Study of thermo-stimulated luminescence of an a irradiated natural glass has revealed the formation of a structural defect that cannot be annealed thermally and is therefore cumulative. This phenomenon was again encountered and analysed in synthetic borosilicate glass to be used as radionuclear waste glass. To detect this structural modification, the thermoluminescence signal of an a irradiated sample is traced under certain conditions, Two peak characteristics of a previous a irradiation appear at 230 °C and 320 °C. Their intensity increases at each new experiment, although the a irradiation dose administered remains constant. In other words, despite the successive thermal emptyings, the glass keeps the trace of previous irradiations and consequently gives an increasing signal for constant doses. This study deals with a description of a physical phenomenon concerning the formation of defects within a irradiated glass matrices. This phenomenon was detected after a thermoluminescence (TL) analysis induced by a particles in natural glass (1,2) and it was systematically detected in synthetic horosili-care glass to be used as radionuclear waste glass. It should be remembered that during the fission reaction of uranium 235 in the centre of a nuclear plant, new nuclei and transuranic elements (neptu-nium, plutonium, americium) are generated. The former constitute the major part of nuclear waste, while the latter are long-life a emitters. After waste recycling to extract the uranium and plutonium (which is fissile and can be reused, mainly in fast-breeder reactors), a nitric solution remains containing 99.9% of fission products, 0.5% of generated plutonium and most of the neptunium and americium. Being conRead less <