MECHANICAL PROPERTIES OF IMMOBILIZED INTERMEDIATE LEVEL WASTES

The paper describes a programme of work in which the mechanical properties of immobilized waste forms were evaluated and related to the impact performance of immobilized waste packages. The waste forms under investigation were Magnox cladding (swarO and Magnox sludge (corrosion products of Magnox swarO immobilized in cement, ion exchange resins immobilized in a polymer and a control material (cement grout) to provide a benchmark against which the properties of the chosen waste forms could be compared and contrasted. The material properties evaluated were limited to those of direct relevance to impact studies, namely the elastic moduli, uniaxial compressive and tensile strengths, ductility, triaxial failure criteria and behaviour under high rates of strain. During most of the programme, conventional laboratory test machines were employed, although some minor modifications were carried out where necessary. Results are presented for the above range of properties for each material and comments are made on the levels of confidence associated with the data and the limits of their applicability. These properties were used to gain an understanding of the impact behaviour of 500 L drums full of the same immobilized wastes. A programme of drop tests on stainless steel sheet metal drums was carried out at drop heights of between 9 and 36 m and in three different drop attitudes. All drop tests were instrumented with accelerometers. Drum deformations were related to the measured mechanical properties of the immobilized wastes. The drop tests were supplemented by a programme of non-linear, finite-element analysis, points of similarity and discrepancy have been highlighted and some guidelines for estimating the impact strength of immobilized waste packages are put forward.