Transactions of the Korean Nuclear Society Spring Meeting, Jeju, Korea, May 17-18, 2012
Accurate treatment of gadolinium (Gd) depletion is one of the major issues in developing a reactor analysis code. Because of the large thermal absorption cross sections of Gd-155 and Gd-177, the depletion of gadolinium isotopes leads to a significant change in the flux distribution. The first approach to properly mitigate the strong influence of Gd in depletion calculations is to use small depletion time steps. However, this approach is not desirable particularly in direct whole core depletion calculations that require excessively long computing time. A better approach is to use a more elaborated depletion method. In this regard, a quadratic depletion method incorporating the post correction method have been proposed and proved to effective by the CASMO5 calculations. The whole core transport code developed at Seoul National University, nTRACER, adopts the quadratic depletion and post correction method and the Krylov depletion method in order to perform accurate depletion calculations for power reactors involving considerable Gd loading with sufficiently large depletion time step sizes. In this paper, the implementation of the quadratic depletion method is presented and the effectiveness of the method and the accuracy of nTRACER depletion are demonstrated with the applications to the YGN3 and UNC5 initial core depletion analyses
