Containers for storage, transport and disposal of radioactive waste

Abstract

The present invention relates to the field of nuclear technology. A container for storing, transporting, and disposing of solid radioactive waste comprises a canister made of reaction-sintered silicon carbide with a free silicon content of 3% to 30% by weight, with a fumed silicon carbide layer deposited on the canister's surface. The canister's outer layer is made of metal foam with an open porosity of 60% to 70% and a pore size of 5 mm to 6 mm. The pores are filled with dispersed boron carbide powder of 40 to 50 μm in diameter, thereby protecting the environment from nuclear radiation emitted by high-level radioactive waste. A stainless steel cylinder with a thickness of 1 mm to 1.5 mm, intended to contain radioactive waste, is placed within the silicon carbide canister. A 5 mm gap between the inner surface of the silicon carbide canister and the stainless steel cylinder is filled with boron carbide powder, thereby protecting the environment from nuclear radiation emitted by high-level radioactive waste. The silicon carbide canister is sealed with a lid made of silicon carbide using a reaction welding method. The metal foam used as the metal foam with an open porosity is selected from the group consisting of titanium, aluminum, and copper. The present invention can increase the strength of containers for solid radioactive waste.

Description

Technical Field

[0001] The present invention relates to the field of nuclear technology, in particular to a device for protecting the environment from environmentally hazardous substances, which can be used for storing, transporting and disposing of highly toxic waste, such as radioactive waste from nuclear power plants, nuclear-powered ships, toxic substances in the chemical industry and other hazardous industrial waste. Background Art

[0002] It is known that containers for solid radioactive waste are made in the form of a steel protective shell having a steel container inside which the waste is placed, and the space between the shell and the container is filled with a filler made of formaldehyde resin (US Patent No. 4377509, G21F 9 / 24, 1983).

[0003] A disadvantage of the known container is that the reliability of waste disposal is unsatisfactory, which is related to the insufficient corrosion resistance of the container. A container for solid radioactive waste is known that is made in the form of a multilayer shell, one of the intermediate layers of which is made of silicon carbide (Japanese Application No. 60-022700, G21F 9 / 36, 1985).

[0004] A disadvantage of this container is that the strength properties are unsatisfactory due to the brittleness of the silicon carbide layer, which reduces the operational reliability of the container during technical operations related to loading of waste, moving the container during transport and loading into transport containers made of concrete or cast iron.

[0005] The closest to the present invention in terms of technical essence and the results obtained is a container for solid radioactive waste, which comprises a cylinder made of reaction-sintered silicon carbide with a free silicon content of 3% to 30% by weight, the surface of which is applied a layer of fumed silicon carbide (Russian Patent No. 2146402, G21F 5 / 005, 1998).

[0006] A disadvantage of the known containers for storage, transport and disposal of solid radioactive waste is that the low impact strength of the silicon carbide cylinder is further reduced by increasing the temperature to 1200

[0007] Vitrified waste at 100°C is poured into silicon carbide cylinders, thereby enclosing the radioactive waste within the container. This results in thermal stresses within the cylinders, and residual stresses develop after the vitrified waste cools. These residual stresses reduce the cylinder's operational reliability during the following technical operations: loading the waste, moving the cylinders during transport, and other operations. Furthermore, these containers lack a means of protecting the environment from radiation emitted by the radioactive waste. Summary of the Invention

[0008] The object of the present invention is to increase the strength of containers for solid radioactive waste and their reliability, and to protect the environment from nuclear radiation emitted by high-level radioactive waste (HLW, also called high-level waste).

[0009] The object of the present invention is achieved in the following manner: the outer layer of the cylinder made of reaction-sintered silicon carbide with a free silicon content of 3% to 30% by weight is made of foam metal (foam aluminum, foam titanium, foam copper, etc.), and the surface of the cylinder made of reaction-sintered silicon carbide is covered with a gas-phase silicon carbide layer. In a specific case, the porosity of the foamed aluminum is 60% to 70%, the pore diameter is 5mm to 6mm, and the pores are filled with dispersed 40μm to 50μm B4C powder, which protects the environment from the influence of nuclear radiation emitted by HLW.

[0010] The causal relationship between the achievement of the set objectives and the salient features of the present invention is as follows:

[0011] In order to reduce the impact forces to values ​​that ensure the integrity of the silicon carbide tank in case of impacts that may be experienced during technical operations (loading of waste, moving the container when loading it into a transport container and other actions), the outer layer of the tank consists of a porous structure with an open porosity of 50% to 60% and a pore diameter of 5.

[0012] The foam metal is made of 1.5mm to 6mm, and the pores are filled with dispersed 40 micron to 50 micron boron carbide powder, which protects the environment from the nuclear radiation emitted by HLW.

[0013] In order to reduce the residual stress in the silicon carbide canister, the contact between the molten vitrified high-level radioactive waste and the wall of the silicon carbide canister was eliminated. To this end, the vitrified molten high-level radioactive waste was poured into a steel cylinder placed in the silicon carbide canister. The gap between the wall of the steel cylinder and the canister was 5 mm, and dispersed 100 to 150 micron boron carbide powder was poured into the cylinder.

