05000336/FIN-2015007-01
From kanterella
Jump to navigation
Jump to search
Finding | |
|---|---|
| Title | Reactor Building Closed Cooling Water System Pump Oil Leakage Results in Technical Specification Inoperability |
| Description | The team identified a non-cited violation (NCV) of Millstone Power Station Unit 2, Technical Specification (TS) 3.7.3.1 the reactor building component cooling water (RBCCW) system Limiting Condition of Operation (LCO) in that Dominion failed to maintain two loops of RBCCW operable. The team found that following the identification of a degraded condition for the C RBCCW pump, Dominion incorrectly concluded the loop remained operable. Specifically, the team determined that from February 4 to February 23, 2015, the RBCCW B loop was inoperable because oil leakage from the C RBCCW outboard pump bearing would have caused the complete loss of oil to the pump bearing, without operator compensatory action, before the C RBCCW train would have completed its design basis 30-day mission time. Using IMC 0609, Appendix A, Exhibit 2, Mitigating Systems Screening Questions, Section A, Mitigating Systems, Structures or Components and Functionality, the team determined that the finding required a detailed risk evaluation due to actual loss of function of at least a single train for greater than its TS allowed outage time. The Region I Senior Reactor Analyst (SRA) identified that because the finding involved the C RBCCW pump function to run for its mission time, the only accident events adversely impacted are the large break loss of coolant accident (LLOCA) sequences. The condition was conservatively modeled assuming an exposure period of one year with the C RBCCW pump failure to run basic event set to True. The resultant change in risk was estimated at mid E-8, or very low safety significance (Green). The dominated risk sequences involve a LLOCA with the failure of the remaining RBCCW pumps due to common cause. Since the estimated risk increase was less than 1E-8, no additional evaluation of external events contribution or change in large early release frequency (LERF) was required. The team concluded that this issue has a cross-cutting aspect in the Human Performance cross-cutting area of Conservative Bias: Individuals use decision-making practices that emphasize prudent choices over those that are simply allowable. A proposed action is determined to be safe in order to proceed, rather than unsafe in order to stop. Specifically, Dominion determined that the qualitative bubbler leak rate was acceptable without evaluation against quantified operability criteria. |
| Site: | Millstone  |
|---|---|
| Report | IR 05000336/2015007 Section 1R21 |
| Date counted | Jun 30, 2015 (2015Q2) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | G Morris J Ayala J Patel K Mangan L Mckown P Krohn S Pindale W Sherbin |
| Violation of: | Technical Specification |
| CCA | H.14, Conservative Bias |
| INPO aspect | DM.2 |
| ' | |
Finding - Millstone - IR 05000336/2015007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Finding List (Millstone) @ 2015Q2
Self-Identified List (Millstone)
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||