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Proposed High-Level
Waste Disposal Techniques

The disposal of high-level radioactive waste (hlw) in mined geologic repositories at depths ranging from 1,000 to several thousand feet below the earth's surface is the final isolation technology most studied and favored by the international scientific community. The technology of the mined geologic repository is composed of a system of both natural and engineered barriers selected to prevent or limit the escape of wastes from the repository.1

Next to the mined geologic repositories, sub-seabed disposal is the concept that has been the focus of the most study. With this method, high-level radioactive waste is emplaced beneath the ocean floor within the thick clay sediments (200 to 500 feet) that cover large expanses of the relatively deep (3 to 4 miles) mid-oceanic regions. Additional work to determine the scientific feasibility of seabed disposal (whether waste canisters and the sediments will adequately contain the wastes) is needed.2

A variety of other techniques for the disposal of hlw have been studied or considered by the U.S. Department of Energy. They include:

  1. deep-hole disposal, in which waste-filled cannisters would be deposited at the bottom of holes drilled to a depth of 20,000 to 50,000 feet;

  2. rock-melting, which uses conventionally mined cavities at depths of 5,000 to 6,000 feet;

  3. well-injection, which involves a relatively simple means of permanently isolating liquid hlw after reprocessing by pumping it to depths of 500 to 5,000 feet into a suitable hydrogeological environment at or near a reprocessing plant;

  4. ice-sheets, in regions where ice-thickness reaches several thousand feet, could conceivably provide a remote, low-temperature environment for the containment of hlw;

  5. outer-space, with encapsulated radioactive waste launched into orbit around the sun, and;

  6. transmutation, a treatment (not disposal) technique that theoretically could be used to convert the long-lived radio-nuclides in radioactive waste into stable, short-lived radioisotopes through a process of neutron bombardment in nuclear reactors.3

Currently, all of these approaches to high-level waste management are unfeasable due to technological and/or economic uncertainties.

1 Managing the Nation's Commercial High-Level Radioactive Waste, op. cit., p. 39.
2 Ibid., p. 50.
3 Ibid., pp. 50-53.

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