ML20134E982

Provides Status of Analysis of torus-to-drywell Vacuum Breaker Valves for Limiting Load Combination.Deferment of Any Mod Work on Subj Valves Until at Least Cycle 12 Refueling Outage Requested

ML20134E982
Person / Time
Site:	Oyster Creek
Issue date:	08/14/1985
From:	Fiedler P GENERAL PUBLIC UTILITIES CORP.
To:	Zwolinski J Office of Nuclear Reactor Regulation
References
(0052A), (52A), NUDOCS 8508200637
Download: ML20134E982 (2)

Text

Q. 1 I

GPU Nuclear Corporation Nuclear  :: sten:r388 Forked River.New Jersey 08731-0388

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i 609 971-4000 Writer's Direct Dial Number:

August 14, 1985  ;

i Mr. John A. Zwolinski, Chief Operating Reactors Branch No. 5 Division of Licensing U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Oyster Creek Nuclear Generating Station Docket No. 50-219 Mark I Containment Torus-to-Drywell Yacuum Breakers

Reference:

(1) NRC letter dated April ll,1985 from J. A. Zwolinski (NRC) to P. B. Fiedler (GPUN)

(2) NRC letter dated December 24, 1984 from D. B. Vasallo (NRC) to H. C. Pfefferlen (GE)

In accordance with Reference 1, this letter provides the status of analysis of the Oyster Creek Torus-to-Drywell vacuum breaker valves for the limiting load combination, which includes the chugging slamming transient defined in the latest General Electric Mark I Program load definition and all other concurrent Mark I Program loads. The wetwell-to-drywell differential pressure load and vacuum breaker response analysis had incorporated the wetwell-to-drywell vacuum breaker load methodology approved by the NRC (Reference 2).

The GPUN analysis has provided preliminary results indicating that the following vacuum breaker valve parts could become overstressed:

. Counterweight Arms

. Disk Arm j Disk Arm Keys

. Valve Shaft

. Counterweight Hubs

. Counterweight Hub Keys 8508200637 DR 850914 ADOCK 05000219 GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation Ao25 lO

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Mr. John A. Zwolinski U.S. Nuclear Regulatory Commission Page 2 GPUN is currently considering a one-for-one replacement of valve parts (with different material properties) as a means to achieve acceptable stresses. However, discussions with Continuum Dynamics, Inc. have indicated that there may be excess conservatism in the Reference 2 analysis which, if eliminated, could result in acceptable stress levels for the identified valve parts. GPUN intends to pursue the performance of a modified analysis with CDI. The additional analysis is anticipated to require approximately 8 weeks. The results of this analysis will be forwarded to your attention as soon as they become available.

In light of the late NRC approval of the load methodology to be used in analyzing the plant specific vacuum breaker loads and the fact that we are still evaluating the need for any valve modifications, GPUN requests deferment of any modification work on these valves until at least the Cycle 12 refueling outage (12R).

Very truly yours,

- 12 ) ,

Petef B #Tedler Vice President and Director  ;

Oyster Creek PBF/ dam Enclosures cc: Dr. Thomas E. Murley, Administrator Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406 Mr. Jack N. Donohew, Jr.

U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue, Phillips Bldg.

Bethesda, MD 20014 Mail Stop No. 314 NRC Resident Inspector Oyster Creek Nuclear Generating Station Forked River, NJ 08731 (0052A)