Development of filling techniques for radioactive waste disposal shafts in hard rock

The choice of material to fill disposal shafts is determined by the nature of the waste, the waste conditioning and the function ascribed to the engineered buffer barrier that it creates. One of the options studied in France is to surround vitrified high level waste packages with sand and alpha bearing waste packages with mortar. Since these materials are to be inserted into a narrow ring shaped space between the waste containers and the wall of the shaft, they require particular characteristics, and tests to validate the techniques used therefore need to be carried out on models which simulate actual storage conditions. The paper describes the results obtained from inserting sand and mortar by gravitational flow. This method yielded an acceptable level of compactness for sand fill and a very compact mortar fill with low permeability. The techniques proposed take into account protection of personnel from ionizing radiation and the risks associated with underground work. (author). 3 refs, 4 figs