05000255/LER-2006-003

LER-2006-003,

Docket Number
Event date:	03-29-2006
Report date:	05-26-2006
Reporting criterion:	10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown
2552006003R00 - NRC Website

U.S. NUCLEAR REGULATORY COMMISSION Palisades Nuclear Plant 05000-255 2006 -- 003 -- 00

EVENT DESCRIPTION

On March 29, 2006, with the plant in Mode 1, left train high pressure safety injection system subcooling control valve CV-3070 [V;BQ] failed to stroke open during a preventive maintenance activity, resulting in entry into Technical Specification (TS) LCO 3.5.2.B.1, for the inoperability of one Emergency Core Cooling System (ECCS) train.

On March 31, 2006, a shutdown was commenced when it was determined that the 72-hour completion time for restoring CV-3070 to operable status could not be met. On April 1, 2006, the shutdown was completed in accordance with TS LCO 3.5.2.C.1 and 2 required actions.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(A) as the completion of any nuclear plant shutdown required by the plant's Technical Specifications.

CAUSE OF THE EVENT

During initial investigation, CV-3070 stroked open following minor physical agitation. Subsequent diagnostic testing of CV-3070 showed that valve stem movement was not smooth. Inspection of the valve stem revealed galling along the underside of the stem that coincided with the length of the valve stroke; indicating that the stem was making excessive contact with the valve bonnet backseat surface along the underside of the stem.

CV-3070 is mounted in a vertical pipe section with its air operator oriented horizontally.

Investigation revealed that the end of the valve's air operator was sagging approximately 1.5 inches from horizontal. A search of records revealed that the operator had previously been supported by a hanger that had been removed in 1994.

The failure of CV-3070 was determined to have occurred from excessive valve stem interference that resulted from inadequate support of CV-3070's air operator, following removal of the support hanger.

CORRECTIVE ACTIONS

Valve components for CV-3070 were replaced. A support hanger has been reinstalled to support the valve's air operator.

NFU FLW1m 366A (1 -2001 ) FACILITY NAME (1) PAGE (3) LER NUMBER (6) DOCKET NUMBER (2) U.S. NUCLEAR REGULATORY COMMISSION Palisades Nuclear Plant 05000-255 2006 -- 003 -- 00

SAFETY SIGNIFICANCE

The safety significance of this occurrence is considered minimal. The applicable required actions and associated completion times for one inoperable ECCS train were satisfied in accordance with Technical Specification LCO 3.5.2.

PREVIOUS SIMILAR EVENTS

None