Description of the models and algorithms used in the CORE SIM neutronic tool

The development of an innovative neutronic tool is reported hereafter. The novelty of the tool resides in its versatility, since many different systems can be investigated and different kinds of calculations can be performed. More precisely, both critical systems and subcritical systems with an external neutron source can be studied, and static and dynamic cases in the frequency domain (i.e. for stationary fluctuations) can be considered. In addition, the tool has the ability to determine the different eigenfunctions of any nuclear core. For each situation, the static neutron flux, the different eigenmodes and eigenvalues, the first-order neutron noise, and their adjoint functions are estimated, as well as the effective multiplication factor of the system. The main advantages of the tool, which is entirely MatLab based, lie with the robustness of the implemented numerical algorithms, its high portability between different computer platforms and operative systems, and finally its ease of use since no input deck writing is required. The present version of the tool, which is based on two-group diffusion theory, is mostly suited to investigate thermal systems. Although the tool cannot be compared in terms of accuracy to existing core simulators, the definition of both the static and dynamic core configurations directly from the static macroscopic cross-sections and their fluctuations, respectively, makes the tool particularly well suited for research and education. This report describes the neutronic models and numerical algorithms implemented in the tool, whereas the validation and demonstration of the tool is reported in a companion report (Demazière, 2011a). The tool, for which a complete user’s manual exists (Demazière, 2011b), is freely available on direct request to the author of the present report