Architecture and management of a geological repository - Andra

3 – High Level Long-Lived WasteThe bitumen-embedded materials consist of dry extract, obtained by drying the sludge, 70/100 refinerybitumen, surface-active additive, and a small quantity of residual water. The average composition ofthe embedded waste, expressed as percentage weight, is as follows:- Dry extract of sludge: 39% of the weight of the embedded waste. This dry extract is itself made upof a mixture of insoluble and soluble salts, in proportions that vary according to the source of thesludge;- Bitumen: 58% of the weight of the embedded waste;- Surface-active agent: 1% of the weight of the embedded waste;- Water: 2% of the weight of the embedded waste.The radioactivity of the waste comes from traces of activation products, fission products and actinidesevenly distributed in the mass of the embedded waste. Among these, short- or intermediate-livedradionuclides represent a large part of the radioactivity of the packages. However, they release muchless radiation that those described in the previous paragraph: the equivalent ß-γ dose rate in pseudocontactwith the package is one sievert an hour at most. As a result of their relatively low radioactivity,they do not release heat.The specific nature of these packages derives mainly from the chemical nature of the conditionedwaste, which contains a high load of salts and organic matter. Radiolysis of bitumen and of waterresults in the production of gases, mainly hydrogen, as well as traces of carbon monoxide and dioxideand methane (for hydrogen produced through bituman radiolysis, 1 to 2 litres 21 per year, for STE3 andSTEL packages, 9 to 10 litres a year for STE2 packages).Another difference is that the bitumen-embedded packages do not all have the same geometry. A firstgroup, representing 45% of the inventoried packages, consists of stainless steel primary drums of238 litres (STE3/STE2) and 245 litres (STEL from October 1996 onwards). These packages areillustrated in Figure 3.2.3.Figure 3.2.3238-litre stainless steeldrum (STE3/STE2)STE3/STE2 and STEL stainless steel drums245-litre stainless steeldrum (STEL)21At atmospheric pressureDOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM79/495