Hi, Notster:

Thank you for introducing the question of nuclear energy to Noront's audiences. Someone should also introduce this topic to Queen's Park. About 40 percent of Ontario's electricity base load is generated by safe and clean nuclear power, 24 hrs x 7 days per week.

With reference to your above posting I would like to mention that in the 1970-es Atomic Energy of Canada actively investigated thorium and mixed-fuel cycles for its reactors. The idea seems to have been moth-balled, and they continued with the current natural-uranium fuel cycle.

Extensive literature is available on this subject, in the following I just outline some of the fashions within the topic:

Thorium Fuel Cycles

There has long been an attraction for fuel cycles using thorium as a thermal breeder of fissile material (U-233). Thorium is three times as abundant as uranium in the earth’s crust, and U-233 is valuable as a fissile material due to its high value of fission neutrons produced per thermal neutron absorbed (eta).

Existing CANDU reactors can operate on thorium fuel cycles, with comparable fuel-cycle costs to the natural-uranium cycle and with improved uranium utilization. While ultimate efficiency is achieved with a self-sufficient cycle that relies only on bred U-233, economical once-through thorium (OTT) cycles can greatly extend uranium resources.

Several options have been identified for the use of OTT in CANDU reactors (Milgram, 1984), and on-power refuelling is the key to successful exploitation of this material. Two general approaches have emerged: the "mixed-core" approach, and the "mixed-fuel-bundle" approach (Boczar, 1998).

In the "mixed-core" approach, a number of "driver" channels provide the flux requirements for a fewer number of "breeding" channels filled with thorium-oxide fuel. This is the conventional CANDU-OTT strategy, and has the potential to be competitive, in terms of resource utilization and economics, with both natural-uranium and SEU fuel cycles (Milgram, 1982; Dastur, 1995). Complex fuel management is required to handle the different characteristics and residence times of the two fuel types.

In the "mixed-fuel-bundle" approach, thorium oxide is contained in the central elements of a fuel bundle, and SEU is contained in the outer elements. Although uranium utilization and thorium irradiation are not as good as in the "mixed-core" approach, uranium utilization is improved over the natural-uranium cycle (but not SEU), with comparable costs. Fuel management is much simpler than in the "mixed-core" approach, and refuelling rates are about a third of that required with natural uranium (Chan, 1998).....

Cheers,

durban1