JPS63212857A - Apparatus for testing rare gas adsorbing capacity of activated carbon - Google Patents

Abstract

PURPOSE:To obtain a highly accurate low cost apparatus for testing the rare gas adsorbing capacity of activated carbon, by providing an automatic sampling apparatus for keeping the quantity, supply time and supply interval of the sample gas batchwise supplied to a gas chromatograph constant. CONSTITUTION:Sample gas is continuously sent to a sample gas quantifying device 23 from the solid line part of a change-over valve 22 at a time other than a sampling time to perform the washing or gas substitution in the quantifying device 23 while carrier gas is continuously supplied to gas chromatography 15. The flow passage of the change-over valve 22 is changed over (dotted line) for a definite time at every interval set to a controller 24 to sent the quantified gas in the quantifying device 23 to the gas chromatography 15 to analyze the same. A sampling pump 6 suppresses pressure variation accompanied by the pressure difference between the sample gas and the carrier gas. Since a sampling interval is set by a predetermined formula, the CO2 detection time of the gas chromatography becomes shorter and CO2 in the sampling gas before the previous time is detected on the chromatograph but the concn. of Kr can be measured without superposing a CO2 detection value on the peak of non-radioactive Kr.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to the noble gas adsorption of activated carbon filled in an activated carbon type rare gas hold-up device that adsorbs and removes rare gases from radioactive gaseous waste. This invention relates to an activated carbon rare gas adsorption capacity test device for testing the capacity of activated carbon.

(Prior art) In nuclear couplants, especially boiling water nuclear power plants,
Radioactive rare gases such as krypton and xenon produced in the reactor are extracted from the tardon condenser to the gaseous waste treatment system, and multiple activated carbon rare gas hold up towers filled with activated carbon are arranged in series. After being subjected to delayed attenuation treatment using an activated carbon rare gas hold-up device, it is released into the atmosphere.

Therefore, it is necessary to confirm that this activated carbon rare gas hold-up device has sufficient delay performance.
The adsorption capacity of activated carbon is tested before and periodically after plant startup.

The conventional method for testing activated carbon's rare gas adsorption capacity was to use an activated carbon rare gas test device as shown in Figure 2 to measure the concentration of radioactive Kr-85 as a tracer. .

That is, the tracer K r- is supplied from the krypton supply device 3 of the activated carbon rare gas adsorption capacity testing device 2 to the upstream side of the activated carbon type rare gas holding up tower 1 disposed in the gaseous waste treatment system.
A constant amount of Kr gas containing 85 is injected into the system via valve 4 in a pulsed manner. The injected Kr-85-containing Kr gas is carried by the air flowing through the system and passes through the activated carbon rare gas hold up tower 1 while being held up in sequence. Meanwhile, each activated carbon rare gas hold up tower 1.1,...
The valves 5.5... are sequentially opened and closed from the outlet side of..., and the gas that has passed through each unit is sent to the ionization chamber 7 using the sampling pump 6.
The Kr-85 concentration in the sample gas is sampled and the change over time in the Kr-85 concentration is measured by the radiation measuring device 8.

The adsorption capacity of activated carbon is evaluated using the system flow rate f (m3/h), K
This is done by comparing the value of the dynamic adsorption coefficient K (m'/1on) obtained from the following equation from the activated carbon IM (ton) at the time th (h) when the r-85 concentration reaches its peak with a reference value.

K=th-f/M (I)However, in the conventional method) (r-85, a radioactive isotope (RI), is used as a tracer, so the test equipment becomes an RI-using device, and the radiation There are various restrictions on the use of RI, such as the establishment of controlled areas and measures against radioactive leakage, resulting in longer test periods and higher test costs, as well as the need for construction and testing of other systems, especially before plant startup. However, this had the disadvantage of having a negative impact on the plant construction period and cost.

In addition, the concentration of Kr-85 used in the test is higher than the extremely small rare gas concentration during actual plant operation in order to increase detection sensitivity, which is desirable from the nuclear facility's policy of suppressing RI emissions. There wasn't.

In view of these circumstances, an activated carbon rare gas adsorption capacity testing device as shown in FIG. 3 using non-radioactive krypton has been proposed, for example, in Japanese Patent Laid-Open No. 60-218064.

