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Vitrification line tested for Japanese waste

Tuesday, 6 November 2007

Active testing has begun at the radioactive waste vitrification line of Japan Nuclear Fuels' new Rokkasho reprocessing plant. The plant could begin full operation in February 2008 separating uranium and plutonium for reuse and conditioning waste for disposal.

Active testing has begun at the radioactive waste vitrification line of Japan Nuclear Fuels' (JNFL's) new Rokkasho reprocessing plant.

This final major test at Rokkasho comes 20 months after active tests began at the plant - when used nuclear fuel was input to the shearing process - and four months before the plant is expected to begin full operation in February 2008.

Engineers began pouring a mixture of dry waste residue and molten glass into stainless steel canisters at 10.20am on 5 November. The glass hardens within the canister, which is welded shut and stored in a special ventilated facility. Ultimately, it is Japan's policy to dispose of its high-level radioactive wastes in a facility about 300m underground.

In reprocessing, highly-radioactive used nuclear fuel is cut into small segments and dissolved in acid. Fragments of steel are removed by centrifuge and then a chemical process separates the 3% highly-radioactive fission products from the 96% uranium and 1% plutonium, both of which are only mildly radioactive.

The benefits of reprocessing are that the volumes of waste after vitrification are many times less than the original volume of the nuclear fuel assemblies, and the uranium and plutonium recovered can be reused in fresh mixed-oxide (MOX) nuclear fuel for light-water reactors or fast-breeder reactors. The plutonium produced by light-water reactors cannot be used in weapons, but the Rokkasho plant takes the extra precaution of separating uranium and plutonium together.

Historically, Japanese companies have contracted British and French firms to undertake this work. France's national nuclear company, Areva, cooperated with JNFL to build Rokkasho based on its own La Hague plant.

JNFL is also in the process of developing a neighbouring facility to produce MOX fuel using the uranium and plutonium. Construction is set to start in coming months with completion around 2012. Even using foreign-produced MOX, some 16-18 Japanese reactors could be using the fuel by FY2010.

Further information

Japan Nuclear Fuel Ltd (JNFL)

WNA's Mixed Oxide Fuel (MOX) information paper
WNA's Nuclear Power in Japan information paper
WNA's Processing of Used Nuclear Fuel for Recycle information paper

WNN: JNFL delays construction of MOX plant