Core Modification to Improve the Irradiation Efficiency and Increase the Core Burn-up of the Experimental Fast Reactor Joyo

摘要

Core modification was investigated to further increase the core burn-up of the experimental fast reactor Joyo. This modification also enables the core to accommodate more irradiation test subassemblies that have lower fissile material content compared to the driver fuel. The design calculations showed that the replacement of the radial reflector elements made of stainless steel with those made of zirconium is effective in improving neutron efficiency. The core reactivity can be increased by reducing the number of control rods based on the re-evaluation of the design margin in the control rod worth calculation. These.modifications will be useful to save driver fuels and to enhance the Joyo's irradiation capability. The detailed core design and the items necessary to obtain the new license are now underway.