MURLI-CLUSTER, Lattice Calculation of PHWR with Rod Clustered Fuel

1 - Description of program or function: MURLI-CLUSTER is an integral transport theory code to obtain the physics characteristics (fluxes, reaction rates, etc.) of PHWR lattices which use rod clustered fuel assemblies. The actual cell is replaced by an equivalent cylindrical cell for the purpose of computation of fluxes. For a specified buckling, it computes the effective multiplication factor using few-group diffusion theory and a few-group collapsed set of Cross sections. The code can optionally be used to obtain the number densities of fissile, fertile and fission product Nuclides as a function of exposure and to recalculate fluxes, reaction rates and k-effective at specified burnup steps. A 27-group library is included. It is obtained by collapsing the 69-group WIMS library over a typical PHWR lattice spectrum. There are four pseudo fission products associated with the decay chains of uranium and plutonium in addition to Xe-135, Rh-105, Np-239, U-236, Am-241, Am-242, and Am-243. There is one lumped pseudo fission production also. 2 - Method of solution: The cluster is homogenized ring-wise and then the interface current formalism is used to obtain the fluxes by integral transport theory. However, the heterogeneity corrections in the fast and resonance regions are obtained by exact collision probability calculation in explicit cluster geometry. The burnup equations are solved by either fourth-order Runge-Kutta method or the trapezoidal rule. 3 - Restrictions on the complexity of the problem: There is a maximum of 40 elements that can be used, out of which there can be up to 8 fissionable and/or resonant elements; one can use up to 30 spatial regions and 8 different material mixtures, with a maximum of 5 burnable mixtures