05000305/LER-2007-001, Regarding Reactor Trip During Turbine Trip Mechanism Testing
| ML070850082 | |
| Person / Time | |
|---|---|
| Site: | Kewaunee  |
| Issue date: | 03/12/2007 |
| From: | Hartz L Dominion, Dominion Energy Kewaunee |
| To: | Document Control Desk, NRC/NRR/ADRO |
| References | |
| 07-0176 LER 07-001-00 | |
| Download: ML070850082 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(B) |
| 3052007001R00 - NRC Website | |
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- -0Dominion Dominion Energy Kewaunee, Inc.
N490 Highway 42, Kewaunee, WI 54216-9511 MAR 1 2 2007 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.
07-0176 KPS/LIC/RS: RO Docket No.
50-305 License No. DPR-43 DOMINION ENERGY KEWAUNEE, INC.
KEWAUNEE POWER STATION LICENSEE EVENT REPORT 2007-01
Dear Sirs:
Pursuant to 10 CFR 50.73, Dominion Energy Kewaunee, Inc., hereby submits the following Licensee Event Report applicable to Kewaunee Power Station.
Report No. 50-305/2007-01 This report has been reviewed by the Plant Operating Review Committee and will be forwarded to the Management Safety Review Committee for its review.
If you have any further questions, please contact Mr. Richard Sattler at (920) 388-8121.
Very truly yours, Leslie N. Hartz' Site Vice President, Kewaunee Power Station Attachment Commitments made by this letter: NONE 5~2~
Serial No. 07-0176 Page 2 of 2 cc:
Regional Administrator, Region III U.S. Nuclear Regulatory Commission 2443 Warrenville Road Suite 210 Lisle, IL 60532-4352 Mr. R. F. Kuntz Project Manager U.S. Nuclear Regulatory Commission Mail Stop 0 7D1A Washington, D. C. 20555 NRC Senior Resident Inspector Kewaunee Power Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 6-30-2007 (6-2004)
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LICENSEE EVENT REPORT (LER)
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FACILITY NAME (1)
DOCKET NUMBER (2)
PAGE (3)
Kewaunee Power Station 05000305 1 of 3
TITLE (4)
Reactor Trip During Turbine Trip Mechanism Testing EVENT DATE (5)
LER NUMBER (6)
REPORT DATE (7)
OTHER FACILITIES INVOLVED (8)
SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MO DAY YEAR YEAR NUMBER NO MO DAY YEAR 1
12 2007 2007 001 00 03 12 2007 FACILITY NAME DOCKET NUMBER OPERATING N
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR (Check all that apply) (11)
MODE (9) 20.2201 (b) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)
POWER 93.7%
20.2201 (d) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(x)
LEVEL (10) 20.2203(a)(1) 50.36(c)(1)(i)(A)
X 50.73(a)(2)(iv)(A) 73.71(a)(4) 20.2203(a)(2)(i) 50.36(c)(1 )(ii)(A) 50.73(a)(2)(v)(A) 73.71 (a)(5) 20.2203(a)(2)(ii) 50.36(c)(2) 50.73(a)(2)(v)(B)
OTHER 20.2203(a)(2)(iii) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C)
Specify in Abstract below or in 20.2203(a)(2)(iv) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) 20.2203(a)(2)(v) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(C) 50.73(a)(2)(viii)(A) 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(B)
LICENSEE CONTACT FOR THIS LER (12)
NAME TELEPHONE NUMBER (Include Area Code)
Richard Sattler (920) 388-8121 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
MANU-REPORTABLE MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX SUPPLEMENTAL REPORT EXPECTED (14)
EXPECTED MONTH DAY YEAR YES (If yes, complete EXPECTED SUBMISSION DATE).
X NO DATE (15)U ABSTRACT At 10:39 on 1/12/2007, with the reactor at 1660MWt (93.7%), while performing a turbine mechanical trip test, the turbine and reactor tripped due to low auto stop oil pressure. MS-201 B1, Reheat Steam to MSR B1, failed to close, which resulted in additional RCS cooldown to 536 degrees F. Per contingency procedures, action was taken to isolate the reheat steam, which halted the cooldown, and Tave was restored to 547 degrees F. The additional cooldown resulted in letdown isolation on low pressurizer level. Feedwater isolated and auxiliary feedwater initiated, as designed, due to low-low level in the steam generators. No other safeguards systems actuated during the transient.
The direct cause was the loss of auto stop oil pressure to the interface valve that resulted in a turbine-reactor trip. No root cause could be conclusively identified. Foreign material on a valve-seating surface was identified as a probable cause.
