Neutron reaction rate measurements in an organically moderated lattice of FTR fuel pins

Critical experiments are being conducted in the Battelle Pacific Northwest Lab.'s Critical Mass Lab. for the Consolidated Fuel Reprocessing Program using a variety of fast test reactor (FTR) fuel pin configurations and fissile solution concentrations. These experiments are being performed as part of a joint agreement between the US Dept. of Energy and the Power Reactor and Nuclear Fuel Development Corp. of Japan on criticality data development. On selected experimental assemblies in this program, absolute neutron reaction rates are being measured to provide basic neutron physics data for use in evaluating nuclear cross sections and calculational methods. The results obtained from the initial set of measurements in this program are presented in this paper. The initial series of reaction rate measurements were made in an experimental critical assembly of FTR fuel pins immersed in a tributylphosphate-normal paraffin hydrocarbon mixture