For two typical LWR fuel rod irradiation devices introduced into the BR2 reflector two-dimensional neutron and gamma calculations are being carried out.

In the first case a single fuel rod surrounded by several pressure tubes and by a time-variable neutron screen (He⁻³ gas at various pressures) is studied. The calculations are carried out in R,θ geometry, centered on the irradiated fuel rod.

In the second case a bundle of nine fuel rods in a 3×3 square lattice is irradiated. Here the calculations are performed in X,Y geometry.

The necessity is discussed of performing two-dimensional calculations for these irradiations in the BR2 reflector, to improve the modelling of the fuel behaviour.