05000362/LER-2002-003, From San Onofre Unit 3, Regarding Main Feedwater Pump Turbine Trip Results in Manual Actuation of Auxiliary Feedwater Systems
| ML023500036 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 12/11/2002 |
| From: | Scherer A Southern California Edison Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 02-003-00 | |
| Download: ML023500036 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3622002003R00 - NRC Website | |
text
SOUTHERN CALIFORNIA n EDIST ON An EDISON INTERNVATIONALIP Company A. Edward Scherer Manager of Nuclear Regulatory Affairs December 11, 2002 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555
Subject:
Docket No. 50-362 60-Day Report Licensee Event Report No. 2002-003 San Onofre Nuclear Generating Station, Unit 3 Gentlemen:
This submittal provides Licensee Event Report (LER) 2002-003 describing a manual actuation of the Auxiliary Feedwater System at Unit 3, which is reportable in accordance with 1 OCFR50.73(a)(2)(iv)(A).
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 advise.
Sincerely, Enclosure: LER No. 2002-003 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 San Clemente, CA 92674-0128 949-368-7501 Fax 949-368-7575 bX 9 A
Abstract
On October 16, 2002, Unit 3 plant operators were conducting Main Feedwater Pump Turbine (MFWPT) lube oil supply auto-start testing. Immediately after restoring the MFWPT lube oil supply to normal operation, MFWPT 3K006 tripped. Plant operators manually started the Auxiliary Feedwater (AFW) system and initiated a power reduction to approximately 75% power. The AFW system functioned correctly. This manual actuation of AFW is being reported in accordance with 10CFR50.73(a)(2)(iv)(A).
SCE's investigation is ongoing. To complete the cause evaluation, the MFWPT lube oil system and associated control systems will require disassembly. SCE will complete the cause evaluation following the next scheduled refueling outage and implement appropriate corrective actions at that time.
SCE concludes that this event was of very low to no safety significance; all safety systems functioned correctly.
NRC FORM 366 (7-2001)U.S. NUCLEAR REGULATORY COMMISSION
(-201)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION I
FAClTY NAME 2 DOCKET NUMBER I LER NUMBER PAGE 3)
SEQUENTIAL REV NO2f San Onofre Nuclear Generating Station (SONGS) Unit 3 00032 0
1
_2002 1-003 -
00 I
Plant:
San Onofre Nuclear Generation Station (SONGS) Unit 3 Reactor Vendor Combustion Engineering Event Date:
October 16, 2002 Event Time:
0152 PDT Unit 3 Mode 1
Power (percent):
100
BACKGROUND:
San Onofre Unit 3 has two turbine driven Main Feedwater Pumps (MFWP). Each pump normally provides about 50 percent of full-load feedwater flow to the two steam generators. A separate lube oil support system provides bearing oil, hydraulic oil, and control oil for each of the two MFWP/MFWPTs. Each lube oil system contains three pumps (2 AC, 1 DC). The AC-powered lube oil pumps can supply 100 percent of required oil. Typically, one AC-powered lube oil pump is in service with the other AC-powered pump serving as a standby that will start automatically if needed. This auto start feature is periodically tested locally. The DC pump auto-starts on low bearing oil pressure or loss of both AC pumps.
DESCRIPTION OF THE EVENT:
Early, on October 16, 2002, Unit 3 was at 100% power and plant operators (Utility, licensed and unlicensed) were conducting MFWPT protective device testing in accordance with procedure S023-2-1.1. During this work, operators performed an auto-start test of the standby Lube Oil Pump P109 for MFWPT K006. After confirming operation of both AC-powered lube oil pumps, at 0152 PDT, Operators stopped the Lube Oil Pump P122. Immediatelythereafter, MFWPT K006 tripped. In accordance with plant Abnormal Operating Instruction (AOl) S023-13-24, plant operators manually actuated the Emergency Feedwater Actuation System (EFAS). All three Auxiliary Feedwater (AFW) pumps started and provided feedwater to both Steam Generators (SG). Plant operators also initiated a power reduction to approximately 75% power in accordance with the AOI. This action allowed operators to secure feeding both steam generators by AFW at 0157, five minutes into the transient. At 0218, operators reset EFAS.
AT 0902 PDT on October 16, 2002, Southern California Edison (SCE) made an 8-hour telephone notification to the NRC Operations Center (Log No. 39292) in accordance with 1 OCFR50.72(b)(3)(iv)(A) for a valid Engineered Safety Features (ESF) actuation of EFAS. SCE is providing this 60-day follow up report in accordance with 10CFR50.73(a)(2)(iv)(A).U.S. NUCLEAR REGULATORY COMMISSION (7-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION I FACLfTY NAME
- 2. DOCKET NUM13ER 6 LER NUMBER PAGE t31 S
SEQUENTIAL REVNO San Onofre Nuclear Generating Station (SONGS) Unit 3 000321NUME I E O3 of 3 12002
- - 003 -
I 00
CAUSE OF THE EVENT
Based on engineering judgment, SCE believes that there are two possible causes of the MFWPT trip:
- 1. A spurious trip occurred due to an inadequately latched turbine trip reset mechanism, or
- 2. A low oil pressure condition occurred due to a malfunctioning oil pressure regulator or check valve.
Either of these conditions would have resulted in the observed MFWPT trip.
SCE's investigation is ongoing. To complete the cause evaluation, the MFWPT lube oil system and associated control systems will require disassembly. This work is planned for the next scheduled refueling outage (January, 2003). SCE will complete the cause evaluation and implement appropriate corrective actions at that time. A supplemental LER will be submitted if the cause is significantly different than noted above.
CORRECTIVE ACTIONS
Pending identification and repair of malfunctioning component(s), the MFWPT AC lube oil pump auto-start tests for all MFWPTs have been suspended (Unit 2 and Unit 3). Additionally, the on-line lockout and trip exercise testing for MFWPT K006 has been suspended.
SAFETY SIGNIFICANCE
The MFWPs are not essential for safe shutdown of the plant. The SONGS 2/3 UFSAR, Sections 15.2.2.5 and 15.10.2.2.5, credits the AFW system for maintaining an adequate heatsink during a transient in which an instantaneous and complete loss of feedwater occurs. The event reported herein, where one feedwater pump was lost and all safety systems functioned correctly is bounded by the UFSAR safety analysis identified above. Therefore, SCE concludes that this event was of very low to no safety significance.
ADDITIONAL INFORMATION
In the past three years, SCE has not reported any ESF actuations that resulted from feedwater transients.