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The release behavior of delayed neutron (DN) precursors from the breached fuel was analyzed, based on the diffusional release model. In this analysis, spherical co-ordinate simple approach as well as two-dimensional finite element method were used for the predomiant DN precursor 137I. It was shown that the fuel sodium reaction product (FSRP) layer at the pellet outer surface provided a predominant role for the accelerated release of DN precursors. The macroscopic diffusion coefficient for DN precursors in the FSRP layer was estimated to be 10−9 to 10−10 m2/s, which is greater than that in unreacted fuel by more than about 106. It was demonstrated that the DN signal response correlated to the growth of the FSRP layer, and did not depend on temperature change of interior fuel itself.

Starting from the experimental determination of the characteristic curve, the modulation transfer function and the Wiener spectrum of a considerable number of commercial colour and black-and-white films, several objective criteria of image quality (signal-to-noise ratio, information capacity, detective quantum efficiency, objective resolving power) COliid be determined under comparable corlditions for the first time. At a logarithmic representation the criteria give good linear correlation with the logarithm of sensitivity; tile slopes of the straight lines, however, slightly deviate from the theoretical values.