3. Modeling Instructions

 
Using the specifications given in Section 2, two-dimensional calculations are to be performed to provide key quantities given in Section 4 at the reactor midplane. The assembly is assumed to be in an infinite array of similar assemblies such that reflective boundary conditions can be used. Also note that the assembly geometry is symmetric such that only 1/4 or 1/8 assembly need be modeled. In the two-dimensional calculations the buckling height is taken to be that of the active height of the fuel (365.76 cm).

The assembly power is 17.5 MW and is assumed to be constant over the entire irradiation period. The pin power distribution will be represented by the calculation of the pin fission density distribution. In the cold zero-power (CZP) condition, all temperatures are 300 K. In the hot zero-power (HZP) condition, all temperatures are 570 K. In the hot full-power (HFP) condition, the average fuel temperature is 1100 K, the clad temperature is 620 K, and the coolant temperature is 570 K . In the HFP condition, equilibrium xenon effects are included and the soluble boron concentration is reduced to offset some of the reactivity loss from the xenon. The guide tubes and burnable poison rods have the same temperature as the coolant in all conditions.

 For Monte Carlo calculations of the BOL cases at HFP the xenon concentrations should be obtained from the methods employed for the burnup calculations. However, since ORNL will be providing fission product inventories for the Russian calculations, equilibrium xenon concentrations will also be provided for the BOL HFP cases.