That is, in FIG. 3, non-radioactive Kr is supplied in a pulsed manner from the krypton supply device 10 of the activated carbon rare gas adsorption capacity testing device 9 to the upstream side of the activated carbon type rare gas holding up tower 1, the flow rate of which is adjusted by the regulating valve 11. injected into the system. After that, each activated carbon rare gas hold up tower 1.1,...
The sample gas is introduced into the sample gas supply pipe 12 by the sampling pump 6 by sequentially opening and closing the valves 5.5, . The sample gas sampled by the sampler 14 is injected into the sample injection port of the gas chromatography 15 and subjected to Kr concentration analysis.

Note that 16 in the figure is a carrier gas supply device for supplying carrier gas to the gas chromatography 15.

In this method, gas sampling and Kr concentration analysis by chromatography are performed in batch processing.
In the concentration range where the adsorption form is Henry type, the time-concentration curve becomes a Gaussian distribution, so the data obtained from each sampling was fitted to a Gaussian distribution to find the time th at which the Kr concentration peaks. , (I> The adsorption capacity of activated carbon is evaluated by the formula.

(Problems to be Solved by the Invention) Using the conventional non-radioactive Kr described above, Kr1i! is produced in a batch manner by gas chromatography. In the method of measuring chromatography, it goes without saying that the greater the number of data points, that is, the shorter the sampling interval, the better the accuracy of the test, but the sampling interval is influenced by the time required for gas chromatography analysis. In other words, in gas chromatography, for example, an analyte gas is passed through a long and narrow column filled with an activated carbon adsorbent, and the analyte is separated into each individual gas by taking advantage of the fact that the hold-up time differs depending on the type of gas. A detector detects peaks of thermal conductivity, for example, and the type and concentration of gas are measured from the retention time and peak height of each peak.

Therefore, one analysis ends when all the gas components in the injected sample gas have passed through the column, so if the sample gas contains gas components with long retention times, the analysis time will also be longer, and the sampling time will be longer. The interval also becomes longer, and fitting accuracy decreases.

In an activated carbon noble gas adsorption test in a gaseous waste treatment system of an atomic couplant, clean air, such as instrument air, is normally flowed through the system. The composition of the air is 78%N2.
21% Q2. 0.9% Ar So, 0.9% CO2 and trace amounts of Ne, He, etc., but when Kr is added to this and subjected to gas chromatography, the chromatogram will be 1 tsubo as shown in Figure 4. That is, in FIG. 4, the horizontal axis represents time (retention time) and the vertical axis represents the detected peak height, but the Kr peak is detected as the peak indicated by the symbol ■ in the figure, and immediately after the peak ■ of N2 and 02. appears in

On the other hand, as shown by the symbol ■ in the figure, the CO2 peak appears much later than the peaks of Kr and other air composition gases, so one gas chromatography analysis needs to be performed for a time longer than the CO2 detection end time (Te3). However, the sampling interval was wasted compared to the analysis time required to detect Kr, which is the purpose of the test, and this resulted in a decrease in test accuracy.

In addition, in the activated carbon rare gas adsorption capacity test device indicated by reference numeral 9 in FIG. 3, the gas waste treatment is operated at negative pressure, so the sample gas sampled by the sampler 14 is also under negative pressure. In order to inject the carrier gas into the gas chromatograph 15 against the pressure of the carrier gas, it is necessary to inject the carrier gas under pressure using a piston mechanism or the like. Further, the sampler 14 requires a backflow prevention mechanism from the gas chromatography 15 side, a mechanism for cleaning residual gas in the sampler 14 in preparation for the next sampling, etc., making the structure complicated and the operation complicated. When automating this series of sampling operations, there are disadvantages in that there are many operation parts, the control becomes complicated, and the cost of the test equipment increases.

Furthermore, since the sampling system is under negative pressure as mentioned above,
There was also a fear that test accuracy would deteriorate due to in-leakage.

The present invention has been made in view of the above points, and provides a low-cost and highly reliable activated carbon rare gas adsorption capacity testing device using non-radioactive krypton gas, which has high test accuracy, has a simple structure, and has an automatic sampling function. The purpose is to provide.

[Structure of the Invention] (Means for Solving the Problems) As a means for solving the above problems, as shown in FIG. A hexagonal switching valve 22 is provided in the sample gas discharge pipe 21 and the gas chromatography 15, and the sample gas quantitative meter 23 connected via this switching valve 22 and the switching valve 22 are switched at regular intervals for a certain period of time. Automatic sampling device 1 configured with a controller 24 that links gas chromatography 15 to switching
9 will be provided. Further, the sample supply pipe 12 is provided with a sampling pump 6 . Roughly speaking, the controller 24 is provided with a timer function that can set the switching interval of the switching valve 22, thereby setting the switching interval within a range determined by the following logical formula.

