Use of CAD generated geometry data in Monte Carlo transport calculations for ITER

Fischer, U.*; Iida, Hiromasa; Li, Y.*; Loughlin, M.*; Sato, Satoshi; Serikov, A.*; Tsige-Tamirat, H.*; Tautges, T.*; Wilson, P. P.*; Wu, Y.*

Several approaches have been recently developed to make available CAD geometry data for Monte Carlo calculations with the MCNP code. Among these are conversion tools for the automatic generation of geometry models in MCNP representation such as MCAM of China, McCad of Germany, and GEOMIT of JAEA, as well as the direct DAG-MCNPX approach developed by USA. An extensive benchmark exercise has been conducted on ITER between 2005 and 2007 with the objective to test and validate the different approaches and thereby check the maturity level for ITER design applications. The exercise encompassed the generation of a dedicated neutronics CATIA model based on available engineering CAD design data, the conversion into MCNP geometry, the verification of the converted models, and a number of calculations to compare the different approaches with regard to the performance and the validity of the results obtained. The paper briefly reviews the different approaches and provides a detailed description of the ITER benchmark effort, its results and conclusions. As a key issue, the recommendations are discussed that need to be followed when generating a neutronics CAD model for ITER design calculations. This is considered essential since the ITER quality assurance requirements will request the consistency of the analysis models and the underlying engineering CAD models.