Mike Koentop, executive officer at DOE’s Office of Environmental Management in Oak Ridge, confirmed this week that a “small population” of drums “has the potential to generate hydrogen and oxygen gases higher than anticipated.” He added: “Based on these characteristics, the containers were determined to be at slight risk for a detonation hazard.”
According to Koentop, the plutonium was generated during operations at the Savannah River Site in South Carolina during the 1970s, and the containers were sent to Oak Ridge National Laboratory in the 1980s for repackaging and long-term storage.
Each of the drums has multiple tiers of containment, apparently for safety and security reasons. The small amount of plutonium oxide and/or metal is inside the inner-most component known as a “pipe nipple.”
Koentop would not reveal the quantities of plutonium involved, but he described them as “small amounts.”
The potential threat was first recognized in May by URS-CH2M Oak Ridge (UCOR), the federal agency’s environmental manager in Oak Ridge. Based on new information, the contractor reportedly declared a “potential inadequacy” in the safety analysis for the containers stored at the Melton Valley Solid Waste Storage Facility on the southern outskirts of Oak Ridge National Laboratory.
Koentop declined to specify the number of plutonium-bearing drums initially identified as a concern, apparently because of security restrictions. But he said additional data and analyses determined that almost half of the original number did not pose a detonation threat. Some other drums were subsequently added to the lot and evaluated for possible concerns.
“Calculations involving the remaining containers are still being analyzed, and those drums remain safely and securely stored,” the DOE official stated via email.
A recently released July 25 memo by staff members of the Defense Nuclear Facilities Safety Board said that DOE had approved an evaluation “of the safety of the situation” that was prepared by its Oak Ridge contractor.
The evaluation “identifies interim safety measures implemented through a standing order that prohibits contact, movement or handling of the specific containers stored at the Melton Valley Solid Waste Storage Facilities,” the memo stated. “As part of its basis for approval, (DOE) also considered the fact that the affected containers have a long history of safe storage.”
The detonation hazard is apparently based on the possible presence of moisture inside the storage containers.
Koentop said it is known that the plutonium was originally packaged at Savannah River in a carefully controlled “dry environment.” There are some questions, however, about the conditions under which the high-hazard radioactive material was repackaged at ORNL in the 1980s, he said.
The DOE official said Thursday that even if there was an explosion or detonation caused by a build-up of gases, it doesn’t necessarily mean that the radioactive material would be dispersed. It’s conceivable that a detonation could occur and it would still be contained by the multiple layers of protection inside the 55-gallon drum, he said.
He emphasized that the risk of detonation is believed to be slight, but added, “You have to assume worst case.”
Plutonium is a highly toxic radioactive element that poses a particular hazard if particles are inhaled or ingested. DOE did not immediately confirm which isotope or isotopes of plutonium were housed in the Oak Ridge storage containers. Plutonium-239 is the fissile isotope that’s used in nuclear weapons. Other forms include Pu-238, which can be used as a heat source in so-called RTGs (radioisotope thermoelectric generators) to provide power on space missions.
Once the detonation risk has been fully evaluated and — if necessary — mitigated, the plan is to open the containers and repackage the radioactive materials at DOE’s Transuranic Waste Processing Center in Oak Ridge.
Ultimately, the plutonium wastes will be shipped to the Waste Isolation Pilot Plant in New Mexico for permanent disposal.
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