Method for reprocessing of equipment, contaminated with radioactive impurities and method for production of steel and alloy using debris of metal radwastes

FIELD: reprocessing of worked-out equipment, contaminated with radioactive impurities.

SUBSTANCE: claimed method includes deactivation of contaminated equipment in assembly, disassembling, fragmentation, separation of surface-contaminated fragments, deactivation thereof, classification of metal kinds and groups, and acceptance of mechanical and physical alterations. Fragments satisfied to acceptance results are deactivated without changing form and metal structure thereof and separated into fragments for direct application and for technological update. Fragments not satisfied to acceptance results are used as debris of metal radwastes in metallurgy to produce steel and alloys. Method for production of steel and alloys includes batch preparing, additive introducing during melting process and casting of finished metal. Necessary debris amount to produce desired chemical element content in specific grade of steel or alloy is predetermined followed by calculation of dilution coefficient and upper limit value of debris specific activity. Then debris with specific activity of not more than calculated upper limit value is fed in founding as the base metal and/or addition alloy.

EFFECT: simplified and economy reprocessing method; increased metal amount recycled into national economy, and reduced solid radwaste amount.

3 cl, 2 ex

 

The invention relates to the field of nuclear technology, in particular to the processing of contaminated structural elements to ensure ecological safety of the environment and returning them to the economic turnover of the metals, reducing the volume of radioactive waste. The invention can be used in the decommissioning of outdated equipment manufactures nuclear fuel cycle, including nuclear power plants and reprocessing plants, as well as the processing of previously buried in the burial ground surface contaminated MRO.

As a result of activity of the enterprises of the nuclear complex, radiochemical industry, research and power reactors and other facilities using fissile materials for events to remove these objects from the operation, dismantling and technological changes of the objects or their individual components are formed of metal radioactive waste (MRO).

MRO divided into exposed to neutron flux and surface contaminated.

MRO exposed to neutron flux, subject to conditioning with subsequent burial in.

Superficially contaminated MRO subjected to decontamination.

Currently used str is usually used for decontamination are divided into chemical, electrochemical and non-chemical. In General, these methods have a destructive impact on the surface to be cleaned. Often used for decontamination method of remelting, providing waste reduction due to the transfer in compact form, convenient for safe disposal or temporary storage, but in this case violated the shape and changing the structure of the metal fragments.

The main direction of work on the improvement of known methods of decontamination is to increase the efficiency of cleaning the contaminated surface of MRO to levels that allow the transfer of metals into economic circulation in areas of the economy, allowing them limited and unlimited use.

There are various forms of partial decontamination MRO - chemical (RF patents №2078387 and No. 2147780, G 21 F 9/28, respectively in 1997 and 2000, the patent WO 9850922, G 21 F 9/30, 1999, the patent DE 198187772, G 21 F 9/28, 1999), electrochemical (RF patents №2009557, Convention priority of DE, G 21 F 9/34, 1994, No. 2130656, G 21 F 9/34, 1999, DE 4420139, G 21 F 9/28, 1995, JP 3074108, G 21 F 9/28 2000), laser (patent RF №2084978, G 21 F 9/30, the conventional priority FR 1997), the explosion of the combustible gas mixture (patent RF №2146841, G 21 F 9/28, 2000), remelting (RF patents №2145126, G 21 F 9/28, 2000, No. 2159473, G 21 F 9/28, 2000, JP 2951874, G 21 F 9/30, 1999).

All these known methods aimed at solving the problems of improving EF is aktivnosti cleaning surface contaminated MRO and give a increase in the percentage of metal, suitable for unrestricted use in the national economy, but, mainly, as a rule, partial decontamination is designed to reduce the volume of MRO and their safe disposal or temporary storage.

A known method of disposal of nuclear submarines in the Russian Federation patent No. 2140108 G 21 F 9/28, 1996, including decontamination equipment Assembly, disassembly, melted metal in the presence of oslakovic additives to a full meltdown, followed by the separation of radioactively contaminated slag from molten metal, the casting metal and slag, while the surface of the molten metal in the accumulation chamber Inuktitut powdered carbon.

The method allows to exclude the construction of special structures that provide long-term storage of the dismantled energetchikov, and to use metal in the economy directly after melting.

The disadvantage of this method is its complexity due to the use of decontamination remelting process that entails the carrying out of works for the collection and purification of the resulting gases, disposal of waste and periodic decontamination of the equipment used, and does not allow to reuse the undamaged portions in the national economy after cleaning them.

