CH651956A5 - PROCESS FOR PREVENTING THE DISSEMINATION OF TOXIC MATERIAL IN THE ENVIRONMENT AND GLASS ARTICLE OBTAINED BY THIS PROCESS. - Google Patents

Description

The invention can be applied in general to lanthanides, for example La, Ce, Pr Nd, Pm, Sm, Eu, Gd, Tb,

concentration and immobilization of toxic solids- Dy, Ho, Er, Tm, Yb, Lu, cobalt, cadmium, silver, zirco-

such as mercury, cadmium, tellurium, lead, nium, molybdenum, technetium, niobium ruthenium, rhodium,

insecticides and poisons, especially palladium, tellurium, cesium, barium, francium, yttrium, ra-

radioactive materials and the like for periods of dium and actinides, e.g. Ac, Th, Pa, U, Np, Pu, Am,

extremely long. Cm, Bk, Cf, Es. Are especially usable in setting

More particularly, according to implementations of the invention of the invention, radioactive waste from tion can be produced new glass articles containing 40 nuclear reactors, the reprocessing of spent fuel from these toxic solid materials and having a high resistance to reactors, spent fuel or thermal storage pools and a high chemical durability to corrosion of other processes producing radioactive waste.

auquese and having sufficiently low values of coeffi- The invention can be implemented in various ways, cient diffusion radioisotopes to provide protection. For example, an easy but very effective way is to tion l environment against the release of radioactive material 45 depositing radioactive materials, for example active nitrates such as radioactive isotopes, nuclear-radioactive waste, in the form of a solid material in a recires, etc., which are concentrated, immobilized and encapsulated in a non-porous glass pient, such as a glass tube, comprising these articles and which can be buried underground or at sea. Both at least one opening, then to heat the container glass articles are formed by depositing the solids to expel water and / or other volatile non-ra-radioactive materials in a glass container, after which is heated so dio-active, s 'there are, and then collapse the walls of the tube the container to expel the non-radioactive volatiles and seal it around the radioactive solids deposited as well as the non-radioactive decomposition products. sées. The heating step can be carried out in such a way that the glass container can be formed from porous glass and can solids, such as nitrates, deposited in the container or not contain a lining of porous glass or tube to decompose. to give non-radioactive gases, which may preferably be particulate or can be relatively 55 such as nitrogen oxides, which are removed from the before large tube as a single or a few cylinders sealing.

of glass. Glass articles are characterized by a radio- Alternatively, a non-porous glass container can be activity greater than for example 1 microcurie, generally closed at one end and at least partially filled with more than 1 millicurie, preferably greater than 1 curie, filling such as particles of porous glass, as on the cubic centimeter part of the article. (When radio-ac-60 waste porous glass powder or very small glass spheres or very diluted tif are treated according to the present invention for silica gel in the form of particles or in another to concentrate and immobilize the radioactive waste to form. The fluid containing the radioactive material is then stored, the radiation activity of the glass articles poured into the container so as to fill the interstices may not reach the level of 1 millicurie per cent the glass particles and then heated to drive out the cubic meters of the glass article and can remain below 1,65 non-radioactive volatile matter with or without decomposi-microcurie per cubic centimeter, when it becomes expedient tion of constituents, such as nitrates, present in them for other reasons of collapsing and / or sealing the container in fluids and finally the glass container is sealed around the glasses. oncentration and immobilization of radioactive solid matter deposited on the particles of

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glass and in the pores of the porous glass particles, if there are here for the glass container and / or for the filling of glass a, contained in the container. In this case, the particles inside the container are of any suitable type - glass contained provide surfaces on which the marks, but preferably are of a resistant, durable, solid-re-type be deposited and also serve to limit the resistance to leaching and are resistant to chemicals. Do not volatilize to prevent a liquid eruption from the door which comopsition of glass having these properties can tube during heating. Particles of glass which can be used, such as glasses with high silica content, by reds provide additional interior surfaces, for example Vycor and Pyrex glasses. The glasses which can be used with the pores of the particles for depositing additional quantities contain at least about 70%, preferably at least 80%, of the solids dissolved in the fluid at the same time, in particular at least about 93% of silica. .

time as external surfaces for the deposition of materials. Suitable glass compositions which may be solid dispersed. used as porous glass compositions in new

In another embodiment of the invention, a calf process generally contains Si02 as a non-porous glass container-cons having major tituant upper ends and have a large specific surface. In open di- and lower can be filled of glass particles towards embodiments of the invention, the content of porous or non-porous SiO 2 which is retained in the glass container with glass or porous silica gel is advantageously by means of a porous structure , such as glass wool or less about 75 mole percent Si02, preferably a disc or cylinder of porous glass in the bottom minus about 82 mole percent Si02 and in particular the container to support the particles of glass in the container about 89 mole percent Si02. Such glasses are pient. The fluid containing radioactive solids described in the published technical documentation, see by dissolved and / or dispersed is then poured into the end of the example E.U.A. n ° 2 106 744.2 215 036,

bottom or bottom of the container and passes through the bed of 2,221,709.2 272,342.2 326,059.2 336,227.2 340,013,

glass particles which act as a filter to separate 4 110 093 and 4 110 096.

of dispersed radioactive solids. The bed of the porous silicate glass compositions may also glass particles may contain glass particles having been prepared as described in E.U.A. No. cation exchange groups bonded to silicon, such as 25,147,225 by forming glass frit particles of alkali metal oxide or ammonium oxide silicon groups. cate, dropping them through a heated area

The particles of porous cation exchanger glass eliminating in which they become fluid while falling li-nent of the fluid radioactive cations dissolved. They can be made briefly and take a generally spherical shape by passing the fluid through one or more of these beds using surface tension forces and then cooling them with conventional techniques for filtration and / or ion exchange to maintain their glassy nature and their spherical shape. multi-bed until the fluid has been stripped of its In general, the porous silicate glass can be prepared for radioactivity to the desired level. When the glass particles melting an alkali metal borosilicate glass, used for filtration and ion exchange become char-separating by phase separation into two re-aged glass phases or when, for another reason, one does not wish the utilities between them and by removing by leaching one of the phases, to read more, one can heat the beds and the container to know them the phase of oxide of boron and oxide of alkali metal, holding to expel water and / or other volatile matter or to leave a porous skeleton consisting mainly of non-radioactive gases such as decomposition products, the glass phase of a high silicate content remaining. The for example of nitrogen oxides, and to then subside the main property of porous glass is that when it is pore particles of porous glass containing the reformed cations, it contains a large internal surface area couio-active, to melt together the glass particles, covered with hydroxyl groups bound to silicon. It is preferred to use thus capturing radioactive solids and / or ca- a porous glass formed by phase separation and leaching deposited on the interior and exterior surfaces of the par- because it can be prepared with a large surface area ■ ticles and then to collapse the glass container and seal it per unit volume and has small pore sizes for around all of its contents to encapsulate the entire mass providing a high concentration of super hydroxyl groups in a substantially full resistant structure to leaching 45 silicon-bound ficals, and because leaching to form suitable for long-term storage. pores leaves residues of hydrolyzed silica groups in the

According to yet another embodiment of the inventor, thus increasing the number of hydroxyl groups su-tion, the glass container itself can be formed of glassware linked to the silicon present. The porous borosilicate glass and the radioactive fluid is introduced inside the reagent when used as a filling can be under the container and it is passed through the pores of the glass from 50 powder form as for use in columns the interior walls to the exterior walls of the chromatographic container or in a predetermined shape such as glass. Radioactive insoluble solids initially - only plates, spheres or cylinders.

dispersed in the fluid are deposited on the inner wall. It is preferable to use a glass composition in the bottom of the container and the radioactive solids dissolved in the container which will produce a coating or an envelope of a test are distributed. in the pores of the glass container where they 55 have a low content of constituents which can be removed by leaching, such as can be deposited by various techniques, such as those of alkali metals or boron. In the event that this is not taught in the E.U.A. n ° 4 110 096. It is possible or practical, it is preferable then to introduce the reci-fer then the container to drive out the volatile matter pient in glass before or after collapse in a second as described above, to collapse the pores of the glass container container which has a composition not containing or glass and finally to collapse the glass container and the 60 containing only small amounts of alkali metals or seal, so as to encapsulate radio solids -acti- boron or other constituents removable by leaching. It is seen in the glass structure. Before heating, it is particularly preferred to use glasses with a very high worm on the surfaces of the outer walls of the container for removing silica content both in the glass container and in the storage of radio solid materials. -active agents deposited from the glass coating layer.

outer surface of the glass container so that fina-65 When it is desired to avoid a rupture of the glass container also a non-radioactive coating is formed after the in the event that a glass lining, such as particles,

heating to collapse the pores and the container. spheres or a glass cylinder, is arranged inside the

Non-porous glass compositions when they are used as a glass container, it is preferred to use, as glass for the

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container, a glass which, after the deposition step, has a temperature. The glass container is hollow and has at least one glass transition ture up to 100 ° C at the opening. The particularly preferred container for processing

glass transition temperature of the glass formed from the liquid ment is a container in the form of a tube filled with glass and solids deposited in and on air. When the container has more than one opening,

the glass lining. It is also preferred for this purpose to use 5 as in the case of a hollow glass cylinder (or of a glass container as a glass which, after the deposition step, tube), one or more of the openings can be capped at a coefficient of thermal expansion of up to up with a glass stopper to prevent fluid from escaping

about 2xl0_6 ° Cau coefficient of thermal expansion of the per during filling in a discontinuous operation,

glass resulting from the sintering of the glass lining and of the materials. For a continuous operation, a tube of solid res glass deposited in or on the glass lining is preferred. In i0 with an opening at each end. In this last-

determining the glass transition temperature and denying cases, the two openings can be plugged with a coefficient of thermal expansion, the quantity and type of porous glass plugs. The larger the volume of fluid to be treated, the solids deposited in the pores of the glass container, the more preferable the continuous operation becomes. When using a porous glass container, and exemplary materials of other configurations of the glass container which solids deposited in the pores and on the exterior surfaces are useful for the purposes of the present invention are those of the porous glass lining , when used, and U-shaped, beaker-shaped, solid res-shaped containers deposited on the outer surfaces of the can lining, etc.

Non-porous glass, when used, can have an effect The simplest embodiment of this inconsiderable present on glass transition temperatures and conditions only involves the deposition of radioactive materials thermal expansion and must be kept 20 ves in a non-porous glass container followed by the slit. It is also preferred to regulate the cooling of the source of the container walls and of the burial of the composite article made up of the glass container and its resulting glass container underground or at sea. reci-content, resulting from the deposits and the sintering step, so glass pient can be in the form of test tube and formed so that the cooling rate is as uniform as pos- non-porous glass as 'a Vycor glass (trademark susceptible in the whole composite of the glass container and for a glass resistant to heat and chemicals, of its contents. Although a rupture has been observed in some a low coefficient of thermal expansion, Corning in some cases, it did not prevent reaching the goals of pre-Glass Works). According to another mode of implementation of the invention, that is to say the immobilization and the isolation present invention, the radioactive material is deposited in relation to the environment of radioactive solid materials. - a porous glass container. According to another mode of implementation coming from radioactive waste containing such maneuver still, the radioactive material can be deposited in solid bodies in the dissolved and undissolved state. a non-porous glass container having a second glass,

In a method according to the present invention, a material, for example a glass lining, arranged inside the container.

radioactive is deposited in the solid state in a container in a container. According to yet another embodiment of the hollow glass comprising at least one opening. The present invention, the radioactive material is deposited in a radioactive material is deposited from a fluid which passes from my porous glass container having a second glass or a continuous stopper through the container. glass or which is placed of glass weaving arranged inside of it. In the last two

discontinuously in the container. The fluid may contain nier modes of implementation mentioned, the second glass of dissolved radioactive materials, radioactive materials may be a non-porous glass or a porous glass. The two- •

particles or both types of radioactive material. th glass, whether porous or not, can be a preform

The fluid can be a gas or a liquid or both. The glass materials of any suitable shape (for example in radioactive forms, whether in particles or dissolved in the form of a cylinder, of rectangular shape, in particles, in in the fluid to be treated, can be deposited on a spheroid glass, etc.) to be housed in the glass container and the non-porous or on a porous glass having a structure to fill at least partially. The second glass, however,

pore reuse in mutual communication. When used is preferably in the form of particles such as porous glass, the pores are usually smaller than 45 spheres. A preferred mode of implementation of the present in-

the radioactive materials in particles in the fluid, of use uses a tube of non-porous glass containing nières to prevent the passage of the particles in the pores connected particles of porous glass.

