ML20213E057
| ML20213E057 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 03/02/1982 |
| From: | Speis T Office of Nuclear Reactor Regulation |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| CON-WNP-0481, CON-WNP-481 NUDOCS 8203120362 | |
| Download: ML20213E057 (4) | |
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R. Tedesco, Assistant Director for LicensinC, DL Fno'1:
T. Speis, Assistant Director for Reactor Saf ety, DSI SUCJ ECT:
REVISIOi! TO TIIE DRAFT SAFETY EVALUf.TIOfl REPORT FOR t!ASilIf!GTON PUOLIC P0llER SUPPLY SYSTErl (WPPSS), l'UCLEAR PROJECT !10. 2
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v The Containaent Systems Cranch input for the Safety 'Fdaluati&DJeport' (CER) on the 1:ashington Public Power Supply System, t;uclear FrideitJh.J'2 (!!ilP-2) t that was forwarded to you by memorandum dated February 11,1952 inadve rtent Ly did not identify the vacuum breaker valve performance curing and af ter the chugging phase of a loss-of-coolant accident as an outstanding issue.
This issue, which was raised by the ACRS during the April 28-29,1981 Fluid Dynamics Subconnittee neeting, relates to the potential for steas.. bypass from a stuck open wetwell-to-dryweLL vacuu.a breaker. Thc-staf f requested the l ark II owners to address the concern.
In a letter dated July 8,1981, the flark II owners indicated that a progran to determine the valve capability during a chugging event was being developed.
The tilo-2 applicant also indicated during a July 31, 1901 uccting that a study was underway to detercine if plant design modifications uere needed to resolve the ACRS concern.
Upon co.Npletion of this study by the I;crk II owners, we wiLL report our find-ings regarding this issue in a supplement to tnis SER.
Enclosed is a revision to our SER input to identify this issue as needing ad-ditional infomation.
Thenis P. Speis, Assistant Director for Reactor Safety Division of Systens Integration
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REVISION TO THE CSB INPUT SAFETY EVALUATION REPORT WASHINGTON PUBLIC POWER SUPPLY SYSTEM, NUCLEAR PROJECT NO. 2 CONTAINMENT SYSTEMS BRANCH 1.
Insert the fotLowing at the end of subsection 6.2.1.8.f, page 6-30 of the Containment Systems Branch portion of the SER.
Concern regarding the potential pool bypass from stuck open wetweLL-to-dryweLL vacuum breaker was expressed by the ACRS during t he Ap ri l 28-29, 1981 Fluid Dynamics Subcommittee meeting.
This concern stems from the fact that fotLowing the onset of a loss-of-coolant accident and at about 20 seconds into the transient, the chugging phenomenon takes place.
This rapid steam condensation wilL cause repeated and strong dynamic underpressure conditions in the vent pipe for about 5 mitLiseconds.
Due to this largeap, the vacuum breaker may open.
i Since the chugging phenomenon is repeated every two seconds i
i on the average, the vacuum breaker may be called upon to function in a cyclic manner during these intermittent steam condensation events.
Failure of a vacuum breaker to close during this time period could result in steam bypass of the I
pool, thus jeopardizing the integrity of the containment.
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During a meeting held with representatives of the Mark II Owners Group in Bethesda, Maryland on July 31, 1981, we were informed that the Mark II owners that have vacuum breakers attached to the vent pipe are in the process of conducting a joint qua li fi cat i on test program to demonstrate the operability of the vacuum breaker under this intermittent steam condensation loading.
The WNP-2 applicant has indicated that they are participating in th'is qualification program and that they are.also considering possible design modifications to resolve the ACRS concern.
We will report our findings regarding this issue in a supplement to this SER after receipt of a report on this subject by the applicant.
2.
Insert the follow;ng item on page 6-33 of our draft SER:
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3.
Wetwell-to-drywell vacuum breaker performance during the chugging event.
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