JP2011220923A - Radioactive substance monitor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radioactive substance monitor system capable of reducing a equipment cost and a maintenance cost, and capable of simplifying maintenance work.SOLUTION: A cooling device cools a sample gas which flows out from an acid gas removal device for removing an acid gas in an inspected gas to collect a radioactive iodine in the sample gas, and an iodine collecting device removes a tar like substance deposited by cooling with the cooling device and a water vapor density measurement device measures water vapor density of a gas which flows out from the iodine collecting device, and a water sample collecting device cools a gas which flows out from the water vapor density measurement device so as to get a water sample including tritium in the gas.

Description

  In the present invention, the amount of radioactivity, such as radioactive iodine, tritium, and radioactive noble gas contained in exhaust gas discharged from an incinerator facility or a melting furnace facility of solid waste in a nuclear power plant, spent fuel reprocessing facility, etc. The present invention relates to a radioactive material monitoring system for monitoring.

  In nuclear power plants and spent fuel reprocessing facilities, radioactive iodine exists in the form of simple iodine and organic iodine as gaseous radioactive waste released from the exhaust pipe at the final discharge end. In order to measure the amount of radioactivity, the gas released from the exhaust pipe is sampled to collect radioactive iodine with a scavenger, and the radioactivity amount of radioactive iodine is measured off-line with a Ge semiconductor spectrometer. As the scavenger, activated carbon impregnated with triethylenediamine, that is, impregnated carbon is generally used.

  On the other hand, according to the guideline on the measurement of the radioactive material released in the light water reactor facility for power generation, the collection efficiency of the collection agent is defined as 90% or more. By the way, since the exhaust gas exhausted from the chimney of the incinerator facility or the melting furnace facility contains a large amount of acid gas, the sampling pipe is maintained at a temperature above the acid dew point, for example, 180. The exhaust gas is maintained at a high temperature of about 0 ° C., and the exhaust gas is introduced into the iodine sampler at such a high temperature. However, the above-mentioned impregnated coal has a low trapping efficiency for simple iodine and methyl iodide under such high temperature conditions. Moreover, when acidic gas is contained in a large amount, the collection efficiency of simple iodine and methyl iodide is lowered. Moreover, the silver zeolite which can collect simple iodine and methyl iodide with high efficiency under high temperature conditions also reduces the collection efficiency due to the acid gas when the acid gas is contained in a large amount.

  Therefore, as described in Patent Document 1 described later, in order to solve the above problem, potassium zeolite having the property of selectively removing acidic gas in a high temperature environment is disposed in the front stage of the silver zeolite, so that it is high temperature and acidic. A radioactive iodine sampler configured to collect simple iodine and methyl iodide with a collection efficiency of 90% or more even in a sample gas containing a large amount of gas has been put to practical use. The sample gas maintained at 180 ° C. was passed through a silver zeolite cartridge to collect simple iodine and methyl iodide, and the Ge semiconductor spectrum was measured for both potassium zeolite cartridge and silver zeolite cartridge. Radioactive iodine is measured offline with a meter.

Further, in Patent Document 2 to be described later, in order to solve the above problem, tritium (tritium T) as gaseous radiation waste is present in the form of HTO or T ₂ O in the exhaust exhausted from the chimney. In order to measure the radioactive temperature of tritium, a sample gas is sampled, a tritium sample is collected, and is measured off-line with a liquid scintillation counter. When collecting a tritium sample, a cooling condensation method is employed in which sample gas is cooled to collect sample water containing tritium.

  According to the “Guidelines for Measurement of Radioactive Material Released in Light Water Reactor Facilities for Power Generation” established by the Atomic Energy Commission of Japan, a part of water vapor in the sample gas is collected for the cooling condensation method described above. When sample water is used, it is necessary to measure the average water vapor density in the sample gas during the sampling period.

