Semantic search
| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 56888 | 11 December 2023 18:32:00 | 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | Part 21 - Circuit Breaker Defects | The following information is a synopsis of information provided by the licensee via phone and email: On December 11, 2023, Tennessee Valley Authority Sequoyah Nuclear Plant completed an internal 10 CFR Part 21 evaluation concerning Siemens 6.9kV, 1200A vacuum circuit breakers, Model No. 7-HKR-50-1200-130. Three separate breakers were found with issues including loose wires terminated incorrectly and the mechanism-operated control switch clevis pin missing a cotter key. Additionally, the mastic insulating pads were found defective on all three lower primaries by way of separation. The affected breakers were never installed in a safety related application. The NRC Resident Inspector will be notified. A written notification will be provided within 30 days. The manufacturer, Siemens, was notified of the defects. The only plant known to be affected at the time of the report is the Sequoyah Nuclear Plant. | ||
| ENS 56322 | 23 May 2022 05:00:00 | 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | Part 21 - Medium Voltage Circuit Breakers | The following information is a synopsis of information provided by the licensee via fax and phone: On May 23, 2022, Framatome informed Tennessee Valley Authority (TVA) of a deviation of breakers purchased under contract. On January 23, 2023, TVA determined that a defect of the basic component could create a substantial safety hazard. Framatome Inc. identified a deviation in the Siemens medium voltage vacuum circuit breaker where a failure to electrically charge or electrically close could occur. Framatome Inc. identified this as a departure from the technical requirements included in the procurement document. It is noted that the ability to electrically trip the circuit breaker would not be affected by the condition. TVA was notified by Framatome under 10 CFR 21.21(b) to evaluate the application of the breaker for a substantial safety hazard. The TVA evaluation identified these breakers as intended for use in safety related Class 1E applications where a loss of the closure function would impact mitigation of design basis accidents and transients. During the Framatome dedication testing/inspection of Siemens medium voltage vacuum breakers, a hi-pot test failure on one circuit breaker was encountered. Troubleshooting and inspection found damage to charging motor wiring. It was determined that the cause of the damage was due to the manner in which control wiring was routed and connected to the internal bracket in close proximity to a bracket edge. This edge caused damage to wiring after significant number of cycles were applied to the breaker prior to dedication testing. TVA received nine medium voltage vacuum circuit breakers at an offsite warehouse facility. While located at that facility, TVA, with assistance from Framatome, examined the affected breakers for the wire routing condition. The wiring harnesses of certain breakers were corrected. Framatome is to examine medium voltage vacuum circuit breakers that may be purchased under this contract for the wiring condition and correct as necessary before delivery. The NRC Senior Resident Inspector has been notified. This is a non-emergency notification required by 10 CFR 21.21(d)(3)(i).
The following information is a synopsis of information provided by the licensee via phone: The Sequoyah site licensing manager requested via phone call to the HOO that the model number for the basic component with the defect be listed in the Part 21 event narrative in addition to the official Part 21 report. The component discussed is a Siemens 6.9kV, 1200A, 125VDC Vacuum Circuit Breaker, Model No.: 7-HKR-50-1200-130. Notified R2DO (Miller) and the Part 21 Reactors Group (Email). |