05000313/FIN-2009005-08
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Finding | |
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| Title | Failure to Appropriately Scope Floor Drains in the Stations Maintenance Rule Monitoring Program |
| Description | The inspectors identified an unresolved item associated with the licensees failure to appropriately monitor nonsafety-related structures, systems, and components whose failure could prevent safety-related components from fulfilling their safety-related function. The inspectors reviewed Station Calculation CALC-01-EQ-1001-01, MFW Critical Crack HELB Analysis, Revision 0. During this review the inspectors noted that (1) Door 19, a high energy line break door, was credited with isolating the emergency feedwater pumps from a harsh environment in the event of a main feedwater critical crack high energy line break event, (2) the door was assumed to remain closed as long as the differential pressure across the door remained less than 1 psid during the event, (3) the atmospheric pressure calculated in the room during the high energy line break event was 0.8 psi, and (4) a water accumulation in the room during the event was predicted to be 6 inches. The inspectors questioned the predicted value for water accumulation based on the assumed geometry of the crack in the feedwater piping. Further review of the calculation and discussions with station design engineers revealed that this water accumulation value was based on the modeling assumption that the drains were 4-inch openings which connected to other rooms through the drain system. The premise of this assumption was that the larger drain size would model the potential effects of steam transmission to other rooms through the floor drain system, therefore, determining if another room would have a potentially harsh environment created during this event. The inspectors questioned the validity of this modeling assumption. While it would be conservative for predicting potentially harsh environments in adjacent rooms, it appeared to be nonconservative for predicting the amount of water that would pool in the room and apply pressure to Door 19. With the drains modeled as 4-inch openings, the results appeared to under estimate the amount of water that would pool in this room. The inspectors determined that the amount of water that would pool in the room was important to determining whether Door 19 would be forced open during a main feedwater critical crack high energy line break event. Specifically, the pressure applied to Door 19 from the atmospheric pressure change due to the high energy line break event, in conjunction with the pressure that would be felt by the door due to water accumulation could potentially exceed 1 psid, and this would cause the door to open and expose the emergency feedwater pumps to a harsh environment. The inspectors informed the licensee of their concerns. The licensee initiated Condition Report CR-ANO-1-2009-1421 to address these concerns. The inspectors determined that the potential vulnerability to the Unit 1 emergency feedwater pumps during a main feedwater critical crack high energy line break event will be treated as an unresolved item pending further inspector review of the licensees analysis. 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 the ability of high energy line break Door 19 to remain shut during a main feedwater critical crack event. Additional information was needed to determine whether a violation of regulatory requirements occurred. Pending further review of additional information provided by the licensee, this issue is being treated as an Unresolved Item 05000313/2009008-08, Failure to Appropriately Scope Floor Drains in the Stations Maintenance Rule Monitoring Program |
| Site: | Arkansas Nuclear  |
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| Report | IR 05000313/2009005 Section 4OA2 |
| Date counted | Dec 31, 2009 (2009Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | A Sanchez G Guerra J Clark J Rottona Sanchezg Werner J Clark J Josey M Haire M Shannon N O'Keefe R Azua S Rotton T Farnholtz |
| INPO aspect | |
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Finding - Arkansas Nuclear - IR 05000313/2009005 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Arkansas Nuclear) @ 2009Q4
Self-Identified List (Arkansas Nuclear)
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