05000397/LER-2010-002, For Columbia Generating Station, Regarding LPCS Minimum Flow Valve Failed to Open Due to Premature Fuse Failure at the Solder Joint
| ML110550189 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 02/17/2011 |
| From: | Sawatzke B Energy Northwest |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GO2-11-035 LER 10-002-00 | |
| Download: ML110550189 (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 |
| 3972010002R00 - NRC Website | |
text
Bradley J. Sawatzke E
E GColumbia Generating Station P.O. Box 968, PE08 ERichland, WA 99352-0968 NORTHW EST 509.377.4300 1 F.
509.377.4150 bjsawatzke@energy-northwest.com February 17, 2011 G02-11-035 10 CFR 50.73 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001
Subject:
COLUMBIA GENERATING STATION, DOCKET NO. 50-397 LICENSEE EVENT REPORT NO. 2010-002-00
Dear Sir or Madam:
Transmitted herewith is Licensee Event Report No. 2010-002-00 for Columbia Generating Station. This report is submitted pursuant to 10 CFR 50.73(a)(2)(v)(D). The enclosed report discusses items of reportability and corrective actions taken related to the low pressure core spray minimum flow valve failure to open due to premature fuse failure at the solder joint. This discrepant condition was discovered on December 20, 2010.
There are no commitments being made to the NRC herein. If you have any questions or require additional information, please contact Mr. K. D. Christianson at (509) 377-4315.
Respectfully, B. J. Sawatzke Vice President, Nuclear Generation & Chief Nuclear Officer
Enclosure:
Licensee Event Report 2010-002-00 cc: NRC Region IV Administrator NRC NRR Project Manager NRC Senior Resident Inspector/988C R.N. Sherman - BPA/1399 W.A. Horin - Winston & Strawn INPO Records Center
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may di t/h ts for each block) not conduct or sponsor, and a person is not required to respond to, the gitscaraters information collection.
- 3. PAGE Columbia Generating Station 05000 397 1
OF 4
- 4. TITLE LPCS minimum flow valve failed to open due to premature fuse failure at the solder joint
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEUMENILREVO MONTH DAY YA 50 NUMBER NO.
YER05000 FACILITY NAME DOCKET NUMBER 12 20 2010 2010 2
0 02 18 2011 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
I
]
20.2201(b) r] 20.2203(a)(3)(i)
E] 50.73(a)(2)(i)(C) 5 50.73(a)(2)(vii)
E] 20.2201(d) 5 20.2203(a)(3)(ii) 5 50.73(a)(2)(ii)(A) 5 50.73(a)(2)(viii)(A)
E] 20.2203(a)(1)
[]
20.2203(a)(4) 5 50.73(a)(2)(ii)(B) 5 50.73(a)(2)(viii)(B) 5 20.2203(a)(2)(i) 5 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 5 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL EJ 20.2203(a)(2)(ii) 5 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A)
L] 50.73(a)(2)(x) 1E 20.2203(a)(2)(iii) 5 50.36(c)(2) 5 50.73(a)(2)(v)(A)
I]
73.71(a)(4) 100 [o 20.2203(a)(2)(iv) 5 50.46(a)(3)(ii) 2 50.73(a)(2)(v)(B)
L] 73.71(a)(5) o] 20.2203(a)(2)(v)
E] 50.73(a)(2)(i)(A) 5 50.73(a)(2)(v)(C) 5] OTHER E] 20.2203(a)(2)(vi)
I]
50.73(a)(2)(i)(B)
- ]
50.73(a)(2)(v)(D)
Specify in Abstract below or in
Immediate Corrective Actions
Immediate corrective actions consisted of protecting the alternate sources of emergency core cooling system (ECCS) injection/spray including residual heat removal (RHR), which performs the LPCI function, and HPCS. The supporting systems of SSW and the diesel generators [EK] were also protected.
Assessment of Safety Consequences
The safety functions for LPCS are to provide inventory makeup and spray cooling during large breaks in the reactor coolant system that uncover the core. All remaining ECCS subsystems were operable and at no time did this event result in the loss of a safety function. The low pressure injection function was not challenged due to all three loops of RHR system LPCI mode being operable while the core spray function was satisfied by the operable HPCS system.
