ML19339A599

LER 80-032/01T-0:on 801014,core Spray Sparger Visual Insp Per IE Bulletin 80-13 Revealed Semicircular Indication on End Cap of C Sparger Junction Box.Caused by Intergranular Stress Corrosion Cracking.Clamp Type Cover Being Designed

ML19339A599
Person / Time
Site:	Vermont Yankee
Issue date:	10/28/1980
From:	Murphy W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19339A597	List: ML19339A596 ML19339A599
References
IEB-80-13, LER-80-032-01T, LER-80-32-1T, NUDOCS 8011040387
Download: ML19339A599 (2)

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LICENSEE EVENT REPORT LER 80-32/lT CONTROL 8 LOCK: l l l l l l (PLEAss PRINT OR TYPE ALL REQUIREO INPORMATION) fiTil 8I 9v i TLICENSEE 7

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7 8 09 75 REPORT CATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h 10 l 2 l l During performance of Core Spray Sparger Visual Inspections in accordance with NRC l

[5Tr1 l IE Bulletin 80-13, a semi-circular linear indication was observed on the end cap of f I O I 4 I I the junction box on the "C" Core Spray Sparger. Further investigations reveal that l ITTT1 I this indication is a crack. See the attached description for additional details. I F5Te 1 1 1 10171 l I I o Ia I I I

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i [ o ; lThe probable failure mode is IGSCC. See the attached description for additional l I1 11 1 dI etails . I 11 1

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES During performance of Core Spray Sparger Visual Inspections in accordance with NRC IE Bulletin 80-13, a semi-circular linear indication was observed on the and cap of the junction box on the "C" Core Spray Sparger. Further investigation has revealed that this indication is a crack, apparently in the sensitized, heat-affected zone of a weld used to install a one-inch diameter solid plug in a visual access hole drilled in the center of the and cap.

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS The probable failure mode is IGSCC. .A preliminary review of documenta-tion concerning the material used to manufacture the four junction box end caps indicates that the cracked material may have been more susceptible to IGSCC than that used for the other three end caps. At this time, considera-tion is being given to application of a clamp-type cover on the affected end cap. This cover would prevent loss of the plug in the reactor vessel in the event it is dislodged outwardly during core spray operation, and would serve to restrict unplanned flow from the cracked area. Design and manufacture of this device is in progress. A meeting with the NRC in Bethesda has been scheduled for October 31, 1980, at which a full report concerning intended corrective action will be presented.

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