Abstract
During the 1960s, trenches and wells were constructed for the disposal of liquid low-level radioactive waste (LLLW) in Melton Valley at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. Trenches 5 and 7 were the subject of a remedial in situ grouting program executed in 2005-2006 for the purpose of limiting migration of radionuclides from the site. Both trenches contained poorly (uniformly) graded coarse crushed stone backfill, in which approximately 34 million litres of LLLW per trench were disposed.
A multiple-pass, multiple-stage, multiple-hole permeation grouting program was carried out via driven, vertical, steel sleeve pipes inside the trenches, using five different types of stable, balanced, durable cement-based suspension grout mixes, with various rheological and set characteristics. A grout curtain was then constructed with acrylamide grout in the native soil around and below these trenches. Real time monitoring and assessment of the grouting parameters using CAGES was used to construct the end product.
The in situ grouting (ISG) program was highly successful in reducing the hydraulic conductivity of the grouted materials and the grouted soil “envelope” around the trenches to values well below the 1.0 x 10-5 cm/s target number. The work was performed safely, and without environmental insult.