JPS6133369B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an apparatus for recovering and measuring tritium in exhaust gas in order to monitor the amount of tritium in exhaust gas discharged from nuclear equipment. In general, the amount of radioactive materials contained in waste from nuclear power plants and other facilities that handle radioactive materials must be monitored to prevent environmental pollution. Among these radioactive substances, especially tritium
Since ^3H is a nuclide with a long half-life, its concentration must be measured and monitored, and its emissions must be regulated, even if the concentration contained in waste, such as exhaust gas, is extremely low. Therefore, in order to measure the amount of such low concentrations of tritium contained in exhaust gas, the general method is to condense and recover the moisture in the exhaust gas, and then measure the tritium contained in this recovered moisture. Adopted. By the way, with such a method, the tritium concentration in the exhaust gas cannot be accurately determined unless the amount of water in the exhaust gas is accurately measured. Of course, it is possible to determine the amount of moisture from the temperature and humidity of the exhaust gas, but this method has low accuracy and cannot be put to practical use. Therefore, in the above method, it is necessary to capture and recover moisture in the exhaust gas with high efficiency and accurately determine the amount of moisture in the exhaust gas. For this reason, such water recovery has conventionally been carried out using a device as shown in FIG. That is, A is an exhaust pipe that discharges exhaust gas, and the exhaust gas discharged from this exhaust pipe A is sent to a sampling nozzle B.
The temperature and humidity are measured by a temperature/humidity detector D after passing through a filter C, and the measured values are recorded on a recorder E. This gas is then compressed to a predetermined pressure by a compressor F, and sent to a cooler H through an accumulator G. This compressed gas is cooled by a cooler H, and the moisture contained in the gas is condensed and liquefied, and collected in a sample collection container I. After being measured, the pressure regulating valve K
is configured to be returned to the exhaust stack through the Then, the amount of moisture in the exhaust gas is determined from the amount of recovered moisture and the gas flow rate, and the recovered moisture is measured using a liquid scintillation counter to determine the tritium concentration in this recovered moisture. The tritium concentration in the exhaust gas is determined from the results. However, this method has a problem in that the amount of moisture in the exhaust gas cannot be accurately measured. That is, in the above-mentioned apparatus, in order to prevent water from freezing, the cooling temperature in the degrading device H must be set to 0° C. or higher. By the way, the saturated vapor pressure of water is 4.58 mmHg at 0°C, so the gas discharged from the cooler H contains 4.58 mmHg of water vapor, and this water vapor is returned to the exhaust stack A without being recovered. Of course, Compressa F
If the compression pressure is increased, the water recovery rate will be increased, but if the pressure is increased too much, the structure of the compressor F will become complicated, its maintenance and inspection will be troublesome, and problems such as increased leakage will occur. In reality, the pressure was limited to about 3 to 5 kg/cm ² , and there was a limit to the improvement in water recovery rate.
For this reason, in the past, the pressure compressed by compressor F was maintained constant, and the relationship between the temperature and humidity of the exhaust gas and the moisture recovery rate was determined in advance.
It would be troublesome and inaccurate if the amount of water in the exhaust gas was not determined by making corrections. The present invention has been made based on the above circumstances, and its purpose is to efficiently capture and recover moisture in exhaust gas, to easily and accurately determine the tritium concentration in exhaust gas, and to continuously The object of the present invention is to obtain a tritium concentration measuring device which is capable of performing accurate measurements, has a simple structure, and is highly durable and reliable. The present invention will be explained below using examples. First, a first embodiment of the apparatus of the present invention will be described with reference to FIG. In the figure, numeral 1 is an exhaust pipe that discharges exhaust gas. The exhaust gas flowing through the exhaust stack 1 is configured to be sampled by a sample gas sampling mechanism 2. Reference numeral 3 designates the sampling nozzle, which is inserted into the exhaust pipe 1 and connected to the suction side of the pump 5 via the suction pipe 4. Further, a discharge pipe 6 is connected to the discharge side of the pump 5, and the discharge pipe 6 is connected to two branch pipes 7a and 7b. Moisture adsorbents 8, 8, which will be described later, are connected to the middle of these branch pipes 7a, 7b, respectively. Further, these branch pipes 7a, 7b are provided with switching valves 9a, 9b, 10a, 10b located upstream and downstream of the moisture adsorbents 8, 8, respectively. Further, these branch pipes 7a and 7b are each connected to a return pipe 11, and this return pipe 11 opens into the exhaust pipe 1. Therefore, the exhaust gas flowing inside the exhaust pipe 1 is sucked and sampled from the sampling nozzle 3 by the pump 5, and is transferred to the branch pipes 7a, 7.
It is configured so that it passes through the moisture adsorbers 8, 8 via the pipe b, and is returned into the exhaust pipe 1 through the return pipe 11. Moreover, the switching valve 9 of each branch pipe 7a, 7b
The valves a, 9b, 10a, and 10b are selectively opened by a control mechanism (not shown), and the exhaust gas selectively collected by the moisture adsorbers 8, 8, that is, the sample gas, is configured to flow through one of them. has been done.