The closest in technical essence allow aemono is a method of processing dismantled radioactively contaminated equipment (RF patent No. 2075126, G 21 F 9/30, 1997), including liquid decontamination equipment Assembly, dismantling and fragmentation of equipment, decontamination fragments, thermal decontamination fragments by burning combustible materials, sorting by types of metals and their activity, the melting of low-melting metals, separation of melt these metals, casting and curing, annealing of the other metals, separating the resulting radioactively contaminated scale, sorting by species and groups calcined metals, transportation them on induction melted in the presence of oslakovic fluxes. Gases formed during thermal decontamination and induction remelting, is removed for decontamination and cleaning.

This method allows you to clear some of the radioactive metals to the level of the established requirements, allowing them to return into the economic turnover in the form of cleared scrap. In addition, as a result of remelting scrap is greatly reduced volume of metal waste weight of waste becomes compact and homogeneous, thus providing more convenient for further treatment of these wastes.

The disadvantage of this method is the length of the processing cycle and its complexity through the use of decontamination remelting process that entails the carrying out of works for the collection and purification of forming the s gases, disposal of waste and periodic decontamination of the equipment used. This method may not provide re-use for its intended purpose or after technological improvements fragments dismantled equipment in the national economy after cleaning them.

A known method for the production of special alloys (Mnesarchus, Vmetro. The problem of radioactive waste management when the dismantling of nuclear power plants in Germany. “Energy management abroad”, the magazine “Electric power stations”, Energoatomizdat, No. 4, 1990, p.19-20), in which melting scrap MRO add non-radioactive scrap, comprising a specific composition of materials. The resulting metal is suitable for the manufacture of limited use, for example, for the manufacture of containers for storage or transport of MRO and other wastes.

This method is used for the manufacture of products from time to time, in addition, it requires special equipment that meets the security requirements of the operating personnel during the remelting of MRO.

The task of the claimed invention is to simplify and cheapen the process of radioactively contaminated equipment, the increase of metals returned to the economy in the process of processors is key, as well as providing the possibility of re-use for its intended purpose or after technological improvements fragments purified equipment in the national economy and, as a consequence, reduce the amount of solid waste sent for long-term storage and disposal.

The task group proposed invention is solved sequentially, both United by a common inventive concept. The second method allows you to use one of the products obtained by carrying out the first method.

The problem is solved in that in the method of recycling of radioactively contaminated equipment, including decontamination Assembly, dismantling, fragmentation, sorting by types of metals and their activity, decontamination fragments according to the invention, after the fragmentation separate surface contaminated fragments, decontamination machine all fragments ways that do not change the form and structure of metals, and maintain their certification on the mechanical and physical changes, fragments, vetted, is subjected to decontamination methods that do not change the shape of the fragments and the structure of their metal to levels limited or unlimited depending on the field of their future use and share them fragments for use in direct the WMD appointment or the exercise of their revision to the desired item products and fragments that do not pass the certification is sent to a scrap metal radioactive waste (MRO) for use as a base metal and/or alloys for the production of steels and alloys by the standards of the steel industry.

The problem is solved in that in the method of production of steels and alloys using scrap MRA, including the preparation of the charge, smelting of steel and alloys with the introduction of smelting alloying additives, the final metal casting according to the invention, before melting determine the number of metal MRO (MMRO)required to achieve the specified content of chemical elements in investment-grade steel or alloy, and the dilution factor from the correlation;

CR=M/MMROwhere

M - the number of the finished product steel or alloy

then specify the upper limit value of the specific activity of the metal MRO (AMROused to obtain a product of formula:

AndMRO=DK×CR where

DK - regulatory activity value of finished products,

Cu - calculated dilution ratio,

and enter the scrap of MRA with specific activity not exceeding the upper limit value AndMROin the smelting as a base metal and/or ligatures.

For reduction of radionuclide gazoobraznoi phase and prevent contamination of equipment scrap MRAO, used as ligatures, is introduced into the melt in solid form.

The claimed methods, the joint General inventive concept, allow high-performance in technical, economic and environmental aspects of the work to be done on the processing and use in the national economy of radioactively contaminated dismantled equipment, as well as previously buried in the burial ground surface contaminated MRO.

The method of recycling of radioactively contaminated equipment is carried out as follows.

Radioactively contaminated equipment, subject to dismantling, pre subjected to decontamination Assembly, i.e. without opening the contaminated internal cavities, but with the localization of radionuclides in a limited volume. Typically, at this stage, use a decontamination liquid. Then this equipment will be dismantled and/or removed previously dismantled equipment from storage of solid radioactive waste and fragmenting, i.e. dismantle equipment to its elements. Fragmentation composite equipment are carried out by using the equipment and tools specified in process maps, and equipment, which has a cylindrical shape (pipelines, bends), using cutters of various diameters depending on the size of fragmentise the s parts, keeping as fragments of the elements according to their functional purpose.

Define the boundaries of the induced activity and share snippets activated MRO and surface contaminated. Activated fragments condition and sent for final disposal.

