JP6058370B2 - Alpha nuclide separation method and separation system from sodium chloride-containing waste liquid - Google Patents

Description

  The present invention relates to a method for separating α nuclides from sodium chloride-containing waste liquid and a separation system thereof, wherein α nuclides are separated from sodium chloride-containing waste liquid contaminated with radioactive substances to reduce the concentration of α nuclides.

  2. Description of the Related Art Conventionally, a technique for separating α nuclide from a radioactive material-containing waste liquid contaminated with a radioactive substance has been used as a water treatment technique for nuclear power plants and related facilities. As for the separation of α nuclides, a method for separating nuclides from a high-level radioactive waste liquid (hereinafter referred to as a high-level waste liquid) generated from a reprocessing plant is known. The high level waste liquid is a nitric acid acidic waste liquid, and nuclide elements such as americium (Am) and curium (Cm) are recovered from the high level waste liquid using an extractant.

As a conventional method for separating nuclides from high-level liquid waste, Patent Document 1 discloses an extraction and separation method for americium (Am), curium (Cm), and lanthanoid (Ln) present in an acidic solution. In this extraction and separation method, a diglycolamide compound having a structure in which two amide groups are bonded to each other with a functional group of —CH ₂ —O—CH ₂ — containing ether oxygen is extracted using an extractant, Am, This is a technique for extracting and recovering elements such as Cm and Ln.

  Patent Document 2 uses an extract containing tetramethylpyridylethylenediamine (TPEN), and preferably extracts and separates rare earth elements and actinoid elements using di-2-ethylhexyl-phosphate (D2EHPA) as an extractant together with TPEN. A separation method is described.

  Patent Document 3 discloses that a trivalent actinoid element and a trivalent lanthanoid are obtained by using 1,10-phenanthroline or an alkyl derivative thereof having a neutral bidentate functional group (nitrogen atom: N) as an extractant. A method is described in which only a trivalent actinoid element is selectively extracted and separated from a solution containing the element.

  On the other hand, Patent Document 4 describes a technique of separating and recovering using an adsorbent instead of an extractant for extraction and separation from a high-level waste liquid.

  In Patent Document 4, a high-level radioactive liquid waste containing elements to be separated such as americium (Am), curium (Cm), zirconium (Zr), molybdenum (Mo), palladium (Pd), and rare earth elements is used as an organic phosphorus compound. The solid adsorbent is brought into contact, the element to be separated in the radioactive liquid waste is adsorbed on the solid adsorbent, the solid adsorbent is brought into contact with an acidic aqueous solution containing diethylenetriaminepentanitrate (DTPA), and A separation and recovery method is described in which after eluting Am, Cm, Zr, Mo, Pd and heavy rare earth elements, the solid adsorbent is brought into contact with water or a dilute acid solution to elute light rare earth elements from the solid adsorbent. .

JP 2002-1007 A JP 2004-108837 A JP 2007-278749 A JP 2004-20546 A

J. et al. H. Song et. al. “Nuclear Engineering and Design”, Volume 222 (2003)

  In conventional separation and recovery technology from high-level waste liquid, acidic waste liquid that is acidic as nitric acid is targeted as high-level waste liquid, and americium and the like are present in an ionic state, so extraction as described in each patent document Separation and recovery of nuclides by liquid treatment using an agent or absorbent is effective.

  However, sodium chloride-containing waste liquid contaminated with radioactive substances, which is targeted for radioactive waste liquid mixed with seawater components, has a pH of neutral or weak alkaline, partly ions, partly solid components (solid component) ) In a mixed state. For this reason, α-nuclide separation technology from sodium chloride waste solution contaminated with radioactive substances is a separation / recovery technology using extractant or absorbent from nitric acid high-level waste solution that is assumed in conventional reprocessing plants. Not suitable.

  Sodium chloride-containing wastewater, which is assumed to be radioactive wastewater mixed with seawater components, has a neutral or weak alkaline pH. The actinide elements americium (Am), curium (Cm), uranium (U), and plutonium (Pu) As for, a part becomes an ion and a part becomes a solid component (solid component), and the form is mixed.

  Therefore, instead of the α nuclide separation technology of acidic waste liquid of radioactive material assumed in the conventional reprocessing plant, how is the nuclide separation technology of sodium chloride waste liquid mixed with ions and solid components (solid component)? It was a problem whether to configure.

  Regarding the particle size of α nuclides and the like, according to Non-Patent Document 1 in which the phenomenon of debris being injected into water during a severe accident is examined, as shown in FIG. 1, the debris particle size is 2.0 to 4.75 mm. Many fine particles having a debris particle size of less than 0.425 mm have also been confirmed. It has also been found that it is necessary to install an alpha nuclide separation system that removes debris (solid components) of various particle sizes.

