Thermal neutron diffusion parameters of O, 20, 50, 80 and 100 percent D₂O in mixtures of light and heavy water were measured by the pulsed neutron technique at room temperature (21°C), near the freezing point of the mixture in the liquid state, and at -20°C in the solid state (ice). A 250-kv pulsed Cockcroft-Walton accelerator, using neutrons from the ₁H²(d,n)₂He³ reaction, was used to generate fast neutrons bursts. The values of the infinite medium decay constant, λ₀, were computed by a least squares fit of λ versus B² data to the expression: λ = λ + D₀B² - CB⁴ The parameters D₀, C, and λ𝗍ᵣ were determined from the above expression after rearranging: λ-λ₀ = D B² - CB⁴ The resulting values of D₀, C, λ, and λ𝗍ᵣ at several temperatures are tabulated. / Ph. D.