Hydrologic conditions at the Idaho National Engineering Laboratory, Idaho: 1979-1981 update

Aqueous chemical and radioactive wastes have been discharged to shallow ponds and to shallow or deep wells on the Idaho National Engineering Laboratory (INEL) since 1952 and have affected the quality of the ground water in the underlying Snake River Plain aquifer. Ongoing studies from 1979 throug 1981 have shown the perpetuation of a perched ground-water zone in the basalt underlying the waste disposal ponds at the INEL's Test Reactor Area and of several waste plumes in the regional aquifer created by deep well disposal at the Idaho Chemical Processing Plant (ICPP). The perched zone contains tritium, chromium-51, cobalt-60, strontium-90, and several nonradioactive chemicals. Tritiated waste water has formed the largest plume south of the ICPP, and accounts for 99 percent of the total radioactivity disposed of through the ICPP disposal well. Waste plumes with similar configurations and flow-paths contain sodium, chloride, nitrate and iodine-129. Strontium-90 and cesium-137 are also discharged through the well but they are sorbed from solution as they move through the aquifer. Waste water containing strontium-90 has formed a small plume and cesium-137 is detectable in only a few ground-water samples collected very near the ICPP disposal well. Radionuclide plume size and concentrations therein are controlled by aquifer flow conditions, the quantity discharged, radioactive decay, sorption, dilution by dispersion, and perhaps other chemical reactions. Chemical wastes are subject to the same processes except for radioactive decay. 32 references, 34 figures, 1 table