Process of Homogenization and the Lattice-Parameters of a Sub-Critical Assembly

抄録

The systematic variation of lattice parameters as a function of fuel-moderator ratio in a subcritical assembly (natural uranium, graphite moderated) has been investigated. Diffusion theory was used for correlation of results. The theoretical results were calculated according to the procedure laid down for graphite-moderated reactors based on the unit-cell concept of Wigner-Seitz. The results show that the method (Wigner-Seitz) predicts accurate results even when a fuel element is assumed to be spread over two lattices uniformly. This also proves the method of replacing a square lattice by an equivalent cylindrical one. The effect of voids (gas channels) on the lattice-parameters was also considered.