• 专利附录
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    • 专利摘要:
    A method of reducing radiation exposure comprises the steps of: injecting iron into a coolant flowing from the reactor cooling system to the reactor core of a nuclear power plant; ferrite and fix radionuclides or modernuclides thereof, which are entrapped in the refrigerant, on the surface of a reactor core structure, wherein an iron citrate which is soluble organic iron, or iron oxalate or iron fumarate having a particle diameter of 3 μm or less is used as the iron with which the injection is made. .
    公开号:SE1100429A1
    申请号:SE1100429
    申请日:2009-11-04
    公开日:2011-06-29
    发明作者:Yumi Yaita；Seiji Yamamoto；Hajime Hirasawa；Yutaka Uruma
    申请人:Toshiba Kk；
    IPC主号:
    专利说明:

    2 of the high energy type, becomes the main radiation source for the radial beam (radiation) received by the worker when he performs power plant inspection and so on.
    To reduce the exposure dose received by the worker, it is important to reduce the concentration of cobalt (Co) which is a coolant flowing in the reactor cooling system or nickel (Ni) which is a modern nuclide thereof.
    A method of injecting iron into a refrigerant and ferritizing and fixing nickel or cobalt contained in the refrigerant on the surface of a fuel enclosure tube is effective in reducing nickel concentration or cobalt concentration in the refrigerant. The reason mentioned above is that the surface of the fuel enclosure tube has an overwhelmingly large surface area and that the ferritization of nickel or cobalt progresses easily on the surface of the fuel enclosure tube by performing boiling and condensation.
    Techniques for reducing radiation exposure which are proposed as ordinary techniques for reducing radiation exposure are described, for example, in the following patent documents 1-4. (1) Japanese Laid-Open Unexamined Patent Application (published) No. 2000-9889 (JP-A-2000-9889) as patent document 1 describes the technique for suppressing the radiation dose around a reactor cooling system by injecting iron into a coolant and ferritizing and oxidizing nickel (Ni) or cobalt (Co), which are enclosed in the coolant. , on the surface of a fuel housing tube. (2) Japanese Laid-Open Unexamined Patent Application (published) No. 5-288893 (JP-A-5-288893) as patent document 2 describes the technique for suppressing the radiation dose around a reactor cooling system by injecting iron oxide obtained from iron ion into a coolant and ferritizing and fixing Ni or Co, which are enclosed in the coolant. , on the surface of a fuel housing tube. (3) Japanese Published Unexamined Patent Application (Published) No. 7-20277 (JP-A-7-20277) as patent document 3 describes the technique for suppressing the radiation dose around a reactor cooling system by injecting iron oxide into a coolant and ferritizing and fixing Ni or Co, which are contained in the coolant, on the surface of a fuel housing tube. (4) Japanese Published Unexamined Patent Application (Published) No. 63-229394 (JP-A-63-229394) as patent document 4 describes the technique 3 for suppressing the radiation dose around a reactor cooling system by reinjecting a metal oxide (crud: "chalk river unclassified deposit") which is filtered at the capacitor filter of the reactor cooling system into a reactor core and ferritize and fix Ni or Co, which are enclosed in the refrigerant, on the surface of a fuel enclosure tube.
    According to patent document 1, it is known that iron ions are obtained by electrolysis operation. The speed of generation of the iron ions varies continuously according to a voltage state between the electrodes or the surface of the electrodes. It is therefore not easy to supply the coolant in the reactor cooling system with iron with a uniform fate, and it is difficult to control the iron concentration in the coolant. Furthermore, the workload for handling the devices used in the electrolysis operation is large because the electrolysis operation requires mechanical cleaning to remove oxide film generated on the surface of the electrodes and so on.
    As long as iron oxide has lower reactivity in comparison with iron ion, one cannot expect a good ferritization of the iron oxide compared to Ni or Co even if the iron oxide injected into the coolant has reached the reactor core. Incidentally, a situation with a power plant operation that has too high a concentration of iron in the coolant is not preferable.
    In view of the above circumstance, an object of the present invention is to provide a method of reducing radiation exposure which can ferritize nickel and cobalt well and then fix well ferritized nickel and cobalt on the surface of the fuel capsule tube by injecting iron into the coolant. check the iron concentration in the coolant and reduce the workload for handling the device used to inject the iron into the coolant.
    The above objects can be achieved according to an aspect of the present invention, which is to provide a method of reducing radiation exposure which comprises the steps of: injecting iron into a coolant flowing from the reactor cooling system to the reactor core of a nuclear power plant and ferritizing and fix radionuclides or modernuclides thereof, which are enclosed in the refrigerant, on the surface of a reactor core structure, using an iron citrate, which is a soluble organic iron, as the iron to be injected into the refrigerant.
