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Explosion risk identified at US nuclear waste dump

04 April 2013

The Defense Nuclear Facilities Safety Board expressed concerns on April 1 to US Senator Ron Wyden, D-Ore, that hydrogen gas could build up inside underground tanks holding radioactive waste at the Hanford Nuclear Reservation in Washington State, leading to an explosion that might release radioactive material.

The board, speaking in advance of confirmation hearings for the next leader of the Energy Department, recommended additional monitoring and ventilation of the tanks last fall, and federal officials are working to develop a plan to implement the recommendation.

Sen. Wyden, who is chairman of the Senate Energy and Natural Resources Committee, had sought the board's perspective about cleanup at Hanford.

The federal government created Hanford in the 1940s as part of the secret Manhattan Project to build the atomic bomb. It spends billions of dollars to clean up the 586-square-mile site next to the Columbia River, the southern border between Washington and Oregon and the Pacific Northwest's largest waterway.

Six underground storage tanks at Hanford were recently found to be leaking radioactive waste, but there is no immediate risk to human health, state and federal officials said in February. Technical problems have delayed construction of a plant to treat the waste for long-term safe disposal.

The Energy Department said after the leaks were brought into the public domain that declining liquid levels in one tank at Hanford showed it was leaking at a rate of 150 to 300 gallons (568 to 1,136 litres) per year.

It subsequently informed state officials that a second, larger tank was leaking at about the same rate, while the four smaller tanks were leaking at a rate of about 15 gallons per year. The Department said that monitoring wells have identified no significant changes in concentrations of chemicals or radionuclides in the soil.

The seeping waste adds to decades of soil contamination caused by leaking storage tanks at Hanford in the past and threatens to further taint groundwater below the site but poses no near-term danger of polluting the Columbia River, officials said.

Those issues are likely to come up during confirmation hearings next week for Energy Secretary-nominee Ernest J. Moniz. Huffington Post says the fears of explosion and contamination could give Washington and Oregon officials more clout as they push for cleanup of the World War II-era site.

Central to the cleanup are the removal of 56 million gallons of highly radioactive, toxic waste left from plutonium production from underground tanks. Many of the site's single-shell tanks, which have just one wall, have leaked in the past, and state and federal officials announced in February that six such tanks are leaking anew.

"The next Secretary of Energy - Dr. Moniz - needs to understand that a major part of his job is going to be to get the Hanford cleanup back on track, and I plan to stress that at his confirmation hearing next week," Wyden said in a statement Tuesday.

The nuclear safety board warned about the risk of explosion to Wyden, who wanted comment on the safety and operation of Hanford's tanks, technical issues that have been raised about the design of a plant to treat the waste in those tanks, and Hanford's overall safety culture.

In addition to the leaks, the board noted concerns about the potential for hydrogen gas buildup within a tank, in particular those with a double wall, which contain deadly waste that was previously pumped out of the leaking single-shell tanks.

"All the double-shell tanks contain waste that continuously generates some flammable gas," the board said. "This gas will eventually reach flammable conditions if adequate ventilation is not provided."

It also noted technical challenges with the waste treatment plant, which is being built to encase the waste in glasslike logs for long-term disposal. Those challenges must be resolved before parts of the plant can be completed, the board said.

The federal government spends about $2 billion annually on Hanford cleanup – roughly one-third of its entire budget for nuclear cleanup nationally. About $690 million of that goes toward design and construction of the plant. Design of the plant, last estimated at more than $12.3 billion, is 85% complete, while construction is more than 50% complete.

The problems identified by the board show that the plant schedule will be delayed further and the cost will keep rising, Wyden said, adding: "There is a real question as to whether the plant, as currently designed, will work at all."


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