ML19225C135
| ML19225C135 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 07/23/1979 |
| From: | Groce R Maine Yankee |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| WMY-79-73, NUDOCS 7907260590 | |
| Download: ML19225C135 (2) | |
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__wO kHY 79-73 July 23, 1979 United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention: Office of Nuclear Reactor Regulation
References:
W) License No. DPR-36 (Docket No. 50-309)
(b) MYAPC Letter to USNRC dated February 21, 1978 (c) USNRC Letter to MYAPC dated January 25, 1978
Dear Sir:
Maine Yankee Asyrcretric LOCA Loads Evaluation
Subject:
Maine Yankee had cormitted in Reference (b) to begin an evaluation of the consequences of asyrmetric LCCA loads on the primary coolent systca.
to review the time Ebasco Services has been awarded a contract Since that extant asyntetric loads analyses to deternine the applicability to Maine This Yankce directly or indirectly by appropriate conservative scaling.
inf ormation was necessary to establish the best course of action for Maine Yankee to resolve the concerns expressed in Reference (c).
The preltainary version of th.t report was received in April of 1978 and reviewed by the Nuclear Services Division (NSD) of Yankee Atomic Ebascc was abla to co~.ervatively esticate peak values Electric Cnapany.
of loads that were generated by the asytretrical loading phenomenon on the reactor vessel. A computer model similar to the version that was used to license Maine Yankee was constructed by NSD and the peak loads
.ne resulting vessel support applied along with the original design loads.
loads were in the plastic range which invalidaced the clastic analysis.
The next step was to re-evaluate the assumptions used by Ebasco to obtain Ebarco Services was requested to refine their nodel for the the loadings.
reactor vessel cavity pressurization loadings and incorporate revised cass The new blowdown data represented and energy released data supplied by NSD.
mass cnd energy r:3 ease f rom a pipe break less than a full double ended The revised report and loads have been received frcu guillotine rupture.
Ebasco and is pre. ntl'f being evaluated by NSD. Depending on the outccme structural analysis incorporating the new loadings and a cost of the benefit analyses, one of the following steps will be taken:
perform nore concise dynamic plastic analyses; or 1.
conceptually design and evaluate !nstallation of pipe restraints 2.
which will limit the break to an assumed acceptable break area.
This evaluation will be cenpletcd af ter the next extended cutage (currently planned f or September) when actual geometric ccnfigurations can be defined at the plant.
79072605%
United States Nuclear Regulatory Conni'sion July 23, 1979 Attention: Office of Nuclear Reactor Regulation Page Two As required by Reference (c) additional analyses are required, i.e.,
pump supports, steam generator supports, etc.
Maine Yankee's approach has been to first assure the adequacy of the vessel supports since we felt
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this area to be the most highly loaded.
This assumption has recently been proven by the analyses performed by k'estinghouse and Combustion Engineering for the Owners Groups.
In general, both vendors have concluded that the i
additional LOCA loads are a small portion of the original design loads and
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that the original design limits are not exceeded. Maine Yankee is confident that a similar analyses performed for Maine Yankee will reach the same concit s.
We are at this present tire in contractural negotiations with Corbustion Engineering to perform the appropriate evaluations to envelope Maine Yankee under their present generic analysis pertainirg to pipe breaks in the primary piping outside of the reactor vessel cavity. Upon release of the contract, we will notify the NRC of a tentative schedule and completion date for this phase of the analysis.
In conclusion, Maine Yankee feels that we are addressing the consequences of LOCA induced asyrmetrical Joads in a tanner consistant with our committent and your requirements. By the beginning of October of this year, a detailed schedule for the completion cf our evaluation will be sent to the NRC.
At this time we feel confident that we will be able by the end of this year, to present to the NRC our resolution of the asytmetrical loading problem.
If you have any questions regarding this issue, feel free to call us at (617) 366-9011.
Very truly yours, MAINE YANKEE ATOMIC PO'.TR COMPANY
/
F Robert H. Groce Licensing Engineer TMC/stw i