05000424/LER-2014-001
| Vogtle Electric Generating Plant (Vegp) - Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4242014001R00 - NRC Website | |
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A. 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 RPV when RCS pressure was lowered below zero (0) psig.
B. 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. 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.
C. DESCRIPTION OF EVENT
On February 20, 2014 with VEGP Units 1 and 2 operating at 100 percent thermal power, VEGP identified that both units had operated outside the PTLR curve required by Technical Specification LCO 3.4.3 RCS Pressure and Temperature Limits following the seven previous refueling outages on each unit. From October 2003 through May 2013, seven refueling outages have been conducted on each unit in which the RPV was placed under vacuum to perform fill and vent operations. LCO 3.4.3 requires that RCS pressure, temperature, and heatup and cooldown rates be maintained with the limits specified in the PTLR and is applicable at all times. Although minimum 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.
The cause of not entering LCO 3.4.3 was the condition was procedurally allowed and aligned with Operations training. In August 2003, prior to the first use of RCS vacuum fill and vent at VEGP, an engineering analysis was performed to ensure the procedure would have no adverse impact on the system. Since the analysis determined there would be no adverse impact from drawing a vacuum on the RPV, Engineering and Operations did not recognize it was necessary to revise the PTLR curves and operation with the RPV under vacuum would be outside the limits of LCO 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.
D. CAUSE OF EVENT
The direct cause of the failure to enter the LCO was the condition was procedurally allowed and aligned with training Operations personnel had received. Therefore, establishing vacuum conditions in the RCS was not recognized to be a condition that required entry into the LCO.
E. SAFETY ASSESSMENT
The seven events on each unit posed no threat to public health and safety as the reactor pressure vessel performed as designed. 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 VEGP reactor pressure vessel. There was no impact to the safety of the public, industrial safety or radiological safety as a result of these events.
F. CORRECTIVE ACTION
Corrective Action to revise the VEGP Pressure and Temperature Limit Report (PTLR) for Units 1 and 2 to address establishing a negative pressure (vacuum) in the reactor vessel has been completed.
G. ADDITIONAL INFORMATION
1) Failed Components:
None 2) Previous Similar Events:
None 3) Energy Industry Identification System Code:
[AB] — Reactor Coolant System 4) Other Systems Affected:
None 5) Commitment Information:
This report does not create any commitments.