RU2442236C1 - The method of soil decontamination - Google Patents

Abstract

FIELD: environmental protection.

SUBSTANCE: invention relates to the field of environmental protection, remediation of the soil contaminated with technogenic radioactive wastes; the method of the soil radioactive isotopes decontamination is as follows: the electrodes are placed into the soil contaminated with radionuclides, then it is moisturized and the electrodes are connected to the source of electromagnetic field; the electrodes are connected to the nanosecond electromagnetic impulses generator; the soil is treated with unipolar electromagnetic impulses (wattage -1 megawatt) during no less than 1 nanosecond at the recurrence rate of 1 kHz, at that the electrodes are arranged in the system of several groups, the distance between the electrodes is to be no less that 1 meter.

EFFECT: innovation allows to treat the soil of the contaminated territories preserving its physicochemical properties due to conversion of the radioactive long-lasting isotopes in stable and/or short-lasting radionuclides.

1 cl, 2 ex

Description

The invention relates to the field of environmental protection, rehabilitation of territories contaminated with technogenic radioactive waste.

A known method of rehabilitation of soil contaminated with radioactive nuclides (RF №2317603, IPC G21F 9/12, declared. 07.08.2006, publ. 02.20.2008). The method includes introducing into the soil a sorbent of radionuclides, taken in an effective amount, taking into account the sorption characteristics and the level of soil contamination, soil decontamination, removing the sorbent with nuclides from the soil.

A known method of rehabilitation of soil contaminated with radioactive nuclides (p. RF No. 2088064, IPC G21F 9/12, 12/03/1995, op. 08.27.1997). The essence of the invention: natural or artificially created sorbents are introduced into the soil, which can extract 100% of strontium 90, 91, 89, cesium 137, uranium 235, 238, plutonium 239 radionuclides from the soil. Sorbents firmly bind radionuclides in their structure. After complete decontamination of the soil, sorbents can be removed from the soil by sifting it, and subsequently sent for burial.

The main disadvantage of these methods is that the sorbent with immobilized nuclides needs to be removed from the soil, for which it is necessary to develop methods for removing the sorbent from the soil. In addition, the disadvantage of the methods should be attributed to their high cost associated with the need for removal, transportation over long distances and disposal of spent sorbent.

There is a known method for the destruction of radioactive waste, which consists in the fact that the nuclei of radioactive waste isotopes are affected by at least two electromagnetic fields whose propagation directions are not perpendicular to each other, the polarization planes do not coincide, and the phases are shifted (RF No. 2172993, IPC G21F 9/00 Z. 07.23.1998, Op.27.08.2001). Such an effect creates a rotating magnetic field upon interference of the fields, in which the isotope core changes its angular momentum, thereby reducing the time of destruction of radioactive waste.

A known method for the treatment of radioactive waste, in which the waste is irradiated with microwave radiation with an energy flux density of more than 5 · 10 ^-3 J / cm ² (RF №2100858, IPC G 21F 9/00, s. 31.07.1995, op. 27.12.1997 ) Achievable result: the decay constant after processing the waste with microwave radiation of the indicated energy flux density increased by about 1% compared with the decay constant before irradiation.

The main disadvantage of these methods is the complexity of the installation and the inability to process large volumes of radioactive waste.

Closest to the claimed is a method of soil decontamination (RF №2059307, IPC G21F 9/12, z. 11.01.1993, op. 27.04.1996). The method involves decontamination using electrodes, one of which is connected to the negative pole and coated with a sparingly soluble hydrated oxide or a hydrated oxide compound having acidic properties, and the other electrode is connected to the positive pole and made of an inert material. These electrodes are placed in soil or hard water. When a constant voltage is applied to the electrodes, a current of one direction passes through the residual solutions, creating the movement of ions. At the same time, passing through a layer of clay rocks, heavy metal cations are absorbed in them in exchange for calcium, sodium, etc. and are fixed in them. The method increases the degree of purification of contaminated soil while maintaining its physico-chemical properties and expanding soil types, the purification of which cannot be carried out in another way.

However, this method has a number of significant drawbacks: some of the pollutants are redeposited in the intermediate layers and can create recurrent pollution due to capillary transfer; in the presence of groundwater, contaminants may migrate during the treatment process.

The invention is based on a technical problem, which consists in cleaning contaminated soil while maintaining its physico-chemical properties, by converting radioactive long-lived isotopes into stable and / or short-lived radionuclides.

