ML20214H931

Responds to 870428 Mailgram Demanding Proof Prior to Restart That Stated Circumstances,Including Valve Failure Permitting Loss of Coolant from Reactor Core Through Failed Valve, Cannot Occur

ML20214H931
Person / Time
Site:	Pilgrim
Issue date:	05/20/1987
From:	Varga S Office of Nuclear Reactor Regulation
To:	Piercebjorklun AFFILIATION NOT ASSIGNED
Shared Package
ML20214H933	List: ML20214H931 ML20214H942
References
NUDOCS 8705270545
Download: ML20214H931 (2)

Text

- _ _ __. __ . _ _ _ _ _ _ _ .. _ _ _ _ - - _ . _ _ _ _ . _ . .

! . May 20. 1987

. ~ ,

Ms. Patricia Pierce-Bjorklund 15 Spring Street Essex, Massachuetts 01929

, [l )

Dear Ms. Pierce-Bjorklund:

Your mailgram of April 28, 1987 to Chainnan Zech was referred to me for

response.

Before addressing the issues raised in your mailgram, I need to remove any confusion about Pilgrim and a low power license. Pilgrim currently holds a i full power operating license that was issued September 15, 1972. Therefore, 1 I am assuming your telegraphic referral to Pilgrim is in regards to restart of the plant.

j Below I have repeated each of your' issues and my response:

Issue i

f We demand proof prior to the issuance of low power license to Seabrook ,

) or Pilgtim Nuclear Stations that the following circumstances cannot 4

occur.

1. Valve failure permitting loss of coolant from the reactor core '

through the failed valve so that emergency coolant entering the "

cooler would not also exit through the same failed valve thereby leaving the core without coolant.

Response 4

As a part of the licensing bases for nuclear power plants, licensees must perform safety analyses to dcmonstrate that the emergency core cooling systems conform to the requirements of 10 CFR 50.46 and Appendix X to 10 CFR 50 for postulated loss-of-coolant accidents (LOCAs). These LOCA analyses are performed for a spectrum of postulated break sizes at the worst location in the primary system and directly account for possible loss of emergency core cooling through the break.

In addition, single failure analyses are performed for the emergency core cooling systems to demonstrate that adequate core cooling will be provided assuming a single active valve failure in these systems.

Since the staff has concluded in Section 15.6.5 of the Seabrook Safety Evaluation Report dated March 1983, and in Section 9 'of the Pilgrim Safety Evaluation dated August 1971, that the emergency core cooling i systems for these two plants meet the requirements of 10 CFR 50.46, there is no single active valve failure which would prevent the core from being adequately cooled in the event of a-LOCA.

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8705270545 870520 PDR ADOCK 05000293

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. ~ e Ms. Partricia Pierce-Bjorklund May 20, 1987 Issue

2. Increase in reactor core temperature causing the Zirconium casings on uranium rods to swell thereby blocking passages .

between rods and preventing emergency core coolant from '

circulating thereby resulting in uncontrolable (sic) chain reaction and meltdown.

Response '

The staff recognizes that swelling of the Zirconium casings on the fuel rods may cccur during a LOCA and result in blockage of the coolant channels. Section B of Appendix K to 10 CFR 50 requires that the analytical models used to perform LOCA analyses account for the effects of fuel rod swelling and rupture. In addition, 10 CFR 50.46(b)(41 j requires that the core geometry remain amenable to cooling following a LOCA. Therefore, since the LOCA analyses for the'Seabrook and Pilgrim Nuclear Stations demonstrate conformance to the requirements of 10 CFR 50.46, swelling of the fuel rods will not prevent the emergency core coolant from providing adequate core cooling in the event of a LOCA.

J Sincerely,

-._.x ...._a i

• ' ** . = mm gg Steven A. Varga, Director Division of Reactor Projects I/II Office of Nuclear Reactor Regulation DISTRIBUTION Docket Files NRC PDR LPDR VNerses Murley/Snf ezek FMiraglia RStarostecki JBlaha JFunches DMossburg NRR Yellow Ticket 879131 PBaker(2)

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