JPH07148418A - Method for testing leakage in iodine filter and apparatus for the same - Google Patents

Abstract

PURPOSE:To detect simply without environmental pollution the leakage in an iodine filter for removing radioactive iodine from offgas from radioactive substance treating facilities. CONSTITUTION:An air introduction apparatus which can change humidity is placed upstream from an iodine filter to be tested; a humidity meter is located downstream from the filter. Dry air from the air introduction apparatus is fed into the iodine filter to remove water from an iodine adsorbent in the filter. Then, air with elevated humidity is fed into the filter. The humidity of air passed through the filter is measured by the humidity meter. The leakage of the iodine filter is judged from the difference in time between the start of humid air supply to the filter and the detection of high humidity by the humidity meter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak test method for an iodine filter and a test apparatus therefor, and particularly to off gas (exhaust gas) generated from a nuclear power plant, a reprocessing plant, a facility for handling radioactive isotopes, and other nuclear facilities. ) Related to a leak test method and a test apparatus for an iodine filter used in an offgas treatment facility for separating and removing radioactive iodine contained in

[0002]

2. Description of the Related Art As a conventional leak test method for iodine filters, a method using freon has been generally known. Further, Japanese Patent Publication No. 4-75455 (Japanese Patent Laid-Open No. 58-1725).
As described in Japanese Patent Laid-Open No. 48), a method of introducing heavy water vapor into an iodine filter to detect a leak has been known.

[0003]

The conventional leak test method for iodine filters has excellent performance as a leak test technique, but uses a substance that does not exist in the natural world, and thus is suitable for environmental protection and handling. I had to be careful.

An object of the present invention is to provide a leak test method for an iodine filter which can easily detect a leak using a substance existing in nature.

[0005]

Means for Solving the Problems A feature of the present invention that achieves the above object is to provide a leak test method for an iodine filter, which removes radioactive iodine contained in exhaust gas discharged from a nuclear facility with an iodine adsorbent, in an air condition. Aerated air having a changed composition of the gas component contained in the iodine filter, a time delay of the composition change of the air at the outlet side of the iodine filter with respect to the composition change of the air at the inlet side of the iodine filter To detect.

[0006]

By using a substance contained in the atmosphere as an indicator for leak detection, it is not necessary to pay attention to environmental protection and handling is relatively easy. The substance used in the test and the substance present in the atmosphere can be easily discriminated by significantly changing the concentration of the substance used in the test and introducing the substance into the iodine filter.

Whether or not there is a leak in the iodine filter can be determined by grasping the time delay of the change in the outlet concentration of the substance in the ventilation gas with respect to the change in the inlet concentration of the iodine filter.

The gas component contained in the atmosphere causes a reversible adsorption / desorption reaction with the iodine adsorbent in the iodine filter. Leakage of the iodine filter means that the ventilation gas passes without passing through the iodine adsorbent layer, and iodine in the ventilation gas is not normally removed by the iodine adsorption material. Therefore, if a gas component contained in the atmosphere also leaks to the iodine filter, it will pass through the filter without causing an adsorption / desorption reaction with the iodine adsorbent, so the filter will be faster than if there is no leakage. Get out of. That is, the presence or absence of leak can be determined from the time delay of the gas component. The passage time delay of the gas component of the iodine filter normally filled with the iodine adsorbent depends on the type of gas component,
It depends on the concentration (flow rate) and the amount of iodine adsorbent (layer thickness).
By preliminarily evaluating the time delay of passage of the gas component in the normal case by the basic test, the difference from the case with the leak can be clarified.

The gas components existing in the atmosphere are adsorbed in the iodine adsorbent to some extent in equilibrium with the atmosphere. In this case, if the component adsorbed on the iodine adsorbent in the filter is removed in advance, the difference in time delay can be easily discriminated. Further, even if a gas containing the component at a concentration higher than the equilibrium adsorption concentration is passed, the discrimination becomes easy.

Further, even a component which does not exist in the atmosphere can be used for the leak test method of the iodine filter as long as it is a component which is adsorbed to and desorbed from the iodine adsorbent.

