ENS 51771
ENS Event | |
|---|---|
02:00 Mar 7, 2016 | |
| Title | Unanalyzed Condition Involving Diesel Driven Auxiliary Feedwater Pump Air Intakes |
| Event Description | The Auxiliary Feedwater (AF) system at Braidwood automatically supplies feedwater to the Steam Generators (SG) to remove decay heat from the Reactor Coolant System following a loss of normal feedwater supply. The AF System consists of a motor driven pump (A) and a diesel driven pump (B) configured into two trains for each unit. Each pump provides 100% of the required AF capacity to the SGs as assumed in the accident analysis. One pump at full flow is sufficient to remove decay heat and cool the unit to Residual Heat Removal (RHR) entry conditions. The diesel driven AF pump is powered from an independent diesel whose combustion air intake is located in the Seismic Category II (non-seismically qualified) Turbine Building but the diesel and pump are located in the Seismic Category I (seismically qualified) Auxiliary Building.
During the ongoing NRC Component Design Basis Inspection at Braidwood Station, Inspectors asked about the acceptability of the diesel combustion air intake being located in the non-seismic Turbine Building. During the review of available documentation related to the AF diesel engine combustion air intake, it was identified that the documentation did not support operation of the diesel with High Energy Line Break (HELB) environmental conditions in the Turbine Building. This has been reviewed and determined to be applicable to Braidwood Station Units 1 and 2. Specifically, prior evaluations did not account for air displacement by steam release during the event. After running different models for the Turbine Building HELB, diesel driven AF pump operability was supported for all but the Main Feedwater (FW) HELB. For the FW HELB, the best air density obtained failed to remain above the required levels deemed acceptable for engine operation and remained suppressed for extended periods of time. Additional efforts to qualify the FW piping in the Turbine Building for an Operating Basis Earthquake (OBE) to eliminate this piping from HELB considerations were not successful. This condition applies to both Units 1 and 2 but does not affect the motor driven AF pumps. This event does not constitute a loss of safety function at the point of discovery because the Braidwood opposite train motor driven AF pumps were operable on both Units 1 and 2. This event is reportable per 10 CFR 50.72(b)(3)(ii)(B) for 'any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety.' The licensee has notified the NRC Resident Inspector. The licensee entered a 72-hour Action Statement and is preparing to address the issue with a configuration change. |
| Where | |
|---|---|
Braidwood  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| LER: | 05000456/LER-2016-001 |
| Time - Person (Reporting Time:+0 h0 days <br />0 weeks <br />0 months <br />) | |
| Opened: | James Petty 02:00 Mar 7, 2016 |
| NRC Officer: | Daniel Mills |
| Last Updated: | Mar 7, 2016 |
| 51771 - NRC Website | |
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 519592016-05-25T19:15:00025 May 2016 19:15:00
[Table view]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 Discovery of Non-Conforming Conditions During Tornado Hazards Analysis ENS 517712016-03-07T02:00:0007 March 2016 02:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Involving Diesel Driven Auxiliary Feedwater Pump Air Intakes ENS 513342015-08-20T22:10:00020 August 2015 22:10:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Condition That Could Prevent Pressurizer Porv Block Valves from Operating ENS 502822014-07-15T14:42:00015 July 2014 14:42:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Low Containment Spray Flow Rate ENS 502272014-06-25T20:55:00025 June 2014 20:55:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Loss of Ultimate Heat Sink Capacity Due to Low Level ENS 501892014-06-11T19:34:00011 June 2014 19:34:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition One Containment Spray Train Chemical Additive Flow Out of Specifications ENS 493712013-09-09T22:00:0009 September 2013 22:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Leakage of Containment System Isolation Valve Controlled Leakage Devices ENS 468682011-05-20T23:00:00020 May 2011 23:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Marine Life Inside Afw Piping ENS 467072011-03-30T01:00:00030 March 2011 01:00:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Voiding in Auxiliary Feedwater Alternate Suction Line ENS 464152010-11-12T19:00:00012 November 2010 19:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Inaccurate Information Provided in License Amendment Request ENS 462032010-08-24T16:40:00024 August 2010 16:40:00 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 Essential Service Water Placed in a Line-Up That May Have Prevented Its Safety Function ENS 460212010-06-17T10:19:00017 June 2010 10:19:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Containment Spray Recirc Sump Isolation Valve Failure to Stroke Closed 2016-05-25T19:15:00 | |