  The average water vapor density in the sample gas is obtained by measuring the temperature / humidity or dew point in Patent Document 2 to be described later, and comparing the temperature / humidity or dew point with the water vapor density using a controller. When sampling exhaust gas from an incinerator or melting furnace that contains acid gas, the humidity sensor or dew point sensor is corroded by acid gas, so the humidity sensor or dew point sensor is frequently calibrated during the operation period. Since it is necessary to replace the detached humidity sensor or dew point sensor, a temperature sensor, humidity sensor or dew point sensor, flow meter, etc. are installed downstream of the sample water collector, and acid gas is removed from the sample water collector. Samples collected from the sample water collection device were collected together with the sample water as acid, acid gas was removed, temperature / humidity or dew point and flow rate were measured Measure the mass of water, determine the average water vapor density corresponding to the collected water based on the above mass and integrated flow rate, and determine the average residual water vapor density of the sample gas discharged from the sample water collector based on the temperature / humidity or dew point. By adding the two together to obtain the average water vapor density in the sample gas and installing a hygrometer or dew point meter in a suitable environment, humidity sensor or dew point sensor calibration during operation, humidity sensor or dew point sensor The frequency of calibration is reduced to the frequency of periodic inspection of the equipment.

  Further, in Patent Document 3 described later, a radioactive gas monitor that samples a sample gas from the chimney and measures a radioactive noble gas measures the sample gas at an ambient temperature lower limit in order to protect devices such as a radiation detector and a pump from acidic gas. After cooling to remove acid gas as acid drain, the radioactivity concentration of the rare gas in the sample gas is measured.

JP 63-256898 A JP 2007-24768 JP-A-6-242291

  However, since the above-described conventional radioactive iodine sampler is configured as described above, it is necessary to use an expensive collector with high-temperature specifications in order to collect radioactive simple iodine and organic iodine at high temperatures. However, there was a problem that the material cost for exchanging the collecting agent every week specified in the above guidelines was expensive. In addition, by reducing the temperature when measuring the flow rate with a flow meter, tar-like substances contained in the sample gas precipitate and adhere inside the flow meter. The flow meter must be replaced periodically, and the pump replacement cycle is shortened due to corrosion, resulting in an increase in maintenance material costs.

  In addition, when the sample gas is cooled by the sample water collector, the conventional tritium sampler adheres to the inner surface of a cooling fin or a thin tube that cools the sample gas when the tar-like substance contained in the sample gas comes into contact with the refrigerant. As the capacity decreases and the sample gas passage is blocked, it is necessary to clean the sample water collection device to remove tar-like substances during periodic inspections. A process of immersing and dissolving cooling fins, capillaries, etc. with substances and a high-pressure flushing process are required, which requires a lot of maintenance time and a long cleaning period, and is incinerated and melted during regular inspections. Since the amount of treated substances increases, if the cleaning period becomes longer, waste treatment is stagnated, so that reduction of the maintenance time and shortening of the maintenance period have been problems.

  Furthermore, in order to protect the radiation detector from acid gas and tar-like substance, the conventional radioactive noble gas monitor cools the sample gas below the ambient temperature and removes the acid gas as acid drain. As a result, the reduction of maintenance work has been a problem. Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radioactive substance monitoring system capable of reducing equipment costs and maintenance costs and simplifying maintenance work.

  The radioactive substance monitoring system of the present invention has been developed to solve the above-described problems, and is an acid gas removing device that removes acid gas in a gas to be inspected, and the object to be inspected from which acid gas has been removed. A cooling device for cooling the gas, an iodine collecting device for collecting the radioactive iodine contained in the cooled gas to be inspected and removing a tar-like substance deposited by the cooling, and the tar-like substance has been removed. A water vapor density measuring device for measuring the water vapor density of the gas to be inspected, and a sample water collecting device for cooling the gas to be inspected after measuring the water vapor density to obtain sample water containing tritium contained in the gas to be inspected It is characterized by comprising.

  Another radioactive substance monitoring system of the present invention includes an acidic gas removing device that removes an acidic gas in a gas to be inspected, a cooling device that cools the inspected gas from which the acidic gas has been removed, and the cooled inspected gas An iodine collector that collects radioactive iodine contained in the catalyst and removes tar-like substances deposited by the cooling, and the gas to be inspected is cooled after the measurement of the water vapor density and is contained in the gas to be inspected. A sample water collecting device for obtaining sample water containing tritium and a water vapor density measuring device for measuring the water vapor density of the gas to be inspected from which the tar-like substance has been removed.

  Since the radioactive substance monitoring system of the present invention has the above-described configuration, the acidic gas in the sample gas is removed by the acidic gas removing device, and the radioactive iodine in the sample gas is captured by the iodine collecting device. Further, by cooling the sample gas with the cooling device so that the temperature of the sample gas is not less than the water dew point and not more than a predetermined humidity, a general collecting agent can be used in the iodine collecting device. Thus, the material cost for exchanging the collecting agent can be reduced.

