The US Department of Energy’s (DOE’s) Office of Environmental Management announced on its website that workers for the first time have removed equipment contaminated with plutonium once used to power deep space missions from building 235-F at the Savannah River Site (SRS) facility, marking a milestone in reducing risk.
The two-story, blast-resistant, windowless, reinforced concrete 235-F facility has been inactive for more than 25 years. One section of the building – the Plutonium Fuel Form (PuFF) Facility – was used to make fuel spheres and pellets out of plutonium-238. These pellets powered deep space missions, including the Galileo space probe to Jupiter which was launched from the Space Shuttle Atlantis in October 1989.
“This material removal marks a huge milestone in the multi-year process to reduce the risk and clean up the PuFF Facility cells,” said 235-F Project Manager Jeff Hasty. “We started planning for removal in 2012 and have been preparing the cells since then."
Hasty said that work completed so far in the facility has included removing fixed combustibles, upgrading the fire detection system, de-energising unneeded electrical circuits, draining and cleaning shield windows after their partial disassembly, and installing light sources.
The PuFF Facility comprises nine cells of thick concrete walls with shielded windows. Employees who worked there handled hazardous materials using remote manipulators. Material entered the facility in Cell 1 and travelled through the other cells to be made into spheres and pellets.
"This project is extremely challenging," Hasty explained. “Along with the amount of material involved, we are also working in very tight spaces with limited accessibility. Because of the way the spheres and pellets were made, the Pu-238 was left in some cells as a very fine particulate dust that is easily disturbed. Every move we make will need to be slow, deliberate, and precise.”
Cell 1 is the most contaminated cell. Hasty says that work is expected to continue there for the rest of 2018 and 2019.
The Savannah River National Laboratory (SRNL) working with the 235-F Risk Reduction Team, determine that an estimated 1500grams of Pu-238 remain within the shielded cells. SRNL is using existing technology and developing new tools to locate and remove or affix the Pu-238 to ensure it will not become mobile during decontamination activities. Workers are also practicing cleanup work in a mock-up of 235-F
The material to be removed includes wires and manipulator handles. Operators will work remotely as they pass the items through the cells for removal. The cells will then be vacuumed and otherwise cleaned to remove the leftover plutonium. Any Pu-238 and tools containing Pu-238 to be safely stored for eventual packaging and shipment to EM’s Waste Isolation Pilot Plant in New Mexico.
Photo: Plutonium Fuel Form (PuFF) Facility (Credit: US DOE)