The gas generator plays a role of flowing the gas whose component concentration is changed through the iodine filter, and the device capable of measuring the component concentration in the gas plays a role of detecting the component concentration and its time change (time delay with respect to the inlet side). Fulfill.

[0012]

EXAMPLES Examples of the present invention will be described below.

Example 1 As a first example of the present invention, the case where the atmospheric gas component contained in air is water (water vapor) will be described with reference to FIG. FIG. 1 shows the basic configuration of the leak test apparatus in this embodiment.

An air introducing device capable of changing the humidity is installed upstream of the iodine filter to be tested, and a humidity measuring device is installed downstream of the iodine filter. The gas flow from the air introducing device to the humidity measuring device through the iodine filter is closed, and there is no outflow of gas to the outside or inflow of gas from the outside. Since it is often the case that a plurality of iodine filters are tested in terms of equipment, it is convenient to be able to replace the iodine filters.

First, dry air with reduced humidity is passed through the iodine filter from the air introducing device to remove water from the iodine adsorbent in the iodine filter (dry the iodine adsorbent). In this case, the humidity is preferably close to 0%, but if it is 30% or less, there is no particular problem. While supplying dry air to the iodine filter, measure the humidity in the air flowing out of the iodine filter with a humidity measuring device on the downstream side, and dry air until the humidity becomes the same as the humidity in the air supplied to the iodine filter. Keep flowing.

After the humidity in the air on the downstream side from the outlet of the iodine filter stabilizes at a low value, the air having the next increased humidity is supplied into the iodine filter. The humidity of the air supplied into the iodine filter may be equal to or higher than the humidity of the initially supplied air, but is preferably 2 or more than the initial humidity in the air.
The higher the value is 0% or more, the easier the detection. Understand the time when the high humidity air is supplied to the iodine filter. On the downstream side of the iodine filter, the humidity in the air that has passed through the iodine filter is continuously measured by the humidity measuring device to grasp the time when high humidity is detected. The humidity in the air that has passed through the iodine filter is measured by the humidity measuring device and the time when the iodine filter is supplied, and the presence or absence of leakage of the iodine filter is determined from the difference between the time when high humidity is detected.

A typical example of the humidity measurement result and the procedure for determining the presence / absence of leakage of the iodine filter will be described with reference to FIG. In FIG. 2, (a) is a humidity change in the air flowing into the iodine filter, (b) is an ideal humidity change in the air flowing out from the iodine filter, and (c) is an actual humidity change in the air flowing out from the iodine filter. 2 schematically shows the change in humidity. The humidity change in the air flowing into the iodine filter is adjusted by an air introducing device and the change is grasped, and the humidity is raised at a certain time. Humidity change in the air flowing out from the iodine filter is detected by a humidity measuring device, and at what time the humidity changes from when the humidity in the air flowing into the iodine filter is changed. If this time is earlier than the time measured by the normal iodine filter in advance, there will be a leak in the tested iodine filter. The change in humidity in the air flowing out from the iodine filter is ideally as shown in (b), but in reality it is S-shaped as shown in (c) due to the interaction with the iodine adsorbent in the iodine filter. A gentle humidity change in the mold is measured. In particular, when it is normal, it becomes gentle, and when the degree of leakage of the iodine filter is severe, it changes rapidly. The lighter the leak is, the more the interaction between the water vapor and the iodine adsorbent increases, the more gradual the humidity change becomes, and the time lag shifts to the rear side, approaching the normal case. In any case, the presence or absence of a leak in the iodine filter can be determined by comparing the humidity change position in the normal case.

Since the iodine adsorbent after the leak test is in a state of adsorbing water vapor, it is preferable to remove the water vapor from the iodine adsorbent by flowing dry air again.

The iodine filter that was normal in this leak test can be used as it is in a nuclear facility. Further, in the iodine filter in which the leak is found, the leak part is eliminated by vibration or the like, or a new iodine adsorbent is refilled in the iodine filter. In this case, the presence / absence of a leak is determined again by this leak test method.

As described above, according to the present embodiment, since the air whose humidity has been changed is supplied to the iodine filter and only the time delay of the humidity change is measured, the presence / absence of leakage of the iodine filter can be determined very easily. . Further, the water vapor contained in the air flowing into the iodine filter is a substance existing in nature, and it is not necessary to pay attention to environmental protection and handling.

