munich

A US nuclear watchdog organization has called for the construction of a research reactor at a German university to be suspended on the grounds that the reactor's proposed fuel has been inadequately tested for safety.

The Technical University of Munich had planned to test a sample rod of the fuel — densely packed highly enriched uranium (HEU) — from the FRMII reactor in the SILOE reactor in Grenoble, France. But the university abandoned the idea when it became clear that the amount of heat generated would exceed the limits of the reactor.

Instead, university researchers tested a fuel rod of intermediate density — 1.5 grams of uranium per cubic centimetre instead of 3.0 grams — and extrapolated the results to the high-density fuels. This extrapolation was accepted by the Technische Überwachungs Verein, the German atomic-plant inspectorate that advises licensing authorities, to approve the building of the reactor, which began in 1996.

The Washington-based Nuclear Control Institute (NCI) has long argued that the reactor should not have been designed to burn weapons-grade HEU. Under a supplementary agreement to the Nuclear Non-Proliferation Treaty, signatories agreed to convert existing HEU-burning research reactors to low-enriched uranium (LEU), and not to build new HEU-burning reactors.

The NCI has written to the Bavarian environment minister, who will be responsible for licensing the operation of the reactor, saying that without complete tests “it is impossible for a licensing authority to certify the safety of a proposed reactor”.

But the university insists that the safety tests were sufficient and in accordance with international standards. “We have conducted tests on those parts of the fuel plates which have the highest uranium fission density,” says Gert von Hassel, spokesman for the FRMII project. Thus, he says, extrapolation to HEU fuel rods is legitimate.

The NCI says that the risks of catastrophic accident and nuclear terrorism could be averted if the reactor were redesigned to burn low-enriched uranium fuel. A recent study by the Argonne National Laboratory (ANL) in the United States indicated that the reactor could produce the same experimental performance if it converted. But according to von Hassel, the ANL proposal is limited to fuel consideration and says nothing about safety.

The reactor could still be forced back to the drawing-board if the opposition Social Democrat Party wins power in the September federal elections. The party wants an alternative reactor, based on the LEU, to be developed.