30 March 2012
$20M plutonium project at ORNL to support space program
By Frank Munger
Knox News Sentinel

OAK RIDGE — Over the next two years, Oak Ridge National Laboratory will carry out a $20 million pilot project to demonstrate the lab's ability to produce and process plutonium-238 for use in the space program.

Tim Powers, director of ORNL's Non-Reactor Nuclear Facilities Division, said the technology demonstration will include development of neptunium-237 targets that will then be introduced into the High Flux Isotope Reactor to produce small amounts of Pu-238. Later, workers will remove the targets from the reactor core and process the radioactive materials in hot cells at the lab's Radiochemical Engineering Development Center, separating the Pu-238 from the neptunium and purifying the plutonium.

Powers said the ORNL program will support the U.S. Department of Energy's plan to eventually produce 1½ to 2 kilograms of Pu-238 per year, using existing infrastructure within the DOE complex. For years, the U.S. has relied on purchases from Russia to supplement the inventory of the radioisotope for the space power program. There have been multiple proposals to re-establish a U.S.-based production program, none of which took hold.

According to Powers, very small amounts of neptunium will be introduced into the High Flux Isotope Reactor in the early stages of the demonstration project. Over time, some of the targets will be withdrawn for evaluation, while others will be left in the reactor core for longer irradiation periods, he said.

Pu-238 is a sister isotope to the plutonium-239 that's used in nuclear weapons. It's considered the optimum material for power sources — known as radioisotope thermoelectric generators or RTGs — on deep space missions.

The RTGs supply electricity to spacecraft that are too far from the sun to use solar panels. The heat generated by plutonium's natural decay is converted to electricity, which then powers transmitters and other instruments.

In addition to using the lab's 85-megawatt research reactor and the nearby Radiochemical Engineering Development Center, ORNL plans to do some of the nuclear processing work for the project at Building 3535 — also known as the Irradiated Fuels Examination Lab.

Powers said NASA is providing funds for the project. The research money is funneled through the U.S. Department of Energy's Nuclear Energy program to the Oak Ridge lab.

ORNL is just one of the institutions participating in the program. The Advanced Test Reactor at Idaho National Laboratory also will be producing Pu-238, and Powers said Oak Ridge would provide information on target development, production evaluation and flow sheet on its processing work to Idaho.

DOE will eventually make a decision on where best to do the plutonium work following the various pilot projects. "We think we're the best choice," Powers said.