05000336/FIN-2007007-01
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Finding | |
|---|---|
| Title | Control Room Fire Evacuation Procedure |
| Description | Pending further inspector review of control room fire scenario developments, the team identified a potential vulnerability in Dominions safe shutdown method and operating procedures during a control room fire scenario that would require evacuation. Specifically, the reactor coolant makeup and reactor coolant pump seal injection functions of the charging pumps were potentially affected. The team reviewed 25212-BTP-9.5-1, MP3 Branch Technical Position 9.5-1 Compliance Report, Rev. 003, and noted that the charging pump volume control tank (VCT) outlet level control valves were subject to spurious operation during a control room fire. The team questioned engineers regarding the validity of this conclusion and if Dominion considered the impact of the VCT outlet isolating the suction path to an operating charging pump during the time necessary to evacuate the control room and to establish control at the auxiliary shutdown panel. The engineers confirmed that a VCT outlet level control valve spurious closure was possible for a control room fire and that an operating charging pump would fail in a relatively short time without a suction path. Dominion also provided the team condition reports, CR-04-08399 and CR-04-08450, that were initiated on September 16, 2004, for the same potential issue the inspectors raised: catastrophic failure of an operating charging pump due to loss of a suction path from a spurious closure of the VCT outlet level control valves. Only two charging pumps, A and B, were analyzed for safe shutdown, and only the A charging pump could be operated remotely for a fire requiring control room evacuation. The third charging pump, C, was available but was normally secured without a 4kV breaker installed. The team noted that the C charging pump was also not analyzed for safe shutdown. Dominions safe shutdown analysis for a Unit 3 control room fire only credited the A charging pump for boration and reactor coolant pump (RCP) seal injection functions. The team further identified that Kirk interlock keys were not available outside of the main control to rack in a normally disconnected 4kV breaker to the C charging pump. Regarding the potential issue, Dominion completed several immediate corrective actions including: equipment configuration changes (i.e., 4kV breaker alignments and kirk interlock key locations were implemented) to ensure the C charging pump would remain available after such a scenario, operators were notified of the condition through a night order entry, fire protection compensatory measures were initiated to minimize the potential for a fire in the areas of concern, and an extent of condition review was performed to identify additional plant areas where this potential vulnerability may exist. Dominion entered the issue into the corrective action program as CR-07-10124, CR-07- 10158, CR-07-10363, and CR-07-10614. The team determined that the potential vulnerabilities to the reactor coolant makeup and RCP seal injection functions during a control room fire that required evacuation will be treated as an unresolved item (URI), pending further inspector review of credible fire scenarios and their potential impact on the VCT outlet valve control cabling. An unresolved item is an issue requiring further information to determine if it is acceptable, if it is a finding, or if it constitutes a violation of NRC requirements. In this case, additional NRC inspection will be required to assess credible control room fire scenarios that lead to a loss of reactor coolant makeup and conditions that may require control room evacuation |
| Site: | Millstone  |
|---|---|
| Report | IR 05000336/2007007 Section 1R05 |
| Date counted | Dec 31, 2007 (2007Q4) |
| Type: | URI: |
| cornerstone | Initiating Events |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | M Patel D Orr J Tifftt Moslakj Lilliendahl J Benjamin J Krafty D Orr S Shaffer B Norris J Commiskey H Gray E Burket |
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Finding - Millstone - IR 05000336/2007007 | |||||||||||||
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Finding List (Millstone) @ 2007Q4
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