washington

The US Department of Energy is on the brink of delivering its first consignment of radioactive waste to permanent storage. This follows certification by the Environmental Protection Agency (EPA) that the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico, is ready to receive it.

Unless environmentalists succeed in two last-ditch legal challenges, the first shipment of low-level transuranic waste will arrive at WIPP from the Los Alamos National Laboratory on or soon after 19 June. The waste is clothing and equipment that has been contaminated by plutonium or other actinides in the US nuclear weapons complex, and which is now stored in steel barrels at 23 locations.

Although the waste is far less radioactive than the spent nuclear fuel and other highly radioactive waste that the United States hopes eventually to store at Yucca Mountain, Nevada, the certification of WIPP was described by Federico Peña, the energy secretary, as a “historic milestone”.

The opening of WIPP, in a salt bed 2,000 feet underground, would mark the first time the United States has buried any nuclear waste in a repository that is supposed to be permanent — and the first time in the world that such waste has been deposited deep underground. Sweden and Finland have permanent repositories, but these are close to the land surface.

Warren Weart of the Sandia National Laboratory, New Mexico, a senior manager on the WIPP project for 25 years, said last week that he is not taking a successful operation for granted. “I'll hold off on a final celebration until we actually place some waste,” he says. “I will be surprised if [opponents] don't try to block it or slow it down.”

Don Hancock, director of the Southwest Research and Information Center in Albuquerque, New Mexico, says that two lawsuits attempting to block the opening are pending — one against the EPA and one against the Department of Energy. They may attract the support of Tom Udall, the attorney-general of New Mexico. In contrast to Yucca Mountain, WIPP is supported by the governor and both senators in its home state.

Although not very radioactive — a tonne of it contains less than one-tenth of a curie — the transuranic waste contains elements such as plutonium which have long half-lives. So the argument about WIPP has focused on its ability to maintain its integrity for thousands of years. In 1996, a National Academy of Sciences panel concluded that it could do so if undisturbed by humans — but that a lack of disturbance, by oil drilling for example, could not be guaranteed.