Helium Production Due to Neutron Streaming Through Small Circular Ducts in a Fusion Reactor Blanket by Analytical Fitting from Monte Carlo Calculation Results

The neutron streaming through a small circular duct in a shielding blanket module in the deuterium-tritium (DT) fusion reactor was evaluated, and the helium production at a plug of the cooling water branch pipe was calculated by a three-dimensional Monte Carlo method. By changing systematically the duct diameter, the blanket thickness, and the boron content in the plug, analytical representations of the helium production could be obtained as functions of these parameters based on the Monte Carlo results. Their dependencies on the blanket composition could also be clarified. The analytical formulas thus obtained were applied to clarify the shielding design condition required to satisfy the shielding design criteria for a DT fusion reactor.