CN109295493B - Electrochemical in-situ decontamination method for radioactive pollutants on metal surface - Google Patents
Electrochemical in-situ decontamination method for radioactive pollutants on metal surface Download PDFInfo
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- CN109295493B CN109295493B CN201811245087.3A CN201811245087A CN109295493B CN 109295493 B CN109295493 B CN 109295493B CN 201811245087 A CN201811245087 A CN 201811245087A CN 109295493 B CN109295493 B CN 109295493B
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- C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
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- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
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Abstract
The invention discloses an electrochemical in-situ decontamination method for radioactive pollutants on metal surfaces, which comprises a liquid storage tank, wherein a cathode plate is arranged below the liquid storage tank, a lead is connected onto the cathode plate, a through hole is formed in the bottom of the liquid storage tank, and the bottom end of the through hole sequentially penetrates through the liquid storage tank and the cathode plate; the outside detachably of liquid storage pot is connected with anode contactor, and anode contactor is provided with the chamber that holds that is used for holding the negative plate, is provided with annular sealing member on the anode contactor, and annular sealing member is inside to constitute with the anode contactor bottom surface and washs the chamber, and the opening has been seted up to anode contactor bottom, and the opening intercommunication holds the chamber and washs the chamber. For a smaller polluted area, the invention can carry out fixed-point in-situ decontamination on the radionuclide area through the cleaning cavity formed by the anode contactor and the annular sealing element, has high decontamination precision and good decontamination effect, can not waste electrolyte on the metal surface which does not need to be cleaned, not only saves the cleaning cost, but also has less secondary waste liquid amount.
Description
Technical Field
The invention relates to the field of nuclear facility retirement and three-waste treatment, in particular to an electrochemical in-situ decontamination method for radioactive pollutants on a metal surface.
Background
In nuclear power plants, military nuclear power and research institutes, along with the operation, maintenance, inspection and regular maintenance of nuclear facility equipment, a large number of detachable and difficult-to-detach metal-polluted parts, such as pipelines, glove boxes and the like, are generated in the spent fuel aftertreatment and nuclear facility decommissioning. Watch with watchThe main radionuclides of surface deposition and adhesion contamination are60Co、55Fe、63Ni and54and Mn. The decontamination of nuclear facilities such as these metal-contaminated parts is mainly carried out by removing the contaminated radionuclides from the surface or the interior thereof, wholly or partially, by physical or chemical methods and means, so as to prevent and reduce the harm of the radionuclides to the human and the environment as much as possible and reduce the amount of radioactive solid waste generated.
Electrochemical decontamination means that pollutants on the metal surface are dissolved through electrolysis, and then are separated from the metal surface and dissolved in electrolyte, so that the metal surface is smooth, and the aim of decontamination is fulfilled. It has the following advantages: the damage to a metal machine body is small, so that the surface is covered by an oxide film, and secondary pollution is not easy to occur after dirt removal; the working efficiency is high, and decontamination can be completed in a short time; the usage amount of chemical reagents is small, and the generated waste liquid is correspondingly reduced; soft and hard dirt can be removed, and the decontamination effect is good; is beneficial to further disposal, and the cost required by decontamination is relatively low. Therefore, electrochemical decontamination is effective and practical as a method for decontaminating contaminated metal parts produced in operations in the nuclear industry field. In the future, electrochemical decontamination is also a promising approach as a decontamination method associated with extremely low levels of radioactivity exemption in order to reduce the amount of retired waste produced.
However, the electrochemical polishing device used in the traditional electrochemical decontamination method is mainly groove-type electrochemical decontamination, for example, patent with publication number CN205943483 discloses an ultrasonic electrolysis automatic decontamination device for removing radioactive surface contamination, which requires manually removing small parts and placing them into an electrolytic cell, not only the process is complicated, but also the electrolyte can electrolyze the whole parts regardless of whether the parts are contaminated, the device has no pertinence, and the decontamination efficiency is low; patent publication No. CN102628176A discloses a mobile cathode electrochemical cleaning device, which is also suitable for cleaning large areas, and has a complex structure and inconvenient use and maintenance. Therefore, a method for performing in-situ spot decontamination on a local radioactive hot spot area on a metal surface of an undetachable workpiece is needed to solve the problems in the prior art.
