05000261/FIN-2012002-02
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Finding | |
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| Title | Inadequate Design Change Resulted in Interference and Inoperability of Containment Water Level Indication |
| Description | The inspectors identified a Green NCV of 10 CFR 50, Appendix B, Criterion III, Design Control, for the licensees installation of a plant modification that adversely affected the operability of nearby safety related equipment. Specifically, the licensees installation of radiation barriers in containment impeded the travel path for equipment associated with containment water level transmitter, LT-802E, and resulted in the B train of containment sump water level instrumentation being inoperable for a period of time greater than allowed in Technical Specification 3.3.3. The licensee took immediate actions to remove the interference with the level instrumentation. This issue was entered into the licensees corrective action program as NCR 510240. The licensees installation of a plant modification that adversely affects the operability of nearby safety related equipment was a performance deficiency and resulted in containment water level transmitter, LT-802E, being inoperable for greater than the allowed outage time specified in Technical Specification 3.3.3. The performance deficiency was considered more than minor because it affected the Mitigating Systems Cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences (i.e. core damage). Specifically, reactor operators would have unreliable indication of containment water level during a postulated Loss of Coolant Accident (LOCA). Using Manual Chapter 0609.04, Phase 1 Initial Screening and Characterization of Findings, the issue was evaluated to be a degradation of the Mitigation Systems cornerstone because it affects long term core decay heat removal in the event of a LOCA. Table 4a of the Phase 1 worksheet requires a Phase 2 significance determination evaluation, because the finding represents an actual loss of safety function of a single train, for greater than its Technical Specifications Allowed Outage Time. A further characterization of the safety significance could not be performed in Phase 2 because the function (i.e., containment water level indication) was not modeled and necessitated that a Phase 3 SDP be done. The SRA performed a bounding event assessment. The dominant accident sequence was where a LOCA occurs and, as a result of the depressurization, a Steam Generator Tube Rupture happens. This leads to the water from the steam generator adding to the internal flooding event. Subsequently operators fail to isolate the ruptured steam generator thus continuing to feed the break. The increase in core damage probability (ACDF) for this event was determined to be < 1E-6 therefore, this condition should be treated as very low safety significance (Green). The inspectors did not identify a crosscutting aspect associated with this finding because the performance deficiency occurred in 2005 and does not represent current licensee performance. |
| Site: | Robinson  |
|---|---|
| Report | IR 05000261/2012002 Section 1R15 |
| Date counted | Mar 31, 2012 (2012Q1) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.15 |
| Inspectors (proximate) | A Nielsen R Hamilton L Lake J Hickey R Musser P Lessard C Scott J Rivera A Sengupta W Pursley |
| INPO aspect | |
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Finding - Robinson - IR 05000261/2012002 | |||||||||||||||||||||||||||||||||||||||||
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Finding List (Robinson) @ 2012Q1
Self-Identified List (Robinson)
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