  Moreover, by cooling the sample gas with the cooling device, the tar-like substance contained in the sample gas is precipitated, and the tar-like substance is removed by adhering to the collecting agent in the iodine collecting device. Since the water vapor density can be measured under suitable conditions that do not adhere and cause no corrosion, the replacement frequency of the water vapor density measurement sensor becomes longer, and tar-like substances deposit and adhere inside the sample water collecting device. Therefore, the inside of the sample water collecting device can be easily cleaned, and the maintenance cost can be reduced. In addition, by connecting an iodine sampler, a tritium sampler, and a radioactive noble gas monitor in this order, and sharing the measuring instrument sensor and pump of the sampling unit, the equipment cost and the maintenance cost can be greatly reduced.

1 is a diagram showing a configuration of an entire radioactive substance monitoring system according to Embodiment 1 of the present invention. FIG. 2 is a detailed configuration diagram of a heating device according to Embodiment 1. FIG. 3 is a detailed configuration diagram of a cooling device according to Embodiment 1. FIG. 1 is a configuration diagram of a water vapor density measuring apparatus according to Embodiment 1. FIG. 1 is a configuration diagram of a sample water collecting device according to Embodiment 1. FIG. 2 is a configuration diagram of an acidic gas removal filter unit according to Embodiment 1. FIG. 3 is a configuration diagram of an iodine collection filter unit according to Embodiment 1. FIG. It is a figure which shows the structure of the whole monitoring system of the radioactive substance concerning Embodiment 2 of this invention. It is a block diagram of the part in the monitoring system of the radioactive substance concerning Embodiment 3 of this invention.

Embodiment 1 FIG.
Hereinafter, the first embodiment of the present invention will be described in detail with reference to FIGS. In FIG. 1, the radioactive substance monitoring system according to the first embodiment includes, in order, a sampling pipe 1, a heating device 2, an acid gas removal filter unit 3, a cooler 4, an iodine collection filter unit 5, and a water vapor density measuring device. 6, a compressor 7, a sample water collecting device 8, a first pressure gauge 9, a pressure regulating valve 10, a flow meter 11, a second pressure gauge 12, and a radioactive noble gas monitor 13.

  Moreover, the said heating apparatus 2 is comprised from the heater 21, the temperature sensor 22, and the controller 23, as shown in FIG. As shown in FIG. 3, the cooler 4 includes a fin body pipe 41, a fan 42, and a controller 43. As shown in FIG. 4, the water vapor density measuring device 6 includes a temperature sensor 61, a humidity sensor 62, a pressure sensor 63, and a calculation display unit 64. As shown in FIG. 5, the sample water collecting device 8 automatically drains the collected sample water, the sample water collecting unit 81, the cooling water supply unit 82 that circulates and supplies the cooling water to the sample water collecting unit 81, and the sample water. An auto drain 83 and a sample water container 84 for storing the discharged sample water are configured, and the sample water collecting unit 81 has a plurality of thin tubes 811 inside as shown in the figure. The narrow tube 811 is formed of a chemically stable resin, for example, a fluorine resin such as Teflon (registered trademark), a polyolefin resin such as polyethylene, or a metal material whose surface is coated with such a chemically stable resin. Yes.

  As shown in FIG. 6, the acid gas removing device 3 includes a dust filter 31 that collects particulate radioactive substances, and then an acid gas removal filter cartridge 32 that is filled with potassium zeolite 321 that removes acid gas, An acid gas removal filter case 33 in which the dust filter 31 and the acid gas removal filter cartridge 32 are mounted, and a thermostatic chamber 34 that contains the acid gas removal filter case 33 and maintains the temperature of the sample gas so as not to be lower than the acid dew point; The acidic gas removal filter case 33 is composed of an inlet valve 35 and an outlet valve 36 provided at the inlet and outlet, respectively. Potassium zeolite 321 is an adsorbent in which potash is supported on zeolite, and particularly effectively acts on acidic gas to remove efficiently. The acid gas removal filter cartridge 32 may be loaded by various methods according to the concentration of the acid gas, for example, by stacking a plurality of the cartridges. As shown in FIG. 7, the iodine collecting filter unit 5 includes an adhering charcoal filter case 52 in which adhering charcoal cartridges 51 filled with adhering charcoal 511 that collects radioactive iodine are stacked and loaded, and an adsorbing charcoal filter case 52. Consists of an inlet valve 53 and an outlet valve 54 respectively provided at the inlet and outlet

