Project Continuation Proposal: Radiation Transport Modeling of Beam-Target Experiments for the AAA Project

The AAA program will rely on the use of an accelerator-based transmuter1 to expose spent nuclear fuel to high-energy neutrons. The neutron flux will be sufficient to activate or fission the long-lived isotopes of Tc, I, Pu, Am, Cm, and Np that present a significant radiological hazard in commercial spent fuel. Transmuter fuel will be subcritical and a high-energy proton accelerator is needed to maintain the necessary neutron flux through the use of a neutron spallation target. The maximum neutron energy produced by spallation (~ 800 MeV) is significantly higher than that produced by a commercial light water reactor (~ 2 MeV). To design the nation’s first transmuter, the neutronics code MCNPX will be used to model the distribution of neutron flux within the fuel blanket and to determine the neutron multiplication, keff. However, the cross section libraries and computational methods used by MCNPX at these neutron energies still have some uncertainty and will require validation. During the second year of the project, the goals include: • Continue analyses of the neutron leakage tests completed in July 2002 and to be conducted on LANSCE in December, 2002. • Prepare simulations of the December 2002 tests to provide input on the test design. • Complete work started in the first year on a benchmark program for the validation of MCNPX for transmutation studies. This program will be designed along the lines of the international nuclear criticality benchmark series