05000281/LER-2005-001, Regarding Low Head Safety Injection Pump Breaker Failed to Close Due to Binding

Regarding Low Head Safety Injection Pump Breaker Failed to Close Due to Binding

ML051880043
Person / Time
Site:	Surry
Issue date:	06/24/2005
From:	Jernigan D Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
05-348 LER 05-001-00
Download: ML051880043 (7)

LER-2005-001, Regarding Low Head Safety Injection Pump Breaker Failed to Close Due to Binding

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
2812005001R00 - NRC Website

text

1 OCFR50.73 Virginia Electric and Power Company Surry Power Station 5570 Hog Island Road Surry, Virginia 23883 June 24, 2005 U. S. Nuclear Regulatory Commission Serial No.:

05-348 Attention: Document Control Desk SPS: TJN R2' Washington, D. C. 20555-0001 Docket No.: 50-281 License No.: DPR-37

Dear Sirs:

Pursuant to 10CFR50.73, Virginia Electric and Power Company hereby submits the following Licensee Event Report applicable to Surry Power Station Unit 2.

Report No. 50-281/2005-001 -00 This report has been reviewed by the Station Nuclear Safety and Operating Committee and will be forwarded to the Management Safety Review Committee for its review.

Very truly yours, donald E. Jernigan, Site Vice President Surry Power Station Enclosure Commitments contained in this letter:

By no later than the preventive maintenance or refurbishment during the next refueling outage, all remaining safety related circuit breakers with upgrade kits installed will be inspected, and the close latch release rod air gap will be adjusted.

Serial No.:

05-348 Docket No.: 50-281 cc: United States Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 Mr. N. P. Garrett NRC Senior Resident Inspector Surry Power Station

NRC FORM 366 US. NUCLEAR REGULATORY COMMISSION APPROVED BY B: NO. 3150-0104 EXPIRES 0632007 (6-20064)

, the NRC may not conduct or sponsor, and a person is not required to respond to, the digitstcharacters for each block) information collection.

3. PAGE Surry Power Station, Unit 2 05000.

281 1 OF 5

4. TITLE Low Head Safety Injection Pump Breaker Failed to Close Due to Binding

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED SEQUENTIAL REV M

HY FACILnTY NAME DOCKETNUMBER MONTH DAY YEAR YEAR NUMBER NO.

MONTH DAY YEAR 05000 FACLIIT NAME DOCKET NUMBER 04 01 2005 2005 -

001 -

00 06 24 2005 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Checkall thatappty)

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20.2201(b)

E 20.2203(a)(3)(i) 1 50.73(a)(2)(i)(C) 2 50.73(a)(2)(vii)

N E

20.2201(d) j 20.2203(a)(3)(ii) a 50.73(a)(2)(ii)(A)

E 50.73(a)(2)(viii)(A) 20.2203(a)(1)

E 20.2203(a)(4) a 50.73(a)(2)(ii)(B) i 50.73(a)(2)(viii)(B) a20.2203(a)(2)(i) 50.36(C) (1 ) (i)(A) 50.73(a)(2)(iii) 50.73(a)(2) (ix) (A)

10. POWER LEVEL 1

20.2203(a)(2)(ii)

Cl 50.36(c)(1)(ii)(A) a 50.73(a)(2)(iv)(A) 2 50.73(a)(2)(x)

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Cl 73.71(a)(4) 0%

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Specify in Abstract below

_____or In N PC Form W6A

12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (include Area Code)

Donald E. Jernigan, Site Vice President (757) 365-2001MANU-IREPORTABLE MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT FACTURER TO EPIX

CAUSE

SYSTEM COMPONENT FACTURER TO EPIX B

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14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YEAR I SUBMISSION Cl YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

El NO DATE ABSTRACT (Umit to 1400 spaces, I.e., approximately 15 single-spaced typewritten lines)

On April 26, 2005 at 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br />, while performing an engineered safety feature actuation test with Unit 2 in cold shutdown, breaker 24J-3 for low head safety injection (LHSI) pump 1 B failed to close while in the test position when a simulated automatic closure signal was generated. At the time of the failure, Unit 1 was at 100% reactor power.

