Active direct measurement of residual fissile content in spent fuel assemblies. Final report

The feasibility of direct nondestructive measurements of the residual fissile content of spent LWR fuel assemblies is studied. The requirements of such nondestructive assay (NDA) techniques are determined by the general characteristics of highburn spent fuel assemblies and by the nature of practical techniques for in-situ measurement in nuclear power sites. A generic measuring system, encompassing several possibilities for detectors and sources and forming the basis for all the calculations for this study, is defined on the basis of the various requirements. The general principals of active NDA techniques, inducing fissions and detecting some of the emanated penetrating radiations, are discussed. Possible measuring techniques, based on isotopic sources and accelerators, are discussed. Guided by the results of the study a conceptual engineering layout of a proposed measuring system has been prepared. Also discussed in this study are the relative merits vs. the technical difficulties of a waterless system (a system with uncooled or gas cooled spent fuel assembly)