Analysis of the F-lattice Using Scale and Mcnp5 by Steven

The current resurgence of interest in the nuclear power industry has led to renewed interest in new reactor designs. The GE Compact Modular Boiling Water Reactor (CM-BWR) is one such reactor. The 350 MWe CM-BWR is designed for small incremental additions to the power grid. A key feature of the CM-BWR is the use of the unique F-Lattice. The F-Lattice employs a staggered row configuration for the control blades. Additionally, the control blades are more than double the width of control blades found in most commercial boiling water reactors today. Increase in blade width and pitch allows for approximately a one-half factor decrease in the number of control blades. Reduction in control blades results in a large reduction in control rod related components. This reduces construction and maintenance costs, as well as reducing the risk of failures within the core. However, before design certification can be completed for the CM-BWR, first the tools needed to design and monitor reactor core performance must be validated. In this thesis, two versions of the SCALE package are validated to accurately model the F-Lattice by comparing their results against MCNP5 benchmark results. Multiplication factor and flux distribution are compared. The techniques necessary to iii analyze the flux calculations on a spatial grid were developed for the SCALE output. To compare flux distributions it was necessary to process the SCALE output and generate flux distributions in the same units as those employed in MCNP. A code is written in Perl to accomplish this task. Limitations of the supplement code, as well as limitations of the SCALE packages are discussed in detail. In addition, parametric studies are performed to determine rod worth and the effect of small and large perturbations to the geometry. Results are obtained for variation in material properties and change in control blade thickness. Suggestions for future work are given. iv Acknowledgments