To evaluate the characteristics of various passive safety concepts and provide the proper technical data for the conceptual design of the advanced integral reactor, the following R&D activities are being performed.

Hexagonal Semi-Tight Lattice Fuel Assembly

Numerical Analysis Technology is being development to analyze the hexagonal fuel assembly core with tight lattice. Some thermal-hydraulic experiments will be performed to understand the phenomena in the semi tight hexagonal lattice. The suitable thermal-hydraulic analytic model will be developed, especially thermal-hydraulic correlations, which are vital for the semi-tight hexagonal geometry. The developed model is incorporated into computer codes for the design and safety analysis.

No Boron Core Concept

The use of no soluble boron in the core design causes to utilize large amount of burnable absorbers to properly hold down the excess reactivity at the beginning of cycle and to install considerable number of control rods for the reactor control and operation. The optimization in the number of burnable absorbers and control rods is required with respect to the reactivity compensation with fuel bumup and reactor control through the cycle, and this study in conjuntion with the core design with hexagonal fuel assemblies are thus investigated in this R&D subject.

Natural Circulation Phenomena for Integral Reactor

To investigate thermo-hydraulic characteristics of primary circuit in natural circulation operation mode, an experimental test loop is being designed. An computer code is being developed to model the thermo-hydraulic behavior of the primary circuit.