Plutonium-244 is a highly valuable nuclear material used in applications such as nuclear forensics and medical research.
Office of Environmental Management
March 26, 2019
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AIKEN, S.C. – Plutonium-244 is a highly valuable nuclear material used in applications such as nuclear forensics and medical research.
And it is extremely rare.
The material is thought to exist in nature in almost undetectable quantities as a relic of the violent galactic activity that contributed to the formation of our solar system over 4.6 billion years ago. It has a half-life of 81 million years.
The only plutonium-244 that originated through human activity, other than that dispersed from nuclear weapon explosions, was produced in the unique high flux reactors, now decommissioned, that operated at the Savannah River Site (SRS) during the Cold War.
Only 20 grams of this material exists in only one place: the Mark-18A “targets,” or nuclear material assemblies, stored at SRS. In 2011, DOE asked the Savannah River National Laboratory (SRNL) to preserve the valuable, rare, and irreplaceable plutonium-244.
Recovering the materials from the Mark-18A targets is no easy task. They are mixed together in each assembly and must be chemically separated before they can be used.
H Canyon at SRS is the only operating, production-scale, radiologically-shielded chemical separations facility in the U.S. However, the facility is designed to handle large quantities of nuclear materials, so recovering the relatively small quantity of Mark-18A target material there is impractical.
SRNL decided to process the targets in a special facility at SRNL that contains cells providing shielding and confinement necessary to work with radioactive materials. A specially trained operator stands safely outside each cell to perform tasks remotely inside the shielded workspace.
The laboratory invented equipment to enable processing of the 14-foot-long Mark-18A target bundles inside the 6-by-6-foot workspaces of the SRNL shielded cells.
One is a shielded cask that will safely package, transport, and deliver a target from wet storage in L-Basin into a shielded cell. It was received at SRS in July.
Another is a cell insert that will seal the open cell; align the target as it is inserted into the cell from the transport cask so a saw can slice pieces to be processed in the limited workspace of the cell; and provide shielding during operations in the cell.
SRNL also has adapted a commercial robot typically used in the automotive industry to remotely remove material from the shielded cell and place it in a shielded container for transport. The robot arrived at the site in August 2018.
Those procurements allow for design verification of interfacing equipment, development of procedures, and personnel training necessary to prepare for an expeditious start of recovery operations. Recovery of material from the first Mark-18A target is scheduled to begin in mid-2021.