05000335/LER-2012-004
| Event date: | 08-01-2012 |
|---|---|
| Report date: | 08-20-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) |
| 3352012004R00 - NRC Website | |
Description of the Event
On August 1, 2012, with Unit 1 operating at 100 percent power and Unit 2 reducing power from approximately 70 percent power to approximately 68 percent power as part of a coastdown for the upcoming refueling outage, it was determined that opening the boundary valve between the safety related and seismically qualified Refueling Water Tank (RWT) and the non-safety related and non-seismically qualified Spent Fuel Purification (SFP) system in Modes 1-4 renders the RWT inoperable.
The isolation between the seismic and non-seismic piping is accomplished via a normally locked closed, manually operated, seismically qualified isolation valve (V07104). The piping on the discharge of the fuel pool purification pump is not seismically qualified and could fail during a seismic event. As a result, with V07104 open and aligned for fuel pool purification, this alignment could result in a loss of inventory from the RWT during a seismic event rendering the RWT inoperable. Consistent with NRC Information Notice 2012-01, it has been determined that opening the boundary valve for planned maintenance activities while the plant was operating in Modes 1 through 4 would render the RWT inoperable regardless of the administrative controls that were in place. Since the boundary valve had been opened under administrative controls in Modes 1 through 4 and the one hour completion time of the Action Statement for Technical Specification 3.5.4 was not satisfied, this represents a condition prohibited by Technical Specifications and is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B).
Cause
The direct cause of this event was an incorrect application of compensatory measures (i.e., manual operator actions) when placing the non-seismic SFP system in service on seismically qualified systems/components (RWT) for planned maintenance activities during Modes 1 through 4. Prior to the issuance of NRC Information Notice 2012-01, manual operator actions had been evaluated and deemed acceptable in accordance with processes and procedures in place at that time. However, recently it has been determined that licensees cannot use compensatory measures to mitigate RWT operability for planned maintenance activities should a seismic event occur.
Analysis of Safety Significance Since no seismic events occurred while the SFP system was aligned to the RWT, this event had no significant safety consequence and there is no increase in risk above the baseline. In addition, procedural controls were in place to maintain the RWT level such that sufficient time (30 minutes) was available for plant personnel to isolate the RWT from the non-seismic piping by closing V07104 prior to the level falling below that required to satisfy the Technical Specification 3.5.4.a minimum volume Limiting Condition for Operation.
Also, although not specifically credited following a seismic event, the safety injection tanks have been credited as a backup water source for RCS makeup during safe shutdown.
This licensee event report is being reported in accordance with 10 CFR 50.73(a)(2)(i)(S) as a condition prohibited by Technical Specifications.
Immediate Corrective Actions
An Operations Department Policy was issued which outlines the conditions for RWT operability when aligned to the SFP system.
Additional Corrective Actions The various options for properly aligning the RWT to the SFP system are being evaluated as part of the apparent cause evaluation being performed under the corrective action program.
Similar Events This condition was previously documented in the corrective action program. Prior corrective actions implemented administrative controls including manual operator actions. However, consistent with Information Notice 2012-01, it has been determined that compensatory measures such as operator actions cannot be used to mitigate RWT operability should a seismic event occur.
Failed Component(s) N/A Manufacture N/A