Next, the function of the apparatus of the first embodiment will be described in detail. The heating apparatus 2 maintains a predetermined temperature equal to or higher than the acid dew point, and a sample gas (not shown) is removed from the sampling pipe 1 by an acid gas removal filter. The acid gas is removed and introduced into the cooler 4 while being introduced into the unit 3 and maintained so that the temperature of the sample gas does not fall below the acid dew point. The cooler 4 passes the sample gas through the finned pipe 41 to cool by air cooling, and blows air from the fan 42 to the fin of the finned pipe 41, and the controller 43 does not fall below the water dew point based on the humidity of a hygrometer described later. And control the fan speed so that the humidity does not exceed the specified humidity or turn on the fan power
N / OFF control. The sample gas discharged from the cooler 4 is introduced into the iodine collection filter unit 5 to collect radioactive simple substance iodine and organic iodine contained in the sample gas and to remove tar-like substances deposited by cooling. Is done.

  The sample gas discharged from the iodine collection filter unit 5 is introduced into the water vapor density measuring device 6, the temperature is measured by the temperature sensor 61 shown in FIG. 4, the humidity is measured by the humidity sensor 62, and the pressure is measured by the pressure sensor 63. Are measured, the respective measurement results are input, and the average water vapor density from the start of sampling is calculated and displayed on the calculation display unit 64. The humidity sensor 62 may be replaced with a dew point sensor that measures the dew point.

  The compressor 7 sucks and pressurizes the sample gas discharged from the water vapor density measuring device 6. The pressure of the sample gas discharged from the sample water collecting device 8 is measured by the first pressure gauge 9, the pressure is adjusted by the pressure adjusting valve 10, and the pressure is reduced and discharged. With respect to the sample gas discharged from the pressure regulating valve 10, the flow rate is measured by the flow meter 11, the pressure is measured by the second pressure gauge 12, the rare gas is measured by the radioactive rare gas monitor 13, and is exhausted from the sampling pipe 14. The

  As shown in FIG. 6, the acid gas removal filter unit 3 includes a dust filter 31 that collects particulate radioactive substances, and an acid gas removal filter cartridge 32 that is subsequently filled with potassium zeolite 321 that removes acid gas. An acid gas removal filter case 33 in which the dust filter 31 and the acid gas removal filter cartridge 32 are mounted, and a thermostatic chamber 34 that contains the acid gas removal filter case 33 and maintains the temperature of the sample gas so as not to be lower than the acid dew point; The acidic gas removal filter case 33 is composed of an inlet valve 35 and an outlet valve 36 provided at the inlet and outlet, respectively. The above-mentioned potash zeolite 321 is an adsorbent in which potash is supported on zeolite, and particularly effectively acts on acidic gas to remove efficiently. A plurality of acid gas removal filter cartridges 32 may be stacked and loaded according to the concentration of the acid gas.

As shown in FIG. 7, the iodine collecting filter unit 5 includes an adhering charcoal filter case 52 in which a plurality of adhering charcoal cartridges 51 filled with adhering charcoal 511 that collects radioactive iodine are stacked and stored, and an adsorbing charcoal filter case. It is comprised from the inlet valve 53 and the outlet valve 54 which were each provided in the inlet and outlet of 52. The collected radioactive radioactive material and radioactive iodine are measured off-line by a Ge semiconductor spectrometer. The impregnated carbon 511 is obtained by adding an additive to activated carbon. Examples of the additive include triethylenediamine (TEDA), tin iodide (SnI ₂ ), and the additive includes simple iodine and organic iodine collected on the activated carbon. Is fixed in activated carbon to prevent detachment and to be collected with high efficiency. The impregnated charcoal cartridge 51 filled with activated carbon is commercially available, and is easily available and inexpensive.

