A highly efficient numerical technique for solving multigroup
neutron diffusion equations in nuclear reactor physics.
About the NEM Code
RDFMG's NEM code utilises the Nodal Expansion Method (NEM), a highly efficient numerical technique used in nuclear reactor physics to solve the multigroup neutron diffusion equations. By using coarse spatial meshes (typically the size of a fuel assembly, ≈ 20 cm), NEM drastically reduces computational costs and unknowns compared to traditional fine-mesh finite difference methods.
NEM transforms multi-dimensional diffusion problems into one-dimensional equations per spatial direction via transverse-integration. The intra-nodal neutron flux is then approximated using higher-order polynomial expansions (often up to fourth-order). This allows the code to capture complex flux shapes and accurately predict power distributions within a reactor core.
Key Features
- Coarse-mesh efficiency — Assembly-sized spatial meshes (~20 cm) for fast computation
- Higher-order polynomial expansions — Up to fourth-order accuracy for complex flux shapes
- Transverse-integration procedure — Reduces multi-dimensional problems to 1D per direction
- Multigroup capability — Solves multigroup neutron diffusion equations
- Accurate power distributions — Reliable predictions for core analysis and design
Get Involved with NEM
Interested in using NEM for your research or reactor analysis work? The code is available through RDFMG's code distribution program. Contact us to learn about access requirements, licensing, and collaboration opportunities.