ENS 42020
ENS Event | |
|---|---|
15:00 Sep 27, 2005 | |
| Title | Postulated Faults Have Electrical Current in Excess of the Maximum Listed Interrupting Ratings. |
| Event Description | NMC (Nuclear Management Company) has identified certain equipment in the PBNP electrical distribution system that will not assure, under certain conditions, interruption of a three phase bolted fault short circuit. These postulated faults have electrical current in excess of the maximum listed interrupting ratings for designated circuit breakers and associated bus bar bracing. This condition affects the 13.8 Kv, 4.16 Kv, and 480 V power panels, motor control centers (MCCs), and switchgear. Although the probability of bolted faults is considered low, the Point Beach bolted fault analysis is based on the worst case assumption of three phases firmly tied together and grounded. A postulated bolted fault itself would only impact equipment in a single safety train. However, the PBNP Appendix R analysis relies on breaker coordination and fault current interruption to prevent loss of safe shutdown equipment due to common enclosure/power supply associated circuit concerns. The degraded breaker coordination resulting from a bolted fault condition does not satisfy the requirements of the Appendix R safe shutdown analysis.
This condition is reportable because the PBNP Appendix R analysis is based on the occurrence of a single fire in a single fire area. The postulated condition could result in a loss of safe shutdown equipment functionality beyond that previously analyzed. Compensatory measures (i.e., fire rounds - 6 times per day) have been implemented for cases where the unprotected cable length was routed beyond the original fire area. As part of the long-term corrective action, transformer tap setting changes to reduce bus voltages are being evaluated. The NRC Resident Inspector was notified of this event by the licensee.
This is a supplemental emergency notification based on additional information identified regarding degraded voltage conditions at PBNP. On 09/27/2005 NMC reported a condition where certain equipment in the PBNP electrical distribution system would not assure, under certain conditions, interruption of a three-phase bolted fault short circuit. Licensee Event Report (LER) 266 & 301/2005-005-00 was subsequently submitted on November 18, 2005. The original Event Notification Report was associated with bolted fault conditions that potentially resulted in additional unanalyzed fire losses due to direct fire damage or uncleared faults on associated circuits. The synopsis of the LER addressed these issues, and also identified: 1. A non-conservative Technical Specification for degraded voltage time delay relay settings and their setting tolerance range in calibration procedures that could have resulted in certain safety system motors and switchgear tripping on overcurrent. Such an event could have prevented the fulfillment of the motors' safety function to mitigate the consequences of an accident. 2. Under a design basis loss of coolant accident concurrent with a reduced voltage condition, safety-related motors and switchgear may trip their protective devices on overcurrent without the degraded voltage relays being actuated. Affected equipment included certain safeguards 480V AC switchgear, 480 V AC motor control centers, both auxiliary feedwater pump motors, and one component cooling water pump motor. Corrective actions for the above issues included placing calibration procedures on administrative hold, implementation of compensatory measures consisting of fire rounds for affected zones, and administrative controls to assure that a more restrictive limit for the degraded voltage allowable value was in place for the affected Technical Specification (s), as well as implementing administrative controls on the management of 480 V loads. Long-term corrective actions are evaluation and implementation of analytical changes resulting from the completed analysis, plant modification changes as needed to address minimum bus voltage and submittal of a license amendment request. Additional reviews into the extent of condition of this issue have revealed additional potential concerns associated if a station battery charger load test is conducted under reduced or degraded grid voltage conditions. If a battery charger load test is conducted during a degraded grid voltage condition and a loss-of-coolant accident occurs with a coincident safety injection signal but a loss of off-site power does not occur, the battery chargers are not stripped from their alternating current supply. The additional potential electrical load on the AC supply has not been analyzed. Compensatory measures, in the form of administrative controls associated with battery charger testing, are being implemented. A supplement to LER 266(301)/2005-005-00 will be submitted. The senior resident inspector has been informed of this supplemental report. Subsequent conversations between the Headquarters Operations Officer and the Shift Manager and Shift Technical Advisor at Point Beach have confirmed that this is not an "emergency" notification as quoted in the first paragraph of the event update. This is an event notification only. R3DO (Stone) notified.
