The question of neutronics or reactor physics methods has come up at various times and with respect to different aspects. I thought it would be worthwhile to explore various methods, the technology and their applications. Broadly, reactor physics calculations involve solving equations related to neutron transport or diffusion in the complex reactor geometry. The calculations are represented by a system of coupled nonlinear partial differential equations, and particularly partial integro-differential equations (or integro-partial-differential equations). Some methods, e.g., MC or Sn methods are only appropriate for limited applications such as criticality or a time-specific statepoint in a calculation. For depletion calculations, deterministic methods are more appropriate. https://en.wikipedia.org/wiki/Neutron_transport https://en.wikipedia.org/wiki/Method_of_characteristics MIT's OpenMOC Method of Characteristics Code should be of interest - https://mit-crpg.github.io/OpenMOC/ The choice of method depends on application. I've posted some links to get started, but I plan to elaborate more on the subject.