(Tkz <r <TC+) AND [NOT
((Tc+Tk2)/NET<(Te3-T
kz ) /N)] ...... (I) Here, Tk +...Kr detection start time Tk of gas chromatography z...Detection end time TC+...of gas chromatography CO2 detection start time Tc 2... CO2 detection end time T of gas chromatography... Set time N... Integer (1, 2,...) (Operation) The operation of the above means will be explained below.

In FIG. 1, the sample gas is continuously sent to the sample gas meter 23 as shown by the solid line in the six-way switching valve 22 except during sampling, and the inside of the sample gas meter 23 is cleaned and gas replaced. On the other hand, carrier gas is continuously supplied to the gas chromatograph 15.

At each interval set in the controller 24, the six-way switching valve 2
The flow path 2 is switched as shown by the dotted line for a certain period of time required to send the gas in the sample gas meter 23 to the gas chromatography 15, and the fixed amount of sample gas in the sample gas meter 23 is transferred to the carrier gas. is supplied to the gas chromatography 15, and at the same time the controller 2
The gas chromatography 15 is reset to the signal No. 4 and starts a new analysis.

In addition, the sampling pump 6 is the automatic sampling device 1.
The pressure of the sample gas supplied to the gas chromatography 9 is increased to suppress pressure fluctuations during sampling due to the pressure difference between the sample gas and the carrier gas, thereby preventing the function of the gas chromatography 15 from being impaired.

Since the sampling interval is set by formula (n), it is shorter than the CO2 detection time of the gas chromatography, and CO2 in the sample gas supplied to the gas chromatography in the previous or previous sampling is detected on the chromatogram. However, the Kr concentration does not overlap with the Kr peak, and the Kr concentration can be reliably measured at short sampling intervals.

(Example) Hereinafter, an example of the present invention will be described with reference to FIG.

In FIG. 1, a pipe 25 connected to the upstream system piping of the activated carbon type rare gas holding up tower 1 is connected to the krypton supply device 10 of the activated carbon rare gas adsorption capacity testing device 18 via the valve 4.
A regulating valve 11 is provided in the middle.

On the other hand, activated carbon rare gas hold up tower 1.1...
A pipe 26 branches from each column outlet pipe and is connected via a valve 5 to a sample gas supply pipe 12 of an activated carbon rare gas adsorption capacity testing device 18. A sampling pump 6 is provided in the middle of the sample gas supply pipe 12, and the downstream end of the sampling gas supply pipe 12 is connected to the boat A of the six-way switching valve 22.
It is connected to the. The boat B of the six-way switching valve 22 is connected to the sample gas discharge pipe 21 and communicates with the downstream system piping of the activated carbon rare gas hold up tower 1. Also,
Boat C and boat D of the six-way switching valve 22 communicate with each other via a sample gas meter 23, boat E communicates with the carrier gas supply device 16 via the carrier gas supply pipe 20, and boat F communicates with the gas chromatography 15. It is connected.

The six-way switching valve 22 is driven by a motor or an electromagnetic coil or the like, and changes from A to D as shown by the solid line in FIG.

It is possible to switch between a state in which B-C, E-F communicate with each other and a state in which A-B, C-F, and D-E communicate as shown by dotted lines in FIG. 1, and the switching is performed by the controller 24. It will be done. The state shown by the solid line in Figure 1 below is the normal state, and the state shown by the solid line in Figure 1 is the normal state.
The state indicated by the dotted line in the figure is called the sampling state.

The switching interval of the six-way switching valve 22 from the normal state to the sampling state is set by the controller 24 within the range shown by equation (I), and the return from the sampling state to the normal state is also determined by the timer function provided in the controller 24. It is done.

In addition, the controller 24 is connected to the gas chromatography 1 in conjunction with the switching of the hexagonal switching valve 22 to the sampling state.
5 is also provided with a mechanism for issuing a reset signal. This controller 24 can be configured by a combination of a timer, a switch, and a relay mechanism, or a combination of a timer and an electric sequence circuit, but a programmable controller using a microprocessor or a personal computer is also suitable.

In addition, 27 in the figure is an exhaust pipe of the gas chromatography 15.

Next, the operation of the above embodiment will be explained.

Activated carbon rare gas hold up tower 1 with air flowing through it
Open the valve 4 in the upstream system piping of the krypton supply device 10
Non-radioactive Kr is injected in a pulsed manner through the tube 25 for a fixed period of time, for example, 5 minutes.