between them. In this case, the particulate matter is deposited on the surfaces of the inner wall of the Nuclear Waste glass container in a porous non-porous tube. The radioactive materials which are dissolved in the 50 A hollow non-porous glass container formed of fluid glass or which are gaseous radioactive materials pass Vycor or silicate glass is at least partially filled in the pores of the glass and are trapped in the structure of a fluid containing radioactive materials. The porous container is either by reaction with the glass, undergoing a reaction preferably comprises an opening which is blocked by a cation exchange with the glass, or by precipitation in a porous glass stopper. In the case where the fluid is a li-the pores of the glass. Whether a porous glass or a glass 55 is used, for example water, the container is then heated to non-porous, after the radioactive material has been deposited glass to evaporate the fluid to dryness so to be precipitated in the hollow glass container, the radioactive materials of the radioactive materials on the interior walls of the container are enclosed in the glass matrix by a glass collapsible. Temperatures can be used slightly from the container walls. The collapse of the walls of the re-above the boiling point of the fluid and going up to the container is carried out by heating the container while: a) about 60 ° C. above this point d 'boiling. A vacuum can be used inside the container, b) lower temperatures are applied to evaporate the liquid when a pressure external to the container, for example by placing a vacuum is applied inside the glass container , a weight on the container or by increasing the gas pressure The glass container is then heated further and to approximately outside the container or c) or combinations of 400 ° C are used the radioactive salts initially present in the methods a) and b). When radioactive material is deposited 65 nuclear waste, for example the nitrates of radioactive metals in the pores of a porous glass, the containers are heated, decompose or are calcined to form the oxides for collapse the pores before collapsing the walls of the corresponding, for example radio-ac-cipient metal oxides. tifs. Non-radioactive gaseous decomposition products,

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for example nitrogen oxides, are removed by heating in the E.U.A. n ° 4 110 096. Thus, the precipitation and the porous plug plays the role of barrier to prevent can be caused by cooling of the glass container (prone nuclear waste to leave the glass container. Thermal cipitation), by chemical precipitation and by further heating the glass container until it collapses combinations of this process. The chemical precipitation com-to trap the precipitated crystalline nuclear waste 5 takes precipitation by the effect of common ions to reduce the sealed container. Before the introduction of the fluid into the solution the solubilities and cause the precipitation of the ra-glass container materials, dissolved silica and dioactive alumina can be added. It also includes the fluid technique so as to create a callused material during the exchange of solvents to reduce the solubilities so as to heat. The calcination of nuclear waste in reciprocating precipitation. In this method, the metal test tube is well known. The procedures and porous glass can be immersed in a solvent in which the operating conditions which are used in the calcination of soluble radioactive material present in the pores is less in a metal container are also usable when one is soluble. The addition of a suitable precipitant which reacts with calcination in the glass containers according to the pre-dopant, or the dissolved radioactive materials, in the present invention and these teachings are incorporated here by res or cause an appropriate change in pH is also a benchmark. The glass tube typically collapses at 1300 ° C by chemical precipitation. The precipitation can also approx. Other details concerning the drying, the imprisonment- being caused by evaporation of the fluid from the pores, preferably from radioactive decomposition products and the collapse- under vacuum and at temperatures close to the amassing temperature of the glass container are shown below. biante or below. Precipitation techniques other than those involving evaporation of the solvent as the sole

Nuclear waste in a porous glass container 20 means of precipitation are used when it is desired to obtain

The manufacture of the porous glass container used uniformly in higher strength glasses process according to the present invention can be carried out in a mechanical manner.

any of the available methods used Combinations of precision techniques may be used

by those skilled in the art to form a pitation porous glass container. A preferred combination of precipitation techniques

of any desired shape, such as cylindrical or rectification is the combination of thermal precipitation and angular. The glass preferably has a precipitation composition by ion exchange.

more than 75% silica. We prefer to form porous glass. The deposit of radioactive materials dissolved in the

according to the methods described in the E.U.A. n ° 4 110 096. res can also be carried out by a reaction of exchange of

For example, a glass composition containing silica, tions in the glass. The manufacture of glass suitable for boron trioxide and two alkali metal oxides 30 cation exchange reaction as well as a detailed description

(like Na20 and K20) is melted and pulled into long rods or lée from the cation exchange process are presented in the long tubes. By appropriate heat treatment, separate patent application filed on the same day as this de-

these rods or tubes in two phases: a phase rich in silica mande, in the names of the Applicants and entitled “Fixing by also containing small amounts of B203 and of oxide of ion exchange of toxic materials in a matrix of tal alkaline and a low silica phase which additionally contains 35 glass, incorporated herein by reference. A glass container for

large amounts of B203 and alkali metal oxide. Tires with ion exchange capabilities are particularly suitable for

Heat treated tubes or tubes are then immersed well for a continuous process. The solu-a suitable leaching solution is passed so as to dissolve and tion inside the container, through the porous walls,

removing the phase having the lowest silica content. The elimination for the exchange of cations and the imprisonment of the nation material of this phase and a subsequent washing give a 40 radioactive glass dissolved, and then the rest of the solution, that is to say

porous, characterized by an SiO2 content greater than 90%, ie the solvent such as water, comes out passing through the wall the percent which is ready for use as a container outside the container.

glass for the encapsulation of the dissolved radioactive material After the deposition step, the outer wall of the glass or gas tube according to the present invention. porous can be washed so that the radioactive material

The invention is further described with reference to a precipitated container 45 disposed in the pores of the hollow surface layers of porous glass which is in the form of a test tube. One exterior of the porous tube is removed. The washing step is lution containing dissolved radioactive materials and preferred when it is desired to produce a radioactive article in radioactive materials in particles such as precipitates free of radioactive material, or having only a small metallic from the family of platinum group metals which quantity, in its outer surface layers, and are typically present in nuclear waste solutions is not essential in the broad sense of the present invention, key from fuel reprocessing stations The solvent from the solution is then removed, preferably without spent nuclear, is poured into a porous glass test tube. migration of radioactive material present in the pores.

The solution permeates the walls of the tube and in this way This can be done by the drying technique described in has the radioactive material dissolved in the form of the patent E.U.A. No. 4 110 096. Typically, the container doped in the walls of the porous glass test tube. In addition, 55 porous glass is placed in an oven and heated to a temperature

their, the radioactive materials in particles, due to their higher rature of heating under vacuum at a lower speed.

particle size, do not penetrate the walls of the interior at 100 ° C / h. However, in certain circumstances, it is a glass container, but rather is deposited on the inner wall. It is advantageous to use a higher rate of heating of the tube by sedimentation or filtration. Deposition on to increase the rate of passage of articles through the inner walls of the tube occurs by filtration and by a treatment system.

subsequent evaporation of the fluid. Once the tube is dried, two forms of material are obtained

Radioactive material that was initially in solution, radioactive deposited: 1) initial particulate matter-

on the other hand, is distributed in the pores of the undissolved glass tube which are arranged in the interior solution space, in the form of a nitrate for example. The opening defined by the inner walls of the glass tube and 2) the ma-

in the tube can then preferably be capped with a 6s initially dissolved which are arranged in the pores, glass stopper porous or not. Next, the radio material from the walls of the glass tube.

Active ingredient is deposited in the pores by precipitation. After the drying step, continued heating from the solution by methods such as those described in the glass container causes the decomposition of the ra-

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dio-active agents deposited both in the pores and outside the pores. For example, the radioactive material changes from its nitrate form (or from any initial form) to its oxide or phosphate or silicate form, the nitrogen oxide decomposition products being removed. If it is desired to encapsulate radioactive gases, for example krypton or iodine, or can introduce them into the pores of the porous glass at a temperature, for example from 50 to 150 ° C., below the glass transition temperature, Tg, of the glass tube containing the deposited materials.

Heating is continued until the pores of the porous glass collapse. When the pores collapse, the radioactive material that has been deposited from the solution, including the radioactive gases, is completely trapped in the glass matrix. It is chemically linked to the glass and physically enclosed inside the glass. Heating can be continued without much risk of vaporizing the radioactive material in the glass, because it is now buried in the glass itself. While continuing to heat the tube, a small difference in pressure applied between the inside of the tube and the outside of the tube can be used to collapse the tube. The pressure inside the tube is made a little lower than the pressure outside the tube (by means of a vacuum) to gradually collapse the tube into a full cylinder. An external pressure produced by a weight placed on the tube, for example, can also be used to collapse the walls of the container. After the tube (or other glass container) has collapsed, the radioactive material that was initially in the form of particles is trapped inside the resulting sealed glass container. The initially undissolved particulate radioactive material which is then trapped in the glass container may be in the elemental form of a metal, a metal salt, a metal oxide or other metallic forms. The radioactive material in particles which decomposes as described below will be in the oxide, phosphate or silicate form. The collapsed tube is in the shape of a full cylinder where two types of radioactive material are trapped: 1) a radioactive material which was initially soluble in the solution and which was eventually chemically bound to the glass or trapped in the glass and 2) a insoluble solid radioactive material which was finally encapsulated by the glass. Thus, after the hollow glass article has collapsed, a glass article is obtained which comprises the initially undissolved solid radioactive materials trapped in its central portion. The initially dissolved radioactive materials are trapped and immobilized in the glass matrix surrounding the central portion.

The use of a hollow porous glass container, in particular a tube-shaped container, provides several advantages over the use of a porous glass cylinder. For example, an advantage of a porous glass container in the form of a test tube is that two surfaces are used (an inner wall surface and an outer wall surface). The solution containing the nuclear waste is placed inside the tube to trap the radioactive materials in particles and for passage through the pores of the solution containing dissolved radioactive materials. A solution which will cause precipitation in the pores of the dissolved radioactive material can be introduced through the outer surface of the porous tube. For example, potassium silicate reacts with a lot of nuclear waste (for example iron). The high pH caused by potassium silicate causes precipitation (eg iron oxide) in the pores. In the case of ruthenium, ruthenium silicate precipitates, and so on. By introducing the material through the external surface of the porous tube, the action which one can have on the precipitation of nuclear waste inside the pores of the porous glass is improved.

Another advantage of the tube configuration is that dissolved radioactive materials which do not precipitate during the precipitation step can be drawn into the inner wall of the tube. Thus, the tube is completely filled with the fluid containing the radioactive material. It is then placed in clean water or in a second solution and a vacuum is applied inside the tube. By doing so, some dissolved radioactive material may not be precipitated with a drop in temperature, by insolubility in the second solvent or by chemical activity with the second solvent. Dissolved radioactive material which does not precipitate for any of these reasons is sucked into the inner wall of the tube, the outer wall remaining clean. This current towards the interior wall causes a distribution of the dopant, that is to say of the radioactive material initially dissolved, which is stronger on the interior surface of the tube. When the tube is finally collapsed into a cylinder, this region of high concentration of radioactive materials is trapped in the total glass system. It is thus possible to avoid a high concentration of nuclear waste on the outside of the glass article.

Another advantage of the tube configuration is the imprisonment of all radioactive gases produced by decomposition of the radioactive materials during the drying step. For example, if ruthenium tetraoxide is produced from radioactive materials inside the pores, it can be drawn through the center of the tube out of the drying / sagging furnace and into another glass tube which is at a lower temperature. The radioactive gases are filtered through the second porous glass tube. The fumes react with the silicate in the glass and precipitate inside the pores of the glass. For example, rubidium will be reduced from the tetra-oxide to a lower degree of oxidation and will precipitate in the pores. The second tube serves as a micropore filter. Its pores are then collapsed by the collapse of the walls of the tuve so as to trap and immobilize the gaseous radioactive materials in a sealed glass matrix.

