J.P. Catalan

Development of the R2SUNED Code System for Shutdown Dose Rate Calculations

R2SUNED is a code system implementing the mesh-based Rigorous-two-step method for shutdown dose rates calculations, making use of MCNP and ACAB codes. In addition to the most relevant features of state-of-the-art R2S systems, novel and unique features have been implemented in R2SUNED to overcome limitations common to the current mesh-based R2S implementations. One of particular interest is the cell-under-voxel approach intended to address most of the issues associated with the conventional averaging technique used in the neutron flux determination. The underlying idea is to identify the cells enclosed in each voxel and calculate the average value of the neutron flux within each cell fraction. Subsequently, the activation of each material, filling the cell delimited by the voxel, is calculated using the neutron flux evaluated in the corresponding cell. This capability enables to properly resolve the strong spatial gradients of the neutron flux independently of geometrical considerations. Another relevant feature is that a flexible decay gamma source sampling has been incorporated to assure an efficient decay gamma transport in a vast diversity of problems. A verification of R2SUNED has been addressed on the ITER computational shutdown dose rate benchmark. It is highlighted both the limitations of voxel averaged neutron flux standard approach, and the ability of R2SUNED to overcome this issue. The excellent agreement of the results with those obtained using a mesh matching perfectly the geometry tells that R2SUNED performs correctly. Finally, a description of the most representative applications carried out with R2SUNED is provided for fusion relevant facilities.

Activation Analysis for a He/LiPb dual Coolant Blanket for DEMO Reactor

Abstract The objective of the Spanish national project TECNO_FUS is to generate a conceptual design of a DCLL (Dual-Coolant Lithium-Lead) blanket for the DEMO fusion reactor. The dually-cooled breeding zone is composed of He/Pb-15.7 6Li and SiC as liquid metal flow channel inserts. Structural materials are ferritic-martensitic steel (Eurofer-97) for the blanket and austenitic steel (316LN) for the Vacuum Vessel (VV). The goal of this work is to analyze the radioactive waste production by the neutron-induced activation and the back-end of the blanket and the VV (SS316LN) materials (Eurofer, SiC, LiPb, and SS316LN). Furthermore, the radioactive waste production in the cryostat (SS316LN) and the bioshielding (concrete) has been estimated. Following the current approach to the back-end of the materials in fusion facilities, the radioactive waste has been subdivided according to the activity-level classification (EW, exempted waste, LILW, low and intermediate level waste, and HLW, high level waste) and according to the radiological complexity of operations (handling and cooling). The activation calculations have been carried out with the ACAB code.

Neutronic Assessment of Candidate Materials for TF Coils Shielding in a DEMO Fusion Reactor Based on a DCLL Blanket

Abstract Under the Spanish Breeding Blanket Technology Program TECNO_FUS, a conceptual design of a dual-coolant lithium-lead (DCLL) blanket for DEMO is being revisited. In this work, different shielding candidate materials are assessed in their ability to satisfy the radiation load requirements that must be fulfilled in the toroidal field (TF) coils: absorbed dose in the insulator (Epoxy), peak fast neutron fluence in the superconductor (Nb3Sn), peak nuclear heating in the winding pack and maximum neutron fluence in the cooper stabilizer. Furthermore, the impact of the material choice on waste management requirements of both shielding and vacuum vessel (VV) materials is evaluated, and the performance of candidate materials is examined in terms of the helium production in the VV SS316LN material and its implications in reweldability. Materials discussed for the High Temperature Shield are Eurofer, graphite, B4C, WC and WB4C, while the metal hydrides ZrH2, Zr(BH4)4, and TiH2 are discussed for the Low Temperature Shield. In the case of DEMO irradiation scenario, all the analyzed material combinations fulfill the design requirements for the waste management of the shield and VV, He production in the VV wall and TF coils radiation loads requirements.