In the above embodiment, the type of iodine adsorbent was not specified, but any iodine adsorbent such as activated carbon, silver impregnated activated carbon, silver zeolite, silver mordenite, silver silica gel, silver alumina, etc. will leak. The presence or absence of can be determined.

In this embodiment, water (water vapor) is selected as the leak detecting gas component, but the same effect can be obtained by selecting a gas component other than water vapor contained in the atmosphere. However, in this case, it is necessary to install a device capable of measuring the component instead of the humidity measuring device. The test procedure was to remove the component from the iodine adsorbent, to ventilate the gas with an increased component concentration, to detect the time delay between the inlet side and the inlet side of the component concentration change,
The judgment is whether there is a leak or not, and the components are removed again from the iodine adsorbent, which is exactly the same as above.

Example 2 A leak test apparatus for an iodine filter, which is a second example of the present invention, will be described with reference to FIG. In the present embodiment, the air containing the carbon dioxide having a certain constant concentration is supplied to the iodine filter, and the air having the carbon dioxide concentration changed to another value is allowed to flow into the iodine filter. The time delay until the concentration of carbon dioxide after the concentration change in the air passing through the iodine filter is detected by the carbon dioxide concentration measuring device after the start of supplying the air containing it to the iodine filter is automatically detected, and iodine is detected. This is a method for determining the leak of the filter.

An air introducing device capable of changing the carbon dioxide (CO ₂ ) concentration is installed on the upstream side, and a carbon dioxide concentration measuring device is installed on the downstream side with the iodine filter to be tested interposed therebetween. Also, a time delay determination device for measuring the time delay of the change in carbon dioxide concentration is installed. The gas flow from the air introduction device to the carbon dioxide concentration measurement device through the iodine filter is closed, and there is no outflow of gas to the outside or inflow of gas from the outside. The time delay determination device receives information about the time when the carbon dioxide concentration changes from the air introducing device and the carbon dioxide measuring device, and automatically calculates the time delay of the carbon dioxide concentration change.

First, air containing a certain concentration of carbon dioxide is supplied from the air introducing device into the iodine filter until equilibrium is reached. Next, the air whose carbon dioxide concentration has been changed is supplied into the iodine filter. The carbon dioxide concentration in this case may be different from the concentration in the air initially supplied to the iodine filter, but it is desirable that the carbon dioxide concentration is 10% or more higher or lower than the initial carbon dioxide concentration to facilitate detection. The time at which the air having the changed carbon dioxide concentration starts to flow is transmitted from the air introduction device to the time delay determination device as information. On the downstream side, the carbon dioxide concentration in the passing air is measured by the carbon dioxide concentration measuring device, and the time when the concentration change corresponding to the inlet side change is detected is transmitted to the time delay determining device as information. When the carbon dioxide concentration in the air that has passed through the iodine filter was measured with the carbon dioxide concentration measuring device at the time when the carbon dioxide with changed concentration was started to be supplied to the iodine filter, and when the change in the carbon dioxide concentration was detected, Whether there is a leak in the iodine filter is determined from the time difference.

The procedure for determining the presence / absence of a leak in the iodine filter is the same as in the case of Example 1, and when a change in concentration is detected earlier than the time previously measured by the normal iodine filter, the iodine filter tested is used. There will be a leak. If the time delay determination device is given in advance information on the time delay in the normal case, the presence or absence of a leak in the iodine filter will be automatically determined.

In this case, the carbon dioxide concentration may be changed from a low value to a high value or conversely from a high value to a low value. In the former case, the iodine adsorbent after the leak test is carbon dioxide. Is adsorbed, it is preferable to remove the carbon dioxide from the iodine adsorbent by flowing air having a low carbon dioxide concentration.

The iodine filter that was normal in this leak test can be used as it is in a nuclear facility. Further, in the iodine filter in which the leak is found, the leak part is eliminated by vibration or the like, or the iodine adsorbent is refilled. In this case, the presence / absence of a leak is determined again by this leak test method.

