A hydrologic analysis of postulated liquid-waste releases - Brookhaven National Laboratory, Suffolk County, New York

Abstract

Application of general hydrologic principles permits an analysis of the consequences of releases of radioactive solutions. At Brookhaven National Laboratory relatively small quantities of radioactivity are available for release to the environment. Only at the reactor, the hot laboratory, the tank farm, and the waste concentrating plant is there enough activity to make an accident even a potential hazard to the water resources of the area. In these areas of interest the water table ranges from 25 to 60 feet below the land surface. The sand and gravel above the water table and below the soil zone are only partly saturated, and hence the permeability to small volumes of downward percolating fluids is lower than if the material were saturated. About half the rainfall, 22 inches, reaches the water table. Liquid contaminants would move downward primarily by displacing water in the unsaturated zone; some mixing would take place, but some of the contaminants would be held by capillary forces in the unsaturated zone. Contaminants would not reach the water table sooner than a few weeks after release to the ground surface, and under some circumstances several years might be required for all the contaminants to reach the water table. A leak from a buried pipeline or tank could release a larger volume of fluid before being detected, which could infiltrate to the water table through a relatively small volume of soil and cause somewhat more serious consequences than a surface release of a contaminant. Below the water table the shape of the contaminated zone depends on the rate of lateral movement of the ground water, physical properties of the aquifer, and density differences between contaminant and ground water. Laboratory experiments with dyes demonstrate these deductions. Differences between vertical and horizontal permeability of an aquifer, due to the effects of bedding, exert a marked influence on the shape of a contaminant plume. The average rate of ground-water movement beneath Brookhaven Laboratory is half a foot per day ; for conservatism in calculating traveltime and to allow for permeability variations, a rate of 1 foot per day is used. The effects of adsorption and ion exchange on contaminant movement are complex ; extrapolations from laboratory experiments are possible only under specific circumstances. Complexities arise from the presence of several different adsorbents, different radioactive ions and different mechanisms, the presence of interfering macroconstituents in solution, and inhomogeneity of the soil. Because