05000289/LER-2015-001
| Three Mile Island, Unit 1 | |
| Event date: | 08-06-2015 |
|---|---|
| Report date: | 10-05-2015 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2892015001R00 - NRC Website | |
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2. DOCKET
A. EVENT DESCRIPTION
Plant Conditions before the event:
Babcock & Wilcox — Pressurized Water Reactor — 2568 MWth Core Power Date/Time: August 6, 2015 / 14:30 hours Power Level: 100% Mode: Power Operation TMI Unit 1 (TMI-1) had recirculated and cleaned up the BWST since original plant operation (operating license issued April 19, 1974). On January 26, 2012 the NRC issued Information Notice IN 2012-01 "Seismic Considerations-Principally Involving Tanks". IN 2012-01 discussed the Shearon Harris plant's recirculation of a seismically qualified RWST (refueling water storage tank) through non-seismic fuel pool piping purification system piping causing the RWST to be made inoperable. TMI-1 reviewed the IN 2012- 01 and stopped the practice of BWST recirculation on October 3, 2012 to conduct a further investigation of the licensing basis. The procedure for BWST recirculation and clean-up was revised with a supporting 10 CFR 50.59 screening review that supported use of the BWST clean-up system. The BWST was subsequently recirculated via the clean-up system (while in power operation mode) on June 1, 2013, and later secured from the clean-up system on June 11, 2013. TMI-1 periodically used the BWST clean-up system until the NRC Resident Inspectors communicated their concerns on March 10, 2014. At that time TMI-1 ceased use of the BWST clean-up system while at power operation until the issue was resolved.
TMI-1 was cited a traditional violation for failure to perform a 10 CFR 50.59 Evaluation for the BWST Seismic Qualifications on May 14, 2014 via NRC Inspection Report 5000289/2014002. On August 6, 2015, NRC provided the final response to Task Interface Agreement (TIA) 2015-01 "Assessment of Three Mile Island Nuclear Station's Use of a Non-Seismic Qualified Cleanup Path for the Borated Water Storage Tank." A review of TIA 2015-01 coupled with a review of operator logs determined that a condition prohibited by Technical Specifications existed and is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B).
B. CAUSE OF EVENT
The apparent cause was historical interpretation of the TMI-1 licensing basis. TMI-1 staff interpreted the original plant licensing basis as a pre-GDC plant (designed prior to published Appendix A to 10 CFR 50 General Design Criteria) to not include an ECCS performance requirement coincident with a seismic event. The seismic capability for pre-GDC 2 plants was subsequently questioned and the USI A-46 process established to resolve the issue. TMI-1 interpreted the USI A-46 resolution and original FSAR description of the BWST recirculation process path as an acceptable basis for operation.
When TIA 2015-01 was published on August 6, 2015, final resolution of this issue was concluded:
"Based on a review of TMI's licensing basis (i.e., the draft GDC and design bases in the UFSAR), the NRR staff has concluded that the BWST cannot be credited to perform its intended safety function when it is connected to the non-seismically qualified piping for cleanup. This configuration is unanalyzed and renders the BWST inoperable according to TS. Also, manual actions are not approved as a justification for compliance with Criterion 2 of the AEC draft GDC.
C. ANALYSIS / SAFETY SIGNIFICANCE
This event had no effect on the health and safety of the public. There were no actual safety consequences for the condition because there were no seismic events that impacted the non-seismic BWST clean-up and recirculation piping.
A technical evaluation was completed for the non-seismic BWST Cleanup and Recirculation piping.
The technical evaluation concluded that the piping used for cleanup or recirculation of the BWST will withstand a safe shutdown earthquake (SSE) without loss of pressure boundary integrity. The additional defense-in-depth measure during an SSE or Operating Basis Earthquake (OBE) seismic event was provided by the timely removal of the BWST from Cleanup or Recirculation operation by implementing emergency operating procedure OP-TM-AOP-003 "Earthquake." Therefore, had an event occurred, the actions implemented in emergency operating procedure OP-TM-AOP-003 "Earthquake" would have provided additional defense-in-depth.
D. CORRECTIVE ACTIONS
- Implemented administrative controls to prohibit aligning the BWST to the non-seismic qualified clean-up piping in modes power operations, Startup, Hot Standby and Hot Shutdown
- A license amendment request was submitted on July 23, 2015 to provide Temporary Restoration of Borated Water Storage Tank Cleanup and Recirculation Operation until permanent resolution is implemented
- Various options that include permanent plant modifications are being evaluated
E. PREVIOUS OCCURENCES
Previous Events Previous Event Review None * Energy Industry Identification System (EIIS), System Identification (SI) and Component Function Identification (CFI) Codes are included in brackets, [SI/CFI] where applicable, as required by 10 CFR 50.73 (b)(2)(ii)(F).