05000482/LER-2014-001
| Docket Number | |
| Event date: | 01-06-2014 |
|---|---|
| Report date: | 03-06-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4822014001R00 - NRC Website | |
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CONTINUATION SHEET
1 .FACILRYNAIVE 2.DOCKET 6. LER NUMBER 3. PAGE
PLANT CONDITIONS PRIOR TO THE EVENT
100% Mode 1 There were no structures, components or systems (SSC) that were inoperable at the start of the event and contributed to the event.
DESCRIPTION
During a review of outside operating experience on January 6, 2014, it was discovered that one utility received a non-cited violation of Technical Specification (TS), "Reactor Coolant System (RCS) Pressure and Temperature (P/T) Limits," for failure to comply with reactor pressure vessel pressure/temperature limits. The licensee had operated the plant with a vacuum in the reactor pressure vessel.
Wolf Creek Generating Station (WCGS) Technical Specification 3.4.3, "RCS Pressure and Temperature (P/T) Limits," Limiting Condition of Operation (LCO) 3.4.3 requires the RCS pressure, temperature and heatup and cooldown rates be maintained within the limits specified in the Pressure/Temperature Limits Report (PTLR). The Applicability for LCO 3.4.3 is "At all times." The RCS heatup and cooldown limitations in the PTLR only specify a pressure to 0 psig. WCGS draws a vacuum on the RCS [EllS: AB] at the end of refueling outages to fill the RCS, using procedure SYS BB-112, "Vacuum Fill of the RCS.
During the performance of SYS BB-112, a vacuum is drawn on the RCS to between 20 inches Hg and 24 inches Hg.
A review of operating history for the last three years found that WCGS drew a vacuum on the RCS on May 8, 2011 and March 30, 2013.
REPORTABILITY
NUREG-1022, Event Reporting Guidelines, Section 3.2.2, "Operation or Condition Prohibited by Technical Specifications," specifies that a Licensee Event Report is required if a condition existed for a time longer than permitted by the TS even if the condition was not discovered until after the allowable time had elapsed and the condition was rectified immediately upon discovery. Events that occurred within 3 years of the date of discovery are reportable.
During the past 3 years, a vacuum was drawn on the RCS on May 8, 2011 and March 30, 2013, using procedure SYS BB-112. TS 3.4.3, "RCS Pressure and Temperature (P/T) Limits," LCO 3.4.3 requires the RCS pressure, temperature and heatup and cooldown rates be maintained within the limits specified in the PTLR. The Applicability for LCO 3.4.3 is "At all times." The RCS heatup and cooldown limitations in the PTLR only specify a pressure to 0 psig.
Since the Applicability of TS 3.4.3 is "At all times," and the PTLR does not provide curves associated with a vacuum in the RCS, the plant was not operating in accordance with the TSs. Required Action C.1 requires initiating action to restore parameter(s) to within limits with a Completion Time of Immediately.
Action was not taken during the performance of SYS BB-112 to restore parameter(s) immediately. TS 1.3, "Completion Times," defines Immediately as pursued without delay and in a controlled manner.
The events that occurred on May 8, 2011 and March 30, 2013 are reportable as an operation or condition prohibited by Technical Specifications pursuant to 10 CFR 50.73(a)(2)(i)(B).
CAUSE
The apparent cause is inadequate engineering evaluation and procedure reviews resulted in allowing operations below PTLR Curve Limits. WCGS implemented a change in the method to which the Reactor Coolant System is filled and vented following a refueling outage without verifying the change complied with Technical Specification 3.4.3. Implementation of vacuum fill and vent of the RCS at WCGS was evaluated in Engineering Evaluation EER 92-BB-02 and implemented by use of SYS BB-112 without reference to the fact that the PTLR curves do not have values less than 0 psig.
CORRECTIVE ACTIONS
Procedure SYS BB-112 was cancelled so a vacuum will not be drawn on the RCS.
SAFETY SIGNIFICANCE
In the development of SYS BB-112, Engineering Evaluation EER 92-BB-02 evaluated the effect of drawing a vacuum on the RCS. Precautions necessary to prevent any system or equipment degradation were incorporated into the procedure. As a result, the reduction in RCS pressure would not affect the integrity of the RCS components.
OPERATING EXPERIENCE/PREVIOUS EVENTS
None