As can be seen, porous glass tubes can be used to absorb radioactive gases from nuclear waste disposal systems that do not use porous glass containers. Thus, radioactive fumes from other nuclear waste treatment systems can be treated in a porous glass filter. Radioactive fumes may contain particulate radioactive material and gaseous radioactive material. Non-radioactive materials, for example water, etc., will pass directly through the porous glass filters while nuclear waste, for example ruthenium tetra-oxide or cesium, will be trapped inside of the porous glass filter. When the filters begin to lose their effectiveness, the filter itself is heated to collapse the pores and walls of the porous glass filter. Both the radioactive materials in particles which were in suspension in the gas and the gaseous radioactive materials are thus trapped and immobilized in the glass matrix. When using the porous glass container as a filter, it does not have to have the configuration of a test tube. Flat configurations, for example, are just as good, or even better in some cases, than the test tube configuration.

Another advantage of using a porous glass container (instead of a porous glass cylinder) is that the processing time is reduced for a given thickness of porous glass. For example, the time required to impregnate a cylinder of porous glass with a radius of 10 cm is the same as that required to completely impregnate a container of porous glass with an inner radius of 10 cm and an outer radius of 30 cm. The wall of the glass container is 20 cm thick.

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thickness, but the impregnation occurs so much by the surface having 60% voids and the particles (or grains) can represent

inner than by the outer surface, at a depth of feeling only 40% of the interior volume of the container in 10 cm. In the case of the glass cylinder, the cross-glass area. On the contrary, if we use round spheres, they have glass versal is only 100 n (or about 314) cm3. There is a tendency to pack better and garbage rates can be obtained, however, for the glass container, the cross-sectional area of 60% or more. The ideal for compacting dirty spheres of porous glass is 800 n or about 2514 cm2 or 8 would be a filling rate of 80%. One can get one time greater than that of the cylinder. Thus, during the same period, improvement in compaction by applying pressure. In time, a much larger amount of glass may be im- can use glass particle sizes ranging from 5 mi-

pregnated. This advantage also comes into play during the drying stage and crons at 5 mm, preferably from 50 microns to 1 mm.

during decomposition. For comparison purposes, loading of the glass container can be done if there is zero contraction for the porous glass. it is desired in any suitable manner other than

When the glass container is collapsed, the final diameter of those described above.

resulting cylinder is approximately 28 cm. Furthermore, the diameter of several glass can be used in the final stage of the glass cylinder which had a radius of 10 cm is drying. First, we can place on top of the party-about 20 cm. Thus, a larger final product containing 15 glass cules a little glass wool or a glass disc a greater quantity of radioactive waste is obtained in porous or another type of porous top to prevent them from processing time. equal when using the container to move vertically when the gases are expelled from the glass. radioactive waste contained. In addition, sufficient space must

be left at the top of the container so that particles of

Particulate glass inside a glass container 20 glass can move upward when the gases are chased

A particulate glass which can be a non-porous glass and then finally fall back once the gas flow or a porous glass having a porous structure with connected pores stopped. It is also preferable to dry the container and the parts therebetween or a mixture of the two may be arranged in the glass particles by having a relatively small heating zone of the glass container. The formation of non-tite particles which is moved up and down to expel the carrier gases is well known in the art. Particles of 25 gressively from the top to finish at the bottom.

non-porous glass of conventional compositions or variants Otherwise, if the heat is strong or applied to the bottom, one of these compositions can be used. Boiling particles may occur inside the container near the porous glass may be formed from glasses having bottoms, which may result in glass particles compositions similar to those used to form the container being sprayed outside at the top. Advantageously, the pient in porous glass. The porous glass is preferably formed 30 the top of the container should be kept above using the compositions and methods described in the 100 ° C. One can operate thus relatively quickly, of patent E.U.A. n ° 4 110 096. such that by starting to heat at the top and in

To prepare a powder into glass, you can pour the glass placing the heater down, all the water in the molten container directly in cold water to break it and it can finally be evaporated. So when a layer fragment into small pieces. Alternatively, the molten glass 35 porous glass particles is dried, it is held in can be drawn into rods or cast to any desired shape the temperature range of 100-150 ° C to prevent that. In the latter case, the glass is broken in a grinder. other toxic gases escape through it. The vapors The pieces of glass are sieved so as to obtain non-radioactive compounds for the decomposition of nitrates in the container.

particles of the desired particle size. The pient particles can escape through the porous dry glass sieve layer are then passed through a flame of 40 while the cesium and sodium and other radio-ac isotopes-so that they take the form of small spheres. Advantages such as cadmium are retained in this porous sieve.

stage of formation of spheres instead of simple use- Once the water has evaporated from the entire column, this sieved glass particles which have ir- last shapes can be heated to a temperature of order of regulars varying at random is that this allows a 400 ° C to be obtained quickly enough to prevent the distillation of ni-

more uniform and denser filling in the container in 45 radioactive trates. At temperatures of this order, the decom-

glass. Thus, two types of particles can be produced from the start position and fumes of nitrogen oxides are chased.

glass. One type is simply broken and sieved and squeezed glass. Here again, ruthenium tetra-oxide can pose a door so elongated grains of irregular shapes varying problem, because it must be prevented from escaping from the top at random. The other type is broken glass, sifted and melted from the container while maintaining the layer of glass particles by passing through a hot zone and then cooled quickly in the top hot enough for the water vapor to produce glass particles in the form of escapes, but cold enough for Ru04 to remain in the container

very small spheres. pient while the decomposition continues. As long-

The particles thus obtained are non-porous and may last long for the nitrates decomposition fumes to continue.

to be used in the embodiment of the invention to be released, the material will be under highly conditions in which the radioactive material is deposited on the particulate oxidizers and there is not much likelihood that Ruthenian

the non-porous glass inside the glass container. be reduced to lower degrees of oxidation, less vo-

To make non-porous glass particles porous, we use latils.

reheats them to approximately 550 ° C for approximately two hours. Once the decomposition of nitrates is complete, we can

They thus undergo a phase separation and they are apply a vacuum inside the container while subsequently leached; see the E.U.A. No. 4 110 096. The product 60 maintaining the temperature, high, thereby reducing the finished pressure is a porous glass in wet particles with pores of oxygen vapor low enough for the tetra-oxide to bond together in the of every particle that can ruthenium spontaneously decomposes at lower degrees

be used in the process according to the present invention. Any oxidation which have a high temperature characterization times, by heating the porous glass above 100 ° C, water or a very low vapor pressure, so as to imprison-

is eliminated and a porous glass in dry particles is obtained which is permanently ruthenium in the glass. The-

is a rolling powder product. pressure must be applied before porous glass

If elongated grains are used, the filling of the container really begins to lose its pores under the action of heat.

glass may not be very effective, typically there may be them, because under these conditions we can also reduce the

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amount of gas dissolved in the final product. In fact, by reducing the amount of gas inside each pore of the glass, the amount of soluble gases in the glass is reduced. Then, the temperature is gradually raised and each time there is a pressure jump, the vacuum is applied until the pressure slowly drops. Around 1300 ° C, the exact temperature depending on the configuration of the oven, the bore of the container, the type of glass particles, etc. the tube collapses. If the container walls are thin, they sag to a flat or elliptical cross section, forming a ribbon rather than a cylinder. If the walls are thick, a cross section similar to that of a cylinder is obtained. One way to encourage the formation of a cross section resembling that of a cylinder is to pull the container while heating it so that it elongates while it collapses. For convenience in packaging finished glassware, it may be easier to pack a cylinder-like section for storage. If there is a major heat transfer problem, however, it may be more convenient to work with flat ribbon-like cross sections in order to alleviate these heat transfer problems. By using a narrow heating zone and moving it up and down, we arrive at a region near the top where there are no glass particles left and the glass container collapses on itself to ensure better sealing isolating neclearous waste.

If the degassing is carried out correctly, there will be only a very small quantity of bubbles and this results in a finished product which comprises an envelope of non-radioactive glass, of a low coefficient of thermal expansion, surrounding a glass d '' a high coefficient of thermal expansion. This provides compression on the outer layers of glass and tension on the inner core of glass. If the interior glass is relatively free of bubbles, it will withstand the tension and make the final article a resistant prestressed material having a modulus of rupture considerably greater than that of glass. The advantages of maintaining the finished product in the monolithic state are as follows: 1) the external surface area of the monolithic glass is much less than if it is discontinuous and since the amount of leaching is proportional to the surface area, the risk of leaching is greatly reduced, 2) in the case where there is no nuclear waste in the outer layers of the container, there is no nuclear waste available to be removed by leaching in the initial period of conditions leaching until, if ever, leaching is able to continue through the thickness of the outer layers free of radioactive waste from the collapsed container. This can be considered a long period compared to the short half-life of radioactive isotopes encapsulated inside the container, thus encapsulating them for the duration of their radioactivity and no radioactivity is exposed to the biosphere. In addition, the treatment of nuclear waste according to the present invention has the advantages that it does not use an oven electrode which could be corroded by molten glass, that there is no smoke from radio elements. -hunted assets and that in general a very clean operation is possible. In the event that a glass container breaks, you can get rid of the glass by reducing it to particles or by remelting it and transforming it into particles as explained above and placing these particles in another glass container. Thus, there is no new waste produced, requiring a separate disposal system.

A cylinder of monolithic porous glass (not in particles) or a similar preform containing a solution of radioactive waste has a tendency to rupture on heating because internal pressures increase due to the boiling of internal water. If the boiling is strong enough, the internal pressures can become strong enough to cause the glass preform to rupture. Also, after most of the liquid has been removed, when the preform becomes dehydrated,

it contracts and, if the dehydration has been irregular, unequal stresses develop when one side has contracted more than the other, which can cause the preform to rupture. In addition, at the slightly higher temperatures used to decompose salts, such as nitrates, gases, for example nitrogen oxides, are released. Here again, too rapid release of these gases can break the preform.

In addition, if the material is irregularly deposited in the monolithic porous glass cylinder or the similar preform, the dopant increases the coefficient of thermal expansion of the silica component of the glass preform and, when the pores collapse by heating, the coefficient of irregular expansion can lead to rupture. The distribution profile of the dopant in the monolithic glass preform must be very well adjusted to avoid rupture. These problems are greatly reduced or eliminated when using porous glass particles in a glass container. The individual particles are so small that the stresses that settle on them during heating are not strong enough to break them and if a small number of them actually break, it results in little or not at all. problem and heating can be done much faster. In addition, the distribution profile of the dopant in cross section can be important. In the case of a non-porous glass container, the outer layers of the final product will have the initial coefficient of thermal expansion of the container which can be formed with a coefficient of thermal expansion lower than that of the glass particles at the inside. Thus, the final product, in this case, has compression on the surface which makes it more resistant.

In addition, the use of a glass container containing porous and / or non-porous glass particles has the additional advantage of providing a distribution of radioactive solids deposited throughout the interior of the tube rather than just on the interior surfaces of container walls as in the case of a glass container in which a glass lining is not used or on the exterior surface of a porous glass cylinder when one is used. In addition, when using a non-porous glass container filled with glass particles, the resulting coating is free of radioactivity, presenting no significant risk of contamination by radiation to the environment.

In the treatment of glass containers according to the present invention, gases can escape from the container through the open end. A convenient way to control these gases is to introduce a layer of porous glass into the open end of the container. It will act as a molecular sieve and due to its very large initial specific surface, for example hundreds of square meters per gram, the gases trying to exit the container are trapped by it. By regulating the temperature of the layer of porous glass, it is possible to allow the passage of water, non-radioactive decomposition products of nitrates and other non-radioactive fumes which it is desirable that we get rid of, while trapping ruthenium, cesium, cadmium and other radioactive materials in the container at the same time. The temperature differences along the container can be advantageously used to expel volatile non-radioactive materials while preventing radioactive materials from escaping.

It is also advantageous that the container can be collapsed into a cylinder of smaller dimensions or into a ribbon having a small dimension, namely its thickness, and a greater width. The smaller dimension facilitates a more uniform heat dissipation, i.e. reduces the gra5

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temperature dients in the resulting glass and significantly avoids or reduces breakage.

Non-porous glass lining

The glass container can be lined with non-porous glass particles in addition to or in place of the above-mentioned porous glass particles. The non-porous glass particles can be prepared from any suitable vitrifiable composition using the procedures described above with respect to the porous glass particles, except, of course, that the phase separation steps and acid leaching are not necessary in the case of non-porous glass. The non-porous glass particles can thus be in the form of spheres, elongated grains or any other suitable shape and they behave in the glass container in much the same way as the porous glass particles, except that 'there are no pores into which dissolved radioactive materials penetrate. Consequently, the radioactive materials, both dissolved and undissolved, are deposited on the peripheral or external surfaces of the particles and in the subsequent heating step the oxide forms of the radioactive material react with the molten glass particles. non-porous and become part of the final glass product, while other forms are trapped deep inside the final glass product. In many cases, it is preferred to use a mobile heating zone with a pressure difference produced by evacuating the interior of the container or by applying a higher pressure externally such as by mechanical means or by gas means.

