JP2012021777A - Device for predicting exit hydrogen concentration of exhaust gas recombination device and method of predicting exit hydrogen concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for predicting the exit hydrogen concentration of an exhaust gas recombination device in a boiling water reactor nuclear power plant from inflow conditions of gas and the state of a catalyst.SOLUTION: A device for predicting the exit hydrogen concentration of an exhaust gas recombination device includes: an input device 7 which inputs the flow rate of components of exhaust gas flowing into the exhaust gas recombination device within a gaseous waste processing system of a boiling water reactor nuclear power plant, the temperature of the exhaust gas, an index indicating the state of a catalyst in the exhaust gas recombination device, and the amount of inflow of a poisoning material that affects the properties of the catalyst; a calculating device 2 for calculating the hydrogen concentration at the exit of the exhaust gas recombination device from information input by the input device 7; and a display device for displaying the hydrogen concentration calculated or temporal change of the hydrogen concentration.

Description

  The present invention relates to a boiling water nuclear power plant, and more particularly to prediction of a recombiner outlet hydrogen concentration of a boiling water nuclear planton suitable for application to a boiling water nuclear power plant having a recombination device in an off-gas system. The present invention relates to an apparatus and a method for predicting outlet hydrogen concentration.

In a situation where global warming due to carbon dioxide (hereinafter abbreviated as CO ₂ ) becomes serious, the demand for nuclear power generation systems that do not generate CO ₂ during operation is increasing year by year as a future energy supply source.

  The nuclear power generation system includes a boiling water reactor plant (hereinafter referred to as a BWR plant) and an improved boiling water reactor plant (hereinafter referred to as an ABWR plant). In such a BWR plant, the cooling water is heated by the heat generated by the nuclear fission of the nuclear fuel material contained in the plurality of fuel assemblies loaded in the core in the reactor pressure vessel to generate steam. The steam generated in the reactor pressure vessel is fed directly to the turbine. During operation of the BWR plant, the cooling water in the reactor core is decomposed by irradiation with radiation such as neutrons and γ rays generated by fission, and hydrogen and oxygen are generated. Such hydrogen and oxygen are transferred to the turbine system together with the steam. At this time, the steam finally becomes condensed water in the condenser, but hydrogen and oxygen remain as noncondensable gases. The non-condensable gas inside the condenser is exhausted after ensuring a safe state. In particular, a mixed gas of hydrogen and oxygen has a risk of combustion when recombined in a gas phase reaction. For this reason, in the BWR plant, a recombiner filled with a combustion catalyst that promotes recombination of hydrogen and oxygen is provided in the off-gas piping, and this recombiner recombines hydrogen and oxygen generated by radiolysis. ing. Hydrogen and oxygen are recombined by the reaction shown in (Formula 1).

  Recently, when the BWR plant is started, an event has occurred in which the operation of the BWR plant has to be stopped due to an increase in the hydrogen concentration in the gas discharged from the recombiner provided in the off-gas piping.

  In low-pressure turbines installed upstream of the recombiner, linseed oil has been conventionally used as a seal material for the packing part. However, due to the use of linseed oil, the airtightness was low and the turbine efficiency was lowered. Therefore, the sealing material was changed to liquid packing in order to improve the decrease in turbine efficiency. The occurrence time of the hydrogen concentration increase event of the gas discharged from the recombiner is almost the same as the time when the sealant was changed, and silicon was detected from the catalyst recovered from the recombiner. .

  [Non-patent document 1] [Non-patent document 2] [Non-patent document 3] As disclosed in [Non-patent document 2], a small amount of hexamethyldisiloxane (HMDS) is generated from the liquid packing even at room temperature, and this is the electrode of the combustible hydrogen sensor. There are many examples of research on the deterioration of performance due to adhesion.

Karl Arnby, Mohammad Rahmani, Mehri Sanati: Applied Catalysis B, pp.1-7 (2004) Masahiko Matsumiya, Woosuck Shin, Fabin Qiu et al: Sensors and Actuators B, pp516-522 (2003) Jean-Jacques Ehrhardt, Lionel Colin, Didier Jamois, et al: Sensors and Actuators B, pp117-124 (1997)

  The inventors of the present invention have examined the increase in the concentration of hydrogen contained in the gas discharged from the recombiner provided in the off-gas piping. HMDS is a chain compound containing two Si atoms, but when the number of Si atoms increases to 3 or more, it becomes a cyclic siloxane compound (hereinafter abbreviated as class D) as shown in FIG. This class D can be a poison for the combustion catalyst. As a result, HMDS generated from the liquid packing used as the sealant for the packing part in the low-pressure turbine becomes the catalyst poison of the combustion catalyst charged in the off-gas recombiner, and the catalytic action of the combustion catalyst is reduced. It is thought that the hydrogen concentration in the gas discharged from the recombiner increased. In order to maintain the safety of the nuclear power plant, it is desirable to be able to predict the hydrogen concentration in the gas discharged from the recombiner in advance.

