Investigation of burnup dependent radial power distributions for highly enriched Halden test pins by the spectral code CIRTHE

CIRTHE is a one-dimensional collision probability method with burnup. Although primarily written for heavy water fuel rod cluster calculations, it can also be applied to light water moderated fuel lattices. CIRTHE calculations on PWR and BWR fuel rods have been checked against experiments involving capture rates of heavy nuclides, fuel temperature coefficients at full power conditions, relative concentrations of U- and Pu-isotopes in burnt fuel assemblies as well as xenon reactivities. A very satisfactory agreement between calculations and experiments was obtained. CIRTHE is well suited for application to HBWR conditions. Results of the analysis of ultra high burnup rig rods are presented. (author)