The method of immobilization of radioactive and toxic waste

 

(57) Abstract:

The method includes the steps of concentration, crushing and mixing with fluxing additives, which use a modifier consisting of a mixture of electrically conductive magnet and silicon dioxide in the range of ratios of 0.67: 1,5 between them. Next, a mixture containing 12.5 to 35% of the total mass of radioactive or toxic waste is loaded into transparent to the electromagnetic field of the crucible and operate induction melting and homogenization at a temperature of 1250-1600oThrough direct induction heating. During melting the resistivity and temperature of the melt is stabilized by changes in the share of the modifier, and the ratio between the magnet and the silicon dioxide in the modifier. While the measurement of electrical resistivity of the melt is carried out by means of indications of system instrumentation magnetic field generator. Upon reaching stationarity of the electrical resistance of the melt determine its homogenization, followed by cooling and removing the cooled melt of the final product. Advantages of the invention lie in the fact that the way pozwolenie monolithic material, and the time of implementation of the method is reduced on average 3 times.

The inventive method relates to the field of environmental protection, more precisely to the field of processing of radioactive and toxic waste by fixation in stable solid media. Most effectively the inventive method can be used for immobilization of radioactive waste (RW) containing the actinides (uranium, plutonium, neptunium, and so on), fission products nuclear fuel (rare earth elements, oxides of zirconium, strontium), and ash from incineration of radioactive waste and toxic waste with a high content of oxides of aluminum and heavy metals (over 35%).

The known method include uranium and rare earth elements in glass-like composition by melting glass induction cold crucible described in [1], which includes a mixture of oxides of radioactive waste with stekloobrazovanie and flux in the form of phosphoric acid or of silicon oxide and calcium borate, creating the initial start of the melt, the input to the melt of radioactive and toxic wastes together with stekloobrazovanie and flux, melting, homogenization and cooling of the melt.

The disadvantages of this method are:

low is th solubility of oxides of actinides and rare earth elements (REE) in glassy compositions), resulting in a deterioration of its radiation-protective properties;

the unreliability of steklokompozita when used as a matrix for immobilization of long-lived radionuclides due to insufficient chemical stability in contact with water;

the increased duration of the melting process, caused by mandatory operation of the starting melt when switching on the melter after the forced stop and solidification of the melt in it;

the complexity of management in the implementation of the method due to the necessity of constant control input power high-frequency field to the melt during implementation of the method due to a wide variation of electrical resistivity of the melt.

Known "Method of vitrifying radioactive and toxic waste in the induction furnace [2], including loading stekloobrazuyuschego charge (IN2O3, SiO2, Al2ABOUT3in induction melter with cold crucible, the input to the charge of a limited number of electrically conductive material (magnetite), creating the initial start of the melt, the input to the melt of radioactive and toxic waste along with stekloobrazuyuschego the charge, melting, homog final product, associated with the formation of an heterogeneous phases (due to the limited solubility of oxides of actinides and rare earth elements in glass-like compositions), resulting in a deterioration of its radiation-protective properties;

the unreliability of steklokompozita when used as a matrix for immobilization of long-lived radionuclides due to insufficient chemical stability in contact with water;

the increased duration of the melting process, caused by mandatory operation of the starting melt at a forced stop of the melting and solidification of the melt, as well as limiting the input power to the melt due to the decrease of resistivity in the process of melting;

the complexity of management in the implementation of the method because of the need for constant adjustment of the output parameters of the generator high-frequency electromagnetic field in the implementation of the method due to a wide variation of electrical resistivity of the melt.

The closest to the technical nature of the claimed method and the achieved effect is "a Method of processing radioactive waste mineral wool insulation materials mi additives in the form of FeO in an amount of 10-25% by weight of waste melting the mixture at a temperature up to 1200oC.

Heating and melting the crushed mineral wool contaminated with radioactive caesium, was performed by the method of indirect induction heating in conductive crucible (graphite, metal and others ) in an induction furnace. After melting and cooling of the melt of the final glass-like product with a density of 3.0 g/cm3.