  An object of the present invention is to provide a method for operating a boiling water nuclear plant that predicts a hydrogen concentration in a gas discharged from a recombiner provided in an off-gas piping of the boiling water nuclear plant, a boiling water nuclear plant, and An object of the present invention is to provide an apparatus for predicting hydrogen concentration.

The feature of the present invention for solving the above-described problems is as follows.
(1) Concentrations of constituents of exhaust gas flowing into the exhaust gas recombiner of the gas waste treatment system of the boiling water nuclear power plant, the temperature of the exhaust gas, the index indicating the state of the catalyst in the exhaust gas recombiner, and the catalyst An input device that inputs an inflow amount of a substance that affects performance, an arithmetic device that calculates the hydrogen concentration at the outlet of the exhaust gas recombiner from the input information, and a display device that displays the calculated hydrogen concentration. .

  (2) Preferably in (1), the component of the input exhaust gas contains at least hydrogen, oxygen, and water vapor.

  (3) Preferably, in (1) or (2), the index indicating the state of catalyst performance in the exhaust gas recombiner is the activation energy and frequency factor of the hydrogen-oxygen recombination reaction, the amount of catalyst noble metal applied, the monoxide It includes at least one of carbon (CO) chemisorption.

  (4) Preferably, in (1) to (3), the substance that affects the catalyst performance for inputting the inflow amount is an organosilicon compound.

  According to the present invention, since the hydrogen concentration in the gas discharged from the recombiner provided in the off-gas piping can be predicted, the safety of the nuclear power plant can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a structural diagram of a boiling water nuclear power plant according to embodiment 1, which is a preferred embodiment of the present invention. It is explanatory drawing which shows the chemical structure of cyclic siloxane. It is a block diagram which shows the hydrogen concentration prediction apparatus provided in the boiling water nuclear power plant of Example 1. FIG. It is a block diagram which shows the recombination reaction test apparatus used for the test of recombination reaction of hydrogen and oxygen. It is a block diagram which shows the organosilicon test apparatus for performing the influence evaluation of the organosilicon with respect to the catalyst used for a recombiner. It is a figure which shows the result of the evaluation test using the organosilicon test apparatus shown in FIG. 5, and shows the time change of outlet hydrogen concentration. It is a figure which shows the example of prediction of the exit hydrogen concentration at the time of starting of a virtual nuclear power plant. It is a figure which shows the example of prediction of the exit hydrogen concentration at the time of rated operation of a virtual nuclear power plant.

  Hereinafter, the present invention will be specifically described with reference to Examples.

A boiling water nuclear power plant (BWR plant) according to a first embodiment which is a preferred embodiment of the present invention will be described with reference to FIG. The BWR plant 137 of the present embodiment includes a nuclear reactor, a low-pressure turbine 104, a condenser 106, an off-gas system pipe 131, and a recombiner (recombining device) 101. The nuclear reactor includes a reactor pressure vessel 105 and a core 134 disposed in the reactor pressure vessel 105. A plurality of fuel assemblies 111 containing nuclear fuel material are loaded on the core 134.
A plurality of control rods 112 are provided in the nuclear reactor, and the output of the nuclear reactor is controlled by these control rods 112 being taken in and out of the core.

  A high pressure turbine (not shown) and a low pressure turbine 104 are connected to the reactor pressure vessel 105 by a main steam line 109. The low pressure turbine 104 is disposed downstream of the high pressure turbine and installed in the condenser 106. Liquid packing is used as a sealing material in the packing portion of the low-pressure turbine 104. A water supply pipe 110 connected to the condenser 106 is connected to the reactor pressure vessel 105. A water supply pump 107 is provided in the water supply pipe 110. A generator 108 is connected to the rotary shafts of the high pressure turbine and the low pressure turbine 104.

  An off-gas piping 131 is connected to the condenser 106. In the off-gas piping 131, an air extractor 115, a dehumidifying cooler 114, an exhaust gas preheater 120, a recombiner 101, and an exhaust gas condenser 113 are provided in this order. The recombiner 101 is filled with a recombination catalyst (hereinafter referred to as catalyst) that promotes the bonding reaction between hydrogen and oxygen. In this example, an example in which a catalyst having a carrier and an active component (hereinafter referred to as a metal catalyst) on a porous sponge-like metal substrate is used as the catalyst. This active component is an active component capable of converting oxygen and hydrogen into water, and activates noble metals (Pt, Pd, Rh, Ru and Ir), which are components that dissociate and activate hydrogen molecules, and oxygen molecules. It is comprised with at least 1 type chosen from Au which is a component to convert. In this embodiment, a metal catalyst in which an alumina carrier is attached to the surface of a sponge-like metal substrate and platinum (Pt), which is a noble metal, is dispersed thereon will be described as an example. In this embodiment, an example in which the recombiner 101 is filled with a metal catalyst is shown. However, the recombiner 101 in which a catalyst (ceramic catalyst) loaded with an active ingredient is packed in a granular or columnar support. It may be. Also in the case of this ceramic catalyst, the active component is an active component capable of converting oxygen and hydrogen into water, and is a noble metal (Pt, Pd, Rh, Ru and Ir) which is a component that dissociates and activates hydrogen molecules. And at least one selected from Au, which is a component that activates oxygen molecules.

