05000281/LER-2003-002

LER-2003-002,

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2812003002R00 - NRC Website

FACILITY NAME (1)

SURRY POWER STATION

DOCKET � LER NUMBER 16) � PAGE (3) [ sEouurniu. � REVI$ON � 1.0 DESCRIPTION OF THE EVENT On September 23, 2003, while performing a periodic test with Unit 2 in cold shutdown, breaker 24J-4 (EUS-ED, BKRI for Inside Recirculation Spray (ISRS) pump 18 failed to close when a simulated automatic closure signal was generated. The breaker was in the test position and open to support surveillance testing. When the breaker was removed from its cubicle, the breaker closing springs did not discharge as expected. A manual attempt to locally close the breaker was made but the breaker remained open. A manual charging handle was then inserted and a slight agitation of the manual charge lever closed the breaker.

A review indicated that this breaker was last operated successfully during an April 3, 2002 test. Technical Specification 3.4 requires that four recirculation spray subsystems, including recirculation spray pumps, shall be operable when a unit's reactor coolant system temperature or pressure exceeds 350 degrees Fahrenheit (F) or 450 psig, respectively. During power operation, the requirements may be modified to allow one ISRS 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 />. Due to the breaker failure, the ISRS pump 1 B was assumed to be inoperable, for longer than allowed, therefore, this report is submitted in accordance with 10CFR50.73(a)(2)(i)(B) for any operation or condition which was prohibited by Technical Specifications.

2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS Surry Unit 2 has four subsystems of Recirculation Spray (RS) that are used for containment depressurization and sump cooling. Each subsystem has one spray header supplied by a RS pump and cooled by a RS heat exchanger. A probabilistic risk analysis concluded that any one of the four RS subsystems is sufficient to ensure containment pressure and temperature limits can be maintained. The integrated risk for this event was determined to be of low significance.

3.0 CAUSE Following surveillance testing, the breaker was taken to the breaker shop and cycled 30 times successfully, including 5 cycles at reduced control system voltage. The breaker was then disassembled. Areas of wear were noted on the oil cite bearing, primary close latch, and primary latch roller bearing. The breaker was re-assembled using the original parts and was cycled approximately 300 times successfully. The breaker was then disassembled and bluing was placed on the primary close latch roller bearing to trace the primary latch lever and roller bearing movement. When the breaker was again re- assembled and tested, the bluing showed movement toward the charging cam. Based on the findings noted during disassembly and comparisons with retrofit kit replacement parts,

DOCKET

� LER NUMBER 16) PAGE (3) I Nu .m � HUUBEfi FAC1UTY NAME (1)

SURRY POWER STATION

the following is considered to be the failure mechanism. When the circuit breaker charged, the primary close latch that should rest on the face of the roller bearing slid between the roller bearing and the charging cam. The primary close latch wedged between the roller and charging cam. When the breaker was electrically signaled to close, the closing spring tension further wedged the cam roller, and the breaker closing motion ceased. When the manual charging device was used, it pulled the charging cam through the wedged condition allowing the breaker to close.

The root cause evaluation determined that the failure of the ISRS pump 1B model 0 ABB K-Line 600 series breaker was mechanical binding due to interference between the moving parts of the breaker 24J-4 operating mechanism. The original model 0 operating mechanism has inherent gaps between the various moving component parts. These gaps allowed misalignment of the various moving parts, creating the potential for binding or interference in the moving parts.

4.0 IMMEDIATE CORRECTIVE ACTIONS) After the breaker failed to close in the test position, the breaker was removed from its cubicle. A manual charging handle was then inserted and a slight agitation of the manual charge lever closed the breaker. The breaker was then reinstalled into the cubicle and cycled two times with satisfactory results. The breaker was returned to the test position to allow surveillance testing to be completed and no further problems were noted with the breaker.

5.0 ADDITIONAL CORRECTIVE ACTIONS A spare breaker was refurbished with a retrofit upgrade repair kit and installed in 24J-4.

A retrofit upgrade repair kit for the model 0 K-Line 600 series breaker improves the design by reducing the inherent gaps in the operating mechanism.

6,0 ACTIONS TO PREVENT RECURRENCE Review of equipment history indicates Units 1 and 2 have other safety-related breakers similar to breaker 24J-4. Two Unit 1 and four Unit 2 safety related breakers that receive automatic safety system closure signals were refurbished with the retrofit upgrade repair kit. Five breakers on Unit 1 and two breakers on Unit 2 will be refurbished with the retrofit upgrade repair kit during or prior to the next scheduled outage of sufficient duration. The schedule for the remaining breakers is considered appropriate due both to the infrequent occurrence of malfunction of similar breakers (failure history), and due to the infrequent failure probability indicated by the repetitive, successful testing of the 24J-4 breaker following detection of the malfunction.

NRC FORK! 386A (7-2001) U.S. NUCLEAR REGULATORY COMMISSION FACILITY NAME (1)

DOCKET

05000 - 281 LER NUMBER (6) PAGE (3) IL � NUMBER 7.0 SIMILAR EVENTS None 8.0 MANUFACTURER/MODEL NUMBER ABB K-Line 600 series circuit breaker model 0 9.0 ADDITIONAL INFORMATION None