Statistical approach to combined use of information on fuel elements

The stages in the production and use of fuel elements are shown schematically and the informational processes of pre-, in-, and postreactor monitoring (PM, IM, PoM) are isolated. Great effort has been exerted in PM and IM (20-30% of the fuel-element cost in the case of PM), but use of the results obtained has been far from complete - as a rule, within the limits of one episode of fuel-element 'biography.' Thus, for nonrated fuel elments, the whole volume of PM information reduces to one conclusion: fit or unfit. The most complete and reliable information on the state of the fuel element is determined in the post-reactor cycle of investigations, using a complex of destructive-monitoring methods. The lack of exhaustive theoretical description of the operating parameters of the fuel element in the reactor and the scale of expenditure required for the development of improved PM and IM systems, as well as the empirical selection of systems that are optimal for industrial application, are weighty arguments for the combined use of all information on pre-, in-, and postreactor monitoring with the aim of increasing the efficiency of atomic-power-plant operation. The algorithm proposed for determining the actual response of PM and IM systems is based on the mathematical model of monitoring and operation of the fuel elements, in which the random process of change in state of the fuel element on irradiation is determined and considered. The application of pre- and in-reactor monitoring methods within the framework of the given model allows some probabilistic characteristics of the above-noted random process to be obtained. This paper describes the model, and discusses determination of PM and IM efficiency, and practical application of the method