  During the operation of the BWR plant 137, the cooling water in the reactor pressure vessel 105 is pressurized by a recirculation pump (or an internal pump) not shown and supplied to the core 134. This cooling water is heated by the heat generated by the nuclear fission of the nuclear fuel material in the fuel assembly 111, and a part thereof becomes steam. The steam is sequentially supplied to the high-pressure turbine and the low-pressure turbine 104 through the main steam pipe 109 to rotate the high-pressure turbine and the low-pressure turbine 104. The generator 108 connected to these turbines also rotates and generates electric power. The steam exhausted from the low-pressure turbine 104 is condensed by the condenser 106 to become water. The water accumulated at the bottom of the condenser 106 is boosted by the feed water pump 107 as feed water and supplied to the reactor pressure vessel 105 through the feed water pipe 110.

  The gas in the condenser 106 is sucked by the air extractor 115 and discharged into the off-gas system pipe 131. Cooling water in the core 134 is decomposed into hydrogen and oxygen by being irradiated with radiation (neutrons, γ rays, etc.) generated by fission. The hydrogen and oxygen accompany the steam generated in the core 134 and are discharged to the condenser 106 through the high-pressure turbine and the low-pressure turbine 104. Hydrogen and oxygen discharged to the condenser 104 are also discharged to the off-gas piping 131 by the suction action of the air extractor.

  The gas containing hydrogen and oxygen discharged from the condenser 104 flows through the off-gas system pipe 131 and reaches the dehumidifying cooler 114. The moisture contained in the gas is removed by the dehumidifying cooler 114, and the gas from which the moisture has been removed is heated to a predetermined temperature by the exhaust gas preheater 120. Since the hydrogen / oxygen bonding reaction by the catalyst in the recombiner 101 is promoted as the temperature increases, the heating of the gas in the exhaust gas preheater 120 promotes the hydrogen / oxygen bonding reaction in the recombiner 101. It will be. The gas whose temperature rises and is discharged from the exhaust gas preheater 120 is supplied to the recombiner 101. Hydrogen and oxygen contained in the gas are recombined by the action of the catalyst in the recombiner 101 to become water. For this reason, the concentration of hydrogen contained in the gas discharged from the recombiner 101 is reduced within an allowable range. The gas discharged from the recombiner 101 is cooled by a cooler (not shown) provided in the off-gas system pipe 131, and moisture contained in the gas is removed. Thereafter, the gas is supplied to an activated carbon adsorption device (not shown), and the radioactive substance contained in the gas is removed and discharged.

  Next, a hydrogen concentration prediction device 7 that predicts the hydrogen concentration in the gas discharged from the recombiner 101 of the boiling water nuclear power plant of the present embodiment (hereinafter referred to as outlet hydrogen concentration) will be described with reference to FIG. To do. The hydrogen concentration prediction device 7 is input from the input device 1 for inputting necessary data by the operator, the arithmetic device 2 for calculating the outlet hydrogen concentration or the like based on the data input from the input device 1, and the input device 1. And a display device 3 for displaying the data calculated by the calculation device 2. The input device 1 is connected to the arithmetic device 2, and the arithmetic device 2 is connected to the display device 3. More preferably, the hydrogen concentration prediction device 7 includes a data storage device 6 that stores the calculation result of the calculation device 2. The data storage device 6 is connected to the arithmetic device 2.

  The input device 1 can be configured by a general input device such as a keyboard and a mouse. The arithmetic device 2 is composed of a general information processing device (such as a personal computer). The display device 3 includes a display and a monitor that can be connected to the arithmetic device 2. The data storage device 6 is a storage device that can be connected to the arithmetic device 2 and is composed of a hard disk drive or the like. These input device 1, arithmetic device 2, display device 3, and data storage device 6 are not general-purpose products as described above, but may be designed as dedicated devices for the hydrogen concentration prediction device 7.

