WIMS-D4M user manual

The Winfrith Improved Multigroup Scheme (WIMS) code has been used extensively throughout the world for power and research reactor lattice physics analysis. There are many WIMS versions currently in use. The D4 version selected by the RERTR program was originally developed in 1980). It was chosen for the accurate lattice physics capability and an unrestricted distribution privilege. The code and its 69-group library tape 166259 generated in Winfrith were obtained from the Oak Ridge National Laboratory Radiation Shielding Information Center (RSIC) in 1992. Since that time the RERTR program has added three important features. The first was the capability to generate up to 20 broad-group bumup-dependent macroscopic or microscopic ISOTXS cross sections for each composition of the unit cell, a new ENDF/B-V based nuclear data library, and a new Supercell option. As a result of these modifications and other minor ones, the code is now named WIMS-D4M. A supplementary reference guide can be obtained from the RSIC that contains detailed explanations of all user options, library contents, along with several sample problems. Primary applications of WIMS for research reactor modeling do not require an extensive knowledge of all WIMS user options. This user guide is primarily addressed to the needs of the research reactor community although the code can be used for most thermal reactor lattices. The guide is written based on the experience of the RERTR staff with WIMS-D4M and will discuss only the most needed options for research reactor analyses