It may also be advantageous in the use of a mobile heating zone to gradually lower the container from the bottom up. If the container is very long, it may not be able to support its weight if it is supported only at its upper regions and can also be supported at the bottom so that it does not lengthen during collapse. If on the contrary you wish to stretch the tube so that it collapses into a cylinder rather than a flat plate, a small tensile force (in addition to gravity) can be applied to the bottom of the container and will produce an object cylindrical.

To prevent rupture of the glass container containing a glass lining, the glass container must have a coefficient of thermal expansion lower than that of the resulting enclosed glass which is obtained when the glass container and its contents containing the radioactive material deposited are heated to sinter the glass lining so as to give an enclosed glass doped with radioactive materials. Silicate glasses with or without small amounts of boron (eg Vycor glass) have low coefficients of thermal expansion and, when the content of alkali metals is increased, the coefficient of expansion increases significantly. It is preferred that the container does not collapse prematurely,

even when the inside is vacuum and the outside is at atmospheric pressure at temperatures at which the enclosed glass lining begins to melt so that a container containing the enclosed glass remains until it is advantageous to collapse the container. In this connection, it is preferred to use a container having a fairly high glass transition temperature (silicate glass and Vycor glass are advantageous). When the particles of the glass lining are heated, they degas to become solid particles below the glass transition temperature or just above the glass transition, as long as the glass is not hot enough that 'there is coalescence of the particles between them. At a slightly higher temperature, the glass particles melt together, that is, there is coalescence, and they become a unitary body of glass which, if operated correctly, is free of bubbles. If the container

11 651956

collapses at a temperature slightly higher than the temperature Tg of the interior molten glass (including the deposited solid materials), the result is a bubble-free final glass product containing nuclear waste. However, if the container is not collapsed until a much higher temperature is reached, there is a risk that the solubility of gases, such as oxygen, in the inner molten glass will decrease in a measure such that the content of this gas, for example oxygen is greater than its solubility in the molten gas because it is under the vacuum used to collapse the container. When the gas (oxygen) content exceeds its solubility at the temperature and reduced pressure of the interior molten glass before the container collapses, bubbles and foam may form in the interior molten glass. Once the tube becomes af-15, its interior is no longer subjected to a vacuum, but is subjected at this time to external pressure; thus, the solu-tility of the gases in the interior molten glass increases and the danger of bubble or foam formation is reduced. Preventing the formation of bubbles or foam requires fairly precise choices of the glass transition temperature of the container and the glass transition temperature of the interior glass composition comprising the deposited radioactive solids. Again, if the interior glass composition is too soft for a Vycor glass or fused silica glass container, the collapse temperature of the container can be lowered by using a glass container such as Pyrex. Obviously, the preparation of compositions having any desired glass transition temperature is well within the skill of the art and any means available can be used to obtain glass compositions having temperatures TG suitable for the container and the interior lining of glass. The glass composition of the container should melt at higher temperatures than the interior glass composition comprising the deposited radioactive solids; that is, it must have a higher glass transition temperature and must be able to collapse only after sintering the interior glass composition. The presence of interior bubbles is not intolerable in many cases; 4o however, if the absence or reduction of bubbles or foam is desired, the temperature TG of the glass compositions used must be chosen as explained above.

When a porous glass with a high silica content (more than 90 mole percent Si02) and 45 with a low alkali content (less than 0.5 mole percent Na20) is used as the filling: (a) Pyrex glass tubes are sufficient at too low a temperature to allow sintering of the lining; and (b) Vycor glass tubes have the following disadvantages:

(1) The coefficient of thermal expansion is so low that it can only be matched with the interior glass when the load is very low (for example less than 5% by weight for the British composition, see example 25 ).

(2) Due to the high subsidence temperature (about 1300-1400 ° C), this can result in volatilization ss of Cs and other nuclear waste.

Although nuclear waste containers made of Pyrex glass and Vycor glass can be used for many applications as indicated in the examples, other compositions have preferred properties. The preferred container is produced: a) by preparing a porous glass container, such as a tube, as described in the U.S. Patent. No. 4 110 006 from column 10, line 50 to column 16, line 36, and b) by doping this porous glass container with at least one dopant such as cesium, rubidium, strontium and copper. The doping could be carried out by one or the other of the two following methods:

1) The preform is immersed in a solution containing the doping ions at a pH between 9 and 13.5, preferably

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between 10 and 13, for a time which depends on the thickness of the wall and the desired concentration of dopants. Typically, the duration of the immersion is between 1 hour and 7 days. The pH of the solution is preferably adjusted with NH4OH. For a maximum ion exchange rate, the solution is saturated with the desired doping ions. Usually the dopants are introduced into the solution in the form of nitrates. However, chlorides and carbonates can be used.

2) The porous preform is immersed in a solution of dopant or of a doping compound. Once the dopant concentration is uniform throughout the preform, the dopant is precipitated by lowering the temperature. The preform is immersed in a dopant-free solution. The dopant is allowed to partially dissolve and diffuse out of the matrix. Only the dopant precipitated near the outer surface is removed in this step.

In these two methods presented by way of example, the doped porous preform is then dried and heated to the temperature of collapse of the pores. The drying must not significantly modify the distribution of the dopant according to the teachings of the E.U.A. n ° 4 110 096 nor the shape of the container. When the pores collapse, the container changes its appearance, going from an opalescent to a transparent appearance, without significant modification of the shape other than the contraction of its linear dimensions by about 20%. In addition, the dopant compound is used in an amount such that a dopant concentration of between 0.5 and 6 mole percent is obtained in the form of its oxide in the resulting contracted glass product. The porous glass preform usually contains up to 8 mole percent of B203, including other constituents, for example alumina (if any).

Under these conditions, the resulting contracted container will be characterized by a minimum SiO2 content of 86 mole percent. In a preferred aspect, this container will be characterized by at least about 90 mole percent of SiO2, thereby improving the chemical durability of the glass.

Of the two above methods for introducing the dopant into the porous glass, method 1 is preferred. The concentration of the dopant is very uniform throughout the cross section of a preform doped according to method 1. This high uniformity also allows the preparation of the container by conventional glass blowing techniques. In Example 27, for example, the glass tube produced by method 1 (ion exchange method) is heated and one end is closed without breaking.

Since the preferred nuclear waste container should have both a lower viscosity (lower slump temperature) and a higher coefficient of expansion than a 96% SiO2 glass, the addition of alkaline dopants seems appropriate. It has been discovered that at concentrations greater than 85 mole% SiO2 and less than about 5 mole% alkali, the chemical durability of Cs or Rb glasses is greater than that of Na or K glasses of comparable composition . At room temperature, for 2 mole% of alkaline dopant, glass, a sodium glass is 1000 times more durable than a cesium glass and, for cesium and rubidium at 100 ° C, rubidium glass is 10 times higher than cesium glass. The chemical durability was measured for cesium and rubidium glasses by measurements of leaching rate in water with a pH of about 5.6 and at 20 ° C. It has been found that the leaching rates are less than 10 ~ 9 g of silica per cm2 of exposed surface of the sample and per day after an immersion period of 20 days. It has excellent chemical durability. However, although high chemical durability is obtained with a rubidium dopant, a cesium dopant is preferred because of the much lower cost of cesium. Ele12

divalent elements which can advantageously be incorporated at the same time as Cs and / or Rb are Sr and Cu.

In choosing the dopant and the concentration, one should not only consider the chemical durability, but also the harmonization of the coefficient of thermal expansion and of the temperature of collapse of the container with the sintering temperature of the nuclear waste powder. Those with normal experience in this technique can obtain such harmonization by independently adjusting the following variables: composition of nuclear waste, charge of nuclear waste in the material inside, compositions of dopants and concentrations of dopants in the container. However, some of the product can still break, allowing the material inside to be exposed outside. Due to the large surface area of the filling glass which is still covered by the container glass (coating), there is still a very significant reduction in the leaching rates of nuclear waste in water, despite the presence of this coating broken. Thus, 2ocela is still considered as a waterproof seal.

In the context of the present invention, cation exchange particles in a glass container can be used to remove dissolved and undissolved radioactive solids from very dilute solutions of these materials. For example, solutions containing only 1 ppt (part per trillion) based on the weight of the solution, i.e. 1 part by weight per 1012 parts by weight of solution of radioactive cations can be purified. Solutions having less than 0.01 microcurie of radioactivity per cm3 as well as more concentrated solutions, for example, those having 1 or more curia of radioactivity per cm3, and solutions having between 0.01 microcurie and 1 curia of radioactivity per cm3 are effectively treated by the present invention.

In a typical nuclear reactor, there are several sources of radioactive waste as described above which must be safely contained. They include very dilute liquid waste streams which may contain dispersed radioactive solids as well as dissolved radioactive cations; concentrated liquid waste which 40 may contain radioactive cations, radioactive anions and radioactive solid matter (this waste is the result of boiling concentration of a primary coolant containing boric acid used initially in the cooling fluid as a chemical reducer of reactivity and of the concentration by boiling of spent regeneration solutions of the common ion exchange beds commonly used); and / or radioactive gases such as radioactive krypton and / or radioactive iodine. Consequently, the present invention comprises a system for the total elimination of radioactive waste in which a glass or porous silica gel in particles having oxy-alkali metal groups, oxy-metal of group Ib and / or oxy ammonium bound to silicon is packed in a cation exchange column which preferably is a column of fusible glass. The particles 55 of glass or silica gel can be kept in the column by means of a porous closure device such as glass wool or a porous disc in its lower end and, if desired, in its upper end as well. In addition, the porous and / or non-porous glass particles 60 can be mixed with the glass or ion exchange silica gel particles in the column to provide an additional outer surface on which dispersed solid particles do not being not deposited can deposit. It is preferred that the porous silica glass or gel is finely divided and sieved to an appropriate size so as to maximize the speed of the flow of the radioactive waste stream through and between the particles of the glass or porous silica gel and also to minimize the duration of the e

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change ions. First, the diluted stream of radioactive waste is passed through the column and the radioactive cations in solution are replaced by cation exchange with the cations of alkali metal, group Ib metal and / or ammonium present in the glass or porous silica gel, to chemically bind the radioactive cations to the glass or to the silica gel. If the diluted stream of radioactive waste is to be reused as the primary coolant, it is conventional to add lithium ions as a corrosion inhibitor. Consequently, it may be advantageous to use a porous silica glass or gel having oxy-lithium groups bonded to silicon so that lithium ions (which do not become radioactive as do sodium dions) are released into the coolant stream while the radioactive cations are removed. In addition, the radioactive solids dispersed in the dilute stream of radioactive waste can be separated by mechanical filtration on the porous glass or silica gel particles in the column when the stream passes through and between the particles. To keep the ratios of the solids in the radioactive waste stream to the porous glass or silica gel small enough to maintain the filtration action as the solids accumulate on the porous glass particles or silica gel, fresh porous glass particles or silica gel can be added to the column.

Once the ion exchange capacity of the column has been exhausted by the dilute stream of liquid radioactive waste, the column can be dried and the concentrated liquid radioactive waste (containing liquid) can be added to the column. concentrated boric acid, for example, at a temperature of 100 ° C). Thus, the pores of the glass or porous silica gel can be filled with radioactive solid materials, cations and anions contained in concentrated radioactive waste. The excess boric acid present between the particles of the glass or porous silica gel can then be removed by washing with cold water (below 30 ° C.) and the particles can be dried to deposit the radioactive solids, cations and anions in glass pores or porous silica gel using the techniques taught in the EUA patent n ° 4 110 096. Then, the column can be evacuated to remove the decomposition gases. Then, the radioactive gases can be introduced into the glass column and the column can be heated to collapse the glass pores or porous silica gel and to collapse the glass column, so as to immobilize and trap the cations radioactive activated by exchange, the radioactive solid matter on the outside of the porous particles of glass or silica gel, the solid matter, the anions and / or the radioactive cations deposited in the pores of the glass or gel of porous silica and the radioactive gas contained in the glass column. Appropriate pressure differences can be used to facilitate collapse of the glass column. Heating can be continued so that the porous glass or silica gel particles stick to each other to further trap the radioactive interstitial solids between the particles. On cooling, this results in a very durable solid material which very effectively contains the radioactive waste introduced into the glass column.

