Investigation of C-14 release in an engineered low-level waste disposal facility

Abstract

Atmospheric releases of C-14 from a generic engineered low-level waste (LLW) disposal facility and its radiological impacts are investigated. A computer model that describes microbial gas generation and the transport has been developed and used to analyze the generation of C-14 contaminated gases and subsequent migration in a facility. Models are based on a chemical kinetic description of aerobic and anaerobic decomposition of organic materials coupled with attending models of oxygen transport and consumption within waste containers in a facility. Effects of radiolysis on gas generation are addressed based on the estimated dose rate for class B and C wastes. Estimates predict that annual atmospheric release of C-14 due to atmospheric pressure variations could range between similar to 2.6 x 10(8) and 5.5 x 10(11) Bq as a result of microbial gas generation based on a volume of 48 000 m(3) LLW disposed in a facility. The associated dose to a maximally exposed individual is estimated to be dominated by ingestion pathway and strongly depends on the fraction of the food imported from an uncontaminated outside area. Dose rates are expected to be <0.04 mSv/yr, considering a reasonable distance between the facility and the exposed population. The depletion through airborne releases of C-14 inventory that is available for transport through other path ways is not expected to be a significant issue.