JP2016017930A - Radioactive contaminated marine-soil treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radioactive contaminated marine-soil treatment method capable of inexpensively and safely treating radioactive contaminated soil on a sea bottom with a simple configuration.SOLUTION: The radioactive contaminated marine-soil treatment method includes: a radioactive contaminated marine-soil suction process S100 of raising, above sea, a radioactive contaminated marine-soil containing radioactive cesium on a sea bottom using a pump device; a radioactive contaminated marine-soil heating/concentrating process S200 of storing sucked radioactive contaminated soil in a contaminated soil concentrator and heating and concentrating the soil; and a radioactive contaminated marine-soil discarding process S300 of sealing and discarding the concentrated radioactive contaminated marine-soil remaining in the contaminated soil concentrator together with the contaminated soil concentrator covered with a fireproof block made of artificial ore and silicon carbide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radioactively contaminated seabed soil treatment method.

  Since the Great East Japan Earthquake on March 11, 2011, the nuclear power plant has increased awareness of radioactive pollutants. In order to decontaminate radioactive contaminants, high-pressure cleaning is known in which high-pressure water is sprayed on the target contaminants and the radioactive contaminants are allowed to flow. Therefore, a large amount of contaminated water is generated.

  Therefore, when a large amount of contaminated water is generated, it can be assumed that it flows into rivers and seas. In addition, radioactive pollutants floating in the atmosphere and radioactive pollutants adhering to the ground flow out along the rivers to the sea along with the earth and sand due to rain. Then, soil contaminated with pollutants accumulates in the sea. Therefore, a method for dealing with such contaminated seabed soil has been desired.

  As methods for dealing with contaminated soil, there are known methods for adsorbing and removing radioactive substances (for example, see Patent Document 1) and methods for surrounding contaminated soil with concrete or the like (for example, see Patent Document 2). It has been.

Japanese Unexamined Patent Publication No. 2013-083641 JP 2013-107032 A

  However, there is a problem that it is difficult in practice to remove and treat the pollutant from the contaminated seabed soil, which requires enormous costs, complicated equipment and complicated treatment steps.

  The present invention has been made in view of the above points, and provides a radioactively contaminated seabed soil treatment method that can treat radioactively contaminated soil on the seabed with a simple structure, at low cost, and safely. .

  The present invention includes a radioactively contaminated seabed soil suction step for lifting radioactively contaminated seabed soil containing radioactive cesium on the seafloor to the sea using a pump device, and the radioactively contaminated soil that has been sucked up is accommodated in a contaminated soil concentrator and heated and concentrated. The radioactively contaminated seabed soil heating and concentration process and the concentrated radioactively contaminated seabed soil left in the contaminated soil concentrator are sealed together with the contaminated soil concentrator covered with a refractory block made of artificial ore and silicon carbide. The present invention provides a radioactively polluted seabed soil disposal method and a radioactively polluted seabed soil disposal method characterized by comprising:

  The artificial ore is also characterized in that it is manufactured by adding metal and calcium to silicon or a silicon compound, and melting and cooling repeatedly.

  Also, in the contaminated soil treatment process, the entire tank body concentrated with the solidified pollutant is sealed in a sealed manner with a coating agent mainly composed of artificial ore, and the encased tank body is dumped or landfilled. It is also characterized by its use as a breakwater.

  The coating agent is also characterized in that it is produced by a hardener that mixes a main agent composed of a mixed solution of aluminum oxide and a liquid epoxy resin and the powder of the artificial ore and hardens them.

  According to the present invention, a radioactively polluted seabed soil suction step that is lifted up to the sea using a pump device, a radioactively polluted seabed soil heating and concentration step in which the sucked radioactively polluted soil is housed in a contaminated soil concentrator and heated and concentrated, Concentrated radioactive contaminated seabed soil left in the contaminated soil concentrator is sealed together with the contaminated soil concentrator covered with a refractory block made of artificial ore and silicon carbide and discarded. By the process, the radioactively contaminated seabed soil containing radioactive cesium on the seabed can be easily processed at low cost.

It is a flowchart of the radioactive contamination seabed soil processing method of this invention. It is the schematic of the radioactive contamination seabed soil processing method of this invention. It is explanatory drawing of a contaminated soil concentration apparatus. It is explanatory drawing of a contaminated soil concentration apparatus. It is a figure explaining the measuring device used for a gamma ray shielding measurement experiment. It is a figure explaining the measuring device used for a neutron shielding measurement experiment.

