Tolerance Analysis Based on 3D Models for In-Wall Shielding of ITER Vacuum Vessel

Tolerance analysis is an important step in the design of a product assembly. It indicates the probable variation in the assembly response for a given set of input parameters, well in advance, right at the design stage. vacuum vessel (VV) is an important component in international thermonuclear experimental reactor to provide a high quality vacuum for plasma experiment. VV is a torus-shaped, double wall structure with shielding and cooling water between two shells (inner shell and outer shell). In-wall shielding (IWS) is used to fill the space between two shells of VV to provide neutron shield. The shield blocks are fixed by bolts to the VV ribs or blanket flexible support housings to withstand the mechanical forces. The gaps between the shield blocks and between the blocks with the ribs are minimized to avoid excessive neutron streaming. Based on the design and fabrication procedure of VV and IWS, the assembly sequence and assembly procedure of them would be studied considering the fabrication tolerance of VV sector and interface with VV sectors. Local IWS assembly tolerance analysis considering the fabrication tolerance also would be performed. This paper presents a design evaluation through tolerance analysis of assembly dimension using 3D model simulation. This approach is applicable to complex assembly function, and is quite useful in predicting the assembly precision, well in advance right at the stage of product design.