Not so secure after all? (Image: Jeff T. Green/Getty)

Waste from the production of US nukes is on the loose. Toxic cargo is escaping from six of the 177 ageing tanks at the Hanford site in Washington state where the nation stores two-thirds of its high-level nuclear waste, most of it from the production of nuclear bombs.

The site houses 200 million litres of radioactive and hazardous waste, and 67 tanks have leaked waste before. The new leaks undermine recent reassurances that the dump is now secure.

The biggest worry is that highly radioactive sludges containing heat-generating isotopes are corroding the bottoms of the tanks, following work to drain off most of the liquid waste which allowed the isotopes to collect there, says Bob Alvarez of the Institute of Policy Studies in Washington DC.

“There is no immediate public health risk,” said Lindsey Geisler, a spokesperson for the Department of Energy. However, much of the waste has already contaminated groundwater, says Tom Carpenter of Hanford Challenge, an environmental watchdog in Seattle, Washington.