GB2140194A

GB2140194A - A method of packaging radioactive waste

Info

Publication number: GB2140194A
Application number: GB08410843A
Authority: GB
Inventors: Pieere Albert Crouzet
Original assignee: BARROW INVESTMENTS
Current assignee: BARROW INVESTMENTS
Priority date: 1983-04-29
Filing date: 1984-04-27
Publication date: 1984-11-21
Also published as: EP0124825A3; GB2140194B; IL71682A; SE8402303D0; CH654436A5; JPS6040998A; FR2545258A1; IT8420746A0; GB8410843D0; NL8401345A; FR2545258B1; EP0124825A2; ZA843148B; SE8402303L; DE3415433A1; IT1213161B; CA1226380A

Description

1 GB 2 140 194 A 1

SPECIFICATION

A method of packaging radioactive waste 65 BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a packaging of radioactive waste such to store the waste in 70 mentioned condition.

Radioactive waste which is more or less radioactive and is presently produced specifically in nuclear reactors creates an ever increasing number of problems with regard to their storage and no satisfactory solutions thereto have been hitherto found.

One of the problems relates to the selecting of the applicable technique of packaging radioactive waste.

"Radioactive waste" is used to define on the one hand materials which contain radioactive products and are present, for instance, in the form of spheres of ion-exchanging material which are enriched by radioactive chemical products and mixed with water to practically saturation (about 50%) and on the other hand also radioactive sludges containing, for instance, uranium fluorate or uranium fluorite.

2. Description of the Prior Art

Two of the most important solutions to 90 mentioned problem comprise packaging the radioactive waste which preferably initially has been brought into the shape of small spheres or pearls, which packaging is made by means of glass or a synthetical cement.

For carrying out the last mentioned method cannisters of concrete or metal are provided, which are filled with the radioactive waste present in form of small spheres and with synthetic cement called "Synroc". The product "Synroc" has been developed in Australia by Professor D.

Ringwood of the Australian National University.

Test results have, however, revealed that the stability of "Synroc" raises some problems. This material is prone to a partial degrading, specifically by acids produced by the radiation of the radioactive waste and the water present in the "Synroc". Improved results have been arrived at during tests attempting to immobilize the spheres or pearls, respectively, of the radioactive waste in glassy blocks. Since glass lacks the crystal boundaries of ordinary metals, thus has no individual crystals such as ordinary metals, atomic matter, i.e. the radioactive waste, embedded in the glassy block cannot readily leave through it. 115 The following steps are followed for the packaging of radioactive particles: Add boric acid, sand and lithium hydroxide to the radioactive waste present preferably in the shape of spheres or pearls. Heat this mass thereafter to over 1 OOOOC and then allow it to cool so that it sets into cylindrical bodies. Thereafter, these cylindrical bodies can be enclosed in metal cannisters. This method is, however, not absolutely danger-proof and specifically under such circumstances where 125 water can penetrate into the glassy mass in one or the other way.

The problem to be solved in connection with the present invention is the blocking of spheres, i.e. tiny balls of an ion-exchanging resin enriched by rare radioactive chemical substances to which water has been admixed practically up to saturation (about 50%) within a concrete.

The cannister receiving these microballs must be absolutely tight and leak-proof because these substances absorb quite strongly water and are inclined to rather increase their volume due to their absorption of water. This generates forces of such a magnitude that the concrete can rupture the cannisters. This in turn leads to the danger that radioactive products can penetrate towards the outside.

Presently numerous methods are known regarding the packaging of radioactive substances in which either polymers (German method MOWA) or polystyrene (SETRAG-method) are utilized. However, none of these known methods is completely satisfactory because either due to a deficient stability of form or due to a leaking out specifically of the ions of cesiu m.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide a new procedure regarding the packaging of radioactive waste.