On April 6, 2006, NMC provided a supplemental notification to EN# 42020 regarding a condition where certain equipment in the PBNP electrical distribution system would not assure, under certain conditions, interruption of a three-phase bolted fault short circuit. The supplemental notification resulted from additional reviews into the extent of condition of this issue, which indicated additional potential concerns associated with a station battery charger load test being conducted under reduced or degraded grid voltage conditions. A subsequent evaluation of this supplemental condition concluded that its significance is minor. The April 6, 2006, supplemental notification concerned 480 VAC vital bus loading due to battery charger load during charger testing and battery charger load while recovering a battery after battery discharge testing conducted under reduced or degraded grid voltage condition. The potential impact of this testing was evaluated to be associated only with the D-109 station battery charger and not several chargers as originally determined. An evaluation of the risk significance of this issue indicates that because of the combination of simultaneous events that would need to occur, the significance is minor. Because of the minor risk significance and that the issue concerns only a single piece of equipment (D-109 station battery charger), the guidance in NUREG-1022 indicates that this condition does not meet the reportability criteria in 10 CFR 50.72(b)(3)(ii)(B). Therefore, the supplemental notification made to EN #42020 on April 6, 2006, is hereby retracted. The underlying condition will continue to be addressed through the plant's corrective action process. The licensee notified the NRC Resident Inspector. Notified R3DO (M. Phillips). |
| Where | |
|---|---|
Point Beach  Wisconsin (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+2.25 h0.0938 days <br />0.0134 weeks <br />0.00308 months <br />) | |
| Opened: | Charles Stalzer 17:15 Sep 27, 2005 |
| NRC Officer: | John Mackinnon |
| Last Updated: | Jun 6, 2006 |
| 42020 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 532392018-03-01T22:43:0001 March 2018 22:43:00
[Table view]10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 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 Tornado Missile Vulnerabilities ENS 529762017-09-18T22:24:00018 September 2017 22:24:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 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 Control Room Envelope Not Maintained ENS 507402015-01-15T23:04:00015 January 2015 23:04:00 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 Inadequately Sealed Piping Penetrations and Postulated Flooding Event ENS 484022012-10-12T09:20:00012 October 2012 09:20:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Reactor Power Exceeded Fsar Analyzed Value ENS 443512008-07-16T20:16:00016 July 2008 20:16:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Fire Propagation Between Rooms Could Affect Appendix R Safe Shutdown ENS 434872007-07-12T15:15:00012 July 2007 15:15:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Fire Inspection Analysis of Pressurizer Porvs and Block Valves ENS 433532007-05-09T21:23:0009 May 2007 21:23:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Identified Non Compliant Fire Protection Manual Operator Actions ENS 421292005-11-08T14:44:0008 November 2005 14:44:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Design Basis for Long Term Cooling Not Correctly Modeled ENS 421092005-11-02T05:00:0002 November 2005 05:00:00 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, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Tech Spec Required Shutdown Due to Degradation of Containment Coatings ENS 420202005-09-27T15:00:00027 September 2005 15:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Faults Have Electrical Current in Excess of the Maximum Listed Interrupting Ratings. ENS 418562005-07-20T09:51:00020 July 2005 09:51:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Minimum Recirculation Valves Will Not Automatically Open in Local Operating Mode ENS 417582005-06-08T22:24:0008 June 2005 22:24:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - Fire Organizational Plan No Longer Aligned with Safe Shutdown Analysis ENS 417542005-06-07T23:00:0007 June 2005 23:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Appendix R Safe Shutdown Strategy Deficiency 2018-03-01T22:43:00 | |