05000348/LER-2014-001
| Joseph M. Farley Nuclear Plant, Unit 1 | |
| Event date: | 02-18-2014 |
|---|---|
| Report date: | 04-17-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3482014001R00 - NRC Website | |
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Westinghouse - Pressurized Water Reactor Energy Industry Identification Codes are identified in the text as [XX].
Requirement for Report This report is required per 10 CFR50.73(a)(2)(i)(B) for an operation or condition which was prohibited by Technical Specifications Limiting Condition of Operation (LCO) 3.4.3, RCS Pressure and Temperature Limits, during vacuum refill of the reactor coolant system (RCS) when RCS pressure was lowered below zero pounds per square inch gage (psig).
Unit Status at Time of Event At the time of discovery of the issue, both units were operating in Mode 1 at 100% reactor power.
Previous vacuum refill operations were conducted with the applicable unit in Mode 5. There were no additional inoperable structures, systems, or components at the time of discovery that contributed to this event. This event is considered a discovery of an existing but previously unrecognized condition.
Description of Event
On February 18, 2014 with Farley Nuclear Plant (FNP) Units 1 and 2 operating at 100 percent thermal power, a review of industry operating experience determined that both units were in non-compliance with Technical Specification 3.4.3, RCS Pressure and Temperature (P/T) Limits, during 23 previous refueling outages due to placing the RCS under vacuum conditions during RCS vacuum refill operations. From during which the RCS was placed under vacuum to perform vacuum refill operations. Technical Specification 3.4.3, applicable at all times, requires that RCS pressure, RCS temperature, and RCS heatup and cooldown rates be maintained within the limits specified in the Pressure Temperature Limit Report (PTLR). Although RCS temperature and heatup rates were maintained within limits, RCS pressure was lowered below 0 psig, the lowest RCS pressure value identified on the curve.
In October, 1995 the system operating procedure to perform RCS fill and vent under vacuum conditions was developed in accordance with an approved safety evaluation to facilitate RCS vacuum refill and eliminate the need to perform multiple reactor coolant pump sweeps of the RCS for removal of non- condensable gases. The safety evaluation for this procedure properly evaluated the impact of vacuum conditions on the reactor pressure vessel [RPV], the RCS, and related components. It was not recognized that this evolution would be in non-compliance with Technical Specification 3.4.3. Upon review of industry operating experience, the non-compliance was identified and corrective action initiated to update the PTLR curves to account for operation under vacuum conditions.
These events are of very low safety significance and resulted in no adverse effects on the health or safety of the public.
Cause of Event
The direct cause of not entering the required action for Technical Specification 3.4.3 was a failure to recognize that a negative RCS pressure is not allowed by Technical Specifications. Establishing vacuum conditions in the RCS was not recognized to be a condition that required entry into the required action statement.
Safety Assessment As determined in the safety evaluation for the vacuum refill implementing procedure, there were no challenges to any design or safety limit. Nuclear safety was not compromised because the negative (vacuum) internal pressures identified did not cause any concerns with applicable material stresses or analysis for the reactor pressure vessel or RCS piping. There was no impact to the safety of the public, industrial safety, or radiological safety as a result of the vacuum refill operations.
Corrective Action Corrective Action to revise the FNP Pressure and Temperature Limit Report (PTLR) for Units 1 and 2 to address establishing a negative pressure (vacuum) in the reactor vessel has been initiated and will be completed prior to the next vacuum refill operation. A review of Technical Specifications for similar or related issues with other Technical Specification curves has been initiated.
Additional Information
A review of internal Operating Experience was performed, and no previous events were identified in which a curve referenced by Technical Specifications was inaccurately applied leading to violation of a Technical Specifications.