05000361/LER-2002-006
| San Onofre Nuclear Generation Station (Songs) Unit 2 | |
| Event date: | 11-02-2002 |
|---|---|
| Report date: | 12-31-2002 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3612002006R00 - NRC Website | |
6 LER NUMBER I FACUTY NAME 05000-361 2002 —006 — 00 Reactor Vendor: Combustion Engineering
Description of the Event:
On November 2, 2002 at 0316 PST (event date), with Unit 2 reactor at 100% power, the Reactor Protection System (RPS) {EIIS Code JC} actuated causing a Unit 2 reactor trip. A main Feedwater (FW) controller failed {EIIS Code JB}; the FW regulating valve (2FV1111) {EIIS Component Code FCV} began to close; and the water level in steam generator 89 decreased to the low-level trip set point.
On November 2, 2002, at 0538 PST, Southern California Edison (SCE) made a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> telephone notification to the NRC Operations Center (Log No. 39340) in accordance with 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). SCE is providing this follow-up report in accordance with 10 CFR 50.73(a)(2)(iv)(A).
Cause of the Event:
SCE's cause evaluation is ongoing. However, preliminary investigations indicate that the 2FC1111 main FW controller card (serial number 3252836) had a shorted low limit operational amplifier (Motorola, MLM301AG, date code 7432) (Cause Code: X). This may be an age-related failure. This LER will be supplemented if this conclusion changes significantly.
Corrective Actions:
SCE replaced both Unit 2 main FW controller cards (2FC1111 and 2FC1121) with new cards (even have been scheduled for replacement.
Safety Significance:
UFSAR Section 15.2.2.5 and 15.10.2.2.5 evaluate the Loss of Normal Feedwater Flow with the plant at full power. The UFSAR analysis shows that all of the event acceptance criteria (DNBR, offsite doses, peak linear heat rate, peak RCS pressure, and peak secondary pressure) are met. Therefore, there was little to no safety significance to this event.
An assessment of the conditional core damage probability (CCDP) and the conditional large early release probability (CLERP) for the November 2, 2002 event, determined that the Unit 2 CCDP and CLERP were 5.0E-6 and 2.2E-7, respectively. The assessment was based on the reported actual component unavailability and system alignments at the time of the event.
Additional Information:
On November 21, 1999, the Unit 3 main feedwater controller card 3FC1121 failed due to a manufacturing defect (pinhole oxide defect) in an operational amplifier (Fairchild, date code 7825). That controller card had been in service for many years and when it failed, it failed at the location of the manufacturing defect.
Corrective actions for the November 21, 1999 event focused on cards with Fairchild operational amplifiers.