05000425/FIN-2010006-02
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Finding | |
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| Title | Licensing Basis for Multiple Spurious Operations and Adequacy of Related Compensatory Measures |
| Description | The team identified a URI concerning the licensing basis for multiple spurious operations (MSOs) and adequacy of related compensatory measures implemented to address potential noncompliances related to multiple circuit faults. Description: As documented in the Background section of Enforcement Guidance Memorandum (EGM) 09-02, Enforcement Discretion for Fire-induced Circuit Faults, dated May 14, 2009, the matter of how many fire-induced circuit faults need be postulated in post-fire SSAs has been an industry-wide generic issue. With the issuance of Regulatory Guide (RG) 1.189, Revision 2, Fire Protection for Nuclear Power Plants, in October of 2009, the generic issue has been resolved, and the guidelines disseminated to all power reactor licensees regarding what constitutes an acceptable multiple circuit fault analysis. The inspection team confirmed that VEGP has performed an acceptable analysis. Refer to Section 4OA5 of this report for details of that analysis. As a result of than analysis, the licensee identified 78 MSO scenarios that apply to VEGP. Each scenario on this list may represent a non-compliance with the Operating License Condition 2.G and the requirement to ensure one train of SSD equipment and associated circuits (that could adversely affect SSD) would be free of fire damage in the event of a fire. This list of potential noncompliances related to MSOs was entered into the corrective action program, identified as a degraded, but operable, condition, and compensatory measures were posted. The team examined MSO Scenario 1: loss of all RCP seal cooling due to spurious closure of RCP 1 seal water inlet valve 1-HV-1803A concurrent with spurious isolation of auxiliary component cooling water (ACCW) to the RCP thermal barrier heat exchanger. If this MSO were to occur, with the RCP running, an RCP seal loss-of-coolant-accident would result. Isolation of ACCW to the RCP thermal barrier heat exchanger could occur due to spurious closure of either ACCW supply isolation valve 1-HV-1978 or ACCW return isolation valve 1-HV-1974. Both the ACCW valves are located inside containment, and all three valves (1-HV-1803A, 1-HV-1978, and 1-HV-1974) are motoroperated valves. Cable 1BBD26SB in the control circuit for valve 1-HV-1803A could cause spurious closure of that valve if fire-induced short-circuit between wires X1 and T2 occurred. This cable runs from termination cabinet 1ACPT10 in the Train B cable spreading room to motor control center (MCC) 1BBD located in the control building. Cable 1BBE25SB in the control circuit for valve 1-HV-1978 could cause spurious closure of that valve if fire-induced short-circuit between wires X1 and T2 occurred. Cable 1BBE24SB in the control circuit for valve 1-HV-1974 could cause spurious closure of that valve if fire-induced short-circuit between wires X1 and T2 occurred. Cables 1BBE25SB and 1BBE24SB run from termination cabinet 1ACPT04 in the Train B cable spreading room to MCC 1BBE in the auxiliary building. Termination cabinets 1ACPT10 and 1ACPT04 are in the same row of termination cabinets. Cable 1BBD26SB (associated with RCP 1 seal water valve 1-HV-1803A), cable 1BBE25SB (associated with ACCW valve 1-HV-1978) and cable 1BBE24SB (associated with ACCW valve 1-HV-1974) are routed in cable trays above the termination cabinet line-up, and are in close proximity. Since the termination cabinets are considered a fire ignition source, all three of these cables could be damaged by fire. Therefore, MSO Scenario 1 could occur due to a fire at termination cabinets 1ACPT 04 through 1ACPT10. The applicable SSD procedure for a fire in the Unit 1, Train B, cable spreading room (17103A-C, Annunciator Response Procedures for Fire Alarm Computer) did not include a step to trip RCP 1, nor take any other action to mitigate the potential for loss of all seal cooling to RCP 1. Enforcement Guidance Memorandum (EGM) 09-002 provides guidance for granting enforcement discretion for non-compliances involving the use of unapproved operator manual actions (OMAs) to address multiple circuit faults. Specifically, to be eligible for this enforcement discretion, by April 2010, licensees were to (1) identify noncompliances related to MSOs, (2) implement compensatory measures for the noncompliances, and (3) place the noncompliances in the corrective action program. If granted, enforcement discretion would continue until October 2012 to allow time for licensees to resolve the noncompliances related to MSOs. The Vogtle FPP specifies that as a compensatory measure, an hourly fire watch be implemented in FAs where a fire barrier is degraded. This requirement is applicable to the licensees list of potential noncompliances related to MSOs, because if these cables were protected from fire damage by a fire barrier (using a 3- hour rated barrier, one-hour rated barrier with detection and suppression, or 20 feet of separation with detection and suppression), the MSO scenario would be precluded from happening. However, the licensee modified its FPP, to allow for the use of operator rounds as a compensatory measure, specifically to address the MSO concerns. The justification given for this change was that Regulatory Issue Summary 2005-007, Compensatory Measures to Satisfy Fire Protection Program Requirements, recognizes the acceptability of alternate compensatory measures. While this is true, the alternate compensatory measures must be equivalent or adequately compensate for the degradation. In the case of using a fire watch as a compensatory measure for the MSO concerns, the specific location of the degraded fire barrier is not known beyond the fact that it is somewhere in the fire area. The operator rounds take place once per 12-hour shift, and can take place any time during the shift. Therefore significantly more than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> may elapse between performing the fire watch function as part of the operator rounds. The team also found that the operator rounds will not cover all the rooms affected by the MSO concerns. Specifically, the rooms involved in MSO Scenario 1 would not all be covered by operator rounds. In addition, the operator is not instructed to walkdown the entire floor area of each area he/she enters as part of the regular rounds; therefore, MSO areas of concern may not be observed by the operator. Furthermore, the team noted that a portion of operator rounds can be cancelled during a particular shift due to emergent plant conditions. For these reasons, the team concluded that the compensatory measures implemented at Vogtle for the MSO concerns did not constitute sufficient compensation as intended by EGM-09-002. When the NRC inspection team communicated to the licensee that the use of operator rounds as described above was not an acceptable substitute for hourly fire watch, the licensee countered that their list of MSO scenarios did not represent any noncompliances, as the consideration of multiple circuit faults was outside the design basis for Vogtle. To substantiate this position, the licensee cited portions of Appendix 9B of the UFSAR, which is a line by line comparison of the CMEB 9.5-1 requirements against the Vogtle compliance position including clarification of conformance or justification of deviation. The team concluded that further review of information related to the plant licensing basis is necessary in order to determine whether, or to what extent, multiple circuit fault scenarios must be considered as part of the Vogtle FPP. This licensing basis issue was referred to the Office of Nuclear Reactor Regulation for review. Even though the licensee has performed an analysis which considers MSOs, the question of the licensing basis is important to the question of whether or not the compensatory measures put in place for the newly-identified potential noncompliances related to MSOs are acceptable. This issue will be identified as URI 05000424; 425/2010006-02, Licensing Basis for Multiple Spurious Operations and Adequacy of Related Compensatory Measures. |
| Site: | Vogtle  |
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| Report | IR 05000425/2010006 Section 1R05 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | URI: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | A Dahbur B Metzger F Ehrhardt G Wiseman H Barrett M Thomas P Braxton P Fillion R Neaser Rodriguezm King D Jones K Ellis J Montgomery P Braxton J Dymek |
| INPO aspect | |
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Finding - Vogtle - IR 05000425/2010006 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Vogtle) @ 2010Q3
Self-Identified List (Vogtle)
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