Since some of the nuclear reactor currents can be basic, some elements in the radioactive waste are present in the form of anions, for example chromium, molybdenum, praseodymium and cerium anions, which obviously must be immobilized too. One way to do this is to pass the basic stream of radioactive waste through a column of ordinary ion exchange resin. The column is regenerated with a non-radioactive base, for example ammonium hydroxide. The effluent from this regeneration contains a fairly high concentration of radioactive elements and is concentrated by boiling in a boiler to obtain a reduced volume of 5 basic radioactive waste. When the basic radioactive waste concentrated in the bottom of the boiler is acidified under reducing conditions, some of the anions, for example those of Cr, Mo, Ce and Pr become cations which can be subjected to an ion exchange and removed by the porous glass co-columns mentioned above. The material remaining at the bottom of the boiler is called the concentrated solution or raffinate which remains after the solution has been boiled, and may contain solids. This material can be molecularly packed into the porous glass to become a very durable solid product containing waste.

There are many other industrial residues to be removed from waste streams which, although non-radioactive, are very toxic to humans. For example, much publicity has been given to the fact that bodies of water have been contaminated in the past with mercury, cadmium, thallium, lead, other heavy metals, insecticides and organic poisons. . Often the concentration of these toxic substances in the waste streams is very low, which poses the problem of treating large volumes of water containing small amounts of toxic substances. However, overall, large amounts of these impurities actually enter the ecosphere. The present invention can be used to purify these waste streams.

The present invention can be used to concentrate and immobilize radioactive cations in the glass for an extremely long storage period. For example, sintered silicate glass loaded with radioactive solids can be suitably packaged in containers, and disposed of beneath the surface of the earth or at sea. Alternatively, the radioactivity of the glass product sintered container containing radioactive solids can be used in devices or instruments suitable for various applications, such as for destroying microorganisms, for example in food preservation, or for sterilizing sewage or any other application where radioactivity can be usefully used.

A typical range of radioactive solids content of the glass products according to the present invention resulting from the treatment of low level radioactive waste is about 1 ppb to 20,000 ppm of the glass product . The content of radioactive solids in glass products resulting from the treatment of waste with a high level of radioactivity can be up to about 30% by weight or more, for example is between about 2% by weight and about 30% by weight. The glass products according to the present invention which are to be used as radioactive sources can have solids contents within the ranges mentioned above.

In general, the glass articles according to the present invention comprise a first portion of non-porous glass and a second portion of non-porous glass surrounding the first portion. The first portion contains trapped and immobilized radioactive materials and the second portion contains other trapped and immobilized radioactive materials. The radioactive materials in one of these portions are derived from radioactive materials that were soluble in a nuclear waste solution (radioactive waste) and the radioactive materials in the other portion are derived from 65 radioactive materials that were insoluble in this nuclear waste solution. For example, the radioactive materials in the first portion are derived from materials that were insoluble in radioactive waste.

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As another example, the radioactive material in the first protion is derived from radioactive materials which were soluble in radioactive waste.

In addition, the glassware according to the present invention may include a third portion of non-porous glass which surrounds the second portion, and the third portion is free of radioactive materials. The radioactive materials in the new glassware are described above. Also, the insoluble radioactive materials can be metallic precipitates from the family of platinum group metals. The glass article may be cylindrical, ribbon-shaped or any other desired shape.

The following non-limiting examples will clearly show how the invention can be implemented. Unless otherwise specified, all solutions are aqueous solutions. The "aqueous ammonium hydroxide" or "NH4OH" used in the examples contains about 28% NH3, ppm means parts per million parts of solution, ppb means parts per trillion parts of solution, ppt means parts per trillion parts of solution, all parts and percentages are by weight and all temperatures are given in ° C. For security reasons, all of the simulated radioactive waste solutions used in the examples were actually non-radioactive; however, radioactive solutions of the same type can be substituted for them and concentrated and encapsulated in accordance with the following examples.

Example 1

Preparation of particles and glass tubes

A. A molten glass is formed in a platinum crucible at 1400 ° C from sand, boric acid, sodium carbonate and potassium carbonate, the glass having a nominal composition of 3.5 mole percent of Na20.3.5 moles percent K20.33 moles per tooth of B203 and 60 moles percent of Si02. The molten glass is drawn vertically and solidified into cylindrical rods having a diameter of about 0.8 cm and a length of about 100 cm which are then ground in a stainless steel cylinder with a stainless steel bar. The resulting powder is sieved and the fraction between sieves of 0.5 and 0.105 mm mesh size is chosen for use in some of the following examples.

B. Tubes are formed by pulling the glass described above and applying a small internal pressure. Tubes are formed which are sealed at one end by removing internal pressure during the pulling operation. Tubes open at both ends are formed while maintaining internal pressure during the entire stretching and cutting operation. The tubes are formed with an outside diameter of about 1 cm and a wall thickness of about 0.15 cm and are cut to about 5 cm in length.

Example 2

Preparation of porous glass tubes

A base glass tube having a sealed end and an open end is prepared as described in Example IB. The tube is then heat treated in an electric oven at 550 ° C for 110 minutes to cause proper phase separation. The tube after the heat treatment is annealed by slow cooling to room temperature and is leached to form a porous tube by immersion in a 3N HCl solution saturated with NH4Cl at 95 ° C for two days. The porous tube is then immersed in hot water for one day to wash the residue from the leaching operation and it is then kept in a desiccator until the pores are dry, by removing the water from it. washing. The resulting porous glass tuve has a nominal composition of 5 mole percent of B203 having pores in mutual communication and an internal surface of approximately 100 m2 / g. The surface of the resulting porous glass tube is saturated with groups = SiOH.

5

Example 3 Preparation of a Porous Glass Powder

Glass rods are prepared as described in Example IA. Before grinding the glass rods, they are heat treated at 550 ° C for 110 minutes and then they are ground to form glass powder. The glass powder is then sieved and the fraction passing through a sieve of 0.5 mm mesh size, but not through a sieve of 0.105 mm, is leached in a 3N solution of HCl at approximately 95 ° C. for about six hours. The glass powder is washed with deionized water for approximately 24 hours at approximately 25 ° C. The resulting porous glass powder has a nominal composition of 95 mole percent Si02.5 mole percent B203, has pores in mutual communication and has an internal surface of about 100 m2 / g. The surface of the resulting glass is saturated with SiOH groups. The porous glass powder is dried in a beaker on a hot plate at about 150 ° C.

25 Example 4

Use of a porous glass tube to concentrate and encapsulate

A dry porous glass tube having an open end and a closed end, prepared as described in Example 30 2, is impregnated with a solution containing dissolved CsN03 and particles of A1203 simulating a nuclear waste fluid. The CsN03 solution contains 67 g of CsN03 (which could be radioactive) dissolved in 23 cm3 of water at 100 ° C and 10 g of A1203 representing suspended solids (which could be contaminated with radioactive isotopes. active). The inside of the tube is filled with the dopant solution and the solution is allowed to penetrate the pores. Part of the solution in the tube is allowed to pass through the walls of the tube to the outside of the tube and is collected for use in other tubes. This is continued until the interior of the tube is substantially empty of the solution. The solid particles of A1203 suspended in the solution, however, being much larger than the pores of the walls of the tube, are retained in the interior of the tube. In addition, the solution containing the dissolved CsN03 fills the pores of the walls of the glass tube. The resulting charged porous tube is then immersed in methanol at 0 ° C so that the CsNO3 dissolved in the solution present in the pores precipitates in the pores. The interior and exterior surfaces of the loaded tube so are soaked in clean methanol at 0 ° C for 24 hours, while methanol is often changed, resulting in thin layers on both the exterior and interior surfaces of the tube in which the concentration of precipitated CsN03 is lower than the concentration of precipitated CsN03 55 deeper in the glass. (That is, the inner and outer surface layers or regions contain about one-fifteenth of the concentration of CsN03 from the regions deeper in the wall of the tube).

"O The porous tube is then removed from the methanol bath at 0 ° C and placed in the molten silica glass tube, substantially non-porous, of larger diameter (3.5 cm) having an open end and is dried under vacuum at 0 ° C for 24 hours. The molten silica glass tube containing the charged porous tube is then allowed to warm under vacuum to room temperature and then placed in an oven in which it is slowly heated to 15 ° C / h at 625 ° C. This heating period allows the pores of the glass to dry further. The

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porous tube loaded inside the non-porous tube is kept at 625 C for 16 hours to ensure that all of the CsN03 is decomposed and that the resulting nitrogen oxides are expelled leaving Cs02.0n then heated to 875 ° C always under vacuum so as to melt the pores and sinter the glass structure of the porous glass tube, thus transforming it into a substantially non-porous glass tube with the cesium (Cs20) trapped as part of the glass structure. The solid material (A1203) remains deposited on the inner tube. The tube is placed horizontally on a graphite block in a tubular ceramic furnace with another graphite block resting on it. It is heated to about 1350 C and the tube collapses under the weight of the upper graphite block, causing the inner surfaces of the tube to melt and seal together, thereby immobilizing and encapsulating both the Cs20 from the initially dissolved CsN03 and the solid particles of A1203 initially dispersed.

Example 5

Use of a porous powder in a non-porous tube for encapsulation

A non-radioactive aqueous solution simulating a foreseeable radioactive waste stream for an existing spent nuclear fuel reprocessing installation and containing 3.06 g of Fe (N03) 3-9H20.1.68 g of Ce (N03 ) 3-6H20, 0.78 g of La (NO3) 3-6H20.0.78 g of CsN03.3.88 g of Nd (N03). 5H20.2.72 g of Zr (N03) 4.0, 42 g of Sr (N03) 2, 0.34 g of Y (N03) 3-5H20 and 5 cm3 of water, with all the elements in solution except Zr (N03) 4 which is present in the form of a precipitate , is poured into a 50 cm3 beaker which contains 5 g of porous glass powder prepared as described in Example 3. The excess solution is decanted and the beaker is heated to 200 ° C. on a hot plate to dry the powder of glass and deposit the dissolved nitrates in the pores of the glass powder and the undissolved Zr (N03) 4 on the exterior surfaces of the glass powder. The charged glass powder is then placed in a Vycor glass tube (Corning 743170-4381) having a nominal composition of 96% Si02 and 4% B203, an internal diameter of 7 mm, an external diameter of 9 mm and a length of 50 cm. The tube is sealed at one end and is connected to a vacuum pump. The tube containing the charged porous glass powder is then introduced into an oven at room temperature under vacuum and heated to 15 ° C / h at 600 ° C for evaporation of any remaining water or any other volatile matter and for decomposition of nitrates. present in the corresponding metal oxide and in nitrogen oxides and for expulsion of nitrogen oxides. After maintaining at 600 ° C for 24 hours, the tube is transferred to a second oven capable of providing higher temperatures. When transferred from one oven to another, the temperature drops to 530 ° C.

The temperature in the second oven is gradually increased from 530 ° C to 1340 ° C over a period of three hours and 25 minutes. The tube is removed and found to have collapsed above the level of glass powder impregnated with the simulated nuclear waste solution. This happened because the oven had too large a temperature gradient and because the tube was inserted too far. However, the end product is a partially collapsed tube that completely encloses the glass powder without cracks in the tube. The non-collapsed lower portions of the tube contain the impregnated glass, part of which is loose powder, part of which melted into blocks and part of which melted and stuck to the interior walls of the tube. There are no ruptures in the walls of the tube and no stress on the walls of the tube is observed under crossed Polaroid slides. The resulting product effectively encapsulates the metal oxides resulting from the metal nitrates present in the initial simulated nuclear waste stream and isolates them from the environment.

