ML20236K389
| ML20236K389 | |
| Person / Time | |
|---|---|
| Issue date: | 04/08/1987 |
| From: | Speis T Office of Nuclear Reactor Regulation |
| To: | Pratt W BROOKHAVEN NATIONAL LABORATORY |
| Shared Package | |
| ML20236K304 | List:
|
| References | |
| CON-FIN-A-3786, FOIA-87-380, TASK-082, TASK-82, TASK-OR NUDOCS 8708070101 | |
| Download: ML20236K389 (13) | |
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April 8, 1987 Dr. W. Trevor Pratt Department of Nuclear Energy Brookhaven National Laboratory Upton, NY 11973
Dear Dr. Pratt:
Subject:
NRC Staff Coments on BNL Draft Report "Beyond Design Basis Accidents In Spent Fuel Pools (Generic Issue 82)," dated January 1987 (FIN No. 3786)
Detailed NRC staff comments on the A.3786 report (forwarded to BNL on April 2, 1987) have been compiled in the enclosed list by major areas of concern. This list should be used by BNL for the agenda for our upcoming meeting on April 21, 1987 in Bethesda, Maryland.
We have initiated a Technical Assistance contract with the Lawrence Livermore National Laboratory to provide us with the estimated fragility of actual spent fuel pool structures and to assess the structural capacity of a spent fuel pool wall for the shipping cask drop accident.
We request that BNL be prepared to address the enclosed infonnation at our meeting and that BNL also begin to develop recommendations to address the more detailed NRC comments. One of our objectives is to complete the meeting with a firm schedule commitment to finalize the report and agree on a) what should be included, and b) what should be identified as additional follow-up work.
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Please contact the Task Manager, Mr. Edward D. Throm, if you need additional information or clarification on our coments or objectives for the meeting.
Sincerely, ORicyxAL stage gy Themis P. Speis, Director Division of Safety Review & Oversight
Enclosure:
Comments on BNL Draft Report cc:
K. Perkins, BNL R. Bari, BNL Distribution RSIB R/F Central fil s DSR0 C/F EThrom GMazetis 8708070101 070B04 Qrs
- SEE PREVIOUS CONCURRENCE.
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l Consents On ENL Draft Report Eeyond DEAs in Spent Tuel Fools" Cl-22 Content 1
Seistic Hasard Curves Page 2
- 2. Spent Tuel Fool Tragility Page 3
- 3. Shipping Cask Drop Page 4
E 4.
Tallure Assumptions Page 5
5.
Spent Tuel Fool Inventery (equivalent cores)
Page 6
l l
4 Tassion Product Inventory (ORICEN2 Code Use)
Page 7
l 7.
Tission Product Release Trom Tuel Matris Page 8
8.
Tission Product Release Te Atmosphere Page 9
9.
Consequences (CRAC2 Code Use)
Page 10
- 10. Risk Reduction Measures Page !!
- 11. Other Issues Identified During Review Page 12 4
Page 1
I Cctsents On ENL Draft Re; ort "Eeyond DEAs in Spent ruel Fools" Cl-f 1
1 SE!SM!c HA AEr CUPVES EHL esed Millstone SEP seismic hasards cutves for BVR evaluation and generated a 'sytthesised" curve fer Cinna (PVR evaluation)
MAJCF _COMMENTE : (RRAE/DSRO, EB/DPL-A, EE/DPL-B)
A. Ma!! stone-1 SET data is higher than more recent EPRI or Utility estimates.
Tacter of 2 to 10 too high (for site specific estimates).
B. Use of hasards curve in FRA study.
(1) Methodology used by BNL appears acceptable to most of the reviewers, however a better justification for weighting scheme is needed. IThis appears to be a conclusion based on site-specific perception of study.) A more appropriate weight ing s' cheme (NUREC-!!52) may not change results.
(11) Methodology recensended by RRAB/DSRO is to esamine the sensitivity of conclusions to a set of hasard cutees.
(iii) Chcice of the upper bound cut-off to acceleration has not been justified, ENL indicates it is japortant.
C. The development of the Cinna curve appears to be in error, small.
C RECOMMENDATION IQ RESOLVI ISSUES Select a family (3 - mean, upper and lower bound) of seismic hasard curves based on RRAB/DSRO comments and establish an uncertainty range for each fragility curve (fragility discussions follow). The data needs to be extrapolated beyond the typical 1.0g limit.
kesults can be presented in a generic manner, given large uncertainties in both hasar ds estimat es and sit e-specific estimat es, and failure differences between elewat ed EVR pool and at-grade PVR pool can be estimated by f ragility.
