ML19320B094
| ML19320B094 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 07/01/1980 |
| From: | Grace R Maine Yankee |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| WMY-80-104, NUDOCS 8007090295 | |
| Download: ML19320B094 (2) | |
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WMY 80-104 United States Nuclear Regulatory Commission Washington, DC 20555 Attention:
Of fice of Nuclear Reactor Regulation
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b) MYAPC Letter to USNRC dated May 2, 1980
Subject:
Maine Yankee Asymmetric LOCA Loading Evaluation
Dear Sir:
Maine Yankee has completed its evaluation of asymmetric LOCA loadings on the reactor pressure vessel, reactor internals, primary support system, centrol rod drive assemblies (control element assemblies - CEAs) and ECCS and branch piping systems attached to the reactor coolant system. Conclusions resulting from our evaluation are summarized as follows:
(a) Upper bound asymmetric LOCA loads applied to tae reactor pressure vessel supports are less than those used in original design calculations, (b) primary support system stresses due to normal op2 rating, maximum hypothetical seismic and upper bound asymmetric LOCA conditions, computed using the methodology and conservatisms employed in original design analyses, are within original allowable stress limits stipulated in the Maine Yankee FSAR, (c) maximum reactor internals loadings due to asymmetric LOCA are less than those originally considered for Maine Yankee, (d) ECCS piping systems attached to the intact reactor coolant system loops are structurally adequate to withstand loadings due to normal operating, maximum seismic and applied transient displacement loadings due to RPV response to asymmetric LOCA loads, (e) branch piping attached to the intact reactor coolant system loops do not degrade ECCS function when subjected to normal operating, maximum seismic and transient displacement loadings, the latter due to RPV response to asymmetric LOCA 1 cads, and 8007090 295 p
9 United States Nuclear Regulatory Commission July 1, 1980 Office of Nuclear Reactor Regulation Page 2 (f) maximum stresses at critical points of CEAs due to normal operating, maximum seismic and transient displacement loading due to reactor pressure vessel response to asymmetric LOCA are within original Maine Yankee FSAR allowable stress limits.
The conclusions stated in items (a), (b), and (c) are those which have been previously reported. Conclusions stated in items (d), (e) and (f) are based upon the results of dynamic analyses in ubich:
1.
structural system representations were developed to conservatively characterize the structural response to applied transient loadings, 2.
upper bound loadings were applied to the structural models and maximum atresses due to the applied transient displacements were combined with those due to normal operating and maximum seismic conditions, 3.
resulting combined stresses were evaluated with respect to the conservative acceptance criteria defined in the Maine Yankee FSAR and original design calculations. In those cases where FSAR stress limits for the specified loading criteria and corresponding functionability requirements did not exist, suitable acceptance criteria consistent with current code requirements and industry practice vere established.
Detailed descriptions of methodology, evaluation criteria and summary of results are forthcoming in a final version of the evaluation report.
In summary, Maine Yankee has completed its evaluation of the effects of asymmetric LOCA loadings end has concluded that the design basis, and safety evaluations described in the Maine Yankee FSAR are not adversely af fected by asymmetric loadings resulting from a postulated LOCA. This letter, along with the forthcoming documenting report, serves as final resolution of the January 25, 1978 letter to Maine Yankee Atomic Power Company concerning Asymmetric LOCA Loads.
Should you have any questions or wish to discuss the contents of this letter, please feel free to call.
Verv truly yours, MAINE YANKEE ATOMIC POWER COMPANY lobert H. Groce Senior Engineer - Licensing AVR/ dis
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