The synthesis and characterisation of model glasses for the stabilisation and immobilisation of high level nuclear wastes is described. The introduction of nitrogen into the anionic network of aluminosilicate glasses greatly influences the mechanical properties and leaching characteristics of the glasses resulting in better performance. The redox properties of nitride ions also favour the stabilisation of the low oxidation states of radionuclides which significantly affects the dispersion of radioactive elements by interaction with colloidal particles.