Integral and differential measurements as tests of neutron diffusion calculations in the Purdue University Fast Breeder Blanket Facility

The Purdue University Fast Breeder Blanket Facility (FBBF) was designed as a realistic mock-up of the radial blanket of a fast breeder reactor. Measurements made in the FBBF blanket can be used as benchmark tests of calculational methods used in the design of fast reactor blankets. Integral and differential measurements in the FBBF were used to test the accuracy of a two-dimensional diffusion calculation to the neutron flux. Neutron reaction rates for 238U capture, 55Mn capture, 232Th capture, 197Au capture, 186W capture, 114In capture, and 115In inelastic scattering were measured by activation analysis in three different blanket configurations of the FBBF. Circular metal foils were irradiated between the pellets in the blanket fuel rods. The absolute activity produced in each foil was measured with a Ge(Li) spectrometer system. Various corrections were made to the foil activities, and absolute reaction rates for the infinitely dilute target material were obtained. These reaction rates and previously measured fission rates and neutron spectra were compared with the results of the two-dimensional neutron diffusion calculation. The calculated absolute integral reaction rates compare favorably with the absolute measurements in the inner part of the blanket. The calculated results diverge from the measured results with increasing penetration into the blanket