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The status of the Canadian nuclear power program and possible future strategies

1975; Elsevier BV; Volume: 2; Issue: 11-12 Linguagem: Inglês

10.1016/0306-4549(75)90076-6

1873-2100

J.S. Foster, E. Critoph,

Radioactive element chemistry and processing

Canada is fortunate in having developed a versatile and flexible power reactor concept—one which can be kept economically competitive into the distant future, while at the same time offering opportunities for large reductions in uranium requirements. The one CANDU concept provides a range of alternatives, at least as extensive in terms of adaptation to changing economic and uranium supply conditions as that of most other nuclear power programs consisting of two or more distinct reactor types. The range includes reduced capital costs through use of boiling light water and organic cooled options, better thermal efficiency through use of the organic cooled option, and the ability to minimize the impact of changing economic parameters and improve uranium utilization through use of Pu recycle and/or thorium fuel with uranium recycle. AECL has devoted considerable effort over the last few years to study of advanced fuel cycles in the various CANDU reactor types. Very few feasibility questions have been uncovered. A detailed conceptual study of our currently favoured vehicle for Pu recycle, CANDU-BLW (PB), a plutonium burning, boiling light water cooled CANDU, has indicated that it could be initiated with no major problems. Development would be required in a number of areas—notably, fuel design and computational methods for fuel management. The results indicate a savings of some 15–20% in plant capital costs over the natural uranium CANDU-PHW and a reduction of almost a factor of two in uranium requirements. More general studies of thorium fuelled concepts are also encouraging. The reactor designs are almost identical to those for uranium CANDU reactors and so no new feasibility problems are introduced. We recognize feasibility problems associated with specific fuels in specific CANDU types, but there appear to be none in the areas of reactor physics, control, safety and fuel management. These concepts are competitive with CANDU-PHWs even for current economic conditions over a fairly wide range of reprocessing costs and/or separative work cost. Increasing uranium prices tend to favour the thorium fuelled reactors. The uranium requirements as a function of time depend on system growth rate but for any reasonable values the saving is at least a factor of two. As the growth rate slows this factor increases. In fact we envisage the possibility of thorium cycles with uranium recycle, which are self sufficient at equilibrium. This means a limited natural uranium requirement to establish and maintain a given electrical capacity. Requirements as low as 1 Mg (natural uranium)/MWe seem possible. We are currently studying these self-sufficient thorium cycles in more detail. We feel that the question is not so much whether the CANDU concept can be adapted to suit any particular set of economic and uranium supply conditions, but rather one of matching and timing. A large amount of work is required to determine the best system to match a given set of economic conditions or, with more difficulty, a given uncertainty band of economic conditions. The substantial time delays associated with any major adaptation make anticipation of future economic conditions important. Indeed at any time, the best system to design and build may be one which can be used with a variety of fuels rather than the optimum system for any one fuel. In order to capitalize on our present enviable position we will have to keep on top of these problems. In the U.S. the study of strategies for various plausible scenarios is important for long term planning, to provide a basis for decisions on types of reactors to develop. For Canada such studies are important for long term planning of development programs but will also likely be important for determining optimum operation of facilities. Some of the initial work detailing what I have been saying appears in our paper. The time seems ripe for serious consideration of Pu recycle and use of thorium, and yet in Canada there seems to be no need for undue haste in implementing these. Therefore we can contemplate an orderly research and development program which will put us in a position to adopt one or more of the many options in 10–20 yr time. Since our major uncertainties are in the areas of fuel reprocessing and active fuel fabrication these will be an important part of this program. It is not clear how our experience relates to U.S. problems. Certainly there are many conditions which are quite different in the two countries. The two most important are: (i) We have developed heavy water power reactors and the U.S. has not. (ii) The U.S. has a fast breeder program and we do not. I would like to stress the fact though that we really believe our program is a fully valid alternative (at least for us). We are quite willing then to explore with you the question of whether Canadian experience has any pertinence to problems associated with the U.S. nuclear power program.