Modeling and validation of radionuclides releases from an engineered disposal facility

The disposal of low and intermediate level radioactive wastes in shallow land burial sites has received strong scrutiny with respect to waste integrity and radionuclides migration through the engineering barrier to the geosphere. The aim of this study is to determine the transient mass release rates of radionuclides from an engineered disposal facility due to waste matrix exhaustion. A finite difference model as developed includes treatment of contaminant mass transport in both the waste and the surrounding media and allows calculation of release rates for cases with and without loss of contaminants by decay. The sensitivity analyses of certain input parameters to release rate calculation are also investigated. Results indicate that the disposal facility with clay and crushed rock backfill materials could contain almost all the radionuclides normally encountered in low level radioactive waste, where short-lived radionuclides having higher distribution coefficient values are completely confined within the waste form. On the other hand, inventories of long lived radionuclides having lower distribution coefficient values need to be regulated so as to reduce their entry into the geosphere.