Nuclear Data Requirements for the Production Of Medical Isotopes in Fission Reactors and Particle Accelerators

Simulations of isotope-production irradiations of targets in the radiation environments of fission reactors or particle accelerators require the evaluation of proton and/or neutron particle fluxes within the target and the integration of these with appropriate cross-section data. In fission reactors, proton fluxes are typically considered negligible and the approach reduces to neutron reactions at energies below the upper extents of the fission spectrum at which neutrons are born — 10 to 15 MeV. In particle accelerator target simulations, the secondary neutron flux can provide considerable production and/or collateral target activation. Where target and product nuclides are separated in Z and A, the relative contributions of neutron and proton reactions may not be apparent. Through decades of effort in nuclear data development and simulations of reactor neutronics and accelerator transmutation, a collection of reaction data is continuing to evolve with the potential of direct applications to the production of medical isotopes. At Los Alamos the CINDER'90 code and library have been developed for nuclide inventory calculations using neutron-reaction (En≤20 MeV) and/or decay data for 3400 nuclides; coupled with the LAHET Code System (LCS), irradiations in neutron and proton environments below a few GeV are tractable; additional work with the European Activation File, the HMS-ALICE code and the reaction models of MC-NPX (CEM95, BERTINI, or ISABEL with or without preequilibrium, evaporation and fission) have been used to produce evaluated reaction data for neutrons and protons to 1.7 GeV. At the Pacific Northwest National Laboratory, efforts have fo-cused on production of medical isotopes and the identification of available neutron reaction data from results of integral measurements.