Savannah River Site officials have taken corrective actions — and fired two workers — after two incidents in H Canyon in which bundles of highly enriched uranium were dropped by a crane.
According to a Defense Nuclear Facilities Safety Board report — dated Aug. 21 and made public Thursday — the incidents “had potential criticality safety implications” and halted reprocessing operations for a week.
A criticality accident is one in which a chain reaction occurs, said Charles Nickell, the site’s nuclear materials disposition manager. “It is something we definitely don’t want to happen.”
The H Canyon area is where highly enriched uranium is loaded by cranes into vats of acid, called “dissolvers,” that help purify and convert the material from solid to a liquid form. The liquid is later blended with natural uranium to create low-enriched uranium and shipped off-site for use in the manufacture of fuel rods for commercial reactors.
On Aug. 3 — and again a week later — 200-pound bundles of highly enriched uranium fell from the crane and dropped about 15 feet into the dissolvers. It was later determined that a third bundle had become tangled but did not disengage and fall.
“The event had potential criticality safety implications because a damaged insert could allow undissolved fuel to drop to the bottom of the dissolver,” the board’s report said, adding that the failure of employees to properly report the problem compounded its significance.
Mr. Nickell said the resulting inquiry led to two corrective actions.
Engineers discovered small protrusions on the outside welds of metal caps that help guide the uranium bundles into the acid.
“We’ve used hundreds, if not thousands of them, with no trouble,” he said. “But we changed them to make sure they have a nice, smooth surface.”
The second action involved termination of two employees who failed to follow protocol in reporting the incidents. “A couple of folks made the decision not to do the right thing, and the message is that we clearly will not tolerate that sort of conduct.”
The processing activity was resumed about three weeks ago, he said, and no further problems have been reported.