05000255/LER-2003-001
| Palisades Nuclear Plant | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2552003001R00 - NRC Website | |
EVENT DESCRIPTION
On January 15, 2003, at 2015 hours0.0233 days <br />0.56 hours <br />0.00333 weeks <br />7.667075e-4 months <br />, with the plant in Mode 1, it was determined from a review of surveillance procedure basis information, that all four steam generator [SG;AB] (SG) reactor protection system [JC] (RPS) low-level trip setpoints in each SG were set such that the trip could occur below the allowable value specified in Technical Specification (TS) 3.3.1. The SG low-level trip setpoints were declared inoperable. It was determined that this condition had existed since 1998.
TS 3.3.1 requires four associated instrument channels, for the SG low-level RPS trip functions, to be operable in Modes 1 and 2, and in Modes 3, 4 and 5 when more than one full-length control rod is capable of being withdrawn and the primary coolant system [AB] boron concentration is less than refueling boron concentration. TS 3.3.1 does not provide a condition for all four SG level instrument channels being inoperable. Therefore, TS 3.0.3 was entered. Nuclear Management Company, LLC, (NMC), requested enforcement discretion to extend the completion times in TS 3.0.3 by an additional 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> to avoid a plant shutdown. The Nuclear Regulatory Commission Staff verbally exercised discretion on January 16, 2003 at 0017 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br />.
This occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
CAUSE OF THE EVENT
A vendor calculation error resulted in the incorrect determination for the SG level transmitter static correction factor term. This resulted in biasing the calculated setpoints for the RPS channels on both steam generators in a manner that could cause the associated trips to actuate below the required TS requirement. This was compounded by knowledge deficiencies and technical review rigor deficiencies by the plant engineering staff.
CORRECTIVE ACTIONS
To compensate for this error, the setpoints were adjusted upward, and the SG low-level RPS trip functions were declared operable on January 16, 2003, at approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />.
The need for further training is being evaluated for appropriate system and design engineers in the procedures and calculation of the static pressure shift correction factor term for Rosemount differential pressure transmitters.
Rigorous application of engineering principles was reiterated.
The instrument setpoint methodology design guide is being revised to incorporate the lessons learned from this event.
The SG level transmitter calibration procedure is being revised and the transmitters will be restored to the correct values during the 2003 refueling outage.
SAFETY SIGNIFICANCE
The allowable value for the SG low-level setpoints contained in TS 3.3.1 is .25.9%. The allowable value was chosen to assure that Auxiliary Feedwater (AFW) flow would be initiated while the SG could still act as a heat sink and steam source, and to assure that a reactor trip would not occur on low level without the actuation of AFW.
NMC determined that the configuration of the low level trip setpoints resulted in a worst-case setpoint of approximately 24.71%. Although less than the TS allowable value, this setpoint is greater than the analytical value (18.14%) contained in the plant safety analysis, after including total loop uncertainties.
Therefore, since analytical limits were maintained, this event had no safety significance.
PREVIOUS SIMILAR EVENTS
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