The Hanford tank farm contractor has received a letter of enforcement related to the possible freezing of radioactive waste in transfer lines.
However, the Department of Energy Office of Enforcement and Oversight, which issued the letter, did not issue a notice of violation or take enforcement action.
Washington River Protection Solutions, which operates the tank farms for DOE, discovered the potential problem in late summer and reported it to DOE. The tank farms include 172 underground tanks holding 56 million gallons of radioactive waste from the past production of weapons plutonium.
It discovered that no analysis had been done to see if radioactive waste, moved between tanks in above-ground lines, could freeze and potentially causing pipes to burst or damaging valves.
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Waste has been transferred through the above-ground lines for more than a decade without a documented problem.
"But it's a potential accident scenario and that's not acceptable in a nuclear environment," said John Britton, a Washington River Protection Solutions spokesman.
Analyses had been done that assumed a temperature of 32 degrees, but should have been done for temperatures down to minus 25 degrees, according to the letter.
In addition, dropping temperatures could cause solids to precipitate out of the waste, potentially clogging safety relief valves designed to open if the system becomes over-pressurized.
A new analysis is being done, but in the meantime a temporary plan is in place that allows waste to continue to be transferred, including from leak-prone single shell tanks to sturdier double shell tanks.
Cables are available to be used to heat up the lines, and thermocouples measure temperatures and provide readings that are transmitted to workers. Limits also have been set on operations in the cold.
Washington River Protection Solutions identified the issue and is using extensive interim administrative controls to continue waste transfers, the letter said.
However, the Office of Enforcement is concerned about the processes used to ensure waste transfer hazards and potential accidents are fully analyzed and controlled, the letter said.
"It is the responsibility of WRPS to ensure that personnel involved in these processes are fully trained and qualified on all technical aspects," the letter said.
-- Annette Cary: 582-1533; email@example.com; more Hanford news at hanfordnews.com