[0014] The parameters of the outer layer (the thickness of the aluminum foam that protects the can from damage, its porosity, pore size, and the amount of powder placed in the pores) depend on the can's dimensions and weight. These parameters are determined mathematically, with all calculations performed in the ANSIS program. As a starting point, the container weighs 170 kg, the can material has a strength of 270 MPa, and the stress in the can should not exceed 20 to 25 MPa when dropped from a height of 1.2 m. Under these conditions, the calculations yield the following: a 110 mm thick aluminum foam layer with a porosity of 60% to 70% and a pore size of 5 to 6 mm. DETAILED DESCRIPTION

[0015] The proposed design is implemented as follows:

[0016] The following technology is used to manufacture tanks made of reaction-sintered silicon carbide. A blank with the desired geometry is pressed from a filler of the desired recipe by hydrostatic pressure, followed by thermal operations: polymerization at T = 150°C, carbonization at T = 900°C, siliconization at T = 1500°C, thereby obtaining a silicon carbide tank with a free silicon content of 3% to 30% by weight. After sandblasting, a silicon carbide layer is applied to the outer surface of the tank by a vapor phase method. A foam metal layer (foam aluminum, foam titanium, foam copper, etc.) with a thickness of 110 mm is provided on the outer surface of the tank obtained in this way, and a 1.5 mm thick steel shell is provided on top of the foam metal. The pores of the foam metal are filled with dispersed 40 to 50 micron B4C powder (see Figure 1 ).

[0017] Test results

[0018] When dropped from a height of 1.2 m onto a steel plate, a container manufactured according to the prototype ruptured because the stress level caused by the impact exceeded the strength of silicon carbide, which is 250 MPa.

[0019] During the throw test at a height of 1.2 m, at the test center "TSNIIMASH-

[0020] The geometric stability and airtightness of an experimental container consisting of a silicon carbide tank with an outer layer of aluminum foam with a porosity of 50% to 60% and a pore diameter of 5 mm to 6 mm, backfilled with dispersed boron carbide powder of 40 to 50 microns, were experimentally determined on a stand of the "ANALITIKA-PROCHNOST".

[0021] The following results were obtained:

[0022] - During the vertical drop of a container having a silicon carbide canister with a cartridge simulant containing HLW, the container maintained its integrity and airtightness;

[0023] - The container having the silicon carbide canister (the silicon carbide canister having the cylinder containing the HLW) maintained integrity and airtightness during vertical drop while the side surface of the container was kept horizontal;

[0024] - A container having a silicon carbide canister with a barrel containing HLW maintained integrity and airtightness during vertical drop with its side surface at a 45° angle;

[0025] During casting, the stress generated in the barrel does not exceed 10 MPa to 15 MPa.

[0026] The positive test results obtained for the tank when dropped from a height of 1.2 meters indicate satisfactory agreement between the preliminary calculated estimates and the experiments, and that the strength and reliability of the container meet the required characteristics.

[0027] Thus, the container for storing, transporting and disposing of radioactive waste proposed in the present application provides increased strength and reliability for storing and disposing of radioactive waste and protects the environment from radioactive radiation compared to known containers (Russian Patent No. 2146402, G21F 5 / 005, 1998).

[0028] Boron carbide powder placed in the gap between the container with HLW and the inner surface of the silicon carbide can, as well as boron carbide powder placed in the aluminum foam layer, reduced the radiation intensity to background value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A diagram showing containers for the storage, transport and disposal of highly toxic waste, such as radioactive waste from nuclear power plants, nuclear-powered ships, toxic substances from the chemical industry and other hazardous industrial waste.

[0030] The container includes ( Figure 1 ):

[0031] 1: Tank made of reaction-bonded silicon carbide;

[0032] 2: Foam metal with interconnected pores and a porosity of 60% to 70%, the pores of which are filled with boron carbide powder;

[0033] 3: Metal shell;

[0034] 4: Steel cylinders containing high-level radioactive waste;

[0035] 5: High-level radioactive waste;

[0036] 6: Gap between the inner surface of the tank and the barrel;

[0037] 7: Filled boron carbide powder;

[0038] 8: A lid of a can made of reaction-sintered silicon carbide, the lid being welded to the can by reaction welding.

Claims

1. A container for storing, transporting and disposing of solid radioactive waste, comprising: A silicon carbide can made of reaction-sintered silicon carbide having a free silicon content of 3% to 30% by weight, and a fumed silicon carbide layer deposited on the surface of the can, wherein the outer layer of the can is made of a metal foam having an open porosity of 60% to 70% and pores having a pore diameter of 5 mm to 6 mm; wherein the pores are filled with dispersed 40 μm to 50 μm boron carbide powder; A stainless steel cylinder with a thickness of 1 mm to 1.5 mm and made of stainless steel and disposed in the silicon carbide tank for containing solid radioactive waste; There is a 5 mm gap between the inner surface of the silicon carbide tank and the stainless steel cylinder, and the 5 mm gap is filled with boron carbide powder; A lid is provided to seal the silicon carbide can, wherein the lid is made of silicon carbide.

2. The container of claim 1, wherein the metal foam is selected from the group consisting of aluminum foam, copper foam, nickel foam, steel foam, and bronze foam.

3. The container according to claim 1, wherein the boron carbide powder protects the environment from nuclear radiation emitted by radioactive waste.

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