Next, the structure of the moisture adsorbents 8, 8 will be explained. 1
Reference numerals 2 and 12 denote adsorbent storage containers, which are approximately cylindrical in shape. And these adsorbent storage containers 12, 12
Heat insulating materials 13, 13 are provided inside.
A predetermined amount of adsorbents 14, 14, such as molecular sieves 4A, which adsorb moisture, are accommodated in the adsorbent containers 12, 12.
Further, an inflow pipe 15, 15 and an outflow pipe 1 are provided at both ends of these adsorbent storage containers 12, 12, respectively.
6, 16 are connected, and these inflow pipes 15, 15
On-off valves 17 are provided in the middle of the outflow pipes 16, 16, respectively. Further, connection joints 18 are provided at the tips of these inflow pipes 15, 15 and outflow pipes 16, 16, respectively, and these moisture adsorbents 8, 8 are connected to branch pipes 7a, 7b, respectively, in a detachable manner. Furthermore, heaters 19, 19 such as heating wires are built in these moisture adsorbents 8, 8, and the adsorbents 14, 14 can be heated by supplying electricity to these heaters 19, 19. It is configured. Next, a method of capturing and recovering tritium in exhaust gas and measuring the tritium concentration using the above-mentioned apparatus will be explained. First, the switching valves 9a and 10a of one branch pipe 7a are opened, and the switching valve 9 of the other branch pipe 7b is opened.
b, 10b are closed, the pump 5 is operated, exhaust gas is sampled from the exhaust pipe 1, and the sample gas thus sampled is made to flow into one of the moisture adsorbents 8. Then, the moisture in this sample gas is absorbed into one moisture adsorbent 8.
It is adsorbed and captured by the adsorbent 14 inside. After a predetermined amount of sample gas is passed through, the switching valves 9a and 10a of one branch pipe 7a are closed, and the flow of the sample gas to the moisture adsorbent 8 is stopped, and the switching valve of the other branch pipe 7b is closed. 9b and 10b are opened to allow the sample gas to flow through the other moisture adsorbent 8. In addition,
The amount of the adsorbents 14, 14 in the moisture adsorbents 8, 8 is set in advance so as not to be saturated before the flow of the sample gas is stopped. Then, close the on-off valves 17, 17 of one moisture adsorbent 8, remove the connecting joints 18, 18, and remove the connecting joints 18, 18.
Remove it and then install a new moisture absorber. Thereafter, the same operation is repeated to cause the moisture in the sample gas to be adsorbed alternately onto the moisture adsorbents 8, 8.
Then, the entire weight of the removed moisture adsorbent 8 is measured using a weighing scale 20 as shown in FIG. Note that the weight of this moisture adsorbent 8 before adsorbing moisture is measured in advance, and the weight of the absorbed moisture is determined from the difference in weight after adsorbing moisture. In this case, the moisture adsorbent 8 is equipped with an on-off valve 1.
7 and 17 are provided, and these on-off valves 1
7 and 17 are closed before the moisture adsorbent 8 is removed, moisture in the atmosphere is absorbed into the adsorbent 14 between the time the moisture adsorbent 8 is removed and the weight is measured. There is no such thing as being absorbed.
Then, as shown in FIG. 4, the water adsorbent 8 whose weight has been measured is connected to either the inflow pipe 15 or the outflow pipe 16, for example, the outflow pipe 16, to the collection container 21, and the on-off valve 17 of the outflow pipe 16 is connected. When opened, the heater 19 is connected to the power source 22, and the adsorbent 14 is heated by the heater 19. Therefore, the moisture adsorbed in the adsorbent 14 is released, and the released moisture flows into the collection container 21. This recovery container 21 is immersed in a refrigerant 24 housed in a refrigerant container 23, and since the peripheral wall thereof is cooled, the released water, that is, water vapor, is cooled and condensed. Note that the moisture adsorbent 8 that has released moisture has its adsorbent 14 regenerated and used again. The volume of the water collected in the collection container 21 is measured using a measuring device 25 as shown in FIG. 5, and then the tritium concentration Cliq [μ
Ci/ml] is measured. Then, V
[ml], the flow rate of the sample gas is N [/min], the flow time of the sample gas is T [min], and the capture efficiency of adsorbed water is η, then the tritium concentration in the exhaust gas is C.
_H [μCi/ml] can be determined by C _H =Cliq·V/N·T·η×1000. In this method, the moisture in the exhaust gas is adsorbed by the adsorbent 14, so the capture efficiency can be 100% in practice without any problem, almost no correction is required, and the accuracy is high. In addition, in order to confirm this effect,
The following table shows the results of adsorption and recovery of a sample gas whose water content, ie, water vapor pressure, was precisely regulated to a constant level using the above-described apparatus and method.

【table】

[Table] As is clear from this result, the moisture capture efficiency is 100% except when the water vapor pressure is extremely low, almost no correction is required, and the accuracy is high. Note that the amount of water finally recovered in a liquid state is approximately 1/1 of the amount of water adsorbed and captured by the adsorbent 14.