    Furthermore, another aspect of the present invention is to provide a method of reducing radiation exposure comprising the steps of: injecting iron into a coolant flowing from the reactor cooling system to the reactor core of a nuclear power plant and ferritizing and fixing radionuclides or modernuclides thereof contained therein. the refrigerant, on the surface of a reactor core structure, wherein an iron oxalate or an iron fumarate having a particle diameter of 3 μm or less is used as the iron to be injected into the refrigerant.
    In the example of the present invention, a soluble organic iron may be used with an indigestible iron compound. Furthermore, an iron oxy hydroxide is preferably used as the indigestible iron compounds. In accordance with the present invention comprising the above-described feature, nickel and cobalt can be well ferritized and then fixed to the surface of the fuel enclosure tube by injecting iron into the coolant, whereby the iron concentration in the coolant can be easily controlled and the workload, for handling the device used for injecting iron into the coolant can be reduced.
    Brief Description of the Drawings Fig. 1 is a configuration diagram showing a reactor cooling system of a BWR power plant to which the method of reducing radiation exposure is applied in the embodiment, Fig. 2 is a graph representing a result of a verification test (solubility test) according to the method of reduction of radiation exposure in the embodiment, Fig. 3 is a graph representing a result of a verification test (reaction test) according to the method of reducing radiation exposure in the embodiment, Fig. 4 is a graph representing a result of a verification test (adhesion test). ) according to the method of reducing radiation exposure in the embodiment, Fig. 5 is a graph representing a result of a verification test (scattering test) according to the method of reducing radiation exposure in the embodiment and Fig. 6 is a table representing a result of a verification test (reaction In the figures (in particular in Fig. 1), the reference numerals RC, MS, FD, RRS, CUW, RHR and P for the respective reactor cooling system , the main steam system, the feed water system, the reactor recirculation system, the reactor water clean-up system, the residual heat removal system, the residual heat removal system ”) and the point where iron is injected.
    Preferred Embodiments of the Invention In the following and on the basis of examples, which are applied to the reactor cooling system of the boiling water type reactor (hereinafter referred to as "BWR", "boiling water reactor"), embodiments of the radiation exposure reduction process according to the present invention invention to be described with reference to the accompanying drawings.
    [First Embodiment] Fig. 1 is a configuration diagram showing a BWR power plant to which the radiation exposure reduction method is applied in a first embodiment. Fig. 1 also shows the reactor structure, reactor cooling system RC (reactor cooling system), reactor water cleaning system CUW ("reactor water clean-up system") and residual heat removal system RHR ("residua | heat removal system") of the BWR.
    In the reactor cooling system RC in BWR 1, a coolant (water) heated by a reactor core 102 is sent in a reactor pressure vessel 101 as high temperature steam and pressure to main steam pipe 103 in the main steam system MS and used for driving (rotating) a turbine 104 which is a power source for a power generator. Incidentally, the steam emitted from the turbine 104 is saved as condensed water and removed impurities for the purpose of corrosion of devices 6 or pipes, tubes or the like which are included in the reactor cooling system RC. After the condensed water has been heated to a specified temperature in order to be supplied as a coolant to the reactor vessel 101, the condensed water is again supplied to the reactor pressure vessel 101 through a supply water pipe 105 in the supply water system FD. The reference numeral 106 shown in FIG. 1 denotes a supply water pump.
    Further, in the reactor recirculation system RRS ("reactor recirculation system"), after the refrigerant in the reactor pressure vessel 101 has been introduced into the circulation system pipe 107 and pressurized by the circulation pump 108, the refrigerant is injected and supplied from the jet pump 109 to the reactor pressure vessel. 108, the control of the reactor core effluent is performed via the control of the coolant supply quantity and the coolant is stirred in the reactor pressure vessel 101.
    In the reactor water cleaning system CUW, after the heat exchanger 110 (regenerative heat exchanger 110a, non-regenerative heat exchanger 110b) cools down a branch of the coolant introduced into the circulation system pipe 107 at a temperature suitable for filtration and demineralization, the pump is pressed 111. impurities in the refrigerant removed by the filtration and demineralization device 112. The refrigerant produced by the cleaning process is cooled and introduced into the reactor pressure vessel 101 through the inflow water pipe 105 into the inflow water system FD. Furthermore, in the residual heat removal system RHR, other branches of the coolant of the pump 113 are pressurized and cooled by the heat exchanger 114 down to a predetermined temperature.
