3-D Thermo-Mechanical Modeling of the ITER Limiter Small Scale Specimen

E. A. Mogahed and I. N. Sviatoslavsky
Fusion Technology Institute
University of Wisconsin
1500 Engineering Dr. Madison, WI 53706

This analysis describes in part, the design activity related to the small scale limiter specimen for ITER. The limiter specimen is needed to experimentally examine the possible methods of constructing and testing a prototype of the ITER limiter under near-operating conditions. Steady state heat fluxes of 3 MW/m2 are expected. A 3D finite element model has been created to represent the beryllium-copper-steel layered construction of the limiter small scale specimen. The model takes advantage of the design symmetry, such that only a quarter of the specimen has been considered. The boundary conditions are chosen to simulate the actual conditions of the entire limiter. The model consists of a 10 mm diameter, 0.5 mm thick steel liner running through a Cu block which is 2.0 cm thick made of GlidCop Al25. The center to center spacing between the coolant channels is 2.0 cm in the normal direction. The Cu block has a 1 cm thick castilated layer of Be armor facing the plasma on one side and is attached to a 5 cm thick cooled SS backing on the other. Each Cu block is separated by a 1.0 mm groove from the adjacent block leaving a 1.0 mm thick GlidCop Al25 base at the steel interface. The interface between the various layers assumes no inter-layer compositions and thus has a singularity due to different material properties. Further, the analysis is elastic, not allowing any plastic deformation. These two rather severe assumptions tend to give higher stresses at the SS/Cu/Be interface. The maximum Be temperature is 586oC at the coolant exit. The maximum Von-Misses stresses at the Cu/Be interface corners are 445 MPa. These stresses are superficially high due to the singularity at the interface and the assumption of no plastic deformation. It is proposed that any additional analysis should include the plastic deformation at the interfaces between different layers and also include an interface layer of materials to more closely simulate the actual conditions.