JPS5948672A - Apparatus for monitoring radiactive waste gas - Google Patents

Abstract

PURPOSE:To certainly perform measurement and monitoring with high accuracy, by providing a plurality of moisture recovery mechanisms mutually arranged in parallel and recovering moisture in radioactive waste gas and a carbon dioxide recovery mechanism for recovering carbon dioxide in the radioactives waste gas passing said moisture recovery mechanism. CONSTITUTION:Moisture recovery mechanisms 106A, 106B cool waste gas by cooling medii sent through cooling pipes 108a, 108b from a cooler 107 and moisture contained in the waste gas condensed or coagulated to be separated and recovered. In addition, carbon dioxide in the radioactive waste gas passed through the moisture recovery mechanisms 106A, 106B is absorbed and recovered by carbon dioxide recovery mechanisms 112a, 112b. In this case, because the moisture recovery mechanisms 106A, 106B or the carbon dioxide recovery mechanisms 112a, 112b can be replaced with a new moisture recovery mechanism and a new carbon dioxide recovery mechanism even if contaminated with radioactivity, the concn. of the radioactive nuclide in the waste gas can be certainly measured with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for monitoring radioactive substances in radioactive waste gas discharged from nuclear power generation facilities and the like.

Generally, radioactive waste gas discharged from nuclear power generation facilities and the like is discharged after the radioactive substances contained therein are removed by a waste gas treatment device. By the way, among the radionuclides contained in such radioactive waste gas, 3H +
``C+85Kr etc. have a long half-life, so their concentrations must be regulated to extremely low concentrations.For this reason, strict monitoring is required to see if these nuclides are contained in the emitted waste gas. A device that performs such monitoring needs to be able to measure and detect the above-mentioned nuclides down to extremely low concentrations, and conventional devices have been configured as shown in Figures 1 and 2. The one in Figure 1 monitors 3H and C, and 1 is an oxidation mechanism.The waste gas collected from the exhaust gas exhaust system 2 is first introduced into this oxidation mechanism 1, and the waste gas is The hydrogen, carbon oxide, and hydrocarbon compounds contained in the water are oxidized to produce water and carbon dioxide.Then, the waste gas flowing out from this oxidation mechanism 1 is then sent to the moisture recovery mechanism 3.This moisture The recovery mechanism 3 cools the waste gas using a refrigerant sent from the cooler 4 through the cooling pipe 5, and condenses or solidifies the water contained therein to separate it.Therefore, the water contained in the waste gas is separated. All hydrogen is recovered as water in this moisture recovery device 3, and 3H is also 3H20,”H3
It is recovered in the form of HO.

The waste gas that has passed through the moisture recovery device 3 is then sent to the carbon dioxide recovery mechanism 6. Then, in this carbon dioxide recovery mechanism 6, the waste gas is brought into contact with a carbon dioxide absorption liquid such as monoethanolamine or phenylmethylamine, and the carbon dioxide contained therein is absorbed. Therefore 1
4c is recovered in the carbon dioxide absorption liquid in the form of 14 Co . Therefore, trace amounts of 3H914C contained in the waste gas are also concentrated and recovered in the form of water and carbon dioxide. The amount of radiation emitted from the recovered water and carbon dioxide absorption liquid is measured using a scintillation counter, etc., and the 3H contained in the waste gas is measured.
Measures the concentration of 14C, etc. down to the extremely low concentration range. Also,
In the system shown in FIG. 2, a rare gas concentration separation mechanism 7 and a radiation detector 8 are provided on the downstream side of the carbon dioxide recovery mechanism 6. The rare gas concentration separation mechanism 7 is a permeable membrane or the like I) K
It concentrates and separates rare gases such as r, Xe, etc. The concentrated and separated rare gas is then sent to the radiation detector 8 to measure the radiation dose, which measures radioactive rare gases such as 85Kr contained in the waste gas down to extremely low concentrations. be. By the way, something like this
When relatively high concentrations of 5H, 14C, etc. are contained in the waste gas, these 3H and 14C are concentrated and recovered in the moisture recovery mechanism 3 and carbon dioxide recovery mechanism 6. The carbon dioxide recovery mechanism 6 is radioactively contaminated. As a result, a problem occurs in which subsequent measured values become higher than the actual values.