Disclosure of Invention
The invention aims to provide an electrochemical in-situ decontamination method for radioactive pollutants on a metal surface, which aims to solve the problems that in the prior art, the decontamination process for a difficult and undetachable metal workpiece is complex, the decontamination cost is high due to no pertinence to radioactive nuclides, and an electrochemical decontamination device is complex in structure and inconvenient to maintain and use.
The invention is realized by the following technical scheme:
the electrochemical in-situ decontamination method for the radioactive pollutants on the metal surface uses an electrochemical decontamination system, the electrochemical decontamination system comprises a direct-current stabilized power supply, an anode metal clamp and a portable electrochemical cathode device, the portable electrochemical cathode device comprises a liquid storage tank, a cathode plate is arranged below the liquid storage tank, a lead is connected onto the cathode plate, a through hole is formed in the bottom of the liquid storage tank, and the bottom end of the through hole sequentially penetrates through the liquid storage tank and the cathode plate; the outer part of the liquid storage tank is detachably connected with an anode contactor, the anode contactor is provided with an accommodating cavity for accommodating a cathode plate, a filling pad positioned below the cathode plate is also arranged in the accommodating cavity, an annular sealing element is arranged on the anode contactor, the inner part of the annular sealing element and the bottom surface of the anode contactor form a cleaning cavity, the bottom of the anode contactor is provided with an opening, and the opening is communicated with the accommodating cavity and the cleaning cavity;
the method comprises the following steps:
(A) the anode of the direct current stabilized power supply clamps a workpiece to be decontaminated through an anode metal clamp;
(B) the portable electrochemical cathode device is connected to the negative electrode of the direct current stabilized power supply through a lead;
(C) placing the annular sealing element in a radioactive contamination area on the surface of the workpiece to be decontaminated, and compacting the annular sealing element to completely seal the cleaning cavity; wherein, the steps (A) to (C) are not in sequence;
(D) adding electrolyte into the liquid storage tank, and starting a direct-current stabilized power supply to carry out electrochemical decontamination;
(E) after decontamination is finished, closing the direct current stabilized voltage power supply, and cleaning the surface of the workpiece, the cathode plate, the anode contactor and the annular sealing element;
(F) collecting and uniformly treating the secondary waste liquid generated by washing in the step (E) and the used filling pad.
In the prior art, the groove type electrochemical decontamination is used for cleaning detachable parts in batches, but has no effect on radioactive contamination on the surfaces of stainless steel workpieces such as a hot chamber, the wall surface of a storage water tank, the table surface of a glove box and the like, the application range is narrow, and meanwhile, the groove type electrochemical decontamination process is complex, and if the groove type electrochemical decontamination is used for cleaning a certain workpiece independently, the cleaning cost is high; the mobile cathode electrochemical cleaning device disclosed in chinese patent CN102628176A is not only complex in structure, resulting in inconvenience in installation, use and maintenance, but also the same as the slot type electrochemical decontamination, the device cannot perform concentrated cleaning on the radionuclide in a certain small area, i.e. the cleaning effect is the same for all areas regardless of whether there is any radionuclide, which not only causes electrolyte waste, but also has poor cleaning effect, and many secondary waste liquids, and thus has no popularization value.
Moreover, the traditional electrochemical decontamination device for decommissioned nuclear equipment has the problems of low decontamination efficiency, long decontamination time, complex waste treatment process and the like. The workers are exposed to radioactive environment for a long time in the processes of decontamination process and post-treatment process, and the health of the workers is not facilitated.
In order to solve the problems in the prior art, the inventor designs a portable electrochemical cathode device capable of performing fixed-point in-situ decontamination of local "hot spots" on the metal surface, and applies for utility model (application number: CN 201820965346.9). After that, the inventor continuously researches, develops a corresponding electrochemical decontamination method around an electrochemical decontamination system applying the portable electrochemical cathode device, further determines the optimal reaction condition and electrolyte ratio of the electrochemical decontamination method through an experimental method, obviously improves decontamination efficiency and greatly shortens decontamination time.