  The present invention has been made in consideration of the above-mentioned circumstances, and while avoiding a criticality accident reliably, by separating the α nuclide by performing solid-liquid separation and ion removal of the sodium chloride-containing waste liquid, the α nuclide concentration is increased. It is an object of the present invention to provide a method for separating α nuclides from waste liquid containing sodium chloride and a separation system thereof.

In order to solve the above-described problem, the method for separating α-nuclide from sodium chloride-containing waste liquid according to the present invention separates sodium chloride-containing waste liquid containing α-nuclide into a solid component and a liquid component using a solid-liquid separation device, and separates them. The solid matter is collected in a solid matter recovery tank while maintaining a subcritical state due to the solid matter component, and the α nuclide concentration is measured with an α nuclide monitor from the separated liquid component waste liquid, and the measured α nuclide concentration Is higher than the target concentration, the α nuclide is separated and removed by an ion content removing device to reduce the α nuclide concentration of the treatment liquid.

Moreover, in order to solve the above-described problems, the α nuclide separation system from the sodium chloride-containing waste liquid according to the present invention includes a waste liquid tank that contains the sodium chloride-containing waste liquid containing the α nuclide, and the sodium chloride-containing waste liquid is a solid substance. A solid-liquid separation device that separates the liquid component into a liquid component, a solids collection tank that collects solids while maintaining a subcritical state due to the separated solids component, and α nuclides from the separated liquid component waste liquid An α nuclide monitor for measuring the concentration, an ion content removing device for separating and removing the α nuclide by guiding the waste liquid of the liquid component whose measured α nuclide concentration is equal to or higher than the target concentration, and the ion content removing device using the α nuclide And a second α nuclide monitor for measuring the α nuclide concentration of the processing waste liquid in which is reduced.

  According to the present invention, it is possible to separate α-nuclide and reduce α-nuclide concentration by performing solid-liquid separation and ion removal of sodium chloride-containing waste liquid containing α-nuclide while avoiding criticality accidents reliably. .

The table of nonpatent literature 1 which examined the phenomenon in which debris was injected in water at the time of a severe accident. The typical block diagram of the alpha nuclide separation system in a 1st embodiment of the present invention. Graph showing the critical data of the uranium in the non-homogeneous _{UO 2} -H 2 O. Graph showing the critical data of MOX in heterogeneous _PuO 2 -uo _2. The typical block diagram of the alpha nuclide separation system from the sodium chloride containing waste liquid in 2nd Embodiment of this invention. The block diagram which shows 3rd Embodiment of this invention and shows an example of the solid-liquid separator with which an (alpha) nuclide separation system is equipped.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings.

[First Embodiment]
FIG. 2 is a configuration diagram schematically showing the α nuclide separation system from the sodium chloride-containing waste liquid according to the first embodiment of the present invention. The α nuclide separation system 10 includes a waste liquid tank 11 that receives radioactive liquid waste containing α nuclides. The radioactive waste liquid 12 received by the waste liquid tank 11 is assumed to be a waste liquid mixed with seawater components, and is a sodium chloride-containing waste liquid contaminated with a radioactive substance. The pH of the sodium chloride-containing waste liquor is neutral or weakly alkaline, and some of the actinide elements americium (Am), curium (Cm), uranium (U), and plutonium (Pu) are ionized. The part becomes a solid (solid matter) component, and its form is in a mixed state.

  Sodium chloride waste liquid (radioactive waste liquid) 12 containing α-nuclide is sent to a solid-liquid separation device 13, and solid-liquid separation into solid matter 14 and liquid component 15 is performed by this solid-liquid separation device 13. The separated solid 14 component containing the α nuclide is sent to the solid collection tank 16 and collected. A solidity recovery tank 16 is provided with a criticality monitor 17, and the criticality monitor 17 always manages the critical state of the solid matter.

The solid 14 recovered in the solid recovery tank 16 may become critical depending on the concentrations of uranium (U) and plutonium (Pu). FIG. 3 shows critical data for uranium, and FIG. 4 shows critical data for MOX (fuel). FIG. 3 shows that when the U-235 concentration is 5 wt%, the cylinder diameter may become critical at 22 cm, and means for avoiding the criticality, for example, a solids recovery tank having a cylinder diameter of less than 22 cm 16 is used or a neutron absorber is installed. According to FIG. 4, a non-homogeneous PuO ₂ -UO ₂ MOX (fuel) may become critical when the cylinder diameter is 18.5 cm, and a means for avoiding the criticality is also necessary. The means for avoiding the criticality may be configured by installing a neutron absorber made of boron or hafnium (Hf) in the solid matter recovery tank 16.

