Neutronic Modeling Challenges for the ITER ECRH Launcher Shielding Design

Comprehensive neutronic analyses are being performed for different variants of the International Thermonuclear Experimental Reactor (ITER) electron cyclotron resonance heating upper launcher under development in the European Union making use of modern computation tools such as the McCad code for geometry conversion and the rigorous two-step (R2S) interface for rigorous shutdown dose rate calculation. There were many reasons for the challenges encountered during the shielding analyses: deep-penetrated radiation transport in the complex geometry of the launcher, frequent need to introduce changes in the three-dimensional MCNP model, and necessity to meet a broad range of nuclear sufficiency requirements specified for ITER. The challenges were successfully addressed and resulted in radiation shielding and nuclear safety support for the current version of the launcher design, which should be workable in ITER. During the process of the launcher design development, a comprehensive knowledge of neutronic characteristics has been gained, and computation methods were matured accordingly.