While the spill itself took place back in late July, the legal proceedings brought by the Washington State Department of Ecology have only just been completed.

The fine relates to an incident at the Hanford Site, the world’s largest contaminated site which was originally used to provide enriched plutonium for the USA’s nuclear weapons programme.

While the site is no longer used for production of nuclear material, remediation work is ongoing.

On July 27, contractors were pumping high-level radioactive waste from a leaky storage tank when the pump became blocked.

An attempt to unblock the pipe by running the pump in reverse resulted in some 300 litres of high-grade waste being sprayed onto surrounding land, endangering workers and brining a halt to the clean-up of the underground tanks.

“Over 80 gallons of highly radioactive tank waste spilled to the environment,” said Jane Hedges, manager of the Washington Ecology Department’s nuclear waste programme.

“Before the spill was discovered, a series of poor decisions put workers in grave danger from exposure to the tank waste and vapours. This accident calls into question the adequacy of the safety culture which is so critical at the tank farms.”

The state department investigated the circumstances surrounding the spill, including the equipment design, incident notification, and emergency response. A series of administrative and engineering failures were found to have contributed to this accident.

The Department of Energy conducted its own investigation, which identified several major contributing causes including engineering reviews and testing, work controls, industrial hygiene, radiological protection, medical response and emergency management.

“The raw water system used to provide dilution water for the pump had no backflow equipment to prevent waste from backing up into it,” said Eric Van Mason, inspector for Washington Ecology.

“The system is designed to supply water, not to transfer or contain waste. When the pump was run in reverse, tank waste travelled into a rubber hose above the ground. The rubber hose ruptured, resulting in the spill.”

Mr Van Mason said poor lighting and a lack of staff during the graveyard shift when the accident had occurred had also exacerbated the situation.

Ms Hedges said she was also troubled by the response time, saying it took way too long for contractors and the DoE to notice anything was amiss.

The second violation involved inadequate engineering reviews. The Tank Waste Retrieval System design was not adequately or fully reviewed in accordance with state regulations.

“There was a delay of more than seven hours from the time the first high radiation readings were discovered,” she said.

“This is completely unacceptable.”

Sam Bond

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