05000456/LER-2009-002, Regarding Safety Injection System Containment Sump Isolation Valve 1518811B Failed to Stroke Full Open Due to Torque Switch Assembly Corrosion
| ML092370590 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 08/24/2009 |
| From: | Shahkarami A Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BW090080 LER 09-002-00 | |
| Download: ML092370590 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(viii)(A) 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 |
| 4562009002R00 - NRC Website | |
text
wwwexeloncol'p.com Nuclear 3S'UC South Rt 53 Suite 84 Brace",:'ille, lL 60,4°7 August 24, 2009 BW090080 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Unit 1 Facility Operating License No. NPF-72 NRC Docket No. STN 50-456 10 CFR 50.73
Subject:
Licensee Event Report 2009-002 Safety Injection System Containment Sump Isolation Valve 1S188118 Failed to Stroke Full Open Due to Torque Switch Assembly Corrosion The enclosed Licensee Event Report (LER) is being submitted in accordance with 10 CFR 50.73, "Licensee event report system," paragraph (a)(2)(i)(B) as a condition prohibited by the plant's Technical Specifications (TS), and paragraph (a)(2)(v)(B) as a condition that prevented the fulfillment of a system's safety function. On June 24, 2009, safety injection system containment sump isolation valve 1SI8811 B failed to stroke full open during surveillance testing due to corrosion of the valve's torque switch assembly. 10 CFR 50.73(a) requires an LER to be submitted within 60 days following discovery of the event. Therefore, this report is being submitted by August 24, 2009.
There are no regulatory commitments contained in this letter. Should you have any questions concerning this SUbmittal, please contact Mr. David Gullatt, Regulatory Assurance Manager, at (815) 417-2800.
Respectfully, Amir Shahkarami Site Vice President Braidwood Station
Enclosure:
LER 2009-002-00
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 infnrm;:\\tinn r.nll~tinn
- 13. PAGE Braidwood Station, Unit 1 05000456 1
OF 4
- 4. TITLE Safety Injection System Containment Sump Isolation Valve 1518811 B Failed to Stroke Full Open Due to Torque Switch Assembly Corrosion
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR ISEQUENTIALIREV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR N/A N/A FACILITY NAME DOCKET NUMBER 06 24 2009 2009 002 00 08 24 2009 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 o 20.2201(b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C}
o 50.73(a)(2)(vii}
o 20.2201(d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii}(A) o 50.73(a)(2)(viii)(A) o 20.2203(a)(1) o 20.2203(a)(4) o 50.73(a)(2}(ii)(B) o 50.73(a)(2)(viii)(B) o 20.2203(a)(2)(i) o 50.36(c)(1 )(i)(A) o 50.73(a)(2)(iii) o 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL o
20.2203(a)(2)(ii}
o 50.36(c)(1)(ii)(A}
o 50.73(a)(2)(iv}(A) o 50.73(a)(2)(x) o 20.2203(a)(2)(iii) o 50.36(c)(2) o 50.73(a)(2)(v)(A) o 73.71(a)(4) 100 o 20.2203(a)(2)(iv) o 50.46(a)(3)(ii)
IZI 50.73(a)(2)(v)(B) o 73.71 (a)(5) o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C) o OTHER o 20.2203(a)(2)(vi}
IZI 50.73(a)(2)(i)(B) o 50.73(a)(2)(v)(D)
Specify in Abstract below or in conduit houses the control power cables and is routed from the electrical component compartment of 15188118 up to a cable tray where it terminates, open-ended at approximately a 45 degree angle, above the edge of an open cable tray (Cable Tray 1619G). A second cable tray (Cable Tray 1619F), is routed directly above Cable Tray 1619G. The configuration of the conduit is such that if water was spilled/sprayed on top of the upper cable tray, any runoff would be routed toward the opening of the conduit, providing a direct path to the electrical component compartment of the operator for 1518811 B. The conduit openings into the LS enclosures for MOVs are not required to be sealed per Environmental Qualification (EO) Binder number EQ-BB-027.
In an effort to determine the source of the water found in the L5 compartment, a sample of water was taken and analyzed by Chemistry. An isotopic analysis was performed. Water was not from the reactor coolant system.
Evaluation of potential non-contaminated water sources (containment penetrations) above the 1518811 B valve include systems Chilled Water (WO), Essential Service Water (SX), Make-up Water (WM) and spare penetrations used for steam generator sludge lancing (WM water). Investigation could not determine the exact source of the water found in the lS enclosure.
Based on the above analysis, the cause of this event was determined to be corrosion of the TS assembly, causing it to become non-functional, due to water intrusion into the LS compartment through the conduit.
b.
Safety Consequences
There were no safety consequences impacting the plant or public safety as a result of this event. The 1S18811B valve is closed during normal operations, and the issue was discovered during a planned valve stroke test of the 1S18811 B valve in accordance with Operating surveillances as required by Technical Specifications.
An evaluation was performed to determine past operability and whether the valve could pass design flow at the as-found opening travel position for the valve. Based on the failure mode, the valve would have been capable of opening to the bypass LS setting of approximately 38 percent open, and the valve was capable of passing the required ECCS recirculation flow at this partial opening position. Additional consequences of the inability of 1518811 B to achieve full open valve travel are the failure to meet the electrical interlock to manually open valve 15188048, Residual Heat Removal (RH) to Safety Injection (SI) crosstie valve, and 1CS009B Containment Spray (CS) Pump 1B Sump Suction valve from the main control room. The 1518804B is required to open in order to establish flow from the ECCS sump to the Hillntermediate Head ECCS pumps during the cold leg recirculation phase of ECCS. The 1CS009B is required to open in order to establish flow to the CS system from the containment recirculation sump.
The SI containment sump is required for loss of coolant accidents (LOCA) inside containment during the recirculation phase of the accident. Additionally, rupture of a control rod drive mechanism causing a rod cluster control assembly ejection accident results in a loss of reactor coolant inventory which the 51 system would be required to mitigate the accident. The SI containment sump isolation valves receive a signal to open when an 51 signal is actuated and the refueling water storage tank (RWST) reaches the RWST Low-2 setpoint. The CS system is required for a LOCA to minimize containment pressure and will also actuate during a feedwater or steam line break inside containment.
This event resulted in a safety system functional failure due to loss of interlock function of 1SI8811 B. The 1S18811 B is required to be fully open to make up electrical interlocks that allow opening of 1SI88048 and 1C5009B. The periods of time when the redundant train of RH and CS were unavailable result in a loss of safety function. The CS and EGCS systems would not be able to be realigned to take suction from the containment recirculation sump.
An evaluation is being performed to determine the bounding impact on the SI system, the plant's ability to mitigate events, and the associated change in risk. A supplement to this report will be provided with the conclusions of this evaluation and the associated risk impact.
~.
Corrective Actions
05000456 YEAR 2009 002 00 4
OF 4
Corrective actions taken include replacing the torque switch and limit switch finger bases, cleaning and drying the wires and limit switch compartment lenclosure on 1SI8811 B, and diagnostic testing. (Actions completed)
Additional corrective actions include:
Sealing the 1(2)SI8811 B conduits A walkdown of all the auxiliary building high and medium risk MOVs will be performed to determine if conduit openings exist similar to 1S18811B that would allow water intrusion from above.
Sealing of the identified conduits.
1:.
Previous Occurrences
There have been no similar Licensee Event Report events at Braidwood Station in the last three years.
G. Component Failure Data
Manufacturer Limitorque CorporationNomenclature Motor Operator Valve Actuator Model 5MB-2 Mfg. Part Number N/A PRINTED ON RECYCLED PAPER