RADIATION STREAMING IN GAPS BETWEEN ITER FIRST WALL/SHIELD MODULES

摘要

Gaps exist between the first wall/shield (FWS) modules of ITER to allow for fitting by remote handling equipment. Simplified three-dimensional models were used at the top and mid-plane locations to analyze gap streaming. Heating, helium production, and fast neutron fluence were examined at the front of the vacuum vessel and the magnet for both straight and stepped gaps. In addition, total nuclear heating values in the inboard magnet and central solenoid were examined for straight and stepped vertical gaps and for combined horizontal and vertical straight gaps. The results show significant radiation streaming effects that are more pronounced for fast neutron fluence and helium production. Furthermore, it was found that stepping the gap significantly reduces the local peaking, but has little effect on the relative average values of radiation effects. The results also show increases up to 75% in total magnet heating at the inboard mid-plane location for a straight 2 cm combined vertical and horizontal gap .