Event Notification Report for April 01, 2021

EN Revision Imported Date: 3/11/2022

EN Revision Text: PART 21 INTERIM REPORT - FAILURE OF AMETEK 300V, 250A CLAMP DIODES

The following is a synopsis of a Part 21 interim report received by email:

"COMPONENT DESCRIPTION - 300V, 250 A clamp diodes with Vishay/International Rectifier part numbers IN3737 and IN3737R and Ametek part numbers 07-600250-00 and 07-600251-00, respectively. Diode failures occurred in 20kVA Inverters, Ametek part number 85-VC0200-41 with serial numbers C84733-0211 and C84733-0511. Two failed diodes returned for evaluation were manufactured in India in 2004.

"PROBLEM EXPERIENCED - TVA has experienced 5 diode failures since November of 2017. The diode failures experienced at TVA resulted in alarms for abnormal conditions and equipment alarms for fan failure, inverter fuse blown, and inverter failure. The equipment will transfer to bypass when a diode fails.

"POTENTIAL CAUSE - Diodes installed in the TVA equipment were shorted in most cases and degraded in one instance. Only two of the shorted diodes were sent to AMETEK SCI for evaluation.

"While the precise cause of this failure is unknown, diode failures are generally attributed to transient voltage spikes and overheating. TVA did indicate there have not been any transient events on the DC bus that could have caused this failure.

"The inverters at TVA are loaded below 50%. This could contribute to increased heat and stress on the diodes due to increased current draw. However, test data from the original testing of the equipment at no load did not show elevated temperatures on the diodes.

"EFFECT ON SYSTEM PERFORMANCE - Failures described above could result in loss of output voltage and transfer of the static switch to the bypass source which could result in potential loss of load.

"EVALUATION OF THE POTENTIAL DEFECT - AMETEK is sending the parts to the original manufacturer for further evaluation with the intent to obtain more insight on the interior condition of the diodes. The targeted completion date for this evaluation of the two diodes returned is June 1, 2021."


* * * UPDATE FROM ETHAN SALSBURY TO DONALD NORWOOD AT 0648 EDT ON 4/6/2021 VIA E-MAIL* * *

What is being classified as a 'minor adjustment' is being made to the notification originally submitted on 4/1/2021.

"All diodes TVA identified as failed were shorted. None were degraded."

Notified R2DO (Miller) and the Part 21/50.55 Reactors E-mail group.

* * * UPDATE FROM ETHAN SALSBURY TO THOMAS HERRITY AT 1145 EST ON 02/11/2022 VIA EMAIL * * *

The following excepts provide a synopsis of information provided by AMETEK in the final report.

"... The failure was caused by electrical overstress, but the specific root cause is indeterminate.

"PROBLEM YOU COULD SEE: A diode failure could occur and will result in the equipment transferring to bypass, a loss of output voltage, blown fuses, and unexpected alarms such as fan failure, inverter fuse blown, and inverter failure alarms. There are no conclusive warning signs that a failure is imminent, or detection method for predicting an approaching failure.

"CAUSE: Diodes that failed in the TVA equipment were shorted according to the summaries provided by TVA. Only two of the shorted diodes were sent to AMETEK SCI for evaluation. The condition of all other diodes is unknown.

"While the precise cause of this failure is unknown, diode failures are generally attributed to transient voltage spikes and overheating. TVA did indicate there have not been any transient events on the DC bus that could have caused this failure. Additionally, AMETEK sent a representative to the site to review the equipment and operating conditions. The field service technician concluded that there were no abnormalities apparent in the operating conditions or the equipment itself.

"According to TVA, the inverters at TVA are loaded below 50%. The AMETEK field service representative determined load was at 25% of full load during the site visit in August of 2021. This could contribute to increased heat and stress on the diodes due to increased current draw. However, there was no indication of overheating of the diode at no load or 25% of unit C84733- 0511 (1-II). All diodes were within acceptable temperature conditions on the equipment evaluated.

"EFFECT ON SYSTEM PERFORMANCE: Failures described above could result in loss of output voltage and transfer of the static switch to the bypass source which could result in potential loss of load.

"ACTION REQUIRED: AMETEK Solidstate Controls recommends that each facility evaluate the potential risk and performs replacement as determined necessary. Evaluation could include oscilloscope measurements across the diodes and temperature measurements of the diodes and the equipment. Voltage readings from the oscilloscope measurement should not exceed the rating of the diode. Temperatures should be compared to original test data and should not exceed 100ø C.

"Recent evaluations have been unable to pinpoint a failure mode and there are no conclusive connections to previous failures. Only the failures provided in this report have surfaced for the subject part numbers and the failure rate has been low.

"AMETEK SOLIDSTATE CONTROLS CORRECTIVE ACTION: AMETEK Solidstate Controls will work with you to arrange replacements and spare parts for your application as needed. Please contact our Client Services group at 1-800-222-9079 or 1- 614-846-7500, extension 1."

Notified R2DO (Miller) and the Part 21/50.55 Reactors E-mail group.

EN Revision Imported Date: 4/30/2021

EN Revision Text: AGREEMENT STATE REPORT - GAUGE DAMAGED BY CONSTRUCTION VEHICLE

The following was received from the Texas Department of State Health Services (the Agency) via email:

"On April 1, 2021, at 1647 CDT, the Agency was notified by the licensee's radiation safety officer (RSO) that a Troxler model 3440 moisture density gauge containing an eight millicurie cesium-137 source and a 40 millicurie americium-241 source had been run over at a field site by a piece of equipment.

