Energy self-shielding and SED/SAD effects in sensitivity calculations of a NET shielding blanket

The results are presented of a sensitivity and uncertainty analysis of a NET iron/water inboard shielding blanket using energy self-shielded cross sections. Coupled (n, γ) transport calculations were performed in an S8P3 approximation using cross sections derived from the European Fusion File in the 121-group GAM-II structure. Energy self-shielding was taken into account using the Bondarenko method. The results of this analysis are compared with a similar analysis in which infinite dilute cross sections were used. It is shown that the effect of energy self-shielding on the neutron flux in the coils of the NET design is considerable, whereas the γ-flux is hardly influenced at all. This causes the nuclear heating in the inboard coils to be increased by 13%. The relative uncertainty in the nuclear heating due to uncertainties in the total cross sections of Fe, Cr and Ni decreases by 8% when self-shielding is taken into account. In addition, the effects of uncertainties in the energy and angular distributions of the scattered neutrons (SED and SAD respectively) were studied. SED uncertainties appear to have only a minor effect. SAD uncertainties, however, are quite important for elastic scattering. It is therefore concluded that more attention should be paid to these SAD uncertainties. (orig.)