The management of low-level radioactive and mixed wastes at Oak Ridge National Laboratory

The management of low-level radioactive wastes at Oak Ridge National Laboratory (ORNL) is complicated because of several factors: (1) some of the waste that had been disposed previously does not meet current acceptance criteria; (2) waste is presently being generated both because of on-going operations as well as the remediation of former disposal sites; and (3) low-level radioactive waste streams that also contain chemically toxic species (mixed wastes) are involved. As a consequence, the waste management activities at ORNL range from the application of standard practices to the development of new technologies to address the various waste management problems. Considerable quantities of low-level radioactive wastes had been disposed in trenches at the ORNL site, and the trenches subsequently covered with landfill. Because the vadose zone is not very extensive in the waste burial area, many of these trenches were located partially or totally within the saturated zone. As a result, considerable amounts of radioactive cesium have been leached from the wastes and have entered the groundwater system. Efforts are currently under way to remediate the problem by excluding groundwater transport through the burial site. This is being accomplished through several approaches: (1) the introduction of polyacrylamide grouts into the voids contained in the burial trenches; (2) compaction of the trench region to collapse the voids; and (3) capping of the burial site to prevent penetration by surface water