05000368/FIN-2014005-05
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Finding | |
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| Title | Unit 2 Unplanned Scrams Performance Indicator |
| Description | The inspectors identified an unresolved item associated with the Unit 2 unplanned scrams per 7,000 critical hours performance indicator related to a reactor trip. On April 27, 2014, Unit 2 experienced an Axial Shape Index (ASI) trip when performing a rapid downpower at the request of the transmission grid operator due to severe weather affecting the grid. This unplanned reactor trip was caused by exceeding
the Core Protection Calculator ASI limits. As noted in Licensee Event Report 05000368/2014-003-00, and NRC Inspection Report 2014004, the ASI limits were exceeded, due in part to plant operators not following the downpower reactivity plan. The automatic trip occurred at approximately 50 percent power and was uncomplicated. The unplanned scrams per 7000 critical hours performance indicator measures the rate of scrams per year of operation at power and provides an indication of initiating event frequency. The licensee did not include this scram as an input into the unplanned scram performance indicator and submitted a frequently asked question to the NRC Reactor Oversight Process Working Group. The frequently asked question is currently under review to decide whether the above event should be captured as an unplanned scram. The licensee noted that anticipatory plant shutdowns to reduce the impact of externa events are excluded from this performance indicator. The licensee believed the intent of the exclusion was met because the shutdown being performed at the time the reactor trip occurred had been requested by the transmission grid operator due to the impacts of weather conditions. The inspectors noted that Nuclear Energy Institute Document 99-02, Regulatory Assessment Performance Indicator Guideline, Revision 7, guidance states that an unplanned scram is a scram that is not an intentional part of a planned evolution or test as directed by a normal operating or test procedure. This includes scrams that occurred during the execution of procedures or evolutions in which there was a high chance of a scram occurring but the scram was neither planned nor intended. The inspectors noted that the April 27, 2014 reactor trip was an automatic trip, which was not intended as part of the rapid downpower evolution that was being performed. The inspectors also noted that had the licensees reactivity plan been followed, the severity of the ASI transient would likely have been managed and a trip avoided. The inspectors concluded that additional inspection was required to assess whether the scram should have been reported in the unplanned scrams per 7,000 critical hours performance indicator for Unit 2. This issue was identified as Unresolved Item URI 05000368/2014005-05, Unit 2 Unplanned Scrams Performance Indicator. |
| Site: | Arkansas Nuclear  |
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| Report | IR 05000368/2014005 Section 4OA5 |
| Date counted | Dec 31, 2014 (2014Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71003 |
| Inspectors (proximate) | B Tindell G Guerra J Drake J Melfi J Rollins M Young P Elkmann R Lantz S Hedgerb Tindellj Melfi M Williams M Young N Greene P Hernandez R Lantz S Garchow W Sifre |
| INPO aspect | |
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Finding - Arkansas Nuclear - IR 05000368/2014005 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Arkansas Nuclear) @ 2014Q4
Self-Identified List (Arkansas Nuclear)
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