05000482/LER-2009-001, For Wolf Creek, Regarding Reactor Protection System Actuation and Reactor Trip Due to Main Feedwater Regulating Valve Failing Closed
| ML091810707 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 06/24/2009 |
| From: | Matthew Sunseri Wolf Creek |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| WO 09-0014 LER 09-001-00 | |
| Download: ML091810707 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(iv), System Actuation |
| 4822009001R00 - NRC Website | |
text
W0LF CREEK UCLEAR OPERATING CORPORATION Matthew W. Sunseri Vice President Operations and Plant Manager June 24, 2009 WO 09-0014 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555
Subject:
Docket No. 50-482: Licensee Event Report 2009-001-00, Reactor Protection System Actuation and Reactor Trip due to Main Feedwater Regulating Valve Failing Closed Gentlemen, The enclosed Licensee Event Report (LER) 2009-001-00 is being submitted pursuant to 10 CFR 50.73(a)(2)(iv)(A) regarding an Engineered Safety Features Actuation and Reactor Trip at Wolf Creek Generating Station.
Commitments made by Wolf Creek Nuclear Operating Corporation in the enclosed LER are identified in the Attachment to this letter.
If you have any questions concerning this matter, please contact me at (620) 364-4008, or Mr.
Richard D. Flannigan, Manager Regulatory Affairs at (620) 364-4117.
Sincerely, Matthew W. Sunseri MWS/rlt Attachment Enclosure cc:
E. E. Collins (NRC), w/a, w/e V. G. Gaddy (NRC), w/a, w/e B. K. Singal (NRC), w/a, w/e Senior Resident Inspector (NRC), w/a, w/e P.O. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 An Equal Opportunity Employer M/F/HC/VET A
Attachment to WO-09-0014 Page 1 of 1 LIST OF COMMITMENTS The following table identifies those actions committed to by Wolf Creek Nuclear Operating Corporation in this document. Any other statements in this letter are provided for information purposes and are not considered regulatory commitments. Please direct questions regarding these commitments to Mr.
Richard Flannigan, Manager Regulatory Affairs at Wolf Creek Generating Station, (620) 364-4117.
REGULATORY COMMITMENT DUE DATE All remaining Westinghouse 7300 card frame fuse holders will March 5, 2010
.be replaced in Refuel Outage 17 with all actions completed following the outage.
All power supply fuse holders will be replaced in Refueling July 8, 2011 Outage 18 with all actions completed following the outage.
An annunciator alarm will be added to the Main Control Board July 1, 2011 for the Westinghouse 7300 card frame fuse holders.
Procedural guidance will be provided that any fuse holder October 30, 2009 measured at or above 60 degrees Centigrade would require replacement of the fuse holder.
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may (See reverse for required number of not conduct or sponsor, and a person is not required to respond to, the digits/characters for each block) information collection.
- 3. PAGE WOLF CREEK GENERATING STATION
,. 05000 482 1 OF 4
- 4. TITLE Reactor Protection System Actuation and Reactor Trip due to Main Feedwater Regulating Valve Failing Closed
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIALI REV MONTH DAY FACILITY NAME DOCKET NUMBER NUMBER NO.
I 05000 I FACILITY NAME DOCKET NUMBER 04 28 2009 2009 001 00 06 24 2009 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
[] 20.2201(b)
El 20.2203(a)(3)(i)
E] 50.73(a)(2)(i)(C)
E] 50.73(a)(2)(vii)
E] 20.2201(d)
El 20.2203(a)(3)(ii)
[]
50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
E] 20.2203(a)(1)
E] 20.2203(a)(4)
E] 50.73(a)(2)(ii)(B)
[
50.73(a)(2)(viii)(B)
_E 20.2203(a)(2)(i)
[] 50.36(c)(1)(i)(A)
E] 50.73(a)(2)(iii)
E] 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL
[=
20.2203(a)(2)(ii)
[] 50.36(c)(1)(ii)(A)
[] 50.73(a)(2)(iv)(A)
[]
50.73(a)(2)(x) 10 20.2203(a)(2)(iii)
E] 50.36(c)(2)
El 50.73(a)(2)(v)(A)
E] 73.71 (a)(4) 100 E] 20.2203(a)(2)(iv)
[]
50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
E] 73.71 (a)(5)
E] 20.2203(a)(2)(v)
E] 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
E] OTHER E] 20.2203(a)(2)(vi)
E] 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in
BACKGROUND:
Steam generator (SG) [EIIS Code: SG] water level is normally controlled automatically using circuitry that compares existing SG level with a programmed reference level. The result of this comparison, or "level error," generates a signal to.the Main Feedwater System JEllS Code: SJ] regulating control valve (MFRV) for the respective SG, which results in adjustments in the MFRV position. Upon loss of power, the MFRV fails to its designed safe closed position.
