IMPLEMENTATION OF A REFERENCE NEUTRONICS CALCULATION SCHEME WITH DEPLETION FOR PWR CORES USING APOLLO3® CODE

The aim of this work is the implementation of a reference neutronics calculation scheme, for a Pressurized Water Reactor (PWR) core in 2-D in depletion, using the lattice part of APOLLO3®. The goal is to build a generic and complete scheme that can be used to validate the standard industrial simplified schemes. The ideal validation of these schemes is with Monte Carlo code but it is constrained by large computational cost and limitation in depletion. APOLLO3® is the new multi-purpose deterministic code developed by the CEA, in partnership with Framatome and EDF. It enables the computation of nuclear cores undergoing different operational conditions, in order to evaluate the physical quantities of interest for the design and operation of nuclear reactors. The implemented scheme is based on Method of Characteristics for 281 energy groups mesh for a small core geometry with heavy reflector whose internal part, including the assemblies, is built in APOLLO3® and the outer part by means of the external tool ALAMOS. The crucial point of the implementation is the evaluation of self-shielding on subdomains testing different methods. The reference case, validated with the results of the previous generation code APOLLO2 and the stochastic code TRIPOLI4®, is the less simplified in which the calculation of self-shielding is performed on the whole geometry. In this work, before the core, two preliminary cases are presented, the cluster 9x9 and the assembly 17x17, for some important aspects and for a first verification. The scheme is implemented yielding low reactivity discrepancies for the calculation in steady state and even in depletion. However, the most important characteristic to emphasize is that calculating the self-shielding on subdomains, although there is a greater approximation, the computational time is significantly reduced without having a deterioration in the accuracy of the results.