A barrel of radioactively contaminated material at a Westinghouse Electric facility in Columbia, S.C., briefly ignited early on July 12 after becoming pressurized and popping off its lid, the U.S. Nuclear Regulatory Commission reported.
The drum had just been placed into storage after being loaded with mop heads, filters, and rags designated as “wet recoverable material,” along with laboratory waste, according to an NRC event notification report posted Monday. The material was generated by the Columbia facility’s core uranium fuel fabrication mission, the agency said.
An “unexpected chemical reaction caused the barrel to pressurize and the lid blew off” at 1:52 a.m., NRC spokesman Joey Ledford said Monday. Acid in the barrel might have reacted with other materials, he said, noting that the agency is continuing to review the incident.
Some material in the barrel was ejected, the NRC report says. There was a small fire involving dry paper in the vessel, which caused a smoke detector to activate.
Firefighting personnel tipped the barrel over and dispersed the contents, Ledford said: The fire “pretty much extinguished itself.”
In the event report, the NRC said workers moved the drum away from other material in storage. “There were no personnel injuries. Health Physics monitored the area with no airborne results approaching radiological limits and no personnel were affected,” the agency said.
“The materials had been packaged for uranium recovery and incineration. The fire was quickly extinguished by plant personnel, with no impact on people, the environment or the plant,” Westinghouse said in a prepared statement Monday. “The safety of our employees and community is our highest priority. Air samples taken within the area confirmed no impact to plant personnel, the public or the environment.”
The company said it would conduct a comprehensive evaluation of the incident. An NRC inspector is also expected to visit the facility next week to follow up.
“Westinghouse has yet to complete their investigation of the incident. We will be analyzing their findings as well as the corrective actions they have identified and are putting into place to ensure there is no recurrence,” Ledford stated by email on Thursday. “When we go in next Thursday, we will begin this work, as well as looking through the waste from the drum, examine the drum itself, question the workers who were involved — all the things you would expect. That’s just part of the beginning of the process.”
Measurements prior to storing the drum showed the material had a uranium-235 content of 71.45 grams, which is within the reporting threshold. The material in the drum is considered recoverable, containing a sufficient amount of uranium for reprocessing, Ledford said. Westinghouse typically sends the drums to an incinerator, “where the material is burned, the uranium is recovered, and the waste ash is then processed as waste.”
Wet-loading was temporarily suspended after the incident, but had resumed by Wednesday after Westinghouse took several corrective steps, Ledford stated. That included updating operating procedures and additional training for personnel. The company is also now using a different type of waste drum lid that ventilates itself to prevent pressurization. Westinghouse added that its steps would include revised segregation controls to prevent mixing of potentially combustible materials and revised monitoring of heat buildup.
The 550,000-square-foot Columbia Fuel Fabrication Facility began operations in 1969, producing nuclear fuel for power plants.
The NRC in 2016 investigated the buildup of uranium-contaminated material in the scrubber for the plant’s ventilation system, which it said could have represented a danger of criticality – an uncontrolled nuclear fission chain reaction.
Multiple leaks have also been found at different times in the facility, The State newspaper reported.