The disadvantages of this method are:

narrowing the scope of the method due to the limitation of the operating temperature of the process is not more than 1200oWith sufficient processing of radioactive waste and toxic ash residues containing heavy metal oxides and aluminum type R23+ABOUT3, R4+O2and R2+O more than 35 wt.% from the total mass of waste and waste that does not contain in its composition of stekloobrazovanie;

the low quality of the final product for immobilization of radioactive and toxic waste containing oxides of actinides and fission products of uranium and plutonium (REE, Zr, Am, Np, Sr, Cs), oxides of heavy metals associated with the formation of an heterogeneous phases (due to the limited solubility of the oxides of the actinides, rare earth elements and RCC;

the unreliability of glassy product when it is used as a matrix for immobilization of long-lived radionuclides due to insufficient chemical stability in contact with water;

the impossibility of control over the degree of penetration of waste in the course of implementation of the method because it is impossible to determine the electrical resistivity of the melt during melting method indirect induction heating in conductive crucible, escape the penetration of the electromagnetic field in the melt;

increased duration of implementation of the method, due to the periodic sequence of the execution of operations (installation of electrically conductive crucible loading of radioactive waste and flux, melting, subsequent prolonged homogenization of the melt without the ability to control its quality, cooling the melt in the crucible, the evacuation of spent and the subsequent installation of the crucible).

The proposed method solves the technical problem by extending the scope of implementation of the method, to improve the quality of the final product and the control of its quality during the implementation of the method, reducing the time of carrying out the process.

The uke is xichnik waste includes the steps of concentrating and grinding waste, mixed with fluxing additives containing metal oxides, load the mixture in the melting, induction melting, homogenizing, cooling and removal of the cooled melt of the final product.

According to the invention hallmarks is that as a fluxing additives use a modifier consisting of a mixture of magnetite and silica in the range of ratios of 0.67...1,5 between them, and the amount of radioactive or toxic waste is 12.5...35% of the total mass of the operation of induction melting and homogenization is carried out at a temperature of 1250. . . 1600oDirect induction heating using a crucible, transparent to electromagnetic fields, according to the testimony of system instrumentation magnetic field generator control the resistivity of the melt during the melting stabilize the resistivity and temperature of the melt by changing how the proportion of modifier in the melt, and the correlation between magnetite and silica in the modifier, and completion of homogenization determine when reaching stationarity of the electrical resistance of the melt, and then perform the operation of release melt.

RA, consisting of a mixture of electrically conductive magnetite (FeO Fe2O3) and silicon dioxide in a mixture of radioactive and toxic waste in the specified proportions, allows to form a conductive flowable melt with operating temperature 1250-1600oFrom waste consisting of refractory and electroconductive oxides, which expands the area of implementation of the method.

Using the method of direct induction heating of the melt during the implementation of the method in the crucible, transparent to electromagnetic fields, such as cold crucible, allows instrumentation magnetic field generator to control the change of electrical resistivity of the melt during the melting and homogenization. Homogenized melt with established electrical resistance with full penetration and dissolution of the original components of the mixture of radioactive or toxic waste and the modifier is a plot of the electric circuit in the induction system, causing its electrical resistance is kept constant. Therefore, the output of the readings of the power supply inductor (the voltage of the load circuit, the frequency of the generator, the grid current of the lamp, okonchanii dissolution process and timeliness of release of the melt. Thus, the use of direct induction heating allows to observe the change of electrical resistivity of the melt during the melting and homogenization, thus ensuring that quality control inclusion of radioactive waste in the matrix during the implementation of the method. In addition, the transaction indicates the timeliness of the release of the melt, which reduces the time of implementation of the method. The above-mentioned operation control of the electrical resistance of the melt is not possible when implementing the method of the prototype due to the shielding of the molten electrically conductive crucible.

The proposed method is continuous, because during the implementation of the method of operation cooling of the melt, due to its release from the melt, are carried out separately, during the execution of the operations of melting and homogenization of the melt, which reduces the duration of the process.

Typical disadvantages for direct induction heating that occurs during the implementation of the proposed method analogues: the mandatory operation of the starting melt at a forced stop of the melting and solidification of the melt, as well as limiting the input power to the melt by reducing its electrocore Romagnolo ferromagnetic magnetite in the composition of the modifier. The change in the amount of magnetite in the modifier at the specified interval correlations with Dukakis silicon during melting and homogenization allows you to quickly affect the resistivity of the melt in the course of work at the waste fraction in the mixture in the range of 12.5.. . 35% of the total mass of the mixture. Created a range of change of the electrical resistance allows to stabilize the generator parameters (voltage on the load circuit, the oscillator frequency, the grid current of the lamp), which makes the regulation of the output parameters of the generator high-frequency electromagnetic field during the implementation of the method in comparison with analogues.

