ENS 46697
ENS Event | |
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18:00 Mar 24, 2011 | |
Title | Non-Compliance with Nuhoms Technical Specification |
Event Description | This 24-hour report is being issued in accordance with the requirements of NRC Certificate of Compliance 1030, Amendment 0, for the NUHOMS Storage System, Technical Specification (TS) 2.2, Functional Operating Limit Violations.
During a review of historical North Anna NUHOMS dry storage canister (DSC) loading certification documents, a discrepancy was identified. The NUHOMS Certificate of Compliance 1030 Amendment 0 Technical Specifications include a Figure 2, "Heat Load Zones" which specifies the maximum decay heat load for each of the 32 assembly locations in a DSC. The figure includes limits for two zone '1b' locations and two zone '1a' locations in the four center locations of the DSC. The zone '1b' decay heat limit of 0.8 kw is specified for the two 'upper compartments' and zone '1a' decay heat limit of 1.05 kw is specified for the two 'lower compartments' on the figure. Contrary to this, the loading certifications for 7 of 10 DSCs already loaded at NAPS (North Anna Power Station) were not developed to maintain this orientation when loaded in the horizontal storage module (HSM). As a result, the DSC zone '1b' heat load limits were exceeded in some cases for these 7 DSCs. The heat load limit for all other zones in the DSCs are symmetric, and those assemblies were verified to the correct limit and are unaffected by this error. In addition the total heat load limit for the sum of the center assemblies was met for all DSCs. The maximum heat load of any zone '1b' assembly at the time of loading was 0.859 kw, which is slightly higher than the 0.8 kw limit. The lower heat load of assemblies in the other compartments offset the slightly higher heat load effects, and it is expected that the thermal analysis acceptance criteria would still have been met at the time of loading. The decay heat of the assemblies has continued to decrease since their initial loading and it was confirmed that 12 of the 13 assemblies that initially exceeded the 0.8 kw limit currently meet the zone '1b' heat load limits. The current decay heat of the remaining assembly is slightly above the 0.8 kw limit. Based on the offsetting margins identified above all of the affected DSCs are currently in a safe condition as loaded in the HSMs. The NRC Resident Inspector has been informed. |
Where | |
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North Anna ![]() Virginia (NRC Region 2) | |
Reporting | |
Other Unspec Reqmnt | |
Time - Person (Reporting Time:+17.23 h0.718 days <br />0.103 weeks <br />0.0236 months <br />) | |
Opened: | Don Taylor 11:14 Mar 25, 2011 |
NRC Officer: | Charles Teal |
Last Updated: | Mar 25, 2011 |
46697 - NRC Website
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Unit 1 | |
---|---|
Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
Unit 2 | |
---|---|
Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
WEEKMONTHYEARENS 474972011-12-05T13:47:0005 December 2011 13:47:00
[Table view]Other Unspec Reqmnt Discovery of After-The-Fact Emergency Condition - Unusual Event ENS 466972011-03-24T18:00:00024 March 2011 18:00:00 Other Unspec Reqmnt Non-Compliance with Nuhoms Technical Specification ENS 461532010-08-05T17:55:0005 August 2010 17:55:00 Other Unspec Reqmnt Discovery of After-The-Fact Emergency Condition Meeting Unusual Event Criteria ENS 454602009-10-23T20:34:00023 October 2009 20:34:00 Other Unspec Reqmnt, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Plant Shutdown Due to Excess Letdown Heat Exchanger Tube Leak and After-The-Fact Unusual Event ENS 450132009-04-22T09:00:00022 April 2009 09:00:00 Other Unspec Reqmnt Discovery of After-The-Fact Emergency Condition - Alert - Due to Fire Damage to Safety-Related Breaker ENS 403282003-11-17T16:50:00017 November 2003 16:50:00 Other Unspec Reqmnt Significant Leak in Fire Protection Header 2011-03-24T18:00:00 | |