As described above, according to the present embodiment, the same effect as that of the first embodiment can be obtained because only the air having the changed carbon dioxide concentration is flowed and the time delay of the concentration change is measured.

In the above embodiment, the type of iodine adsorbent was not specified, but any iodine adsorbent such as activated carbon, silver-impregnated activated carbon, silver zeolite, silver mordenite, silver silica gel, silver alumina, etc. will leak. The presence or absence of can be determined.

In this embodiment, carbon dioxide was selected as the leak detecting gas component, but the same effect can be obtained by selecting a gas component other than carbon dioxide contained in the atmosphere. However,
In this case, it is necessary to install a device capable of measuring the component instead of the carbon dioxide concentration measuring device. The procedure of the test is to ventilate a gas containing a certain concentration of component, to ventilate a gas whose component concentration has been changed, to detect the time delay between the inlet side and the outlet side of the component concentration change, and to determine the presence or absence of leakage. Is the same.

Example 3 A leak test apparatus for an iodine filter, which is a third example of the present invention, will be described with reference to FIG. In this embodiment, air containing a higher concentration of argon than the argon adsorbed on the iodine adsorbent in the iodine filter is caused to flow, and the time delay at which the high concentration of argon is detected downstream from the iodine filter outlet is automatically adjusted. This is a method of detecting and determining a leak.

An air introducing device capable of introducing air containing a high concentration of argon into the iodine filter is provided upstream of the iodine filter to be tested, and an argon concentration measuring device is provided downstream of the iodine filter. In addition, information on the time when the high-concentration argon-containing air is introduced from the air introducing device to the argon concentration measuring device should be sent. The gas flow from the air introducing device to the argon concentration measuring device through the iodine filter is closed, and there is no outflow of gas to the outside or inflow of gas from the outside. Since it is often the case that a plurality of iodine filters are tested in terms of equipment, it is convenient to be able to replace the iodine filters.

Air containing a high concentration of argon is supplied to the iodine filter. In this case, the argon concentration may be higher than the argon concentration in the iodine adsorbent, but it is preferable that the argon concentration is higher than 5% to facilitate detection of the change in the concentration. The time to start flowing the air whose concentration has been increased is transmitted from the air introduction device to the argon concentration measurement device as information, and the presence or absence of leakage of the iodine filter is determined from the time difference from the time when the high concentration argon was measured with the argon concentration measurement device. judge.

The procedure for determining the presence or absence of this leak is the same as in the case of Example 1, and when high-concentration argon is detected earlier than the time previously measured by the normal iodine filter, the iodine filter tested leaks. Will exist. The presence or absence of a leak can be automatically determined by previously inputting the time difference in a normal case to the argon concentration measuring device.

Since the iodine adsorbent after the leak test is adsorbed with argon, it is preferable to remove air from the iodine adsorbent by flowing air having a low argon concentration.

The iodine filter that was normal in this leak test can be used as it is in a nuclear facility. Further, in the iodine filter in which the leak is found, the leak part is eliminated by vibration or the like, or the iodine adsorbent is refilled in the iodine filter. In this case, the presence / absence of a leak is determined again by this leak test method.

As described above, according to the present embodiment, the same effect as that of the first embodiment can be obtained because only the air with the argon concentration changed is flowed and the time delay of the concentration change is measured. Although the type of iodine adsorbent was not specified in the above examples, activated carbon, silver-impregnated activated carbon, silver zeolite,
Whether or not any iodine adsorbent such as silver mordenite, silver silica gel, or silver alumina has a leak can be determined.

In this embodiment, argon is selected as the leak detecting gas component, but the same effect can be obtained by selecting a component other than argon. However, in this case, it is necessary to install a device capable of measuring the component instead of the argon concentration measuring device. The procedure of the test is exactly the same as the above, including the ventilation of gas containing a high concentration component, the grasp of the time delay of the detection at the outlet side after the introduction of the high concentration component, and the determination of the presence or absence of leak.

Embodiment 4 A leak test apparatus for iodine filters according to a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, propane is supplied to the iodine filter, and the time delay when the propane discharged from the iodine filter is detected is automatically detected.
This is a method for determining the leak of the iodine filter.