The flow rate of Kr is adjusted to a constant flow rate by a regulating valve 11. K
Since the system side is operated at a negative pressure of about 1100 mmHg, the injection of r can be easily carried out by using a container capable of maintaining an appropriate pressure in the krypton supply device 10, such as a cylinder equipped with a regulator.

The injected Kr gas is diluted and transported by the air flowing through the system, and is then transferred to the activated carbon rare gas holding up tower 1.1...
The gases passing through each province are held up by the pipe 26, widening the concentration time distribution, and being guided downstream. The sample gas is guided to the sample gas supply pipe 12, but at this time, the pressure is increased to above atmospheric pressure by the sampling pump 6, and the sample gas is sent to port A of the six-way switching valve 22.

When the six-way switching valve 22 is in the normal state, the sampling gas flows through the path A-+D→23→C-+B, cleans the inside of the sample gas meter 23, replaces the gas, and is discharged from the sampling gas exhaust pipe 21. Ru.

On the other hand, the carrier gas is supplied from the carrier gas supply device 16 to the carrier gas supply pipe 20 and the port E of the hexagonal switching valve 22, and is discharged to the exhaust pipe 27 through the gas chromatography 15 along the EF route.

From this state, when a switching signal is sent to the six-way switching valve 22 at each time set in the controller 24, the six-way switching valve 22
is in the sampling state, and the sample gas is 12→A-
+B → 21 path bypasses the sample gas quantifier 23 and a fixed amount of sample gas is sampled in the sample gas quantifier 23, and this is from 20 → E
It is carried to the gas chromatograph 15 by the carrier gas flowing along the path -+D→23→C-F→15, and simultaneously analyzed by the gas chromatograph 15 reset by a signal from the controller 24.

The return from the sampling state to the normal state is performed after a certain period of time has elapsed using the timer of the controller 24. This sampling time varies depending on the container of the sample gas meter 23 and the carrier gas flow rate, but in general gas chromatography, the sample amount is mβ is sufficient, and approximately 1 minute is appropriate.

After returning to normal state, the carrier gas is 20→E-F→
The sample gas in the column is continuously supplied to the gas chromatography through 15 routes, and the sample gas in the column is guided to the detection section where Kr is analyzed 11 times.

By continuously repeating the above series of operations,
The change over time in the Kr concentration at the outlet of the activated carbon rare gas rare gas hold up tower 1 is measured, and the rare gas adsorption capacity of the activated carbon is determined by equation (1).

By the way, if the sampling interval is less than the CO2 detection time TC+ of gas chromatography, as shown in Figures 5 and 6, the CO2 peak will not appear in the first analysis, but will appear on the chromatograph from the second and subsequent samplings. Appears late. That is, in Figures 5 and 6, (A>, (B), and (C) indicate the start of the first, second, and third sampling, that is, the reset time of the gas chromatography, and King indicates the sampling interval. In this example, Tk2 < rcl / 2
<t<TC+. In addition, Fig. 5 shows that if the condition [NOT ・((Tc1-Tk2) /N≦D≦(Te3-Tk+) /N)] is not satisfied in the theoretical formula of <IF), then Fig. 6 is satisfied. Indicate the case.

In the case of Fig. 5, (C1-Tk2) <T < (C2-Tk,), that is, (TC+T) <■
h+ < (Te3-d), and the Kr peak in the chromatogram from the second and subsequent samplings overlaps with the CO2 peak from the previous sampling, making it impossible to measure the Kr concentration correctly.

On the other hand, in the case of FIG. 6, when (Tc2-Tkl)<T, that is, Tc1-t<Tk+, the CO2 peak at the time of the previous sampling that appears in the chromatogram from the second and subsequent samplings does not overlap with the Kr peak.

The retention time of each gas varies depending on the gas chromatography column length, adsorbent, and carrier gas flow rate, but if Tk = 9 minutes, Tk2 = 10 minutes, TC
Assuming that 1 = 20 minutes and Tc2 = 22 minutes, 13 minutes≦
If the shortest time is 13 minutes, the sampling interval can be made 40% shorter than when the sampling interval is Tc2 or more. Generally, this is because the width of the Kr concentration distribution at the outlet of each unit of the activated carbon rare gas holding up tower in a BWR atomic coupler is 3 hours at the first tower exit and 10 hours at the final tower exit. Data can be obtained, the test can be performed with sufficient accuracy for practical use, and the test accuracy can be significantly improved compared to the case where ■≧TC2.

