DONJON5/CLASS coupled simulations of MOX/UO₂ heterogeneous PWR core

Most fuel cycle simulation tools are based either on fixed recipes or assembly calculations for reactor modeling. Due to the high number of calculations and extensive computational power requirements, full-core computations are often seen as not viable for this purpose. However, this leads to additional hypotheses and modeling biases, thus limiting the physics realism of the resulting fuel cycle. For several applications, the current modeling method is sufficient, but precise calculations of discharged compositions may require further refinement. CLASS (Core Library for Advanced Simulation Scenarios) is a dynamic fuel cycle simulation code developed since 2012 with reactor models based on neural networks to produce nuclear data and physical quantities. Past work has shown a first coupling between CLASS and DONJON5 to quantify neural networks approach biases. This work assesses the applicability of 3D full-core calculations using a deterministic calculation code coupled with nuclear scenario simulations to allow realistic simulation of a full PWR core at equilibrium cycle conditions. The deterministic calculation is provided by the chaining of DRAGON5 and DONJON5. DONJON5 enables interpolation of burnup dependent diffusion coefficients and cross sections generated beforehand by DRAGON5, a deterministic lattice calculation tool. Whereas the first reference considered only homogeneous reactors (i.e. homogeneous assembly in terms of composition and enrichments as well as homogeneous core), the present contribution focuses on the integration of full-core calculations in CLASS for fuel cycles involving a MOX/UO₂ PWR core (i.e. 1/3 MOx - 2/3 UOx). The DONJON5 model considered in this work is for a core with critical boron concentration at equilibrium cycle conditions loaded partially with MOx heterogeneous assemblies composed of three enrichments. In fuel cycle calculations, the main issue is to adapt, in the fabrication stage, the fresh fuel composition for the reactor with regards to the isotopic composition of the available stocks. This work presents a fuel loading model based on power-peaking factors minimization that respects cycle time reloading scheme, ²³⁵U enrichment as well as Pu concentration and fissile quality, hence, ensuring a more uniform power distribution about the core. The full paper will provide an illustration as to the viability and robustness of this new multiparameter fuel loading model. Also, results obtained via our deterministic approach for homogeneous and heterogeneous rectors will be discussed. (authors)