European studies on fast reactor core interwrapper flows

The core of a fast reactor is formed with the assemblies of fuel pins contained within hexagonal wrapper tubes. The gaps of a few millimeter between the adjacent faces of the triangularly pitched wrapper tubes form a complex network of passages connected with the hot pool. In many designs of fast reactors, radial pressure gradient is generated at the subassembly exit plane by the interaction of subassembly outlet flow with the above core structure. The state of flow is described briefly. In the EFR design, the flow pattern in the hot pool, required by the compact design, is controlled by the details of the above core structure which generates a pressure gradient large enough to support significant interwrapper flow. In this paper, the aspects of the current work on interwrapper flow in the EFR project are reported, which is presenting the typical results from the experimental and theoretical programs. The HIPPO model is the scale model of the core and hot pool region of the Superphenix 2 design of a fast reactor system. The experiment on it and the results, the calculation of interwrapper flow, the translation of water results to sodium and so on are reported. (K.I.)