ABSTRACT
This chapter starts with definitions, continues with quality assurance matters, and ends with safety assessment issues. Once the validity of the models assumed for calculating the physicochemical function and waste-isolating capacity of a repository has been certified, the matter of quality assurance is a determinant of the function in practice. By quality assurance, the chapter means the guaranteed fulfillment of certain criteria concerning the properties and composition, chemically or mineralogically, of a material, mainly smectitic clay and concrete, for constructing engineered barriers in LLW and ILW repositories on-ground and underground. The engineered barrier materials considered here are smectitic clay and barriers of compacted clay and cement and barriers of on-site cast concrete. Placement of clay-based materials specified in the design descriptions and precept for construction, including compaction and sampling for determination of the density and water content, is essential for reaching the desired state of clay barriers.
