05000255/LER-2007-001

LER-2007-001,

Docket Number
Event date:	01-04-2007
Report date:	03-01-2007
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2552007001R00 - NRC Website

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Palisades Nuclear Plant 05000-255 2007 -- 001 -- 00

EVENT DESCRIPTION

On May 22, 2006, the automatic load tap changer for startup transformer 1-2 [XFMR;EB] was noted to be non-functional. Upon discovery, the startup transformer was declared inoperable until repairs were completed. Subsequently, it was recognized that past operability of startup transformer 1-2 needed to be conducted for the period of time that the startup transformer's automatic load tap changer was not functioning; which was determined to be the period between,May 16, 2006, and May 22, 2006.

On January 4, 2007, the evaluation of the past operability status of startup transformer 1-2 was concluded. The results of the evaluation were that startup transformer 1-2 should have been declared inoperable on three separate occasions, based on the recorded output voltage of the transformer. The inoperable periods occurred on May 18, May 19 and May 22; with the duration of each inoperable period not exceeding 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />.

Startup transformer 1-2 is associated with one of the two credited offsite power sources required by Technical Specification (TS) Limiting Condition For Operation (LCO) 3.8.1, "AC Sources - Operating." Consequently, during the three identified periods of inoperability, TS LCO 3.8.1.A for one offsite circuit inoperable was applicable. However, since the startup transformer's past periods of inoperability were not recognized at the time, the required action of TS LCO 3.8.1.A.1 to perform an offsite source check for the operable offsite circuit was not performed in accordance with the specified completion time of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter.

The failure to perform the offsite source check within the specified completion time is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.

CAUSE OF THE EVENT

The failure of the automatic load tap changer was attributed to mechanical binding internal to interlocked contactors.

CORRECTIVE ACTIONS

An extent of condition review was performed. No other similar components were identified.

The raise/lower contactor set for the automatic load tap changer was replaced and tested satisfactorily.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) Palisades Nuclear Plant 05000-255 2007 -- 001 00

SAFETY SIGNIFICANCE

The safety significance of this occurrence is considered to be minimal. The intent of the offsite source check is to ensure a highly reliable power source remains with one offsite circuit inoperable by verifying the operability of the remaining required offsite circuit on a more frequent basis.

Although not verified in accordance with the TS requirements, the remaining offsite source and both emergency diesel generators were operable during each of the three periods of inoperability of startup transformer 1-2.

PREVIOUS SIMILAR EVENTS

None