The present invention has been made based on the above circumstances, and its purpose is to eliminate radioactive waste that does not affect subsequent measurement values even if the waste gas contains relatively high concentrations of radionuclides. The purpose is to obtain gas monitoring equipment.

The present invention will be explained below according to embodiments shown in the drawings.

FIGS. 3(a) and 3(b) show a first embodiment of the present invention. In the figure, reference numeral 101 denotes an oxidation mechanism, and the waste gas collected from the radioactive waste gas discharge system 102 is sent to this oxidation mechanism 101 via a collection pipe 103.

The oxidation mechanism 101 is configured to oxidize hydrogen gas, carbon oxide, and hydrocarbon compounds contained in the waste gas to produce water and carbon dioxide. Therefore, all the hydrogen contained in this gas becomes water, and all the broken carbon becomes carbon dioxide.

Further, the waste gas that has passed through the oxidation mechanism 101 is supplied to the supply pipe 10
4 and a moisture recovery mechanism 106a via the inlet pipe 105,
106b. These moisture recovery mechanisms 106a and 106b are connected to a cooling pipe 108a from a cooler 1θ7.

The exhaust gas is cooled by the refrigerant sent through the exhaust gas 108b, and the moisture contained in the exhaust gas is condensed or solidified to be separated and recovered. And this moisture recovery mechanism 106a.

A plurality of water recovery mechanisms 106b, for example two, are provided in parallel with each other, and the inlet pipe 105 has water recovery mechanisms 106m and 106b.
Inlet valves 109h and 109b are provided corresponding to 06b, respectively. In addition, these moisture recovery mechanisms 106a,
The outlet sides of the water recovery mechanisms 106b are connected in parallel to each other by an outlet pipe 110, and each water recovery mechanism 106m is connected to the outlet pipe 110 in parallel.
, 106b, respectively, outlet valves 111a and 1ll.
b is provided. Further, 112a and 112b are 6-carbon dioxide recovery mechanisms. This carbon dioxide recovery mechanism 112a
, 112b brings the waste gas into contact with a carbon dioxide absorption liquid such as monoethanolamine or phenylethylamine,
It absorbs and recovers the carbon dioxide contained in this waste gas.

A plurality of carbon dioxide recovery mechanisms 112h and 112b, for example two, are provided in parallel, and their inlet sides are connected in parallel to each other by an inlet pipe 113. Each carbon dioxide recovery mechanism 1 is connected to this inlet pipe 113.
Inlet valves 114h, corresponding to 12a and 112b, respectively;
114b is provided. And this inlet pipe 113
is the moisture recovery mechanism 106a via the communication pipe 115,
106b is connected to the outlet pipe 110. Further, the outlet sides of these carbon dioxide recovery mechanisms 112a and 112b are connected in parallel to each other by an outlet pipe 116. Each carbon dioxide recovery mechanism 112a is connected to this outlet pipe 116.
, 112b, respectively, outlet valves 117a, 117.
b and absorption liquid recovery mechanisms 118h and 118b are provided. These absorption liquid recovery mechanisms 118h and 118b separate and recover the vapor of the carbon dioxide absorption liquid contained in the waste gas that has passed through the carbon dioxide recovery mechanisms 112h and 112b by cooling it or using an adsorbent such as synthetic zeolite or activated carbon. The carbon dioxide absorption liquid is drained from the drain valves 119a, 1
It is configured to be discharged to a processing system (not shown) via 19b. The outlet pipe 116 is the discharge pipe 1.
It is connected to the exhaust gas exhaust system 102 via the exhaust gas 20. and between the inlets of the moisture recovery mechanisms 106h, 106b and carbon dioxide recovery mechanisms 112a, 112b and the inlet valves 109a, 109b, 114h, 114b, and the outlets of the moisture recovery mechanisms 106a, 106b and carbon dioxide recovery mechanisms 112a, 112b. and outlet valve 11
1a.

