05000461/LER-2009-004, Regarding Steam Leak Due to Valve Packing Torque, Resulting in Required Plant Shutdown
| ML093350529 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 11/20/2009 |
| From: | Kearney F Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SRRS 5A.108, U-603929 LER 09-004-00 | |
| Download: ML093350529 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4612009004R00 - NRC Website | |
text
Exelon.
Nuclear Clinton Power Station 8401 Power Road Clinton, IL 61727-9351 10 CFR 50.73 SRRS 5A.108 U-603929 November 20, 2009 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. 50-461
Subject:
Licensee Event Report 2009-004-00 Enclosed is Licensee Event Report (LER) No. 2009-004-00: Steam Leak Due to Valve Packing Torque Results in Required Unit Shutdown. This report is being submitted in accordance with the requirements of 10 CFR 50.73 There are no regulatory commitments contained in this letter.
Should you have any questions concerning this report, please contact D. E. Hupp, at (217)-
937-2509.
Respectully, F. A. Kearney Site Vice President Clinton Power Station RSF/blf
Enclosures:
Licensee Event Report 2009-004-00 cc:
Regional Administrator - NRC Region III NRC Senior Resident Inspector - Clinton Power Station Office of Nuclear Facility Safety - IEMA Division of Nuclear Safety
NW 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 information collection.
- 13. PAGE Clinton Power Station, Unit 1 05000461 1 OF 4
- 4. TITLE Steam Leak Due to Valve Packing Torque Results in Required Plant Shutdown
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR I None 05000 NUMBER NO. I__________I_______________________
FACILITY NAME DOCKET NUMBER 09 30 09 2009 004 -00 11 20 09 jNone 05000
- 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)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii) 3 El 20.2201(d)
[I 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
[1 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
[I 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
E] 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El50.73(a)(2)(iii)
El-50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
[E 20.2203(a)(2)(iii) 0l 50.36(c)(2)
El 50.73(a)(2)(v)(A)
[1 73.71(a)(4) 0.00 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) 0 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in Cooling (RCIC) [BN] steam line inboard isolation valve [ISV] 1 E51-F063. The steam leakage from valve 1 E51 -F063 was verified to be a packing leak. No other significant steam leaks were identified during the initial or subsequent walkdowns of the drywell.
No other inoperable equipment or components directly affected this event.
Issue Report 972235 was initiated to investigate and correct this issue.
CAUSE OF EVENT
This event has two root causes. The first root cause is the valve stem of valve 1 E51 -F063 is off-center with the stuffing box with potential to cause packing side loading and accelerated loss of packing load. While packing the valve during this unit shutdown, maintenance technicians identified the stem was off-center with the stuffing box. Further scale measurements indicated the off-set condition was present in the same direction at the yoke-to-operator interface. If a valve stem is not centered in the stuffing box, when the valve is stroked, the stem will side load the packing set. Side loading will cause uneven stresses in the packing set and can be a contributor to accelerated packing failure. Additional detailed measurements should be obtained to confirm and correct the source for the off-set condition. In 2004, packing was installed in 1 E51 -
F063 while the valve bonnet was in the shop before the bonnet was installed on the valve. If the source of the condition is the valve operator alignment, then the condition could not have been identified in 2004 when the packing was installed since the operator was not in place during that packing activity.
The second root cause is work instructions did not require the packing in 1 E51 -F063 to be torqued to the as-left value from the original installation. In February 2004, the valve was modified to eliminate the leak-off line to provide more reliable valve stem packing due to the chronic valve packing leakage the valve has experienced. An additional work order was performed for this valve in February 2006 to verify packing torque based on a recommendation from another Exelon site to confirm the packing torque was within tolerance after one fuel cycle. Work instructions for the torque confirmation activity in 2006 did not include information on the specific torque value for the packing. The instructions were "do not exceed torque values listed on the Journeyman Worksheet," (that is, 32 to 39 foot-pounds). Using the plus or minus 2 foot-pounds tolerance of the torque wrench, the as-left value was 30 foot-pounds versus the as-found value of 29 foot-pounds.
SAFETY ANALYSIS
This event is reportable under the provisions of 10 CFR 50.73(a)(2)(i)(A) due to completion of the nuclear plant shutdown required by plant TS 3.4.5.
This event had minimal safety significance. The reactor was shut down safely and maintained in a safe shut down condition. The packing leak was less than the total allowed leakage of 30 gpm over the previous 24-hour period provided in the limitations of TS 3.4.5. Although the steam leak added heat load to the ventilation system and condensed water volume to the floor drain system, the leakage was within the design capabilities of the reactor coolant system inventory makeup, the drywell floor drain system, and the drywell ventilation system. There was no release of radioactive material to the environment. Operators continually monitored the leakage during this event.
This event report does not identify any safety system functional failures.
CORRECTIVE ACTION
The packing in valve 1 E51 -F063 was replaced and the proper torque was applied.
The cause for valve 1 E51 -F063 valve stem being off-center with the stuffing box will be investigated and corrected.
Other valves were modified in February 2004 to eliminate the leak-off lines to provide more reliable valve stem packing. The packing torque applied to these additional valves will be verified and corrected as necessary.
PREVIOUS OCCURRENCES
None
COMPONENT FAILURE DATA
Manufacturer: Anchor Darling Valve Company Nomenclature: 8-inch, 600-pounds per square inch, Flex Wedge Gate Valve Manufacturer Model Number: 93-14582PRINTED ON RECYCLED PAPER NRIC FORM 366A (9-2007)
PRINTED ON RECYCLED PAPER