Example 6

5 Encapsulation of calcined nuclear waste in a Vycor glass tube for burial

An amount of approximately 1.5 cm 3 of a non-radioactive aqueous solution simulating a stream of radioactive waste predictable for a facility for reprocessing spent nuclear fuel and as described in Example 5 is placed in a Vycor glass tube 50 cm in length which is also as described in Example 5. The solution comprises dissolved nitrates as well as Zr (N03) 4 precipitated as described in Example 5. No addition is made no glass powder. The tube 15 is connected to a vacuum pump by a flexible rubber hose. To avoid excessive bubbling, the tube is placed in an ice bath at 0 ° C and pumped overnight to dry its contents. The next day, the temperature of the tube is 28 ° C and the internal pressure is 20 torr. The tube is transferred to an oven in which it is heated under vacuum in accordance with the heating program indicated in Table 1 below.

Table 1

25 Times

Temperature,

Pressure

(hours: minutes)

° C

Pa

12:45

70

18.3

1:40 p.m.

80

5.3

30 13:50

130

16.7

14:05

155

6.7

2:25 p.m.

190

10.5

2:50 p.m.

190

3.3

15:15

290

6.7

35 15:30

340

10.7

15:40

350

7.3

16:05

450

4.5

17:05

600

2.1

6:10 p.m.

850

2.1

40 20:00

1340

1.9

At 20:00, after 7 hours and 15 minutes of heating, the tube which has collapsed during heating is removed from the oven. From the results presented in the Table above, it can be seen that the maximum pressure is observed at 12:45, 13:50 and 14:25. This seems to be due to the evaporation of the water still in the tube when it is placed in the oven and seems to occur each time when the temperature is raised significantly. If the temperature is kept constant as at 13:40, 14:05 and so 14:50, the pressure is reduced when the water vapor is vacuumed. Another maximum is observed at around 15:30, at around 300-400 ° C, which is apparently due to the decomposition of nitrates to form nitrogen oxides.

The end product is a collapsed Vycor glass tube 55 sealed with simulated calcined nuclear waste (i.e., oxides of Fe, Ce, Ha, Cs, Nd, Ba, Zr, Sr and Y) encapsulated at the inside of the tube collapsed and sealed. There are no cracks in the surface of the collapsed and sealed tube. When we examine the tube under polarized light, we find that it is free of stress. The resulting product can be used for burial in the ground or at sea and can be packaged for this purpose with other similar products in larger containers.

Example 7

65 Use of a non-porous glass powder in a non-porous glass tube for encapsulation of nuclear waste for burial

Pyrex glass (Corning 234030-510) with a composition

651,956

16

Nominal sition of 81% Si02.2% A1203.13% B203 and 4% Na20 (these percentages being by weight) is ground in a stainless steel cylinder using a stainless steel bar. The crushed glass is sieved and the fraction which passes through a sieve of 0.25 mm mesh opening and is refused by a sieve of 0.105 mm is chosen for use. 9.5 g of the selected fraction of Pyrex glass powder are mixed with 0.5 g of porous glass powder impregnated with a stream of simulated nuclear waste and dried as described in Example 5. The mixed powder is further dried in a beaker on a hot plate at 110 ° C for about two hours. Part of this mixed powder is then placed in a 50 cm long Pyrex glass tube having the nominal composition indicated above, an outside diameter of 9 mm and an inside diameter of 7 mm, so that it forms a column 10 cm high. Also, a piece of platinum wire 1 cm long and 1.5 cm in diameter is added to the powder in the tube. The open end of the tube is connected to a vacuum pump and the tube is placed in an oven in which it is gradually heated from about 25 ° C to about 830 ° C in about 4 hours and 35 minutes. The finished product shows some cracks after removal from the oven. The cracks appear to be internal and do not extend to the outside surface of the collapsed Pyrex glass tube. The resulting product effectively encapsulates glass powder containing simulated radioactive waste and platinum which represents the platinum group metals such as Pd, Ru and Rh which are commonly solid materials dispersed in nuclear waste streams. The formation of cracks can be eliminated by harmonizing more closely the coefficient of thermal expansion of the tube and that of its contents. The final product can very well be buried underground or at sea, preferably with other products of the same kind and packaged in a container of larger dimensions for more convenience.

Example 8

Imprisonment of radioactive vapors in a porous glass rod

The purpose of this example is to show that gaseous products from simulated nuclear waste which are heated in a glass tube can be trapped in a porous glass rod. 6 grams of porous glass powder prepared as described in Example 3 are mixed in a beaker with 2.76 g of CsN03.3.17 g of Cu (N03) 2, 73 cm3 of H2O and 25 cm3 of NH4OH for 20 , 5 hours and washed for 24 hours. The impregnated porous glass powder is dried on a hot plate at a low temperature (approximately 200 ° C. for approximately one hour). Next, the sample is placed in a Pyrex glass tube identical to that described in Example 9 and having a closed end and a narrowing located approximately 11 cm from the closed end. The powder forms a column 4 cm high in the tube. A porous glass rod 12.5 cm in length, as prepared in Example 1 A, having a diameter slightly less than 7 mm is introduced into the tube. The inner end of the rod was reduced by grinding to a frusto-conical shape (which is then washed in an HF solution to release the pores) so that a fairly good seal is formed between this end of the rod and the narrowed part of the tube. The tube is partially placed vertically inside an oven so that the upper half of the rod is outside the oven. The heating is carried out in accordance with the time, temperature and pressure program indicated in Table 2 below. At the end of the heating cycle, the tube is removed from the oven. The lower part of the tube sagged up to 1 cm below the frustoconical end of the porous rod. The 5 cm protion of the rod, which was half inside and half outside the oven, is slightly yellow in color, which indicates the condensation of copper vapors, while all the other parts of the tube and the rod are substantially colorless. This indicates that the simulated radioactive vapor, i.e. copper vapor, escaping from the porous glass powder impregnated during heating was trapped in the approximately 5 cm portion of the porous rod and couldn't leave the tube. The resulting collapsed tube product effectively encloses the simulated radioactive waste in a resistant glass structure.

20

25

Table 2

Time

Temperature

Pressure

(hours: minutes)

° C

Pa

2:30

20

0.7

2:31

95

2.9

2:52

95

2.3

3:13

95

1.7

3:43

150

1.7

4:21

260

3.2

9:30 am

580

1.1

10:20

750

1.6

30

The maximum pressure at 2:31 is due to the water which is expelled from the porous glass powder and the maximum at 4:21 is due to the nitrogen oxides produced by the decomposition of cesium and copper nitrates.

35

Examples 9 to 13 Each of Examples 4 to 8 is repeated, except that the corresponding radioactive nitrates are used instead of the corresponding non-radioactive nitrates specified in Examples 4 40 and 8 and that radio-contaminated A1203 -active is used in place of the non-radioactive A1203 specified in Example 4. In each case, the radioactive material is immobilized and encapsulated in the resulting glass product.

45

Example 14

The porous glass powder prepared in Example 3 is then immersed in an aqueous solution of 3.2 to 50 molarity of sodium nitrate-ammonium hydroxide for three days and it is then rinsed in water until until the pH of the rinse water is lowered to around 8. The resulting powder is then placed in an ion exchange column formed from Vycor glass as described in Example 5. A 55 primary radioactive cooling fluid from a pressurized water nuclear reactor installation using U02 fuel coated with stainless steel (containing 4.9% by weight of 235U) is passed through the column. The primary coolant has the composition indicated so in Table 3 below which indicates the radionuclide, the probable source, the probable form and the average concentration of microcuries per cm3. The cationic radionuclides are the subject of an ion exchange with the sodium cations linked to silicon by oxy groups in the powder of 65 porous silicate glass.

17

651,956

Table 3

Radionuclide

Source

Form ^

Average concentration

Average concentration

probable probable

((iCi / cm3)

(ppb) (3)

3h

(1), (2)

Water, Gas

2.4

0.249

14c

1.2 x 10 -5

2.69 xlO-3

24N3

(1)

Cation

1.9 xlO-2

2.18 x 10- "

32P

3.3 x 10 "5

1.16 xlO-8

35s

3 x IO-6

7.08 x IO "8

51Cr

(1)

Anion

3.7 x 10-4

4.02 x 10-6

54Mn

(1)

Cation, s

2.7 x 1 (H

3.38 x IO "5

55Fe

(1)

Cation, s

1.9 x 10 "4

7.6 x IO-5

59Fe

(1)

Cation, s

1.0 x 10.5

2.03 x IO "7

57Co

(1)

Cation, s

1.2 x 10 "6

1.42 x 10 "7

58co

(1)

Cation, s

4.7 x 10-4

1.48 x IO "5

60co

(1)

Cation, s

7.7 x 10-5

6.81 x IO "5

63 Ni

(1)

Cation, s

8.0 x IO "6

1.30x10-4

64Cu

(1)

Cation, anion, s

5.4x10-4

1.41 x 10-7

89Sr

(2)

Cation

2.8 x 10-6

9.93 x IO "8

90Sr

(2)

Cation

4 x 10 "7

2.84x10 ""

91Sr

(2)

Cation

9.8 x 10 ~ 5

2.76 x IO "8

90y

(2)

s

91y

(2)

s

92y

(2)

s

95zr

(1)> (2)

s

1.7 x 10.5 "

8.06 x IO "7

95NÒ

(1), (2)

s

1.9 x 10 "5

4.83 x IO "7

99mo

(1), (2)

Anion

1.2x10-4

2.54 x 10 "7

103Ru

(2)

s

0

106Ru

(2)

s

0

122sb

(1)

s

1.0 x IO "4

2.62 x 10 "7

124Sb

(1)

s

2.0 x 10 ~ S

1.16 x 10- "

132Te

(2)

Anion, s

131,

(2)

Anion

4.6xl0-s

3.71 x 10 "6

132,

(2)

Anion

133,

(2)

Anion

6.2x10-4

5.5 x 10 "7

135,

(2)

Anion

9 x 10 "4

2.60 x 10 "7

134Cs

(2)

Cation

4.7 x 10 "7

3.62 xlO "7

136Cs

(2)

Cation

0

137Cs

(2)

Cation

1.1x10- "

1.26 x IO-5

140Ba

(2)

Cation

4.7x10 ""

6.45xl0-8

141this

(2)

Anion, s

0

143this

(2)

Anion, s

0

144this

(2)

Anion, s

0

143pr

(2)

Anion, s

110mAg

(1)

s

1.2 x 10.5

2.52x10- "

181Hf

(1)

s

6x10-6

3.70 x 10 "7

182Ta

(1)

s

2.5 x 10 "5

4.01 x 10 "

183Ta

(1)

s

6.2xl0-5

4.34 x10 "7

185w

(1)

s l, 2xl0-5

1.28 x 10- "

187w

(1)

s

3.7 x 10 "4

5.30 xlO-7

85mKr

(2)

Gas

B5Kr

(2)

Gas

88] Cr

(2)

Gas

133xe

(2)

Gas

8.9 x IO "5

4.78 x IO "8

135Xe

(2)

Gas

9 x IO "5

3.54xl0-8

a (l) Neutron activation products of nuclides from the coating of fuel, building materials and water.

(2) Leak from fuel. Mainly fission products.

bGas: probably in the form of dissolved gases s: insoluble solids.

(3) • ppb = part per billion

The radioactive cations of the radionuclides indicated in Table 3 are the subject of a cation exchange with the sodium cations bound to silicon by oxy groups in the porous glass, thus binding the radionuclides to the porous glass by the in -

65 intermediate of the oxy groups linked to silicon and releasing in the cooling solution non-radioactive sodium cations. Radioactive solids insoluble in the coolant are also separated by filtration and

651,956

porous glass particles remain on the exterior surfaces. Additional particles of porous glass can be added to increase the filtration capacity of the ion exchange column when insoluble solids accumulate on the column.

The anionic radionuclides are not notably eliminated in the column and pass with the coolant through the column. The anionic radionuclides can then be removed by treatment with conventional ion exchange resins. During the regeneration of the conventional ion exchange resin once it has been charged, the regeneration solution containing the anionic radionuclides can be concentrated by evaporation and the resulting concentrate can be molecularly piled up according to the methods described in the patent E.U.A. No. 4 110 096 in the pores of the porous glass in the ion exchange column after this porous glass has been notably charged with oxy-cation groups of radionuclides bound to silicon. It is preferred to first dry the charged porous glass so that the anionic radionuclide concentrate can easily enter the pores of the porous glass. The anionic radionuclides can be precipitated or deposited in the pores of the porous glass by the careful drying methods described in the E.U.A. No. 4110 096. Next, the columns containing the porous glass particles can be heated to expel volatile matter, to decompose decomposable substances and expel non-radioactive decomposition products, to collapse the pores of the particles and sinter them. as a unit mass and to collapse the Vycor glass column around the sintered mass so as to wrap the solids separated by filtration and the sintered glass particles containing the cationic and anionic radionuclides in the collapsed Vycor glass column. Although the glass column breaks due to differences in thermal contraction, it still contains and immobilizes the radioactive materials more and forms a product which is much more durable than the cement or metal drums currently used. This produces a durable package of concentrated radionuclides that is highly resistant to leaching by water or other fluids.

