ENS 50641
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ENS Event | |
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18:11 Nov 25, 2014 | |
Title | Deficiency in Methodology Used for Emergency Core Cooling System Performance Requirements |
Event Description | On Tuesday November 25, 2014, at 1211 CST, Arkansas Nuclear One, Unit 1 (ANO-1) reviewed AREVA 10 CFR 50.46 Notification Letter FAB14-00632. This letter indicates that a deficiency was discovered in the uranium thermal conductivity models used in the ANO-1 Loss of Coolant Accident (LOCA) analysis of record. When the deficiency is corrected, the LOCA Peak Cladding Temperature (PCT) limits may be in excess of 2200 degrees Fahrenheit (F). 10 CFR 50.46 paragraph (b) defines the acceptance criteria for the LOCA analysis process. The ANO-1 licensing basis PCT is evaluated for compliance with the criterion 10 CFR 50.46(b)(1) and must not exceed a PCT of 2200 degrees F.
During AREVA's review of the issue, AREVA had provided compensatory measures in the form of reductions in LOCA linear heat rates as a contingency in case the errors were found to be substantiated, which were then translated into reduced axial imbalance limits so that ANO-1 would operate within 10 CFR 50.46 limits. As a precautionary measure pending the completed analysis, ANO-1 implemented the compensatory measures on October 20, 2014, and as a result, the errors reported have no impact on current plant operation or public health and safety. This event is being conservatively reported in accordance with 10 CFR 50.72(b)(3)(ii)(B). Based on 50.46(a)(3)(ii) criteria, ANO-1 will submit a written report within 30 days. ANO-1 has notified the NRC Senior Resident Inspector. |
Where | |
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Arkansas Nuclear Arkansas (NRC Region 4) | |
Reporting | |
10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
LER: | 05000313/LER-2014-002 |
Time - Person (Reporting Time:+-1.07 h-0.0446 days <br />-0.00637 weeks <br />-0.00147 months <br />) | |
Opened: | Keith Ledbetter 17:07 Nov 25, 2014 |
NRC Officer: | Daniel Mills |
Last Updated: | Nov 25, 2014 |
50641 - NRC Website
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Unit 1 | |
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Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
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