Broken pump delays cleanup at Hanford

RICHLAND – A broken pump has made it impossible to meet a deadline for emptying a troublesome radioactive waste tank at the Hanford Nuclear Reservation, officials said.

Today is the deadline for getting the S-102 tank 99 percent emptied, but a pump being used in the process recently broke down with 9 percent of the radioactive and hazardous chemical waste still inside, officials said this week.

Tank S-102, one of 149 single-shell underground tanks that were filled with waste from the separation of plutonium from irradiated fuel in the process of making nuclear warheads, contained 464,000 gallons when the effort to empty it began in December 2004.

The potentially lethal sludge is being transferred into newer double-shell tanks to await processing and disposal.

Workers are trying to determine whether enough waste has been emptied from Tank S-112 for the state to be satisfied that retrieval is complete.

Tank S-112, which would be the seventh of the 149 tanks to be emptied, has been used for technology demonstrations and was not under a legal deadline.

“S-102 was thought by many to be the hardest in the tank farm,” said Victor Pizzuto, vice president of closure operations for CH2M Hill Hanford Group, which worked on that part of the cleanup.

The gunk in Tank S-102 contains phosphates, which when heated and cooled turn gelatinous and clog the plumbing.

First the contractor used a high-pressure water spray to dissolve the waste so it could be removed by a pump at the center of the tank, but a cavity soon formed and little waste reached the pump.

Next workers used a “pump on a string,” a flexible hose with a cable and winch to suspend the pump in the liquids above the thick layer of sludge to prevent it from clogging, and got the tank about half emptied.

At that point CH2M Hill deployed a high-pressure mixing tool – called a viper – a rotating spray system mounted on a long shaft that is inserted directly into the waste.

That device enabled workers to boost the retrieval rate to 71 percent, and after two more vipers were added to break up the hardened heel of the waste 91 percent was gone.

Then the central pump broke.

Experts were trying to decide whether to install a new pump or try another method to dislodge and remove the remaining waste, but the 99 percent removal level won’t be reached by the Saturday deadline, said Ken Wade, the Energy Department’s project director for single-shell tank retrievals.

The deadline was set under an agreement by the Energy Department, the Environmental Protection Agency and the state.