This event is being reported under 10 CFR 50.73(a)(2)(iv)(A) as an event or condition that resulted in automatic actuation of the reactor protection system and the auxiliary feedwater system.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME 1)
DOCKET NUMBER (2 LER NUMBER (6)
PAGE (3)
YEAR I
SEQUENTIAL REVISION Kewaunee Power Station 05000305 NUMBER NUMBER 2 of 3 2 0 0 0 0 1 0 0 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
Event Description
Kewaunee Power Station (KPS) was operating at approximately 93.7% steady state power. At 10:15, station operators began performance of SP-54-063, Turbine Trip Mechanism Tests, at the main turbine [TRB]
pedestal. During performance of this task auto stop oil pressure was lost resulting in a turbine-reactor trip at 10:39. Both reactor trip breakers [BKR] opened.
Following the trip, MS-201 B1, Reheat Steam to MSR B1, [ISV] did not close, (a repeat valve failure), which resulted in additional cooldown to 536 degrees F RCS Tave. The additional cooldown resulted in letdown isolation due to low pressurizer level. Feedwater [SJ] isolated and auxiliary feedwater [BA] initiated, as designed, due to low-low level in the steam generators. No other safeguards systems actuated during the transient.
Per contingency procedures, manual action was taken to isolate the reheat steam [SB], which halted the cooldown, and Tave was restored to 547 degrees F. Charging [CB] was taken to manual to restore pressurizer level and letdown flow. LD-10 was taken to manual during the restoration of letdown flow.
Event Analysis
This event is being reported under 10 CFR 50.73(a)(2)(iv)(A) as an event or condition that resulted in automatic actuation of the reactor protection system and the auxiliary feedwater system.
In the Main Turbine [TA] steam admission system, any steam path has two valves in series which are controlled by independent systems. The high-pressure oil [TG] system that actuates the steam valves is completely independent of the low-pressure lubrication oil [TD]. Any loss of oil pressure or power supply causes closure of the steam valves [V]. The auto-stop oil is dumped to drain when any one of the protective trip devices is actuated. Independent reactor trip signals [JC] will actuate the solenoid trip in the emergency trip device and dump auto-stop oil to drain.
MS-201 B1 failed to close following this trip. It had also failed to close following the reactor trips on 10/30/2006 and 11/10/2006. This valve is not a safety-related component and has no safety-related support functions.
Following the 10/30 trip, the cause of MS-201 B1 failing to close was determined to be a galled valve plug, showing the bottom bonnet was not installed squarely. The valve stem was replaced, the valve plug was polished, and the packing was replaced.
Following the 11/10 trip, the cause of MS-201 B1 failing to close was determined to be replacement bushings which eliminated the recessed area of the bushing and extended its length from 1.5 inches to 2 inches.
MS-201 B1 was reassembled with the old style bushings.
During troubleshooting following this trip, AOV diagnostics testing was performed on MS-201 B1 (and MS-201A1 for comparison), but the results were inconclusive.
Maintenance was performed to shorten the stroke length of MS-201 B1 by 1/4 inch. Several other courses of action were considered, but, after comparing the AOV diagnostic testing of MS-201A1 and MS-201 B1, a determination was made to forgo any additionalU.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
Y SEQUENTIAL REVISION Kewaunee Power Station 05000305 YEAR NUMBER NUMBER 3 of 3 2007 001 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) maintenance on MS-201 B1 during the forced outage. The issue was made into an Operator Work Around and procedure changes were made to address the possibility of MS-201 B1 not closing on future trips.
A post-trip event review was performed and, following troubleshooting, the plant was restarted at 17:36 on 1/14/07.
The direct cause of the trip was determined to be the loss of auto stop oil pressure to the interface valve that resulted in a turbine-reactor trip. No root cause could be conclusively identified. Foreign material on a valve-seating surface was identified as a probable cause.
Safety Significance
This event did not create any plant safety issues or personnel injury/safety issues. The control room operating crew responded appropriately to the plant trip addressing all unexpected plant responses to the transient.
Although MS-201 B1 failed to close when required, compensatory actions were taken and the plant was successfully shut down.
Cause
No root cause could be conclusively identified. Foreign material on a valve-seating surface was identified as a probable cause.
Corrective Actions
The control room operating crew responded appropriately to the plant trip addressing all unexpected plant responses. Immediately following the trip, the DNAP-2000 Troubleshooting Plan was initiated for the auto stop oil problem. The stroke length of MS-201 B1 was shortened by 1/4 inch.
Since no root causes were identified for the trip, no root cause corrective actions exist. For the foreign material probable cause, the following corrective actions are being implemented in accordance with a Change Management Plan:
Fleet FME procedure MA-AA-102 "Dominion Foreign Material Process" Fleet procedure MA-AA-1001 "Dominion Supplemental Personnel Process" (to enhance supplemental worker standards on FME)
Training and qualifications requirements of MA-AA-102 "Dominion Foreign Material Process"
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