Example 15

Use of a porous powder in a non-porous tube for encapsulation

A mixture of non-radioactive nitrates is used for si18

mulate the British industrial waste known as United Kingdom UKM-22 whose composition is reported as oxides in Table 4. Various quantities of nitrates are mixed together in suitable proportions to obtain the appropriate concentrations of oxides indicated in Table 4 Appropriate quantities of nitrates whose total weight corresponds to a total of 2 g of oxides are placed in a 250 cm 3 beaker: 20 cm 3 of H 2 O are added; the solution is stirred and slowly heated to 80 ° C, at which temperature a pale brown solution containing a little undissolved salt is obtained. Then added to the solution 18 g of porous glass prepared as in Example 3 so as to obtain a load of 10% of residual oxides relative to the final glass. The volume ratio of the solution to the glass powder 15 is close to 1: 1. The mixture is dried at 90 ° C. About 3 g of the dry mixture are dried under vacuum in a Vycor glass tube similar to that described in Example 5 according to the following program:

20

Time

(hours: minutes)

T (° C)

Pre

25 9:45 AM

25

25

10:15 AM

65

30

11:15 AM

278

26

11:30 AM

342

38

11:40 AM

383

32

30 11:50 PM

403

68

12:05 PM

520

44

3:20 PM

1300

36

3:45 PM

1310

16

4:15 PM

1310

16

Pressure, mtorrs

35

The finished glass product shows that the pores of the powder and the grains inside the tube have been well sintered. In addition, the tube is completely collapsed, but breaks during air cooling. The finished product is sprayed to increase its specific surface area and is subjected to a leaching test at pH 5.6 and at 70 ° C for various exposure times. The results as reported in Table 5 show that the glass sample has excellent chemical durability.

Table 4

Composition called United Kingdon UKM-22

Oxide

% by weight reported

% in weight

Oxide

% in weight

% in weight

simulated

reported

simulated

AI2O3

19.89

19.89

Zr02

5.57

5.57

Rb20

0.43

0.43

P04

0.93

0.93

Cs20

3.00

3.00

Cr203

2.18

2.18

MgO

24.68

24.68

Mo03

6.89

6.89

SrO

1.25

1.25

Fe203

10.63

10.63

BaO

1.48

1.48

RuOz

2.65

2.65

Y203

0.66

0.66

Ni02

1.40

1.40

La203

1.71

1.71

Poo

1.71

1.71

PreOn

1.67

-

ZnO

1.71

1.71

ND203

7.08

7.08

u3o8

0.23

Replaced by Ce02

Ce02

3.85

3.85

S04

0.39

0.39

19

651,956

Table 5

Chemical durability of the product obtained in Example 15 in deionized water having an initial pH of 5.6 *

Glass component and leaching rate **

Sample Si02 Ln *** Fe Na Cs Sr

Interior and coating sprayed

Interior sprayed

295,127

32 42

<1 11

<4 17

<20 3

<1

♦ Results obtained between day 12 and day 15.70 ° C, 71 hours.

** Leaching rates are in ng of dissolved waste per cm2, of surface area of sprayed product per day. *** Includes all lanthanites.

The leaching rates reported in Table 5 above and in Tables 6 and 8 below were normalized by the amount of the constituent present in the glass. Thus, they represent the leaching rate that the glass would present if the measurement were made only on this constituent. The glass dissolves at the leaching rate of the silica. Sodium, strontium and cesium diffuse to the surface and are initially leached out more quickly. Iron and lanthanites are concentrated on the surface. Finally, the whole glass will be leached at the silica rate.

Example 16

Use of a porous powder in a non-porous tube for encapsulation

A mixture of similar non-radioactive nitrates is prepared, similar to that described in Example 15, to simulate the UKM-22 digging. However, in the preparation of this mixture of nitrates, Zr (N03) 4 and K2Mo04 are dissolved separately from the other nitrates with a sufficient amount of concentrated HN03, the others being dissolved in a 3M solution of HN03 or in water. The two solutions are then mixed together and no precipitate is observed. Phosphoric acid and sulfuric acid are then added to the solution to obtain appropriate quantities of PÒ4S and S04 =. A white gelatinous precipitate appears and does not dissolve when heated to 70 ° C. About 50% of the nitrates precipitate when the solution is evaporated to about 15 cm3. Eight grams of porous glass prepared as in Example 3 are then added to the solution so as to obtain a residual oxide load of 20% relative to the final glass. The volume ratio of the solution to the glass powder is approximately 1: 1. The mixture is dried at approximately 90 ° C for approximately 16 hours. About 3 g of the dry mixture are placed under vacuum in a Vycor glass tube having an outside diameter of 13 mm and a wall thickness of 1.5 mm. The mixture is heated to 600 ° C to 50 ° C / hr. After maintaining at 600 ° C. for 48 hours, the tube is subjected to a temperature jump at 1240 ° C., the pores and the grains inside the tube then being well sintered. The tube, however, does not collapse and bubbles are formed in the waste-glass matrix assembly. In addition, the tube breaks during air cooling. Leaching tests are carried out on the interior of the sample. The results reported in Table 6 show that it has excellent chemical durability.

Table 6

Chemical durability of the product obtained in Example 16 in

1> '...... -rr r

Glass component and leaching rate **

Time (days)

Si02

Fe

Ln ***

N / A

Sr

Cs

0.34

6.190

1150

737

3.61 x 105

3,260

<1000

1.3

963

120

344

<2,500

6.340

300

2.2

550

30

400

<2,500

2,200

<300

3.3

370

49

550

<2,500

2,300

1400

5.7

200

12

<80

<2,500

1,400

120

9.3

260

<13

50

<2,500

680

<320

12.2

220

3

210

<2,500

1,900

150

15.2

230

<13

56

2,000

<320

♦ Results determined at 70 ° C.

** Leaching rates are in ng of dissolved waste per cm2 of surface area of sprayed product per day.

*** Includes all lanthanites.

Example 17

Use of a porous powder in an ion exchange tube for encapsulation

A mixture containing non-radioactive nitrates and porous glass is prepared as in Example 16, but a load of only 5% in oxides relative to the final glass. About 3 g of the dry mixture are introduced into an ion exchange tube which has been prepared as follows: an open porous tube having an outside diameter of 10 mm, a wall thickness of about 1 mm and a length of 20 cm is prepared as in Example 2. The porous tube is then soaked in a solution containing 200 ppm of Cs with enough NH4OH to give a pH of 10 for 18 hours and washed in water at room temperature until to obtain a pH of 7. The tube comprising Cs introduced by

ion exchange is then dried under vacuum and is heated from room temperature to 600 ° C to 15 ° C / h and from 600 ° C to 870 ° C at 50 ° C / h to collapse the pores. One end of the tube is then sealed using a blowtorch before the mixture of simulated waste and porous glass is introduced. The mixture is then heated under vacuum in the tube in accordance with the following program:

Time

(hours: minutes)

T (° C) Pressure, mtorrs

65 11:00 AM 11:20 AM 11:25 AM 11:35 AM

(morning)

22 180 200 252

15 100 100 50

651,956

20

Fortsetzung Time

(hours: minutes)

T (° C) Pressure, mtorrs

12:02 PM 12:10 PM 12:53 PM 1:00 PM 1:20 PM 1:30 PM 1:35 PM 1:47 PM 2:00 PM

(afternoon)

330 470 547 775 875 927 1010 1075 1100

48 36 28 25 24 24 24 24 24

The finished glass article shows that the sag of the tube has been complete and that there are no cracks. The grains inside the tube, however, do not sinter completely. Here, the coefficients of thermal expansion of the tube and the powder have been harmonized. However, complete sintering is not obtained because the temperature of collapse of the tube (approximately 1100 ° C.) is too low for the composition of the nuclear waste and the level of charge that is used.

The composition of the ion exchange tube is measured to be 0.5% by weight of Cs.

Example 18

Use of a pouring powder in a non-porous tube for encapsulation

A mixture of non-radioactive nitrates is used to simulate the so-called West-Valley PW-8a waste, the composition of which is reported as oxides in Table 7. Various quantities of nitrates are first dissolved separately in a solution 3M of HN03 or in water and then mixed in suitable proportions to give the appropriate concentrations of oxides indicated in Table 7. A solution containing appropriate quantities of nitrates plus a few undissolved salts, the total weight corresponds to a total of 4 g of oxides is evaporated almost to dryness and is then mixed with 16 g of porous glass prepared as in i5 Example 3 to give a load of residual oxides of 20% relative to the glass final. The mixture is then dried at 90 ° C. About 3 g of the dry mixture are heated under vacuum in a Vycor glass tube similar to that described in Example 5. The mixture is heated to 600 ° C., then it is subjected to a temperature jump to 1250 °. C approximately, temperature at which the mixture of residues and porous glass sintered completely. The Vycor glass tube does not collapse completely and breaks during air cooling. Leaching tests are carried out on the interior of the sample. The results reported in Table 8 show that it has excellent chemical durability.

Table 7

Composition of so-called West-Valley PW-8a waste

Oxide% by weight% by weight Oxide% by weight% by weight

reported

simulated

reported

simulated

Na20

16.62

16.62

Te02

0.86

Fe203

34.29

34.29

CS2O

1.14

1.14

Cr203

1.36

1.36

BaO

1.85

1.85

NiO

1.74

1.74

Y203

0.05

0.05

p2o5

1.58

1.58

La203

6.05

6.05

Rb20

0.21

0.21

Ce02

12.09

12.09

SrO

1.25

1.25

Pr6On

1.06

1.06

Zr02

5.84

5.84

ND203

3.62

3.62

Mo03

7.54

7.54

Sm203

0.64

0.64

Rh203

0.36

0.36

Eu203

0.17

0.17

Ag20

0.104

0.104

Gd203

0.43

0.43

CdO

0.15

0.15

Table 8

Chemical durability of the product obtained in Example 18 in deionized water having an initial pH of 5.6 *

Glass component and leaching rate **

Time (days)

SO2

Fe

Ln ***

N / A

Sr

Cs

0.34

2800

62

<32

6500

560

223

1.3

905

8

370

2500

2000

<630

2.2

550

25

440

1400

240

370

3.25

430

12

440

1360

1200

670

5.7

200

100

150

870

880

340

9.3

280

<25

150

780

600

630

12.2

313

<1

200

780

780

770

15.2

300

3

120

840

-

620

* Results determined at 70 ° C

** Leaching rates are in ng of dissolved waste per cm2 of surface area of sprayed product per day.

*** Includes all lanthanites.

21

651,956

Example 19 a good quality glass, thus increasing the load by

Using a porous powder in a tube having undergone nuclear waste compared to Example 17, one can lower

ion exchange for encapsulation ser the sintering temperature below the temperature

The porous powder mixed with nuclear waste from sagging of the tube having undergone ion exchange. However,

described in Example 18 is used in a prepared tube 5 an excessive amount of nuclear waste was introduced as in Example 17. The mixture is heated under vacuum to in this experiment and the coefficient of expansion was slight-

600 ° C, then subjected to a temperature jump to 110 ° C too high, causing a small number of cracks,

ron, temperature at which the mixture of waste and glass To obtain completely porous non-cracked products sintered completely. The sintered exchange tube with the ion exchange tubes used in ion collapses completely. However, it breaks during Examples 17 and 19, or should use air-cooled load levels. When examining the intermediate material, for example load levels included, it is found that it has been completely sintered and that it is between 8 and 12%.

