ENS 51772
ENS Event | |
|---|---|
10:00 Mar 7, 2016 | |
| Title | Unanalyzed Condition Involving Diesel Driven Auxiliary Feedwater Pump Air Intakes |
| Event Description | The Auxiliary Feedwater (AF) system at Byron 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 the sister 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 Byron 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 Byron 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 engineering is analyzing the issue. |
| Where | |
|---|---|
Byron  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| LER: | 05000454/LER-2016-001 |
| Time - Person (Reporting Time:+1.3 h0.0542 days <br />0.00774 weeks <br />0.00178 months <br />) | |
| Opened: | Allen Shephard 11:18 Mar 7, 2016 |
| NRC Officer: | Daniel Mills |
| Last Updated: | Mar 7, 2016 |
| 51772 - 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 519582016-05-25T18:00:00025 May 2016 18:00:00
[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 517722016-03-07T10:00:0007 March 2016 10:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Involving Diesel Driven Auxiliary Feedwater Pump Air Intakes ENS 513352015-08-20T22:55:00020 August 2015 22:55:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Condition That Could Prevent Pressurizer Porv Block Valves from Operating ENS 467082011-03-30T01:00:00030 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 464162010-11-12T19:00:00012 November 2010 19:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Inaccurate Information Provided in License Amendment Request 2016-05-25T18:00:00 | |