Redetermination of the thermal-neutron absorption cross-sections of gross fission products of 233U, 235U and 239Pu

The thermal cross-sections of the long-lived gross fission products from 233U, 235U and 239Pu fission have been determined by pile oscillator measurements on highly irradiated samples. The samples, consisting initially of a single fissile nuclide in a matrix of high-purity aluminium, had been irradiated to a depletion of 70-90%, which gave a fission product contribution to the total absorption cross-section of about 10%. Measurements with these samples had previously been performed at AECL, but have now been repeated under more favourable experimental conditions. The fission product cross-sections have been determined with an accuracy of 5%. A comparison with a recent version of the calculational model FISSPROD shows that the calculated cross-sections are consistently about 7% higher than the measured ones. (author)