ENS Event | |
|---|---|
22:17 Mar 8, 2026 | |
| Title | Degraded Reactor Vessel Closure Head Penetration |
| Event Description | The following information was provided by the licensee via phone and email:
At 1717 CDT on March 8, 2026, during the Byron Unit 1 refueling outage, it was determined that the control rod drive mechanism (CRDM) penetration 31 was degraded because liquid penetrant testing performed on the embedded flaw repair weld identified an unacceptable rounded indication, in accordance with American Society of Mechanical Engineers (ASME)Section III acceptance standards and an NRC-approved licensee relief request for a previously performed embedded flaw repair. Required repairs will be completed in accordance with the ASME code of record prior to returning the vessel head to service. Therefore, this event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| Where | |
|---|---|
Byron  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | |
| Time - Person (Reporting Time:+2.97 h0.124 days <br />0.0177 weeks <br />0.00407 months <br />) | |
| Opened: | Jacob Benner 01:15 Mar 9, 2026 |
| NRC Officer: | Brian P. Smith |
| Last Updated: | Mar 9, 2026 |
| 58186 - NRC Website
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WEEKMONTHYEARENS 581862026-03-08T22:17:0008 March 2026 22:17:00
[Table view]10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Degraded Reactor Vessel Closure Head Penetration ENS 573212024-09-13T13:23:00013 September 2024 13:23:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Degraded Reactor Vessel Closure Head Penetration ENS 558572022-04-23T13:54:00023 April 2022 13:54:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Ultrasonic Examination Results - Reactor Vessel Head Penetration ENS 525922017-03-05T14:00:0005 March 2017 14:00:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Planned Ultrasonic Test on Previously Repaired Reactor Vessel Penetration Did Not Meet Acceptance Criteria ENS 525912017-03-03T23:05:0003 March 2017 23:05:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Previous Overlay Repair Did Not Meet Acceptance Criteria ENS 514102015-09-19T01:00:00019 September 2015 01:00:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Reactor Vessel Head Penetration Repair Did Not Meet Acceptance Criteria ENS 505172014-10-08T00:00:0008 October 2014 00:00:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Ultrasonic Testing Reveal Degraded Condition on One Control Rod Drive Mechanism Penetration ENS 483112012-09-15T00:00:00015 September 2012 00:00:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Degraded Condition Due to Indications on Reactor Vessel Head During Dye Penetrant Test ENS 466862011-03-19T13:00:00019 March 2011 13:00:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Ultrasonic Examination Results in Indications on Two Reactor Head Penetrations 2026-03-08T22:17:00 | |