group diffusion method

group diffusion method

[′grüp di¦fyü·zhən ‚meth·əd]
(nucleonics)
An approximation used in studying the diffusion of neutrons in a nuclear reactor, in which the range of neutron energies, from source energy to thermal energy, is divided into a finite number of intervals, or groups, and the neutrons in each group are assumed to diffuse with no loss of energy, until they have undergone the average number of collisions needed to reduce their energy to that of the next lower group.