Development of design window evaluation and display system. 2. Confirmations of the basic performance of genetic algorithm

A large- scale sodium-cooled fast breeder reactor in feasibility studies on commercialized fast reactors which has a tendency of consideration of through simplified and compacted system is being investigated, however special attention should be paid to thermohydraulic designs for a gas entrainment behavior from free surfaces, a flow-induced vibration of in-vessel components, a thermal shock for various structures due to high-speed coolant flows, nonsymmetrical coolant flows, etc. in the reactor vessel. As thus a lot of thermal-hydraulic issues relate to each other complicatedly on the reactor designs, multiple-criteria decision-making on the understanding of relationship among thermal-hydraulic issues is indispensable to design the reactor efficiently. Genetic Algorithm (GA), which is one of the methods for multiple-criteria decision-making, was applied to the typical simple objective optimization problems and then was confirmed its basic performance. From the analyses, the following results have been obtained. (1) In the unimodal optimization problem, it was confirmed that GA is capable of sufficient searching ability. (2) It was confirmed that GA can be also applied to the discrete optimization problems. (3) In the case of applying GA to the combinational optimization problem, the searching efficiency is improved better by increasing the number of experiment times than the maximum of generation. (4) In the case of applying Ga to the multimodal optimization problem, the searching ability is improved by using the two genetic operators (I.e., the mutation, and the elite strategy) at the same time. (author)