Since the 1950’s radioactive wastes from a number of laboratories have been stored below ground at the Hanford site, Washington State, USA, in vertical pipe units (VPUs) made of five 200 litre drums without tops or bottoms, and in caissons, made out of corrugated pipe, or concrete and typically 2,500mm in diameter. The VPU’s are buried of the order of 2,100mm below grade, and the caissons are buried of the order of 6,000mm below grade.

The waste contains fuel pieces, fission products, and a range of chemicals used in the laboratory processes. This can include various energetic reactants such as un-reacted sodium potassium (NaK), potassium superoxide (KO2), and picric acid, as well as quantities of other liquids. The integrity of the containments is considered to present unacceptable risks from leakage of radioactivity to the environment.

This paper describes the successful development and full scale testing of in-ground augering equipment, grouting systems and removal equipment for remediation and removal of the VPUs, and the initial development work to test the utilization of the same basic augering and grouting techniques for the stabilization, size reduction and removal of caissons.

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