    The stainless steel or nickel-based alloy, which has excellent mechanical strength and is corrosion resistant even at high temperature and pressure, is used as a material for devices or pipes which are in contact with high temperature refrigerant and pressure which flows in the reactor cooling system RC. However, already using the stainless steel or nickel-based alloy, since stainless steel or nickel-based alloy is not associated with corrosion reactions, oxide film is produced on the surface of the stainless steel or nickel-based alloy and crud (metal oxide) ionic impurity comprising nickel nuclides consisting of particles can be introduced into the coolant. The material contained in the refrigerant such as crud, ionic impurity or the like is collectively called a "corrosion product" and is finally introduced into the reactor core 102 through the reactor cooling system RC, the reactor water purification system CUW and the residual heat removal system RHR. The corrosion products introduced into the reactor core 102 become radioactive by neutron radiation on the reactor core 102, in particular on the surface of the fuel enclosure tube, and are thus transformed into a radioactive corrosion product. For example, nickel 58 (sam) or cobalt 59 (5900), which is included in the corrosion product, decomposes into cobalt 58 (58Co) or cobalt 60 (6 ° Co), which emit high-energy gamma radiation. In addition, a radioactive corrosion product is also generated by the loss or elution of metal material in the internal core structure, which is radioactive.
    The radioactive corrosion product, which contains a radioactive isotope of cobalt which is produced by performing various processes, circulates in the reactor cooling system RC along the fate of the refrigerant fl in the particulate or ionic state. Even if a portion of the radioactive corrosion product is reattached and fixed to the surface of the fuel enclosure tube or removed in the filtration and demineralization device 112 of the reactor water purification system CWU or other cleaning device, the other portion of the radioactive corrosion product is attached to the inner surface. of devices or pipes included in the reactor cooling system RC and thereby increase the radiation dose (amount of radiation) around the reactor cooling system RC. The method of reducing radiation exposure in the embodiment is used for the purpose of reducing the radiation dose around the RC cooling system RC.
    The method of reducing radiation exposure in the embodiment is a method which suppresses the radiation dose around the reactor cooling system RC by injecting iron into the coolant flowing from the reactor cooling system RC to the reactor core 102 in BWR 1 and ferritizing and fixing radionuclides or parent nuclides within them. , on the surface of the reactor core 102, in particular the surface of the fuel rod. The method of reducing radiation exposure in the embodiment comprises four procedures 1-4 (random order) as follows: 8 Procedure 1: Prepare a tank in which aqueous solution of the iron citrate (soluble organic iron) accumulates and a high pressure injection pump which can inject the iron citrate solution in the reactor cooling system RC which is under high pressure.
    Procedure 2: A point where the iron citrate solution is injected is placed at the circulation system pipe 107 in the reactor cooling system RC or a discharge side of the supply water pump 106 installed in the supply water pipe 105 in the reactor cooling system RC. The reference letter P shown in Fig. 1 denotes the point where iron is injected.
    Since the iron dissolved in the iron citrate solution is an ionic state, the iron dissolved in the ferric citrate solution has a high reactivity with other chemical species. Therefore, a closer distance (extended) from the iron injection point P to the reactor pressure vessel 101 is better with respect to reducing a loss for transporting iron ions which are to be transported to the reactor core 102. Furthermore, the iron injection point P may be one or more.
    Procedure 3: Iron injection from each injection point P is started at a time when the coolant circulates, for example in the start-up operation or in the final operation during operation of the power plant.
    Procedure 4: The amount of iron in the coolant is checked so that the iron concentration in the coolant at the time of inflow of supply water is approximately 0.05 to 0.5 ppb. The reason for controlling the amount of iron injected into the refrigerant is that if the iron concentration in the refrigerant at the time of inflow of inflow water is approximately 0.05 to 0.5 ppb, one can ignore effects that affect properties of the power plant such as the electrical conductivity .
    Next, the effect of the method of reducing radiation exposure will be described with reference to the result of a verification test.
    The verification test is performed to verify the chemical properties of the iron citrate regarding a controllability of the iron concentration of the refrigerant, a generation rate for the nickel ferrite and cobalt ferrite and an attachment property for each ferrite on the fuel enclosure tube. The verification test includes the solubility test, the reaction test and the adhesion test.
    [Solubility test] 9 The solubility test is a test to verify the chemical properties of the iron citrate with respect to the controllability of the iron concentration in the refrigerant. The procedures (steps) for the solubility test will be described.
    Step S101: Add the iron citrate to 500 ml of pure water in the beaker so that the iron concentration of the solution is 150 ppm.
    Step S102: Radiate ultrasonic waves in the iron citrate solution in the beaker by stirring with a spatula. The stirring operation, ie the operation to evenly distribute the reagents, continues for 10 minutes. After the treatment of ultrasonic waves, leave the beaker as it is.
    Step S103: Collect from the suspension fluid at 10, 20,, 45 and 60 minutes, respectively, after the treatment of ultrasound waves.
    Step S104: Drop a drop of the suspension liquid on the filter whose pore size is 0.1 μm and perform a decompression filtering operation (which means an operation that filters something under reduced pressure).
