Comparison of experimental neutronics results and theoretical predictions for a gas core reactor

The development of a sound scientific data base that indludes key information in the areas of neutronics, thermo-physical properties and materials for cyclic gaseous core reactors has been the objective of a lengthy theoretical-experimental research program at the University of Florida. This paper presents results from the experimental neutronics phase of the research program. Static and dynamic neutronic experiments were conducted on the Plasma Core Assembly at the Los Alamos National Laboratory to measure selected fundamental nuclear parameters in a gaseous core critical assembly in which a significant fraction (approx.= 20%) of the fissioning took place in a gaseous uranium hexafluoride (UF6) fuel; the balance of the fission occurred in a ring of conventional solid driver fuel rods surrounding the central gaseous core region. Measured parameters were then compared with theoretically predicted values to determine the adequacy of various analytical neutronics schemes. In general, theoretical predictions obtained from the various computational schemes for key neutronic parameters were in good agreement with one another and also with experiment. For example, predicted neutron multiplication factors were typically within 2 to 5% of measured values and predicted reactivity worths were within 2 to 15% of measured worths. (orig.)