The method of disposal of radioactive materials

 

(57) Abstract:

The invention relates to methods of samosohraneniya radioactive materials of high and medium level of activity in the deeper layers of the lithosphere. In the layers or the domes of rock salt (halite) with a depth of 1-10 km razvarivat hole and cavity-the cavity is injected into it solvent salt and upload capsule with radioactive material that drown in the solution. Under the action of heat from the capsule with radioactive material, the dissolution occurs the bottom of the cavity. The technical result is that the method provides a fast, within 6-10 h, the output material with high activity of the biosphere and in the course of the year samosohranenie to a depth of 5 km, which eliminates the risk of the activity during an emergency. 7 C.p. f-crystals, 1 Il.

The invention relates to the field of radioactive waste management of high and medium level activity, in particular to methods of burial and techniques for secure placement and subsequent self immersion in the deep layers of the lithosphere significant mass of radioactive material, and can be used to release the biosphere excess of radioactive the local way of disposal of radioactive waste (RW), based on samosohranenie fuel waste by melting them rocks and dive into the softened geological environment under the action of gravity containers containing RAO (USSR Author's certificate N 826815 from 23.04.75).

This offer is only conceptual in nature and has a number of fundamental disadvantages associated with technological difficulties of creating containers of large size, and environmental risks of self immersion RAO at the start of the day surface.

Closest to the proposed technical solution is the method of disposal of radioactive material in the deeper layers of the lithosphere, which includes the drilling of wells, the formation of an artificial cavity-cavity, to create a viscous environment, dive RAO in a viscous medium under the action of gravity. The hole and the cavity-cavity fill gray (Byalko A., Khavroshkin O. A method of disposal of high level nuclear waste by deep sinking, RECORD, 91-Proceedings. Sendfi. 1991, p. 486-490).

The disadvantages of this method are the following:

there are no reliable ways of filling deep wells large amount of sulfur, and the development of unique equipment for drilling large (500-800 mm) diameter requires C is idcom condition, with rocks is not known and cannot reliably be predicted taking into account the whole range of long-term effects;

the process of moving a large group of containers (ten thousand units) or vitrified monoliths RAO sulfur in the environment, as well as the accumulation of containers in the cavity occurs within tens of years (30-50 years), which increases the probability of failure of the wellbore and caverns under the influence of rock bursts and other natural and man-made mechanisms;

adhesion of containers in the sulfur melt in the conglomerate (ensemble) is unlikely due to the inevitable formation of fusible sulfides on the surface of the steel container, and the use of ceramic containers is too expensive and cannot provide reliable isolation RAO;

any random deviations thermal equilibrium along the movement of individual containers (local breakthrough groundwater) can lead to blockage of the wellbore, the contamination of the starting horizons and other emergency situations.

The purpose of the invention is the reduction in the duration of operations samosohraneniya RAO, reduce the danger of radioactive contamination of the environment and the economic efficiency of the whole comp is the, when radioactive materials in the deeper layers of the lithosphere, drilling, formation of a cavity-cavity, to create a viscous environment, the accommodation portions and the accumulation of radioactive materials in the capsules are then immersed in a viscous medium under the action of gravity, is carried out in the reservoir and (or) the domes of rock salt with depth array of 1-10 km, and viscous environment is created by pumping in the cavity-the cavity of the solvent salt, ask the activity of a single capsule ensure it is heating up and reaching the temperature gradient between the surface of the capsules and viscous environment 3-10o. The solvent salts may be water-based. The solvent salt may be in non-aqueous base, for example kerosene or ethylene glycol. The solvent can be introduced surfactants that reduce the surface tension of the viscous medium (solution) by 10-30%.

Capsules can be made spherical. Capsules can be made non-spherical shape with a multiply connected surface. Capsules can be made with a multi-layer protective shell. Download speed capsules may be 500-700 units/hour.

The result of radioactive decay of nuclide the stability of the capsules can be a fusion of rock, moreover, if the density of the capsules is higher than the density of the melt rocks, capsules inevitably begin to sink. The melting of rocks of the heat source is a generic method, suitable for a broad class of rocks, but for rock salt, there is another possibility of self immersion. It is when the heat source is in solution (brine) at the bottom of the cavity, and the cavity is filled with a liquid which dissolves the salt, the bottom cavity inevitably eroded (due to more efficient dissolution during heating and as a result of leaking convection processes), and excess salt crystallizes on the upper surface of the cavity, thus there is samozakryvaniya caverns. The process of dissolution is accelerated by convective transfer of a salt solution (brine) from the interface with the solid salt. As a result, the transportation of salt from the bottom of the cavity on its ceiling and side surfaces and, as a consequence, the moving cavity with capsules in the depths of the salt of the array.

To ensure the mode of immersion is necessary that the capsule was located at the bottom or near the bottom. The speed of the dive can be described by the expression:

< / BR>
where Cus- concentration solution spaly and salt solution;

V0- kinetic coefficient of dissolution;

K - coefficient taking into account the shape and dimensions of the capsule.

