ML20235D997
| ML20235D997 | |
| Person / Time | |
|---|---|
| Issue date: | 08/26/1986 |
| From: | Glynn J NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Burdick G NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML20235D912 | List: |
| References | |
| FOIA-87-10, RTR-NUREG-1150 NUDOCS 8707100377 | |
| Download: ML20235D997 (3) | |
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AUG 16 BBS MEMORANDUM FOR: Gary Burdick, Chief Risk Anelysis Branch, DRSS l FROM: James C. Glynn, Section Leader Application Development Section Risk Inalysis Branch, DRSS, RES
SUBJECT:
A PERSPECTIVE ON THE VENTING ISSUE FOR PRESENT DAY l BWR-MARK-1 PLANTS In view of the considerable attention being given to the belief that certain j minor modifications to existing plant design / procedures could establish the venting option es an " acceptable way" to reduce the overall public risk from severe accidents, there are a number of considerations that need to be kept in l
mind in this regard and es such are being brought to management's attention:
(1) The INEL/BCL venting study for Peach Bottom done under contract to our branch is a limited feasibility study that is now under review by RES and l NRR. As you know, this study only provided estimates of sequence success probability for human actions for TC and TB. I'm concerned that the human action element may have been so over emphasized that some people may have jumped to inappropriate conclusions; namely, that since small plant changes to equipment / procedures could well increase these human action likelihood estimates, that a similar conclusion applies to the likelihood of overell fenting success. Please be advised that this latter conclusion is not justified, since successful venting not only depends on the human actions investigated, but would depend also in great measure on the results of a yet-to-be completed engineering design analysis. In such an enalysis, all of the assumptions and judgments on which the INEL likelihood velues were conditionalized would have to be appropriately treated in the context of accepteble engineering practices. Note:
INEL/BCL study did not address the TW sequence which has of ten been referred to as the secuence most likely to be mitigated by venting; however, this sequence for Peach Bottom still leaves open, in my mind, many engineering questions.
(2) I have provided INEL with my corr'ents on their report. Among many suggestions, I've esked that the final report emphasize the important fett that this study was an engineering feasibility study to judge whether venting of the existing Peach Bottom plant is possible and where there may be problems that eventually would have to be addressed before one could conclude that e vieble system eristed for venting the conteinmer.t. INEL's study accomplished these objectives; however, I'm suggesting that the report male it very cleer that: (i) tht> study was only a feasibility study with some quantitative emphasis on human reliability actions, (ii) significant engineering eralysis end date are needed before it's possible Fo z.A - ? 7-/6 8707100377 870701 PDR FOIA 1 TYE87-10 PDR l
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2 to take a position that venting, even with some modest changes to existing conditions, cro reasonably be expected to contribute to overall plant safety, and (iii) unless Peach Bottom's containment design performance could be shown to effectively extend beyond its design tapacity, and this condition then accepted as a legitimate basis o' regulatory approval, venting will not be an acceptable option.
(3) NUREG-1150 should be very explicit with' regard to its discussion of venting such that NRC decisionmakers are fully informed of the subtleties inherent in this complex problem. For example, questions such as--should containments be vented?, if so, when?, should they te re-isolate?--need to be addressed.
(4) The PRISIM inspection system for Peach Bottom will probably not address venting as a possible option. The reason clearly being that we have no basis for judging the efficacy of the proposed system vis-a-vis the rest of the plant systems for which there have bee- engineering analyses performed. Accordingly, to give credit to the iosa of venting with our-present state of knowledge is in my opinion n:t justifiable. This decision is consistent with our treatment of recovery actions not covered by E0Ps for the AND-1 PRISIM system.
In the attachment to this memorandum, I have identified several areas for those sequences addressed in the INEL report for which the ateve discussed concerns of mine are a direct consequence, if you agree with w*at I've stated in this memorandum, i.e., not sufficient information to judge w*at plant modifications would be needed to mate venting a viable and useful optien, I think it would be appropriate for you to see to it that the others in RES management are alst on board, if you disagree with my views as stated, I certainly need to know so that we can develop a cohesive position on the questicn of venting existing MARK-1 containments.
Qd ~
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James C. Glynn, Section Leader Application Development Section Risk Analysis Branch, DRSS, RES
Attachment:
As stated l M. Leonard, BCL l cc: D. Ross l
M. Ernst H. Reilly, INEL J. Murphy P. Mcdonald, INEL B. Morris Application Development Section Mb D. Batt, INEL M. Leonerd. BCL
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- ENCLOSURE 1 Venting Assumptions Needing Verification TC-la TC-lb TC-2 o Operator is successful o Same as TC-la except o Operator cannot in tripping re-circ pump, operator does not achieve any of the lowering level and depress RCS. actions in TC-la, depress. RCS thereby resulting ir core melt before cont.
failure.
--Power level is correctly --Basically the same as --Several of the problers calculated to be lit for TC-la stated for TC-la
--Containment will maintain --Rupture of RCS will not its integrity up to 2X result in direct cont.
Des. Press, failure.
--Pool dynamic loads will --MARCH code is accurate not affect torus integrity to predict RCS rupture
--Analysis of steam / air flow within 20 minutes of thru valves is accurate given initiation of venting, quality / sonic vel. consider- --Plant performance durin; venting of ignited H, ations #
--Existing steam flow will not gases create other plant problems TB (Blackout)
--Rupture of RCS will not directly feil cont.
--Determination of o Accurate pool df
--Effect of exiting H2 gases on bldg. integrity
--Containment integrity for T, P conditions beyond design
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