05000456/FIN-2010003-01
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Finding | |
|---|---|
| Title | Degraded Condition of Reactor Head Vent Valves |
| Description | A finding of very low safety significance was self-revealed on July 30, 2009, after the Unit 2 reactor tripped due to a trip of the 2C reactor coolant pump on overcurrent. The 2C reactor coolant pump tripped on overcurrent following an automatic bus transfer due to the loss of station auxiliary transformer 242-1 on a sudden pressure relay actuation. Subsequent investigation identified the cause of the 2C reactor coolant pump trip to be incorrect setpoints on the reactor coolant pump overcurrent relays. The inspector determined that this cause was not a violation of NRC requirements since the overcurrent trip function of the reactor coolant pump is not a safety-related function. The licensee entered this condition into their corrective action program. Corrective actions included: increasing the Unit 2 reactor coolant pump overcurrent relay dropout values from 75 to 90 percent, adjustment of the 2C reactor coolant pump overcurrent time delay setting, extent of condition review for Unit 1 during their next scheduled refuelling outage (Fall 2010), and a revision of station procedures to include periodic calibration of the reactor coolant pump overcurrent relays. This performance deficiency was considered more than minor because it impacted the Configuration Control attribute of the Initiating Events Cornerstone objective to limit the likelihood of those events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. The inspectors performed a Phase 1 Significance Determination Process review for this finding using the guidance provided in IMC 0609, Attachment 4, Initial Screening and Characterization of Findings. Based on Tables 2, Cornerstones and Functions Degraded as a Result of the Deficiency, and 3b, Significance Determination Process Phase 1 Screening Worksheet for Initiating Events, Mitigation Systems, and Barriers Cornerstones, in IMC 0609, Attachment 4, the inspectors determined the finding was a transient initiator contributor in the Initiating Events Cornerstone. The inspectors answered No to the Transient Initiators question in the Initiating Events Cornerstone Column of IMC 0609, Attachment 4, Table 4a, Characterization Worksheet for Initiating Event, Mitigating System, and Barrier Integrity Cornerstones, and determined that the issue was of very low safety significance. No 2 Enclosure cross-cutting aspects were assigned to this issue since the performance deficiency was not reflective of current performance. |
| Site: | Braidwood  |
|---|---|
| Report | IR 05000456/2010003 Section 1R12 |
| Date counted | Jun 30, 2010 (2010Q2) |
| Type: | URI: Green |
| cornerstone | Initiating Events |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71111.12 |
| Inspectors (proximate) | M Holmberg M Perry M Thorpe Kavanaugh N Feliz Adomo R Jicklin R Ng T Go B Metrow B Palagi D Betancourt D Jones E Duncan J Benjamin J Dalzell J Robbinsj Benjamint Go M Perry A Garmoe R Skokowski C Scott S Bakhsh V Meghani C Lipa |
| INPO aspect | |
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Finding - Braidwood - IR 05000456/2010003 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Braidwood) @ 2010Q2
Self-Identified List (Braidwood)
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