ML20214G562

Requests Technical Assistance in Evaluation of Util 740809 Submittal Re drywell-wetwell Leakage.Ser Section 5.4 Identifying Item as post-CP Review Item & Pertinent Section of Summary of 731017-18 Meeting Encl

ML20214G562
Person / Time
Site:	Columbia
Issue date:	10/07/1974
From:	Deyoung R US ATOMIC ENERGY COMMISSION (AEC)
To:	Schroeder F US ATOMIC ENERGY COMMISSION (AEC)
References
CON-WNP-0058, CON-WNP-58 NUDOCS 8605220280
Download: ML20214G562 (4)

Text

{{#Wiki_filter:_ t OCT 7 1974 DISTRIBUTION: Docket Fil E-- P SVarga LWR l-2 File DEisenhut WMcDonald RCDeyoung RWKlecker LWR l-2:74-14 RTedesco TR AD GLainas TR BC Docket No. 50-397 MErnst (for scheduling) J0rndoff PM. F. Schroeder, Acting Deputy Director for Technical Review, L TECHNICAL ASSISTANCE REQUEST PLANT: WPPSS Nuclear Project No. 2 (formerly Hanford-2) STATUS: Post-CP Review BRANCll: LWR 1-2 PROJECT MANAGER: John Orndoff TR BRANCHES INVOLVED: Containment Systeco DATE REQUIREb: November 8, 1974

REFERENCE:

Letter from J. J. Stein, Washington Public Power Supply System to A. Giambusso dated August 9, 1974 with attached technical report (WPPSS 74-2-R5, Dry-well to Wetwell Leakage Studf ) DESCRIPTION OF REQUEST: Technical assistance is requested to eva*.cate the submittal by WPPSS on drywell-wetwell leakage. This is a post-CP review item which is identified in Section 5.4 of the SER. This section of the SEP is provided in Attachment 1 for your convenience. Included also in this attach-ment is the pertinent section from the Summary of the Ot.tober 17-18, 1973 neeting (dated November 21, 1973), in which the subject CP item is discussed. Blain D MR R R. C. DeYoung / g/ Assistant Director for Light Uster Reactors, Croup 1 Directorate of Licensing cc: R. Tedesco C. Lainas

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e g ATTACID ENT 1 EXCERPT FROM FA' FORD NO. 2 SER

 %4   Dry *,; ell to Sunaression Chamber Leckage The dry. sell deck vill be designed to reduce the likelihood of typm of blowdem steam from the drywell dirc:tly ir.to the air chacher above the suppression pool. Short circuiting of the pool could affect the pressure suppression capability of the containnent systea. Several patential bypass areas have been identified. These are:    the peripheral joint of the drywell floor to containment wall, joints betwee'n the downco=ers and the drywell floor, and cracks in the reinforced coacrete iloor. In k::endeent No. 6 the applicant stated that he is presently developing his seal design for the peri-pheral joint between the drywell floor to the containment. It cenaists of a circular segment of steel pipe, forced to an anaular diameter of approxinately 85 feet which is capable of acco=:odating t.he naxint: 2 anticipated. vertical and radial dif ferential thermal novements and resisting the maximun anticipated differential pressure in an clantic naaner.      Since this seal is sensicive to differential grosa latera) and torsional covecents, sheer lugs between the drywell floor and the containment vessel will be provided to assure that they wove in unison at the tire of a seismic occurrance. Thue shear lugs par ai.e radial and vertical dif ferential covenents, but restrict torsional and horizontally lateral displner.+nts henteen the floor and the contain ent vessel. The do:mccur vents that penetrate t ht- drywa) floor     ;il be velded to a platt thst 7131 he ed edJ d in the

1 ccatar of the drywell floor slab. The applicant tete 1 in /s r' ..r r No. 3 2 that the dr- vell floor will be se. sled u.ith . plast it coat in-that has clastic propertics, On the basis of our review of the dry-well deck design, we have concluded that the potential for dock bypass leakage has been sil ;nificantly reduced. In order to preclude excessive upward dif ferential pressure on tha drywell deck as a result of drywell cooling fcllowing a blowdewn, vacuum relief valves are provided on the downtoners. During a blc.v-down the vacuum relief valves prevent direct bypass flow iron the dryvell to the suppression pool vapor space. To idnicize the potea-tial for a vacuun valva being stuck open cad thereby providing dryuell to wetwell Icak paths we require, and in Acendment No. 9 the applicant has agreed to provide, testabic vacuen valves with redun-dent position indicators for each valve. These valves will be tested at a frequency equivalent to the testing frequency for ECCS valves. To detcet other possible Icak paths the applicant has agreed to conduct dryuell deck leakage tests at each operating cycle. In addition, prior to startup, the applicant uill test the drywell f.1r;or to its design differential pressure of 25 psi by sealing the down-cenerr, and pressurizing. We will revicu the detailed test progran during the operating license revleu to assure that an acceptable progran 10 develeped. We have concluded that as a result of the propeacd design nodifi-cations to the vaccur breakers an? the surveillance pro; ran proposed for rhe dryv=11 dech and the vacua breakert the patential for hypas ,

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6 1.eebge L~s been reduced. I!owver, in Ame,drent' No. 12 the applice.t h:u :. greed to study additional means (i.e. , scaller vacuu.a breakers or ndditional contain:ient spray) to citigate the consequence or nini :ine the potentici for bypass leakage. EXCERPT FRO'! SUFDLARY OF OCTOBER 17-18, 1974 MEETIf{G _D:vuell to Uetuell Leakage including vacuu Breaker Design The applicant and the representatives of Eurns and Roe presented a discussion of potential leak sources betueen the dryuell and uetuell, the syste= to be used to detect these leaks aad the procedures to be used to operate the leak detection system. potential leak sources uhich were discussed in greatest detail and which received the most discussion included the vacuum breaker valve design, te concrete floor scalant and the netal peripheral seal of the dryvell floorh Uith regard to the vacuun breaker valves, it was pointed cut by the staff that the reliability of these valves is low and that the accuracy and reliability of the valve pas.ition indicating switches should be carefully considered. The applicant stated that he vas examining suitable floor sealers even though ha did not expect dryuell to uetuell leakage through the ccncrete floor to be a prcblem. The details of the floor to contain.wnt real were presented. *lhe seal ir essentially a sectioned stainless pipe attache ' to carbca steel seppert plates which are then attached to the floar and the contoimm nt vess.l. Yhe seal allo.:s dif ferential horizontal and vert icle novanant., u tm r draint y and inspectica of seal velds. A report deal ng '. iti Gy, 11 t o uctuell 1cchage is scheduled for submittal by the applicmt. turing Ap r il 1974. I

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