  When the operator inputs the exhaust gas data 4 and the catalyst state data 5 from the input device 1, the exhaust gas data 4 and the catalyst state data 5 are input to the arithmetic device 2. The exhaust gas data 4 includes data on the flow rates of hydrogen, oxygen, nitrogen and water vapor contained in the exhaust gas flowing into the recombiner 101, data on the temperature of the exhaust gas flowing into the recombiner 101, and the recombiner 101. The flow rate data of the catalyst poisoning substance (in this embodiment, organosilicon) contained in the exhaust gas flowing into the gas is included. The flow rate of hydrogen flowing into the recombiner 101 is equal to the amount of hydrogen generated by radiolysis in the nuclear reactor and is substantially proportional to the output of the nuclear reactor, and can be obtained based on the output of the nuclear reactor. For nuclear power plants that implement technology for adding hydrogen from the water supply system (hydrogen injection) for the purpose of reducing the oxygen and hydrogen peroxide concentrations in the reactor water caused by the radiolysis of water. The flow rate of hydrogen flowing into the coupler 101 is a value considering the amount of hydrogen generated by radiolysis and the amount of hydrogen added by hydrogen injection. The flow rate of oxygen flowing into the recombiner 101 includes the amount of oxygen generated by radiolysis in the nuclear reactor, the amount of oxygen contained in the air flowing into the vacuum equipment such as the turbine, and the gas waste treatment system. It can be determined from the amount of oxygen contained in the air. Since the amount of oxygen generated by this radiolysis is a value substantially proportional to the output of the reactor, it can be obtained based on the output of the reactor. The flow rate of nitrogen flowing into the recombiner 101 can be determined from the amount of nitrogen contained in the air flowing into the vacuum equipment such as the turbine and the amount of nitrogen contained in the air mixed in the gas waste treatment system. . Since the temperature of the exhaust gas flowing into the recombiner 101 is a value determined by the temperature condition set in the exhaust gas preheater 120, it is determined based on this temperature condition. The flow rate of the organosilicon contained in the exhaust gas flowing into the recombiner 101 can be determined based on the amount of the organosilicon compound contained in the sealing material used in the nuclear reactor. However, since it is difficult to grasp all the amount of the sealing material used in the nuclear reactor, in this embodiment, the exhaust gas flowing into the recombiner 101 is sampled in advance, and the organosilicon contained in the exhaust gas The flow rate of the organosilicon contained in the exhaust gas is determined by analyzing the flow rate of. As this analysis method, a gas chromatograph mass spectrometer (GC-MS) can be applied.

  The catalyst state data 5 includes data on the amount of active components contained in the catalyst charged in the recombiner 101, the activation energy of the catalyst, and the frequency factor. In this embodiment, an example in which noble metal (Pt) is used as the active component of the metal catalyst is shown. Therefore, the amount of the active component contained in the catalyst is the amount of noble metal added to the metal catalyst. Although an example in which the noble metal deposition amount is included as the amount of the active component in the catalyst state data 5 is shown, data of carbon monoxide (CO) chemisorption amount on the catalyst may be used instead of the noble metal deposition amount. . The catalyst activation energy and frequency factor data can be obtained in advance using the recombination reaction test apparatus 16 shown in FIG. 4 and the organosilicon test apparatus 17 shown in FIG. Here, a method for obtaining catalyst activation energy and frequency factor data using the recombination reaction test apparatus 16 and the organosilicon test apparatus 17 will be described.

  First, the reaction rate of a catalyst is demonstrated using the recombination reaction test apparatus 16 shown in FIG. As shown in FIG. 4, the recombination reaction test apparatus 16 includes a catalyst layer 11 in which five metal catalysts formed in a disk shape having a diameter of 25 mm and a height of 11 mm are stacked in the height direction, a reaction tube 12, A heat insulating material 13, a temperature measuring device 18, a hydrogen measuring device 19 that measures a hydrogen flow rate, and a dehumidifier 20 are provided. A catalyst layer 11 is installed inside the reaction tube 12, and a heat insulating material 13 is spread between the reaction tube 12 and the catalyst layer 11. This catalyst layer 11 is composed of the same components as the metal catalyst used in the recombiner 101. In this embodiment, an alumina carrier is attached to the surface of the sponge-like metal substrate, and noble metal is used as the active component thereon. It becomes a metal catalyst in which some platinum (Pt) is dispersed. A temperature measuring device 18, a hydrogen measuring device 19, and a dehumidifier 20 are installed on the downstream side of the catalyst layer 11. The dehumidifier 20 is installed on the upstream side of the hydrogen measuring device 19 and has a function of removing water vapor contained in the gas discharged from the catalyst layer 11.