  The waste liquid (supernatant liquid) 15 containing the α nuclide from which the solid matter 14 has been removed by the solid-liquid separator 13 is sent to the liquid collection tank 19 and stored therein. The α nuclide concentration of the waste liquid 15 containing the α nuclide received in the liquid collection tank 19 is measured by the α nuclide monitor 20. When the measured α nuclide concentration is less than the target concentration, for example, less than 1 Bq / ml, the first control device 21 switches the valve 23, for example, a three-way switching valve, to open on the bypass passage 22 side and sends it to the next processing step. The valve 23 may be an individual on-off valve instead of the three-way switching valve.

  The next processing step is, for example, a step of processing β rays or γ rays.

  When the waste liquid containing the α nuclide received in the liquid collection tank 19 measures a target concentration, for example, an α nuclide concentration of 1 Bq / ml or more, by the α nuclide monitor 20, the first controller 21 controls the valve 23. The ion content removing device 24 is connected to the ion content removing device 24 and supplied to the ion content removing device 24. The ion content removing device 24 removes α nuclides from the waste liquid 15 containing α nuclides at a target concentration or higher, reduces the α nuclide concentration, and collects them in the treatment liquid collection tank 26. The α nuclide concentration of the treatment waste liquid 27 collected in the treatment liquid collection tank 26 is measured by a second α nuclide monitor 28.

  When the α nuclide concentration of the treatment waste liquid 27 is less than the target concentration, for example, less than 1 Bq / ml, the second control device 29 opens the valve 30 such as a three-way switching valve to the next processing step side (the α nuclide is less than the target concentration). The processing waste liquid 27 (which has been reduced to 2) is discharged to the next processing step.

  When the α nuclide concentration of the treatment waste liquid 27 is equal to or higher than the target concentration, the valve 23 is communicated to the feedback passage 31 side by the second control device 29, and the treatment waste liquid having the target concentration or higher is passed through the upstream tank of the ion content removing device 24. A liquid collecting tank 19 is fed back. The fed processing waste liquid is again guided to the ion content removing device 24 to remove the α nuclide, and the α nuclide concentration is reduced.

  According to the present embodiment, the α nuclide separation system 10 from the sodium chloride-containing waste liquid removes the α nuclide from the solution using two processing steps of solid-liquid separation of the sodium chloride-containing waste liquid and ion removal, The α nuclide concentration can be reduced.

  If the α nuclide concentration in the treatment liquid (liquid component waste liquid 15) is high, there is a risk of becoming a waste liquid treatment process α nuclide waste in the next treatment step.

  In the α nuclide separation system 10 of this embodiment, the α nuclide separation system 10 provided with the α nuclide monitors 20 and 28 for measuring the α nuclide concentration and provided with the ion content removing device 24 for removing the α nuclide to the target concentration is adopted. To do.

  Furthermore, depending on the concentration of uranium and plutonium, there is a risk of becoming critical. In the α nuclide separation system 10 of the present embodiment, a criticality monitor 17 is provided in the solid matter recovery tank 16 or a criticality avoiding means (not shown) is installed, and the criticality monitor 17 performs critical design. The criticality accident can be reliably avoided.

[Second Embodiment]
FIG. 5 is a configuration diagram schematically showing an α nuclide separation system from a sodium chloride-containing waste liquid according to the second embodiment of the present invention. In the α nuclide separation system 10A of the second embodiment, an additional processing step for removing cesium (Cs) and strontium (Sr) is added to the α nuclide separation system 10 of the first embodiment when measuring the α nuclide. Yes, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the α nuclide monitors 20 and 28, when the α ions are removed to the target concentration in the measurement of the α nuclide concentration, if the concentrations of cesium (Cs) and strontium (Sr) are high, there is a possibility that the α nuclide concentration measurement may be disturbed. is there. In order to avoid the interference of the α nuclide concentration measurement, a cesium / strontium removal device 33 is provided on the upstream side of the liquid collection tank 19.

  In the α nuclide separation system 10A shown in the second embodiment, a cesium / strontium removal device 33 is provided between the solid-liquid separation device 13 and the liquid collection tank 19, and between the solid-liquid treatment and the ion removal treatment, An additional processing step for performing a cesium-strontium removal process is additionally provided.

