Neutronics analysis of the international thermonuclear experimental reactor (ITER) MCNP “Benchmark CAD Model” with the ATTILA discrete ordinance code

There is currently extensive effort to develop and benchmark new codes to supplement the accepted computational tools for the nuclear design of ITER. The ITER management and quality program (MQP) officially requested benchmarking the newly developed FEM 3D, discrete ordinates code, ATTILA, to the results obtained by the CAD-based MCNP Monte Carlo codes. CAD-based computational tools are needed to reduce the turnaround time between changes in design and the subsequent nuclear analysis to key design parameters in an iterative process. There is currently extensive effort to develop and use a CAD–MCNP interface for design purposes to facilitate the modeling and analyses. ATTILA uses CAD-based geometrical input and as such it is a potentially quicker alternative to the MCNP code for the neutronics studies contingent on its success in predicting key neutronics parameters in large systems such as ITER. The ITER neutronics community had agreed to use a standard CAD model of ITER (40° sector, denoted as“Benchmark CAD Model”) to compare results for several responses selected for calculation benchmarking purposes to test the efficiency and accuracy of the CAD–MCNP approach developed by each ITER party in addition to ATTILA. In this paper we report such comparison to the results of the CAD-based MCNP developed at the University of Wisconsin for five selected nuclear responses. It is shown that ATTILA's results are within 25–30% of the MCNP results.