Radiochemical measurements for evaluating air quality in the vicinity of low-level waste burial sites - the West Valley experience

Radioactive wastes buried in the commercial low-level burial site at West Valley, New York, consist primarily of low-density, low-specific-activity wastes. Except for contaminated soil and building rubble the wastes were shipped and buried uncompacted in steel drums, wooden boxes, cardboard cartons, or concrete casks. The wet climate at West Valley led to decomposition of the containers and biodegradation of much of the organic material in the wastes. As anoxic conditions developed in the trenches, appreciable quantities of organic complexing agents formed in the trench water, and a variety of gaseous decomposition products formed in the void space within each trench. The escape of the gaseous decomposition products through the trench cover presents the most significant pathway for uncontrolled release of radioactivity from the trenches and the greatest impact on air quality at the now inoperative West Valley site. The radioactive gases HT, 85Kr, 14CH4, 3HCH3, 14CO, 14CO2, 222Rn, and 14C- and 3H-hydrocarbons were identified in the voids beneath the trench covers. Studies were conducted to identify radionuclides and chemical species vented to the atmosphere, to evaluate the mechanisms of venting, and to quantify the leak rate of each radioactive gas. These studies required specialized techniques for sample collection, species separation, and radionuclide measurement. A close relationship exists between the experimental data obtained and the computer models which were developed to estimate gas production rates in a trench and the transport to and escape from the surface of a trench. As a result, field measurements and computer calculations are found to be as important for post-closure characterization of the site as are the radiochemical measurements