HELIOS: analysis of MOX critical experiments

Thirty UO 2–PuO 2 fueled light-water moderated lattice critical experiments have been analyzed with HELIOS at the Nuclear Engineering Program of the Pennsylvania State University, in collaboration with Studsvik Scandpower. These experiments were performed at Battelle Pacific Northwest Laboratories in the early 1970s. HELIOS is an advanced lattice physics code based on two-dimensional (2D) high order transport theory with complete geometric flexibility. The 30 cases have been analyzed already with HELIOS as single pin cell cases and these results are used for comparison. The present study involves the development of the HELIOS input decks for complete 2D representations of the estimated critical cores. The sensitivity of the calculated values of k eff for various options such as reflector thickness, energy groups, coupling order and the modeling approach used in this analysis are discussed for selected cases. Finally, the results of HELIOS have been verified by comparison with the experimental results.