  In the α nuclide separation system 10A of the second embodiment, the waste liquid 15 of the supernatant liquid containing the α nuclide from which the solid 14 component (including the α nuclide) is removed by the solid-liquid separator 13 is removed by the pump 34 with cesium and strontium. Sent to the device 33. The cesium / strontium removal apparatus 33 includes, for example, a cesium adsorption tower 35 on the upstream side and a strontium adsorption tower 36 on the downstream side. The cesium adsorption tower 35 and the strontium adsorption tower 36 may be configured integrally, or a plurality of each may be provided in series or in parallel.

  Cesium removal in the cesium adsorption tower 35 is carried out using silicate titanate, zeolite, ferrocyanide, etc., and strontium removal in the strontium adsorption tower 36 is carried out using sodium titanate in addition to silicate titanate and zeolite. Is done.

  When removing cesium and strontium in an additional processing step using the cesium / strontium removal device 33, the sodium chloride waste liquid 15 of the liquid component (supernatant liquid) containing the α nuclide from the solid-liquid separation device 13 is supplied to the pump 34. The liquid is passed through the cesium adsorption tower 35 and the strontium adsorption tower 36, where cesium and strontium are removed to avoid interference with the α nuclide concentration measurement by the α nuclide monitor 20. The waste liquid containing the α nuclide processed by the cesium / strontium removal device 33 in the additional processing step is guided to the liquid collection tank 19 where the α nuclide concentration is measured by the α nuclide monitor 20.

  The waste liquid containing the α nuclide whose α nuclide concentration is measured is subsequently subjected to a process of removing the α nuclide similar to the α nuclide separation system 10 shown in the first embodiment and reducing the α nuclide concentration. It is discharged to the next processing step.

  In the α nuclide separation system 10A of the second embodiment, in addition to the same effects as those described in the first embodiment, cesium and strontium are removed when the waste liquid containing the α nuclide passes through the additional treatment step, and α Interference with the nuclide concentration measurement by the nuclide monitors 20 and 28 is avoided, and ions of the α nuclide can be smoothly removed to a target concentration.

[Third Embodiment]
FIG. 6 shows a third embodiment of the present invention.

  The sodium chloride-containing waste liquid α-nuclide separation system 10B shown in the third embodiment is an improvement of the solid-liquid separation device 13 provided in the α-nuclide separation systems 10 and 10A shown in the first embodiment or the second embodiment. It is a thing. Since other configurations are not different, illustration and duplication description are omitted.

  The solid-liquid separator 13 is an apparatus that separates an ionic component and a solid component (solid component) from the sodium chloride-containing waste liquid 12 having α nuclides. As the solid-liquid separator 13, a filtration device is selected according to the size (particle size) of the target solid matter. When the particle size of the solid separated by the solid-liquid separation device 13 is as large as about 0.5 mm or more, the filtration device can be settled and separated by the sedimentation separation device 38.

  According to the past nonpatent literature 1 shown by FIG. 1, presence of the microparticles | fine-particles with a particle size of 0.425 mm or less is also confirmed. The proportion of the fine particles varies widely from 0.5 wt% to 20 wt%, but is assumed to be large as a mass.

  For this reason, the filtration device which is the solid-liquid separation device 13 is constituted by two types of sedimentation separation device 38 and microfiltration device 39. For the microfiltration device 39, a sand filter is selected if the particle size of the fine particles is 0.01 mm or more, and a centrifuge device or the like is selected if it is less than 0.01 mm. Depending on the particle size distribution of the target waste liquid that is the sodium chloride-containing waste liquid having the target α nuclide, either the sedimentation separator 38 or the microfilter 40 may be selected as the filtration device that is the solid-liquid separation device 13.

  For example, when the microfiltration device 39 is selected, if a large amount of solid matter remains, there is a risk of becoming critical in the microfiltration device 40. Applying the critical data of U and MOX in FIGS. 3 and 4, when the U-235 enrichment is 5 wt%, the circular diameter is 22 cm, and in MOX, the circular pitch is around 1 cm and the circular diameter is 18.5 cm. Since it becomes critical, the diameter of the microfilter 40 cannot be increased to, for example, 20 cm or more, and the performance of the microfilter 40 is significantly limited.

  For this reason, a neutron absorber is installed in the microfilter 40 or the filtering device 13 to prevent criticality in the filtering device 13. In addition, by providing a medium containing boron or hafnium as a medium (neutron absorbing material) in or around the filtration device 13, it is possible to reliably prevent criticality even if solid matter is deposited in the filtration device 13. It becomes possible.

