Comparison of /sup 235/U and /sup 239/Pu alpha values obtained by analysis of irradiated BN-350 reactor fuel and by calculation

One of the most important components in the error of the breeding coefficient for fast reactors is the error in the value of alpha (the ratio of the radiation-capture and fission cross sections) for the fundamental fissile isotopes. It is possible to reduce the present error of approx. 10% to the required approx. 5% only through analysis of experiments on irradiated-fuel composition in fast reactors. Such experiments were performed on the BN-350 reactor. Fuel samples which had been irradiated in different periods of BN-350 operation with several different core configurations and compositions were subjected to radiochemical investigation. By means of calculations, all the experimental results were standardized to the radiation conditions in the central plane of the reactor core, which was in a mean steady-state condition. The calculations were carried out in three-dimensional geometry using the program TRIGEX with the utilization constant BNAB-78.