05000346/FIN-2013008-02
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Finding | |
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| Title | Un-Fused Direct Current Ammeter Circuit |
| Description | Introduction: The following finding that affects 10 CFR 50.48 was identified by the NRC and was a violation of NRC requirements. This finding has been screened and determined to warrant enforcement discretion per the Interim Enforcement Policy Regarding Enforcement Discretion for Certain Fire Protection Issues. The inspectors identified a violation of 10 CFR 50.48(b) and 10 CFR Part 50, Appendix R, Section III.G.3 for the licensees failure to provide electrical protection for common enclosure associated circuits to ensure that one train of systems and components is free of fire damage during a fire. Specifically, the licensee failed to provide electrical protection (i.e., fuses) for the control room ammeter circuits associated with the batteries and battery chargers to a prevent secondary fire due to thermal and/or arcing affects from damaged ammeter cables outside the fire area. Description: The original plant wiring design for the station batteries and battery charger ammeter circuits contained a shunt in the current flow from each direct current station battery or charger. Two Institute of Electrical and Electronics Engineers (IEEE) standard 383 qualified leads were bolted to the shunt bar and connected to the ammeter in the control room. The small difference in voltage between the two taps on the shunt was enough to deflect the ammeter gauge in the control room when current flows from the battery or charger through the shunt. The ammeter wiring attached to the shunt did not have fuses. If one of the ammeter wires shorted to ground at the same time as another direct current (DC) wire from the opposite polarity on the same battery, a ground loop through the un-fused ammeter cable could occur. Thermal and/or arcing effects from the damaged ammeter cable could cause a secondary fire or damage adjacent cables located at some point along the path of the ammeter cable outside the fire area that may be required for safe shutdown thereby resulting in a loss of the associated safe shutdown function/capability. The licensee entered this issue into their corrective actions program as Condition Report (CR) 2013-02965 Un-fused DC Ammeter Circuits, dated February 28, 2013, and initiated hourly fire watches in fire areas where these cables were routed; Cable Spreading Room (Fire Area DD), Electrical Penetration Room (Fire Area DF), Low Voltage Switchgear Rooms (Fire Areas X and Y), and Heater Bay Room (Fire Area II). The licensee also completed an investigation summary report and concluded that these ammeters cables were not routed in the same trays with safe shutdown cables in these fire areas. However, the inspectors were still concerned that fire-induced damage of the ammeter cables, due to a fire in either the control room (Fire Area FF) or cable spreading room (Fire Area DD), could cause a secondary fire in the credited safe shutdown area (i.e., Fire Areas X or Y). A secondary fire in either the low voltage switchgear rooms could cause damage to cables or equipment required for safe shutdown thereby resulting in loss of the safe shutdown capability. The Fire Hazard Analysis Report (FHAR) credited Train 1 for the safe shutdown method in the event of a fire in either the control room or cable spreading room. Damaged ammeter cables could cause a secondary fire in a low voltage switchgear room (Fire Area Y) which contained Train 1 safe shutdown cables and components that were required for alternative shutdown capability. This condition was previously identified at other nuclear power stations as reported by Licensee Event Reports (LERs). The licensee at Davis-Besse Nuclear Power Station concluded that this condition was not reportable because it would not result in loss of any safe shutdown functions that were not already assumed lost by the safe shutdown analysis. Analysis: The inspectors determined that the failure to ensure that the alternative shutdown capability and its associated circuits remained free of fire damage during a fire was contrary to the requirements of 10 CFR Part 50, Appendix R, Section III.G.3 and was a performance deficiency. Specifically, the licensees failure to provide electrical protection for the station batteries and the battery charger ammeter circuits resulted in not ensuring safe shutdown systems and components would be free of fire damage in the event of a fire. Shorts to ground on the ammeter circuits could have resulted in a secondary fire or damage to safe shutdown cables located outside of the fire area in the event of a fire in the control room or cable spreading room. The finding was determined to be more than minor because the finding was associated with the Mitigating Systems cornerstone attribute of Protection Against External Factors (Fire) and affected the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences (i.e., core damage). Specifically, the failure to provide electrical protection to non-safe shutdown circuits associated with the battery charger ammeters could have resulted in a secondary fire which damaged safe shutdown cables and complicated safe shutdown of the plant in the event of a fire in the control room or cable spreading room. The licensee completed a quantitative risk assessment evaluation for this issue using the methodology contained in IMC 0609, Appendix F, Fire Protection Significance Determination Process, because the finding was fire protection-related and the licensee was in transition to NFPA 805. The licensees evaluation concluded that the finding was not associated with a finding of high safety significance based on a bounding analysis which showed that the increase in Core Damage Frequency due to the un-fused ammeter circuits issue was 4.96 10-5 per year. The inspectors reviewed the evaluation and concluded that it was appropriate. Cross-cutting aspects are not addressed for findings which warrant enforcement discretion per the Interim Enforcement Policy Regarding Enforcement Discretion for Certain Fire Protection Issues. Enforcement: Title 10 CFR 50.48(b)(2) requires, in part, that all nuclear power plants licensed to operate prior to January 1, 1979, must satisfy the applicable requirements of Appendix R to 10 CFR Part 50, including specifically the requirements of Sections III.G, III.J, and III.O. Appendix R,Section III.G.3 requires, in part, that alternative or dedicated shutdown capability and its associated circuits, independent of cables, systems, or components in the area, room, or zone under consideration should be provided where the protection of systems whose function is required for hot shutdown does not satisfy the requirement of Section III.G.2 of Appendix R. Fire Areas Fire Areas DD and FF were fire areas which required alternative or dedicated shutdown capability. Contrary to the above, as of February 28, 2013, the licensee failed to provide alternative shutdown capability free of fire damage in the event of a fire in Fire Areas DD and FF. Specifically, the licensee failed to provide electrical protection for battery charger ammeter circuits to prevent a secondary fire and damage to safe shutdown cables or components located outside the fire area (i.e., low voltage switchgear rooms) in the event of a fire in the control room or the cable spreading room. The licensee is in transition to NFPA 805 and; therefore, the NRC-identified violation was evaluated in accordance with the criteria established by Section A of the NRCs Interim Enforcement Policy Regarding Enforcement Discretion for Certain Fire Protection Issues (10 CFR 50.48) for a licensee in NFPA 805 transition. The inspectors determined that for this violation: (1) the licensee would have identified the violation during the scheduled transition to 10 CFR 50.48(c); (2) the licensee had established adequate compensatory measures within a reasonable time frame following identification and would correct the violation as a result of completing the NFPA 805 transition; (3) the violation was not likely to have been previously identified by routine licensee efforts; and (4) the violation was not willful. The finding also met additional criteria established in Section 12.01.b of Inspection Manual Chapter (IMC) 0305, Operating Reactor Assessment Program. In addition, in order for the NRC to consider granting enforcement discretion the violation must not be associated with a finding of high safety significance (i.e., Red). Therefore, the licensee performed a risk evaluation following the guidelines in IMC 0609, Appendix F, and determined that this issue was not associated with a finding of high safety significance. The inspectors reviewed this evaluation and found it acceptable. In addition, the licensee entered this issue into their Corrective Action Program as CR-2013-02965. As a result, the inspectors concluded that the violation met all four criteria established by Section A and the NRC was exercising enforcement discretion to not cite this violation in accordance with the Interim Enforcement Policy Regarding Enforcement Discretion for Certain Fire Protection Issues. |
| Site: | Davis Besse  |
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| Report | IR 05000346/2013008 Section 1R05 |
| Date counted | Jun 30, 2013 (2013Q2) |
| Type: | Violation: Green |
| cornerstone | Initiating Events |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | R Daley R Langstaff R Winter A Dahbur |
| Violation of: | 10 CFR 50 Appendix R 10 CFR 50.48 |
| INPO aspect | |
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Finding - Davis Besse - IR 05000346/2013008 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Davis Besse) @ 2013Q2
Self-Identified List (Davis Besse)
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