  DESCRIPTION OF SYMBOLS 10,10A, 10B ... alpha nuclide separation system, 11 ... waste liquid tank, 12 ... radioactive waste liquid (sodium chloride containing waste liquid), 13 ... solid-liquid separator (filtering device), 14 ... solid substance containing alpha nuclide, 15 ... liquid Component (waste liquid containing α nuclide), 16 ... solids collection tank, 17 ... criticality monitor, 19 ... liquid collection tank, 20 ... α nuclide monitor, 21 ... first control device, 22 ... bypass passage, 23 ... valve (three-way) Switching valve), 24 ... ion content removing device, 26 ... treatment liquid collection tank, 27 ... treatment waste liquid, 28 ... second α nuclide monitor, 29 ... second control device, 30 ... valve (three-way switching valve), 31 ... feedback passage 33 ... Cesium / strontium removal device, 34 ... pump, 35 ... cesium adsorption tower, 36 ... strontium adsorption tower, 38 ... sedimentation separation device, 39 ... microfiltration device, 40 ... microfiltration device.

Claims (10)

Sodium chloride component waste liquid containing α nuclide is separated into solid component and liquid component by solid-liquid separator,
Recovering the solid in a solid recovery tank while maintaining a subcritical state due to the separated solid component,
The α nuclide concentration is measured with the α nuclide monitor from the separated liquid waste liquid,
An α nuclide separation method from a sodium chloride-containing waste liquid, wherein when the measured α nuclide concentration is equal to or higher than a target concentration, the α nuclide is separated and removed by an ion removing device to reduce the α nuclide concentration of the treatment liquid. 2. The sodium chloride-containing waste liquid according to claim 1, wherein when the α nuclide concentration measured by the α nuclide monitor is less than a target concentration, the waste liquid of the liquid component is transferred to the next treatment step, bypassing the ion content removing device. Of α-nuclide from sucrose. The α nuclide concentration of the treatment liquid is measured by a second α nuclide monitor, and when the α nuclide concentration of the treatment liquid is equal to or higher than a target concentration, the treatment liquid is fed back to an upstream tank of the ion content removing device. Of α-nuclide from sodium chloride-containing liquid waste. 3. The sodium chloride-containing composition according to claim 1, further comprising a cesium / strontium removal treatment step for removing cesium and strontium which interferes with the measurement of α nuclide when the α nuclide concentration is reduced, on the upstream side of the α nuclide monitor. Α nuclide separation method from waste liquid. a waste liquid tank containing sodium chloride-containing waste liquid containing α-nuclide,
A solid-liquid separator for separating the sodium chloride-containing waste liquid into a solid component and a liquid component;
A solids collection tank for collecting solids while maintaining a subcritical state due to the separated solids component;
An α nuclide monitor that measures the concentration of α nuclide from the waste liquid of the separated liquid component;
An ion content removing device that guides a waste liquid of the liquid component having a measured α nuclide concentration equal to or higher than a target concentration to separate and remove α nuclide;
An α nuclide separation system from a sodium chloride-containing waste liquid, comprising: a second α nuclide monitor that measures the α nuclide concentration of the treatment waste liquid in which the α nuclide has been reduced by the ion content removing device. The waste liquid of the liquid component separated by the solid-liquid separation device includes a first control device that is guided to a bypass passage that bypasses the ion content removal device when the α nuclide concentration is less than a target concentration. An α nuclide separation system from the sodium chloride-containing waste liquid described in 1. The sodium chloride containing of Claim 5 provided with the 2nd control apparatus fed back to the upstream tank of the said ion content removal apparatus, when the alpha nuclide density | concentration of the process waste liquid processed with the said ion content removal apparatus is more than target concentration. Α nuclide separation system from waste liquid. The solid-liquid separation device includes: a sedimentation separation device that precipitates and separates solids from the sodium chloride-containing waste solution from the waste liquid tank; and a microfiltration device that filters the supernatant liquid from which the solids components have been separated by precipitation. The α nuclide separation system from the sodium chloride-containing waste liquid according to 5. The solid-liquid separation device includes a cesium / strontium removal device for removing cesium and strontium from the separated liquid waste liquid,
The α nuclide separation system from sodium chloride-containing waste liquid according to claim 5, wherein the α nuclide concentration is measured by the α nuclide monitor from the treatment waste liquid of the liquid component processed by the cesium / strontium removal apparatus. The cesium / strontium removing device is a cesium adsorption tower for adsorbing and removing cesium from a waste liquid of the liquid component separated by the solid-liquid separator,
It consists of a strontium adsorption tower that adsorbs and removes strontium on the downstream side of this cesium adsorption tower,
The system for separating α-nuclide from waste liquid containing sodium chloride according to claim 9, wherein the treatment waste liquid of the liquid component treated in the strontium adsorption tower is guided to the liquid collection tank.

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