PLANT CONDITIONS PRIOR TO EVENT:
MODE-1 Power - 100 percent Normal Operating Temperature and Pressure
EVENT DESCRIPTION
On April 28, 2009 at 3.27 p.m. Central Daylight Time (CDT), Wolf Creek Generating Station (WCGS) automatically shut down from operating at approximately 100 percent power because the "B" Main Feedwater Regulating Valve (MFRV), which provides water to the "B" steam generator (SG), failed to the closed position. Overheating of the fuses due to degraded fuse holders in the Westinghouse 7300 card frame caused the primary and secondary card frame fuses to fail, which disrupted the control power to the "B" MFRV. In response to a loss of control power, the "B" MFRV closed to its designed safe position. As the water level decreased in the "B" SG, the reactor tripped at the low-low SG water level set point of 23.5 percent. As a result of the card frame fuse failures, power was also disrupted to indicators for pressurizer surge temperature, pressurizer liquid temperature, pressurizer pressure high and pressurizer safety temperature. Power was restored at 9:57 p.m. CDT on April 28, 2009.
At the time of the trip, all control rods inserted into the core. The Reactor Protection System (RPS) and the Engineered Safety Features (ESF) Systems performed as required. Main feedwater was isolated and motor-driven and turbine-driven auxiliary feedwater pumps started as expected.
All equipment functioned as expected except Intermediate Range Channel NI-36, which prevented clearing the P-6 permissive that would have allowed automatic re-energization of the Source Range channels. The Source Range channels were re-energized manually. Intermediate Range Channel NI-36, a compensated ion chamber detector, was found to be under-compensated. This instrument was replaced in the last refueling outage and had not had an opportunity to have its compensation voltage checked under full gamma radiation exposure. Steam emitted from the relief valve on the Steam Generator Blowdown Tank actuated fire alarms in the Turbine Building but no fire occurred.
No personnel were injured. Reactor operators completed the emergency procedures network at 4:05 p.m. CDT on April 28, 2009. Reactor start-up commenced at 11:29 p.m. CDT on April 30, 2009.
In July 1995, Westinghouse Infogram IG-95-004 was sent to the industry because of an overheating issue identified with Littelfuse card frame fuse holders on the 7300 system. WCGS evaluated the Infogram and themography showed no elevated temperatures above 85 degrees Centigrade. Corrective actions included establishing a
conditioned-based preventive maintenance activity and replacing the fuse holders on an as-needed basis with a Bussman fuse holder, as per the Westinghouse recommendation. The preventive maintenance activity put in place was determined to be less that adequate to detect the degrading condition of the fuse holders.
BASIS FOR REPORTABILITY:
The reactor trip and subsequent actuation of Engineered Safety Features (ESF) described in this event is reportable per 10 CFR 50.73(a)(2)(iv)(A), which requires reporting of "Any event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B) of this section." Paragraph (B)(1) of 10 CFR 50.73(a)(2)(iv) includes "Reactor protection system (RPS) including: reactor scram or reactor trip." Paragraph (B)(6) of 10 CFR 50.73(a)(2)(iv) includes "PWR auxiliary or emergency feedwater."
ROOT CAUSE:
WCGS instituted less than adequate actions to address known deficiencies of the Littelfuse fuse holders. Procedures did not require routine inspections of the indicating lights for the 7300 card frame fuses, or specify acceptance criteria for the 7300 system card frame fuse holders. Thermography was being used, but there were no specific criteria for card frame fuse holders.
Littelfuse fuse holder model number 342038A was used in an application for which it was not designed. Overheating of the Littelfuse fuse holders subjected the fuses to temperatures as high as 119.9 degrees Centigrade and was most likely caused by high resistance at the riveted connection and spade terminations. The maximum temperature rating of the fuses is 125 degrees Centigrade.
CORRECTIVE ACTIONS
Westinghouse recommends replacing the Littelfuse fuse holder model number 342038A with a Bussman HKP-CC fuse holder, which is rated for higher current and higher temperatures than the Littelfuse fuse holder. Following the shutdown, all fuse holders in the Westinghouse 7300 system card frames were analyzed using thermography and a total of 14 fuse holders and fuses were replaced.
Other bayonet-style fuse holders used in applications critical to nuclear safety or plant operations were assessed and repaired or replaced if temperatures greater than 75 degrees Centigrade were identified. No other degraded fuse holders were identified during this assessment.
All other Westinghouse 7300 card frame fuse holders will be replaced in Refuel Outage 17 with all actions completed by March 5, 2010. All power supply fuse holders will be replaced in Refueling Outage 18 with all actions completed by July 8, 2011.
Future use of the Littelfuse fuse holder model number 342038A has been prohibited for this application through supply controls.
By July 1, 2011 an annunciator alarm will be added to the Main Control Board for the Westinghouse 7300 card frame fuse holders to alert operators to failed primary or secondary card frame fuses.
Procedural guidance will be provided by October 30, 2009 that any fuse holder measured at or above 60 degrees Centigrade would require replacement of the fuse holder.
SAFETY SIGNIFICANCE
The Safety Significance of this event is low. This event is analyzed as reported in WCGS Updated Safety Analysis Report (USAR) section 15.2.7, "Loss of Normal Feedwater Flow." Results of the analysis show that a loss of normal feedwater does not adversely affect the core, the reactor coolant system, or the steam system, since the auxiliary feedwater capacity is such that reactor coolant water is not relieved from the pressurizer relief or safety valves.
There were no adverse effects on the health and safety of the public.
PREVIOUS OCCURRENCES
No failures of fuse holders have resulted in a previous reactor trip at Wolf Creek Generating Station. In February 2004, WCGS experienced a reactor trip due to a MFRV closure caused by the valve plug in the MFRV separating from the valve stem.