An interim root cause evaluation determined that the most probable cause of the circuit breaker 24J-3 failure was binding of the close latch roller in conjunction with a burr or plating on the edge radius of the primary close latch. A spare safety related breaker was installed, tested, and the LHSI pump returned to service. Other safety related Unit 2 breakers were tested for a similar restriction. No problems were found, which provided confidence that breakers on Unit 1 were satisfactory. All remaining susceptible safety related Unit 1 and Unit 2 breakers will be inspected for similar issues.

A risk assessment determined that the potential unavailability of the LHSI pump 1 B on cumulative core damage probability was a low risk significant event. An evaluation considered the breaker to have been inoperable since the previous successful test on April 1, 2005. During this time period, the redundant LHSI pump 1A was briefly inoperable related to tests and maintenance on its associated emergency diesel generator.

(ff more space Is required, use add tional copes of NRC Form 366A) 1.0 DESCRIPTION OF THE EVENT On April 26, 2005 at 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br />, while performing an engineered safety feature actuation test with Unit 2 in cold shutdown, breaker 24J-3 [EIIS-ED, BKR] for Low Head Safety Injection (LHSI) pump 1 B [EIIS-BP, P] failed to close when a simulated automatic closure signal was generated with the breaker in the test position.

Following the failure to close during the actuation test, the breaker also failed to close when the Main Control Room (MCR) switch was placed in the closed position and when the local close pushbutton on the breaker was depressed. The breaker was inspected while still in the test position and it was noted that the coil spring was charged and there was no overcurrent trip bell lockout at the breaker. A manual close lever was used to successfully close the breaker. The breaker was opened from the MCR and the closing spring charged as designed. A second attempt to close the breaker from the MCR failed.

Technical Specification 3.3 requires that two safety injection subsystems be operable, with each subsystem including one operable low head safety injection pump, when a reactor is made critical. During power operation, the requirements may be modified to allow one LHSI subsystem to be inoperable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. An evaluation considered the breaker to have been inoperable since the previous successful test on April 1, 2005, exceeding the allowed outage time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Therefore, this report is submitted in accordance with 10CFR50.73(a)(2)(i)(B) for any operation or condition that was prohibited by Technical Specifications. In addition, Technical Specification 1.0 definition for operable requires all necessary emergency electrical power sources that are required for a device to perform its specified function(s) are also capable of performing their related support function(s).

However, the emergency diesel generator for the redundant LHSI pump 1A was inoperable related to testing and maintenance from April 23, 2005 at 0856 hours0.00991 days <br />0.238 hours <br />0.00142 weeks <br />3.25708e-4 months <br /> for less than 19 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br />. Therefore, this report is submitted in accordance with 10CFR50.73(a)(2)(v)(D) for any 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.

2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS

Surry Unit 2 has two subsystems of safety injection that are used to remove heat from the reactor core. Each subsystem includes one high head charging pump [EIIS-BQ, P], and one low head safety injection pump. There are two independent and redundant LHSI pumps with their discharges cross connected so that either pump is capable of providing safety injection to the reactor coolant system. The as-found condition of circuit breaker 24J-3 resulted in the inability of the breaker to(1-2001)

U. S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

I perform its safety function by electrically closing to start LHSI pump 1 B. However, circuit breaker 24J-3 was able to be manually closed locally as demonstrated during troubleshooting.

A probabilistic risk analysis was performed for the potential unavailability of the LHSI pump 1 B for this event. The analysis concluded that the cumulative core damage probability was of low risk significance.

3.0 CAUSE

During initial breaker inspections, the closing spring was found to be charged, which was unexpected, and the primary and secondary close latches (reference Figure 1) were found to have moved to a position that should have allowed the spring to discharge. By design, upon receipt of an actuation signal, the breaker close latch release rod will move the secondary close latch which in turn will move the primary close latch off the primary close latch roller. Inspection in the shop, however, found the primary close latch movement on the close roller was restricted. When the breaker was disassembled, the close roller was also confirmed to have a restriction to turning on the roller shaft.

