05000237/LER-2009-002, Regarding Unit 2 High Pressure Coolant Injection Suction Valve Fails to Close
| ML091470278 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/14/2009 |
| From: | Hanley T Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SVPLTR 09-0021 LER 09-002-00 | |
| Download: ML091470278 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 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)(iv)(A), System Actuation 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)(i)(B), Prohibited by Technical Specifications |
| 2372009002R00 - NRC Website | |
text
Exekrn Exelon Generation Company, LLC Dresden Nuclear Power Station 6500 North Dresden Road Morris, IL 60450-9765 www.exeloncorp.com Nuclear 10 CFR 50.73 SVPLTR # 09-0021 May 14, 2009 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit 2 Renewed Facility Operating License No. DPR-19 NRC Docket No. 50-237
Subject:
Licensee Event Report 237/2009-002-00, "Unit 2 High Pressure Coolant Injection Suction Valve Fails to Close" Enclosed is Licensee Event Report 237/2009-002-00, "Unit 2 High Pressure Coolant Injection Suction Valve Fails to Close" for Dresden Nuclear Power Station, Unit 2. This event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(C) and (D), "Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to: (C) control the release of radioactive material and (D) mitigate the consequences of an accident." There are no regulatory commitments contained in this submittal.
Should you have any questions concerning this report, please contact Mr. Stephen Taylor, Regulatory Assurance Manager, at (815) 416-2800.
Respectfully, Tim Hanley Site Vice President Dresden Nuclear Power Station Enclosure cc:
Regional Administrator - NRC Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the infnrmatinn cnllectinn.
- 3. PAGE Dresden Nuclear Power Station, Unit 2 05000237 1 OF 4
- 4. TITLE Unit 2 High Pressure Coolant Injection Suction Valve Fails to Close
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR N/A N/A
_I I
FACILITY NAME DOCKET NUMBER 03 15 2009 2009 002-00 05 14 2009 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
El 20.2201(b)
El 20.2203(a)(3)(i)
[E 50.73(a)(2)(i)(C)
[l 50.73(a)(2)(vii)
[1 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
[I 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL
[] 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
[I 50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x)
[I 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4) 100 El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71 (a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
Specify in Abstract below or in another signal from the control room to close. The valve was manually closed. The valve was last successfully closed electrically on January 13, 2009.
Subsequent troubleshooting and diagnostic testing were performed to determine the failure mode.
The electrical circuit was inspected up to and including the valve actuator. There were no issues identified with the electrical control power circuit. During the diagnostic testing, the valve did go fully closed when operated electrically. Subsequent testing showed reduced thrust and torque during each of the next couple of strokes. The diagnostic test identified an internal valve binding force during the close stroke for about the first 40% of travel. The open stroke was observed to be as expected with no evidence of binding. The diagnostic testing found no issues with the Limitorque actuator.
During the MOV diagnostic testing evolution several actions were taken to ensure the valve would achieve the full close stroke: (1) The process of numerous strokes appears to have lowered the magnitude of the binding forces from the initial value of greater than 4800 lbs to approximately 3000 lbs. (2) The stem was cleaned and lubricated to improve the efficiency of the actuator torque to stem thrust conversion. The as-found stem Coefficient of Friction (COF) was measured at 0.2 and after the lubrication activity it was improved to 0.06 COF. (3) The actuator output torque switch setting was increased to ensure sufficient margin between the actuator output and the binding forces. The valve was stroked a total of 12 times.
The valve was declared operable and capable to perform its design function after it was verified that all diagnostic test parameters for torque and thrust were within prescribed specifications. Monthly diagnostic testing will be performed on MOV 2-2301-6 to verify its continued operability until internal valve inspections are performed in the next Unit 2 refuel outage currently scheduled for November 2009.
It is hypothesized that when the valve failed to stroke, that the binding force was greater and/or the stem lubrication slightly less efficient, resulting in the actuator output exceeding the torque switch setting and subsequent failure to stroke. The root cause of this event will not be completed until internal valve inspections are performed in the next Unit 2 refuel outage currently scheduled for November 2009.
D.
Safety Analysis
The safety significance of the event is minimal. An evaluation was performed to determine the effect of this event on the operability of the HPCI and Torus during the time that it is hypothesized that MOV 2-2301-6 would not electrically close (i.e., January 13, 2009 to March 15, 2009). The evaluation concluded that HPCI would have operated long enough to fulfill its safety function. A review of the actual Torus water levels during this time frame identified that the Torus would not have exceed its structural design values during a postulated accident. Therefore, the consequences of this event had minimal impact on the health and safety of the public and reactor safety.
E.
Corrective Actions
MOV 2-2301-6 was returned to operable status.
Monthly diagnostic testing will be performed on MOV 2-2301-6 to verify its continued operability until internal valve inspections are performed in the next Unit 2 refuel outage currently scheduled for November 2009.
Dresden MOV diagnostic testing for MOV Program valves with horizontal disc and stem orientation that exhibit internal binding will be revised to ensure the testing frequency does not exceed six years.
Dresden MOV stem lubrication for MOV Program valves with horizontal disc and stem orientation that exhibit internal binding will be revised to ensure the lubrication frequency does not exceed two years.
F.
Previous Occurrences
A review of DNPS Licensee Event Reports (LERs) for the last three years did not identified any LERs associated with failure of valve closure due to internal binding.
G.
Component Failure Data
16" Crane Class 150 cast steel wedge gate valve with flanged endsPRINTED ON RECYCLED PAPERPRINTED ON RECYCLED PAPER