[en] Genetic Algorithm (GA) based systems are used for the loading pattern optimization. The use of Genetic Algorithm operators such as regional crossover, crossover and mutation, and selection of initial population size for PWRs are discussed. Antithetic variates are used to generate the initial population. The performance of GA with antithetic variates is compared to traditional GA. The results of multi-cycle optimization are discussed for objective function taking into account cycle burn-up and discharge burn-up

[en] We present a simple methodology for reducing the extent of the search space of the modular optimization code package developed for the size and shape optimization of the beam tube assembly at the Penn State Breazeale Reactor (PSBR). In this method, we express the origin of the neutron output at the beam tube exit in two components depending on the location of their last scattering collision in (i) the Bi gamma shield; or (ii) the moderator (e.g. H₂O or D₂O) illuminating the beam tube. We compute the contribution of these two components to the neutron flux at the beam tube exit by performing numerical experiments using the three-dimensional particle transport code TORT on a model configuration. We illustrate the results of this approach with various moderator materials, comparing the strength and spectrum of the outgoing neutron beam, and indicating how those affect the search space size. Results demonstrate that the neutrons originating at the beam tube base contribute more output neutrons at the beam tube exit than neutrons from all other origination locations. Hence, this result enables defining a small search space, thus reducing the optimization procedure's computational time. (authors)

[en] SCALE is a widely used suite of tools for nuclear systems modeling and simulation that provides comprehensive, verified and validated, user-friendly capabilities for criticality safety, reactor physics, radiation shielding, and sensitivity and uncertainty analysis. Since 1980, regulators, industry, and research institutions around the world have relied on SCALE for nuclear safety analysis and design. SCALE 6.2 provides several new capabilities and significant improvements in many existing features for criticality safety analysis. Enhancements are realized for nuclear data; multigroup resonance self-shielding; continuous-energy Monte Carlo analysis for sensitivity/uncertainty analysis, radiation shielding, and depletion; and graphical user interfaces. An overview of these capabilities is provided in this paper, and additional details are provided in several companion papers. (authors)