The integration should be provided as a table /curte versus g for each set of hasard-fragility curves.
ACTION. ENL l
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Contents On BNL Drait Report "Beyond DBAs in Spent Tuel Fools' Cl-82 l
l 2
STENT Jy,11 f,221 FRACILITY l
ENL used two fragility estimates, which were intended to be rep resentative of the spent fuel pool structure. No spent fuel pool fragility was found and an alternative approach was selected.
Cyster Cseek Reactor Building A, = 0.75 Bg = 0.37 BU
- O'38 Zion Aus. Bldg Shear Vall A = 1.1 BR*
U=
. O The fragility curves were weighted and combined to estimate seistic failure-MAJOR COMMENTS. (RRAB/DSRO, EE/DPL-A, EB/DPL-B)
A. The estimated seismic capacity of spent fuel pools are overly conservative.
The structures selected by BNL may not be appropriate based on a review of other data (NUREC/CR-4334), Median g values range from 0.9 to 8.2g.
B. The spent fuel pool liner needs to fail before water is lost.
C. The weighting factors used need justification.
RECOMMENDATLQH Ig RESOLVE ISSUES
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A. A Technical Assistance protect (A-0814) with LLNL has been initiated (April 1,
1987) te provide fragility estimates for spent fuel pools. L;NL wi!! also be-eealbate the spent fuel pool capacity for shipping cask ' rop accidents. A task to develop a working definition of " failure" is includ:d in the project.
Estimated completion date for project in the Tal! 1987.
B.
In the interim, for the BNL final report, it is recommended that a re-review of available fragility data be made to provide an agreeable set of fragility carves. It is proposed that four fragility curves be selected (two for an elevated BVR pool and two for an at-grade PVR pool). A lower bound (fragile, failure a' lower g levels) and an upper bound (better estinate of sp6At fuel pools) fragility curve should be selected. For each pool type, combined with the three hasard curves, sin estimates of failure will be det!!oped. The sedian has ar d cur we r esult s should be present ed as "bes t es tima t e" with upper and lower estimates used to provide a seasure of uncertain both in harard and site.
NURECICR-4293 (January 1986) provides a range of estimated fragility for three foot thick shear walls which conld be reviewed to determine if this data as more representative of spent fuel pools.
ACTION ENL and LLNL
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l Page 3 I
Contents On ENL Draft Report "Beyend DEAs in Spent Fuel Focis" Cl-82 3.
!H:FF f,'~ ff13 If21 MAJ0F COMMENTS- (RRAE/DRSO, FS&EE/DFL-A, DRSS/RE!, PEICSE8EE/DFL-A)
A.
Mcsan error rate nct justified, based on unreviewed data and NRC Handbook, and development of numerical value not present. The BNL developed data is not justated, nor is sensitivity to data shown.
E. A-36 resolution not considered by BNL.
C, Risk does not address fact that there is little cask movement in the andustry at the present time and that there are on'y a few licensed casks available.
ret 0KMENLaT10N IQ RESOLVE ISSUES A. LLNL wi!! evaluate spent fuel pool structural capacity for dropped shipping cask accident.
B. BNL should teview NUREC-0612. "Heary Loads Control at Nuclear Power Plants" and Generic Letter 25-11. " Completion of Phase !! of Control cf Heavy Loads at Hucelar Power Plants," and include discussions of heary loads evaluation, f(
C. Development of risk should include discussion of current shipping rates and potential future rates.
D. A review of poc! designs could be conducted to determine which pools at are risk to cask drop.
ACTICN ENL and LLNL 4
p Fage 4
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l I
Ccasents On ENL Draft Report "Beyond DEAs in Spent Tuel Pocis" GI-82 i
4 TA11131 ASSUMPTIONS MAJOR COMMENTE: (RRAE/DSRO, EDO, REE&IE/DFL-A)
A.
Instantaneous loss of pool is unrealistic E. Loss ef cenfigurationlintegrity of fuel assemblies (for beyond design basis selssic events) not addressed.
C. Events which could damage fuel assemblies, with or without water, are not addressed (energetic missiles, heav} load drop, structural failures).
