Messungen und Berechnungen zur Sr-90-Freisetzung aus HTR-Brennstoffelementen

Abstract

Coated fuel particles were investigated in post irradiation experiments. Sr-90-fractional releases from single particles were measured during isothermal anneals. The time-dependent fractional release curves were analyzed with the aid of simple diffusion theory and delivered temperature dependent diffusion constants. For oxide kernel material with burn-up values up to 30% fima it resulted: D$_{Sr-90}$ =3,5 $\cdot$ 10$^{-5}$ $\frac{m ^{2}}{sec}$ e - $\frac{409 000(Joule/mol)} {RT}$ Additionally some measurements were done on kernels with additives and TRISO coated particles. Moreover these data and other data from literature were used in a parametric study to determine the data's influence upon Sr-90 Core releases of 3000 MW$_{th}$-plants. The results show, that all calculated forecasts remain sufficiently low as for oxide fuel, but increase to evidently higher release values as for carbide kernel materials