05000361/LER-2002-006, Main Feedwater Controller Fault Causes Loss of Main Feedwater and Reactor Trip on Low Steam Generator Level
| ML030060075 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 12/31/2002 |
| From: | Waldo R Southern California Edison Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 02-006-00 | |
| Download: ML030060075 (3) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3612002006R00 - NRC Website | |
text
SOUTHERN CALIFORNIA U ED ISO An EDISON INTERNATIONAL6 Company Dr. Raymond W. Waldo Station Manager San Onofre December 31, 2002 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555-0001
Subject:
Docket No. 50-361 Licensee Event Report No. 2002-006 San Onofre Nuclear Generating Station, Unit 2 Gentlemen:
This submittal provides a Licensee Event Report (LER) for an occurrence involving the actuation of the Reactor Protection System when Unit 2 experienced a loss of main feedwater to the steam generators.
Any actions listed are intended to ensure continued compliance with existing commitments as discussed in applicable licensing documents; this LER contains no new commitments. If you require any additional information, please so advise.
Sincerely, LER No. 2002-06 cc:
E. W. Merschoff, Regional Administrator, NRC Region IV C. C. Osterholtz, NRC Senior Resident Inspector, San Onofre Units 2 & 3 P.O. Box 128 1*
San Clemente, CA 92672-0128 949-368-8725/PAX 88725 Fax 949-368-6183 waldorw@songs.sce corn
Abstract
On 111212002 at 0316 PST, with the Unit 2 reactor at 100% power, the Reactor Protection System (RPS) tripped the Unit A main Feedwater (FW) controller failed; the FW regulating valve (2FV1111) began to close; and the water level in steam generator 89 decreased to the low-level trip set point. 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 in accordance with 10 CFR 50.72(b) and is providing this follow-up report in accordance with 10 CFR 50 73(a)(2)(iv)(A)
SCE's cause evaluation is ongoing. However, preliminary investigations indicate that the 2FC1 111 main FW controller card had a shorted low limit operational amplifier (Motorola, MLM301AG, date code 7432) This may be an age-related failure. This LER will be supplemented if this conclusion changes significantly. SCE replaced both Unit 2 main FW controller cards (2FC 11 1 and 2FC1 121) with new cards (even though 2FC1 121 tested satisfactorily) As a precautionary measure, the corresponding cards in Unit 3 have been scheduled for replacement 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 NRC FORM 366 (7-2001)U.S. NUCLEAR REGULATORY COMMISSION (7-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION 1 FACLITY NAME 2 DOCKET NUMBER 6 LER NUMBER PAGE (3)
Sn YR NSEQUENTIAL REV No (
San Onofre Nuclear Generating Station (SONGS) Unit 2 05000-361 1NUMBER I
12 of 2 I 2002 1
- - 006 -
I00 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 (2FVI1I1) {EIIS Component Code FCVI 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 2FC1 111 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 (2FC 11 1 and 2FC1 121) with new cards (even though 2FC1 121 tested satisfactorily). As a precautionary measure, the corresponding cards in Unit 3 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.OE-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 3FC1 121 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.