A propane introducing device is installed upstream of the iodine filter to be tested. The propane detection device is connected to a pipe that connects the propane introduction device and the propane inlet of the iodine filter, and a pipe that connects the propane outlet of the iodine filter and the propane recovery device, respectively.
The gas flow from the propane introduction device to the propane recovery device through the iodine filter and to the propane detection device is closed, and there is no outflow of gas to the outside or inflow of gas from the outside.

Propane is supplied to the iodine filter from the propane introducing device. In this case, propane may be used alone, but there is no problem as long as it is contained in an amount that can be detected by the propane detection device. The propane detection device is set to detect propane supplied to the iodine filter first, and is switched so as to detect the time when propane is started to flow and at the same time detect propane discharged from the iodine filter next. The presence / absence of a leak in the iodine filter is determined from the time from the switching of the propane detection device as described above until the detection of propane discharged from the iodine filter.

The procedure for determining the presence / absence of this leak is the same as in the case of the first embodiment, and the time when the propane detected as described above is started to flow and the propane discharged from the iodine filter is detected with respect to the normal iodine filter. If propane is detected earlier than the difference from the time before (measured in advance), there is a leak in the iodine filter tested. If the time difference when the iodine filter is normal is input to the propane detection device in advance, it is possible to automatically determine whether the iodine filter leaks.

Since the iodine adsorbent after the leak test is in the state of adsorbing propane, it is preferable to remove propane from the iodine adsorbent by flowing air having a low propane concentration. Also, since propane does not exist in the atmosphere, it is desirable to recover it with a propane recovery device after the test.

The iodine filter that was normal in this leak test can be used as it is in a nuclear facility. Further, in the iodine filter in which the leak is found, the leak part is eliminated by vibration or the like, or the iodine adsorbent is refilled. In this case, the presence / absence of a leak is determined again by this leak test method.

As described above, according to this embodiment, since propane is flowed and the time until detection at the outlet is simply measured,
The same effect as that of the first embodiment can be obtained.

In this embodiment, propane is selected as the leak detecting gas component, but the same effect can be obtained by selecting a component other than propane. However, in this case, it is necessary to install a device capable of measuring the component instead of the propane detection device. The procedure of the test is exactly the same as that described above, including aeration of a gas containing a component alone or a gas containing the component, grasping the time until the detection at the outlet side after the introduction of the component, and determining the presence or absence of a leak.

Example 5 As a fifth example of the present invention, a leak test device for an iodine filter installed in an off-gas treatment device of a radioactive substance handling facility (for example, a nuclear power plant) will be described with reference to FIG.

In the radioactive substance handling facility, a pretreatment facility is provided upstream of the iodine filter, and a posttreatment facility and a stack are provided downstream of the iodine filter. The off-gas inlet of the iodine filter and the pretreatment facility, and the off-gas outlet of the iodine filter, the post-treatment facility and the stack are connected by pipes, respectively. An air introduction device that introduces the air whose humidity has been changed into the iodine filter is connected to a pipe connected to an offgas inlet of the iodine filter. A sampling line for sampling the gas discharged from the iodine filter is connected to a pipe connected to the offgas outlet of the iodine filter. Further, it is possible to send information on the time when the humidity in the air supplied to the iodine filter is changed from the air introducing device to the humidity measuring device. The gas flow from the air introducing device to the humidity measuring device through the iodine filter is preferably closed by a valve existing in the middle of the off-gas line, but there is no problem as long as the leak test air flows.

After removing the moisture in the iodine filter as in Example 1, high-humidity air is supplied from the air introducing device into the iodine filter, and the time at which the supply is started is transmitted to the humidity measuring device as information. The humidity measuring device samples the air discharged from the iodine filter through the sampling line, measures the humidity in this air, and measures the humidity in the air from the difference between the start time transmitted from the air introducing device and the measuring time in the humidity measuring device. The presence or absence of a leak is determined.

The procedure for determining the presence / absence of the leak is the same as in the case of Example 1, and when the humidity is detected earlier than the time previously measured by the normal iodine filter, the tested iodine filter has the leak. Will be done. If the above-mentioned time difference in the case where the humidity measuring device is normal is input in advance, the presence or absence of leak can be automatically determined.

