Event Notification Report for May 20, 2026

LOST MOISTURE DENSITY GAUGE

The following information was provided by the licensee via phone:

An NRC inspection of the licensee found that one of three Troxler model 3440 moisture density gauges, containing 10 mCi of Cs-137 and 40 mCi of Am-241/Be, was no longer in the licensee's possession. The licensee reported that the gauge had been sold to a company in Wisconsin approximately five years ago. No records of the sale were available. The licensee is attempting to locate additional information about the missing gauge.

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

TECHNICAL SPECIFICATION ABNORMAL OCCURRENCE

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

"On May 17, 2026, at 0457 CDT, the control room received a firemain low pressure alarm with indication reading 0 psi. The firemain provides the source of water to the emergency pool fill system as required by Technical Specification 3.9.b. At 0501 it was confirmed this was an actual firemain rupture and not just an indication. At 0502 the reactor was manually scrammed. At 0514 the ruptured firemain was discovered and isolated shortly thereafter to restore pressure. Subsequently, permission for the reactor restart was received from the facility director and the reactor was restarted at 1245.

"The 12-inch firemain was found split from fitting to fitting. The cause is still being investigated."


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

At the time of notification, the reactor was in the shutdown condition for normal planned maintenance.

MANUAL REACTOR SCRAM

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

"At approximately 1803 EDT on May 18, 2026, the operating crew responded to a fire below the main generator. The fire was identified on the Y-phase of the isophase ducts. At 1807, the reactor was manually scrammed, and a level 3 isolation signal was received due to the scram. The scram was non-complicated. The fire was confirmed extinguished at 1810.

"Operations responded and stabilized the plant. Reactor water level is being maintained at normal level. The lowest water level observed was approximately 139.5 inches. Decay heat is being removed by the main steam system to the main condenser using automatic operation of the turbine bypass valves. All control rods inserted into the core.

"Due to the reactor protection system actuation while critical, this event is being reported as a four-hour non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B)."