Compositions – Radioactive compositions
Patent
1987-06-19
1989-07-11
Locker, Howard J.
Compositions
Radioactive compositions
252631, 252633, 106232, 106276, 106277, 1062731, 264 05, 264DIG32, 366 69, 521 25, G21F 916, G21F 912
Patent
active
048470066
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a solid bitumen product having embedded or encapsulated therein granular and/or pulverulent ion-exchange resin which is at least partially saturated with radioactive ions; and to a method for manufacturing the product; and to the use of the product for the long-term storage of radioactive waste of low and intermediate activity.
Energy producing power stations generate large quantities of radioactive waste, which must be converted to a form suitable for long-term storage. The major part of this waste, measured in volume, comprises waste of low and intermediate radioactivity. Most of this waste is concentrated in ion-exchangers, while a minor part is concentrated in evaporators. There are obtained in this way large quantities of radioactive ion-exchangers in granular and/or pulverulent form. The evaporation residues can also be converted to granular or pulverulent form.
When practising known methods, the resultant ion-exchangers are dried and then mixed with liquid bitumen, normally at a minimum temperature of 130.degree. C. The resultant mixture is normally transferred into barrels, e.g. having a volumetric capacity of 200 l, in which the mixture is allowed to solidify and cool to ambient temperature, whereafter the barrels are sealed. The barrels are then placed in long-term storage locations of particular construction, e.g. rock cavities.
The known method of embedding dry ion-exchange resin in bitumen at high temperatures is encumbered with several drawbacks, of which the most serious reside in the risk of fire when using bitumen at high temperatures, and in the fact that the ion-exchangers are in a dry state. Dry ion-exchangers swell considerably when coming into contact with water. Consequently, should the dry ion-exchanger embedded in the bitumen come into contact with water, which is at least theoretically possible, there would be generated an extremely high swelling pressure sufficient to explode the encasing barrel and therewith spread the radioactivity throughout the surroundings. This risk, together with that of fire, has been a subject of criticism on the part of the authorities. Since the liquid bitumen has a high temperature, normally higher than 150.degree. C., water present in the ion-exchange resin will depart upon contact of the resin with the bitumen, the resin therewith losing the major part of its water content. Water is also given off when pre-heating the ion-exchange resin prior to said mixing process. Consequently, when practicing known techniques, it is impossible for the ion-exchange resin embedded in solidified bitumen to be moist.
Other known methods and processes for treating radioactive material are found described in GB-A-959 751, CH-A-549 265, and FR-A-2 289 034, the radioactive material in these cases being mixed with a bitumen and water emulsion. The mixture is then heated to remove residual water, and hence the radioactive material is present in the bitumen in a dry state.
GB-A-2 116 355 describes a method in which ion-exchange resin having radioactive ions absorbed therein is encapsulated in bitumen. The radioactive ion-exchange resin and the bitumen are heated to extract water therefrom.
The objective of the present invention is to avoid the aforesaid drawbacks and to provide a novel and improved method of encapsulating ion-exchange resin in a solid bitumen matrix, in which subsequent to being encapsulated the ion-exchanger is in a wet, swollen form and with which there is no risk of fire during the actual working operation, and to enable the resultant product to be used for the long-term storage of radioactive waste of low and intermediate levels of activity.
This objective is achieved in accordance with the invention by mixing/combining the ion-exchange resin with a bitumen-water emulsion; by adding the ion-exchange resin, and optionally the waste material, to a given quantity of emulsion in an amount such that the break point of the emulsion is reached and the mixture transforms to a solid product, in which the ion-exchange resin is pre
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Eschrich Hubert R.
Hoglund Lars O.
Baxley Charles E.
Locker Howard J.
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