Disposal of waste containing radioisotopes and of spent nuclear reactor fuel presents a serious problem for which there is as yet no completely satisfactory solution. Such wastes may remain radioactive for thousands of years and can constitute a long-term hazard that is restraining the development of nuclear-generated electric power. Safe disposal techniques are being intensively studied. Ocean dumping, practiced some years ago, is no longer permissible. Small amounts of low-level wastes containing radioisotopes can be diluted sufficiently with an inert material to reduce its activity to an acceptable point. High-level reactor wastes, for example, at Hanford, are stored in concrete tanks lined with steel and buried under a foot of concrete and 5 or 6 ft of soil. Containers of compressed alumina (corundum) have been recommended, as this material remains impervious to water indefinitely. Storage in the form of calcine (granular solid) and in borosilicate glass is a promising possibility under active investigation. The DOE has recommended disposal in deep geologic formations, although the heat generated by the radioactivity could cause fracturing of the surrounding rock structures; this would admit water that would eventually rise to the surface after being contaminated. A test program involving storage in basalt is being conducted by DOE. Storage in salt formations is under serious consideration because they are self-sealing and free from water.See Waste Control.
