Simulation of critical experimental nuclear arrays with the Serpent code

From the Nea/Nsc/Doc/(95) manual that contains criticality safety benchmark specifications, which have been derived from experiments conducted at several critical nuclear facilities worldwide, four experimental arrangements were chosen for simulation with the Monte Carlo Serpent code. The following experimental arrangements were simulated: 18 configurations of low enrichment UO₂ fuel rod arrangements with water to fuel volume ratios of 1.5 to 3.0, with specification number Leu-Comp-Therm-006; 29 configurations of U(2.35)O₂ fuel bar arrangements moderated with water and reflected by two walls of lead, depleted uranium or steel, with specification number Leu-Comp-Therm-017; bare metallic Pu-239 sphere (4.5 at. %, 240-Pu, 1.02 wt. % Ga), with specification number Pu-Met-Fast-001 and the critical reference experiment of a plutonium sphere reflected by thorium, with specification number Pu-Met-Fast-008. This paper describes the critical experimental arrangements; the geometry with its dimensions, the composition of the materials constituting the fuel, the moderator, the support structures and the material used as a reflector is provided. Likewise, the results of the multiplication factor obtained with the Serpent code and the comparison of these results with the experimental result are presented. It was shown that the simulation models prepared to simulate these experimental arrangements with the Serpent code were correctly designed, since the differences were minimal between the numerical results of the multiplication factor versus the experimental ones. Additionally, the validity and reliability of this code was confirmed for use in neutron calculations for any nuclear fuel arrangement. (Author)