Mathematical and computational models for simulating transient nuclear criticality excursions within wetted fissile powder systems

This paper describes a novel methodology for the analysis of nuclear criticality excursions in fissile powder beds under wetting conditions. These potentially hazardous powder, slurry and sludge systems may be found fuel manufacturing fabrication facilities. A point neutron kinetics model was coupled with water infiltration, thermal–hydraulics radiolysis models through use reactivity feedbacks. Good agreement infiltration rate when comparing used this to experiments conducted by French Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA). case study proposed whereby sheet fine droplets from sprinkler system came into contact an open-topped bed low enriched UO2 powder. Simulations indicate that mean particle size had strong effect on time required percolate bed. Powder also predicted have moderate initial fission power spike. The energy released over first 300 s transient ranged 65.28 MJ 97.98 depending size. is similar magnitude other simulated beds. predicts spike would limited production radiolytic gas lesser extent effects Doppler broadening thermal expansion. As expected, boiling associated steam production, important phenomenon reduction negative void steam.