Specifically, the electrochemical decontamination system applied to the experimental method comprises a direct-current stabilized power supply, an anode metal clip and a portable electrochemical cathode device. The anode of the direct current stabilized power supply is connected to the anode metal clip through a lead, and the cathode of the direct current stabilized power supply is connected to the portable electrochemical cathode device through a lead. The whole structure of the electrochemical decontamination system and the connection mode of the anode and the cathode are the prior art, and the invention is not limited in particular.
An improvement of the present invention is to provide a portable electrochemical cathode device that enables spot in-situ decontamination of localized "hot spots" on a metal surface.
Specifically, the portable electrochemical cathode device comprises a liquid storage tank, and a cathode plate is arranged below the liquid storage tank, wherein the cathode plate can be preferably a cathode titanium plate. The diameter of the cathode plate may be less than, equal to or greater than the diameter of the bottom of the reservoir tank, preferably the diameter of the cathode plate is equal to the diameter of the bottom of the reservoir tank, as one preferred dimension of the cathode plate, the diameter of the cathode plate is 50 mm. The connection mode of the negative plate and the bottom surface of the liquid storage tank can be connection through a fastener, threaded connection, clamping connection or splicing, and can also be fixed on the bottom surface of the liquid storage tank in a welding mode. And the negative plate is connected with a lead which is externally connected with a negative electrode of a direct current stabilized voltage power supply. The bottom of liquid storage pot is provided with the through-hole, and the liquid storage pot, negative plate are run through in proper order to the bottom of through-hole, and the below space of through-hole intercommunication liquid storage pot inside and negative plate promptly, and the purpose-built of through-hole makes the inside electrolyte that holds of liquid storage pot can permeate to the negative plate from the liquid storage pot inside to finally permeate to the below of negative plate, in order to make the electrolyte in the liquid storage pot can slowly flow to the negative plate below, the diameter of through-hole should not be too big, and preferably, the diameter of through-hole is 1 ~ 3 mm.
The outside of the liquid storage tank is detachably connected with an anode contactor, and meanwhile, an accommodating cavity is formed in the anode contactor to accommodate the cathode plate, wherein the accommodating means that the cathode plate is completely placed in the accommodating cavity. The liquid storage tank, the anode contactor and the cathode plate are arranged in various modes, for example, when the diameter of the cathode plate is smaller than that of the bottom of the liquid storage tank, the upper surface of the anode contactor can be connected with the lower surface of the liquid storage tank, or the inner surface of the accommodating cavity of the anode contactor is detachably connected with the side surface of the liquid storage tank; when the diameter of the cathode plate is larger than or equal to the diameter of the bottom of the liquid storage tank, the inner surface of the containing cavity of the anode contactor is detachably connected with the side surface of the liquid storage tank. Preferably, the diameter of the cathode plate is equal to the diameter of the bottom of the liquid storage tank, the central axis of the cathode plate is collinear with the central axis of the liquid storage tank, and the inner wall of the accommodating cavity of the anode contactor is detachably connected with the lower half part of the outer wall of the liquid storage tank in a threaded connection mode. When the accommodating cavity of the anode contactor accommodates the lower half part of the liquid storage tank, a through groove for leading the lead is arranged in the anode contactor so as to lead the lead out of the cathode plate to the outside of the anode contactor.
And a filling pad is also arranged in the accommodating cavity and is positioned below the cathode plate. Preferably, the filling pad is made of absorbent cotton. The provision of the filling shoe has at least three benefits: firstly, the filling pad further slows down the permeation speed of the electrolyte, the electrolyte is uniformly dispersed, and the electrolyte entering the filling pad continuously permeates into the cleaning cavity only after the filling pad is saturated, so that the damage to the metal surface caused by overhigh local concentration or poor cleaning effect caused by low local concentration due to nonuniform distribution of the electrolyte in the cleaning cavity is avoided; secondly, the filling pad saturated with the electrolyte protrudes downwards to the lower part of the opening under the action of gravity and is finally contacted with the workpiece to be decontaminated to form a salt bridge for decontamination, and the filling pad also has the function of a wiping cloth, can wipe part of the radionuclide with high adhesive force and uniformly wipe the electrolyte on the workpiece to be decontaminated; thirdly, after the decontamination is completed, the filling pad is in a saturated state, the electrochemical decontamination solution is adsorbed, the filling pad can be rapidly used next time by replacing the filling pad, and meanwhile, the filling pad has the function of collecting the electrochemical decontamination solution, so that the subsequent treatment process of the electrochemical decontamination solution is facilitated.