    Step S105: Measure the amount of iron on the filter using an X-ray fluorescent type spectrometer.
    Fig. 2 is a graph representing the result of a verification test (solubility test) according to the method of reducing radiation exposure in the embodiment. In Fig. 2, the horizontal axis represents a elapsed time from the reference time (0 minutes) immediately after the processing of ultrasonic waves in step S102 starts. Furthermore, the vertical axis represents the suspension component and the ion component of the total amount of iron (the sum of the suspension component and the ion component).
    As shown in Fig. 2, the iron, which is a component of an iron ion citrate, is ionized with time and then stops almost completely ionizing after about 60 minutes from the start of the ultrasonic wave procedure.
    As a result, (a) The component iron and iron citrate injected into the refrigerant is rapidly (within about 60 minutes) converted and almost completely to iron ions and circulates in the reactor cooling system RC. Or the component iron injected into the refrigerant is rapidly and almost completely converted to iron ion in the tank where the iron citrate solution accumulates, after injection of the iron citrate solution into the refrigerant and thus circulates in the reactor cooling system RC. Thus, since the iron citrate is water-soluble, i.e. high dispersing property, iron can be supplied to the coolant in the reactor cooling system RD in uniform flow and the iron concentration in the coolant can thus be easily controlled. (b) As a result of using the iron citrate as the iron injected into the refrigerant, it is unnecessary to carry out the electrolysis operation in order to obtain the iron ion. Thus, as in the case of the use of electrolysis operation, mechanical cleaning to remove oxide film generated on the surface of the electrodes or the like is unnecessary, and thus the working load on operating devices for injecting iron ion can be reduced.
    [Reaction test] The reaction test is a test to verify the chemical properties of the iron citrate with respect to the generation rate of nickel ferrite and cobalt ferrite. The procedures (steps) of the reaction test will be described.
    Step S201: Prepare three types of iron reagents which are the iron reagents consisting of particles, the iron citrate reagents and the iron oxalate reagents respectively and inject into the test tube (volume: 20 ml) manufactured by Teflon (registered trademark) so that iron weight is 2.5 mg from each iron reagent.
    Step S202: Add 15 ml of pure water to each test tube and further add nickel sulphate solution so that the weight of nickel is 1.25 mg.
    Step S203: Irradiate the ultrasonic wave into each test tube and disperse the solute evenly in each test tube.
    Step S204: Place each test tube in the autoclave and heat to 285 ° C (degrees) for about 17 hours. Here, the heating temperature (285 ° C) is set as a temperature that simulates coolant temperature in the reactor cooling system RC 1 BWR 1.
    Step S205: After heating the test tube, filter the reactant in each test tube with the filter whose pore size is 0.1 μm. Then measure a reactant shape and a reactant composition ratio using an X-ray fluorescent type spectrometer and an X-ray diffractometer.
    Fig. 3 is a graph representing the result of a verification test (reaction test) according to the method of radiation exposure reduction in the embodiment. As shown in Fig. 3, the excess form of iron consists mostly of nickel ferrite (NiFe2O4) and hematite (Fe2O3), under the condition that the iron consisting of particles reacts with the nickel sulphate. The excess form of iron consists mostly of nickel ferrite, provided that the iron citrate reacts with the nickel sulphate. Although the excess form of iron mostly consists of nickel ferrite, provided that the oxalate iron reacts with the nickel sulphate, the iron oxalate remains somewhat (approximately 5%) in the injection form.
    That is, because the iron citrate has a high reactivity with nickel, the nickel ferrite is easily produced in comparison with the iron consisting of particles or the iron oxalate. Furthermore, since the iron citrate also has a high reactivity with cobalt, which is similar to a chemical property of nickel, it seems that the cobalt ferrite is easily produced in comparison with the iron consisting of particles or the iron oxalate.
    As a result, (c) By injecting iron citrate into the refrigerant, nickel and cobalt can be well ferritized compared to a case where an iron consisting of particles or an iron oxalate is injected into the refrigerant.
    [Adhesion test] The adhesion test is a test to verify the chemical properties of iron citrate with respect to the adhesiveness of the nickel ferrite or cobalt ferrite on the fuel enclosure tube. The procedure (steps) for the Adhesion Test will be described below.
    Step S301: Prepare two kinds of iron reagents which are respectively the reagent for iron consisting of particles and the iron citrate reagent and produce a solution in which the iron concentration is 100 ppb and the nickel ion concentration is 10 ppb for each iron reagent.
    Step S302: Allow each solution produced at step S301 to flow through test equipment which simulates a boiling environment in the fuel enclosure tube and around it in the BWR1. The flow rate through the test equipment for each solution produced in step S301 is 250 ml / min and the time to run each solution produced in step S301 is about 100 hours. The test equipment is configured so that a test part (a tube consisting of zircaloy with an outer diameter of about 12 mm and a length of about 200 mm) which simulates the 12 fuel capsule tube is used, the case heater being covered with a test part, a liquid being supplied to the test part surface and the injected liquid is overheated and boiled.
