05000498/FIN-2008008-02
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Finding | |
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| Title | Potential Loss of Centrifugal Charging Pump Suction Due to Fire Damage |
| Description | The team identified an unresolved item associated with License Condition 2.E concerning a potential failure to adequately implement the approved fire protection program. Specifically, the team identified that the licensees fire protection program may not have ensured that the charging pump relied on for achieving post-fire safe shutdown would not be damaged because of a loss of suction. During a post-fire safe shutdown, the charging pump would be necessary to support the reactivity control and reactor coolant makeup functions by providing the reactor coolant system borated water from the refueling water storage tank. The team identified that fire damage to unprotected cables for either of the motor operated valves in the normal suction path had the potential to cause the associated valve to close, which could damage the running pump. During normal plant operations, the chemical and volume control system operates to allow a continuous feed (charging and seal injection) and bleed (letdown and seal leak-off) for the reactor coolant system. Normally one centrifugal charging pump is in operation. In the event of fire, inventory makeup is intended to be accomplished using a centrifugal charging pump by switching to the refueling water storage tank as a source of borated water. Procedure 0POP04-ZO-0009, Safe Shutdown Fire Response, included steps to swap the suction path from the normal suction source to the refueling water storage tank without securing the running charging pump. However, the team determined that if the charging pump credited for safe shutdown was running at the time of the fire, a spurious closure of either one of the two series-connected volume control tank outlet valves (1-MOV-112B or 1-MOV-113A) could result in a loss of suction and damage to the credited charging pump. The post-fire safe shutdown strategy developed by the fire protection program was intended to assure the availability of only one charging pump in fourteen fire areas. The team identified thirteen of these fire areas (Fire Areas 03, 04, 20, 24, 25, 26, 27, 31, 32, 33, 34, 65 and 67) also contain unprotected cables that had the potential to spuriously close at least one of the volume control tank outlet valves (MOV-112B or MOV-113A) due to fire damage. Instructions in Procedure 0POP04-ZO-0009 for each of these fire areas direct the control room operators to place the control switches for both centrifugal charging pumps to the pull-to-lock position to secure the pumps and prevent potential restarting until their suction is aligned to the refueling water storage tank. The team determined that the assumed success of this action was based on an unverified assumption that circuit damage would not occur prior to 10 minutes after control room operators decided to enter Procedure 0POP04-ZO-0009. Entry into Procedure 0POP04-ZO-0009 is based on satisfying criteria provided on the Conditional Information Page of Procedure 0POP04-ZO-0008, Fire/Explosion. The entry conditions for Procedure 0POP04-ZO-0008 are: (1) Verbal report of a fire or an explosion from a person at the scene, or (2) Alarm on the Fire Protection Computer with confirmation of an actual fire in the affected area by an operator dispatched to the fire area. Step 6.0 of Procedure 0POP04-ZO-0008 states, Station the STA (Shift Technical Advisor) in the affected unit to monitor the Conditional Information Page (CIP) until fire is out or transition to Procedure 0POP04-ZO-0009, Safe Shutdown Fire. The procedures would create a time delay between the start of a fire and the decision to initiate a plant shutdown. The team was concerned that fire damage to unprotected cables could spuriously close a volume control tank outlet valve prior to the control room operators securing the credited centrifugal charging pump in accordance with Procedure 0POP04- ZO-0009. |
| Site: | South Texas  |
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| Report | IR 05000498/2008008 Section 1R05 |
| Date counted | Sep 30, 2008 (2008Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.05 |
| Inspectors (proximate) | P Qualls R Mullikin B Correll J Mateychick K Sullivan N O'Keefej Dixonc Smith B Tharakan C Graves G Pick W Walker J Mateychick N Okonkwo J Watkins |
| INPO aspect | |
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Finding - South Texas - IR 05000498/2008008 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (South Texas) @ 2008Q3
Self-Identified List (South Texas)
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