An annular sealing element is arranged below the anode contactor, the anode contactor and the annular sealing element can be connected in a clamping mode, an inlaying mode or a fastening mode, and the annular sealing element can be made of strong acid resistant rubber such as ethylene propylene diene monomer. When the portable electrochemical cathode device is placed on a workpiece to be decontaminated, the annular sealing element is tightly attached to the workpiece to be decontaminated by generating certain deformation, so that the electrolyte is prevented from being diffused. The interior of the annular sealing element and the bottom surface of the anode contactor jointly form a cleaning cavity. The opening that the positive pole contactor bottom was seted up is used for the intercommunication to hold chamber and washing chamber for electrolyte and the filling pad self can enter into the washing chamber through the opening part of permeating to filling pad below. When the cleaning device is used, the annular sealing piece is tightly attached to a workpiece to be cleaned, the cleaning cavity is completely closed, the electrolyte forms a salt bridge in the cleaning cavity, and the direct-current stabilized voltage power supply is electrified to clean the radioactive nuclide in a local area. Preferably, the annular sealing members of different sizes can be replaced according to the size of the polluted area on the workpiece to be decontaminated, and the anode contactors of different sizes can be replaced according to the required electrode spacing, so that the distance between the cathode plate and the workpiece to be decontaminated of the anode is 40-100 mm, for example.
Through the structural design of the portable electrochemical cathode device, the radionuclide area on the workpiece can be cleaned in an electrochemical mode no matter the workpiece is detachable or not detachable, or a large-sized workpiece or a small-sized workpiece; meanwhile, for a small polluted area, the radionuclide area can be subjected to fixed-point in-situ decontamination through a cleaning cavity formed by the anode contactor and the annular sealing element, the decontamination precision is high, the decontamination effect is good, the electrolyte cannot be wasted on the metal surface which does not need to be cleaned, the cleaning cost is saved, and the secondary waste liquid amount is small; moreover, between the anode contactor and the liquid storage pot of the cathode device, between the liquid storage pot and the cathode plate, all adopt detachably connected mode between anode contactor and the annular sealing member, the flexible operation, the user can choose the size of anode contactor and annular sealing member according to the actual demand is nimble, and the installation, the dismantlement, the use and the maintenance of equipment are all very convenient.
Another improvement of the present invention is to provide a corresponding electrochemical decontamination method around the electrochemical decontamination system, and further to determine the optimal reaction conditions and electrolyte ratio of the electrochemical decontamination method.
Specifically, the method comprises the following steps:
(A) the anode of the DC stabilized power supply clamps the workpiece to be decontaminated through the anode metal clamp. The anode metal clamp is connected with the positive electrode of the direct current stabilized voltage power supply through a lead, and is fixedly clamped on a workpiece to be decontaminated, such as a steel plate. It will be understood by those skilled in the art that the anode metal clamp should be construed broadly and that any structure capable of being clamped and secured to a workpiece to be decontaminated should be considered to be part of the anode metal clamp.
(B) The portable electrochemical cathode device is connected to the negative electrode of the direct current stabilized power supply through a lead;
(C) and placing the annular sealing element in a radioactive contamination area on the surface of the workpiece to be decontaminated, and compacting the annular sealing element to completely close the cleaning cavity. The steps (A) - (C) are not in sequence.
(D) Adding electrolyte into the liquid storage tank, and starting a direct-current stabilized power supply to carry out electrochemical decontamination;
(E) after decontamination is finished, closing the direct current stabilized voltage power supply, and cleaning the surface of the workpiece, the cathode plate, the anode contactor and the annular sealing element;
(F) collecting and uniformly treating the secondary waste liquid generated by washing in the step (E) and the used filling pad.
