Estimation of the leach rate of radioactive waste from earth trenches

Radionuclide leach rate is an important parameter for contaminant transport modeling. The leach rate depends heavily on recharge rate. For estimating the recharge, a regression model based on the rainfall and hydraulic head is developed for the radioactive waste disposal facility at Trombay. The total recharge is found to be in the range of 2.15 - 9.65 cm with a geometric mean (GM) of 4.63 cm and a geometric standard deviation (GSD) of 1.8. The recharge rate lies between 0.024 and 0.11 cm/day with a GM of 0.052 cm/day. Using these values of recharge, the leach rates for l37Cs, 90Sr, 239Pu and 129I are estimated as 6.51 x 10-5, 2.65 x l0-3, 4.02 x 10-5 and 5.66 x 10-2y-1 respectively. These values of leach rates are further used to predict the source concentration of each radionuclide reaching to the groundwater below the earth trench. (author)