  When a reaction gas 10 containing hydrogen, oxygen, nitrogen, and steam is introduced from the upper part of the recombination reaction test apparatus 16, the reaction gas 10 passes through the catalyst layer 11 and is discharged from the downstream side. The temperature measuring device 18 measures the temperature of the gas discharged from the catalyst layer 11. Further, the gas from which the water vapor has been removed by the dehumidifier 20 is sent to the hydrogen measuring device 19, and the hydrogen measuring device 19 detects the flow rate of hydrogen contained in the gas discharged from the catalyst layer 11 (after passing through the catalyst layer 11. The flow rate of hydrogen contained in the gas (hereinafter referred to as the outlet hydrogen flow rate) is measured. The flow rate of hydrogen flowing into the recombination reaction test apparatus 16 (hereinafter referred to as inlet hydrogen flow rate) is the flow rate of hydrogen contained in the reaction gas 10 before flowing into the catalyst layer 11. From the inlet hydrogen flow rate and the outlet hydrogen flow rate measured by the hydrogen measuring device 19, the reaction rate of the catalyst can be obtained using (Equation 2).

  Here, since the temperature of the catalyst is determined by the reaction amount of hydrogen, the flow rates of hydrogen and oxygen contained in the reaction gas 10 before flowing into the catalyst layer 11 are set to a plurality of types, and the recombination reaction test apparatus 16 The outlet hydrogen flow rate was measured using a hydrogen measuring device 19. Thus, the reaction rate of the catalyst under a plurality of temperature conditions can be obtained by performing the test under a plurality of conditions in which the flow rates of hydrogen and oxygen are changed. In this example, as shown in Table 1, a hydrogen-oxygen recombination reaction test was performed by changing the flow rates of hydrogen and oxygen contained in the reaction gas 10 to six conditions. Here, the flow rate of nitrogen contained in the reaction gas 10 and the inlet temperature and flow rate of the reaction gas 10 were set to be substantially constant under all test conditions. In this embodiment, the reaction rate of the catalyst is obtained under a plurality of types of temperature conditions by changing the flow rates of hydrogen and oxygen, but the temperature of the reaction gas 10 flowing into the recombination reaction test apparatus 16 (hereinafter referred to as inlet temperature) is determined. By changing, the reaction rate of the catalyst under a plurality of types of temperature conditions may be obtained. Furthermore, by setting the test conditions such as the concentration and flow rate of each component of hydrogen, oxygen and nitrogen contained in the reaction gas 10 so as to simulate the nuclear plan of the actual machine, the prediction accuracy of the outlet hydrogen concentration in the actual machine can be improved. Can be improved.

  Table 2 shows the results of the hydrogen-oxygen recombination reaction test conducted under the six test conditions shown in Table 1. The “experimental value” of “reaction rate” in Table 2 indicates the reaction rate obtained based on the inlet hydrogen flow rate and the outlet hydrogen flow rate obtained under the respective test conditions. The “value” indicates the outlet temperature measured by the temperature measuring device 18 under each test condition. In this way, data on the reaction rate and outlet temperature of the catalyst under a plurality of temperature conditions is acquired.

  If the reaction rate under a plurality of temperature conditions is obtained, the activation energy and frequency factor of the catalyst can be obtained from the Arrhenius equation (Equation 3). Hereinafter, a method for obtaining the activation energy and frequency factor of the catalyst will be described.

Here, E _a shown in (Expression 3) is activation energy, A is a frequency factor, R is a gas constant, T is an absolute temperature, p is a reaction order of hydrogen, and q is a reaction order of oxygen. [H ₂ ] and [O ₂ ] represent the concentrations of hydrogen and oxygen, respectively. The reaction rate can be calculated by setting the activation energy E _a of the catalyst and the frequency factor A that can reproduce experimental results well by fitting.

  The reaction order p of hydrogen and the reaction order q of oxygen are p = 1 and q = 0.5 in terms of the stoichiometry of the chemical reaction. However, by adjusting the values of the reaction order p of hydrogen and the reaction order q of oxygen from the degree of contribution of each component concentration to the reaction in the actual reaction on the catalyst, the prediction accuracy of the outlet hydrogen concentration in the actual machine is improved. Can be made. For example, the dissociative adsorption energy of oxygen atoms to platinum is greater than that of hydrogen atoms, and more oxygen atoms are adsorbed on the platinum surface. Since the contribution becomes lower, the experimental result can be reproduced more accurately by setting the value of the reaction order p of hydrogen to 1 and the value of the reaction order q of oxygen to less than 0.5.

  The method for calculating the outlet temperature is shown below. The calorific value when producing 1 mol of water vapor from 1 mol of hydrogen and 0.5 mol of oxygen is 241.8 kJ / mol. Therefore, since the reaction rate is obtained by the above-mentioned Arrhenius (Equation 3), the calorific value is obtained from the residence time in the catalyst and the reaction amount at that time, and the temperature rise is obtained by dividing by the specific heat of the gas occupying the volume. I want. By adding it to the temperature before the reaction, the temperature after the reaction is determined. When the evaluation is performed on a time scale longer than a minute unit, the time required for heat conduction can be ignored, and sufficiently accurate prediction can be performed by the above-described calculation of the equilibrium state. Further, when the influence of heat radiation cannot be ignored in a small scale system like the recombination reaction test apparatus 16 of the present embodiment, heat transfer from the catalyst to the outside air can be considered.