A further object of the invention is to provide a method of packaging radioactive waste encompassing the steps of providing a mixture of radioactive waste which is suspended in water to saturation, of a resin and of a monomer such to produce an emulsion with the radioactive waste, its water, the resin and the monomer, and of adding a hydraulic binder to the emulsion such to produce a concrete.

Preferably, the resin is an unsaturated polyester resin.

Specifically, utilizable emulsions are such which are disclosed, for instance, in the U.S.

patents, nos. 4 115 336 and 4 204 988 as well as in the Australian patents, nos. 513 486 and 515778.

The inventive method consists accordingly in producing an emulsion such as disclosed, for instance, in the U.S. patents, nos. 4 115 336 and 4 204 988 or the Australian patents, nos. 5 13 486 and 515 778 by utilization of water, in which the radioactive spheres are deposited, and that thereafter the concrete is produced with this emulsion.

Only the free water in the suspension is utilized for producing the emulsion, whereby the microspheres remain always saturated. If the cement is added to the mixture, the eniulsion is self-destructed. Then, the polymer encases the microspheres and the water accumulated thereat and the balance of the water is absorbed by the cement. The encased or packaged, respectively, spheres can no longer lose water and, because they are in a saturated condition, they also cannot take up any water.

2 GB 2 140 194 A 2 DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention will be more fully understood by reference to the following detailed 5 description thereof based on an example.

500 kg of a resin produced in accordance with the U.S. patents, nos. 4 115 336,4 204 988 and the Australian patents, nos. 513 486 and 515 778 are placed into a container.

During a continuous agitation or mixing, respectively, 603 kg of radioactive waste including the water in which the waste is suspended, are gradually added such to produce an emulsion.

In order to stabilize the emulsion produced as above 5 kg of a colloidal silica ("A6rosil" of DEGUSSA) as well as 10 kg of titanium oxide and 3 kg of antimonyoxide are added.

The total weight of this mixture is 1618 kg, whereby however the emulsion proper weighs only 650 kg, because only 150 kg free water is present in the mixture containing the spheres having a weight of 600 kg to produce the emulsion (composition of the 600 kg: 300 kg rigid 60 spheres, 150 kg inner water, 150 kg free water).

In order to produce a correct concrete the hydraulic binder must be added only in function of the 650 kg emulsion.

In the above mentioned example, in which the ratio emulsion/cement of 4/5 has been taken into consideration, 812 kg hydraulic binder is added, the binder consisting of 567 kg Portland cement and 245 kg pouzzolana as well as 26 kg catalyst (4 weight percent of the emulsion). The mixture cement/pouzzolana is produced for the reason of blocking certain ions of cesium because such a blocking effect of the cesium ions can be made by the pouzzolana.

Additives can be added to the concrete produced such asset forth above, such as, for instance, barium sulphate or colemanite which can also be used for a blocking of certain radiation due to their high molecular weight.

The relations between the index of acid and the OH-index of the resins as well as the number of the specific OH-indices are as follows:

01-1-indices between 45 and 100, indices of acid/OH-indices 0.20 to 0.50.

While there is shown and described a present preferred embodiment of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims.

Claims

1. A method of packaging radioactive waste, comprising the steps of providing a mixture of radioactive waste which is suspended in water to saturation, of a resin and of a monomer such to produce an emulsion with the radioactive waste, its water, the resin and the monomer, and of adding a hydraulic binder to the emulsion such to produce a concrete.

2. The method of claim 1, in which said resin is a polyester resin such as an unsaturated polyester resin.

3. The method of claim 1, in which said monomer is unsaturated.

4. The method of claim 1, in which said hydraulic binder comprises products which hydraulically react with water, or a mixture of such products, such as lime, cement, pouzzolana, etc.

5. The method of claim 1, comprising further the step of adding a stabilizer to said emulsion.

Printed in the United Kingdom for Her Majesty's Stationery Office, Demand No. 8818935, 1111984. Contractor's Code No. 6378. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained..

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