VS

Claims (4)

651956 1. Method for preventing the dissemination of toxic material, in particular radioactive material in the environment, characterized in that a mixture of toxic material and a glass lining is formed in a hollow glass container doped with content high in silica, or this mixture is formed in a first container and then at least a portion of this mixture is deposited in a hollow glass container doped with high silica content, this glass container is heated so as to collapse its walls and sealing the container, so that the toxic material is retained and enclosed in the collapsed doped glass container. 2. Method according to claim 1, characterized in that the glass container is a non-radioactive doped borosilicate glass container. 2 3 651,956 Impervious to prevent contamination, heat is transferred from the pressurized primary coolant to water acting as a secondary coolant to form steam to drive turbines to generate electricity. In a typical boiling water reactor, light water circulates through the reactor core (heat source) where it boils to form steam which passes to an outside heat trap (turbine and condenser). In both types of reactors, the primary coolant from the heat trap is purified and recycled to the heat source. The primary coolant and dissolved impurities are activated by neutron interactions. Materials enter the primary coolant through corrosion of fuel elements, the reactor container, pipes and equipment. Activation of these corrosion products adds active nuclides to the primary coolant. Corrosion inhibitors, such as lithium, are added to the reactor water. A chemical agent that reduces the reactivity of boron is added to the primary coolant of most pressurized water reactors to reduce reactivity. These chemicals are activated and add radionuclides to the primary coolant. Fission products diffuse or leak from fuel elements and add active nuclides to the primary coolant. Radioactive materials from all these sources are transported around the system and appear in other parts of the installation through leaks and vents as well as in the output streams of the processes used to treat the primary coolant. The gaseous and liquid radioactive waste is treated in the installation so as to reduce the active nuclides which will be released to the atmosphere and to bodies of water under conditions regulated and controlled in accordance with government regulations. The main processes or basic operations used in the treatment of liquid radioactive waste in nuclear power plants are filtration, ion exchange and evaporation. Liquid radioactive waste in a pressurized water reactor is generally divided into five categories according to their physical and chemical properties as follows: clean waste, dirty or miscellaneous waste, steam generator hunting waste, building of turbines and detergent waste. Liquid radioactive waste in a boiling water reactor is generally divided into four categories according to their physical and chemical properties as follows: high purity waste, low purity waste, chemical waste and detergent waste. Radioactive waste from both types of reactors is very dilute solutions of radioactive cations and other dissolved radioactive materials as well as undissolved radioactive particles or finely divided solids. A practical method for disposing of radioactive materials in a dry solid form with high resistance to leaching and other forms of chemical attack would be usable not only for disposing of radioactive nuclear waste, but also for the manufacture of radioactive sources useful in industry, medicine and the laboratory. Until now, there has been no practical means, safe from misuse, for the safe disposal, storage and immobilization of harmful radioactive waste. Current storage containers do not provide sufficient isolation and immobilization of these radioactive materials, sufficient long-term resistance to chemical attack by the environment and sufficient stability at elevated temperatures. Waste of a low level of radioactivity, that is to say radioactive waste produced in places where reactors are located, is commonly disposed of in the following manner: A) The dead ion exchange resin containing radioactive waste is mixed with cement and poured into 150 liter drums. io B) The residues from evaporators which contain boric acid contaminated with radioactive material and the solutions used to regenerate the ion exchange columns are mixed with cement powder and poured into drums. 150 liters. C) Filters containing particulate forms of radioactive waste are usually enclosed in cement in drums. These cement drums are transported to low-level radioactive waste storage sites and buried at a depth of about 2 meters in the ground. At least one of these storage locations is in the eastern United States of America and is exposed to heavy rain. In Europe, these barrels are buried at sea. In both cases, the water will attack the metal first, then the cement and will expose relatively-25 the radioactive ions for leaching in groundwater or water. like the landfills in the USA are carried out only at shallow depths, contaminated water can easily mix with streams, lakes and rivers, thus entering the ecosphere. The reason for this practice is the assumption that by sufficient dilution the radioactivity becomes harmless. Some of the most serious nuclear wastes are cesium and strontium which are biologically similar to sodium and calcium. They have half-lives of thirty years, which 35 indicates that they should be isolated from the ecosphere for at least three hundred years (ten half-lives). In Bikini, experts considered that the dilution had made the island habitable after decades in which there had been no atomic explosions; however, when the population returned to 40 the island, its health status was adversely affected. We have since realized that plants and animal life biologically reconcile these radioactive elements at dangerous levels. Thus, the “safe” concentration of radioactive waste 45 must be much lower than the accepted values and the cement must be replaced by something more durable. In one aspect, the present invention provides a safe method of replacing solidification in cement of low level radioactive waste. N / A Another technique previously suggested is that known as dry solids which involves fixing the waste in glasses by mixing with vitri-reliable compositions and melting to form glasses. This technique provides a certain improvement with regard to the isolation 55 and the speed of release of the radioactive elements when the outer envelopes or the containers are destroyed. In addition, these glasses remain relatively more stable at high temperatures than plastics and are generally more chemically durable in saline solutions than metals. 6o glasses which have high chemical durability and low conductivity of alkali metal ions and are usable for this prior art are formed at very high temperatures, for example 1800 ° C and above. The prior processes using these vitrifiable compositions melting at high temperatures are economically disadvantageous and moreover pose a dangerous problem due to the risk of volatilization of pernicious radioactive materials. In addition, this process is limited to dry solid radioactive waste and does not 651,956 3. Method according to claim 1, characterized in that the mixture comprises a radioactive solid material and a glass lining. 4. Method according to claim 1, characterized in that the mixture is formed by bringing a fluid containing a radioactive material into contact with a glass lining. 5. Method according to claim 4, characterized in that the fluid is a liquid which contains a dissolved radioactive material and an undissolved radioactive material. 6. Method according to one of claims 3,4 and 5, characterized in that at least a portion of the glass lining comprises porous glass and the radioactive material is deposited on and / or in the glass lining, the glass container is a non-porous glass container of doped borosilicate and the first heating step causes the pores of the porous glass to collapse and then causes the wall of the borosilicate glass container to collapse, so as to retain and enclose the radioactive material in the collapsed borosilicate glass container. 7. Method according to claim 6, characterized in that the quantity of radioactive material contained in the collapsed borosilicate glass container is one part per billion by weight. 8. Method according to claim 7, characterized in that the coefficient of thermal expansion of the non-porous glass container of doped borosilicate is less than 2 × 10 -6 per ° C less than the coefficient of thermal expansion of the glass lining. 9. Method according to claim 6, characterized in that the glass container is a non-porous non-radioactive glass container of doped borosilicate and in that the mixture comprises a fluid of dissolved radioactive solids which are deposited in the pores of porous glass and undissolved radio-active particles which are deposited on the exterior surfaces of the glass disposed inside the container, including the surface of the interior wall of the container. 10. Method according to claim 9, characterized in that the fluid contains radioactive cations and in that the porous glass is formed on its surfaces of non-radioactive cations bonded to silicon by the oxy bonds, the non-radio cations -ac-tives being capable of being exchanged by radioactive cations. 11. Method according to claim 4, characterized in that the fluid is a gas. 12. Method according to claim 6, characterized in that the radioactive material deposited on and / or in the glass lining is nuclear waste. 13. The method of claim 7, characterized in that the heating step inside the glass container creates in it a temperature gradient such that the radioactive gases are prevented from escaping while the products of non-radioactive gas decomposition can be released into the atmosphere. 14. Glass article, obtained by the method of claim 1, comprising a portion of non-porous glass core and a coating portion of non-porous non-radioactive doped glass surrounding the core portion, the core portion containing radioactive materials enclosed and / or immobilized therein, and the coating portion having a coefficient of thermal expansion less than the coefficient of thermal expansion of the core portion. 15. Glass article according to claim 14, characterized in that the coating portion has a coefficient of thermal expansion lower by at most 2 x 10 ~ 6 per ° C than the coefficient of thermal expansion of the core portion. 16. Glass article according to claim 14, characterized in that the coating portion is a non-porous, non-radioactive doped borosilicate glass and in that the portion of The nucleus contains a radioactive material enclosed in it. 17. Glass article according to claim 14, characterized in that the coating portion is a non-porous, non-radioactive doped borosilicate glass and in that the portion of The core contains radioactive material immobilized therein. The objects of the invention are a method for preventing the dissemination of toxic material, in particular radioactive material, into the environment, as defined in claim 1, as well as a glass article, obtained by this method , as defined in claim 14. 30 A problem of considerable importance for the use of nuclear energy is that of disposing of large quantities of toxic materials such as waste with a high level of radioactivity kept in spent reactor storage pools. or produced in the reprocessing of spent fuel from nuclear reactors or produced in the operation and maintenance of nuclear power plants. It is generally accepted that the most promising technique consists in transforming this radioactive waste into a dry solid form which would make this waste chemically, thermally and radiolytically stable. The problem of the stability in the dry solid state of radioactive waste is closely related to the security of human life on ■ land for a period of more than 20,000 years. For example, radioactive waste usually contains the isotopes Sr90, Pu239 and Cs137, the half-lives of which are 28 years, 24,000 years and 30 years, respectively. These isotopes alone pose a significant threat to life and must be put in a stable dry solid form for thousands of years. The solid form of radioactive waste so must be able to keep the radioactive isotopes immobilized during this time, preferably even in the presence of an aqueous environment. Radioactive waste is produced in large volumes and contains long-lived, intermediate-lived and short-lived radioactive ions and some non-radioactive ions. These solutions can be very corrosive and it is difficult, if not impossible, to reduce them to concentrated forms for further processing or storage. The two most common types of fio industrial reactors which both produce waste with little radioactivity are the boiling water reactor (in English Boiling Water Reactor, abbreviated as B.W.R.). and the pressurized water reactor (in English Pressurized Water Reactor, abbreviated as P.W.R.). In a typical pressurized water reactor, slightly pressurized water flows through the reactor core (heat source) to an outside heat trap (steam generator). In the steam generator, in which the primary and secondary fluids are separated by surfaces 4 does not have a solution with regard to significant radioactive volumes in diluted radioactive waste, the container for so many liquid radioactive waste produced by the glass function can be loaded up to 10 microcuries per cm3 or nement and maintenance of nuclear reactors, by practice more, but usually is charged up to 1 microcurie per current storage of spent fuel in masses cm3 of the glass article). The radioactive material is under water and through fuel recovery systems in the form of radioactive solid materials which are trapped in spent reactors. in the glass container. In one aspect, the amount of ma- Due to the general difficulties in handling the radioactive material contained in glassware and radioactive materials and especially due to the danger of at least 1 ppb (parts per billion by weight), in the solid state, volatilization of radioactive materials in the atmosphere, of a multiplicity of radioactive elements, generally attention has drawn to the use of compositions of 10 minus five, and preferably at least ten of the radioactive elements glass with relatively low melting temperatures, active listed below. Preferably, the new articles, that is to say the use of glass compositions having glass te- will contain at least 75 mole percent of SiO2, Si02 levels as low as 27% by weight. Although the in particular more than 89 mole percent of Si02. problem of volatilization of radioactive material either re- From a practical point of view, the upper limit to the quan- duit, it is not completely eliminated. In addition, the composition of radioactive material contained in the glassware resulting glass has chemical durability will be determined, to some extent, by greatly reduced factors and increased rates of diffusion such as: the concentration, form and type of the material ions for the radioactive materials present there, dio-active encapsulated in the glass article, the fraction in vo- The higher this diffusion speed, the lower the pore size, if any, in the glass container, the amount ability of the glass to maintain the radioactive materials as possible immobility of any glass lining in the baking container in its matrix. For long-term glass imprisonment, the various techniques used to encapsulate the ma- radioactive waste, as required by current radioactive standards in the glass container and others, these prior glass compositions are insufficient. factors. Unlike the imprisonment processes in the radioactive materials which can be concentrated, glass, the methods according to the present invention allow 25 encapsulated and immobilized in the glass container according to which one remains master of radioactive materials which tend to present invention include radioactive elements volatilization at high temperatures used in the (natural isotopes and artificial isotopes existing in the form of imprisonment process, thus allowing the elimination of liquids or dissolved or dispersed solids in environmental hazards due to possible release liquids or gases), whether combined or not to the atmosphere of volatilized and avoiding radioactive material ie in the form of anions, cations, a mo- need to provide elaborate techniques and material (non-ionic or non-ionic or elementary form), such as to recapture it and / or to get rid of it again. following elements and their cations: rubidium, strontium,