The issue involved the removal of a source range monitor from the reactor core on April 22, as the plant was shut down for a refueling outage.
The Perry nuclear power plant‘s managers did just about everything wrong when they sent four workers into a small room under the reactor to retrieve a radiation monitor stuck in the reactor’s core, federal regulators said in a report in July.
While performing the activities to remove the monitor, workers at the plant identified an increase in radiation levels in their work area.
Four workers stopped and immediately left the containment area when the higher than expected levels were identified.
The workers, who were exposed to high levels of radiation in the April incident, were given the wrong work instructions for the job, the Nuclear Regulatory Commission said. They used equipment that did not meet industry standards and worked in an area with wires, cables and railings that could have gotten in the way of a quick escape that also involved climbing up a ladder, the NRC said.
The Perry Nuclear Power Plant is located on a 1,100-acre (450 ha) site on Lake Erie, 40 miles (65 km) northeast of Cleveland in North Perry, Ohio, USA. The nuclear power plant is owned by First Energy Nuclear Operating Corporation.
Perry was the 100th power reactor licensed in the United States.
The reactor is a General Electric BWR-6 boiling water reactor design, with a Mark III containment design. The original core power level of 3,579 megawatts thermal was increased to 3,758 megawatts thermal in 2000, making Perry one of the largest BWRs in the United States.
The plant along Lake Erie violated several safety regulations and failed to provide sufficient instructions to the workers, leading to low to moderate safety concerns, the U.S. Nuclear Regulatory Commission said Friday.
The plant’s staff didn’t do enough to protect the contractors from being exposed to higher levels of radiation than are normal, said Mark Satorius, an NRC official who oversees plants in the Great Lakes area.
The four workers were exposed to radiation on April 22 while they were trying to remove a monitor for measuring nuclear reactions. They had been brought in to help the plant shut down to refuel and were in a containment building underneath the reactor.
The engineering team at Perry nuclear power plant Wednesday was still trying to figure out what caused a failure in an emergency shutdown system in early May.
Perry’s reactor operators manually powered down the reactor late on a Tuesday night after pressure dropped in key safety equipment designed to “scram” the reactor in an emergency, shutting it down in three seconds or less.
By noon the next day, the reactor temperature was less than 200 degrees, compared to a normal temperature of 500 degrees, and troubleshooting was under way.
“There was an open, unbarricaded, unguarded hole in the grating [floor] that was a nominal 6 foot deep and 36 inches long by 34 inches wide,” the report said, adding that several trip hazards also were present at the work site.
The NRC, which sent a team of inspectors to Perry after the incident, said the workers were within two seconds to two minutes of a radiation overdose, depending on how far away they were from the stuck radioactive cable.
Three of the four workers involved in the incident were contractors.
The NRC inspection team argued instead that the workers were just lucky and that the concern is whether the company provided adequate controls to ensure that its workers were protected from radiation overdoses.
The nuclear plant, about 30 miles northeast of Cleveland, had several safety problems several years ago, which led the NRC to monitor its safety operations every three months in 2005, when the plant was forced to shut down briefly because of problems with pumps that circulate coolant through the reactor’s core four contractors were exposed to radiation last spring.
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