ML19282A775

LER 79-020/03L-0 on 790205:10 of 18 Main Steam Safety Valves Found Outside Setpoint Range.Believed Caused by Changing Ambient Conditions at Valve Locations.Valves Adjusted & Retested Satisfactorily

ML19282A775
Person / Time
Site:	Davis Besse
Issue date:	02/28/1979
From:	Brown R TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19282A762	List: ML19282A760 ML19282A775
References
LER-79-020-03L, LER-79-20-3L, NUDOCS 7903060475
Download: ML19282A775 (3)

Text

U. S. NUCLFAR REGULATORY COMMISSION NRC FORM 3G6 (7 77)

LICENSEE EVENT REPORT (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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7 60 DOCKET NUMBER EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h I o l 2 l l It was noted on February 5,1979 by the Nuclear Regulatory Commission, that a required l l o 13 l l thirty day written report had not been submitted. As a result of surveillance testing l 0 4 l conducted on July 21, 1978, ten of the eighteen main steam safety valves were found l lo Isl l outside the setpoint range. This placed the unit in the Action Statement of Tech l 0 6 Spec 3.7.1.1. The valves were returned to operable status within four hours. There l The valves l o 17 ] I was no danger to the health and safety of the public or unit personnel. l (NP-33-79-25) l o a I wOuld still have served their intended function.

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J5 l36Zl@ 31 40 41 42 43 44 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS i o l The cause of the variation is believed to be due to changine ambient conditions at the]

li ii ] l location of the valves. Subsequent lifting of safetv valves from numerous unit trios jij7 l may have also affected their lif t setpoint. The valves were adjusted and retested I Facility Change l i 3 l satisfactorily and declared operable by 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on July 21, 1978.

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DVR 79-029 NAME OF PREPARER

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMETAL INFORMATION FOR LER NP-33-79-25 DATE OF EVENT: February 5, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Main Steam Safety Valves were tested and found to be outside of + 1% design setpoint range Conditions Prior to Occurrence: On July 21, 1978, the unit was in Mode 3, with Power (MWT) = 0, and load (Gross MWE) = 0 -

Description of Occurrence: It was noted on February 5, 1979, by the Nuclear Regu-latory Commission that a required thirty day written report covering the out of tolerance setpoint of ten main steam safety valves had not been submitted.

As a result of surveillance testing conducted on July 21, 1978, ten of the eighteen valves during the initial lif t were found to be outside of + 1% design setpoint range.

This placed the unit in the Action Statement of Technical Specification 3.7.1.1, which required the valves to be operable in Modes 1, 2, and 3. The Action State-ment required the valves to be restored to operable status within four hours or the high flux trip setpoint be reduced or the unit be in Hot Shutdown (Mode 4) within six hours and Cold Shtudown within thirty hours. The valves were returned to opera-ble status within four hours.

Designation of Apparent Cause of Occurrence: The apparent cause of the slight varia-tion in relief valve lif t pressure is believed to be due to changing ambient condi-tions at the location of the valves. The ambient conditions at the location of the valves were different from the last test conducted in January,1978.

Subsequent lifting of safety valves from numerous unit trips may have also affected their lift setpoint.

Analysis of Occurrence: There was no danger to the health and safety of the public or to unit personnel. The unit was being started up at the time of the conduct of the test. The valves would still have served their intended function of relieving pressure if a unit trip had occurred.

Corrective Action: The valves were adjusted and retested per Maintenance Work Order 78-800 and the last was declared operable by 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on July 21, 1978.

LER #79-020 .

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR PO'iER STATION UNIT ONE PAGE 2 SUPPLEMENTAL INFORMATION FOR LER NP-33-79-25 Facility Change Requests77-322 and 77-319 have been issued for implemen-tation to install hoods on the main steam safety valves exhaust stack for protec-tion during the winter months and provide ventilation during the summer months.

Both FCRs will help control ambient conditions. Temporary ventilation will be provided if ambient temperature becomes excessive.

Failure Data: There have been two previously reported occurrences of incorrect safety valve lif t setpoints. See Licensee Event Reports NP-33-77-ll7 and NP-33-78-145.

LER #79-020

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