D. Subject of criticality not addressed.
E. Loss of inventory can occur slowly or in a rapid fashion. In case of seismic events or possibly fires, condition alght esist that deprive the operator of control or surviellance capabilities and were not c>nsidered.
T. The seismic event, more than any other event, will affect the entire plant not only the fuel pool structure. In PRAs, seismicallyigdocedcgredamage frequencies were generally estimated in the range of 10~
to 10 The report
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does not address failures and consequences of either fuel pool or reactor core support systems at Icwer seismic levels. In general, these systems appear more
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vulnerable to seismic failure than the fuel pool structures themselves (lower g L
values).
I EJC.Q]il11NDAT10N J,2 RESOLVE lji m A. LLNL will be essaining fallnre. Objective: Establish a workable definition ci spent fuel pool failure. This will invicte examination of the fuel pool support systems (e.g. make-up capacity), loss of structural integrity and damage to spent fuel pool bt falling asterial within the fuel pool storage building (including dropping of a spent fuel shipping cask).
B. Report should clarify that the assumption is that events can result in loss of pool integrity where loss of water exceeds make-up capacity and that fuel heatup calculation are based on " instantaneous" loss of water, a recognised limitation of the ETUEL cesputer code. For events where the water loss is not espected to be rapid, possible recovery and or more appropriate human f actor data should be included in the discussion.
Issues concerning seismic response of fuel assembl.ies, damage to fuel assemblies and criticality are not part of the current ENL project. An agreement on their treatmentlassessment in the BNL report is needed. A sugesstion is to note issues as areas where additional work may be required.
ACTICN; BNL and LLNL Tage 5
Comments On IIO Draft Report "Beyend DBAs in Spent Tue! Pools" Cl-82
- 5. SF E NT LVJJ, ffdd I NV ENTOF Y JJ.9y ! V A L ENT C O R E S )
The risk profiles was developed based on actual operating histories and spent fuel poc! loading as of Apri! 1987. In Millstenu, the i n v e r. t o r y is aprositatelt three equivalent cores.
MAJOR COMMENTS. (RSIB/DSRO)
A. Has potential inventory been underestimated considering fact that there are facilities now licensed to eventually hold large inventories of spent fuel? A brief review of NUREC-0200 data (Licensed Operating Reactors Status Sumstary Report) indicated a acre typical full fuel pool could hold the equivalent of seven cores. Hatch (a dual unit pool) is now licensed to hold nearly 10 equivalent cores.
B. Tuel rod consolidation could result in even larger inventories.
_ RECOMMENDATIONS IQ RESOLVE ISSUES Current inventories can be rev.ewed to determine "present" risk. A brief look at NURIC-0200 indicates that the current inventory ranges from one to two equivalent cores, with dual units somewhat higher.
Tell fuel inventories should be estimated. Should be possible with current
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calculation with added decay times to discharge batches.
ACTION: INL l
a l
Fage 6
Comments On BNL Draft Report "Beyend DEAs in Spent Tuel Fools
- CI-82 6 TIESION FROCUti INVENTCRY MRICEH1 gfJ E h ;;r.t.siGI. (DRSS/RES, RSIE/CSHO)
A. Application of ORICEN2, as presented in Appendis A of ENL report.
(f) Average Specific power assumption as applied to BVR needs discussion of errors which may be introduced, tai) Statement concerning total calculated radioactivity being the same as In a real fuel batch may needs further evaluation. Radionuclides inventory versus total energy being the same needs to be addressed.
B. Tission product inventory is dependent on burnup and power level. Since plants used by BNL are in general low power plants, inventory may be larger for higher (typical new designs) Mw rated plants. Newer fuel cycles asy result in higher burnup values impacting the fission product inventory.
RECOMMENDAT1QB1 IQ RESOLVE ISSUES ENL should address comments provided concerning ORICEN2 use.
Highest burnup rates used by BNL are 30,000 KVD/MT (BVR) and 46,00f MVD/MT (PVR). EPRI NP-3765 shows recent (post 1980) burnup values are larger. Masimum values 44,000 MVDIMT (BVR) and 55,000 MVD/MT (PVR).
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Issue should be addressed and, if possible, assesse'.in terms of potential larger fission product inventories. Not actually in BNL present scope, may require additional work.
ACTION. BNL Page 7
9 Cozzents On SNL Draft Report *Beyond DBAs in Spent Tuel Fools" Cl-22
- 7. F SSION FRODUCT REitAft Q:J E MATRf!
