Updated Shielding Analysis Methodology Applied to OPG Waste Management Facilites

Abstract

Ontario Power Generation has undertaken an update of its shielding analysis methodology for its waste management facilities which store irradiated fuel and re-tube waste fuel channel components. The modeling approximations and excessive conservatisms implicit in the previous toolset have been replaced by a more rigorous treatment of photon physics transport incorporating all exposure pathways using the Monte Carlo N-Particle (MCNP) code. The previous methodology considered doses from each building individually; the new method considers all buildings in a single “holistic” site model. Dose rate calculations using the new methodology have been compared against measurements through various validation exercises. The comparison shows good agreement between code prediction and measurements. This new approach allows OPG to with waste management facility site expansion in a manner which manages shielding design and margins to dose targets and realizes the principle of As Low As Reasonably Achievable.