However, the amount of water required for measuring the tritium concentration is sufficient, and the above amount is sufficient. Note that the present invention is not limited to the above embodiments. For example, FIG. 6 shows a second embodiment of the present invention. This second embodiment is based on the inflow pipe 15 of the moisture adsorbent 8.
Also, flexible joints 26, 26 having flexibility are interposed between the outflow pipe 16 and the connecting joints 18, 18. In this second embodiment, even when the moisture adsorbent 8 is connected to the branch pipe 7a of the sample gas sampling mechanism 2, it is in a floating state. There is no need to remove it when measuring the weight. Further, FIG. 7 shows a third embodiment of the present invention.
In this third embodiment, a so-called electronic refrigeration element 27 utilizing the Peltier effect is provided inside a moisture adsorbent 8, and the periphery thereof is surrounded by a heat insulating material 28. In this third embodiment, cooling and heating can be performed by controlling the direction of the electric current supplied to the electronic refrigeration element 27, so temperature control is performed when adsorbing moisture to the adsorbent 14, and when releasing adsorbed cedar fraction. Heating is easy. Furthermore, the present invention is not limited to the above embodiments,
For example, the number of moisture adsorbents is not limited to two, and three or more may be provided as necessary. Furthermore, the present invention is not necessarily limited to the above, and for example, the adsorbent is not limited to Molecular Sieve 4A, but may be other adsorbents that adsorb moisture, such as silica gel, activated carbon, etc. As described above, the present invention allows sample gas to flow through an adsorbent to adsorb moisture, determines the amount of moisture in the sample gas by increasing the weight of the adsorbent, and heats the adsorbent to release moisture. The water in the sample gas is condensed and the tritium contained in this water is measured to determine the tritium concentration in the sample gas. Therefore, almost 100% of the moisture in the sample gas is adsorbed and captured by this adsorbent, and the amount of captured water can be accurately determined by weight measurement, so the amount of moisture in the sample gas is extremely low. Therefore, the tritium concentration in the sample gas can be determined accurately, and the operation is simple without requiring correction or the like. In addition, since multiple moisture adsorbents containing adsorbents are installed and the sample gas is passed through them alternately, the moisture in the sample gas can be adsorbed continuously, allowing for continuous measurement. It is possible to do this and has a simple structure, and it is convenient because the adsorbent can be handled together with the moisture adsorbent.Also, the pressure of the sample gas can be extremely low, which is necessary for the gas to pass through the adsorbent, and pumps, etc. It has a simple structure and good durability. Also, since the adsorbent storage container is equipped with temperature control means,
Operations such as heating to release moisture adsorbed by the adsorbent can be easily performed, and the temperature control by the temperature control means described above becomes more effective due to the heat insulating effect of the heat insulating material. Furthermore, since a flexible joint is connected to the adsorbent container, if the adsorbent container is installed on a weighing scale, the adsorbent container will be in a floating state. The effects are great, such as making it possible to measure weight without removing it from the device.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a conventional device. Also the second
The figure is a system diagram of the first embodiment of the apparatus of the present invention, Figures 3 to 5 are process explanatory diagrams showing the method of the present invention in the order of steps, and Figure 6 is a diagram showing the main parts of the second embodiment of the apparatus of the present invention. The side view and FIG. 7 are longitudinal cross-sectional views of essential parts of the third embodiment. 1...Exhaust stack, 2...Sample gas sampling mechanism, 5...
...Pump, 7a, 7b... Branch pipe, 8... Moisture adsorbent, 9a, 9b... Switching valve, 10a, 10b...
...Switching valve, 14...Adsorbent, 15...Inflow pipe (inflow port), 16...Outflow pipe (outflow port), 17...Opening/closing valve, 18...Connection joint, 19...Heater, 2
6...Flexible joint, 27...Electronic refrigeration element.

Claims (1)

[Scope of Claims] 1. A plurality of adsorbent storage containers each containing an adsorbent therein via a heat insulating material and equipped with a temperature control means, and a plurality of adsorbent storage containers for collecting a sample gas and storing the sample gas therein. A sample gas collection mechanism that selectively switches and supplies the sample gas to the container, an inlet and an outlet formed in the adsorbent container, an on-off valve that opens and closes the inlet and the outlet, and the inlet and the outlet. a connecting joint for removably connecting the sample gas to the sample gas sampling mechanism; a measuring means for weighing the adsorbent container containing the adsorbent in a state in which water in the sample gas has been adsorbed; A tritium concentration measuring device characterized by comprising a condensing and liquefying means that collects and condenses and liquefies the released moisture when moisture is released from the material. 2. The tritium concentration measuring device according to claim 1, wherein the temperature control means is a heater. 3. The tritium concentration measuring device according to claim 1, wherein the temperature control means is an electronic refrigeration element. 4. The tritium concentration measuring device according to claim 1, wherein the adsorbent container is equipped with a flexible joint.