Through the steps, the workpiece surface decontamination can be realized quickly and efficiently at normal temperature, the waste treatment method is simple, the time of exposure of workers to radioactive environment in decontamination process and post-treatment process is shortened, and the operation safety of the workers is improved.
In order to further improve the decontamination efficiency and shorten the decontamination time, the inventor obtains the main factors and the secondary factors of the influence factors on the decontamination efficiency, namely electrolyte concentration > electrode spacing > current density, by an orthogonal experiment method, and further determines the preferable electrolyte proportion and reaction conditions. Wherein the electrolyte in the step (D) comprises HNO3Said HNO3The concentration of the solution is 6-10 mol/L. Preferably, HNO3The concentration of the solution was 10 mol/L.
Further, the electrolyte also comprisesComprising NaNO3As an electrolyte, the NaNO3The content of (B) is 100 g/L.
Further, the current density is (0.1-0.5) A/cm2Preferably, the current density is 0.3A/cm2。
Further, the distance between the cathode plate and the workpiece to be decontaminated is 0.4-1.0 cm, and preferably, the distance between the cathode plate and the surface of the workpiece to be decontaminated is 0.4 cm.
As a preferred embodiment of the portable electrochemical cathode device, the device further comprises a top cover positioned above the liquid storage tank, wherein the top cover is provided with an adjusting through hole, the adjusting through hole is communicated with the inner space and the outer space of the top cover, the top cover is provided with an adjusting bolt and an adjusting screw hole matched with the adjusting bolt, and the adjusting screw hole is communicated with the adjusting through hole. Preferably, the diameter of the adjustment through-hole is 2 mm. Through the arrangement, the top cover not only can be used for preventing pollutants from falling into the liquid storage tank to pollute the electrolyte, but also can be used for closing or opening the adjusting through hole through the screwing-in or screwing-out of the adjusting bolt in the adjusting screw hole so as to control the pressure inside the liquid storage tank and control the speed of the electrolyte permeating through the through hole. Specifically, when the top cover covers the opening above the liquid storage tank and the adjusting through hole is completely sealed by the adjusting bolt, the inner space of the liquid storage tank is of a closed structure, and as the electrolyte gradually permeates from the through hole, the pressure above and below the electrolyte changes, and the permeation speed of the electrolyte is reduced; when the regulating through hole is opened, the space above the electrolyte is communicated with the external air pressure, and the permeation speed is increased again. It can be seen that through above-mentioned structure for the user can adjust the infiltration rate of electrolyte according to actual demand when the operation, further improves the utilization ratio of electrolyte and the flexibility of operation. Preferably, the inner wall of the top cover is in threaded connection with the outer wall of the liquid storage tank.
Further, a sealing gasket is arranged at the bottom of the adjusting bolt. Sealed pad can change well through self-shape and the inside laminating of adjusting the through-hole, and then reach and seal the effect better, sealed pad simultaneously can also play certain cushioning effect, avoids the adjusting bolt of metal to avoid causing the scratch to adjusting the through-hole.
Further, the outer side of the liquid storage tank is sleeved with a shell positioned above the anode contactor, the shell is connected with a handle, and a wiring groove is formed in the handle. The shell arranged above the anode contactor is beneficial to protecting the liquid storage tank, and meanwhile, the handle connected to the shell can be conveniently held by an operator, so that the use of the operator is facilitated. Preferably, the handle is detachably connected to the side of the housing by means of screw holes. A wiring groove is arranged in the handle and used for placing a wire which extends from the anode contactor and is connected with the negative pole of the direct-current stabilized voltage power supply, and inconvenience in operation caused by random placement of the wire is avoided.