Two areas of concern:
(1) Anount of fuel falled by fire (2) Astunt of fission products released fres fuel matris due to heatup fo!!owing fire.
MA)Q1 CONCERNS: (DRSSIRES)
A. The dynamics of the fire should be considered. The Zircaloy may burn so quickly that the fuel pellets of the cold fuel may not have time to heat up t o the temperatures tequired to completely vaporise the volatile radionuclides.
B. Fefect ventilation versus imperfect ventilation cases appear to need additional wording.
RIC0 EMENDATIONS IQ RESOLVE ISSVES INL should reconsider the fire propagation and dynamics. Results should indicate how much fuel will born as a result of sufficient decay heat and how much will burn given a rubble bed on the pool floor.
A simplified heat transf er analysis may be needed to see how f ast and how hot the fuel can get for a Zircator fire.
w.
ACTION: ENL l
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i l
Contents On ENL Dr af t Repor t "Beyund.DEAs in Spent Tuel Fools" GI-82
- 8. T I E R12E P R ODt'CT N E L E A S E IQ 1,7M0 c P H E F E i
Mll COPMENT!. (K!E 8 KSIE/DSRO)
A. Fossible retention of radionuclides on structures not considered.
B. No distinction made for non-selstic events.
RECOMMENDATIONS 123 RESOLUTION 21 ISSUES EKL sh:uld consider possible retention on structures. May be justifiatic for EVE p o o l s inside' reactor building.
ACTJQB. ENL I
e l
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Coas,ents On EHL Draft Report "Beyond DBAs in Spent Tuel Fools" C!-62 7.
Col 4 SEQUENCES (CKACI SEI UU HA ;C F. C C N *, E nli). (RRAE/DSRC, DESS/RES, EDO)
A. CKA 2 data concerning timings, height and energy of release are not prcvided.
B. Some radionuclides listing in source ters tables are not directly accounted for in CRAC.
C. Consequences for Cases 3 and 4 not provided.
D. It is not appropriate to use NUREC-1150 data to compare with spent fuel pool scridents, 1150 is plant specific study.
E. Should mere than one site population distribution be considered, and is the conditional interdiction area different for different sites (based on populatlon)?
l RECOP&lGDATIONS IE RESOLUTION g IEEUES Provide missing information on releases, Address source tera question.
Consider additional CRAC cases to address sensitivities?
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ACTION, BNL j
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.Cossents On ENL Draft F.epert "Beyond DEAs in Spent fuel Fec!s" C!.82 10 M F.tDUCT!Cli ME A!URES r..,,,...7'.i (FEICSEIDFL-B)
Consideration of risk teduction measures are superficial.
RECOMMENDATIONS 12 RESOLVE ISSUts I
The BNL project objecties was to identify possible measures based on potential cost benefit, no ealuelimpact assessment was requested. Report should be clarsfied to indicate that BNL has not attempted a detailed ealue/ impact assessment.
ASIl2.8 : ENL Page 11
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Cosser.ts On BNL Draft Repert "Beyend DEAs in Spent Tuel Pools" Cl-82
- 11. OTFER !!!VIS 1DEP~* TIED DURINO REVIEV MAJOR CON:EPNS. (RRAE/DSRO, DRSS/RES, RSIE/DSRO)
A. Approach is not systematic enough to assure that all aspects of Generic
!ssue 82 are covered.
B. Report uses several bounding assumptions and conservative boundary condition in several areas. Report is a reasonable screening study in that it conservative bounds the probles.
C. The data presented can not be judged as being best estimate, point estimate, conservative. Uncertainties are not, in general, addressed. It is not possible to tell if data is generic or plant specific, probably neither.
BLOOMMENDATION) IQ RESOLVE ISSUES The stated objective of the report should coincide with the objective as described in the Technical Assistance project work statement. The report is not intended to be an " integrated risk assessment" of spent fuel pools Ciren the possibility of Zir caloy fires, BNL was to re-evaluate the likelihood of draining a spent fuel pool and assess the risk associated with a drained pool.
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The report needs to be modified to provide an assessment of values selected by BNL which are not supported. For example, VASH-1400 values and HUREC-0933 values are used solely because they asist, without qualification or assessment.
BNL needs to qualify these data.
To the entent practical, an assessment of uncertainty is needed. Human error r at es ne ed es amina t ion.The amount of fuel involved in a release needs more i
attention.
l AITl28. ENL l
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