    Step S303: Measure the amount of nickel adhering to the surface of the test part upon completion of the solution flow in step S302.
    Fig. 4 is a graph representing the result of a verification test (adhesion test) according to the method of radiation exposure reduction in the embodiment.
    As shown in Fig. 4, in the case that the solution of iron consisting of particles passes through the test equipment, the amount of nickel adhering to the surface of the test part is 490 mg. Furthermore, if the iron citrate solution passes through the test equipment, the amount of nickel that adheres to the surface of the test part is 1600 mg. That is, the iron citrate allows nickel to easily adhere to the test part in comparison with the iron consisting of particles. Furthermore, since the iron citrate also has a high reactivity with cobalt, which is similar to a chemical property of nickel, it seems that the iron citrate also allows cobalt to be easily fixed on the test part in comparison with the iron consisting of particles.
    As a result, (d) By injecting iron citrate into the coolant, nickel or cobalt can be easily fixed to the surface of the fuel capsule tube as compared with a case where particles consisting of particles or an iron oxalate are injected into the coolant. In addition, in the case where iron citrate is injected into the coolant, the adhesion amount of nickel is about three times greater than the adhesion amount of nickel in the case where iron consisting of particles is injected into the coolant.
    According to the method of reducing radiation exposure in the first embodiment and as is apparent from the contents described above, (1) in the case of the refrigerant circulating as in the case of a power plant in operation and so on, nickel citrate is used as the iron injected into the refrigerant. . Nickel and cobalt can be well ferritized and then fixed to the surface of the fuel enclosure tube by measures where iron is injected into the coolant. Furthermore, the control of the iron concentration in the coolant becomes simple and the workload for handling the device when injecting iron into the coolant can be reduced. 13 (2) Further, the point where the iron citrate solution is injected into the coolant is placed at the circulation system pipe 107 of the reactor cooling system RC or a discharge side of the supply water pump 106 installed in the supply water pipe 105 of the reactor cooling system RC. That is, the point where the iron citrate solution is injected is set at the point closer to the reactor pressure vessel 101. Thus, excess iron injection, with respect to decreasing amount, can adhere to devices or pipes included in the reactor cooling system RC before the iron citrate which has high reactivity reaches to the reactor core 102, is suppressed and the input to the power plant operation can be reduced.
    [Second Embodiment] The second embodiment is configured under the same conditions as in the first embodiment except that the iron reagent used in procedures 1-4 of the radiation exposure reduction method in the second embodiment is changed to an iron reagent different from the iron reagent used in procedures 1-4 of the method of reducing radiation exposure in the first embodiment.
    In the method of reducing radiation exposure in the second embodiment, a suspension produced by adding iron oxalate with a particle diameter of 1-3 μm to pure water is used as iron which is injected into the reactor cooling system RC in BWR 1. The iron oxalate has here weak solubility with respect to the coolant compared to the iron citrate. Incidentally, as well as other points which are substantially similar to those in the first embodiment, the explanation of these will be omitted.
    Next, the effect of the method of reducing radiation exposure in the embodiment will be described with respect to the result of a verification test (scattering test).
    [Dispersion test] The diffusion test is a test to verify the properties of the iron oxalate, which has low solubility with the water (coolant), regarding the controllability of the iron concentrate in the coolant. The procedure (steps) in the diffusion test will be described below.
    Step S401: Prepare two types of iron reagents which are respectively the reagent for commercially available iron oxalate and the reagent for iron oxalate 14 with a small particle diameter and produce suspension liquid for each iron reagent in the beaker. In this case, the diameter of the particles for the most commercially available iron oxalate is several tens of micrometers (pm) and the particle diameter of the j est iron oxalates with a small particle diameter is 1-3 μm.
    Step S402: Radiate ultrasonic waves into the suspension liquid in the beaker by stirring with a medical spoon in the beaker. The stirring operation, i.e. the operation to evenly disperse the reagents, continues for 10 minutes. Leave the beaker as it is after the ultrasound wave treatment.
    Step S403: Check the liquid abundance of the iron oxalate in the suspension liquid in each beaker at 10, 20, 30, 45 and 60 minutes after the ultrasound treatment.
    Fig. 5 is a graph representing the result of a verification test (scattering test) according to the method of reducing radiation exposure in the embodiment.