Using the Arrhenius equation (Equation 3), the reaction rate of the catalyst and the outlet temperature are calculated by changing the parameters of the activation energy E _a , the frequency factor A, the hydrogen reaction order p, and the oxygen reaction order q. The activation rate E _a , frequency factor A, hydrogen such that the calculated reaction rate and outlet temperature of the catalyst well reproduce the catalyst reaction rate and outlet temperature obtained in the experiment of the recombination reaction test apparatus 16. The reaction order p and oxygen reaction order q are the activation energy E _a , frequency factor A, hydrogen reaction order p and oxygen reaction order q in the metal catalyst of this example. Table 2 shows activation energy E _a = 2220, frequency factor A = 3600, hydrogen reaction order p = 1.0, oxygen reaction order q = 0.2, and heat transfer coefficient from the catalyst layer to the outside air. The reaction rate obtained when 5.8 W / m ² K is set is indicated in the “calculated value” column of “reaction rate”, and the outlet temperature is indicated in the “calculated value” column of “exit temperature”. The experimental value and the calculated value are in good agreement. That is, the activation energy of the metal catalyst used in this example is E _a = 2220, and the frequency factor is A = 3600.

  As described above, the operator acquires the exhaust gas data 4 flowing into the recombiner 101 and the catalyst state data 5 indicating the state of the catalyst filled in the recombiner 101 in advance and inputs them to the input device 1. It will be.

  Next, a method for predicting the hydrogen concentration (outlet hydrogen concentration) contained in the gas discharged from the recombiner 101 of the rising water nuclear plant using the hydrogen concentration prediction device 7 (FIG. 3) will be described. The concentration of hydrogen contained in the gas discharged from the recombiner 101 can be obtained by using the equation (equation 4) obtained by adding the term of activity decrease due to the poisonous substance to the above-mentioned Arrhenius equation (equation 3). it can.

In Equation (4), M ₀ represents an initial activity amount of the catalyst, and M represents an activity amount of the catalyst at time t. In this embodiment, the catalyst activity amount M is determined by the following method. However, the present invention is not limited to this.

C _{SIL, j} shown in (Equation 5) and (Equation 6) is the concentration of the organosilicon compound in the j-th layer of the laminated catalyst, X _SIL is the adhesion coefficient of organosilicon, n is the poisoning coefficient, and r is the recovery coefficient. To express. The number of layers j may be the same as the actual number of layers in the case of a structure in which catalysts are stacked, or may be a layer virtually divided in calculation. In addition, the adhesion coefficient X _SIL indicates the ratio of adhering organic silicon adhering to the catalyst, the poisoning coefficient n indicates the ratio of inactivation of platinum by the organic silicon adhering to the catalyst, and the recovery coefficient r is inactivated. Indicates the rate at which platinum recovers activity. These parameters can be obtained by using a laboratory-scale catalyst layer, mixing an organosilicon compound in the inflow gas, and measuring the change over time in the outlet hydrogen concentration when the catalyst performance deteriorates. More specifically, the calculation result of (Equation 4) selects the adhesion coefficient, poisoning coefficient, and recovery coefficient that can best reproduce the change over time in the outlet hydrogen concentration of the test. The poisoning coefficient and recovery coefficient can be obtained.

Below, the influence evaluation test of the organosilicon with respect to a catalyst using the organosilicon test apparatus 17 shown in FIG. 5 is demonstrated. The organosilicon test apparatus 17 has a configuration including an organosilicon injection mechanism 14 and a syringe pump 15 on the upstream side of the recombination reaction test apparatus 16 shown in FIG. As in FIG. 4, the catalyst layer 11 is a catalyst layer in which five metal catalysts formed in a disk shape with a diameter of 25 mm and a height of 11 mm are stacked in the height direction. The reaction gas 10 introduced from the upper part of the organosilicon test apparatus 17 contains hydrogen, oxygen, nitrogen and water vapor. The conditions of the reaction gas 10 are as follows: the hydrogen flow rate is 0.028 Nm ³ / h, the oxygen flow rate is 0.015 Nm ³ / h, the nitrogen flow rate is 0.011 Nm ³ / h, the water vapor flow rate is 3.9 kg / h, The test was conducted at an inlet temperature of 155 ° C. and a linear flow rate of 2.8 Nm / s. Decamethylcyclopentasiloxane (hereinafter referred to as D5) was used as the organosilicon compound. Three types of inflow rates were tested using the inflow rate of D5 as a parameter. The three inflow velocities of D5 are 6 μL / h for case 1, 1.5 μL / h for case 2, and 0.75 μL / h for case 3. D5 was diluted with hexane, and the diluted solution was injected by the syringe pump 15 at a rate of 60 μL / h. FIG. 6 shows the test results of each case and the change over time in the outlet hydrogen concentration calculated using (Equation 4) to (Equation 6). The solid line in FIG. 6 is the calculation result, and each point indicates the test result. The hydrogen concentration is expressed as a volume ratio of hydrogen to the total non-condensable gas. As parameters, activation energy E _a = 2220, frequency factor A = 3600, hydrogen reaction order p = 1.0, oxygen reaction order q = 0.2, organosilicon adhesion coefficient X _SIL = 0.95 The calculation results using the values of poisoning coefficient n = 3.7 and recovery coefficient r = 0.0007 reproduced the experimental results well. M ₀ can be set from the amount of precious metal adsorbed on the catalyst and the amount of carbon monoxide (CO) chemisorption.

