05000244/LER-2011-002

LER-2011-002, 1 OF 4

R.E. Ginna Nuclear Power Plant
Event date:	08-23-2011
Report date:	10-17-2011
2442011002R00 - NRC Website

A. PRE-EVENT PLANT CONDITIONS:

The reactor was in Operational Mode 1 at 100%, 2235 psig, and 574 degrees F.

B. EVENT:

On June 11, 2011, shortly after the 2011 Refueling outage, the lights in the Main Control Board to indicate that the "B" Main Steam Isolation Valve (MSIV) was open were flickering. Those lights subsequently went out. Since the issue was initially believed to be due to a potentially faulty limit switch, the repair of the limit switch was determined to be high risk, and the work was scheduled for a subsequent outage.

On August 23, 2011, when a fire water booster pump auto-started, the lights indicating that the "B" MSIV was open turned on. After the booster pump was secured, the lights turned off. Subsequent investigation showed that the fuse clip in the relay rack energized from battery "B" that is used to control the closure of "B" MSIV was not making contact with the glass fuse (FURAl/V7R-N). The cause was determined as apparently being that the vibration from the water booster pump relay may have caused the glass fuse to establish contact with the fuse clip and establish circuit continuity momentarily.

Troubleshooting on August 23, 2011, established that the fuse clip for glass fuse (FURA1/V7R-N) was damaged, therefore, it had resulted in a loss of circuit continuity and loss of indication in the Main Control Board, which in turn precluded control of the "B" MSIV with the circuit energized from battery "B.

The plant entered Technical Specification LCO 3.3.2, condition E, at 1220, to restore the logic circuit to operable status, and exited the LCO at 1403.

Maintenance was performed and the circuit was restored to service.

C. INOPERABLE STRUCTURES, COMPONENTS OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:

The fuse clip in the relay rack energized from battery "B" that is used to control the closure of the "B" MSIV was not making contact with the glass fuse (FURAVV7R-N).

D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES:

6/11/11 - Lights in the Main Control Board to indicate that the "B" MSIV was open were flickering. The lights subsequently went out.

8/23/11 - Fire water booster pump auto-started at 0430 and the lights indicating that the "B" MSIV was open turned on.

After the water booster pump was secured, the lights turned off. Subsequent investigation showed that the fuse clip in the relay rack energized from battery "B" that is used to control the closure of "B" MSIV was not making contact with the glass fuse (FURAl/V7R-N).

E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

None.

F. METHOD OF DISCOVERY:

Troubleshooting on August 23, 2011.

G. MAJOR OPERATOR ACTION:

The "B"MSIV was open at the time of discovery. No actions were required.

H. SAFETY SYSTEM RESPONSES:

Since the fuse clip in the relay rack energized from battery "B" that is used to control the closure of the "B" MSIV was not making contact with the glass fuse (FURA1N7R-N), the logic circuit energized from that battery was disabled. The redundant train of actuation logic for the "B" MSIV supplied from battery "A" was available.

H. CAUSE OF THE EVENT:

This event was entered into the site corrective action program as CR-2011-005962. A fuse clip in the relay rack energized from battery "B" that is used to control the closure of "B" MSIV was not making contact with the glass fuse (FURA1IV7R-N).

The apparent cause of this occurrence was the use of fuse blanks, which are used for hanging clearance tags, that were too large for the small fuse clips which resulted in a loose fit when the fuses were reinstalled.

III. ANALYSIS OF THE EVENT:

This event is reportable in accordance with 10CFR50.73, "Licensee Event Report System" under item (a)(2)(i)(B) based on the plant exceeding the LCO for Technical Specification 3.3.2, condition E, for a time period not discovered until the time allowed had elapsed.

An assessment was made of the impact of the failure of the fuse clip with the glass fuse on the safety function of steam line isolation following a Design Basis Accident (DBA). Isolation of the main steam lines provides protection in the event of a Steam Line Break inside or outside containment. Closure of the MSIVs and their associated non-return check valves limits the accident to the blowdown from only the affected Steam Generator. The actuation logic for each MSIV consists of two redundant trains of actuation logic, each supplied by a separate DC source. Though the actuation logic for the "B" MSIV from the "B" battery was inoperable due to the faulty fuse clip, the logic from the "A" battery was available.

The event was quantified conservatively through the Ginna PRA model assuming the failure of the one train of actuation circuitry and the event results in an increase in Incremental Conditional Core Damage Probability (ICCDP) of 2.20E-09 and a postulated worst case increase in Incremental Conditional Large Early Release Probability (ICLERP) of 2.20E-09.

III. ANALYSIS OF THE EVENT: (Cont.) Based on the above considerations, the nuclear safety consequences of this event are very low.

The event does not have any impact on NRC performance indicators.

IV. CORRECTIVE ACTIONS:

A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS Maintenance was performed and logic circuit was restored to service.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

An Issue Response Team (IRT) identified that the degradation of fuse clips was limited to those that were associated with small glass fuses. The primary contributor is the use of small fuse blanks for clearance tagging that have a larger diameter than the fuse clip, thereby causing damage to the fuse clip.

Forty nine locations with small glass fuses were visually inspected. Of those, nine locations were found to have a loose connection between the fuse clip and the glass fuse. Once visual inspections proved to be a reliable method of identifying the degree of contact between the fuse clip and the glass fuse, they were performed on all remaining glass fuses in the relay racks.

The site is developing and implementing training on installing fuse blanks.

A. FAILED COMPONENT

Fuse clip used with glass fuse (FURA1/V7R-N).

B. PREVIOUS LERS ON SIMILAR EVENTS

A review of recent Ginna events did not identify similar events.

C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND

SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:

COMPONENT IEEE 803 FUNCTION IEEE 805 SYSTEM

IDENTIFIER IDENTIFIER

FURAl/V7R-N