Some Parameters Determining the Efficiency of Facilities for Disposing of the Long-Lived Elements of Nuclear-Power-Generation Wastes

Abstract

The formulations and assumptions for the problem of disposing of the long-lived elements in the wastes from nuclear power generation are examined. Criteria for the efficiency of facilities are proposed. It is shown that the efficiency of waste-disposal facilities is largely determined by the prescribed duration of the elimination process.One solution to the problem of handling long-lived transuranium elements in wastes which has been discussed in recent years in our country and abroad is to remove them by converting them into fission products under irradiation in critical or subcritical breeding systems [1][2][3][4]. Various, and sometimes diametrically opposite, points of view concerning the most effective types of systems for waste disposal have been advanced and discussed. Specifically, should the systems have a fast or thermal spectrum? The arguments made in support of one or another point of view do not convince the opponents, and no universally accepted opinion has thus far been advanced. The proponents of the opposite approaches are, in their own way, actually correct.In the opinion of the present author, this situation has developed because of the lack of a clearly formulated problem for waste disposal, which makes the proposed solutions ambiguous. In the present paper, some formulations and assumptions, on which the formulation of such a problem could be based, are presented. In addition, additional parameters for the efficiency of waste-disposal facilities are proposed. In the opinion of the present author, taking account of these assumptions will make it possible to avoid ambiguity in the solutions for choosing the type of facility.Basic Concepts and Definitions. The initial long-lived wastes consist of a mass of long-lived transuranium elements with a definite composition, which are formed as a result of nuclear power generation and are brought into the disposal process.The disposal of the initial long-lived elements in the wastes is the process of converting them into fission products by irradiation in breeding facilities (critical and subcritical).The final long-lived elements of the wastes comprise the mass of all long-lived transuranium elements of the wastes (i.e., initial and formed during the elimination of the initial wastes), remaining after the elimination process has been completed.The degree of elimination is the ratio of the mass of the wastes which are destroyed to the mass of the initial wastes. The ecological gain is the ratio of the levels of ecological danger of the initial and final wastes. The level of ecological danger of the wastes can be characterized, for example, by their radiotoxicity.The problem of disposal is the choice of the type of breeding facility for disposing of the initial wastes and determining the optimal fuel cycle for facilities of the type chosen.Some Assumptions of the Problem of Disposal of Radioactive Wastes. The mass of the initial wastes which are subject to disposal is given.