ML20127J583
| ML20127J583 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 05/24/1978 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9211190375 | |
| Download: ML20127J583 (1) | |
Text
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NOMTHERN 5TATES POWER COMPANY uiNN s Apou s, ueNN E SOTA 55400 V
May 24, 1978 Director ij; a
Nuclear Reactor Regulation U S Nuclear Regulatory Commiscion u
Washington, DC 2055 V
MONTICELLO NUCLEAR GENERATING PIANT
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Docket Nc. 263 License No. DPR-22 Multipic-Subsequent Actuations of Safety-Relief Valves Following an Isolation Event The enclosure attached to your letter dated March 20, 1978 requested informa-tion relative to torus loadings resulting from multiple-subsequent actuations of safety / relief valves. On October 31, 1977 ve submitted a document to you entitled " Documentation of Basis for Continued Operation, Sequential SRV Actuations of Isolated Events." We have reviewed our October 31 submittal and have concluded that all of the information requested in your March 20 letter is contained in this submittal.
Many different methods have been developed for evaluating the effects of multiple-subsequent SRV actuations. Use of these different methods could change the strength ratios reported in October, 1977; however, none have been identified that would change our conclusion that the plant has adequate safety margins for continued operation.
Since October, 1977 the replacement of three ramshead discharge de-'ces with three T-quenchers has been completed. In-plant SRV discharge tests confirmed that there is a significant load reduction with the T-quencher compared to the rasmhead. Plans are presently underway for replacement of the remaining five ramshead discharge devices during the Fall 1978 refueling outage. The extreme assumption used in the October,1977 analysis that all eight safety / relief valves would open a second time together provides additional assurance that none of the acceptance criteria for the containment structure would be exceeded for multiple subsequent SRV lifts.
L 0 Mayer, PE Manager of Nuclear Support Services LOM/ak 781510004 cc: J G Keppler G Charnoff e
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