The detailed design of the International Thermonuclear Experimental Reactor (ITER) utilizes 60 divertor cassettes with vertical targets and a central dome. Knowledge of nuclear heating and radiation damage levels in the different components of the divertor cassette is essential for proper design analysis. Due to the geometrical complexity of the divertor region, three-dimensional (3-D) analyses are required.

A detailed 3-D model has been developed for the divertor cassette in the ITER detailed design. The model includes in detail the plasma facing components (PFC), the vertical targets, the wings with associated plates, the gas boxes, as well as the central dome and cassette bodies. Each divertor cassette in the model was divided into 103 regions to provide detailed spatial distribution of nuclear heating and radiation damage. The layered configurations of the dome PFC and vertical targets were modeled accurately with the front tungsten layer modeled separately. Separate regions are included in the model to represent the mechanical attachments and coolant pipe connections for the dome, vertical targets, and wings. The divertor cassette model was integrated with the general ITER model that includes detailed modeling of FW, blanket with coolant manifolds and back plates, VV, TF coils, central solenoid, and PF coils.

3-D neutronics calculations have been performed using the continuos energy MCNP-4A code with cross section data from FENDL-1 to determine the detailed spatial distribution of the nuclear parameters in the divertor cassette. The nuclear parameters were provided at the 103 cassette regions used in the model. These parameters included power density, atomic displacement and helium production. The largest heating and damage occurs in the dome PFC which has full view of the plasma. The power density in the tungsten PFC at the dome is 16.4 W/cm³. The total nuclear heating in the 60 divertor cassettes is 101.6 MW with the major contributors being the dome, vertical targets, and wings.