Broader Approach

The aim of the Broader Approach agreement, signed in Feb. 2007 between Euratom and Japan, is “complement the ITER Project and to accelerate the realisation of fusion energy by carrying out R&D and developing some advanced technologies for future demonstration fusion power reactors (DEMO)” [1]. As for ITER, F4E is the Implementing Agency of Euratom for the Broader Approach. The resources for the implementation of the Broader Approach are largely provided on a voluntary basis from several participating European countries (Belgium, France, Germany, Italy, Spain and Switzerland).

Among the three main projects being implemented, our research group is involved in the design of the International Fusion Materials Irradiation Facility (IFMIF). The purpose of IFMIF is test and qualify materials that can be operated at high temperatures and under intense (neutron) radiation, conditions typical of nuclear fusion devices. In IFMIF, the material samples will be exposed to an intense neutron flux created by bombarding a liquid lithium flow by a dual deuterium beam (see adjacent figure) . A high speed liquid lithium flow is required to rapidly and continuously evacuate the heat deposited by the two deuterium beams.

At Université Libre de Bruxelles, we focus our attention on the evaluation of the stability of the free surface lithium flow by means of Computational Fluid Dynamics (CFD). Indeed, a safe and reproducible operation of the 25mm thick lithium target requires that its surface should not present irregularities larger than +/- 1mm in the range of parameters envisaged for nominal flow conditions. Our simulations are performed using two solvers. The first one is a finite volume code called YALES2 [2] capable of achieving high resolution computations on massively parallel clusters. This solver is based on the large-eddy simulation technique and makes used of the volume of fluid (VOF) method coupled to the level-set method. The second solver used is Ansys Fluent [3] which allows the computation of free surface flows using a variety of methods including large-eddy simulations or Reynolds Average Navier-Stokes simulations.