Simulation of a NuScale core design with the CASL VERA code.

• CASL VERA represents a new tool for fuel loading pattern optimization for SMR simulations. • The single fuel assembly calculations provided by the CASL VERA are in a good agreement against the Polaris or Serpent calculation. • The 3D full core calculations with water reflector are in a good agreement against Serpent calculation code. • The 3D full core calculations with stainless steel reflector are in a worse agreement with Serpent calculation code. The optimal stainless steel fraction to het reasonably good results against the Serpent code, was set up to 90%. • Stainless steel reflector extends core operation, moreover it balances the power generation in the SMR NuScale core. Three-dimensional (3D) full-core calculations are an integral part of fuel reload design for today's light water reactors (LWRs). The current approaches are typically based on the nodal diffusion codes that calculate criticality state points and power distributions as a function of burnup. The CASL VERA (Consortium for Advanced Simulation of Light Water Reactors, Virtual Environment for Reactor Applications) code represents one of the latest advancements in 3D full-core calculation analysis based on transport theory methods employing the Method of Characteristics (MOC) and coupled multi-physics. In this article, a publicly released version of the NuScale reactor core is analysed with the VERA code (version 3.9 and 4.1) and contrasted against some static Serpent and Polaris based simulations. The analysis shows an excellent agreement for the lattice-level calculations as well as with some of the 3D full-core models. However, larger deviations were found in cases with heavy reflector models, whereby the reflector composition was found to impact the differences between the VERA and Serpent results. In this analysis, it was determined that greater than 90% stainless steel content in the heavy reflector leads to higher deviations between the VERA results and the Serpent results. The burnup calculations showed that the presence of the heavy reflector extends the cycle length and also leads to a flatter power distribution in the core, which can generally be interpreted as more efficient. [ABSTRACT FROM AUTHOR]