ML20052A466

LER 82-023/03L-0:on 820312,during Refueling,Mode Bench Testing of Main Steam Safety Relief Valves Revealed Pilot Sensing Tube Missing from Valve 312.Caused by Failure of Welds to Hold Sensing Tube in Place

ML20052A466
Person / Time
Site:	Hatch
Issue date:	04/08/1982
From:	Sumner H GEORGIA POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20052A460	List: ML20052A459 ML20052A466
References
LER-82-023-03L, LER-82-23-3L, NUDOCS 8204280354
Download: ML20052A466 (2)

Text

NRC FORM 306 U. S. NUCLEAR REGULATORY COMMISSION (7 77I LICENSEE EVENT MEPORT (P! EASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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7 8 63 EVENT DATE 74 75 DATE EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h O 2 l With Unit 2 in refueling mode, bench testing of the main steam safety I ic i3 i l relief valves was in progress per HNP-2-6020. Wyle personnel noted thail

[O i4 ; l the pilot sensing tube was missing from valve S/N 312. No signi ficant l lOis [ occurrence took place as a result of this event. Unit I has installed l O s I valves of the same design. This is a non-repetitive event. This event l l0l7ll posed no threat to public health or safety. All of the other ten rel i e f l iOis i ; valves were available and operable. I DE CODE S BC E COMPONENT CODE SUBCO D'E s DE O 9 l C l C l@ [Ej@ lB l@ l Vl Al Ll Vl El Xl@ W@ W @

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[Njg _lTl0l2l0lg 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h i O l The cause of this event was failure of the welds that hold the sens'ing l

, i l tube in place. The tube will be replaced by the vendor prior to rein- l

,, ,,, i stallation of the valve. The affected welds on all other Unit 2 valves i

,3 will be inspected prior to unit startup. The affected welds on all Unit l ii i., ; 1 valves will be inspected during the next refueling outage. l

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LER f: 50-366/1982-023 Licensee: Georgia Power Company 4 Facility Name: Edwin I. Hatch Docket #: 50-366 Narrative Report for LER 50-366/1982-023 With Unit 2 in the refueling mode, bench testing 'of the main steam safety / relief valves was in progress per- plant procedure HNP-2-6020, " Main Steam ~ Relief Valves Maintenance". During setup for testing at Wyle Laboratories, Wyle personnel- noted

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that the pilot sensing tube was missing from valve body S/N i 312 which had been installed during plant operation as 2B21-F013B. This valve is a Target Rock model 7567 F safety / relief valve. Further investigation showed that the main disc and main seat of this valve were damaged in a way that could have been caused by passage of the pilot sensing tube during valve operation. The discharge route and present location of the tube has not yet been confirmed.

Investigation is underway by site personnel to resolve this question. The purpose of the pilot sensing tube is to provide a - true pressure to the pilot assembly during valve actuation.

At th is time the static pressure in the valve is reduced due

to steam flowing through the open valve. The absence of the pilot sensing tube does not affect the - valve actuation setpoint. The A/E is in the process of investigating this and any other potential effects that this type of failure could have on valve At the time of the event, all' of operability safety / relief valves were operable.

the remaining ten Plant Technical Specifications requires nine of these valves to be operable for pressure relief function. No significant occurrence took place as a result of this event. The main steam safety / relief valves installed on Unit 1 are of'the same make and model. This is a non-repetitive event. This event posed no threat to public health or saf ety.

This event was caused by a failure of the tube support welds.

The support plates were found in place on the valve wall. The

, tube-to-plate welds had failed, thus releasing the tube.

i The tube for this valve will be replaced by the vendor using a new support design. The new support is comprised of a single strap which fits over the tube and is welded to the wall on both sides. The other damaged components of this valve will also be replaced by the vendor.

The A/E is in the process of investigating the need for modi fi ca ti on of the balance of plant valves. All of the remaining Unit 2 valves of this design, including spares, will be inspected to assure the integrity of the tube support welds prior to un it startup. All of the Unit i valves of this design will be inspected during the upcoming Unit i refueling outage. An update report will be submitted when the

inspection is complete.

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