The actual nuclear power plant can be predicted using the parameters set as described above. An example is shown below. In this embodiment, the dimensions of the catalyst layer of the recombiner 101 are a diameter of 800 mm and a layer height of 200 mm. The parameters are the activation energy E _a = 2220, frequency factor A = 3600, hydrogen reaction order p = 1.0, oxygen reaction order q = 0.2, organosilicon adhesion coefficient X _SIL = 0.95, The poisoning coefficient n = 3.7 and the recovery coefficient r = 0.0007 were used. As the inflow amount of organosilicon (D5), three kinds of calculations are performed, and each inflow amount is Case 1: 5 × 10 ⁻⁴ mol / min, Case 2: 3 × 10 ⁻⁴ mol / min, Case 3: 1 × 10 ^-4 mol / min. The conditions for the gas flowing into the recombiner 101 are as shown in Table 3 assuming that the plant is started. In Table 3, the inflows of hydrogen, oxygen, nitrogen, and water vapor in the elapsed time from the start of the nuclear power plant at 0-12 hours, 12-24 hours, 24-36 hours, and 36-48 hours, respectively. Indicates.

Using the above conditions, the change in outlet hydrogen concentration over time was predicted when the inflow of D5 was 5 × 10 ⁻⁴ mol / min, 3 × 10 ⁻⁴ mol / min, or 1 × 10 ⁻⁴ mol / min. .

An example of the result of the prediction calculation is shown in FIG. The horizontal axis of FIG. 7 shows the elapsed time from the start of the nuclear power plant, and the vertical axis shows the outlet hydrogen concentration. From this result, when the inflow amount of D5 exceeds 1 × 10 ⁻⁴ mol / min, it is assumed that the hydrogen concentration may increase at the time of startup. Therefore, the soundness at the time of start-up can be evaluated according to the present embodiment by previously determining the organosilicon concentration in the exhaust gas by analysis or the like and further evaluating the activity of the catalyst.

That is, as the exhaust gas data 4, the operator has a hydrogen flow rate of 0.028 Nm ³ / h, an oxygen flow rate of 0.015 Nm ³ / h, a nitrogen flow rate of 0.011 Nm ³ / h, a water vapor flow rate of 3.9 kg / h, The inlet temperature is 155 ° C., and the catalyst state data 5 includes activation energy E _a = 2220, frequency factor A = 3600, hydrogen reaction order p = 1.0, oxygen reaction order q = 0.2. 1 and the organosilicon concentrations are 5 × 10 ⁻⁴ mol / min (case 1), 3 × 10 ⁻⁴ mol / min (case 2), and 1 × 10 ⁻⁴ mol / min (case 3). Three cases are input to the input device 1. The calculation device 5 can evaluate the soundness of the catalyst performance by calculating the change over time in the outlet hydrogen concentration using these input data and displaying the calculation result (for example, FIG. 7) on the display device 3. In addition, since the display apparatus 3 has a function which can display input data, since the correctness of input data can be confirmed visually, it is preferable.

In Example 1, although the soundness of the recombiner 101 at the time of starting of a nuclear power plant was evaluated, this example shows the example which evaluated the soundness of the long-term recombination catalyst at the time of rated operation. As in Example 1, the recombiner 101 had a catalyst layer with a diameter of 800 mm and a layer height of 200 mm. The parameters are activation energy E _a = 2220, frequency factor A = 3600, hydrogen reaction order p = 1.0, oxygen reaction order q = 0.2, organosilicon adhesion coefficient X _SIL = 0.95, The poisoning coefficient n = 3.7 and the recovery coefficient r = 0. Here, since a long-term evaluation is performed, the recovery rate r is set to 0 in order to ensure maintainability. Other than that, it is the same value as Example 1. The amount of inflow of organosilicon (D5) is calculated in three ways, and each inflow amount is Case 1: 3 × 10 ⁻⁷ mol / min, Case 2: 1 × 10 ⁻⁷ mol / min, Case 3: 5 × 10 ^-8 mol / min.