The temperature gradient between the surface of the capsules and solution should not be less than 3oC, because the process of self immersion slows to a crawl, when the temperature gradient of more than 10oC, the salt dissolving process is greatly accelerated, the dimensions of the cavity significantly increase the dissolution process of the bottom is much faster than crystallization of excess brine from the ceiling of the cavern. The solvent salts may be water-based, water content in the solution can reach 30%. You can use non-aqueous solvent salts, such as kerosene or ethylene glycol, in conditions of limited wettability of the solution will not be flowing out of the cavity through the cracks. When the choice of solvent required - direct temperature dependence of the solubility of salt.

To ensure more effective convection and stable process of dissolution of salt in the brine, you can enter a surfactant that reduces the surface tension of the solution of 10-30%. Reduction of the surface tension less than 10% is not effective and the solution penetrates into the pores and cracks of the array. When you decrease the crystals are made of spherical shape with a diameter of 200-300 mm, however, the process of convective transfer of salt from the bottom increases, if the capsules are elongated and have channels for flow of solution, i.e., the capsules can be multiply connected surface. As the salt solution environment is very aggressive, the protective shell of the capsules is multi-layered and at least one layer is corrosion-resistant.

Download speed capsules should not be less than 500 units per hour, since the increase in the duration of filling increase heat flow and disrupted the geometry of the cavity. With download speeds capsules over 700 units/hour increase in the expenditures on the creation of a special high-efficiency equipment.

For radioactive materials choose layers or the dome of the rock salt (halite) with depth array 1-10 km. to Use arrays salt depths less than 1 km is not environmentally safe, and arrays of more than 10 km on the territory of our country is not. The reliability of the disposal of radioactive waste is defined by:

- choice geological formations, excluding the exchange;

- stability matrix material under conditions of immersion capsules and their subsequent storage on the underlying rocks;

- stability of shells of capsules R> An example of the experimental burial of radioactive waste in rock salt (halite) is represented in the drawing. In a salt dome is created starting well at a depth of 1-1 .5 km with a standard casing pipe having an inner diameter of 220 mm (POS. 1). At the end of the bore is formed in a spherical cavity with a diameter of 5-6 m by washout of halite hot water. The cavity remains filled with a solution with the addition of surface-active substances (Ref. 2).

At the radiochemical plant operating line for the production of spherical capsules with a diameter of 200 mm, containing raw with dissipation of approximately 1 W per capsule, which is equivalent to activity 150-200 Curie. For experimental burial was made 5000 capsules containing a total activity of about 106Curie.

The capsule is transported to the starting position in special containers that do not require cooling. Capsules free fall in the starter cavity through the hole, fill its volume by about 50% (Ref. 3). Filling the cavity spend time shorter than the characteristic time of the separation cavity. The time separation is estimated as the travel time of the cavity to its diameter (6-7 hours). The capsule is lowered into the well through every 7 seconds, for this is hydrated discharge capsules in the trunk. After loading the cavity for several hours leads to heating of the capsules and the cavity begins to sink, after 6-8 hours the cavity breaks off and is implemented process samosohraneniya. The movement of the cavity is controlled with ultrasonic and electromagnetic sensors.

Advantages of the method are as follows:

1. The possibility of using typical wells minimum diameter and a depth of 1-1 .5 km and create the start of the horizon with the aim of improving security and, as a consequence, the minimization of the expenses.

2. Fast - within 6-10 hours conclusion of a material with high activity of the biosphere and their isolation during the year at a depth of 5 km

3. The placement of the array RAO at a depth of 5 km eliminates the danger of release of activity to the surface when force majeure.

4. The use of multilayer capsules, which are highly resistant in the brines increases the safety of disposal.

1. The method of disposal of radioactive material in the deeper layers of the lithosphere, which includes the drilling of wells, the formation of an artificial cavity-cavity, to create a viscous environment, the accommodation portions and the accumulation of radioactive materials is audica fact, drilling of the borehole and the formation of oral cavity is carried out in reservoirs or salt domes with depth array of 1-10 km, and viscous environment is created by pumping the solvent salt, ask the activity of a single capsule ensure it is heating up and reaching the temperature gradient between the surface of the capsules and viscous environment of 3-10C.

2. The method according to p. 1, characterized in that the cavity-cavity pumped solvent salt water-based.

3. The method according to p. 1, characterized in that the cavity of the cavity pumped solvent rock salt on a nonaqueous basis, for example, kerosene or ethylene glycol.

4. The method according to p. 1, or 2, or 3, characterized in that the solvent type surfactants that reduce the surface tension of the salt solution by 10-30%.

5. The method according to p. 1, characterized in that the loading speed of the capsules is 500-700 u/h

6. The method according to p. 1 or 5, characterized in that the capsules are made with a multi-layer protective shell.

7. The method according to p. 1, 5 or 6, characterized in that the capsules are spherical in shape.

8. The method according to p. 1, 5 or 6, characterized in that the capsule is made non-spherical the

 

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