1x1b, 117&, 117b are provided with separable connectors 121, respectively, and by separating these connectors 121, the moisture recovery mechanisms 106a, 106b and the carbon dioxide recovery mechanism 112 are provided.
a, 112b can be removed from the conduit.

The first embodiment of the present invention configured as described above is first explained by the third embodiment.
As shown in FIG.
114m and outlet valve 111a.

117a, the large mouth valve 109b of the other moisture recovery mechanism 106b and the other carbon dioxide recovery mechanism 106b,
114b and outlet valves 111b and 117b are respectively closed to operate the apparatus. Therefore, the waste gas has oxidation mechanism 1
01, one moisture recovery mechanism 106 a s one carbon dioxide recovery mechanism 112a and one absorption liquid recovery mechanism 11
8a.

Then, the oxidation mechanism 101 oxidizes hydrogen gas, carbon oxide, hydrocarbon compounds, etc. contained in the waste gas, converting all hydrogen into water and all carbon into carbon dioxide. This waste gas is then sent to one moisture recovery mechanism 106h to recover moisture, and one carbon dioxide recovery mechanism 112.
It is absorbed and recovered in the carbon dioxide absorption liquid by a. Therefore, 3H contained in the waste gas is 3H20, 'H'HO
14c is concentrated and recovered in the water recovered by the moisture recovery mechanism 106* in the form of O, and 14c is concentrated and recovered in the carbon dioxide absorption liquid in the form of 14co2. After a certain amount of waste gas has flowed, one moisture recovery mechanism 106a and one carbon dioxide recovery mechanism 1 are shown in FIG. 3(b).
12a inlet valves 109h, 114a and outlet valve 111
m, 117a and the other moisture recovery mechanism 1.
06b and the other carbon dioxide recovery mechanism 112b (D inlet valves 109b, 114b and outlet valves 111b, 117
b is opened to allow the brittle gas to flow into the other moisture recovery mechanism 106b and the other carbon dioxide recovery mechanism 112b. During this time, the front and rear connectors 121° 121 of one moisture recovery mechanism 106h and one carbon dioxide recovery mechanism 112a are connected.
．． 121, 121 are separated, one of the moisture recovery mechanism 106a and the carbon dioxide recovery mechanism 112a is removed from the pipe, and the radiation dose of the water and carbon dioxide absorption liquid recovered inside is measured using a scintillation counter. Based on the results, the concentration of 3H,140 in the waste gas will be measured and monitored down to the extremely low concentration range. And the above operation 1
0- Repeat the operation to remove one moisture recovery mechanism 1θ6a, one carbon dioxide recovery mechanism 112a, and the other moisture recovery mechanism 10.
6b and the other carbon dioxide recovery mechanism 112b are used alternately to continuously measure the concentration of 3H and 14C in the waste gas,
Monitor. And this one is the moisture recovery mechanism 106a,
106b and carbon dioxide recovery mechanisms 112a, 112b
can be removed from the pipe line, so that relatively high concentrations of 3H and 14C are contained in the waste gas.
If a and 112b become radioactively contaminated, they can be replaced with another one and installed without affecting subsequent measurements. Note that the contaminated moisture recovery mechanisms 106a and 106b and the carbon dioxide recovery mechanism 112a
, 112b can be decontaminated and reused. Also,
Since this embodiment is equipped with an oxidation mechanism 101, all hydrogen and carbon contained in the waste gas in a form other than water and carbon dioxide, that is, hydrogen gas, carbon oxide, hydrocarbon compounds, etc., are removed by water. It can also be recovered as carbon dioxide, improving measurement accuracy. Also, a carbon dioxide recovery mechanism 112a.

