ORIGEN (Oak Ridge Isotope Generation code) calculates time-dependent concentrations, activities, and radiation source terms for a large number of isotopes simultaneously generated or depleted by neutron transmutation, fission, and radioactive decay. ORIGEN is used internally within several neutronics codes for depletion and decay. As a stand-alone tool, ORIGEN provides unique capabilities to (1) simulate continuous nuclide feed and chemical removal, which can be used to model reprocessing or liquid fuel systems, and (2) generate alpha, beta, neutron and gamma decay emission spectra.

ORIGEN is currently distributed within the SCALE Code System available through the Radiation Safety Information Computational Center (RSICC) at https://rsicc.ornl.gov. Additional information on ORIGEN is provided at https://www.ornl.gov/division/rnsd/projects/origen.