  Next, the effect of Embodiment 1 is demonstrated. When the acid dew point of the sample gas at the source point (not shown) is 150 ° C., for example, the sample gas is maintained at a temperature higher than the dew point, for example, 180 ° C. by the heating device 2 installed in the sampling pipe 1 to remove acid gas. It is introduced into the filter unit 3. In the acid gas removal filter unit 3, the acid gas removal filter case 33 is kept in a constant temperature bath 34, and the sample gas temperature is maintained at an acid dew point of 150 ° C. or higher even at the lower specification ambient temperature. Acid gas in the sample gas is removed with the filled potassium zeolite 321.

  The cooler 4 cools to 40 ° C. + T 1 when the water dew point of the sample gas at the source point is 40 ° C., for example. The iodine collection filter unit 5 introduces the sample gas discharged from the cooler 4, and captures radioactive simple iodine and organic iodine contained in the sample gas by the adsorbed charcoal 511 filled in the adsorbed charcoal cartridge 51. While collecting, tar-like substances contained in the sample gas are removed. The sample gas discharged from the iodine collection filter unit 5 is cooled to a temperature of 40 ° C. + T1 in the cooler 4 in consideration of the natural heat radiation because the temperature is slightly reduced by natural heat radiation and introduced into the water vapor density measuring device 6. To do. T1 is set such that the humidity of the sample gas is 70% or less, which is a suitable humidity condition for capturing the radioactive simple iodine and organic iodine at 90% or more with the impregnated coal 521. It is set so that it is below the specified upper limit temperature and above the water dew point. For example, by setting T1 to 10 ° C., the temperature of the sample gas becomes 50 ° C. As a result, the humidity of the sample gas becomes about 60% RH, and can be kept below the specification upper limit temperature of 60 ° C. of the flow meter.

  The sample gas discharged from the iodine collection filter unit 5 can maintain a water dew point of 40 ° C. or higher even if the temperature slightly decreases due to natural heat dissipation. When the sample gas discharged from the water vapor density measuring device 6 is pressurized by the compressor 7 to 3 atm, for example, the water vapor density is tripled, and the pressurized sample gas is obtained by the sample water collecting device 8, for example. When cooled to 2 ° C, the water dew point converted back to atmospheric pressure is reduced to 0 ° C, allowing sample water to be collected even in the winter when the water dew point is low, and the downstream flow meter 11. The second pressure gauge 12 and the radioactive noble gas monitor 13 can be operated under suitable low humidity conditions.

  Therefore, as described above, when the iodine sampler, tritium sampler, and radioactive noble gas monitor are installed separately, the sampling function and the pretreatment function for protecting the equipment from corrosion and tar-like substances can be shared. It is possible to provide a radioactive iodine tritium sampler / radioactive substance monitoring system with significantly reduced equipment costs compared to installing each function.

  Further, the acid gas removal filter unit 3 removes the acid gas in the sample gas with the potassium zeolite 321 filled in the acid gas removal filter cartridge 32 while maintaining the temperature of the sample gas at the acid dew point or higher, and the iodine collection filter unit. 5 so as to prevent suffocation of the coking coal 521 filled in the coking coal cartridge 51 of the No. 5 with the acidic gas, the temperature of the sample gas is set to the water dew point or higher and the humidity 70% RH or lower by the cooler 4, By preparing suitable conditions for collecting radioactive elemental iodine and organic iodine, it becomes possible to use an inexpensive commercially available adhering charcoal cartridge 51, which greatly increases the material cost for replacing the adsorbing charcoal cartridge 51. Can be reduced.

  Further, by removing the tar-like substance with the adsorbed carbon 511 filled in the adsorbed carbon cartridge 51 of the iodine collecting filter unit 5, the humidity sensor 62 of the water vapor density measuring device 6, for example, a fluororesin of the sample water collecting device 8 is used. An increase in maintenance frequency and replacement frequency due to the tar-like substance adhering to the thin tube 811 can be prevented, and the maintenance cost can be reduced. In addition, with regard to the periodic sampling of particulate radionuclides required by the guidelines on the measurement of released radioactive materials at light water reactor facilities for power generation, and removal of particulate matter as a pretreatment for measurement of radioactive noble gases, Since the acid gas removal filter unit 3 has both functions, the maintenance cost related to the dust filter can be greatly reduced as compared with the case where the iodine sampler and the radioactive rare gas monitor are installed alone.

