7. UNUSUAL FEATURES OF THE PROGRAM
The only moderator considered is heavy water.
Xenon is assumed to be in equilibrium during the burn-up process.
Reflector and moderator are assumed to have the same macroscopic neutron cross-sections.
Spatial Xenon and temperature distributions within the reactor core are not considered.
The channels of the reactor are treated as line sources and line sinks for neutrons. Thus, their finite size is not taken into account. As a consequence, the channels must not be too large nor too closely packed within the moderator.
The programme does not take into account the condition that the fast flux vanishes at the extrapolated boundary of the radial reflector.The error thereby introduced is negligible if the radial reflector is greater or equal to 4*SQRT(tau), where tau is the slowing down area of the moderator.
The slowing down properties of the materials within the channel are not treated separately but must be included in a suitable way by modifying the slowing down properties of the moderator.