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The Divertor Tokamak Test (DTT) facility is a project proposed by an Italian consortium aimed to test the physics and technology of various alternative divertor concepts in order to design a heat and power exhaust system able to withstand the large loads expected in the divertor of a DEMO fusion power plant. The DTT machine is expected to produce up to 1.0 × 1017 2.5-MeV neutrons per second through deuterium-deuterium (DD) reactions with a significant 14 MeV neutron production (1% of the total yield) due to triton burn-up during the high-performance phase. This work is devoted to a preliminary three-dimensional shielding study to optimize the DTT building for licensing purposes. Neutron and gamma transport simulations were carried-out with MCNP5 Monte Carlo code using weight windows generated with ADVANTG hybrid code. Three-dimensional model of the DTT machine and building has been developed to assess the spatial distributions of the neutron and gamma fluxes, spectra and effective doses inside and outside the tokamak hall. The wall thickness (in the range 150–250 cm) has no impact on satisfying dose limits for the public, but is important when satisfying limits for workers.

In order to prevent the overheating of the liquid Li surface and the consequent Li evaporation for T > 500°C, an advanced version of the liquid lithium limiter has been realized and installed on FTU. This new system, named Cooled Lithium Limiter (CLL), has been optimized to demonstrate the lithium limiter capability to sustain thermal loads as high as 10 MW/m2 with up to 5 s of plasma pulse duration. The CLL operates with an actively cooled system with water circulation at the temperature of about 200°C, for heating lithium up to the melting point and for the heat removal during the plasma discharges. To characterize CLL during discharges, a fast infrared camera and the spectroscopic signals from Li and D atom emission have been used. The experiments analyzed so far and simulated by ANSYS code, point out that heat loads as high as 2 MW/m2 for 1.5 s have been withstood without problems. © 2014 Elsevier B.V.