ML19343C164

Responds to ACRS 800918 Request for Comment on B Cohen Concerns Re Refueling Water Storage Tank Adequacy.Decay Heat Removal Alternatives Recommended

ML19343C164
Person / Time
Site:	Palisades
Issue date:	11/09/1980
From:	Burns R AFFILIATION NOT ASSIGNED
To:	Okrent D Advisory Committee on Reactor Safeguards
References
ACRS-CT-1293, NUDOCS 8102180812
Download: ML19343C164 (2)

Text

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• p. O. Box 1493 Santa Fe, NM 67501 November 9, 1980 iN w,

Dr. David Okrent, Member , .-F L' p 53 Advisory Committee en Reactor Safeguards U. S. Nuclear Regulatory Commission

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n COMMENT 5 REGARDING CONCERN 5 OF S. COHEN ABOUT REFUELIN # 't) i UATER STORAGE TANK (RUST) ADEOUACY, AND Resp 0NSES. BY

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NRR and RES.

Oear Dr. Okrent*

This is in res=onse to your request for my comments on this subject as expressed in a September Although la, 1980 letter to as R. 3. Budnitz me from C. R. Quittschreiber.

correctly pointec out in his memo of June 11, 1980 to R. F. Fraley that RUST unavailability is a minor contributor to failure of containment sprays and emergency core cooling systems (ECCS), I believe it is prudent to search operating histcry for precursor events to RUST unavailability and to consider whether simple alternatives to the RUST exist.

Further, simultaneous seismically-induced LOCA and RUST rupture or supply line break is probably an important contributer to the likelihood of RUST unavailability during a LOCA, and this point may not have received adequate attention in UASH-1400 cr in the responses of Mr. Budnitz, who referenced UASH-14CD, or of H. R. Denton, who expressed his intuition with regard to probabilities.

The RUST is continucusly monitored in the control room, and reactor shutdcun is required in the event of RUST inadequacy.

However, several elements in addition to water level, temperature and boration are required to assure suction for heat removal equipment: (1) supply lines must be unobstructed, (2) valves must be properly aligned and oper-ational, and (3) RUST level indication must be reliable.

A search of licensee event reports (LCRs) should be made for instances of RUST supply line freezing, stuck valves, or problems with RUST instrumentation. Within the next few days I will make such a search and will report any significant findings to you immediately. In any case, these aspects of heat removal reliability should be carefully reviewed by each licensee.

It may be worthwhile to consider the engineering aspects of some 11mple alternatives to the RUST for decay heat removal, and I propose three possibilities. First, a large volume Since the of water could be left in the containment sump.

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Dr. D. Gkrent November 9, 19EC e

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vclume would have to be considerably less than thet normally centained in the RUST, a design basis would need to be established to finc the minimum volume needed in the event cf RUST unavailacility. Second, a backup RUST could be placed insice centainment. In the event of seismically-induced rupture of tne backup RUST, water woulc then spill into the centainnent sum;. Uith this configuration it may be advantageous to align all decay heat removal suction to this tank in the event of a LOCA, and to continuously refill the tank from the containment sump and the original RCST. (hese first tuc RUST alternatives would also decrease the likelihood of trying to take suction from a dry sump, which cculd occur due to too early switching to sump recirculation and could result in cump damage. (Concern over this possibility was recent'y expressed by Westing-hcuse and reported in several LERs.) Third, pipe and valve alignment to draw on other water sources suen as a lake, river, cr ocean may be possible.

The re-examination of the risk contribution from RUST unavailaoility should be part of the IREP studies, as suggested by Mr. Denten. Such analyses uculd help to icen tify whetner significant causes for concern exist, on a clant-scecific basis. Seismic contributions should be addressec specifically.

I hope these comments vill be useful to you. I intent to supply comments as soon as I can regarding the NRC staff re;crts on interfacing-system LOCA and Indian Point and regarding the IREP scheoule. If you wish te discuss this matter further, please feel free to call me at S43-7322/FTS, 5:5-557-7322/ office or 505-958-3451/ hone.

Sincerely,

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Robert D. Burns III R E C E e g dCRS Consultant

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