ML20141H062
| ML20141H062 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 01/07/1986 |
| From: | Miraglia F Office of Nuclear Reactor Regulation |
| To: | Tucker H BABCOCK & WILCOX OPERATING PLANTS OWNERS GROUP, DUKE POWER CO. |
| References | |
| NUDOCS 8601130399 | |
| Download: ML20141H062 (1) | |
Text
l)lhE-M6 Mr. Hal B. Tucker DISTRIBUTION BGrimes Gray File B&W Owners Group NRC PDR JPartlow EBrach Executive Committee L PDR WPaulson H0rnstein Duke Power Company PBD-6 Rdg JThoma RConte P. O. Box 33189 FMiraglia JTaylor'(!!&W) 422 South Church Street 0 ELD RIngram Charlotte, North Carolina 28242 EJordan ACRS-10
Dear Mr. Tucker:
SUBJECT:
REPETITIVE LIFTING 0F STEAM SAFETY VALVES During recent planned reactor trips at TMI-1, repetitive lifting of the once through steam generator (OTSG) safety valves occurred. Our understanding of the events at TMI-1 is as follows.
During the reactor trips at both 40% and 75% reactor power, there was a pressure surge on the secondary side which caused the OTSG safety valves to lift. This is an expected occurrence.
Following the initial pressure relief via the OTSG safety valves, the secondary pressure should be controlled at 1010 psig by the turbine bypass valve; instead, some of the safety valves relieved pressure several times.
In the case of the A-0TSG, the safety valves relieved pressure three or four times after the initial surge. The operator then manually changed the setting for turbine bypass control from 1010 psig to 975 psig and pressure control was achieved without further safety valve lifts.
At TMI-1, the lowest safety valve setpoint is 1040 psig.
It is our understanding that after the initial lift, the safety valve setpoints drift down by about 3 or 4%. As a result of this setpoint drift, the safety valve can lift before the turbine bypass control can achieve pressure control. We understand that other B&W plants have similar experience.
While we view the repetitive lifting of the steam safety valves as an operational concern at this time rather than a significant safety concern, we do not consider repetitive challenges to the safety valves as a normal, acceptable long-term mode of operation. Accordingly, we request that the B&W Owners Group include this issue as a concern requiring appropriate resolution.
Sincerely, Original signud by Trank J. ElPMlia Frank Miraglia, Director Division of PWR Licensing-B Pb@!
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