Integrated Thermofluid Analysis toward Helium Flow Path Design for an ITER Solid Breeder Blanket Module

A sophisticated numerical simulation code that couples multiple physical phenomena has become an essential tool for practical engineering design as we move forward to construct a physically complex component such as an ITER test blanket module. Such a tool can significantly reduce design uncertainties-in particular, where the flow distribution is relatively complicated and involves many parallel flow paths, as seen in a typical test blanket module design. Specifically, in a design currently proposed by the US, the helium exits the primary loop and is immediately divided into three flow paths to cool three independent submodules. This flow division is done passively, through engineering design. The helium enters the submodule and is further divided into 12 or more paths for first wall cooling and collected into 2 paths for internal breeding zone cooling. The surface heat load over an outboard test port first wall will be non-uniform and accompanied by a steady state and/or transient localized peak from MARFE (transient) and other phenomena, such as re-ionization or toroidal field ripple effects (in steady state). Moreover, the ITER test blanket module receives a higher ratio of surface heat to neutron wall load, in order to reproduce DEMO-like behavior; flow management to accommodate first wall cooling needs as well as to reproduce DEMO breeder temperature distributions adds another degree of complexity. In a previous calculation in which fluid and heat transfer phenomenon are decoupled, an extra amount of flow is injected to cool the first wall, accommodating the non-uniform surface heat flux distribution. This excess flow is then by-passed away from the breeding zone. A new analysis based on CRADLE SC/Tetra thermo fluid code has shown that this non-uniformity could potentially be smeared out through heat conduction in the lateral direction. The analysis also indicates the need to offset the helium outlet locations to reflect spatial variations in heat generation as well as to obtain uniform outlet flow distributions. A capability to simulate performance from CAD models to understand the effect of design and condition changes is indispensable, not only for design, but also to reduce unnecessary over sizing of the primary helium flow loop. This paper presents the process and how the intermediate thermo fluid analysis results guide the helium flow path design in a proposed US ITER solid breeder test blanket submodule. (author)