Nuclear Fuel with Thorium The Same Proliferation
Problems as with Plutonium
India is interested by the development of a new type of nuclear fuel
based on uranium-233, the fissile radionuclide associated with thorium.
Standard reactors use enriched uranium, which is uranium with a higher
(3-4%) share of uranium-235 than natural uranium (0.7% U-235). Uranium-235
is the fissile radionuclide on which is based the reactivity in such
reactors. The other radionuclide which is contained in natural uranium
is uranium-238. During the nuclear reaction, some of the uranium-238
is transformed (when capturing a neutron) into plutonium-239. Recently,
utilities have started using fuel based on plutonium (Pu-239) as fissile
radionuclide in so called MOX fuel (see earlier issues of Plutonium
Investigation for more details). India is using experimental fuel rods
based on uranium-233 in the Kamini 30 kWth research reactor. The uranium-233
was recovered through reprocessing (chemical dilution) of the experimental
fuel rods based on thorium - in the same way as plutonium is separated
through reprocessing of uranium nuclear fuel.
However, while plutonium is the material which is most used for fission
type nuclear weapons, uranium-233 has similar proliferation characteristics
as plutonium. According to J. Magill et al. from the European Commission's
Joint Research Center (JRC), "in contrast to reactor grade plutonium
associated with the uranium cycle, where sophisticated engineering is
required for the implosive assembly, the reactor grade uranium from
the thorium fuel cycle could be assembled by a relatively simple gun
type device". The minimum quantity of uranium-233 which is required
to produce an explosive device (critical mass with reflector) is given
to be 5 kg, which is less than most of the plutonium bomb designs require.
Developing technology for uranium-233/thorium fuel might further worsen
India's nuclear proliferation record - and the relationship between
India and countries concerned about the threat of nuclear proliferation.
of the Plutonium in India (Pdf format, 90 Ko)