To ensure the quality of the final product the ratio between the magnetite and silica in the modifier changed in the interval ratios of 0.67.. . 1,5 between them. The quality of the final product is achieved through the polycrystalline material in the form ferrosilicates matrices with traces of the glass rim. Ferrosilicate matrix is a microcrystalline aggregate of the products of isomorphic substitution of mineral phases such as garnet (R32+R23+(SiO4)3) and pyroxenes (R2+(Si2O6)), where a large part of R2+and Rand will be outside the above interval, the formation of the polycrystalline matrix of minerals type of garnets and pyroxenes will be impossible, resulting in the final product will be of poorer quality than in the method prototype.

The method is implemented as follows.

Example 1.

Radioactive waste containing uranium 0.01 g/l, PU 0.005 g/l, neptunium 0.03 g/l of rare earth elements 0.8 g/l, Nickel, chromium, molybdenum, barium concentration of each component 0.1 g/l of zirconium 0.4 g/l, are subjected to thermal concentration /is evaporated to a residual moisture content of 10...16 wt.%, prevent dust generation during their loading into the melter.

One stripped off the waste fed to the melt surface modifier consisting of a mixture of magnetite and silica in the ratio of 1.5:1 between them and having a working temperature of 1480oC. the Melt is formed by heating in a high frequency electromagnetic field of a ferromagnetic, electrically conductive magnetite contained in the modifier. During the dissolution of the refractory component of the waste in the initial melt temperature was increased to 1560oAnd the resistivity has changed, as evidenced by the testimony of system control-isoreticular generator 1.73 MHz, the grid current of 1.5 a lamp current of the lamp 6 And the anode voltage 6 kV). Conducting the waste, brought their share in mixture with modifier to 35 wt. % of the total mass of the mixture by reducing the proportion of modifier in the melt at a constant input power of the generator electromagnetic field. This helped to stabilize the resistivity of the melt and to maintain its temperature in the range 1400 to 1600oC. Further conducted joint loading of waste and modifier in the melter with preservation of 35 wt.% waste from the total mass of the mixture and then with the change of the ratio between magnetite and silica to 1:1.3 for stabilizing the electrical resistivity of the melt and its temperature.

The accumulation of the melt in the melting end of the homogenization process was determined by the stationary value of the testimony of system instrumentation magnetic field generator (voltage load circuit of the generator of 0.35, the generator frequency is 1.82 MHz, the grid current of the lamp And 1,1, current lamp to 6.5 And the anode voltage of 5.5 kV).

Produced production of homogenized melt into the receiving container, and loading and melting of the mixture of waste and modifier kept in continuous mode. The melt is about the product.

Example 2.

The ash from incineration of toxic wastes with high content of heavy metal oxides, wt.%: V2O5- 5, Cr2O3- 2, NiO - 3, Co - 3, FexOy8 and Al2ABOUT3- 56 and SiO2- 9, Cao - 5, MLA - 3, K2O - 4, Na2O - 2 is subjected to grinding to particle sizes less than 3 mm and moistened to a moisture content of 10...16 wt.%, prevent dust generation during their loading into the melter.

Shredded waste is fed to the melt surface modifier consisting of a mixture of magnetite and silica in the ratio of 1.5:1 between them, and has an operating temperature of 1460oC. the Melt is formed by heating in a high frequency electromagnetic field of a ferromagnetic, electrically conductive magnetite contained in the modifier. During the dissolution of the refractory component of the waste in the initial melt temperature was increased to 1550oAnd the resistivity has changed, as evidenced by the testimony of system instrumentation magnetic field generator (voltage load circuit of the generator 0,355, the oscillator frequency of 1.73 MHz, the grid current of the lamp And 1,1, current lamp 6,6 A, the anode voltage of 5.5 kV). Proportianal input power of the generator electromagnetic field. This helped to stabilize the resistivity of the melt and to maintain its temperature in the range 1400.. . 1600oC. continued joint loading of waste and modifier in the melter with preservation of 35 wt.% waste from the total mass of the mixture with simultaneous change of the ratio between magnetite and silica to 1:1.2 for stabilizing the electrical resistivity of the melt and its temperature.

