Some items from today’s NRC Event Reports:
1. Sometimes safety systems can be overcome by human error. Early yesterday morning, a technician left two doors open in the Unit 2 reactor building at the Dresden nuclear power plant in Illinois. This negated an engineered safety feature and might have allowed an unsafe condition in some accident scenarios. The doors had an interlock system designed to prevent the simultaneous opening of both doors, but the lock system was ungoing maintenance testing at the time of the incident.
2. Also yesterday, operators at the Monticello nuclear plant in Minnesota were performing a specification review of the backup meteorological tower (MET.) They determined that the computer program software for the backup system was not properly set to record average wind direction in all instances. According to the Event Report: “A review and analysis of the historical data revealed that there were times that this condition existed when the site’s primary MET had been out-of-service for maintenance or equipment issues. During those times the backup MET was relied on for determination of wind direction. Analysis determined that during those times the potential existed to incorrectly report affected sectors for Protective Action Recommendations.”
3. On Tuesday, the River Bend nuclear power plant in Louisiana reported “detectable levels of tritium” in an onsite groundwater wells. The well registered a level of 48,000 picocuries per liter, more than twice the EPA-established threshold for drinking water. The well is not used for drinking water.
4. Vermont Yankee reported yesterday that they had been informed by an offsite testing laboratory that a water sample they had submitted “tested positive for a low level of tritium.” The sample was taken from the Connecticut River adjacent to the plant.
5. The turbine building at the Clinton nuclear power plant in Illinois had to be evacuated yesterday evening after high hydrogen levels were detected. Clinton nuclear declared an Unusual Event and notified the NRC. The turbine building roof vents were opened, and the emergency was declared over after about 45 minutes.