A macro reactivity-equivalent physical transformation method for prismatic gas-cooled reactors
Prismatic block nuclear reactor geometric homogenization is of interest in order to decrease the expense of full core calculations. The reactivity-equivalent physical transformation (RPT) method of homogenizing TRISO particle fuel regions has been proven for the rods of prismatic gas reactors as well as the pebbles of pebble bed reactor cores. After application of the RPT method, each fuel block of a prismatic gas reactor contains more than 900 different regions to explicitly model. A full core simulation of a problem of this size would simply be too computationally expensive to perform regularly. In order to perform needed calculations for these reactors, simplification of the models is a must. One option is to use a simple volume-weighted homogenization (VWH), which results in a highly underestimated reactivity for the fuel block. The goal of this research is explore methods of homogenization that will correctly predict key parameters of the problem while providing a significant decrease in the computational expense.^ The macro reactivity-equivalent transformation (MRPT) method involves geometrically homogenizing the prismatic fuel block into 7 different fuel regions while maintaining use of continuous energy cross sections in MCNP. Application of the MRPT method can decrease the steady-state computation time of a prismatic block by more than 190 times while maintaing accuracy of the multiplication factor as well as principal reaction rates. The MRPT method is also assessed for burnup calculations for different fuels such as uranium oxycarbide, uranium dioxide, and uranium/thorium fuels. ^
Chan Choi, Purdue University.