The accumulation of the melt in the melting end of the homogenization process was determined by the stationary value of the testimony of system instrumentation magnetic field generator (voltage load circuit of the generator of 0.4, the frequency generator 1,79 MHz, the grid current of the lamp of 0.95 And current of the lamp 7 And the anode voltage of 7 kV). Produced production of homogenized melt into the receiving container, and loading and melting of the mixture of waste and modifier kept in continuous mode. Melt with dissolved toxic waste was cooled to education monolithic polycrystalline product.

When the waste fraction in the melt more than 35% and the ratio of the modifier between magnetite and silica of more than 1.5: 1, the amount of silicon dioxide introduced into R. the ri waste fraction in the melt more than 35% and the ratio of the modifier between magnetite and silica less than 1:1.5 number of oxides, introduced into the melt is reduced to less than 26%, which is insufficient to maintain the desired range of resistivity and temperature stabilization of the melt.

When the waste fraction in the melt is less than 12.5% and the ratio of the modifier between magnetite and silica than 1:1.5 amount of silica in the melt exceeds 53%, which leads to a significant increase of the electrical resistance and excessive increase applied to the melt of electromagnetic power.

When the waste fraction in the melt is less than 12.5% and the ratio of the modifier between magnetite and silica of more than 1.5:1 number of iron oxides in the melt redundant and is more than 53%, which leads to a significant reduction of the electrical resistance and excessive increase in the operating temperature of the melt.

In the result, it was found that:

the method allows immobiliari refractory radioactive and toxic waste (with a content of up to 100 wt.% R2O3) at the melting temperature of 1250 1600...oC;

the final product is a homogeneous material with a porosity of less than 3%, a density of 3.5... of 4.2 g/cm3that has a low rate of leaching is x devices (the constancy of the electrical resistance of the melt) indicates the completion of the dissolution of the components of a mixture of radioactive waste or toxic waste (timeliness of release of the melt) and allows control over the quality of immobilization of radioactive wastes in the matrix during the implementation of the method;

the implementation of the claimed method was reduced in average by 3 times.

LITERATURE

1. Matiunin, Y. I. , Demin A. C., Smelov So Century. the Behavior of uranium and rare earth elements in the glass, synthesized in a cold crucible. - Atomic energy, I. 83, vol. 5, 1997, pp. 330-336.

2. RF patent 2065214, MCI 5: G 21 F 9/16, BI 22, 1996.

3. RF patent 2217460, MCI 5: G 21 F 9/28, 9/32, BI 7, 1999.

The method of immobilization of radioactive and toxic waste, which includes operations of concentration and grinding waste, mixed with fluxing additives containing metal oxides, load the mixture in the melting, induction melting, homogenizing, cooling and removal of the cooled melt of the final product, characterized in that as a fluxing additives use a modifier consisting of a mixture of magnetite and silica in the range of ratios of 0.67:1,5 between them, and the amount of radioactive or toxic waste is 12.5-35% of the total mass process of induction melting and homogenization is carried out at a temperature of 1250-1600oDirect induction heating using a crucible, transparent to electromagnetic fields, and on the testimony of system instrumentation generator e is elektrosoprotivlenie and the melt temperature by changing how the proportion of modifier in the melt, and the correlation between magnetite and silica in the modifier, and the operation is complete homogenization determine when reaching stationarity of the electrical resistance of the melt, followed by the release operation of the melt.

 

Same patents:

The invention relates to the field of nuclear energy and can be used in the conversion of weapons-grade plutonium

The invention relates to the field of nuclear energy and can be used in the conversion of weapons-grade plutonium in MOX fuel

The invention relates to radiochemical production and can be used at the enterprises for processing of spent filters from gas cleaning systems of production of fuel pellets UO2and others

The invention relates to the field of nuclear energy and can be used for the processing of spent nuclear waste fuel, mainly containing cesium and strontium
The invention relates to the field of processing materials with radioactive contamination, and is intended for the decontamination of solid non-combustible surfaces

The invention relates to nuclear engineering and can be used for decontamination of contaminated metal surfaces of the equipment for nuclear power plants
The invention relates to the field of metallurgy, namely the pyrometallurgical recycling: metal and solid mixed radioactive waste and irradiated fuel elements and fuel assemblies containing spent fuel from nuclear reactors

The invention relates to the purification of natural and man-made materials contaminated with radioactive and toxic substances

FIELD: nuclear power engineering.

