Fusion Neutronics Experiments for Thorium Assemblies

Abstract

Thorium is a fertile element that can be applied in the conceptual blanket design of a fusion-fission hybrid energy reactor, in which 232 Th is mainly used to breed 233 U by capture reaction. It is essential to validate 232 Th nuclear data by carrying out integral fusion neutronics experiments for macroscopic thorium assemblies. The thorium assemblies with a D-T fusion neutron source consist of a polyethylene shell, depleted uranium shell, and thorium oxide cylinder. The activation of γ -ray off-line method for determining the thorium reaction rates is developed. The 232 Th(n, γ ), 232 Th(n, f), and 232 Th(n, 2n) reaction rates in the assemblies are measured by using ThO 2 foils and an HPGe γ spectrometer. From 232 Th reaction rates, the fuel and neutron breeding properties of thorium under different neutron spectra are obtained and compared. The leakage neutron spectra from the ThO 2 cylinders are measured by a liquid scintillation detector. The experimental uncertainties are analyzed. The experiments are simulated by using the MC code with different evaluated data. The ratios of calculation to experimental values are analyzed.