THE EFFECTS OF FLUX SPECTRUM PERTURBATION ON TRANSMUTATION OF ACTINIDES: OPTIMIZING THE PRODUCTION OF TRANSCURIUM ISOTOPES

摘要

The research presented herein involves the optimization of transcurium isotope production in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Due to the strong dependence of isotopic cross sections upon incoming neutron energy, the efficiency with which an isotope is transmuted is highly dependent upon the neutron flux energy spectrum and intensities. There are certain energy ranges in which the rate of fissions in feedstock materials can be minimized, relative to the rate of nonfission absorptions. Therefore, it is proposed that by perturbing the flux spectrum, it is possible to increase the production yield key isotopes for the heavy element research program, such as ~(249)Bk and ~(252)Cf, which are produced during a transmutation cycle, relative to the consumption of feedstock material. The optimization process is carried out by developing an iterative objective framework that involves problem definition, flux spectrum and cross-section analysis, simulated transmutation, and analysis of final yields and transmutation parameters. It is shown that it is possible to perturb the local flux spectrum in the transcurium target by perturbing the composition of the target. It is further shown that these perturbations can alter the target yields in a significant way, increasing the amount of ~(252)Cf produced per feedstock consumption by over 8%. Future work is necessary to develop the optimization framework and to identify the necessary algorithms to update the problem definition based upon progress toward the production of the desired transcurium isotope.