2.0 Reactor Core and Fuel Design

Table 1 gives the basic reactor parameters. The fuel design is based on existing KOFA (Korean Optimized Fuel Assembly) design technology. Most design parameters of fuel rods are the same as those of the KOFA except geometrical arrangement which is changed from the square array to hexagonal array. The hexagonal fuel assembly yields the lower moderator to fuel volume ratio(Vm/Vt) and the hardened neutron spectrum which results in stronger

moderator temperature coefficients and higher plutonium conversion ratio. The effective fuel rod length is reduced to 180cm. Fuel utilizes low enrichment, uranium dioxide, which is operated at a low specific power density(17 kW/kgUCb). The uranium enrichment of the fuel is selected to achieve the 18 months(or longer) operating cycle. The fuel assembly section is a 22.9cm hexagon and the geometry is provided to accommodate control element assembly in each fuel assembly. The fuel assembly consists of 360 fuel rods and 36 guide tubes for control absorbers and/or insertable burnable absorbers and 1 guide tube for central in-core instrument.

The core is rated at 300MWt and consists of 55 fuel assemblies. The average linear heat generation rate is 8.4kW/m which is much lower than that of conventional PWRs. The low power density and increased thermal margins with regard to critical heat flux ensure the core thermal reliability under normal operation and accident conditions. The core is designed to operate without the need for reactivity’ control using soluble boron over the whole power range. The elimination of soluble boron from the primary coolant is a major potential simplification for the advanced light water reactor. From the point of the view of the reactor control and safety, soluble boron free operation offers potential benefits through the presence of a strong negative moderator temperature coefficient over the entire fuel cycle and therefore improves reactor transients and load follow performance. Control rods provide the means of core reactivity control except for long term reactivity compensation for fuel depletion provided by the burnable poison and have enough shut down margin at any time under cold clean conditions including refueling conditions.

Primary Circuit