British Nuclear Fuels appears to have been using a flask that does not meet international safety standards to transport spent nuclear fuel from Germany since the 1980s.
The Department of the Environment Transport and the Regions withdrew BNFL’s licence to use the cylindrical NTL-11 flask on 20 February. This followed the failure of a quarter-scale model during a test in which it was dropped from a height of 9m.
A DETR spokesman said the failure meant the unit did not comply with the International Atomic Energy Authority’s safety regulations governing the transport of nuclear materials.
The DETR, as licensing authority, issues a new approval certificate for the flask every three years. But a BNFL spokesman said this was the first drop test on the NTL-11 flask since 1978. Its design was, however, modified in the mid-1980s to incorporate a thermal shield in the shock absorber.
Two bolts on the shock absorber sheared during the test, causing the unit to shift position.
As a result, BNFL did not carry out fire or immersion tests on the flask. The same failure occurred when BNFL repeated the test on 6 March.
The spokesman said the company was carrying out an urgent redesign of the NTL-11 to get it licensed by early next year.
Otherwise it will have to apply for a licence to use one of its other flask designs in Germany a lengthy process that might allow a build up of too much spent fuel at the plant for its storage ponds to handle.