抄録
This paper summarizes basic requirements for improvements of a subchannel code from the view point of a BWR fuel design. Considering recent trends of design modifications of BWR fuels, it is desirable that influences of lattice sizes, spacer geometries, a number and location of partial length rods and other coolant mixing structures to the boiling transition will be evaluated numerically. In addition, experimental databases of the boiling transition can be expanded based on the subchannel analyses so that reliability of the critical power evaluation will be enhanced. A status of NASCA's component models and high temperature/high pressure tests of the boiling transition was reviewed. From the practical point of views, it was noted that more efforts are necessary for improving predictability of spacer geometries and partial length rods.