In addition, the injection amount of Kr is determined by the detection sensitivity of gas chromatography, but if an activated carbon column is used for TCD detection and He is used as the carrier gas,
It has been confirmed through experiments that the detection sensitivity of r can be secured to a level of 10 ppm or lower. Therefore, if the concentration is about 1 ooppm at the outlet of the final gas hold up tower 1, sufficient data can be obtained to obtain a Kr concentration time curve. If the air flow rate is 40 m3/h and injection is performed for 5 minutes, the Kr injection amount is about 70λ, which is within the Uenry type adsorption equilibrium range, and the adsorption state is not different from the actual plant operation.

As described above, when the above embodiment is used in an activated carbon rare gas adsorption capacity testing device, the sampling section has a simple structure and configuration, which facilitates automation, shortens the sampling interval, prevents in-leakage in the sample line, and The test accuracy is improved by reducing the pressure difference between the gas and the carrier gas, thereby providing an activated carbon rare gas adsorption capacity testing device using non-radioactive krypton that is low cost, easy to operate, and highly reliable.

[Effects of the Invention] As described above, the present invention provides low cost, ease of operation,
It is possible to provide an activated carbon rare gas adsorption capacity test device with high reliability and test accuracy, which has the effect of improving the reliability of activated carbon adsorption tests using non-radioactive krypton gas and making the tests easier.

[Brief explanation of the drawing]

Fig. 1 is a schematic system diagram showing an embodiment of the present invention, Fig. 2 is a schematic system diagram showing a conventional activated carbon rare gas adsorption ability test device using radioactive krypton as a tracer, and Fig. 3 is a schematic system diagram showing a conventional activated carbon rare gas adsorption capacity test device using radioactive krypton as a tracer. A schematic system diagram showing an activated carbon rare gas adsorption capacity test device using activated carbon, Figure 4 is a diagram showing an example of a chromatogram of air containing krypton, and Figure 5 is a diagram showing a case where the sampling interval for air containing krypton is inappropriate. FIG. 6 is a diagram showing an example of a chromatogram of air containing krypton obtained by the test apparatus of the present invention. 1...Activated carbon rare gas holding up tower 2...Activated carbon rare gas adsorption capacity testing device 3.
......Krypton supply device 4...
...Valve 5...Valve 6...Sampling pump 7...
..... Ionization chamber 8 ..... Radiation measuring device 9 ..... Activated carbon rare gas adsorption ability test device 10
......Krypton supply device 11...
...Adjusting valve 12...Sample gas supply 13...
... Valve 14 ... Sampler 15 ... Gas chromatography 16 ...
......Carrier gas supply device 17...
...Valve 18...Activated carbon rare gas adsorption capacity test device 1
9... Automatic sampling device 20...
...Carrier gas supply pipe 21...
・Sample gas discharge pipe 22... Six-way switching valve 23... Sample gas meter 24...
..... Controller 25 ..... Pipe 26 ..... Pipe 27 ..... Exhaust pipe

Claims (5)

[Claims] (1) In order to test the rare gas adsorption ability of the activated carbon filled in the activated carbon rare gas hold-up tower, an air supply means is provided on the upstream side, a non-radioactive krypton supply means is provided on the inlet side of the activated carbon rare gas hold-up tower, and the In an activated carbon rare gas adsorption capacity test device equipped with a gas chromatography as a rare gas concentration measuring means on the outlet side of an activated carbon type rare gas hold-up column, the sample gas amount, sample gas supply time, and sample supplied in batch to the gas chromatography are as follows. An activated carbon rare gas adsorption capacity testing device characterized by being equipped with an automatic sampling device that maintains a constant gas supply interval. (2) The sample gas supply interval is equal to or longer than the krypton gas detection end time of gas chromatography and less than the carbon dioxide detection start time, and is equal to one integer of the difference between the carbon dioxide detection time and the krypton gas detection end time and the carbon dioxide detection time. 2. The activated carbon rare gas adsorption capacity test device according to claim 1, wherein the activated carbon rare gas adsorption capacity test device is set to a time excluding one of said integer fraction of the difference between the start time of detection of krypton gas and krypton gas detection start time. (3) The automatic sampling device has a gas meter whose inlet side is connected to a sample gas supply pipe and a carrier gas supply pipe, and whose outlet side is connected to a sample gas discharge pipe and gas chromatography via a switching mechanism. An activated carbon rare gas adsorption capacity test device according to claim 1. (4) The activated carbon rare gas adsorption capacity test device according to claim 3, wherein a six-way valve is used as the switching mechanism. (5) The activated carbon rare gas adsorption capacity test device according to claim 1, wherein a pump for sampling the sample gas is provided upstream of the automatic sampling device.