ML19208A368

LER 79-049/03L-1:on 790331,during Surveillance Testing Nine of 18 Main Steam Safety Valves Found Outside Design Setpoint Range.Caused by Changing Ambient Conditions,Valve Liftings from Previous Trips & Vibrations.Valves Adjusted

ML19208A368
Person / Time
Site:	Davis Besse
Issue date:	04/27/1979
From:	Brown R TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19208A364	List: ML19208A363 ML19208A368
References
TASK-TF, TASK-TMR LER-79-049-03L, LER-79-49-3L, NUDOCS 7909130479
Download: ML19208A368 (3)

Text

U.S. NUCLE AR REGULATORY COMMISSION AC FORM 36G 7 77)

LICENSEE EVENT REPORT (PLE ASE PRINT OR TYPE ALL REQUIRED INFORMATION)

CONTROL BLOCK: l I

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0 l 14 15 NvYtiE H 25 26 TYPE JJ 7 8 9 LICENSEE CODE CON'T o i "l"Cy L @] d j 5 l 0 ] - l 0 ] 3 l 4 l 6bd}@lL3 0 l 313 l 1 7 l 9 l@l0 l 4REPORT Ek ENT D ATE 14 lb l 2 lDAT7 El 7 l9HJl@

? 8 t,0 01 DOC A E T N a'ij E R EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h o 2 l During surveillance testing at 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> on 3/31/79, 9 of the 18 main steam safety [

o 3 valves were found to be outside of +1% design setpoint range. This placed the unit in) of T.S. 3.7.1.1, which requires valves to be operable in Modes 1,j o 4 l the Action Statement l 2, and 3. On 4/1/79, the unit entered a scheduled hat shutdown at 0015 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> and a j

o s There was no danger to the health and saf ety of j l o [6 l [ planned cold shutdown at 0646 hours0.00748 days <br />0.179 hours <br />0.00107 weeks <br />2.45803e-4 months <br />.

o 7 the public or unit personnel. The valves would still have served their intended fune j tion of relieving pressure if a unit trip had occurred. (NP-33-79-51) l o a 1 0 0 CAUSE COYP. VALVE SY ST E M C A US E SU"COCE SUSCODE COUPONENT CODE SUBLODE o 9 CODE

[C l Clg CODE g lB g V AlL lV JE [X l Q ] g ] g 18 19 20 9 10 11 12 73 7 8 HEFOHT REVISION SE QUE N TI AL OCCU R R E NCE CODE TYPE NO EVENT YE AR REPOHT NO gg _ 211719122 -1 10 41 91 1/l I 01 31 LI l-1 11 1

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JS J6 3/ 40 41 42 43 44 17 cAUSE DESCRIPTION AND CORRECTIVE ACTIONS h I i o l The came of the variation is believed to be due to changing ambient cond itions, valve ,

Design changes ,

,jij [11ftings from previous unit trips, and/or flow induced vibration.

The valves  ;

,,,, j nave been iraplemented to help reduce ambient and vibration eff ects.

The location of the 1050 and .j ly l have been adjusted and reccated during plant startup.

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, j, j [ 1100 psig valves have been interchanged to minimize flow induced vibration, so 7 8 9 OTHER S T A TUS D SCO Y DISCOVERY DESCRIPi SON ST A $  % POWE R l

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70W130 479 I j_LJ 5 2 o issuyf L )m @oISCniPriON@ I 68 s2 II I III 80 2 7 8 9 10 Richard A. Brown PHONE: 419-259-5000. Ext. 211 E, DVR 79-061 NAYE Of PREPARER

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POUER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-3? 79-51 DATE OF EVENT: March 31, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Fbin Steam Safety Valves found to be outside of + 1%

design setpoint range Conditions Prior to Occurrence: The unit was in Mode 1, with Power (>nn) = 194, and Load (Gross MWE) = 0.

Description of Occurrence: During the performance of ST 5070.01, " Main Steam Safety Valves Setpoint Test" at 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> on March 31, 1979, nine of the eighteen valves 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 requires valves to be operable in Modes 1, 2, and 3. The Action Statement requires 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 Shutdown within thirty hours.

The unit entered a scheduled Hot Shutdown at 0013 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> on April 1,1979, and planned Ccid Shutdown at 0646 hours0.00748 days <br />0.179 hours <br />0.00107 weeks <br />2.45803e-4 months <br /> on April 1,1979.

Designation of Apparent Cause of Occurrence: The apparent cause of the slight varia-tion in relief valve lift pressure is believed to be due to changing ambient condi-tions and/or flow induced vibration. Subsequent lifting of safety valves from numerous unit trips may have also affectedstheir lift setpoint. A potential problem with pre-vious hydrosets on these valves was identified by the valve vendor, Dresser, and the 1 air may not have been properly bled f rom the h,ydroset apparatus. As a result of this, the vendor hydroset maintenance procedure is being revised to ensure proper venting of the hydroset apparatus during the vendor calibration check.

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

1l Corrective Action: The valves were adjusted and retested per Maintenance Work Order 79-1698 during the plant startup. The location of the 1050 and 1100 psig valves have been interchanged per Facility Change Request 79-139 to minimize flow induced vibration.

The valve vendor, Dresser, has inspected the valve SPl7A2 (which had a spindle damag,d 1 as reported by Licensee Event icport NP-33-79-23) at their factory. They found no I major problems with the valve that would af fect its ability to maintain its setpoint.

LER #79-049 9!= 20u

a TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE PACE 2 SUPPLEMENTAL INFOP3!ATION FOR LER NP-33-79-51 Design changes have been implemented to install hoods on the main steam safety valve vent stack and provide ventilation to control the ambient temperature in the vicinity of the valves. Both of these changes will help control ambient conditions.

Failure Data:

There have been four previously reported occurrences of incorrect safety valve lift setpoints.

See Licensee Event Reports NP-33-77-117, NP-33-78-145, NP-33-79-23, and NP-33-79-25.

LER #79-049 1

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