Comparison of unsaturated flow and transport models with volume and nitrate measurements from a pilot-scale, in-situ lysimeter with different geometry low level radioactive waste designs

Results from a large-scale field lysimeter experiment containing three thirty-ton monoliths formed from actual decontaminated nuclear waste have been used to validate flow and transport models. The models used are a two-dimensional, finite difference transport and diffusion model. The best match of nitrate concentrations calculated to be released from the monoliths with values observed from the lysimeter occurred with monolith diffusivities in the range of 5 {times} 10{sup -9} to 2 {times} 10{sup -8} cm{sup 2}/sec and dispersivities ranging from 15 to 65 cm. The validated models have been used to predict the performance of a low-level waste disposal facility at the Savannah River Site. 4 refs., 9 figs