The influence of liquid waste disposal on the geochemistry of water at the National Reactor Testing Station, Idaho, 1952-1970

Abstract

Studies at the National Reactor Testing Station (NRTS), Idaho by the U. S. Geological Survey are described. A summarized evaluation of the geology, hydrology, and water geochemistry of the NRTS and the associated influences of subsurface liquid-waste products discharged from the NRTS facilities are presented. The progressive buildup, distribution, and changes of both radioactive and chemical wastes are analyzed for the total disposal period from 1952 to 1970. Of principal concern is the fate of wastes discharged from the NRTS in the Snake River Plain aquifer, an extremely large and productive groundwater system underlying the vast eastern Snake River Plain. Since 1952, the NRTS facilities (primarily the Test Reactors Area --- TRA, Idaho Chemical Processing Plant---ICPP, and the Naval Reactor Facility---NRF) have discharged 1.6 x 10/suSTAp 10/ gallons of liquid waste containing 7 x 10/sup 4/ curies of radioactivity and about 1 x 10/sup 8/ pounds of chemicals to the subsurface. The discharge has been disposed in wells and seepage ponds. The principal waste products include tritiated water, /sup 90/Sr, /sup 137/Cs, /sup 60/Co, sodium chloride, chromates, and h eat. Wastes at the NRTS have more » been distributed in the Snake River Plain aquifer and overlying bodies of perched groundwater according to hydrologic and geochemical controls. Expansion of the plume of waste products in the aquifer from the ICPP disposal well has been traced over the years. Chloride and tritium in this plume are most widely distributed, detectable over about 15 miles of the aquifer. Migration of cationic waste products, especially / sup 90/Sr and /sup 137/Cs, has been greatly retarded by sorption. Radioactive decay is a significant influence on the spreading and dilution of wastes as they move down-gradient in the aquifer. No detectable wastes have been found close to or beyond the southern boundary of the NRTS. Materials and heat balances calculated for the ICPP wastes indicate that the interpretive subsurface distributions are valid and that the wastes generally remain in the upper 250 ft of the aquifer. The balances indicate that heat and tritium are maintaining an equilibrium (nearly constant) inventory. Waste plumes from TRA and NRF are poorly defined because of insufficient observation wells. (auth) « less