Generating cross sections for ORION fuel cycle models

ORION is a fuel cycle modeling tool developed at the UK National Nuclear Laboratory that can be used model once-through, limited recycle, and continuous recycle fuel cycle options. When modeling fuel cycle options with ORION, the fuel within the reactor can either use predefined charge and discharge recipes of spent fuel isotopes or one-group cross sections. Recipes work well for once-through fuel cycle models and steady-state scenarios, whereas cross sections improve accuracy for the more complex scenarios involving isotopic changes that occur during fuel cycle transitions and on the approach to equilibrium. This paper describes the importance of using cross sections based on fuel cycle scenarios, explains the method developed for generating ORION-formatted cross sections with SCALE, and demonstrates the impact of using cross sections versus recipes on fuel cycle analyses.