecoveryofelectricalpowerwithin45 min,is estimatedtobe0.505(NUREG/CR-3085-PageC-22)
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VENT AND PURGE SYSTEM UNAVAILABILITY CONSERVATIVELY ASSUMED THAT ALL AIR OPERATED VALVES ARE TESTED ONLY AT 18 MONTH INTERVALS, RECOVERY OF VENT AND PURGE SYSTEM COMPONENTS WHEN SYSTEM IS DEMANDED WAS NOT CONSIDERED, (CONSERVATIVE, SINCE ADEQUATE TIME EXISTS (AT LEAST 24 HOURS) FOR REC 0VERY OF THE MOST l
LIKELY FAILED COMPONENTS.)
l l
MAJOR CONTRIBUTOR TO UNAVAILABILITY IS CONTROL POWER.
TOTAL CALCULATED UNAVAILABILITY IS 5 X E-3/ DEMAND WHICH CONSISTS OF:
3.48 X E-3/ DEMAND DUE TO HARDWARE FAILURES 1.40 X E-3/ DEMAND DUE TO CONTROL POWER FAILURES
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Conclusions:
-VentandPurgesystemprovideseffectivemitigationforonly 1.7%oftotalpopulationofcoredamageaccidentsequences.
(p=0.034x0.505=1.7%)
-Forthe1.7%ofsequenceswheremitigationbyVentandPurge systemispossible,thesystemiseffective99.5%ofthetime
-CalculatedCDFwherecurrentstandardVentandPurgesystem failsis2xE-8 events /yr.
-Assumingwehadaperfectsystem(betterthansystemdesigned tocriteria41,42and43)themaximumpossiblebenefitwould beareductioninCDFof2xE-8 events /yr.
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CONCLUSIONS LICENSING f
BWRMarkIunitsmeettherequirementsdescribedin 50.44(g)withinertedcontainments.
AnEventWhichExceedthatDescribedin50.44 Non-safetyrelatedsystemsaresufficienttoaddress those events where MWR is >l'5 but <10'5 and use of Vent andPurgesystemiseffective, h