As a preferred technical scheme of the arrangement mode of the through holes, the number of the through holes is 6, and the arrangement mode of the 6 through holes is as follows: the 6 through holes are respectively positioned at 6 vertexes of the regular hexagon.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. for a small polluted area, the cleaning cavity formed by the anode contactor and the annular sealing element can be used for performing fixed-point in-situ decontamination on the radionuclide area, the decontamination precision is high, the decontamination effect is good, the electrolyte cannot be wasted on the metal surface which does not need to be cleaned, the cleaning cost is saved, the secondary waste liquid amount is small, and the wide popularization value is realized;
2. according to the invention, the filling pad is arranged, so that the permeation speed of the electrolyte can be further slowed down, the electrolyte is uniformly dispersed, and the damage to the metal surface caused by overhigh local concentration or poor cleaning effect caused by low local concentration due to nonuniform distribution of the electrolyte in the cleaning cavity is avoided; secondly, the filling pad saturated with the electrolyte protrudes downwards to the lower part of the opening under the action of gravity and is finally contacted with a workpiece to be decontaminated to form a salt bridge for decontamination, and the filling pad also has the function of a wiping cloth, can wipe part of radionuclide with high adhesive force and uniformly wipe the electrolyte on the workpiece to be decontaminated; finally, after decontamination is completed, the filling pad is in a saturated state and adsorbs electrochemical decontamination solution, the filling pad can be quickly used for the next time by replacing the filling pad, and meanwhile, the filling pad has the function of collecting the electrochemical decontamination solution, so that the subsequent treatment process of the electrochemical decontamination solution is facilitated;
3. the invention has high decontamination efficiency and short decontamination time, and can carry out electrochemical decontamination reaction at normal temperature, thereby obviously improving the safety of workers in the electrochemical decontamination process;
4. the present invention is directed to two sources of nuclear waste: the electrolyte filling pad bearing electrochemical waste liquid and the secondary waste liquid for cleaning are collected and treated in a unified manner, so that the post-treatment difficulty is simplified, and the post-treatment efficiency is improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a schematic structural diagram of an embodiment of the present invention;
FIG. 2 is a schematic view of the construction of a cathode plate in an embodiment of the invention;
FIG. 3 is a 4000-fold enlarged view of the surface topography of a scanning electron microscope of a workpiece to be decontaminated after electrolysis;
reference numbers and corresponding part names in the drawings:
1-a liquid storage tank, 2-a cathode plate, 3-a through hole, 4-an anode contactor, 5-an annular sealing element, 6-a filling pad, 7-a top cover, 8-an adjusting bolt, 9-a shell, 10-a handle, 11-a wiring groove, 12-a wire and 13-a workpiece to be decontaminated.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
In the description of the present invention, it is to be understood that the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and therefore, are not to be construed as limiting the scope of the present invention.
Example 1:
in the embodiment shown in fig. 1 to 3, the electrochemical in-situ decontamination method for radioactive pollutants on metal surfaces uses an electrochemical decontamination system, the electrochemical decontamination system comprises a direct current stabilized power supply, an anode metal clamp and a portable electrochemical cathode device, the portable electrochemical cathode device comprises a liquid storage tank 1, a cathode plate 2 is arranged below the liquid storage tank 1, a lead 12 is connected on the cathode plate 2, a through hole 3 is arranged at the bottom of the liquid storage tank 1, and the bottom end of the through hole 3 sequentially penetrates through the liquid storage tank 1 and the cathode plate 2; the liquid storage tank 1 is detachably connected with an anode contactor 4, the anode contactor 4 is provided with an accommodating cavity for accommodating the cathode plate 2, a filling pad 6 positioned below the cathode plate 2 is also arranged in the accommodating cavity, an annular sealing element 5 is arranged on the anode contactor 4, the interior of the annular sealing element 5 and the bottom surface of the anode contactor 4 form a cleaning cavity, the bottom of the anode contactor 4 is provided with an opening, and the opening is communicated with the accommodating cavity and the cleaning cavity; the filling pad 6 is made of absorbent cotton; the number of the through holes 3 is 6, and the arrangement mode of the 6 through holes 3 is as follows: the 6 through holes 3 are respectively located at 6 vertexes of the regular hexagon.