SUBSTANCE: compaction involves cutting members into fragments using electroerosive destruction of member wall by pulse spark-arch discharges emerging between member and electrode. In addition, high-temperature treatment in oxidizing medium, in particular vapor formed, is carried out. Cutting and heat treatment are accomplished in water.

EFFECT: simplified procedure and increased safety.

3 cl

FIELD: decontamination engineering.

SUBSTANCE: proposed method includes treatment of circuit coolant with acid solutions and washing. In the process treatment with acid solutions is made by chemical loosening for 2-10 h. Dynamic loosening is effected prior to chemical loosening and then coolant temperature is periodically raised in reactor core to 150-200 °C.

EFFECT: reduced time and enhanced effectiveness of decontamination treatment process.

2 cl, 5 dwg, 1 tbl

FIELD: rare, dispersed and radioactive metal metallurgy, in particular hydrometallurgy.

SUBSTANCE: invention relates to method for reprocessing of polymetal, multicomponent, thorium-containing radwastes, formed when reprocessing of various mineral, containing rare-earth elements, Nb, Ta, To, V, Zr, Hf, W, U, etc. Method includes treatment of solution and/or slurry with alkaline agent; introducing of sulfate-containing inorganic compound solution and barium chloride; treatment of obtained hydrate-sulfate slurry with iron chloride-containing solution, and separation of radioactive precipitate from solution by filtration. As alkali agent magnesia milk containing 50-200 g/dm2 of MgO is used; treatment is carried out up to pH 8-10; sodium sulfate in amount of 6-9 g Na2SO4/dm2 is introduced as solution of sulfate-containing inorganic compound; barium chloride solution is introduced in slurry in amount of 1.5-3 g BaCl2/dm2. Hydrate-sulfate slurry is treated with solution and/or slurry containing 0.8-16 Fe3+/dm2 (as referred to startingsolution) of iron chloride, followed by treatment with high molecular flocculating agent and holding without agitation for 0.5-2 h. Radioactive precipitate is separated from mother liquor, washed with water in volume ratio of 0.5-2:1; then washed with sodium chloride-containing solution and/or slurry in volume ratio of 0.5-2:1; radioactive precipitate is removed from filter and mixed with mineral oxides in amount of 0.5-0.8 kg MgO to 1 kg of precipitate. Formed pasty composition is fed in forms and/or lingots and presses with simultaneous heating up to 80-1200C.

EFFECT: filtrate with reduced radioactivity due to increased codeposition coefficient of natural Th-232-group radioactive nuclide, in particular Ra-224 and Ra-228, with radioactive precipitates.

10 cl, 1 ex

FIELD: chemical technology; deactivation and decontamination of radioactive industrial products and/or wastes.

SUBSTANCE: proposed method designed for deactivation and decontamination of radioactive industrial products and/or production wastes incorporating Th-232 and its daughter decay products (Ra-228, Ra-224), as well as rare-earth elements, Fe, Cr, Mn, Al, Ti, Zr, Nb, Ta, Ca, Mg, Na, K, and the like and that ensures high degree of coprecipitation of natural radionuclides of filtrates, confining of radioactive metals, and their conversion to environmentally safe form (non-dusting water-insoluble solid state) includes dissolution of wastes, their treatment with barium chloride, sulfuric acid, and lime milk, and separation of sediment from solution. Lime milk treatment is conducted to pH = 9-10 in the amount of 120-150% of that stoichiometrically required for precipitation of total content of metal oxyhydrate; then pulp is filtered and barium chloride is injected in filtrate in the amount of 0.4 - 1.8 kg of BaCl2 per 1 kg of CaCl2 contained in source solution or in pulp and pre-dissolved in sulfuric acid of chlorine compressors spent 5-20 times in the amount of 0.5 - 2.5 kg of H2SO4 per 1 kg of BaCl2. Then lime milk is added up to pH = 11 - 12 and acid chloride wash effluents of equipment and production floors are alternately introduced in sulfate pulp formed in the process at pulp-to-effluents ratio of 1 : (2-3) to pH = 6.5 - 8.5. Filtrate pulp produced in this way is filtered, decontaminated solution is discharged to sewerage system, sediment of barium and calcium sulfates and iron oxysulfate are mixed up with oxyhydrate sediment formed in source pulp neutralization, inert filler and 0.5 - 2 parts by weight of calcium sulfate are introduced in pasty mixture while continuously stirring them. Compound obtained in the process is placed in molds, held therein at temperature of 20 - 50 oC for 12 - 36 h, and compacted in blocks whose surfaces are treated with water-repelling material.

