Correlation of two-group theory with neutron flux measurements in a pool-type reactor

Abstract

A method for determining reactor system parameters that employs a compilation of two-group theory and detailed flux measurements is presented. Application of the semi-empirical procedure is illustrated for the University of Virginia pool-type reactor, loaded to approximate two-region cylindrical geometry. Measurements were made of the fast and thermal fission-producing fluxes, using highly enriched uranium foils, both bare and cadmium covered. The equivalent bare axial and radial components of the buckling were determined from the measurements, giving the principal buckling, μ² The related slowing down area, L₁², was adjusted so as to make two-group theory fit the experiment. The best value for the slowing-down area in the 0·40 aluminium-to-water mixture was found to be 42·5 cm² equivalent to an age of 38 cm². The slowing down area in the water reflector was found to be 25·5 cm², in fair agreement with fission-to-thermal age measurements reported in the literature.