Ageing of Eurobitum bituminised radioactive waste under gamma irradiation

The extent of the physico-chemical processes of concern in the study on the acceptability of the Belgian Eurobitum bituminised waste for underground disposal will depend on the degree of ageing of the bituminous matrix. Therefore, the ageing of non-radioactive simulates of Eurobitum under gamma irradiation was studied both in the presence and absence of oxygen. Chemical changes in the bitumen structure were measured in the mid-infrared region with the attenuated total reflectance infrared technique (ATR/FTIR) and evaluation of the peaks at 1700 cm-1 (C=O) and 1600 cm-1 (C=C). Even for the highest total absorbed doses (∼800 kGy at ∼150 Gy/h), the effect of the irradiation in Eurobitum was found to be small and was, in any case, smaller than for samples heated for three hours at 130 deg. C in air. (author)