05000289/FIN-2018001-03
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Finding | |
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| Title | Licensee-Identified Violation |
| Description | This violation of very low safety significancewas identified by the licensee and has been entered into the licensee corrective action program and is being treated as a Non-Cited Violation, consistent with Section2.3.2 of the Enforcement Policy.Violation: 10 CFR 50.63(c)(2) states, in part, that the alternate ac power source will constitute acceptable capability to withstand station blackout provided an analysis is performed which demonstrates that the plant has this capability from onset of the station blackout until the alternate ac source and required shutdown equipment are started and lined up to operate. The time required for startup and alignment of the alternate ac power source and this equipment shall be demonstrated by test. If the alternate ac source can be demonstrated by test to be available to power the shutdown buses within 10 minutes of the onset of station blackout, then no coping analysis is required. The Three Mile Island Unit 1 Station Blackout Evaluation Report 990-1879 identifies the station blackout (SBO) diesel generator as the alternate ac power source for the unit. Contrary to the above, from January 11, 2018, to January 12, 2018, the Three Mile Island Unit 1 alternate ac power source did not constitute acceptable capability to withstand station blackout. Specifically, during this timeframe, the SBO diesel generator was rendered unavailable due to fire service valve FS-V-225 being closed with no dedicated operator to reopen the valve. The time required for startup and alignment of the SBO diesel generator in this configuration had not been demonstrated by test to be available to power the shutdown buses within 10 minutes of the onset of station blackout.Significance/Severity Level: The inspectors evaluated this finding using IMC 0609.04, Initial Characterization of Findings, and IMC 0609, Appendix A, Exhibit 2, Mitigating Systems Screening Questions. The inspectors determined that the finding required a detailed risk evaluation due it representing an actual loss of function of one non-Technical Specification train of equipment designated as high safety-significance for more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. A Region I senior reactor analyst completed the detailed risk evaluation and estimated the increase in core damage frequency (CDF) associated with this performance deficiency to be 7E-8/yr or of very low safety significance (Green). The senior reactor analyst used the Systems Analysis Programs for Hands-On Evaluation (SAPHIRE) Revision 8.1.6, Standardized Plant Analysis Risk (SPAR) Model, Version 8.54, for evaluating the increase in risk. The analyst performed the assessment by failing the station blackout diesel generator for an exposure period of 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> due to its assumed unavailability. The dominant core damage sequence involved a steam line break in the turbine building (SLBTB) with a failure to isolate the steam line break, a loss of reactor coolant pump (RCP) seal cooling, failure of rapid secondary depressurization, failure of the RCP seal stage 2 integrity and failure of the High Pressure Injection mitigating function. In accordance with IMC 0609, Appendix H, Containment Integrity Significance Determination Process, Figure 5.1, the increase in core damage frequency per year was below 1E-7/yr and therefore the Large Early Release Frequency (LERF) contribution was determined not to have an effect on the very low safety significance determination.Corrective Action Reference(s): CR 04093302 |
| Site: | Three Mile Island  |
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| Report | IR 05000289/2018001 Section 4OA7 |
| Date counted | Mar 31, 2018 (2018Q1) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | Licensee-identified |
| Inspection Procedure: | |
| Inspectors (proximate) | Z Hollcraft B Lin J Brand J Deboer R Rolph M Young |
| Violation of: | 10 CFR 50.63 |
| INPO aspect | |
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Finding - Three Mile Island - IR 05000289/2018001 | |||||||||||||||||||||||||||||||||||||
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Finding List (Three Mile Island) @ 2018Q1
Self-Identified List (Three Mile Island)
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