ENS 52377
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ENS Event | |
|---|---|
23:00 Nov 17, 2016 | |
| Title | Incorrect Method Used for Calculation of Control Room Habitability |
| Event Description | During the NRC CDBI [Component Design Basis Inspection], it was identified that the calculation used to demonstrate Control Room Habitability following a Design Basis Accident (DBA) utilized an inappropriate methodology. Specifically, the calculation used dual air inlets for the emergency zones as the type of system used for Main Control [Room] Ventilation (VC) system. In order to use the dual inlet type system in the analysis, each of the VC subsystems is required to be single failure proof. The VC system is single failure proof, but the individual subsystems at the inlet, as designed, are not.
The dual inlet type system allows for certain calculated dose concentrations to be reduced by a factor of 4. Elimination of this reduction factor results in higher calculated control room dose following a DBA which exceeds the 5 Rem limit. This event is reportable under 10 CFR 50.72(b)(3)(ii)(B), 'Any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety.' A standing order has been issued for compensatory actions in the event of an emergency. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Clinton  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+14.67 h0.611 days <br />0.0873 weeks <br />0.0201 months <br />) | |
| Opened: | Jacob Sereno 13:40 Nov 18, 2016 |
| NRC Officer: | Bethany Cecere |
| Last Updated: | Nov 18, 2016 |
| 52377 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (99 %) |
| After | Power Operation (99 %) |
WEEKMONTHYEARENS 531102017-12-09T19:48:0009 December 2017 19:48:00
[Table view]10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 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, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Manual Reactor Scram Due to Loss of Division 1 Ac Power to Numerous Components ENS 526012017-03-09T09:19:0009 March 2017 09:19:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Relay Failure ENS 523772016-11-17T23:00:00017 November 2016 23:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Incorrect Method Used for Calculation of Control Room Habitability ENS 516692016-01-20T19:11:00020 January 2016 19:11:00 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 Primary-Secondary Containment Pressure Differential Exceeded Due to Ccp Exhaust Fan Trip ENS 493732013-09-20T14:17:00020 September 2013 14:17:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Safe Shutdown Analysis Reveals Noncompliance for a Fire Outside Diesel Room ENS 475102011-12-08T11:00:0008 December 2011 11:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Non Fused Dc Bus Ammeters Could Short and Cause a Fire ENS 466032011-02-08T14:00:0008 February 2011 14:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Event Could Initiate High Pressure Core Spray and Overfill the Reactor Pressure Vessel ENS 451222009-06-10T14:20:00010 June 2009 14:20:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Unknown Cable with Combustible Coating Found in Division I / Division II Cable Tray 2017-03-09T09:19:00 | |
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