Final report of shielding calculations performed at ECN Petten for ITER CTA task D4/EU

In this report the final results are presented of neutronics calculations performed at ECN Petten in the framework of ITER task D4. It is shown, that self-shielding in the unresolved resonance region, which is not taken into account in MCNP, will increase the fast neutron flux in ITER shielding blanket calculations with at least 10%. A method is presented, with which an approximate calculation of the effect is possible. It is observed, that homogenisation of stainless steel and water in neutronics calculations is not allowed for accurate calculations. Calculations were performed with several sources of cross section data (EFF-1, EFF-2.4 and FENDL-1.0). It is shown, that systematic differences occur between the results from different calculations. However, a fair agreement is observed if results of EFF-2.4 and FENDL-1.0 calculations are compared. Sensitivity and uncertainty studies show, that the uncertainty in the energy integrated flux in a relevant energy range amounts to 15%. This uncertainty is mainly due to uncertainties in the total cross section and the elastic angular distribution of Fe. (orig.)