The method comprises the following steps:
(A) the positive electrode of the direct current stabilized power supply clamps the workpiece 13 to be decontaminated through an anode metal clamp;
(B) the portable electrochemical cathode device is connected to the negative electrode of the direct current stabilized power supply through a lead 12;
(C) placing the annular sealing element 5 in a radioactive contamination area on the surface of the workpiece 13 to be decontaminated, and compacting the annular sealing element 5 to completely seal the cleaning cavity; wherein, the steps (A) to (C) are not in sequence;
(D) adding electrolyte into the liquid storage tank 1, and starting a direct-current stabilized power supply to carry out electrochemical decontamination; (E) after decontamination is finished, the direct current stabilized voltage power supply is closed, and the surface of the workpiece, the cathode plate 2, the anode contactor 4 and the annular sealing element 5 are cleaned;
(F) collecting and uniformly treating the secondary waste liquid generated by cleaning in the step (E) and the used filling pad 6;
the electrolyte in the step (D) is HNO with the concentration of 10mol/L3The electrolyte also comprises NaNO electrolyte3Said NaNO3The content of (A) is 100 g/L; the reaction parameters are as follows: the current density is 0.3A/cm2(ii) a The distance between the cathode plate 2 and the workpiece 13 to be decontaminated is 0.4 cm; the reaction temperature was room temperature.
To verify the decontamination efficiency of the above method, it was made to contain mainly60And (3) fixedly polluting the workpiece to be decontaminated 13 by using the stainless steel contaminated by the distillation residue of the Co as a hot spot, wherein the area of the area to be decontaminated is phi 50 mm. As shown in figure 3, after 30s of electrolytic reaction, the surface has no obvious pits and becomes a porous dense network structure, which shows that the surface of the workpiece 13 to be decontaminated has60The Co has been substantially removed. By calculation, of its surface60The pollution level of Co is from 19.160Bq/cm2Reduced to 0.103Bq/cm2The decontamination efficiency reaches 99.46 percent. Therefore, the method can be carried out under the normal temperature condition, can carry out fixed-point in-situ decontamination on a specific area in a targeted manner within a short time, has accurate decontamination precision and high decontamination efficiency, does not waste electrolyte on the metal surface which does not need to be cleaned, saves the cleaning cost, has small secondary waste liquid amount, and has wide popularization value.
Example 2:
on the basis of the embodiment 1, the portable electrochemical cathode device further comprises a top cover 7 positioned above the liquid storage tank 1, wherein the top cover 7 is provided with an adjusting through hole, the adjusting through hole is communicated with the inner space and the outer space of the top cover 7, the top cover 7 is provided with an adjusting bolt 8 and an adjusting screw hole matched with the adjusting bolt 8, and the adjusting screw hole is communicated with the adjusting through hole; the bottom of the adjusting bolt 8 is provided with a sealing gasket; the outer side of the liquid storage tank 1 is sleeved with a shell 9 positioned above the anode contactor 4, the shell 9 is connected with a handle 10, and a wiring groove 11 is formed in the handle 10.
Make the user can adjust the infiltration rate of electrolyte according to actual demand when the operation through top cap 7 and adjusting through-hole, adjusting bolt 8, regulation screw, further improve the utilization ratio of electrolyte and the flexibility of operation.
The shell 9 is beneficial to protecting the liquid storage tank 1, and meanwhile, the handle 10 connected to the shell 9 can be conveniently held by an operator, so that the use of the operator is facilitated. The wiring groove 11 arranged in the handle 10 is used for placing a lead 12 which extends from the anode contactor 4 and is connected with the cathode of the direct-current stabilized power supply, so that the inconvenience in operation caused by random placement of the lead is avoided.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. The electrochemical in-situ decontamination method for the radioactive pollutants on the metal surface uses an electrochemical decontamination system, the electrochemical decontamination system comprises a direct-current stabilized power supply, an anode metal clamp and a portable electrochemical cathode device, and is characterized in that the portable electrochemical cathode device comprises a liquid storage tank (1), a cathode plate (2) is arranged below the liquid storage tank (1), a lead (12) is connected onto the cathode plate (2), a through hole (3) is formed in the bottom of the liquid storage tank (1), and the bottom end of the through hole (3) sequentially penetrates through the liquid storage tank (1) and the cathode plate (2); the outer part of the liquid storage tank (1) is detachably connected with an anode contactor (4), the anode contactor (4) is provided with an accommodating cavity for accommodating the cathode plate (2), a filling pad (6) positioned below the cathode plate (2) is further arranged in the accommodating cavity, an annular sealing element (5) is arranged on the anode contactor (4), the inner part of the annular sealing element (5) and the bottom surface of the anode contactor (4) form a cleaning cavity, the bottom of the anode contactor (4) is provided with an opening, and the opening is communicated with the accommodating cavity and the cleaning cavity;