  FIG. 8 shows an example of the result of predictive calculation under the above conditions. The horizontal axis represents the elapsed time from the start of the nuclear power plant, and the vertical axis represents the predicted value of the hydrogen concentration of the gas discharged from the recombiner 101. In case 1, the predicted hydrogen concentration started to increase in about 400 days and in case 2 in about 1100 days. Because it includes conservativeness, the hydrogen concentration actually rises later than expected, but based on this result, it is possible to set the inspection and replacement cycle of the catalyst.

  From the above, the display device 3 may have a function of predicting and displaying the time for reaching a predetermined outlet hydrogen concentration (for example, 4%). Further, the display device 3 has a function of displaying a prompt to replace the recombination catalyst when it is determined that the predicted time does not exceed a predetermined time (for example, the time until the next inspection). You may do it.

DESCRIPTION OF SYMBOLS 1 Input device 2 Arithmetic device 3 Display device 4 Exhaust gas data 5 Catalyst state data 6 Data storage device 10 Reaction gas 11 Catalyst layer 12 Reaction tube 13 Heat insulating material 14 Organosilicon injection mechanism 15 Syringe pump 16 Recombination reaction test device 17 Organosilicon test Apparatus 101 recombiner 115 air extractor 120 exhaust gas preheater

Claims (8)

The flow rate of exhaust gas components flowing into the exhaust gas recombiner of the gas waste treatment system of the boiling water nuclear power plant, the temperature of the exhaust gas, the index indicating the state of the catalyst filled in the exhaust gas recombiner, and An input device for inputting the inflow of poisonous substances that affect the performance of the catalyst;
An arithmetic device that calculates the hydrogen concentration at the exhaust gas recombiner outlet based on the information input from the input device;
An apparatus for predicting the outlet hydrogen concentration of an exhaust gas recombiner, comprising: a display device that displays the calculated hydrogen concentration or a temporal change in the hydrogen concentration. In the outlet hydrogen concentration prediction apparatus according to claim 1,
An exhaust gas recombiner outlet hydrogen concentration predicting device, wherein the exhaust gas constituents input to the input device include at least hydrogen, oxygen, and water vapor. In the outlet hydrogen concentration prediction apparatus according to claim 1 or 2,
The indicator indicating the state of the catalyst in the exhaust gas recombiner is at least one of the activation energy and frequency factor of the hydrogen-oxygen recombination reaction, the amount of precious metal contained in the catalyst, and the amount of carbon monoxide chemisorption of the catalyst. The exhaust hydrogen recombiner outlet hydrogen concentration prediction apparatus characterized by including one. In the outlet hydrogen concentration prediction apparatus according to any one of claims 1 to 3,
An apparatus for predicting the outlet hydrogen concentration of an exhaust gas recombiner, wherein the poisoning substance affecting the performance of the catalyst is an organosilicon compound. Hydrogen concentration that predicts the hydrogen concentration in the outlet gas discharged from the exhaust gas recombiner of the gas waste treatment system of the boiling water nuclear plant using the outlet hydrogen concentration prediction device equipped with the input device, the arithmetic device and the display device A prediction method,
The outlet hydrogen concentration prediction device
Based on the exhaust gas information flowing into the exhaust gas recombiner input from the input device and the catalyst information indicating the state of the catalyst filled in the exhaust gas recombiner, the arithmetic unit is discharged from the exhaust gas recombiner. Predict the hydrogen concentration in the outlet gas
A hydrogen concentration prediction method, comprising: displaying the predicted hydrogen concentration or a temporal change in the hydrogen concentration on the display device. In the hydrogen concentration prediction method according to claim 5,
The exhaust gas information includes information on the flow rate of hydrogen contained in the exhaust gas flowing into the exhaust gas recombiner, the flow rate of oxygen, the flow rate of water vapor, and the flow rate of poisonous substances that affect the performance of the catalyst,
The catalyst information includes activation energy and frequency factor of hydrogen-oxygen recombination reaction, information on the amount of active components of the catalyst,
The arithmetic unit predicts a hydrogen concentration in the outlet gas discharged from the exhaust gas recombiner based on the exhaust gas information and the catalyst information. In the hydrogen concentration prediction method according to claim 6,
The information on the activation component of the catalyst is either information on the amount of precious metal added to the catalyst or information on the amount of chemical adsorption of carbon monoxide contained in the catalyst. In the hydrogen concentration prediction method according to claim 6 or 7,
A method for predicting hydrogen concentration, wherein the poisoning substance affecting the performance of the catalyst is an organosilicon compound.

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