This event did not pose a threat to the health and safety of the public. The TS Required Action for LCO 3.5.1 Condition A, one low pressure ECCS injection/spray subsystem inoperable, was complied with by restoring the LPCS system to operable within the allowed completion time. In addition, the TS Required Actions for LCO 3.6.1.3 Condition C and LCO 3.3.3.1 Condition A were completed within the required completion time. Thus, Columbia Generating Station was never in a condition prohibited by TS.
This event is being reported under 10 CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident for a single train system. The minimum flow valve supports LPCS operability by providing a flow path to prevent pump damage during situations where the LPCS pump has been started in response to a transient but reactor vessel pressure is not low enough to allow LPCS injection.
Historically, when LPCS has been inoperable at Columbia Generating Station, it was not considered to be reportable as a single train system. This treatment is consistent with the plant safety analysis and the associated system and safety function groupings which do not identify LPCS as a single train system. There are two pertinent groupings in the safety analyses which are aligned with the credited safety functions of LPCS. The two groupings are the low pressure injection system function (combined with LPCI), and a core spray system function (combined with HPCS). Industry precedent has been consistent with the historical position. However, recent NRC interpretations have considered safety function at the lowest system level, which results in LPCS being considered a single train performing a safety function.
Causes
The direct cause of LPCS-FCV-11 failing to open as expected was a loss of power that occurred when the overload elements cleared within the three line power fuses. Possible reasons to fail or trigger the overload elements in the fuses are binding within the flow control valve, binding within the motor operator, sticking or dirty contacts within the reversing starter, or a premature failure of a fuse. Once the fuses were replaced, normal operation was restored with no observed binding of the valve or motor operator or abnormalities with the reversing starter. Diagnostic testing of the motor operator was completed which showed that the amps drawn by the motor were under the fuse manufacturer's time-current curve.
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REV NUMBER NO.
4 OF 4
2010 002 00 The failed fuses had been installed approximately two years ago but were 12 years old. An examination of the three failed fuses revealed a poor solder joint in the trigger assembly in one of the failed fuses. The apparent cause of this event is attributed to premature failure of one of the three installed power line fuses from momentary inrush current at a current value under the fuse curve. This conclusion is based on the examination of the fuse trigger solder which displayed evidence of cold unattached solder and trapped resin flux in the trigger solder joint. Also, no heating damage of the PET (polyethylene terephthalate) insulating spool was observed. Two of the fuses obviously failed from current overload on the resulting failure of the first fuse. These two fuses were determined to have functioned normally.
Initially, this event was considered to be not reportable until discussions were held with the NRC Resident Inspector and Regional staff. Upon determination of reportability of this event, a prompt notification was made to the NRC in accordance with 10 CFR 50.72(b)(3)(v)(D) via Event Notification#46604. As such, the event investigation was conducted as an apparent cause rather than a root cause evaluation. A root cause analysis is in progress but has not yet been completed for this event.
If new information is gained, which invalidates the stated cause or corrective actions, this report will be revised to incorporate the new information.
Further Corrective Actions The fuses that failed were Cooper/Bussmann Fusetron dual-element, time-delay, current limiting, 600 Volt, 1.25 Amp fuses (model FRS-R-1-l/4). Since the fuse overload element was found to be triggered, the operating history of the LPCS-FCV-I1 motor operator and starter was investigated: 1) In March 2008, a diagnostic test of the motor operator was completed satisfactorily with no abnormalities noted. 2) In March 2009, an inspection of the reversing starter was completed satisfactorily. The fuses were replaced at this time. 3) In April 2010, the motor operator was lubed and inspected with no problems found. 4) The last quarterly LPCS surveillance test prior to the event was completed satisfactorily on September 29, 2010.
Warehouse and tool crib stock of the Bussmann FRS-R-1-1/4 fuses from the same GI0 date code lot as that of the three failed fuses were quarantined and segregated to prevent further installation of suspect fuses. This lot of fuses was received at Columbia Generating Station in 2000. Enhancements to the Bussmann fuse dedication process to require additional receipt inspections and testing are planned.
A search was performed of all safety-related ECCS motor operated valves which may possibly contain the same Bussmann 1.25 Amp fuses from the same lot. Inspections were performed and no additional fuses of the same lot were found to be installed.
Similar Events
No similar events have been reported by Columbia Generating Station.