ML21174A094

Reactor Trip on June 7, 2021 - Management Directive 8.3 Screening

ML21174A094
Person / Time
Site:	Comanche Peak
Issue date:	06/23/2021
From:	O'Keefe N NRC/RGN-IV/DRP
To:	Anton Vegel NRC/RGN-IV/DRP
References
MD 8.3, NRC-2021-000233
Download: ML21174A094 (4)

Text

June 23, 2021 MEMORANDUM TO: Anton Vegel, Director Division of Reactor Projects FROM: Neil OKeefe, Chief Projects Branch B Cornelius Digitally signed by Cornelius F. O'Keefe Division of Reactor Projects F. O'Keefe Date: 2021.06.23 17:19:50 -05'00'

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT UNIT 2 REACTOR TRIP ON JUNE 7, 2021 - MANAGEMENT DIRECTIVE 8.3 SCREENING On June 7, 2021, Comanche Peak Nuclear Power Plant Unit 2 experienced a failure and fire in main transformer 2MT1 which caused the main generator to lock-out relays on phase differential. The generator lockout tripped the main turbine which caused an automatic reactor trip from full power. As expected, the auxiliary feedwater system automatically started. The transformer deluge suppression system automatically actuated, and the fire brigade responded, putting the fire out in approximately 20 minutes. A local fire company arrived on site but was not needed.

Operators stabilized the plant at normal operating temperature and pressure. The resident inspector responded to the site and verified that the trip was uncomplicated, all safety systems responded as required, and that the fire was out. The resident inspector reviewed the stations actions in response to the reactor trip, the cause of the reactor trip and the sequence of events, as well as emergency action level requirements.

Over the subsequent week, the licensee determined that the Phase B main bushing on top of the transformer had experienced a failure which caused the insulator stack to shatter, hurtling shards as far as the circulating water intake structure. Damage was limited to 2MT1 components, and there were no injuries. Thorough testing demonstrated that 2MT1 and the sister transformer 2MT2 were substantially undamaged except for the 2MT1 bushing assemblies, which were replaced.

Consistent with the guidance in Management Directive 8.3, Manual Chapter 0309, Reactive Inspection Decision Basis for Reactors, and Regional Office Policy Guide 0801, Documenting Management Directive 8.3 Reactive Team Inspection Decisions, the Branch B staff screened the circumstances of this reactor trip against the deterministic criteria in Manual Chapter 0309, Enclosures 1 and 2, to evaluate whether a full deterministic and/or risk-based Management Directive 8.3 evaluation was warranted (see enclosure to this memo).

CONTACT: Neil OKeefe, DRP/B 817-200-1141

A. Vegel 2 Based on the information known as of the date of this memo, none of the deterministic criteria in either enclosure was answered in the affirmative. Thus, no reactive inspection is recommended. The resident inspectors intend to continue the review of the reactor trip as part of the baseline inspection activities utilizing Inspection Procedure 71153, Follow-up of Events and Notices of Enforcement Discretion, and other baseline inspection procedures, as appropriate.

Docket No. 05000446 License No. NPF-89

Enclosure:

As stated

ML21174A094 SUNSI Review ADAMS Non- Publicly Available Keyword:

By: NFO Yes No Sensitive Non-Publicly Available NRR-123 Sensitive OFFICE SPE:DRP/B SRI:DR C:DRP/B P/B NAME NDay JEllego NOKeefe od SIGNATURE NHD JE nfo DATE 06/23/21 6/23/21 6/23/21

Enclosure:

Screening of Management Directive 8.3 Deterministic Criteria for:

Comanche Peak Reactor Trip on June 7, 2021 IMC 0309, Enclosure 1 Deterministic and Risk Criteria: Yes/No; Remarks Involved operations that exceeded, or were not included in, the design No bases of the facility Involved a major deficiency in design, construction, or operation having No potential generic safety implications Led to a significant loss of integrity of the fuel, primary coolant pressure No boundary, or primary containment boundary of a nuclear reactor Led to the loss of a safety function or multiple failures in systems used No to mitigate an actual event Involved possible adverse generic implications No Involved significant unexpected system interactions No Involved repetitive failures or events involving safety-related equipment No or deficiencies in operations Involved questions or concerns pertaining to licensee operational No performance Remarks: None of the deterministic criteria were met for this event.

This was an uncomplicated plant trip and all equipment responded as expected. Operator and fire brigade response was appropriate.

IMC 0309, Enclosure 2 Deterministic-only Criteria:

None of the Reactor Safety, Radiation Safety, and Security/Safeguards deterministic criteria questions were answered in the affirmative for this event.

Enclosure