The main volume of fragmented equipment are of steel construction, pipe casing, valves, valves, pumps, heat exchangers, etc. that can be reused for its intended purpose or technologically improved, for example, by spray coating and the like, either hot or cold perchatki to the desired item products, for example, by perchatki pipe of the same diameter in a pipe of a different diameter, and further used in various sectors of the national economy in accordance with them sanitary norms on the specific activity. All surface contaminated fragments are divided depending on their further use (for example, food industry, medicine or nuclear energy). Followed by sorting on the types of metals and the nature of their activity. The choice of method of decontamination is determined by the nature of radioactive contamination and the properties of the main structural material. Next, carry out the decontamination of the surface Zagra the United fragments ways, do not change the shape of the fragments, the structure of the metal (chemical composition), for example, by chemical or electrochemical methods. Then the fragments certificate nde methods on the mechanical and physical changes, for example, by ultrasonic testing (UT). Fragments, vetted, i.e. without mechanical damage, fatigue cracking of metal, corrosion damage, etc. is subjected to decontamination to levels limited or unlimited depending on the region of their further application. The magnitude of activity of the finished product for limited and unlimited use of specified sanitary rules of radiation safety and is strictly regulated in each country. In Russia at the present time, for unlimited use, this value may not exceed 300 Bq/kg, and limited use up to 1000 Bq/kg

Deactivated fragments are divided into fragments for use for its intended purpose or carry out their revision to the desired item products.

Fragments that do not pass the certification is sent to a scrap metal radioactive waste (MRO) for the production of steel and alloys as the base metal or alloy by the standards of the steel industry.

In all this the groin way carry out dosimetric and radiometric control.

An example of the method.

Technological reactor channel RBMK 1000 was subjected to decontamination assembled, dismantled and fragmented. After dosimetric and radiometric monitoring of selected surface-contaminated fragments. The fragments were sorted according to the types of metals (steel pendant HNWT, pipe of steel 08KH18N10T) and the nature of the activity (main radionuclide cobalt-60) and disabled. Then spent their certification on the mechanical and physical changes. Fragments, vetted, divided into groups according to their areas of intended use. In particular the suspension of the fuel Assembly (FA) of the reactor can be used in the nuclear industry for its intended purpose, i.e. it can be deactivated to the level of restriction. The group, which included suspension, were decontaminated by electrochemical method to the level of limited use, because it is proposed for installation on operating reactors. After dosimetric and radiometric control the level of residual activity amounted to 350 Bq/kg, which is valid for limited use.

Pipe ⊘95×5×2000 of steel 08KH18N10T suitable for further application in the field with the standards for unrestricted use, hence its decontamination was performed to level the unlimited use. The group, which includes pipe, were decontaminated to levels unlimited use. After dosimetric and radiometric control the level of residual activity amounted to 290 Bq/kg, which is valid for the field of unlimited use.

The third group included the fragments that have not been certified and intended for use as a scrap of MRO.

The third group were decontaminated to levels possible use in metallurgy and sent for recycling as scrap, MRA.

Certification fragments was carried out using ultrasonic inspection for compliance with the fragments of the requirements of the specifications and Standards applications. The suspension was certified, qualified and installed on operating reactors. The pipe passed the certification, but due to the presence of fatigue cracks metal was perikatan with concomitant heating of the pipe ⊘90×3×4000 suitable for reuse as a steam pipe cage upper tract reactor BSR. To 1000, other fragments that do not pass the certification, were directed to use in scrap, MRA.

Method for the production of steels and alloys with the use of metal MRO is implemented as follows.

In the smelting alloy steels in charge of the base metal during smelting alloying elements are added, providing tribulationists obtained steels. The alloying additives are quite expensive and are irreplaceable resource. At the same time, low alloy steel in the form of a finished product or of a structural element characterized by a certain chemical composition, can be used in scrap as ligatures and/or additives.

In the process pre-determine the number of metal MRO (MMRO)required to achieve the specified content of chemical elements in specific investment-grade steel or alloy, then determine the dilution ratio CR, which is the ratio of total finished product to scrap MRO (MMRO). Then calculate the upper limit value of the specific activity of the metal MRO (AMROused to obtain a product of formula:

AndMRO=DK×CR.

The values DK (regulatory activity value of the finished product) is strictly regulated by the relevant regulatory documents in each country. According to Russia GOST R 51713-2001, Annex 10 - SP-99 (Basic sanitary rules of radiation safety), paragraph 5.11.3, the value of DK may not exceed 300 Bq/kg for unrestricted use of the finished product. Standards for limited use this value can be C acetelyne above (paragraph 5.11.4).