  Hereinafter, the radioactively contaminated seabed soil treatment method according to the present embodiment will be specifically described with reference to the drawings. Here, FIG. 1 is a flowchart of the radioactively contaminated seabed soil treatment method. FIG. 2 is a schematic view of the radioactively contaminated seabed soil treatment method. FIG. 3 is an explanatory diagram of a contaminated soil concentration apparatus. FIG. 4 is an explanatory diagram of a tank to which a coating agent is applied.

  As shown in FIGS. 1 and 2, the present invention includes radioactive cesium, which is a radioactive pollutant, and lifts the seabed soil deposited on the seabed to the sea (radiation-contaminated seabed soil suction step S100) on a tanker. This is a processing method in which the seabed soil is heated and concentrated by the installed heat concentration treatment apparatus (radiation-contaminated seabed soil heating and concentration step S200), and transported and discarded (radiation-contaminated seabed soil disposal processing step S300).

  Here, the radioactive substance contained in the radioactively polluted seabed soil is radioactive cesium, for example, cesium 137 and cesium 134. The radioactive cesium has a boiling point of 671 degrees as a simple substance of cesium and 990 degrees as long as it is cesium hydroxide.

  The radioactively polluted seabed soil suction step S100 in the radioactively polluted seabed soil treatment method according to the present embodiment is a process of lifting the radioactively polluted seabed soil containing radioactive pollutants on the seabed to the sea using a pump device.

  Specifically, the contaminated soil contaminated with radioactive material deposited near the seabed 200 to 1000 meters is sucked up with the seawater using the suction hose 1 and collected. As this means, an air lift pump device, a sand pump device or the like is used. The contaminated soil collected in this way is sent to the tanker 2 to the sea and transferred to the radioactively contaminated seabed soil heating and concentration step S200.

  The seawater transferred to the tanker 2 and the radioactively contaminated seabed soil from the radioactively contaminated seabed soil suction step S100 are accommodated in the contaminated soil concentrating device 3 provided on the tanker. Done.

  Here, the contaminated soil concentrating device 3 includes an inflow pipe 31, a contaminated seabed soil tank 32, and a water vapor discharge pipe 33, as shown in FIG.

  The inflow pipe 31 is connected to the suction hose 1 and sends inflowing contaminated seabed soil mixed with seawater to the contaminated seabed soil tank 32.

  The contaminated seabed soil accommodated in the contaminated seabed soil tank 32 from the inflow pipe 31 is heated and concentrated in the contaminated seabed soil tank 32.

  As shown in FIG. 3, the contaminated submarine soil tank 32 has a substantially rectangular parallelepiped tank body, the tank inner wall 34 is made of metal, and the tank outer wall 35 is coated with a fireproof block 36 made of artificial ore and silicon carbide. Yes. As will be described later, the tank outer wall 35 can block radiation if it has a thickness of 360 mm or more.

  Here, the artificial ore is manufactured by melting a silicon compound such as silicon or silicon dioxide, then adding a metal and calcium, and melting and cooling repeatedly. Specifically, first, about 80% by weight of powdered silicon and silicon compound is charged into a vacuum melting furnace heated to 1650 ° C. to 1680 ° C. under a substantially vacuum state, and then about 5% by weight of powdered silicon. Iron, about 5% by weight of powdered aluminum, and about 5% by weight of calcium are stirred and mixed in order at intervals of 3 to 5 minutes, and then the melt is taken out from the vacuum melting furnace and naturally cooled at room temperature. Then, it is generated by repeating melting and cooling again. The artificial ore thus produced has excellent heat storage and diffusibility.

  When the artificial ore generated as described above is pulverized and mixed with powdered silicon carbide and sintered, a tank outer wall 35 as a fireproof block 36 is formed. As described above, the fireproof block 36 generated from the artificial ore and silicon carbide maintains strength even when processed into a plate shape or the like, improves heat resistance and wear resistance, and further stores heat stored in the artificial ore. In addition, the diffusibility can be improved.

  In addition, a heating device 37 for heating the contaminated seabed soil tank 32 is provided outside the contaminated seabed soil tank 32, and the contaminated seabed soil contained in the contaminated seabed soil tank 32 is provided by the heating device 37. It is comprised so that it can heat-concentrate.

