05000346/FIN-2016003-03
Finding | |
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| Title | Licensee-Identified Violation |
| Description | Plant TS 3.3.16, Anticipatory Reactor Trip System (ARTS) Instrumentation, requires that three ARTS channels for the main turbine trip function be maintained operable with the unit operating in Mode 1 above 45 percent power, and three ARTS channels for the SFRCS / main feed pump trip function be maintained operable with the unit operating in Mode 1 at any power. While this TS provides actions and allowed outage time for a single inoperable ARTS channel, there are no provisions for more than a single ARTS channel being simultaneously inoperable. The provisions of TS Limiting Condition for Operation 3.0.3, therefore, apply when more than one ARTS channel is inoperable at the same time, and require that actions be initiated within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from the onset of the condition to
Be in Mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> Be in Mode 4 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />; an Be in Mode 5 within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br /> As discussed in Section 4OA3.5 of this report, contrary to the requirements of TS 3.3.16, all four ARTS channels were bypassed and inoperable for both the main turbine and SFRCS functions for a period of approximately 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> on May 910, 2016. The objective of the Mitigating Systems Cornerstone of Reactor Safety is to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences (i.e., core damage). Key attribute associated with this objective are human performance and configuration control. In accordance with NRC IMC 0612, Power Reactor Inspection Reports, Appendix B, Issue Screening, the inspectors determined that the violation was of more than minor significance in that it had a direct impact on this cornerstone objective. Specifically, plant operators in failing to adequately implement applicable operating procedures allowed the unit to enter into a mode of operation with less that the required three channels of ARTS operable and available. Using Exhibit 2 Mitigating Systems Screening Questions, the inspectors determined that a detailed risk analysis by the NRC Region III SRA was required since the issue involved the inoperability of more than one channel of ARTS, a condition for which there is no allowed outage time specified in TS 3.3.16. The SRA used the Davis-Besse SPAR Model, Version 8.19, and SAPHIRE, Version 8.1.4, for the calculation of the change in CDF for the issue. The following assumptions were made in the analysis: The exposure time for the issue was conservatively assumed to be 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> from 3:24 p.m. on May 9, 2016, when the unit entered Mode 1 and the TS 3.3.1 for the ARTS became applicable to 5:52 a.m. on May 10, 2016, when the ART bypass switches were returned to the normal/enabled state; an With the ARTS SFRCS function bypassed, the SFRCS input to the ARTS t provide a reactor trip signal was bypassed. Since the ARTS is not modeled i the SPAR model, it was very conservatively assumed that the RPS automati trips were bypassed during the 15hour exposure time, and only a manua reactor trip was available The result was a change in CDF of 7.6E7 events per year. The dominant core damage sequence was a transient initiating event with a failure of plant operators to manually trip the reactor, along with a failure of plant operators to initiate emergency RCS boration. Based on the detailed risk evaluation, the inspectors determined that the violation was of very low safety-significance (Green). As discussed in Section 4OA3.5 of this report, the licensee had entered this issue into their CAP as CR 201606563. In addition to the commissioning of a formal root cause evaluation, licensee corrective actions included the issuance of an operations standing order to require periodic walk downs of all control room panels by on-watch control room operators in pairs to ensure a comprehensive understanding of plant status awarenes and enhancements to applicable operating procedures. |
| Site: | Davis Besse  |
|---|---|
| Report | IR 05000346/2016003 Section 4OA7 |
| Date counted | Sep 30, 2016 (2016Q3) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | Licensee-identified |
| Inspection Procedure: | |
| Inspectors (proximate) | D Kimble J Cameron J Cassidy J Rutkowski M Garza N Valos T Briley |
| Violation of: | Technical Specification |
| INPO aspect | |
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Finding - Davis Besse - IR 05000346/2016003 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Davis Besse) @ 2016Q3
Self-Identified List (Davis Besse)
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