The problem is achieved in that in the method of soil decontamination from radioactive isotopes, which consists in the fact that the electrodes are placed in soil contaminated with radionuclides, moisten it, connect the electrodes to an electromagnetic field source, according to the invention, the electrodes are connected to a nanosecond electromagnetic pulse generator and irradiate the soil unipolar electromagnetic pulses with a power of more than 1 MW and a duration of less than 1 ns, a repetition rate of at least 1 kHz, while the electrodes are organized in a system of several groups, the distance between which is at least 1 meter.

Preliminary moistening of the soil with an aqueous solution of acid or alkali and treatment with powerful nanosecond electromagnetic pulses reduces the degree of its radioactive contamination, which is due to the conversion of long-lived radionuclide isotopes into stable and / or short-lived radionuclides.

Humidification of the soil with an aqueous solution of acid or alkali and treatment with powerful short electromagnetic pulses leads to the appearance of an electromagnetic field between the electrodes, in which weak interactions can occur. As a result of weak interactions, the electron capture process occurs. In the process of electron capture, the transition of the protons of the nucleus into a neutron takes place, and an antineutrino is emitted, that is, the properties of the excited nucleus can change, which causes them to turn into stable and / or short-lived radionuclides.

In the general case, the electron capture process is described by the formula

,

,

where X is the chemical symbol, A is the mass number, Z is the atomic number, ν is the neutrino.

The inventive method is as follows.

Contaminated soil is treated with an aqueous solution of alkali or acid. A system consisting of several groups of electrodes is placed in a soil contaminated with radionuclides and connected to a generator of nanosecond electromagnetic pulses (for example, a device for generating powerful short unipolar pulses described in RF patent No. 20044064 “Shaper of nanosecond pulses”). The distance between the groups of electrodes is at least 1 meter. Connection to the generator is carried out as follows: the central core of the power cable is connected to one group of electrodes, the braid of the power cable from the generator is connected to the other group. The location of the system, consisting of several groups of electrodes, and the connection of the power cable from the generator are selected experimentally depending on the types of soils, the degree of moisture, and the type of radioactive contamination. Then they are treated with unipolar electromagnetic pulses with a power of more than 1 MW and a duration of less than 1 ns, a repetition rate of at least 1 kHz. The exposure time is chosen experimentally. After certain periods of processing, the content of radionuclides in the soil is determined. After reaching the normative-permissible content of radionuclides in the decontaminated area, the processing process is completed.

Example 1

In this experiment, a sample of soil contaminated with radionuclides taken on the territory of the East Ural radioactive trail was processed. Before treatment, a solution containing ⁹⁰ Sr and ⁹⁰ Y salts was added to the soil. The treatment was carried out in a container of 10 liters. The initial value of soil acidity is 9 pH. The electrodes were placed as follows: the central core of the cable from the generator was connected to the electrode, which was inserted into the container. The braiding terminal was connected to a second electrode, which was under the capacitance. Processing time with nanosecond electromagnetic pulses 30 minutes. Before treatment, the radioactivity of the soil was 177 Bq / kg, after treatment - 102.5 Bq / kg. The degree of purification is 58%, which is a satisfactory result.

Example 2

The treatment of soil contaminated with radionuclides in the region of the East Ural radioactive trail was carried out. To moisten the soil, they were treated with an aqueous alkali solution until the soil moisture reached 60% to 80%. Processing area 10 m ² . A system of groups of electrodes was placed in a soil contaminated with radionuclides, while a central core was connected to one group of electrodes, and a braid of a power cable from a nanosecond electromagnetic pulse generator was connected to another group. The distance between the groups of electrodes was at least 1 meter. The time of one treatment was 30 minutes. The time for complete processing of the site is 2.5 hours. Before treatment, the radioactivity of the soil was 485.2 Bq / kg, after treatment - 302.3 Bq / kg.

Thus, according to the claimed method, an effective decontamination of the source soil from radionuclides is achieved, and the treated soil can be returned to agricultural circulation. This method allows you to quickly and at minimal cost to clean large areas exposed to radioactive contamination.

Claims (1)

The method of soil decontamination from radioactive isotopes, namely, that the electrodes are placed in soil contaminated with radionuclides, moisten it, connect the electrodes to an electromagnetic source, characterized in that the electrodes are connected to a nanosecond electromagnetic pulse generator and process the soil with unipolar electromagnetic pulses with a power of more than 1 MW , lasting less than 1 ns and a repetition rate of at least 1 kHz, while the electrodes are organized into a system of several groups, the distance between which is at least 1 m.