  Here, the heating device 37 in the present embodiment is a microwave generator 37 ′. The microwave generator 37 ′ provided around the tank body irradiates the microwave toward the side wall, the upper surface and the bottom surface of the tank outer wall 35 which is the fireproof block 36 coated with the artificial ore and silicon carbide of the tank body. Is. In addition, as the other heating device 37, not only heating by microwaves but also heating by irradiating infrared rays or radar or direct heating of the tank main body by a heater can be combined and auxiliary heating can be performed. .

  The water contained in the contaminated seabed soil heated and concentrated by the contaminated seabed soil tank 32 is converted into water vapor and discharged to the outside through the water vapor discharge pipe 33. This water vapor can be directly released into the atmosphere.

  In this way, the contaminated seabed soil heated and concentrated in the radioactively contaminated seabed soil heating and concentration step S200 is stored in the contaminated seabed soil tank 32 from which the inflow pipe 31 and the water vapor discharge pipe 33 are removed. It moves to soil disposal processing step S300.

  In the radioactively contaminated seabed soil disposal process S300, the contaminated seabed soil heated and concentrated in the radioactively contaminated seabed soil heating and concentration process S200 is sealed in the contaminated seabed soil tank 32 and discarded. As will be described later, the refractory block 36 made of artificial ore and silicon carbide, which is the tank outer wall 35, has the ability to shield radiation and does not deteriorate over time, and can be stored for a long time.

  Moreover, as shown in FIG. 4, the coating agent 40 which has an artificial ore as a main component can also be apply | coated to the whole sealed tank main body.

  The coating agent 40 is manufactured with an artificial ore 40, a main agent, and a curing agent. The artificial ore 40 is a powder having a particle size of 5 to 30 μm or a powder having a particle size of 150 to 200 mesh. The main agent is a mixture of 60 to 80% by weight of aluminum oxide, 15 to 25% by weight of bisphenol A type liquid epoxy resin, and 5 to 15% by weight of alkylphenol glycidyl ether. A material having 75 to 85% by weight of modified polyamidoamine and 15 to 25% by weight of triethylenetetramine is used. In addition, it is preferable to use about 5.6 g of curing agent for about 100 g of the main agent.

  The tank body that has been foreskind by the coating agent 40 can further improve the waterproofness and antiseptic properties of the fireproof block and can increase the durability.

  In this way, the contaminated seabed soil tank 32 containing the contaminated seabed soil can be discarded directly into the ground, or can be used as a landfill or a breakwater caisson.

  Next, γ-ray and neutron shielding measurement experiments of the refractory block will be described below.

(Γ-ray shielding measurement experiment)
Using the measuring device shown in FIG. 5, the sample is irradiated with collimated γ-rays, and the γ-ray dose rate (μSv / h) transmitted through the sample is measured with a detector. The valence layer (cm) was determined. As the measurement value, an average of 10 measurement values was used.
(Expression) I / I ₀ = e ^−μx = e ^{− (μ / ρ) ρx}
μ: linear attenuation coefficient, x: thickness (cm), ρ: density (g / cm ³ )
λ = 1 / μ: mean free process, μm = μ / ρ: mass attenuation coefficient (cm ² )
D = 0.693 / μ: Half-value layer (cm)

Cobalt (photon energy: 1.173 MeV or 1.333 MeV, 500 KBq), cesium (photon energy: 0.662 MeV, 800 KBq), and radium (photon energy: 0.186 MeV) were used as the radiation source. Moreover, fieldSPEC (made by BICRON) was used for the detector. The sample used was a refractory block mainly composed of artificial ore 9 and silicon carbide shown below, and concrete and a lead block as comparative samples.
・ 12 fireproof blocks (400 × 400 × 30 mm, 13.3 kg, density 2.77 g / cm ³ ) ・ 9 concrete (400 × 400 × 30 mm, 11 kg, density 2.3 g / cm ³ ) ・ Lead block (300 × 300 × 10 mm, density 11.34 g / cm ³ ) 5 sheets

The measurement results of the above tests are shown in Tables 1 to 3 below. In addition, the value which measured separately about lead was used for lead.

  As can be seen from Tables 1 to 3, it was found that the refractory block 36 made of artificial ore and silicon carbide has a shielding effect against γ rays. Moreover, it turned out that the shielding power of said three samples is large in order of lead> refractory block> concrete.

