05000261/FIN-2009003-03
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Finding | |
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Title | Failure to address environmental conditions associated with freeze-protection temperature sensors. |
Description | A green self-revealing finding was identified for the licensees failure to identify the environmental conditions that temperature sensors in certain freeze-protection circuits could experience after routine installation of cold-weather enclosures during cold-weather operation. Although a violation of regulatory requirements was not identified, this failure was a performance deficiency with respect to the licensees procedure EGR-NGGC-0005 (Engineering Change) which requires, in part, that the licensee identify the functional performance requirements of each structure, system and component being modified in all possible operational configurations. In this circumstance, the licensees modification to the freeze-protection circuits for the steam generator power operated relief valve sensing lines, installed the freeze-protection temperature sensors in a location where a heated enclosure is routinely installed for cold-weather protection. With the heated enclosure surrounding the temperature sensors the freeze protection circuitry failed to energize during freezing conditions and subsequently allowed the sensing line for the B steam generator power operated relief valve to freeze, which in turn caused the B steam generator power operated relief to open at full power operation. This finding is in the licensees corrective action program as AR 339914. At the end of this inspection period, the licensee had not yet completed their evaluation of this finding, and had consequently not yet developed corresponding corrective actions. This finding is more-than-minor because it is associated with the Equipment Performance attribute of the Initiating Events cornerstone and affected the cornerstone objective of limiting the likelihood of those events that upset plant stability and challenge critical safety functions during power operations, in that this finding created conditions which caused an event that upset plant stability during power operations. Using Appendix A of the Significance Determination Process (SDP) described in MC 0609, this finding did not screen as green because it was a transient initiator contributor and because the finding contributed to both the likelihood of a reactor trip and the likelihood that mitigation equipment or functions will not be available, in that this finding created conditions that caused a S/G PORV to open during power operation, and rendered inoperable the automatic functions of that PORV. A regional Senior Reactor Analyst performed a Phase 3 evaluation under the Significance Determination Process. The performance deficiency was determined to be of very low safety significance (Green). The evaluation was accomplished using the NRCs Probabilistic Risk Assessment computer model of the plant with basic event MSS-ADV-CC-RV1-2, FAILURE OF SG-B PORV RV1-2, set to always fail. The model was quantified with a one day exposure period. The dominant accident sequences involved Steam Generator Tube Ruptures with complications, partially due to the finding, in depressurizing and cooling down. Consequently, the Residual Heat Removal System was not placed into service resulting in core damage and a Large Early Release. The major assumptions included that recovery of the failed component was possible and common cause inclusion was not appropriate. This finding has a cross-cutting aspect in the Resources component of the Human Performance area because the licensee did not provide and ensure that complete, accurate, up-to-date design documentation were available and adequate to plant personnel, in that the licensee did not ensure that Attachment 7 to EGR-NGGC- 005 was adequate to enable engineers to identify a potential interference between the modification described in EC 70032 and the program described in OP-925 (Cold Weather Preparations). (H.2(c)) (Section 4OA2.2 |
Site: | Robinson |
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Report | IR 05000261/2009003 Section 4OA2 |
Date counted | Jun 30, 2009 (2009Q2) |
Type: | Finding: Green |
cornerstone | Initiating Events |
Identified by: | Self-revealing |
Inspection Procedure: | IP 71152 |
Inspectors (proximate) | M Bates A Vargas-Mendez J Polickoski R Hagar R Musser J Zeiler E Morris C Fletcher N Smith |
CCA | H.7, Documentation |
INPO aspect | WP.3 |
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Finding - Robinson - IR 05000261/2009003 | |||||||||||||||||||||||||||||||||||||
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Finding List (Robinson) @ 2009Q2
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