Bildung der Aktiniden in bestrahlten HTGR-Brennelementen

Abstract

Actinide nuclide concentrations of 11 spent AVR fuel elements were determined experimentally. The burnup of the spheres varied in the range between 10 % and 100 % fifa, the Th : U ratio was 5 : 1. The separation procedures for an actinide isolation were tested with highly irradiated ThO$_{2}$. Separation and decontamination factors are presented. Actinide nuclide formation can be described by exponential functions of the type In m$_{nuclide}$ = A + B $\cdot$ % fifa. The empirical factors A and B were calculated performing aleast square analysis. Build-up of $^{232}$U was discussed. According to the experimental results, $^ {232}$U is mainly produced from $^{230}$Th, a certain amount (e.g. about 20 % at a 10$^{5}$ MWd/t burnup) originates from a n, 2n reaction of $^{233}$U, a formation from $^{232}$Th by a n, 2n followed by a n, $\gamma$reaction was not observed. The AVR breeding rate was ascertained to be 0,5. The hazard potential of high activity waste was calculated. After a 1000 year storage time, the elements Pa, Am and Cm willnot infiuence any more the total hazard index. Actinide recovery factors were proposed in order to reduce the hazard potential of the waste by an actinide removal under consideration of the reprocessing technology which is available presently