Primary Close Latch Cam Secondary Close Latch Air Gap Close Latch Release Rod Graphks No CB4De FIGURE 1 Circuit breaker 24J-3 was refurbished in 2003 and retrofitted with an upgrade kit.

New upgrade kits in stock at the station and the vendor facility were inspected. The restriction to turning was observed on some of the primary close latch rollers at both facilities.U. S. NUCLEAR REGULATORY COMMISSION (1-2001)

LICENSEE EVENT REPORT (LER)

1. FACILITY AME2.

DOCKET

6. LER NUMBER

3. PAGE YEAR SEQUENTIAL REVISION 0

NUMBER NUMBER 4

Surr Power Station 02005 001 00 After troubleshooting was complete at the station, the breaker was reassembled with new parts. The reassembled breaker was shipped to the vendor facility for further testing. It was concluded that:

• Binding of the close roller alone cannot cause the failure. Force testing and minimum voltage testing proved that a binding roller does not cause the breaker to fail to close manually and/or electrically.

• The failure was most likely caused by two factors:

Burrs or material where the close roller is mounted obstructing proper operation.

Burrs or plating on the edge of the radius of the primary close latch, where it rolls off of the close roller, obstructing proper operation.

The interim root cause evaluation report concluded that the most probable cause of circuit breaker 24J-3 failing to close is the binding of the primary close latch roller, in conjunction with a burr or plating on the edge radius of the primary close latch.

Following the breaker closing using the manual close lever, the failure of the breaker to close electrically was attributed to failure of the coil due to overheating which resulted from the breaker binding.

4.0 IMMEDIATE CORRECTIVE ACTION(S)

The failed 24J-3 breaker was removed from the cubicle and taken to the breaker shop for further investigation. A spare safety related breaker was installed for the failed breaker, the breaker was successfully tested, and the LHSI pump returned to service.

5.0 ADDITIONAL CORRECTIVE ACTIONS

Additional testing was performed to check for close mechanism restriction. A manual close lever force test was conducted in accordance with the vendor instructions to measure the force required to close the breaker. Eight Unit 2 safety related breakers, which have had upgrade kits installed and which electrically close to perform their safety function, were tested and all were well below the measurement that would indicate a restriction. The results of this testing provided confidence those breakers on Unit 1 were satisfactory. A Root Cause Evaluation was initiated and an interim root cause report was issued.U. S. NUCLEAR REGULATORY COMMISSION (1-2001)

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEA SEQUENTAL REVSION PtNUMBER NUMBER Surry Power Station 000- 281 2005 001 00 5

OF 5

6.0 ACTIONS TO PREVENT RECURRENCE During the next preventive maintenance or refurbishment activity, but no later than the next refueling outage on the respective unit, all remaining Unit 1 and Unit 2 safety related breakers with upgrade kits installed will be inspected to verify that the edge radius of the primary close latch is free from burrs and verify that the primary close latch roller will rotate freely. In addition, the close latch release rod air gap will be adjusted to provide more margin to overcome frictional forces and ensure that the secondary close latch mechanism mechanically moves the primary close latch off of the close roller.

The schedule for the remaining breakers is considered appropriate due to both the infrequent occurrence of malfunction of similar breakers (failure history), and due to the infrequent failure potential indicated by the repetitive, successful testing of similar refurbished breakers following preventive maintenance and upgrade kit installation activities.

7.0 SIMILAR EVENTS

Review of previous ABB 480 K-Line breaker failures was performed and no failures attributed to the same mechanism were found.

LER 50-281/2003-002-00, Inside Recirculation Spray Pump Breaker Failed to Close Due to Mechanical Binding, also indicated a similar cause, however, the failure was due to gaps between the primary close latch roller and charging cam. The breaker upgrade kit installations reduced these gaps.

8.0 MANUFACTURER/MODEL NUMBER Asea Brown Boveri K600 EO DO

9.0 ADDITIONAL INFORMATION

Unit 1 was at 100% reactor power before and during this event and remained unaffected.