ENS 47545
ENS Event | |
|---|---|
18:59 Dec 21, 2011 | |
| Title | Groundwater Level May Exceed Design Assumptions |
| Event Description | On December 21, 2011, at 1359 hours0.0157 days <br />0.378 hours <br />0.00225 weeks <br />5.170995e-4 months <br /> EST, it was determined that the test instruction for the weekly groundwater level readings contained non-conservative acceptance criteria. The test instruction acceptance criteria for groundwater level exceeds the initial assumptions used in the Updated Safety Analysis Report (USAR) Chapter 15 accident analysis for 'Postulated Radioactive Releases due to Liquid Containing Tank Failures.' The issue was identified during the conduct of a prompt functionality assessment evaluating the plant underdrain system performance and to ensure all USAR described functions were being met.
The test instruction acceptance criteria is less than 575 feet. The calculation supporting the Chapter 15 accident analysis assumes an initial groundwater elevation of 568 feet in order to accumulate a sufficient volume of groundwater to dilute the tank inventory prior to exiting the underdrain system. The accumulation volume results in hold up time allowing for mixing and radioactive decay. With the degraded performance of the underdrain system pumps and high precipitation, the groundwater level had risen above 568 feet but was still less than 575 feet. A preliminary engineering evaluation has determined that significant margin exists in the calculation. A calculation revision is being pursued in parallel with this notification. Compensatory actions involving the repair of 1 permanent non-safety pump and installation of temporary pumps were previously initiated and the groundwater levels are decreasing. Restoration of the remaining permanent plant pumps continues. The NRC Resident Inspector has been notified.
The calculation supporting the USAR Chapter 15 accident analysis was reviewed and subsequently revised. The revised calculation verifies and initial groundwater elevation of 575 feet is consistent with the preliminary assessment that substantial margin existed in the calculation for the underdrain system. Because the condition reported in Event Number 47545 was not an event or condition that results in the nuclear power plant being in an unanalyzed condition that degrades safety, the condition is not reportable, and this notification is retracted. The evaluation for this condition is documented in condition report 2011-07169. The NRC Resident Inspector and R3DO (Passehl) were notified. |
| Where | |
|---|---|
Perry  Ohio (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+2.63 h0.11 days <br />0.0157 weeks <br />0.0036 months <br />) | |
| Opened: | James Pry 21:37 Dec 21, 2011 |
| NRC Officer: | John Knoke |
| Last Updated: | Feb 15, 2012 |
| 47545 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 564552023-04-06T20:46:0006 April 2023 20:46:00
[Table view]10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Main Steam Line 'B' Leakage in Excess of Tech Spec Limits ENS 536752018-10-19T04:00:00019 October 2018 04:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Hot-Short Fire Event That Could Adversely Impact Safe Shutdown Equipment ENS 536442018-10-04T04:00:0004 October 2018 04:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Hot Short Fire Event That Could Adversely Impact Safe Shutdown Equipment ENS 502132014-06-19T20:28:00019 June 2014 20:28:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to a Postulated Hot Short That Could Affect Safe Shutdown Equipment ENS 494462013-10-17T17:00:00017 October 2013 17:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Hot Short Fire Event That Could Adversely Impact Safe Shutdown Equipment ENS 475452011-12-21T18:59:00021 December 2011 18:59:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Groundwater Level May Exceed Design Assumptions ENS 475082011-11-17T01:00:00017 November 2011 01:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Flooding Scenario Results in Unanalyzed Condition ENS 470242011-07-05T22:15:0005 July 2011 22:15:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Two Appendix R Wiring Issues That Could Potentially Affect the Ability to Shutdown ENS 436032007-08-27T20:45:00027 August 2007 20:45:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Grating Inside Containment Found Unsecured ENS 420722005-10-21T13:00:00021 October 2005 13:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Relocation of a Fire Door Boundary ENS 414172005-02-17T22:30:00017 February 2005 22:30:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Emergency Diesel Generators Declared Inoperable Due to Unanalyzed Condition ENS 413442005-01-19T07:37:00019 January 2005 07:37:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Emergency Diesel Generators Declared Inoperable Due to an Unanalyzed Condition ENS 404042003-12-22T01:21:00022 December 2003 01:21:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Impact to Safe Shutdown Due to Control Complex Ventilation Inoperability 2023-04-06T20:46:00 | |