(Neutron shielding measurement experiment)
Next, a neutron shielding measurement experiment will be described.

Using the measurement device shown in FIG. 6, the sample is irradiated with collimated neutron beams, the dose measured through the sample is measured with a detector, and the mean free process (cm) and half-value layer are calculated from the following formulas (Cm) was determined. As the measurement value, an average of 10 measurement values was used.
(Formula) I / I ⁰ = e ^−Σx
Σ: Macroscopic cross section, x: Thickness (cm), λ = 1 / Σ: Mean free process (cm)
D = 0.693 / Σ: Half-value layer (cm)

As a radiation source, cobalt (photon energy: 1.173 MeV or 1.333 MeV, 500 KBq), cesium (photon energy: 0.662 MeV, 800 KBq), and radium (photon energy: 0.186 MeV) were used. The detector used was a ³ He counter. The sample used was a refractory block mainly composed of artificial ore 9 and silicon carbide shown below, and concrete, paraffin block and lead block as comparative samples.
· Refractory block (400 × 400 × 30mm, 13.3kg , density 2.77g / ^cm 3) 12 sheets Concrete (400 × 400 × 30mm, 11kg , density 2.3g / ^cm 3) 9 Like Paraffin blocks (200 × 5 × 100 × 50 mm, density 0.9 g / cm ³ ) • 5 lead blocks (300 × 300 × 10 mm, density 11.34 g / cm ³ )

The measurement results of the above tests are shown in Table 4 and Table 5 below.

  As can be seen from Tables 4 and 5, it was found that the refractory block 36 made of artificial ore and silicon carbide has a shielding effect against neutron beams. Moreover, it turned out that the shielding power of said three samples is large in order of paraffin> lead> fireproof block> concrete.

  As described above, the refractory block 36 made of the artificial ore and silicon carbide of the present invention can shield radiation (γ rays and neutron rays). For this reason, leakage of radiation to the outside can be prevented by surrounding the heat-concentrated seabed soil with a fireproof block made of artificial ore and silicon carbide. The thickness of the fireproof block is preferably 360 mm or more.

  Note that the present invention is not limited to the above-described embodiment and the like. Among the configurations disclosed in the above-described embodiments and the like, the configurations that are mutually replaced or the combination is changed, known techniques, and the above-described embodiments. Also included are configurations in which the configurations disclosed in 1 are replaced with each other or combinations are changed.

S100 Radioactive contaminated seabed soil suction process S200 Radioactive contaminated seabed soil heating and concentration process S300 Radioactive contaminated seabed soil disposal process 1 Suction hose 2 Tanker 3 Contaminated soil concentrator 31 Inflow pipe 32 Contaminated seabed soil tank 33 Water vapor discharge pipe 34 Tank Inner wall 35 Tank outer wall 36 Refractory block 37 Heating device 37 'Microwave generator 40 Coating agent

Claims (4)

Radioactive contaminated seabed soil suction process for lifting radioactively contaminated seabed soil containing radioactive cesium from the seafloor to the sea using a pump device;
Radioactive contaminated seabed soil heating and concentration process in which the radioactively contaminated soil sucked up is housed in a contaminated soil concentrator and heated and concentrated,
Concentrated radioactive contaminated seabed soil left in the contaminated soil concentrator is sealed together with the contaminated soil concentrator covered with a refractory block made of artificial ore and silicon carbide and discarded. And a radioactively contaminated seabed soil treatment method characterized by comprising: 2. The radioactively contaminated seabed soil treatment method according to claim 1, wherein the artificial ore is produced by adding metal and calcium to silicon or a silicon compound, and melting and cooling repeatedly. In the contaminated soil treatment process, the entire tank body concentrated with the solidified pollutant is sealed in a sealed manner with a coating agent mainly composed of artificial ore, and the encased tank body is dumped or landfilled. It uses for a breakwater etc., The radioactive contamination seabed soil processing method of Claim 1 or Claim 2 characterized by the above-mentioned. The said coating agent is produced | generated by the hardening | curing agent which mixes the main ingredient which consists of a mixed solution of an aluminum oxide and a liquid epoxy resin, and the powder of the said artificial ore, and hardens these. Radioactive contaminated seabed soil treatment method.

Images