Potential Detonation Threat Comes From Pu Containers From SRS
WC Monitor
9/26/2014
The Department of Energy this week confirmed that a detonation threat under review at an Oak Ridge waste storage site involves containers of plutonium that were brought to Oak Ridge from Savannah River more than 30 years ago. Mike Koentop, executive officer at DOE’s Office of Environmental Management in Oak Ridge, would not say how many containers are under investigation or specify the quantity of plutonium in the containers, except to characterize it as “small amounts.” Koentop said the investigation pertains to a “small population” of drums that “has the potential to generate hydrogen and oxygen gases higher than anticipated.” Based on those characteristics, the containers were determined to “be at a slight risk for a detonation hazard,” he said. The perceived threat of detonation is reportedly based on the possible presence of moisture inside the storage containers.
The issue was first identified in May by URS-CH2M Oak Ridge (UCOR), the DOE environmental cleanup manager in Oak Ridge. The contractor, based on some new information, cited a “potential inadequacy” in the safety analysis for the containers stored at the Melton Valley Solid Waste Storage Facility. The storage facility is located on the back side of Oak Ridge National Laboratory not far from the Molten Salt Reactor and other nuclear facilities. Koentop indicated that security restrictions prevented him from providing more details about the containers of plutonium.
Drums ‘Safely and Securely Stored,’ DOE Says
After the initial findings cited in May, an analysis of data was able to rule out hazards for nearly half of the containers cited as potentially vulnerable to a buildup of gases and detonation. Some other drums of possible concern were added to the review based on the broadening investigation. “Calculations involving the remaining containers are still being analyzed, and those drums remain safely and securely stored,” Koentop said in response to questions.
A July 25 memo by staff members of the Defense Nuclear Facilities Safety Board noted that DOE had approved an evaluation “of the safety of the situation.” The evaluation was prepared by UCOR. According to the safety board memo, the contractor 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.” While approving the evaluation, DOE also “considered the fact that the affected containers have a long history of safe storage,” the memo noted.
Material Sent to Oak Ridge in The 1980s
Koentop said the plutonium was generated during operations at the Savannah River Site in South Carolina during the 1970s. The containers were sent to Oak Ridge National Laboratory in the 1980s for repackaging and long-term storage, he said. Each of the drums has multiple layers of containment—a series of containers inside the main 55-gallon drum—apparently for safety reasons. The small amount of plutonium oxide and/or metal is located inside a “pipe nipple” in the interior of the storage drum. Koentop said plutonium was originally packaged at Savannah River in a “dry environment” in the 1970s. There are some questions, however, about the conditions under which the material was repackaged at ORNL in the 1980s, he said.
Even if the gases were to cause a detonation, Koentop said, the plutonium would not necessarily be released or dispersed, Koentop said. It’s possible that an explosion could occur and that the materials would be contained by the multiple layers of protection inside the drum, he said. The DOE official said detonation risk is low. But, he added, “You have to assume worst case.”
Plutonium is a highly toxic radioactive element that’s of great concern if particles are inhaled or ingested. It was not clear what isotopes of plutonium are contained in the Oak Ridge drums. 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. After the detonation risks have been studied and mitigated as needed, DOE contractors would open the containers at DOE’s Transuranic Waste Processing Center in Oak Ridge and repackage the plutonium for eventual disposal at the Waste Isolation Pilot Plant in New Mexico.