Discussion of Neutronic Calculation Methods

The FDM is a numerical method in use since the early days of nuclear reactors it solves the multi-group neutron diffusion equation with a homogenized fine mesh structure. Owing to its simplicity, flexibility in geometrical description, and reasonable calculation time cost, the FDM is still being used today for conceptual design of various core types. 

Modem nuclear design methods for commercial LWRs have been based on nodal methods the nodal expansion method (NEM), analytic nodal method (ANM), and analytic function expansion nodal method (AFEN). The nodal method treats a fuel assembly as a node, and an intra-node neutron flux is expressed as a synthesis of a polynomial expansion (NEM) or an analytic solution for each direction (ANM), or its combined expansion (AFEN), which provides very fast solutions for core design. 

Since the core-wide nuclear performance parameters and local power distribution within a fuel assembly depend highly on the moderator condition in LWRs, thermal-hydraulic coupled calculations have been regarded as essential in the core design procedure for thermal neutron spectrum cores. As the thermal-hydraulic 

The SRAC system is used for core design analysis of the Super FR just as it was used for the Super LWR core design (see Chap. 2). It contains many kinds of calculation modules based on integral or differential neutron transport and FDM solutions. However, the SRAC system does not contain a thermal-hydraulic calculation module for coupling. The thermal-hydraulic calculation module is coupled with the original SRAC system. 

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