    In Fig. 5, the horizontal axis represents a elapsed time from the reference time (0 minutes) immediately after the ultrasonic wave treatment in step S403 begins. Furthermore, the vertical axis represents the degree of liquid overflow of the iron oxalates in the beaker. The liquid overflow rate is the amount of a suspension component (in addition to the amount of sediment component) of the total amount of iron oxalate injected into the beaker. Incidentally, "the first example of small particle diameter iron oxalate" and "the second example of small particle diameter iron oxalate" shown in Fig. 5 are the same test conditions as the particle diameter or another test condition.
    As shown in Fig. 5, most of the commercially available iron oxalate (particle diameter is one tenth of a μm) precipitates at 60 minutes after the ultrasonic wave treatment. On the other hand, since most of the iron oxalate with small particle diameters (the particle diameter is 1-3 μm) does not precipitate even at 60 minutes after the ultrasonic treatment, the liquid abundance of the iron oxalate is about 80% or more. That is, iron oxalate for which the particle diameter is 1-3 μm has a much higher spread compared to iron oxalate for which the particle diameter is tens of μm.
    As a result, (e) if the iron oxalate (low solubility with the refrigerant) having a particle diameter of 1-3 μm is used as the iron to be injected into the refrigerant, because the iron oxalate has a high dispersibility, then the iron oxalate in the refrigerant is retained. long-term in the suspended state in the refrigerant and thereby circulating in the reactor cooling system RC in the suspended state. Thus, iron in a uniform flow can be supplied to the coolant in the reactor cooling system RC and the iron concentration in the coolant can thus be easily controlled.
    Incidentally, methods for reducing the particle diameter of iron composite are a method for suppressing particle growth by being a high concentration of material when generating the iron oxalate, a method for physically crushing the commercially available iron oxalate and so on. (f) if the iron oxalate is used as iron to be injected into the coolant, which is the case when using the electrolysis operation, then the work (operations) such as the mechanical cleaning to remove oxide film generated on the surface of the electrodes is unnecessary. Since the iron oxalate has a high spreading property, the workload for the operation of touching the iron oxalate accumulated in the tank can also be reduced. (g) If the iron oxalate is injected into the refrigerant, as is the case for injecting iron consisting of particles into the refrigerant, then nickel can be well ferritised (see Fig. 3).
    In the same way, cobalt, which is similar to a chemical property of nickel, can also be ferritised well. (h) The iron oxalate has low solubility with the water (coolant) and therefore mostly becomes a suspension component consisting of particles. Thus, if the iron oxalate is injected into the coolant, a loss for transporting iron ions to the reactor core 102 can be reduced compared to the case of injecting the iron citrate.
    Which is evident from the contents described above according to the method of reducing radiation exposure in the second embodiment, (3) In the case of the refrigerant circulating as in the case of a power plant in operation and so on, an iron oxalate having a particle diameter of 3 μm or less is used as the iron injected into the refrigerant. Therefore, nickel or cobalt can be well ferritized and then fixed to the surface of the fuel enclosure tube by acts in which iron is injected into the coolant. Furthermore, the control of the iron concentration in the coolant becomes simple and the workload for handling the device used after injection of iron in the coolant can be reduced.
    [Third Embodiment] The third embodiment is configured under the same conditions as in the first embodiment except that the iron reagents used in procedures 1-4 of the radiation exposure method in the third embodiment are changed to an iron reagent different from the iron reagent used in procedures 1. -4 in the method of reducing radiation exposure in the first embodiment.
    In the method of reducing radiation exposure in the third embodiment, a suspension produced by adding a reagent (hereinafter referred to as "mixing iron reagent") produced by mixing the iron citrate and an iron oxyhydroxide (FeO (OH)) is added to pure water is used as iron which is injected into the reactor cooling system RC in BWR 1. The explanation of these will otherwise be omitted as well as other points which are substantially similar to those in the first embodiment.
    In the following, the effect of the method of reducing radiation exposure in the embodiment will be described with reference to the result of a verification test (reaction test).
    [Reaction test] The reaction test is a test to verify the chemical properties of the iron oxyhydroxide reagents with respect to the generation rate of nickel ferrite and cobalt ferrite. The reaction test for the iron oxyhydroxide is here the same case as the reaction test (steps S201 to S205) described in the first embodiment.
    The reaction test for the iron oxyhydroxide which is a component of the mixing iron reagents is performed by injecting an amount of nickel into the suspension produced by adding the iron oxyoxide in pure water and then analyzing the reagents thereof.
    Fig. 6 is a table representing a result of a verification test (reaction test) according to the method of reducing radiation exposure in the embodiment. In Fig. 6, "BEFORE REACTION TEST" represents the excess ratio of the suspension and nickel before the reaction test starts 17 and "REACTION TEST RESULT 1" and "REACTION TEST RESULT 2" respectively represent two experimental results obtained by performing the reaction test twice under the same conditions. "REACTION TEST RESULT 1" represents the excess ratio of the reactant in a first component analysis and "REACTION TEST RESULT 2" represents the excess ratio of the reactant in a second component analysis. In addition, both the first component analysis and the second component analysis are performed after 17 hours from the time when iron oxyhydroxide and nickel begin to react.
