05000390/FIN-2018010-02
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Finding | |
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| Title | Potential Failure to Perform a 50.59 Evaluation for Auxiliary Building and Containment Isolation |
| Description | DCN 66459 added relays and wiring to change the actuation system that initiated the Auxiliary Building Isolation (ABI) and Containment Ventilation Isolation (CVI) protective functions. The new control elements (relay contacts and wiring) bypassed the Unit Solid State Protection System (SSPS) circuitry. The intent was to actuate the CVI function on an ABI actuation from the opposite unit while it was at full power operation and the other unit was in refueling mode. By bypassing the refueling units protection system and controlling the components in the refueling unit, the modification in effect made the protection systems (CVI) a shared system. The CVI was classified as part of the Engineered Safeguards Protection Systems (ESFAS). The ESFAS was not listed in the UFSAR Chapter 3.1.2 WBNP Conformance with GDCs [General Design Criteria], as shared systems under GDC 5. The UFSAR compliance with GDC 5 Sharing of Structures, Systems, and Components, specified all shared systems are sized for all credible initial combinations of normal and accident states for the two units, with appropriate isolation to prevent an accident condition in one unit from carrying into the other. The new control elements integrated in the ESFAS logic, apparently on both units. The licensee did not perform a failure modes and effects analysis to determine the negative effects that could degrade the ESFAS isolation functions when they are required to operate. The inspectors are concerned that the integration of the two ESFAS circuitry could have a detrimental effect. Additional failure modes appear to have been introduced into these systems. The inspectors need to determine the extent to which each units protection system and CVI were exposed to additional failures including common cause failures to determine whether there could be more than a minorissue and a potential failure to perform an adequate 50.59 evaluation in accordance with NPG-SPP-09.3 Plant Mods and Engineering Change Control,Section III, was a performance deficiency. This URI, is being opened to determine whether the PD is more than minor. This modification was complete on June 16, 2017. This issue was captured in CR 1398935, Potential violation of 10 CFR 50.59(d)(1) via DCN 66459. |
| Site: | Watts Bar  |
|---|---|
| Report | IR 05000390/2018010 Section NO CC AREA |
| Date counted | Mar 31, 2018 (2018Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 1R17 |
| Inspectors (proximate) | 71111.1 |
| Violation of: | Pending |
| INPO aspect | NO SL |
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Finding - Watts Bar - IR 05000390/2018010 | |||||||||||||||||||||||||||||||||||||||
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Finding List (Watts Bar) @ 2018Q1
Self-Identified List (Watts Bar)
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