ML20129C344

Forwards Addl Info Re Leak Testing of Valve MO-8812,per 850613 Request.Min Test Pressure Reduced to 33.6 Psig

ML20129C344
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	07/12/1985
From:	Withers B PORTLAND GENERAL ELECTRIC CO.
To:	Butcher E Office of Nuclear Reactor Regulation
References
TAC-56813, NUDOCS 8507160161
Download: ML20129C344 (3)

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Ib10 wem vre Pre,+,4 July 12, 1985 Trojan Nuclear Plant Docket 50-344 Licenso NPF-1 Director of Nuclear Reactor Rot,ulation ATTN! Mr. E. J. Butcher, Jr., Aating Chief Operating Roactors Branch No. 3 DLylslon of Licensing U.S. Nuclear Regulatory Commission Washington DC 20555 Dear Mr. Butchort Volvo HO-8812 Test Progra,n1 In responso to your letter of June 13, 1985, the additional information requested concerning leak testin& of valvo MO-8812 to provided in the attachment. We have revised the minimum test pressure to 33.6 pois.

Sincoroly.

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Bart D. Withers Vice Prostdont Nuclone Attachment c Mr. Lynn Frank, Director State of Oregon Department of Knorgy 0'307160161 OD071P PDH ADOCK 0D000:14 4 p Pl)H I'pl Q

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Trojan Nuclear plant Mr. E. J. Butcher Docket 50-344 July 12, 1985 License NFF-1 Page 1 of 2 NRC Request

1. Regarding your request to reduce the valve test pressure from 60 paid to 22.5 paid, we note this request is based on the estimated contain-

. ment pressure at the beginning of the recirculation phase following a LOCA, plus an allowance of 0.5 psi for calculational uncertainties.

According to the Trojan FSAR (page 6.3-22), however, recirculation is automatically initiated when the Refueling Water Storage Tank (WST) reaches its low-level setpoint corresponding to 145,000 gallons of water remaining in the RWST. In addition, FSAR Table 6.3-4 indicates the minimum capacity of the RWST is 420,000 gallons and FSAR page 6.3-22 indicates the runout flow of the acc8 is 19,000 syn.

Based on these numbers, it appears the recirculation phase could start as early as 14.9 minutes (894 seconds) after the begine.ng of the LOCA. Based on initiation of recirculation at this time, FSAR Figure 6.2-91 indicates the Containment pressure would be about 33 peig instead of the 22 paid you have proposed. Based on these considerations, please change your proposed basic test pressure (not including allowance for uncertainties) to 33 psid or explain why this base test pressure is not appropriate and fully justify some other test. pressure.

Response to Itos 1 Civen the premise that the test pressure for NO-8412 should be the pressure existing at the earliest possible time tecirculation could begin, further analysis has been performed as discussed below.

Switchover from injection to recirculation is auto-initiated only from the standpoint that the WR pumps are stopped automatically at the low-level setpoint in the NWST. The remaining steps are performed manually.

The low-level setpoint in the WST corresponds to 223,000 gallons of water remaining in the tank. This represents 145,000 gallons of usable water plus 78,000 sellons of unusable water remaining in the WST (FSAR l

pages 6.3-22 and -23). The minimum WST capacity is 428,000 gallons and the acc8 runout flow is 19.000 spm. Therefore, the WST low-level setpoint could be reached in 10.8 minutes (647 seconds).

Because No-8812 is closed early in the switchover sequence from injection to recirculation, no additional delay for onset of recirculation due to valve stroke time was considered, which is conservative. Therefore, using Figure 6.2-91 at T = 647 seconde, the containment pressure would be 39 pels.

Another consideration which reduces the test pressure for NO-8812 is the ditfarence in elevational head between the WST and containment at the

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Trojan Nuclear Plant Mr. E. J. Butcher Docket 50-344 July 12, 1985 License NPF-1 Page 2 of 2 start of recirculation. The low-level setpoint in the RWST is 64' 5" MSL. The Containment sump water level is about 51' 0" MSL. This differential head reduces the pressure across NO-8812 by 6.4 psi or a total differential pressure of 32.6 psid.

NRC Request

2. Regarding the uncertainty allowance of 0.5 psig you have proposed for this pressure test value, we note this represents an uncertainty of about 2.5 percent. We doubt the ability of the present state-of-the-art to predict Containment pressures to this accuracy. We also note from Figure 6.2-91 that at a time of 1,000 seconds into the postu-lated accident, the descending curve has its steepest slope and thus its greatest uncertainty. It would appear to be prudent engineering to have the percentage uncertainty in the test value comparable to the percentage of uncertainty in the calculation. Please address this concern in your response and amend your proposal appropriately.

ggsponse to Item 2 The uncertainties associated with the calculation used to generate Figure 6.2-91 are already included in the figure. The only remaining uncertainty is in reading Figure 6.2-91. We are confident of the ensi-neering judgement which assumed an uncertainty of 0.5 psig. However, for further conservatism, we will assume an uncertainty of 1.0 psig.

Therefore, we propose a revised minimum test pressure for MO-8812 of 33.6 psig.

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