ML19270F809

LER 79-032/03L-0 on 790222:main Steam Safety Valve SP17B1 Lifted Early While Unit Was About 15% Power Following Unit Runback.Cause Uncertain.Valves SP17A1/B1 Found Outside Design Setpoint.Valves Adjusted.Investigation Continuing

ML19270F809
Person / Time
Site:	Davis Besse
Issue date:	03/21/1979
From:	Brown R TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19270F807	List: ML19270F806 ML19270F809
References
FOIA-79-98 LER-79-032-03L, LER-79-32-3L, NUDOCS 7903270551
Download: ML19270F809 (3)

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NRC FORM 366 (7 77) -  %

LICENSEE EVENT REPORT

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7 8 EVENT DESCRIPTION AND PROB ABLE CONSEOUENCES h l

10121 l Main Steam Safety Valve SPl7B1 lif ted sarly while the unit was at approximately 15%

o 3 l power f ollowing a unit runback. This placed the unit in the Action Statement of Tech-i o 4 l nical Specification 3.7.1.1. The high flux trip setpoint had already been reduced to j o s l(92.91% of rated thermal power due to an inoperable steam safety valve on A loop. l lo is j l There was no danger to the health and safety of the public or station personnel. The j o 7 l remaining operable valves have enough relieving capacity to serve their intended ,

function of relieving pressure if a unit trip would occur. (NP-33-79-34) l o s I 80 DE CO E SLSO E COVPoNENT CODE StsC dE SL 0E g cl c @ l xl@ l xi@ lV l A lL lV lE lX l@ Q@ J @

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EVENT YEAR

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41 l Y [g 42 43 Nl@ l D l 2 l 4 [ 3 lg 44 47 CAUSE DESCR!aTION AND CORRECTIVE ACTIONS h i o lThe apparent cause is not certain. The two 1050 psig and two 1070 psig safety valves I Iilil 1 on each header were tested. Valves SPl7Al/B1 (1050 psig) were found to be outside

, 7 l the design setpoint. The valves were adjusted, tested, and declared operable at 2115 lil3ll hours on 2/22/79. An evaluation to determine actual cause of the occurrence, and to l I

li i4 l l provide a resolution, is being performed.

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% POWER OTH ER STATUS ISCO RY DISCOVERY DESCRIPTION STA $

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TOLEDO Ei' SON COMPANY DAVIS-BESSE NUCLEAR r WER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-34

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DATE OF EVENT: February 22, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Main Steam Safety Valve lif ted early Conditions Pr ior to Occurrence: The unit was in Mode 1, with Power (MWT) = 416 and Load (Gross MUE) = 0.

Description of Occurrence: A Main Steam Safety Valve (SPl7B1) on B loop (Steam Genera-tor 1-1) lif ted early while the unit was at steady state condit17n at approximately 15%

power f ollowing a unit runback.

s This placed the unit in the Action Statenent of Technical Specification 3.7.1.1 which requires the valves to be operable in Modes 1, 2, and 3. The Action Statement re-quired the valve to be restored to operable status or the high flux trip setpoint be reduced within four hours, or the unit b_e in Hot Shutdown (Mode 4) within six hours and Cold Shutdown within thirty hours. The high flux trip setpoint had already been reduced to<92.91% of rated thermal power per Table 3.7-1 due to an inoperable valve on A loop (Steam Generator 1-2).

Designation of Aoparent Cause of Occurrence: The apparent cause is not certain. It may be due to changing ambient conditions and/or flow induced vibration at low power levels.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The remaining operable valves have enough relieving capacity to serve their intended function of relieving pressure if a unit trip would occur.

Corrective Action: The two 1050 psig and two 1070 psig safety valves on each header were tested per Maintenance Work Order 79-1565 in order to determine the valve which lifted early. The first 1050 psig valve on each header (SPl7Al/B1) were found to be outside of !1% design setpoint. The valves were adjusted, tested, and declared operable at 2115 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.047575e-4 months <br /> on February 22, 1979. The valves (SPl7A3/A4/B2/B3/B4) were tested and found within !1% design setpoint.

Comoany oersonnel are working with the vendor in evaluating the safety valves in order to determine actual cause of occurrence and provide a resolution.

Facility Change Requests77-322 and 77-319 have been issued for implementation to install hoods on the main stean safety valve exhaust stacks for protection during LER #79-032

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TOLEDO EDISON COMPA'iY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEME' ITAL I'iFOR"ATION FOR LER NP-33-79-34 PAGE 2 OF 2

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winter months and provide ventilation during the su=mer months. Both FCRs will help control ambient conditions. Temporary ventilation will be provided if ambient tenpera-tures beco=e excessive.

Failure Data: There have been three previously reported occurrences of incorrect safety valve lif t setpoints. See Licensee Event Reports NP-33-77-ll7, NP-33-78-145, and hT-33-79-25.

LER #79-032 s

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