Shielding design and neutronics calculation of the GDT based fusion neutron source ALIANCE

摘要

This paper presents the high flux neutron shielding design and extensive neutronics calculations of GDT based fusion neutron source ALIANCE. Neutron distribution of ALIANCE is strongly inhomogeneous along the axis: significant portion of the neutron flux is generated near the two mirrors, while the rest of it is spread over the remaining central volume of plasma. The shielding design includes 40 cm stainless steel as the main shielding layer and an additional 5 cm tungsten carbide shielding layer at mirror plugs to protect superconducting coils from neutron damage and reduce nuclear heating. The simulations have been carried out by using Monte Carlo transport code SuperMC with nuclear data library FENDL 3.1. Results show that the nuclear heating on the mirror coils can be reduced by more than two thirds with additional tungsten carbide shield, and fast neutron fluence by 30 %. The highest nuclear heating and the highest fast neutron fluence zones are located at the mirror coils, and the values are about 300 W/m(3) and 9 x 10(18) n/cm(2) respectively, which meets the threshold of ITER superconducting coils. The specific activities of shielding layers are of order of 10(12) Bq/kg. The structural materials? specific activities will decrease to 4 x 10(11) Bq/kg in one year after shutdown, and their decay heat will quickly drop below 2 kW/m(3) after one day. Besides, all the structural materials of ALIANCE can be recycled by different recycling technologies. The modeling and calculations reported in this paper will be beneficial for the pre-conceptual engineering design of ALIANCE.