    As shown in Fig. 6, in the first component analysis, by the reaction of iron oxyoxide and nickel, 37% of the total amount remains as iron oxyoxide, 30% of the total amount is produced as nickel ferrite and 34% of the total amount is produced as hematite. In the second component analysis, by the reaction of iron oxyhydroxide and nickel, 14% of the total amount remains as iron oxyhydroxide which is the material of the mixed iron reagent, 52% of the total amount is produced as nickel ferrite and 34% of the total amount is produced as hematite .
    Since the residual iron oxyhydroxide also reacts with nickel, nickel ferrite or hematite is gradually produced. Furthermore, the hematite produced by the reaction with said nickel reacts and thereby the nickel ferrite is produced mildly. That is, the iron oxyhydroxide as a reagent (medical agent) for ferritization is long-lived, even though the reactivity that ferritizes the nickel of the iron oxyhydroxide is low compared to the iron citrate. Incidentally, it appears that the iron oxyoxide also reacts with cobalt, which is similar to a chemical property of nickel, by a similar reaction process, and the iron oxyoxide is persistent as a reagent for ferritization.
    Since the reactivity with iron citrate and nickel is good (see Fig. 3), the reactivity with iron citrate and cobalt is also considered good in a similar case of the reactivity with iron citrate and nickel. Thus, if iron citrate is injected into the refrigerant, nickel (cobalt) can be well ferritized. However, since the reactivity with iron citrate and nickel is high, the iron concentration of the refrigerant decreases rapidly and thereby the ferritization of nickel (cobalt) does not continue for long. This means that injection of iron citrate into the refrigerant has a disadvantage in deteriorating the continuation of the function (reaction) of the ferritization with nickel (cobalt) is not good.
    Since the iron oxyhydroxide is also indigestible, the reactivity with the iron oxyoxide and nickel is not as high as the reactivity with iron citrate and nickel. Under the condition that nickel is present in the iron mixing reagent, tens of percent of the total amount of iron oxyoxide remains as long as 17 hours later (see Fig. 6) while the iron citrate is consumed within 60 minutes by production of the nickel ferrite (see Fig. 3).
    As a result, (i) if the iron mixing reagents produced by mixing the iron citrate and an iron oxyhydroxide (FeO (OH)) injected into the refrigerant, nickel or cobalt can be well ferritized by injecting the iron citrate into the refrigerant and the ferritization operation (function) of nickel or cobalt can be continued for a long time by injecting the iron oxyhydroxide into the refrigerant.
    As is apparent from the above-described contents of the method of reducing radiation exposure in the third embodiment, (4) when iron is injected into the coolant, if the iron oxyoxide is used with the iron citrate, nickel or cobalt may be well ferritized and then fixerated on the surface of the fuel capsule. through actions where iron is injected into the refrigerant.
    Furthermore, the control of the iron concentration in the coolant becomes simple and the workload for handling the device used in injecting iron into the coolant can be reduced. Furthermore, the ferritization operation (function) of nickel or cobalt can continue for a long time.
    While the embodiments of the method of reducing radiation exposure according to the present invention are described in accordance with the first to third embodiments, the present invention is not limited to the method described in each embodiment. Furthermore, various design changes, additions, omissions, presentations or the like in the form of the methods described herein may be made without departing from the scope of the invention.
    For example, although the iron citrate, which is used as an example of iron injected into the refrigerant, is explained in the first embodiment, the iron injected into the refrigerant may be organic iron which is soluble in water (the refrigerant). While the iron oxalate having a particle diameter of 1-3 μm and explained in the second embodiment is used as an example of iron oxalate injected into the refrigerant, it is preferable that the diameter (for example 1 μm or less) of the iron oxalate injected into the refrigerant becomes as small as possible. The above-mentioned reason is that the smaller the diameter of the iron oxalate, the greater the dispersal property of the liquid and thereby the control of the iron concentration in the refrigerant can be improved and a reduced workload for the operation of stirring if the iron oxalate accumulated in the tank can be achieved. Incidentally, instead of iron oxalate, organic iron such as iron fumarate or the like can be used as the iron to be injected into the refrigerant.
    While the mixture produced by mixing the iron citrate and the iron oxyhydroxide is explained in the third embodiment and used as an example of iron injected into the coolant, organic iron such as iron oxalate, iron fumarate or the like can be used as iron used with the iron oxyhydroxide. In addition, another iron compound can be used instead of the iron oxyhydroxide. In order to ensure in this respect the continuation of the function of the ferritization of nickel or the like, the dispersing property of the iron in water (coolant) is preferably higher. Furthermore, the solubility of the iron compound in water (coolant) is preferably lower.
