Thermal-Neutron Diffusion in Light and Heavy Water

Thermal-neutron diffusion coefficients for H₂O and D₂O were determined from static measurements of the neutron relaxation length in boron poisoned H₂O and D₂O and pulsed measurements of the neutron die-away in different sized containers of these two moderators. The coefficients derived for H₂O are: These results agree well with previously reported coefficients, fairly well with Honeck's calculations, and very well with Dorning's more recent calculations. The diffusion coefficients for D₂O were derived from data in the range of (equivalent) poison concentrations, ∑_a(B) = −0.04 to +0.04/cm. Restricting the data to these limits avoids possible difficulties associated with the approach to the Corngold limits at κ = (∑_t)_min and . The coefficients derived for D₂O are: Unlike previous experiments, these results indicate no discrepancy between pulsed and static determinations of D₀ for D₂O.