Next, enter the scrap of MRA with specific activity not exceeding the upper limit AndMROin smelting as a base metal and/or ligatures in the number of MMROnecessary to ensure the specified content of chemical elements in specific investment-grade steel or alloy.

If the residual values of specific activity of metal MRO (AMRO) are small, this scrap of MRA can be used in metallurgy as a base metal (mixture), in which is inserted a sufficient number of “pure” ligatures, providing activity of the finished product, not exceeding the value of regulatory activity (DK).

At all stages of the method are performed dosimetric and radiometric control.

An example implementation of the proposed method of production of steel. (Report Cniichermet, 2001)

CRI-Dermatom were experimental melting-alloy steel IN. As the charge was used scrap metal steel 08U, and as alloying additives, scrap MRO after decontamination steels HNWT and 08KH18N10T with residual activity AndMRO=565 Bq/kg (emitting radionuclide cobalt-60).

To obtain the necessary chemical composition of steel IN requires the following ratio, parts:

Charge (steel 08U) 93-94,5

Ligature:

Scrap MRO (steel HNWU) 1-2

Scrap MRO (steel HT) 4,5-5

On the basis of the specified chemical composition for smelting M=1000 kg this became necessary introduction ligatures in the number, MMRO=55-70 kg According to the calculation of the dilution ratio CR=M/MMRO=1000/(55-70)=18,18-of 14.28. The upper limit of the specific activity of scrap (AMRO)=DK×Cu, where DK is assumed equal to 300 Bq/kg according to Russia GOST R 51713-2001, according to which the DC may not exceed 300 Bq/kg (cobalt 60) with unlimited use of the finished product.

The estimated upper limit activity scrap, which can be used for smelting steel, And isMRO=300×(18,18-of 14.28)=(5454-4284) Bq/kg

Steel IN specified chemical composition and metallurgical technologies into the melt mixture was added the required amount of ligatures (55-70 kg) in solid form to prevent release of radionuclides in the gaseous phase and prevent contamination melting equipment.

The melting of the alloys in the liquid bath of the charge residual activity ligatures diffusely distributed in the total volume of the melt.

Due to the fact that the residual activity of the used metal MRA was only 565 Bq/kg, the specific activity of the final metal ingot was 35 Bq/kg, while valid for unlimited use of material activity by standard - 300 Bq/kg

Thus, the obtained metal, from the point of view of residual radioactivity, fully complies with sanitary standards and has unlimited use.

The use of the proposed group of inventions can simplify the process of recycling of dismantled equipment, reduce the cost and time involved in carrying out the processes of decontamination to levels possible use of the proposed methods of surface contaminated structural elements. The use of metallic elements with the level of residual activity exceeding the normative production of steels and alloys, allows you to return to use in the national economy waste, unused and sent for disposal. This reduces the need for the construction of new landfills (HTR) and released volumes of existing landfills by recycling previously buried in them superficially contaminated MRA. This ensures the reduction of harmful environmental impacts of MRA on the environment, reduces the collective radiation dose of personnel And returns superficially contaminated MRO in industrial turnover, reduces the need for re-entering the metal in the area of nuclear fuel cycle and reduces social tensions in the locations of the burial sites (HTR)./p>

1. The method of recycling of radioactively contaminated equipment, including decontamination Assembly, dismantling, fragmentation, sorting by types of metals and their activity and deactivation of fragments, characterized in that after fragmentation separate surface contaminated fragments, decontamination machine all fragments ways that do not change the form and structure of metals, and maintain their certification on the mechanical and physical changes, fragments, vetted, is subjected to decontamination methods that do not change the shape of the fragments and the structure of their metal to levels limited or unlimited depending on the region of their further use, and divide them into fragments for use on your direct appointment or the exercise of their revision to the desired item products, and fragments that do not pass the certification is sent to a scrap metal radioactive waste (MRO) for use as a base metal and/or alloys for the production of steels and alloys by the standards of the steel industry.

2. Method for the production of steels and alloys with the use of metal MRA, including the preparation of the charge, smelting of steel and alloys with the introduction of smelting alloying additives, the final metal casting, characterized in that the before melting determine the number of metal MRO (M MRO)required to achieve the specified content of chemical elements in investment-grade steel or alloy and the dilution factor from the relation:

CR=M/mMROwhere

M - the number of the finished product steel or alloy, then specify the upper limit value of the specific activity of the metal MRO (AMROused to obtain a product of formula:

AMRO=DK×CR where

DK - regulatory activity value of finished products,

Cu - calculated dilution factor, and enter the scrap of MRA with specific activity not exceeding the upper limit value of AMROwhen smelting as a base metal and/or ligatures.

3. The method according to claim 2, characterized in that the metal MRO as ligatures injected into the melt in solid form.



 

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2 cl, 1 tbl

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

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