"The RSO stated the technician using the gauge stated that the cesium-137 source was in the fully shielded position when the event occurred. The RSO stated the technician was moving his equipment to a new test location at the site when the gauge was damaged. The RSO stated the gauge case was shattered and he was not sure how they would recover the gauge. He stated the gauge was reading 40 millirem per hour on contact near the cesium source. The RSO stated a barrier was establish around the gauge and the dose rate readings at the barrier were at background.

"The Agency advised the RSO to contact the manufacturer and request assistance in recovering the gauge. The RSO contacted the Agency a short time later and reported the manufacturer could not assist in the recovery. The RSO also stated that during his inspection of the gauge they discovered the cesium source was not in the fully shielded position. Also, it appeared that the source rod was no longer attached to the gauge housing. The RSO stated the source rod was bent so they could not retract the source into the shield.

"The licensee decided to recover the source by picking the source rod up from the end opposite of the source using channel locks and placing it in a thirty gallon can half full with sand and then covering the source with sand. The RSO reported the highest dose rate on the container after placing the source in the can and covering it with sand was 0.8 millirem per hour. The RSO contacted the Agency at 1828 CDT on April 1, 2021, and reported that the source was locked in their storage facility. The RSO stated they would work with the manufacturer to dispose of the gauge and sources. The RSO stated the gauge would be leak tested on April 2, 2021. The RSO stated the americium-241 source was not affected by the event. No individual received a significant exposure from the event. Additional information will be provided as it is received in accordance with SA-300."

Texas Incident Number: I-9835

EN Revision Imported Date: 5/7/2021

EN Revision Text: AGREEMENT STATE REPORT - DOSE ADMINISTERED GREATER THAN PRESCRIBED

The following was received from the Minnesota Department of Health via email:

"A medical event has occurred at Essentia Health, Duluth, MN (MN license number 1048). The event occurred on April 1, 2021 and was discovered by the radiation safety officer on April 8, 2021. The licensee reported the event to the state of Minnesota on April 8, 2021.

"Preliminary details are as follows: A Y-90 Theraspheres procedures with a prescribed dose of 140 Gy administered 173.4 Gy on April 1, 2021. This resulted in a dose [that varied by] greater than 20 percent of prescribed. The event was discovered by the radiation safety officer following a records review and reported to the state of Minnesota within 24 hours of discovery. The licensee is investigating the root cause and the potential for harm to the patient. A report will be submitted within 15 days.

"The state plans to do an on-site investigation with the licensee. Additional information will be reported following the final report from the licensee and investigation by the state."


A Medical Event may indicate potential problems in a medical facility's use of radioactive materials. It does not necessarily result in harm to the patient.

EN Revision Imported Date: 7/1/2021

EN Revision Text: 60-DAY TELEPHONIC NOTIFICATION OF INVALID ACTUATION OF A GENERAL CONTAINMENT ISOLATION SIGNAL AFFECTING MORE THAN ONE SYSTEM

"This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of the 2A Reactor Protection System (RPS). On April 1, 2021, at 1302 (CDT), Browns Ferry Unit 2, 2A RPS [Motor Generator] MG set tripped causing a half scram. Unit 2 experienced an unexpected trip of the 2A RPS MG Set that resulted in automatic Primary Containment Isolation System (PCIS) Group 2, 3, 6, and 8 isolations and Trains A, B, and C Standby Gas Treatment (SGT) and Train A Control Room Emergency Ventilation (CREV) starts. At the time of the event, Unit 2 was in a refueling outage and the rods were already fully inserted. All systems responded as expected.

"Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid.

"Based on the troubleshooting conducted, the cause was determined to be a loose wiring connection in the motor circuit. The lugs were replaced with ring lugs. Operations reset the 2A RPS Half Scram and PCIS in accordance with 2-AOI-99-1 on April 1, 2021, at 1324 CDT thus correcting the condition and returning RPS to service.

"There were no safety consequences or impact to the health and safety of the public as a result of this event.

"This event was entered into the Corrective Action Program as Condition Report 1683358.

"The NRC Resident Inspector has been notified of this event."

EN Revision Imported Date: 6/28/2021

EN Revision Text: 60-DAY TELEPHONIC NOTIFICATION OF INVALID PLANT PROTECTION SYSTEM ACTUATION SIGNAL

"This 60-day telephone notification is being made in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to provide information pertaining to an invalid Engineered Safety Feature actuation signal.

"On April 1, 2021, at Waterford 3, while performing a replacement of power supplies on the Plant Protection System, a spurious signal caused a partial actuation of the Emergency Feedwater Actuation Signal. A partial Emergency Feedwater (EFW) logic trip path was met causing the opening of valves EFW-228A (EFW to SG 1 Primary Isolation), EFW-229A (EFW to SG 1 backup isolation), EFW-228B (EFW to SG 2 Primary Isolation), and EFW-229B (EFW to SG2 Backup Isolation).

"This inadvertent actuation was spurious and was not a valid signal resulting from parameter inputs. The 1992 Statements of Consideration (57 FR 41378) define an invalid signal to include spurious signals. Therefore, this actuation is considered invalid.

"This event was entered into the Waterford 3 corrective action program for resolution. This event did not result in any adverse impact to the health and safety of the public. The plant responded as expected.

"In accordance with 10 CFR 50.73(a)(1) a telephone notification is being made in lieu of submitting a written Licensee Event Report.

"The NRC Senior Resident Inspector has been notified."