Fusion Science and Technology / Volume 56 / Number 1 / July 2009 / Pages 57-62
ITER / Eighteenth Topical Meeting on the Technology of Fusion Energy (Part 1)
Radiation shielding, thermal protection, and energy removal for ITER are provided by an array of firstwall/shield modules (FWS). Nuclear analysis of the shield modules is important for understanding their performance and lifetime in the system. Using Direct Accelerated Geometry (DAG)-MCNPX, a coupling of traditional MCNPX with the Common Geometry Module (CGM) and the Mesh Oriented dAtaBase (MOAB) developed at UW, high-fidelity 3-D neutronics analysis is now possible. Particles are transported in the CAD geometry reducing analysis time, eliminating input error, and preserving geometric detail. The surface source read-write capability that exists in MCNPX has been used in DAG-MCNPX to combine realistic source conditions with an efficient analysis model. A surface source was written using a 3-D model of ITER with a detailed plasma source. The surface source was then used in a detailed 3-D CAD model of Module 13.3-D high fidelity mesh tallies were used to calculate nuclear heating used in thermal-hydraulics analysis. Surface source results were compared against results using a hybrid 1-D/3-D approach in which a uniform neutron source is extended infinitely in the vertical direction. Results show that the hybrid source overestimated the total number and under estimated the average energy of particles incident on the FW. The hybrid approach was found to overestimate the nuclear heating at the front of the first wall by as much as 63%.