More recently, Bowman [133] has proposed using a molten salt subcritical reactor for plutonium incineration with the principal aim of preventing its use for nuclear proliferation. The reactor would have the following characteristics:

• Thermal power: 750 Mwt.

• Molten salt fuel with NaF-ZrF4 carrier, fission fragments and plutonium fluorides.

• Thermal flux: 2 x 1014n/cm2/s.

• Moderator: graphite.

• ks = 0.96.

The reactor is fed with a mixture of fission fragments, zirconium and plutonium fluorides obtained through fluorization of the spent fuels and extraction by sublimation of the uranium hexafluoride. The yearly input would be 300 kg of plutonium and minor actinides, 1200 kg of fission products and zirconium cladding.[57] The output would be 65 kg of plutonium

and minor actinides, 1435 kg of fission products and carrier salt.

Following Bowman, the advantages of such a system would be:

• No weapons plutonium or other weapons materials in repository.

• Possibility of underground criticality in repository eliminated.

• 80% of fission energy recovered before waste emplacement.

• Instant irreversible elimination of weapons potential upon entry into transmuter.

The emphasis is clearly put on the prevention of uncontrolled military use of the plutonium in spent fuels. One TIER reactor would be associated with every 3000 MWt reactor, thereby eliminating the need for radioactive material transportation.

Further incineration of the remaining plutonium and minor actinides would require more elaborate chemical processing in order to separate

fission fragments. Special reactors would be devoted to the second stage of incineration. In this case, however, transportation would again be necessary, but with no risk of weapons materials smuggling.