US nuclear waste strategies evaluated

Methods planned for transporting radioactive spent fuel from nuclear power reactors are generally safe, but questions remain over the safety of nuclear casks in the event of a sustained, hot fire, a review panel of the US National Academy of Sciences has concluded.

The NAS report released in Washington DC on Thursday, found there are "no fundamental technical barriers" to safe transportation, but that a number of "serious challenges" remain.

Assuming no new plants are built, disposing of fuel from the US's 112 operating plants will require a two-decade-long programme of daily shipments, and more planning needs to be done for managing this massive operation, the report says.

The report assessed the adequacy of planning for every kind of accident scenario, but not the potential for deliberate acts such as terrorist attacks. To evaluate that aspect, it says, would require creation of a new committee with full access to classified materials.

Trains versus trucks
There are several main scenarios under consideration for moving the 54,000 tonnes of high-level radioactive waste from the US's 103 nuclear power plants, and a similar amount from military weapons-production plants. One is the movement to their ultimate repository, proposed as the Yucca Mountain facility in Nevada. Another is transport to an interim storage spot or possibly to reprocessing facilities.

The material could be moved in an estimated 55,000 truckloads, or in 9600 dedicated trainloads and just 1000 truckloads, they say. The multidisciplinary panel "much preferred the rail option", says Neal Lane, its chairman, both because of the greatly reduced number of trips and because the rail lines are less subject to disruptions, such as traffic jams.

Research on the strength of the planned containment vessels or casks – which included dropping them from aeroplanes and slamming into them in simulated railroad crossing collisions – assures that they would survive any likely accident or natural disaster, except for the contingency of a very hot fire sustained over a long period, the report says.

Structural issues
Such fires have occurred, for example, in at least two cases where trains of petroleum-filled tanker cars burned for days before being controlled. The only way to minimise that risk for now, the panel concluded, is to make sure petroleum-carrying trains never get close to nuclear waste trains, but more research should be done on the effects of such fires on the nuclear casks.

More research is also needed on other points, such as the best ways of organising and coordinating the shipments, the panel says.

"There are significant questions" about the performance of the Department of Energy agency running the programme right now, panel member Seth Tuler told New Scientist. The report concludes that "changing the organisational structure for this programme will improve its chances for success".