Abstract
Various aspects of the behaviour of bituminized or cemented simulated low- or medium-level radioactive waste in contact with water have been investigated.
The solubility (~ 0.5%) and the diffusion coefficient (~ 5•10-9cm2/sec) determining transport of water in pure bitumen have been measured for Mexphalte 40/50 at room temperature.
A weighing method has been and used to study the behaviour of bituminized sodium nitrate, sodium sulphate or cation-exchange resin in contact with water or various salt solutions. This method permits the simultaneous measurement of water uptake; swelling and leaching. The particle size of the embedded waste material was found to be an important parameter. Development of solution filled porosity in the samples was demonstrated in many cases. The swelling of samples in contact with water or weak salt solutions was in some cases very pronounced. In strong salt solutions the tendency to swell is much less.
Thermal pre-treatment of cation-exchange resin before bituminization was investigated; it does not seem to improve the quality of the final product.
The interaction between bituminized ion-exchange resin and concrete barrier materials has been studied.
Microbial degradation of bitumen and bituminized sodium nitrate under aerobic conditions has been investigated. The phenomenon seems to be of minor importance as far as leaching from the materials is concerned.
A method for measuring the leaching from a plane surface of cemented waste has been developed. The method avoids the problem of cracks between the sample and the container. It was demonstrated that such cracks can introduce considerable errors in the measured leach rates.
Leaching of cemented sodium nitrate or sodium sulphate was investigated. The absorption of CO2 from the atmosphere was found to influence the chemistry of the leach solution. This had only a minor effect on Cs- and Na-leaching but gave a very pronounced decrease in Ca-leaching.
The use of silica-fume as an additive to cemented sodium nitrate decreased the leach rates by about a factor 4.
The leaching behaviour for bituminized as well as cemented waste materials was found in most cases to be diffusion controlled, i.e. the leach rate decreases with /t. However, exceptions were encountered which makes extrapolation uncertain.
The solubility (~ 0.5%) and the diffusion coefficient (~ 5•10-9cm2/sec) determining transport of water in pure bitumen have been measured for Mexphalte 40/50 at room temperature.
A weighing method has been and used to study the behaviour of bituminized sodium nitrate, sodium sulphate or cation-exchange resin in contact with water or various salt solutions. This method permits the simultaneous measurement of water uptake; swelling and leaching. The particle size of the embedded waste material was found to be an important parameter. Development of solution filled porosity in the samples was demonstrated in many cases. The swelling of samples in contact with water or weak salt solutions was in some cases very pronounced. In strong salt solutions the tendency to swell is much less.
Thermal pre-treatment of cation-exchange resin before bituminization was investigated; it does not seem to improve the quality of the final product.
The interaction between bituminized ion-exchange resin and concrete barrier materials has been studied.
Microbial degradation of bitumen and bituminized sodium nitrate under aerobic conditions has been investigated. The phenomenon seems to be of minor importance as far as leaching from the materials is concerned.
A method for measuring the leaching from a plane surface of cemented waste has been developed. The method avoids the problem of cracks between the sample and the container. It was demonstrated that such cracks can introduce considerable errors in the measured leach rates.
Leaching of cemented sodium nitrate or sodium sulphate was investigated. The absorption of CO2 from the atmosphere was found to influence the chemistry of the leach solution. This had only a minor effect on Cs- and Na-leaching but gave a very pronounced decrease in Ca-leaching.
The use of silica-fume as an additive to cemented sodium nitrate decreased the leach rates by about a factor 4.
The leaching behaviour for bituminized as well as cemented waste materials was found in most cases to be diffusion controlled, i.e. the leach rate decreases with /t. However, exceptions were encountered which makes extrapolation uncertain.
| Original language | English |
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| Place of Publication | Roskilde |
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| Publisher | Risø National Laboratory |
| Number of pages | 159 |
| ISBN (Print) | 87-550-0981-6 |
| Publication status | Published - 1983 |
Keywords
- Risø-M-2415
- Bitumens
- Brines
- Cements
- Decomposition
- Diffusion
- Heat treatments
- Intermediate-level radioactive wastes
- Micro-organisms
- Particle size
- Radioactive waste disposal
- Resins
- Sodium sulphates
- Sodium nitrates
- Solidifications
- Swelling
- Solubility
- Tesing
- Uptake
- Water