Since the iodine adsorbent after the leak test is in a state of adsorbing moisture, it is preferable to remove the moisture from the iodine adsorbent by flowing low humidity air.

The iodine filter that was normal in this leak test can be used as it is. Further, in the iodine filter in which the leak is found, the leak part is eliminated by vibration or the like, or the iodine adsorbent is refilled.

As described above, according to this embodiment, since the air whose humidity has been changed is made to flow by using the sampling line and only the time delay of the humidity change is measured, it can be mounted on the actual machine very easily and at low cost. It is possible to determine whether or not there is a leak in the iodine filter that has been processed.

In this embodiment, water (water vapor) was selected as the leak detecting gas component, but the same effect can be obtained by selecting other components. However, in this case, it is necessary to install a device capable of measuring the component instead of the humidity measuring device.

[0056]

According to the present invention, the presence or absence of a leak in the iodine filter can be detected very easily and at low cost. Further, not only the iodine filter before being mounted on the actual machine but also the leak detection on the iodine filter after being mounted on the actual machine can be easily performed. Furthermore, since the gas component contained in the atmosphere is used as a leak detection means, it is easy to handle,
No worry about environmental pollution.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a leak test device for an iodine filter that is an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a leak detection method according to the present invention.

FIG. 3 is a configuration diagram of a leak test device for an iodine filter that is another embodiment of the present invention.

FIG. 4 is a configuration diagram of a leak test device for an iodine filter that is another embodiment of the present invention.

FIG. 5 is a configuration diagram of a leak test device for an iodine filter that is another embodiment of the present invention.

FIG. 6 is a configuration diagram of a leak test device for an iodine filter that is another embodiment of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichi Miura 7-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Energy Research Laboratory

Claims (8)

[Claims] 1. In a leak test method for an iodine filter, which removes radioactive iodine contained in exhaust gas discharged from a nuclear facility by an iodine adsorbent, air in which the composition of a gas component contained in air is changed is iodine. A leak test method for an iodine filter, comprising venting through a filter, and detecting a time delay of the composition change of the air on the outlet side of the iodine filter with respect to the composition change of the air on the inlet side of the iodine filter. 2. The gas components contained in the air and changing the composition of the air include nitrogen, oxygen, argon,
Carbon dioxide, neon, helium, methane, krypton,
Hydrogen, nitrous oxide, carbon monoxide, xenon, ozone,
The iodine filter leak test method according to claim 1, wherein the leak test method is at least one of nitrogen dioxide, ammonia, sulfur dioxide, and water vapor. 3. The leak test method for an iodine filter according to claim 1, wherein the gas component adsorbed on the iodine adsorbent during the leak test is removed from the iodine adsorbent after the leak test. 4. A leak test method for an iodine filter, which removes radioactive iodine contained in exhaust gas discharged from a nuclear facility with an iodine adsorbent, wherein a gas component adsorbed on the iodine adsorbent is previously removed or After reducing the concentration of the gas component in advance, a gas containing this gas component is passed through the iodine filter, and the time delay of appearance of the gas component on the outlet side of the iodine filter is detected. Filter leak test method. 5. In a leak test method for an iodine filter, which removes radioactive iodine contained in exhaust gas discharged from a nuclear facility by an iodine adsorbent, a concentration higher than that of a gas component adsorbed on the filter adsorbent. A method for leak test of an iodine filter, comprising: passing a gas containing the gas component through the iodine filter, and detecting a time delay of appearance of the gas component at an outlet side of the iodine filter. 6. A gas containing a component adsorbed to and desorbed from an iodine adsorbent is passed through an iodine filter to detect a time delay of the component appearing on the outlet side of the iodine filter. Characteristic iodine filter leak test method. 7. A gas generator for changing the concentration of a component contained in the gas supplied to the iodine filter, a device for holding the iodine filter, and a device for measuring the concentration of the component in the gas passed through the iodine filter. Leak test device for iodine filter. 8. A gas generator capable of changing the component concentration is installed in the upstream sampling line of the iodine filter of the off-gas treatment system for nuclear facilities, and a device capable of measuring the component concentration in the gas is installed in the downstream sampling line. A leak test device for iodine filters.