Determination of Diffusion Coefficients for Thermal Neutrons in D₂O at 20, 100, 165, and 220°C

Diffusion coefficients for thermal neutrons in D₂O were determined at temperatures of 20, 100, 165, and 200°C by measuring the change in neutron relaxation length at each temperature with the addition of known amounts of copper as a neutron poison. The experimental values corresponded closely to calculated values after corrections were made for D₂O purity and neutron spectrum shifts. The corrected diffusion coefficients were 0.841 ± 0.010 cm at 20°C, 0.912 ± 0.011 cm at 100°C, 0.989 ± 0.012 cm at 165°C, and 1.091 ± 0.013 cm at 220°C.