EFFECT: reduced radioactivity of filtrates upon separation of radioactive cakes.

8 cl, 1 dwg, 1 ex

FIELD: decontamination engineering.

SUBSTANCE: proposed device incorporates provision for admission to inner space of container through hole. This facility is, essentially, vehicle moved by drive. Vehicle traveling gear is free to move from pulled-in quiescent position to working position having large track width (B).

EFFECT: enhanced reliability and safety in operation.

12 cl, 3 dwg

FIELD: decontamination engineering.

SUBSTANCE: proposed pump has housing, pulse line, inlet ball-and-socket valve with ball lift limiter, delivery pipeline with outlet ball-and-socket valve, and control system. Housing communicates with bottom nozzles through pipe and bottom-nozzles chamber that accommodates shaft provided with flap. Shaft is coupled through movable bearing assembly, gear wheel, and toothed rack with turn and immersion depth control actuator of bottom nozzles. Bottom end of inlet ball-and-socket valve seat has slots and mounts in addition spring with movable perforated rack. In addition housing may accommodate top pipe for its communication through ball-and-socket check valve with washing head that has nozzle and pipe union. Stop is mounted in bottom end of pipe union coaxially with respect to hole in check-valve ball lift limiter. Top part of washing head is joined with aid of actuating shaft through movable bearing assembly, gear wheel, and toothed rack with turn and angle-of-tilt control actuators of top nozzle.

EFFECT: enhanced reliability and safety in operation.

8 cl, 6 dwg

FIELD: decontaminating metal wastes by way of their remelting.]

SUBSTANCE: proposed method includes delivery of metal to be decontaminated to water-cooled ingot-forming equipment and decontamination of melt using refining slag. Refining slag in the form of melt is first to be fed to ingot-forming equipment. Then pre-melted radioactive metal wastes are fed at speed affording maintenance of permanent level of molten refining slag within current-conducting section of ingot-forming equipment at which metal ingot decontaminated from radionuclides in the course of remelting can be drawn out.

EFFECT: enhanced economic efficiency of method.

3 cl, 1 dwg

FIELD: hydrometallurgy.

SUBSTANCE: method involves use of alkali solutions containing excess of oxidant, namely alkali metal metaperiodates, at temperature 70-80є.

EFFECT: enabled dissolution of alloy.

2 ex

FIELD: immobilization of heterogeneous radioactive wastes.

SUBSTANCE: proposed method includes production of dehydrated radioactive sediment and filtrate on filtering centrifuge; heating of dehydrated radioactive sediment at 500 - 600 °C; crushing of products of heating into fragments measuring maximum 30 mm; case-hardening of crushed fragments with high-penetration cement solution which is, essentially, mixture of cement having specific surfaced area of minimum 8000 cm2/g and liquid phase at liquid phase-to-cement mass proportion of 0.6 - 1.4; for the final procedure mixture obtained is cooled down.

EFFECT: reduced amount of radioactive wastes, enhanced radiation safety, and reduced power requirement.

2 cl, 1 tbl, 2 ex

FIELD: decontamination engineering.

SUBSTANCE: proposed device has side pipe connection, working liquid feed chamber, drive shaft, and washing head with nozzle. Working liquid feed chamber that has drive shaft and washing head pipe union, both passed therein through packing assemblies, is mounted directly inside storage tank by means of pipeline joined with side pipe connection. Drive shaft is coupled through movable bearing assembly with nozzle tilt angle varying mechanism. It is also coupled through slotted joint, toothed gear, and toothed rack with nozzle turning mechanism mounted on washing head axle and through hinged link ,to external adjustable ring of bearing disposed on packing assembly.

EFFECT: enhanced reliability and safety in operation.

3 cl, 3 dwg

Up!