DIFFUSION LENGTH OF THERMAL NEUTRONS IN WATER BETWEEN 24 AND 82 C

The diffusion length of thermal neutrons in water has been measured at various temperatures between 24 and 82°C, using an 124Sb-Be (25 kev) source. The experiments were interpreted by a theoretical two-group model, one group referring to neutrons of thermal energy and the other group to neutrons of epithermal energy. The diffusion length L, corrected to unit density, and the absolute temperature T, were found to be related by the following expression: Lρ/ρ0 = constant × T0.487 ± 0.026