ML19257D809
| ML19257D809 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 01/30/1980 |
| From: | Wood E Maine Yankee |
| To: | |
| References | |
| NUDOCS 8002060516 | |
| Download: ML19257D809 (1) | |
Text
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f$5l$EE AMIUl0E0W302.',T'?a Box 450, RFD 2 g -- g
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Wiseasset, Maine 04578
'Q.._. Q January 30, 1980 United States Nuclear Regulatory Commission Directorate of Regulatory Operations Region I 631 Park Avenue King of Prussia, PA 19406
Reference:
License No. DPR-36 (Docket No. 50-309)
Dear Sir:
Subject:
Maine Yankee Reportable Occurrence #80-001/OlL-0 Pursuant to the requirements of Technical Specification 5.9.1.6.h, the Maine Yankee Atomic Power Company hereby submits the following report.
la the course of reviewing the steam line break analysis in response to the concerns raised by the NRC with regard to automation of the auxiliary feedwater systr4, it was discovered that an incorrect assumption was utilized in the zero or low-power steam line break analysis. The analysis had assumed that at low power levels, when feedwater is being controlled by the feedwater regulating valve bypass valves, that these bypass valves would remain "as-is" throughout the transient. In reality, as a result of the low steam generator pressure reactor trip signal, an override signal causes the feedwater bypass valves to ramp to an 80% open (5% full feedwater flow) position. A reanalysis of this event shows that this opening of the feedwater bypass valves results in an unaccepcably high rate of feede=ts.: addition to the affected steam generator causing a rapid cooldown of the reactor coolant system and a return-to-power transient. A return to power following a steam line break is not permitted under the current design basis for Maine Yankee.
The plant was in the refueling mode at the tim; :his error was discovered and therefore no immediate corrective acticn was ne.es ary. Modifi-cations necessary to correct this error shall be implemented prior to plant startup.
Very truly yours,
}g MAINE YANKEE ATOMIC POWER COMPANY b
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Edwin C. Wood Plant Manager ECW/ mf k
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