Deterministic lattice code development at UNIST

A new method of characteristics code, STREAM, has been developed at Ulsan National Institute of Science and Technology (UNIST). With regard to a resonance treatment in STREAM, the gray resonance treatment method and doubly heterogeneous self-shielding method were implemented based on the equivalence theory. STREAM can calculate eigenvalue and pin power distribution of a two-dimensional multi-assembly with CMFD acceleration. In this paper, designed pin cell and two-dimensional C5G7 benchmark problems were solved to verify the STREAM library and solver, respectively. As a practical problem, the VENUS-2 benchmark from research reactor experiments was calculated up to assembly level by the STREAM code. To check applicability of STREAM to new fuel analysis for a boron free reactor, innovative fuel problems were designed and calculated. STREAM solutions of these problems were compared with the Monte Carlo reference solutions, and showed a good agreement with them on a similar level. (author)