RADIONUCLIDE DISTRIBUTION IN SOIL MANTLE OF THE LITHOSPHERE AS A CONSEQUENCE OF WASTE DISPOSAL AT THE NATIONAL REACTOR TESTING STATION.

Abstract

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 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)