Practical numerical reactor employing direct whole core neutron transport and subchannel thermal/hydraulic solvers

The development and verification of a practical numerical reactor formed by integrating a subchannel thermal/hydraulic solver into the nTRACER direct whole core transport code developed at Seoul National University are presented. In order to accomplish high-fidelity and practicality needed for the applications to routine design analyses of power reactors, the accuracy and the parallel computing efficiency of the direct whole core transport methods, which are characterized by the planar MOC solution based three-dimensional calculation method, the subgroup method for resonance treatment under non-uniform conditions and the Krylov subspace based depletion method, are improved and realistic modeling features such as axial spacer grid modeling and burnup-dependent gap conductance are implemented. The accuracy of the nTRACER neutronics calculations is first verified by comparing its solution with the reference Monte Carlo solutions for a group of benchmark problems. Then the core follow calculation results of the practical numerical reactor for two pressurized water reactors are compared with the measured data such as the critical boron concentration and radial power distributions. From these performance examinations, it is demonstrated that accurate and detailed direct simulations of power reactors is practically realizable without any prior calculations or adjustments before the core calculation.