    In addition, in the BWR power plant that includes the internal pump, the injection point pre-iron can be set at the reactor water purification system or the like instead of at the reactor circulation system.
    权利要求:
    Claims (7)
    [1]
    A method of reducing radiation exposure comprising the steps of: injecting iron into a coolant flowing from the reactor cooling system to the reactor core of a nuclear power plant and ferritizing and fixing radionuclides or modernuclides thereof contained within the coolant on the surface of a reactor core structure. An iron citrate, which is a soluble organic iron, is used as the iron to be injected into the refrigerant.
    [2]
    A method of reducing radiation exposure according to claim 1, wherein an indigestible iron composite is used with the soluble organic iron.
    [3]
    A method of reducing radiation exposure according to claim 1, wherein an iron oxyhydroxide is used as the indigestible iron compounds.
    [4]
    A method of reducing radiation exposure according to claim 1, wherein a point at which the soluble organic iron is injected into the coolant is added to a reactor circulation system or an outlet side of a supply pump in a supply water system.
    [5]
    A method of reducing radiation exposure comprising the steps of: injecting iron into a coolant flowing from the reactor cooling system to the reactor core of a nuclear power plant and ferritizing and fixing radionuclides or modernuclides thereof contained within the coolant on the surface of a reactor core structure. an iron oxalate or an iron fumarate having a particle diameter of 3 μm or less is used as the iron to be injected into the refrigerant.
    [6]
    A method of reducing radiation exposure according to claim 5, wherein an indigestible iron compound is used with the soluble organic iron. 21
    [7]
    A method of reducing radiation exposure according to claim 6, wherein an iron oxyhydroxide is used as the indigestible iron compounds.
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    同族专利:
    公开号 | 公开日
    JPWO2010053079A1|2012-04-05|
    JP5106640B2|2012-12-26|
    WO2010053079A1|2010-05-14|
    US8798225B2|2014-08-05|
    US20110211663A1|2011-09-01|
    SE536022C2|2013-04-02|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US4476047A|1982-03-22|1984-10-09|London Nuclear Limited|Process for treatment of oxide films prior to chemical cleaning|
    JPH0476079B2|1984-03-01|1992-12-02|Hitachi Ltd|
    JPH0631816B2|1986-10-03|1994-04-27|株式会社日立製作所|Method and apparatus for suppressing elution of radioactive material into cooling water in nuclear power plant|
    US5015436A|1988-03-30|1991-05-14|Hitachi, Ltd.|Water-cooled direct cycle nuclear power plant|
    US5024805A|1989-08-09|1991-06-18|Westinghouse Electric Corp.|Method for decontaminating a pressurized water nuclear reactor system|
    US5245642A|1991-10-31|1993-09-14|General Electric Company|Method of controlling co-60 radiation contamination of structure surfaces of cooling water circuits of nuclear reactors|
    JP2808970B2|1992-03-19|1998-10-08|株式会社日立製作所|Nuclear power plant, its water quality control method and its operation method|
    JPH05288893A|1992-04-14|1993-11-05|Hitachi Ltd|Control method of concentration of chromium of boiling water nuclear power plant|
    JP2912525B2|1993-07-01|1999-06-28|株式会社日立製作所|BWR plant reactor water control method and apparatus|
    US5608766A|1993-10-29|1997-03-04|General Electric Company|Co-deposition of palladium during oxide film growth in high-temperature water to mitigate stress corrosion cracking|
    JP3289679B2|1998-06-19|2002-06-10|株式会社日立製作所|Water quality control method for boiling water nuclear power plant|
    JP3587161B2|2000-10-26|2004-11-10|株式会社日立製作所|Water quality control method|
    JP3945780B2|2004-07-22|2007-07-18|株式会社日立製作所|Radionuclide adhesion suppression method and film forming apparatus for nuclear plant components|
    JP5059325B2|2006-01-06|2012-10-24|株式会社日立製作所|Method and apparatus for inhibiting corrosion of carbon steel|
    JP2007192672A|2006-01-19|2007-08-02|Hitachi Ltd|Method and device for forming ferrite coating film on surface of carbon steel member in nuclear power plant|
    JP5591454B2|2008-04-25|2014-09-17|株式会社東芝|Reactor water radioactivity reduction method and nuclear power plant|DE102008043403B4|2008-11-03|2019-06-27|Robert Bosch Gmbh|Fan, method for mounting a fan wheel and device|
    法律状态:
    2019-07-02| NUG| Patent has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    JP2008283517|2008-11-04|
    PCT/JP2009/068792|WO2010053079A1|2008-11-04|2009-11-04|Method for reducing radiation exposure|
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