Validation of Simplified Evaluation Models for First Peak Power, Energy, and Total Fissions of a Criticality Accident in a Nuclear Fuel Processing Facility by TRACY Experiments

Simplified evaluation models are developed at the Japan Atomic Energy Research Institute (JAERI) to predict the first peak power, energy, and total fission numbers during a criticality accident for design and installation of a criticality alarm system and for quick response with measures to avoid excessive exposure of the general public. These models were first derived in previous papers only from theoretical considerations employing one-point reactor kinetic neutron behavior and thus are applicable to any geometrical shape of vessel containing fissile solution. Applicability concerning nuclide composition comes essentially from using empirical equations describing specific heat and density to give simplified forms of the models. The models developed originally for a stepwise reactivity insertion mode are shown in the current paper to approximately stand for the ramp reactivity insertion mode by giving their theoretical formation and are validated by applying experimental data from JAERI's Transient Experiment Critical Facility (TRACY) on a low-²³⁵U-enriched uranium nitrate solution as well as CRAC experiments on high-²³⁵U-enriched uranium nitrate solution together with past accident data, including the most recent JCO accident.