MCNPX characterization of the secondary neutron flux at the Los Alamos Isotope Production Facility

• MCNPX event generator simulations describe secondary neutron flux at the Los Alamos IPF.
• Medium-energy monitor reactions using metal foils experimentally validate MCNPX predictions.
• MCNPX is used to examine CEM03.02, Bertini, and TALYS reaction models of medium energy neutron-induced reactions.

The spallation neutron flux produced from proton irradiation of rubidium chloride and gallium targets at the Los Alamos National Laboratory (LANL) Isotope Production Facility (IPF) was investigated using the activation foil technique and computational simulation. Routine irradiations have been found to produce fluxes as high as 1012 n cm−2 s−1, with approximately 50% of the total flux having energy in excess of 1 MeV. Measurements of activation foils are compared with the predicted radionuclide yield using nuclear excitation functions from MCNPX event generators, evaluated nuclear data, and the TALYS nuclear code. Practical application of the secondary neutron flux in the realm of radioisotope production is considered.