05000244/LER-2006-007

LER-2006-007, Main Steam Safety Valve Setpoint Exceedance

Docket Number
Event date:	10-07-2006
Report date:	3-1-2007
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2442006007R01 - NRC Website

I. PRE-EVENT PLANT CONDITIONS:

At the time the condition was identified, the plant was in Mode 1 at approximately 90% rated thermal power.

II. DESCRIPTION OF EVENT:

A. � EVENT:

On October 7, 2006, with the plant in Mode 1, in-place testing of main steam safety valve 3508 determined that the as-found lift pressure did not meet the acceptance band of +1% / - 3% of setpoint, as specified by Technical Specification surveillance SR 3.7.1.1. The initial as-found lift pressure for safety valve 3508 was 1.39% above the specified lift setting. This was the second unsatisfactory as- found lift pressure for a main steam safety valve, as in-place testing had previously determined that safety valve 3515 had failed to meet the as-found acceptance band, with an initial as-found lift pressure of 1.09% above the specified lift setting. All of the other valves were tested within range, but at an elevated lift setpoint when compared to their previous as-left value.

Technical Specification LCO 3.7.1 requires eight main steam safety valves to be operable in Modes 1, 2 and 3. Testing of main steam safety valves is performed one valve at a time, with each valve adjusted if necessary and returned to operable status before proceeding with the testing of another valve. In this manner, a maximum of one valve is known to be inoperable at any time during testing.

However, since the cause of the two unsatisfactory as-found lift pressures may have arisen over a period of time, it is assumed that at least one required main steam safety valve was not operable during past plant operation for a time greater than allowed. Therefore, this occurrence is considered reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's Technical Specifications.

THE EVENT:

None

C. DATES AND APPROXIMATE TIMES OF MAJOR OCCURENCES:

October 7, 2006, 1240 EDST: main steam safety valve 3515 removed from service for lift setpoint testing and returned to service following adjustment.

• October 7, 2006, 1445 EDST: main steam safety valve 3508 removed from service for lift setpoint testing and returned to service following adjustment.

D. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

None

E. METHOD OF DISCOVERY:

Review of test data associated with as-found setpoint testing.

F. SAFETY SYSTEM RESPONSES:

No safety systems were actuated.

III. CAUSE OF EVENT:

The apparent cause of the set point drift in the MSSVs is additional friction in the spindle guide area.

The additional friction can be caused by a reduced clearance between the spindle point and the guide bearing and/or a collection of dirt and other debris in this area. It has been determined by the manufacturer that there is a tendency for the bearing material to close up on the spindle point over time. Additional operating experience associated with MSSVs was recently issued by the NRC in Information Notice 2006-24, Recent Operating Experience Associated with Pressure and Main Steam Safety/Relief Valve Lift Setpoints.

IV. ASSESSMENT OF THE SAFETY CONSEQUENCES OF THE EVENT:

This event is reportable in accordance with 10 CFR 50.73, Licensee Event Report System, item (a)(2)(i)(B), which requires a report of, "Any operation or condition which was prohibited by the plant's Technical Specifications.

The operability of the main steam safety valves ensures that the secondary system pressure will be limited to within 110% of its design pressure of 1085 psig during the most severe anticipated system operational transient. The as-found condition of the main steam safety valves was compared to the current overpressure analysis prepared in support of extended power uprate and it was concluded that the analysis remained bounding. This analysis is conservative with regards to prior operation. As such, the applicable acceptance criteria for design basis events would have been met and the safety valves remained capable of performing their intended safety function.

Operation of the facility with the main steam safety valves as-found settings was within analytical bounds; therefore, this event had no impact on the health and safety of the public.

V.�CORRECTIVE ACTIONS:

A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

Immediate actions included adjusting main steam safety valves 3513 and 3508 to within +/-1% of their required set lift pressure.

The main steam safety valves were subsequently tested on October 31, 2006 during the plant startup from the refueling outage, and all of the valves exhibited a reduced as-found setpoint (within the +1% / - 3% allowed range).

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

A training session was held at the MSSV manufacturer's facility, which included verification testing of the identical Set Point Verification Device used at Ginna on October 7, 2006, as well as set point testing of an identical safety valve while simulating the Ginna conditions.

• The MSSVs will be evaluated for refurbishment during an upcoming refueling outage on a valve specific basis, based on vendor recommendations and analysis of test data.

VI.�ADDITIONAL INFORMATION:

A. FAILED COMPONENTS:

No other structures, systems, or components failed as result of this event.

B. PREVIOUS LERs ON SIMILAR EVENTS:

A similar Ginna LER event historical search was conducted which resulted in no similar events.

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

THIS LER:

COMPONENT IEEE 803 � IEEE 805 FUNCTION NUMBER�SYSTEM IDENTIFICATION Valve, Relief RV� SB