Neutronic and Shielding Analyses for the DTT Electronics

Abstract

The radiation effect on electronic devices is a critical issue for nuclear facilities, accelerators, and spatial missions as well as for fusion machines. Phenomena related to particle interactions have significant impact on the normal functioning of such devices: they could arise progressively during machine lifetime due to the cumulated ionization [total ionizing dose (TID)], cumulated atomic displacement (dpa) or it can appear instantaneously after a single highly ionizing particle interaction [single-event effect (SEE)]. The divertor tokamak test (DTT) facility is a tokamak machine, which will produce, in its high-performance phase, up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.5\times 1017$ </tex-math></inline-formula> n/s at 2.45 MeV from deuterium–deuterium reactions plus about 1% of 14.1-MeV neutrons produced by the triton burn-up inside the plasma. Such significant neutron production implies a severe radiation environment, up to 1010 n/cm2/s and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times 109\,\,\gamma $ </tex-math></inline-formula> /cm2/s [secondary gammas mainly due to (n, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> ) reactions], inside Torus Hall building (THB) and outside the THB nearby the penetrations. DTT will be equipped with several power and signal electronic devices: 1) critical electronics that play a crucial role for the machine functioning in order to avoid failure, loss of plasma stability, and damages on the structural components (e.g., energy supply to the toroidal field, poloidal field, and central solenoid superconductive magnets); and 2) noncritical electronics, used to power diagnostics and systems whose failures do not compromise the machine operations, but are essential for scientific and engineering exploitation programs. Neutronics and shielding studies of electronics are fundamental for protecting the main components of the tokamak and to avoid the failure of the critical systems, as well as for the evaluation of the positioning and functioning of the noncritical devices and the selection of radiation-hard electronics. In this work, 3-D shielding studies for the DTT electronics devices, carried out with MCNP Monte Carlo code, are presented and discussed as well as the effectiveness of the proposed arrangement and mitigation solutions.