ML20210T604
| ML20210T604 | |
| Person / Time | |
|---|---|
| Issue date: | 08/26/1986 |
| From: | Ernst M NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Knapik M INSIDE N.R.C. (MCGRAW-HILL PUBLICATION) |
| Shared Package | |
| ML20210T528 | List: |
| References | |
| FOIA-87-10, RTR-NUREG-1150 NUDOCS 8702180240 | |
| Download: ML20210T604 (2) | |
Text
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%' Vettit D ET ATES j . NUCLE:AM REGULATORY CQe4AtStt0N .
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Avgest 26,1H6 : .
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t Letter to the Editar l
Inside NRC -
Suite 1200 1120 Vermont Ave.. N. W.
Vashington. 8. C. 20005
,, - Attn: Mr. Michss1 Knapik Chief Editor O
Dear Sir:
Because of scoewhat incomplete inforr.ation published in the medit regarding the u pcssible vulnerability of Mark 1 BWR contairnents it tore melt accidents I -
i agreed to an in-de>th interview with 'Irside NRC' (ref. page 1 article by '
Brian Jorden. 'NUREG.1150 Will Question Capability of Mark i Contatteents,
' August 18,1%6). However, this oce-hour interview resulted in surnary
. statements that still are not sufficiently on-the. mark. I respectfully request -
that, because of the importance of this subject, this letter of clarification be
. gb11shed in e prw.inent spot in the r. ext issue of 'Inside NRC.'
To clarify the record, the following points should be made:.
- 1. The NRC study is not yet cceplete; therefore, it is inappropriate to cieracter13e what the stv# "will conclude.' The technical issues are very compler and still under study. Also, because of the uncertainties, even the final Study conclusions will not provide a precise, definitive answer to the' questions of risk or the likelihood of survivability of the Pesch Bottom contairment given a severe core donage accident.
, 2. In ey discussion of the efficacy of venting the Peach Bettom contairment, I was very careful to point out that our assessment was that procedures and
- plant design existing at the time of the Jstud would make it unifkaly to be
- able to vent the contaEent succelifuTTy under station blackout conditlons, Alch is the Peach Bottom dominant accident sequence identified in our study. However, I also stressed several times that this would be a very plant-sMcific conclusion, and changes to the Peach Bottom procedures and design could significantly improve the capability to vert successfully under such circes tances. This is ir contrast to the ecnclusions in *!nside Rec
which state that venting efforts at Peach Bottom *would most certainly fail," but that other Mark I's might be okay. It should be recognized ,
though that such changes would need to be supported by engineering analysis; and, quantity as of a matter of policy,le radioactive nob gases would still be released to theit would envirofeent.
. 3. There are substantial uncertainties in the assessment of containment 4 integrity and risk. Some of the inportant uncertainties with regard to Mark I contairwants include: the location of the containnent failure in the event:af overpressuritation; the likelihood of successful Nenting to p reclude . suc h ove rp re s s uriza tion ; the potential for direct corium attack on the drprell containnent liner, which would result in suopression pool 8702180240 870211 /~dI A /C PDR FOIA - ---~
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lypan buildingand the potential for fiss'en prodact.retentien Ja the teector '
drywell o,rifthe theuppression containment pool.fared is the lower portion of either the '
I carefully stated in the intaryfew that '
our preliminary risults for Peac' totters show that if the contaltsent fails .
such as to bypess the suppressio pool, and M the reactor bwlidinj decontanication factor is ar411, 7 then the trfertil Peach Bottom com4fane -
perforv4nce would be about as est miTed in WAW1400.
represent the upper range of a rsthee wids uncertainty band.However, this would This is in contrast to.the staterents in "Irstde ARC' which were "a that:
nuriber of plants do not meet the perforr.an:t guideline in the Comission's r edopted~5aTely goal policy"; and 'the overall risk of a large release .
remains signiffcant g_iv_en 1_uc_h a M (mphasis added). probability of contaireant failure" cceplex technical issuet causing themConsidering Irt w de etnge .of unc make the type of explicit findings quo,ted in Inside ERC.it it not appropri
- 4. Mnally
' allow ro,lten fuel and other high*j radioactive rateri 1
1 drain substantively from the incorrect. drywe11 through vt t lines to the wetwall' is technic The mo' ten fuel would rtesin in the dry well.
However, core-concrete radioactivereactions in aerosols the d- 4M nor.condensible gases produced by thro 1Jgh the suppression pool rest. ting in the deposition of radioactive wetwell. Yentingmaterials in the tool wat4r and increasing pressures in serve both to lower (the wetwell) s*. tMs timesuccessfull would if done pressure in v.e wetwell f and thus the drywell ,and provide in their passage for removal through of the most of t'e radioactive sus:aession pool. materials from the aerosols Radioactive noble gases would.not be removed, however, a'f thus would be released to the atm .
believe the complexity of the technittI hope that this helps citrify . I the i analyses and the inherent uncertainties I
nst rewits. be properly charactertred in ar.y cresentation of preliminary NURIG-115 t
that M'JMG-1150 will estir. ate risk us'r.s rangesuesrathe
- in order the probabilistic to reflect risk assessments properly thear.
- larst degree of uncertainty inherent in reasons for those uncertainties. tc focus titention on the important
, a alc a L. Ernst. Director Division of Reactor System Safety Offics' of Nuclear Regulatory Aesearch U. S. Muclear Regulatcry Conafssfon i
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