the method comprises the following steps:
(A) the positive electrode of the direct current stabilized power supply clamps a workpiece (13) to be decontaminated through an anode metal clamp;
(B) the portable electrochemical cathode device is connected to the negative electrode of the direct current stabilized power supply through a lead (12);
(C) placing the annular sealing element (5) in a radioactive contamination area on the surface of a workpiece (13) to be decontaminated, and compacting the annular sealing element (5) to completely close the cleaning cavity; wherein, the steps (A) to (C) are not in sequence;
(D) adding electrolyte into the liquid storage tank (1), and starting a direct current stabilized power supply to carry out electrochemical decontamination, wherein the electrolyte comprises HNO3Said HNO3The concentration of the solution is 6-10 mol/L;
(E) after decontamination is finished, closing the direct current stabilized voltage power supply, and cleaning the surface of the workpiece, the cathode plate (2), the anode contactor (4) and the annular sealing element (5);
(F) collecting and uniformly treating the secondary waste liquid generated by washing in the step (E) and the used filling pad (6).
2. The method of claim 1, wherein the electrolyte further comprises NaNO3Said NaNO3The content of (B) is 100 g/L.
3. The electrochemical in-situ decontamination method for radioactive contaminants on a metal surface according to claim 1, wherein the reaction parameters in step (D) are: the current density is (0.1-0.5) A/cm2。
4. The electrochemical in-situ decontamination method for radioactive contaminants on metal surfaces according to claim 1, characterized in that the distance between the cathode plate (2) and the workpiece (13) to be decontaminated is 0.4-1.0 cm.
5. The electrochemical in-situ decontamination method for radioactive contaminants on a metal surface according to claim 1, further comprising a top cover (7) positioned above the liquid storage tank (1), wherein the top cover (7) is provided with an adjusting through hole, the adjusting through hole is communicated with the inner space and the outer space of the top cover (7), the top cover (7) is provided with an adjusting bolt (8) and an adjusting screw hole matched with the adjusting bolt (8), and the adjusting screw hole is communicated with the adjusting through hole.
6. The method for the electrochemical in-situ decontamination of radioactive contaminants on metal surfaces according to claim 5, wherein the adjusting bolt (8) is provided with a sealing gasket at the bottom.
7. The electrochemical in-situ decontamination method for radioactive contaminants on a metal surface according to claim 1, wherein a housing (9) positioned above the anode contactor (4) is sleeved on the outer side of the liquid storage tank (1), a handle (10) is connected to the housing (9), and a wiring slot (11) is arranged in the handle (10).
8. The method for electrochemical in-situ decontamination of radioactive contaminants on a metal surface according to any one of claims 1 to 7, wherein the material of the filling pad (6) is absorbent cotton.
9. The electrochemical in-situ decontamination method for radioactive contaminants on a metal surface according to any one of claims 1 to 7, wherein the number of the through holes (3) is 6, and the arrangement manner of the 6 through holes (3) is as follows: the 6 through holes (3) are respectively positioned at 6 vertexes of the regular hexagon.
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| CN109295493B (en) * | 2018-10-24 | 2020-05-26 | 中国核动力研究设计院 | Electrochemical in-situ decontamination method for radioactive pollutants on metal surface |
| CN109913936B (en) * | 2019-04-30 | 2020-10-16 | 中广核核电运营有限公司 | Decontamination system and decontamination method |
| CN110444308B (en) * | 2019-08-01 | 2024-07-19 | 中广核核电运营有限公司 | In-situ electrolytic nuclear pollution decontamination matched decontamination head |
| CN111748837A (en) * | 2020-07-27 | 2020-10-09 | 中广核核电运营有限公司 | Immersion type electrolytic decontamination device |
| CN115762840B (en) * | 2022-10-26 | 2023-07-07 | 核工业北京化工冶金研究院 | Electrochemical decontamination device and decontamination method for pipeline |
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