Thorium reactors generate interest in parliament
Support for additional research into thorium-fuelled nuclear energy is gathering pace after the formation of the Weinberg Foundation, a lobby group which is touting the technology as a “peaceful nuclear solution to the energy crisis”.
Thorium is a naturally occurring mineral that holds large amounts of releasable nuclear energy, similar to uranium. Crucially, the chemical and nuclear properties of thorium make it much easier to extract this energy completely than is the case with uranium, claim its proponents.
The Weinberg Foundation is advocating the transition away from uranium solid-fuelled reactors towards the development of liquid-fluoride thorium reactors (LFTRs). Conventional nuclear reactors use solid fuel elements. A liquid-fluoride reactor uses a solution of several fluoride salts, typically lithium fluoride, beryllium fluoride, and uranium tetrafluoride, as the basic nuclear fuel.
The fluoride salts are claimed to have advantages over solid fuels. They are impervious to radiation damage, they can be chemically processed in the form that they are in, and they have a high capacity to hold thermal energy. Additional nuclear fuel can be added or withdrawn from the salt solution during normal operation. LFTRs operate at low pressure and are chemically stable. They shut down passively and remove decay heat without human or mechanical intervention, removing the possibility of accidents such as that at Fukushima.
The Weinberg Foundation says that LFTRs produce less waste, as they consume 99% of their thorium fuel. Thorium and its derivative fuel, uranium-233, are also highly unsuitable for weapons, making nuclear proliferation or terrorism less of a threat.
Two liquid-fluoride reactors have been built, at Oak Ridge National Laboratory in Tennessee in the 1950s and 1960s. These were small research reactors. The first, which was called the Aircraft Reactor Experiment, ran for a week in 1957. The second, the Molten-Salt Reactor Experiment, ran between 1965 and 1969 and validated many of the principles of the fluoride reactor concept.
Prism power block
1. Steam generator
2. Reactor vessel auxiliary cooling system stacks (8)
3. Refuelling enclosure building
4. Vessel liner
5. Reactor protection system modules
6. Electrical equipment modules
7. Seismic isolation bearing
8. Reactor module (2), 311 MWe each
9. Primary electromagnetic pump (4 per module)
10. Reactor core
11. Intermediate heat exchangers (2)
12. Lower containment vessel
13. Upper containment building
14. Sodium dump tank
15. Intermediate heat transfer system
16. Steam outlet piping to turbine
17. Feedwater return piping