RU2400849C2 - Method for removing radioactive bituminous compound from bitumen storage house - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: by means of hydraulic cutting which is performed by converging liquid jets directed at the surface outline of the divided section without submersion of jet-forming nozzles to bituminous compound there cut is a piece of bituminous compound. Then the cut-out piece is separated for example by means of special gripping device with a grip hook. After the liquid flows off, the separated piece is placed into the container to be further stored. This operation is repeated for many times by moving the hydrocutter with jet-forming nozzles above the surface of bitumen storage house.

EFFECT: method allows emptying bitumen storage house without heating of radioactive bituminous compound and high mechanical forces.

3 cl, 1 dwg

Description

The invention relates to the field of disposal of solid radioactive waste.

One of the most common methods for fixing liquid radioactive waste (LRW) of low and medium activity levels is curing by incorporating them into bitumen (bitumen), see, for example, RF patent No. 534138 of 05/28/75, IPC G21F 09/16.

As a rule, the bitumen process involves evaporating water from liquid waste and mixing the remaining salts (still bottom) with bitumen at elevated temperatures. When the mixture is cooled, a bitumen compound is formed with waste particles uniformly distributed in it. It uses both bitumen of soft grades, such as BNK-II, and bitumen with the inclusion of soluble polymeric materials in it, characterized by increased viscosity, water resistance and the possibility of greater filling with radioactive waste (see USSR author's certificate No. 550040 from 04.24.75 IPC G21F 9/16).

For radioactive bitumen soft compounds, a method is known for preparing them for pouring into refrigerated containers according to USSR author's certificate No. 502558 of 06.24.74, IPC G21F 9/16 for the purpose of further burial. The essence of this method is to convert a soft bitumen compound into solid blocks intended for direct burial in burial grounds without the use of rigid containers.

Bituminous compounds with inclusions of polymeric materials generated during the immobilization of solidified LRW in them at the preliminary processing stage (liquid evaporation) are classified as SRW (solid radioactive waste).

To date, a significant amount of bitumen compound in the form of SRW has been accumulated at a number of nuclear power plants of the Russian Federation in station storage facilities of bulk type. This poses a significant environmental threat due to increased fire hazard and biological corrosion of bitumen. It is preferable to organize the storage of bitumen compound with immobilized waste in the general SRW storage facilities in special transportable packages (metal container-barrels with a capacity of 0.2 m ³ ), which makes it possible to further remove waste packages from general temporary storage facilities and send them to landfills.

However, the extraction of the bitumen compound from the bulk storage facilities of the nuclear power plant, its packaging in transportable packaging is a certain problem, since no special measures are provided for in these bitumen storage facilities.

Possible methods for extracting a bitumen compound from station storage facilities were analyzed. In particular, it was considered the possibility of imparting a low viscosity (fluidity) to the bitumen compound, which will allow it to be pumped from the bitumen storage for further processing. This, in principle, can be done in two ways:

- liquefying the compound to a viscous state with light solvents such as white spirit;

- heating the compound to technological liquefaction temperatures of 100-200 degrees.

The first way leads to an increase in the volume of the final product by 10-30% (depending on the amount of solvent) and requires a considerable time for its evaporation. The final strength of the material is established only after the complete evaporation of the solvent, which leads to air pollution and increased fire hazard during work.

The second way, regardless of the type of heat exposure (heating with steam, electric heaters, microwave radiation, etc.) is also fire hazardous, and in addition, gaseous radioactive substances are released.

As a prototype of the method of extracting the compound from bitumen storage, the hydraulic cutting method is implemented in the installation for the hydraulic removal of coke from delayed coking reactors according to RF patent No. 2138534 dated 07.15.97, IPC СВВ 33/02. In principle, this method can be used to extract bitumen, but with low efficiency. The fact is that high-pressure water jets in this installation can have a destructive effect on the solid or viscous material of the bitumen composition, but the problem of extracting the separated material remains unsolved.

The task is to create a safe and effective method for extracting a radioactive bitumen compound of high viscosity from a stationary storage area of a large area.

The problem is solved in that in the method of removing a radioactive bitumen compound from a bitumen storage using a hydraulic cutting according to the invention, hydraulic cutting is carried out by converging jets of liquid directed to the surface contour of the separated area without immersing the jet forming nozzles in the bituminous compound, the cut-off section is separated, for example, by a separation, which after draining, the liquid is immersed in a container for subsequent storage, and the hydraulic cutting operation is repeated many times, moving the hydraulic cutting torch with jet forming of the nozzles above the surface bitumohranilischa.

The technical result of the method consists in separating sections of material of a certain shape without heating and large mechanical forces and uncomplicated movement of the hydraulic cutter above the surface of the bitumen storage, as nozzles, unlike the prototype, do not come into contact with the material being cut.

All the described operations are controlled remotely, which excludes personnel contact with radioactive radiation.

In addition, the liquid used during hydraulic cutting and accumulated during operation is diverted and used repeatedly to form cutting jets.

The drawing schematically shows the principle of hydraulic cutting of a radioactive bitumen compound 1, located in bitumen storage 2. Jet forming nozzles 3 are placed around the perimeter of the bottom of the housing of the hydraulic cutter 4 with a given inclination towards each other. On the axis of the housing of the hydraulic cutter 4 moves a remotely controlled grip 5 with a hook 6.

The method is implemented as follows.

Using a crane arrow (not shown), the hydraulic cutter 4 is brought to the surface of the bitumen storage 2 so that the jet forming nozzles 3 remain at a certain distance above the surface of the bituminous compound 1. The gripper 5 is immersed in the thickness of the material and fixed in it using the hook 6. Hydraulic cutting jets directed towards each other, while the cut lines converge to the top of the cone or pyramid symmetrically with respect to the capture. Upon completion of cutting, the gripper 5 is moved up. Piece 7 of the bitumen compound, due to the weakening of the connection with the bulk along the cut lines 8, breaks off and leaves the bitumen storage 2. After draining the liquid, a special container (not shown) is brought under it and release capture 5, shaking the separated piece into the container. The container is shifted to the side, and the hydraulic cutter 4 is moved to the next cutting zone. So gradually, in several passes, the entire volume of bitumen storage 2 is released, with the exception of those residues that cannot be removed using a hydraulic cutter and which are not difficult to remove in another way. The liquid 9, which accumulates on the surface of the bitumen storage, is constantly pumped out and, after filtration, is repeatedly used for hydraulic cutting.

Thus, the proposed method will solve the pressing problem of freeing overflowing bitumen storages at nuclear power plants most safely in comparison with the use of heating and pumping out bitumen compound and economically in comparison with the use of mechanical drilling.

Claims (3)

1. A method of removing a radioactive bitumen compound from a bitumen storage using hydraulic cutting, characterized in that the hydraulic cutting is carried out by converging jets of liquid directed to the surface contour of the separated area without immersing the jet forming nozzles in the bitumen compound, and the cut-off section is separated, for example, by separation, which is immersed in the liquid after draining a container for subsequent storage, and the hydraulic cutting operation is repeated many times, moving the hydraulic cutting torch with jet-forming nozzles above the surface of the bitumohr ilischa. 2. The method according to claim 1, characterized in that the control operations are carried out remotely. 3. The method according to claim 2, characterized in that the liquid used in the hydraulic cutting, accumulated during operation, is diverted and used repeatedly to form cutting jets.

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