05000255/LER-2004-003

LER-2004-003,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2552004003R02 - NRC Website

U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) Palisades 05000-255 2004 -- 003 -- 02

EVENT DESCRIPTION

On October 23, 2004, with the plant in mode 6, offsite testing of main steam safety valve RV-0706 [SB;RV] determined that the as-found lift pressure did not meet the acceptance band of +/- 3% of setpoint, as specified by Technical Specification Table 3.7.1-1, "Main Steam Safety Valve Lift Settings." This was the second unsatisfactory as-found lift pressure for a main steam safety valve, as in-place testing on September 16, 2004, had previously determined that RV-0710 had failed to meet the as-found acceptance band.

Subsequently, continued testing both offsite, and later, in-place after the plant had been returned to power operation, revealed 9 more unsatisfactory, main steam safety valve as-found lift pressure tests, for a total of 11 out of 24 unsatisfactory as-found tests. See Tablel for additional data on the unsatisfactory as-found lift pressure results. All of the unsatisfactory as-found lift pressures were above the acceptance band.

Technical Specification LCO 3.7.1 requires a minimum of 23 out of 24 main steam safety valves to be operable in modes 1, 2 and 3. Since the cause of the multiple unsatisfactory as-found lift pressures may have arisen over a period of time, there is a likelihood that all of the required main steam safety valves were not operable during past plant operation. Therefore, this occurrence is considered reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's Technical Specifications.

CAUSE OF THE EVENT

The cause of the occurrence has been identified as a combination of disc/seat sticking and binding/bonding at the valve spindle guide bearing. Industry experience has shown that disc/seat sticking may be identified by the as-found lift pressure being approximately 30 psi higher than a second lift pressure when re-tested. All eleven of the unsatisfactory test results exhibited a significant reduction in lift pressure on the second lift, indicating potential disc/seat sticking. Also, based on the second lift, all eleven of the unsatisfactory main steam safety valves would have either met the as-found acceptance criterion, or in one case, lifted below the acceptance band.

SAFETY SIGNIFICANCE

The safety significance of this occurrence is minimal. Analysis of postulated events that credit operation of the main steam safety valves has determined that neither the acceptance criteria nor plant design limits would have been challenged with the as-found condition of 11 out of 24 main steam safety valve lift pressures above the acceptance band.

FACILITY NAME (1)� DOCKET NUMBER (2) LER NUMBER (6� PAGE (3) Palisades 05000-255 2004 -- 003 -- 02

CORRECTIVE ACTIONS

Final lift pressures were established in accordance with requirements. A maintenance and testing plan has been developed to test the valves on a more frequent basis.

PREVIOUS SIMILAR EVENTS

Palisades Licensee Event Report 86-004, "Main Steam Relief Valves Fail To Meet 'As Found' Pressure Acceptance Criteria" Palisades Licensee Event Report 83-074, 'Valves Failed To Meet 'As Found' Acceptance Criteria" Palisades Licensee Event Report 78-002, (not titled)