Performance assessment for proposed disposal of NORM at an existing landfill in New South Wales, Australia

Approximately 5,000 tonnes of soil containing naturally occurring radioactive materials (NORM), primarily consisting of the uranium and thorium series, were proposed to be removed from properties undergoing remedial action in New South Wales (NSW), Australia. These 'NORM soils' were proposed to be excavated and transported for disposal at an existing landfill facility in NSW. Once at the landfill facility and confirmed to meet appropriate acceptance criteria, the NORM soils were proposed to be disposed of in an encapsulated waste cell (EWC) within a previously permitted and constructed restricted solid waste (RSW) cell at the landfill. The characteristics of the NORM soils require that they be disposed of and managed in an appropriate manner, both near-term as well as beyond the time when the EWC liner system can be assumed to have degraded. A Performance Assessment (PA) was conducted to help assess the potential long-term incremental dose received by a target receptor group related to the disposal of the NORM soils at the landfill facility. The PA consisted of computing the doses to a designated receptor group associated with the planned disposal of the soils within the licensed RSW cell at the landfill facility. Primary tasks performed for this PA included conceptual site model (CSM) development, infiltration (Hydrologic Evaluation of Landfill Performance [HELP]) modeling, and radionuclide fate and transport and dose (RESidual RADioactivity-OFFSITE [RESRAD-OFFSITE]) modeling. The results of the PA indicated that the computed doses to the receptors associated with the disposal of NORM soils in the EWC within the RSW at the landfill facility was in compliance with both the current NSW Radiation Control Regulation 2013 and International Commission on Radiological Protection (ICRP) dose limits for the designated potential receptor group. (author)