HOW MUCH OF THE ROCKS AND THE OCEANS FOR POWER? EXPLOITING THE URANIUM- THORIUM FISSION CYCLE
Even at quite low costs there appear to be many routes available to supply the world population of the future with its power for electricity, heat, energy storage, portable fuel, desalting water and local climate control. For example, sufficient power could come from nuclear fission in thermal neutron reactors. When rich uranium ores have become scarce, the price will rise from the current $13/kg U, but with improved techniques of extraction and the choice of an economical fuel cycle, abundant uranium for many centuries appears to be available in the rocks and the oceans. Even from reactors already developed to the stage of engineering design it is possible to choose a fuel cycle to which uranium at $250/kg U would contribute no more than 2 mill/kWh. Without suggesting when such a high cost might be reached, its implications are examined. The optimum fuel cycle would balance the financing charges on the fuel inventory and the costs of fuel make-up supply and reprocessing. By using uranium and thorium in combination at least 50,000 MWd can be derived per tonne of uranium. At a current low net conversion efficiency of 30% and an overall rating of 6 thermal kW/kg, the natural uranium inventory would cost at the suggested high price $250/(6 x 0.3) $139/ekW and for 7000 hr/yr at 7% annual charges would contribute 1.4 mill/ekWh. At 50 MWd/kg U the make-up supply contributes 250/(50 x 24 x 0.3) = 0.7 mill/ekWh. Probably higher efficiency and possibly higher specific power ratings would be used to lower such costs. The value of uranium is related to its content of the fissile U-235, and even though most power may be derived from thorium, its value will not rise comparably with that of uranium. In the course of time a ceiling will be set on the value of fissile material by the introduction of processes other than the thermal neutron fission chain reaction for producing power or neutrons. The total cost of nuclear power includes also contributions from the cost of equipment and plant operation as well as of fabricating and processing materials. Any other technique or fuel cycle cannot supplant the thermal fission reactors merely by showing a lower demand for fissile material, but if plant and operating costs are not excessive, may enter the competition or become a valuable supplement. Three such techniques have for many years been recognized as (1) Fast neutron breeders; (2) Neutron production by the excitation of heavy nuclei to high energies; and (3) Controlled thermonuclear fusion. (author)
- Research Organization:
- Atomic Energy of Canada Ltd., Chalk River, Ontario (Canada)
- NSA Number:
- NSA-18-026917
- OSTI ID:
- 4079176
- Report Number(s):
- AECL-1916; DM-72
- Country of Publication:
- Canada
- Language:
- English
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