Event Notification Report for August 30, 2024

AGREEMENT STATE - STOLEN MOISTURE DENSITY GAUGES

The following information was provided by the California Radiologic Health Branch via email:

"The RSO and Vice President of NMG Geotechnical, Inc. notified the California Radiologic Health Branch that two moisture density gauges had been stolen over the weekend (August 30 - Sept 2, 2024) from a locked trailer at their jobsite. Other construction equipment was also stolen. Thieves removed security bars from a window to enter and exit the trailer. The two gauges were secured within separate locked cabinets inside the trailer, inside their locked transportation cases that has company name and contact number affixed.

"The Troxler model 3411, number 12325 contains 8 millicurie of Cs-137 and 40 millicurie of Am-241/Be sealed sources. The CPN MC-3 Elite contains 10 millicurie of Cs-137 and 50 millicurie of Am-241/Be sealed sources. A trigger lock on the CPN gauge was not engaged and the Troxler did not have a trigger padlock.

"Irvine Police Department was notified of the theft. Maurer Technical Services was also notified. NMG Geotechnical will post a reward for information leading to the return of the stolen equipment."

California 5010 Number: 090324

THIS MATERIAL EVENT CONTAINS A 'Less than Cat 3' LEVEL OF RADIOACTIVE MATERIAL

Sources that are "Less than IAEA Category 3 sources," are either sources that are very unlikely to cause permanent injury to individuals or contain a very small amount of radioactive material that would not cause any permanent injury. Some of these sources, such as moisture density gauges or thickness gauges that are Category 4, the amount of unshielded radioactive material, if not safely managed or securely protected, could possibly - although it is unlikely - temporarily injure someone who handled it or were otherwise in contact with it, or who were close to it for a period of many weeks. For additional information go to http://www-pub.iaea.org/MTCD/publications/PDF/Pub1227_web.pdf

SPECIFIED SYSTEM ACTUATION - AUTOMATIC START OF DIESEL GENERATORS

The following information was provided by the licensee via phone and email:

"At 1051 CDT on 8/30/2024, during transfer of 4KV shutdown bus 1 to support Unit 1 shutdown activities, the alternate feeder breaker failed to close resulting in 4KV shutdown boards 'A' and 'B' experiencing an under voltage condition. This resulted in 'A' and 'B' diesel generators automatically starting and tying to their respective boards. This condition also caused a loss of reactor protection system (RPS) channel 'A' on Units 1 and 2, resulting in invalid actuation of primary containment isolation system Groups 2, 3, 6, and 8. The failure of the board to transfer was identified during preparation for the evolution, contingency actions were prepared and implemented as planned. The breaker failure to close has been corrected and 4KV shutdown bus 1 is energized on alternate. 4KV shutdown boards 'A' and 'B' have been restored to offsite power supplies and the diesel generators are secured.

"All systems responded as expected for the loss of voltage. This event requires an 8-hour report per 10 CFR 50.72(b)(3)(iv)(A). There was no impact to the health and safety of the public or plant personnel. The NRC resident has been notified."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

The change in reactor power from 70 percent to 40 percent was not as a result of the failed breaker, rather Browns Ferry Unit 1's change in reactor power was due to a scheduled reactor shutdown which was in progress. In regards to the Unit 2 loss of channel 'A' RPS, this was not a specified system actuation. The actuation of the 'A' and 'B' diesel generators were the specified system actuation. Although the 'A' and 'B' diesels are common to both Units 1 and 2, only Unit 1 credits these specific diesel generators for accident mitigation. As such, this event is only reportable from Unit 1. Unit 2 did not experience a specified system actuation.

AGREEMENT STATE REPORT - RADIOGRAPHY CAMERA FAILURE

The following report was received via email from the California Radiologic Health Branch (RHB),

"The Mistras Group's radiography crew was working at a temporary job site (inside a tank) on Friday, August 30, 2024. During the first exposure for the day at 0845 [PDT], the radiographer extended the source assembly and then felt the crank mechanism spin freely, causing the inability to retract the source assembly into the shielded position (a critical component failure). Emergency procedures were implemented; both radiographers extended their controlled radiation area boundary and monitored the area while the radiation safety officer (RSO) was notified at 0852. Source recovery personnel from Mistras Group's Torrance Lab arrived at 1040 to evaluate the situation. A recovery plan was discussed and implemented by the recovery radiographer. He entered the tank, opened the crank assembly, and determined the drive cable was not inside the housing. He opened the exposure side of the crank assembly and saw the end of the drive cable. He was able to retract the source assembly drive cable until the source assembly latched and locked inside the exposure device. This was accomplished at 1105. The RSO made a telephone notification to RHB at 1801 to report the event, but it went to voice mail, so he left his name and phone number. However, the voice mail was not forwarded and the RSO did not follow-up the next week to determine if his voice mail was received. A 30-day written notification of the event, per 10 CFR 34.101 was sent to RHB and received on September 28, 2024. Radiation exposures did not exceed 5 mrem for any involved personnel."

California Report Number: 093024