A few other types of fuel have been tried on a minor scale or have been irradiated in research reactors or as lead rods in commercial nuclear power stations. Metal fuel is still used in the UK Magnox reactors, but this reactor type is being phased out and will soon disappear. Metal fuel is produced from UF4 , which is mixed with magnesium metal and heated to about 600 °C. The UF4 and magnesium react leaving molten uranium metal at the bottom of the furnace. After cooling, the uranium metal is melted again, cast into rods, which are machined to size and length, and put into magnesium alloy tubes.

Vibration-compacted (VIPAC) fuel is made of granules with different size fractions, which are directly filled into the fuel tube without first making pellets. Vibration compaction can achieve a smear density of about 80-85% of theoretical density. Experimental irradiations have shown an acceptable performance (Knudsen et al, 1977; van der Linde, 1982).

After burning and unloading, spent LWR fuel has a higher equivalent fissile content of U-235 than natural uranium; it also contains plutonium. Fuel for ‘Direct Use of Pressurized Water Reactor Spent Fuel in CANDU’, DUPIC, could therefore continue irradiation in CANDU reactors after refabrication. In the DUPIC fabrication process, uranium, plutonium, fission products and minor actinides are retained in the fuel powder from which new pellets are produced (Bae et al., 1998; Lee et al., 2008). DUPIC fuel has to be fabricated in shielded facilities.