A simplified calculation model of the recoil and irradiation enhanced diffusion which occur in neutron activation analysis
of metals is proposed. Under usual irradiation conditions, the recoil does not exceed 0.01 μm for n, γ reactions and 2 μm
for other reactions; the diffusion does not exceed 1 μm. Examples, in which deep impurity diffusion leading to important analytical
errors was put forward, are discussed through this calculation model. In most cases, the observed phenomena are not related
to diffusion but to other causes such as unefficient etching of the sample surface.