Embodiment 2
The second embodiment of the present invention will be described in detail with reference to FIG. In the first embodiment, the water vapor density measuring device 6 is installed between the iodine collecting filter unit 5 and the sample water collecting device 8 as shown in FIG. On the other hand, in the second embodiment, the measurement device 6 is installed downstream of the sample water collecting device 8 and accumulated in the sample water container 84 of the sample water collecting device 8 as shown in FIG. The sum of the average water vapor density obtained by dividing the sample water by the sampling period integrated flow rate and the average water vapor density obtained by the water vapor density measuring device 6 in FIG. In addition, the average water vapor density at the source point can be accurately measured, and the residual acid gas is removed by the sample water collecting device 8 so that the acid gas in the sample gas is lowered to the normal atmospheric concentration level. The effect which can operate 61 in a more suitable environment is produced.

Embodiment 3
The third embodiment of the present invention will be described in detail with reference to FIG. In Embodiment 3, as shown in FIG. 9, the acid gas removal filter unit 3 in Embodiments 1 and 2 includes two systems 3a and 3b in parallel, and inlet valves 35a and 35b of the respective systems are provided. In addition, the dust filter 31 and the acid gas removal filter cartridge 32 can be exchanged without stopping the compressor 7 by sequentially switching the outlet valves 36a and 36b to one system, two systems, and one system, and the iodine collection filter unit. 5 also includes two systems 5a and 5b in parallel, and the compressor 7 is stopped by sequentially switching the inlet valves 53a and 53b and the outlet valves 54a and 54b of the respective systems to one system, both systems, and one system. Therefore, it is possible to replace the impregnated charcoal cartridge 51 without the need for maintenance. It can provide sexual noble gas monitoring system.

  The present invention monitors the radioactivity of radioactive iodine, tritium, and radioactive noble gases contained in exhaust gas discharged from solid waste incinerator facilities or melting furnace facilities at nuclear power plants, spent fuel reprocessing facilities, etc. It is highly possible to use as a monitor system.

1: sampling piping, 2: heating device, 3: acid gas removal filter unit,
4: cooler, 5: iodine collection filter unit, 6: water vapor density measuring device,
7: Compressor, 8: Sample water collecting device, 9: First pressure gauge, 10: Pressure regulating valve,
11: Flow meter, 12: Second pressure gauge, 13: Radioactive noble gas monitor

Claims (6)

An acid gas removing device for removing acid gas in the gas to be inspected, a cooling device for cooling the gas to be inspected from which acid gas has been removed, and collecting radioactive iodine contained in the cooled gas to be inspected The iodine collection device for removing the tar-like substance deposited by cooling, the first water vapor density measuring device for measuring the water vapor density of the inspection gas from which the tar-like substance has been removed, and the inspection after the water vapor density is measured A radioactive substance monitoring system comprising a first sample water collecting device for cooling a gas to obtain sample water containing tritium contained in the gas to be inspected. An acid gas removing device for removing acid gas in the gas to be inspected, a cooling device for cooling the gas to be inspected from which acid gas has been removed, and collecting radioactive iodine contained in the cooled gas to be inspected Iodine collector for removing tar-like substances deposited by cooling, sample water collection for obtaining sample water containing tritium contained in the test gas by cooling the test gas after measuring the water vapor density A radioactive substance monitoring system comprising: an apparatus; and a second water vapor density measuring apparatus for measuring a water vapor density of the inspection gas from which tar-like substances have been removed.   The acidic gas removing device includes an acidic gas removing filter cartridge filled with potassium zeolite for removing acidic gas, an acidic gas removing filter case to which the acidic gas removing filter cartridge is attached, and the acidic gas removing filter case. The radioactive substance monitoring system according to claim 1, further comprising a thermostatic chamber that maintains the temperature of the sample gas so as not to be lower than the acid dew point.   4. The iodine collecting apparatus according to claim 1, further comprising: an adhering charcoal cartridge having an adhering charcoal for collecting radioactive iodine; and an adhering charcoal filter case for mounting the adhering charcoal cartridge. The radioactive substance monitoring system according to claim 1. The acid gas removing device includes a dust filter that collects particulate radioactive substances, and the sample gas passes through the acid gas removing filter cartridge via the dust filter. The radioactive substance monitoring system according to claim 3 or 4.   The radioactive substance monitoring system according to any one of claims 1 to 5, wherein the acid gas removing device and the iodine collecting device are respectively provided in parallel in two systems.

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