Effect of polynomial expansion order of intranode flux treatment in nodal S transport calculation code NSHEX for large-size fast power reactor core analysis

Sugino, Kazuteru; Kugo, Teruhiko 

The nodal discrete ordinates (S) transport calculation code for three-dimensional hexagonal geometry NSHEX treats intra-node flux distribution by polynomial series and considers angular dependence of flux by the S method. For the improvement of calculation accuracy of NSHEX for the practical use to large-size fast reactor plants, the maximum order of polynomial series is extend from two to six. In order to check the effect of the polynomial expansion order, NSHEX is applied to the middle-size fast power reactor core "Monju" and the large-size one "Super Phenix" including various control rod insertion conditions. From the application, it is found that extension of polynomial expansion order is effective especially for the large-size core "Super Phenix" with control rod inserted condition.