The waste gas passing through 112b contains the vapor of the carbon dioxide absorption liquid, and this carbon dioxide absorption liquid is generally toxic, but in this embodiment, the absorption liquid recovery mechanism 118a
+'118b recovers the vapor of this carbon dioxide absorption liquid, thus preventing the surrounding environment from being contaminated by this vapor.

Note that the present invention is not limited to the first embodiment described above.

For example, FIG. 4 shows a second embodiment of the invention. This second embodiment has carbon dioxide recovery mechanisms 112a and 112b.
The waste gas discharged from the outlet pipe 116 is introduced into the rare gas concentration mechanism 122 to remove 85Kr contained in the waste gas.
Separate and concentrate radioactive rare gases such as This rare gas concentrating mechanism 122 permeates waste gas through a gas permeable membrane and separates and concentrates the contained rare gas, and the separated and concentrated rare gas is detected by radiation through a rare gas pipe 123. vessel 124
The radioactive rare gas concentration in the waste gas is measured and monitored based on the results, and the remaining waste gas from which the rare gas has been separated is discharged through the exhaust pipe 125. It is composed of Further, 126 is a waste gas dilution mechanism which opens stop valves 127 and 128 when the concentration of radioactive rare gas in the waste gas is high and exceeds the measurement range of the radiation detector 124. Gas supply source 12
9 to the rare gas concentration mechanism 122 via the flow rate adjustment valve 130.
Alternatively, the carrier gas is supplied upstream of the radiation detector 124 to dilute the waste gas or the separated and concentrated rare gas, thereby reducing the concentration of the radioactive rare gas to within the measurement range of the radiation detector 124. There is. Note that this second embodiment has the same configuration as the first embodiment except for the above points,
In FIG. 4, parts corresponding to those in the first embodiment are designated by the same reference numerals, and their explanation will be omitted. The second embodiment can also measure and monitor the concentration of radioactive rare gases other than 5H and 14c. In addition, in the case of the second embodiment, if the vapor of the carbon dioxide absorption liquid mixed into the waste gas in the carbon dioxide recovery mechanisms 13-112a and 112b flows into the rare gas concentrating mechanism 122, the performance of the gas permeable membrane will deteriorate. However, since the vapor of this carbon dioxide absorption liquid is recovered by the absorption liquid recovery mechanisms 118m and 118b, the above-mentioned problem does not occur.

Furthermore, the present invention is not limited to the above embodiments.

For example, the number of moisture recovery mechanisms and carbon dioxide recovery mechanisms is not necessarily limited to two each, and three or more may be provided.

Further, the oxidation mechanism, absorption liquid recovery mechanism, and mechanism for measuring the concentration of radioactive rare gas do not necessarily need to be provided.

As described above, the present invention provides a plurality of water recovery mechanisms and carbon dioxide recovery mechanisms in parallel, and a large mouth valve and an outlet valve are provided on the inlet and outlet sides of the water recovery mechanisms and carbon dioxide recovery mechanisms. Separable connectors are provided on the inlet and outlet sides, respectively.

14- By selectively opening and closing the large mouth valve and outlet valve, the plurality of moisture recovery mechanisms and carbon dioxide recovery mechanisms are operated one by one, and the moisture recovery mechanisms and carbon dioxide recovery mechanisms that are not in operation are By separating the connector and removing it from the pipe line, and measuring the radiation dose of the recovered water and carbon dioxide, the concentration of radionuclides such as AH and 14C in the waste gas can be continuously measured and monitored down to extremely low concentrations. Even if the moisture recovery mechanism and carbon dioxide recovery mechanism become radioactively contaminated due to high concentrations of 3U and 14C being impregnated in the waste gas, we can remove them from the pipes and create a new moisture recovery mechanism and a carbon dioxide recovery mechanism that are not radioactively contaminated. Since it can be replaced with a carbon dioxide recovery mechanism, it does not affect subsequent measurement accuracy, and its effects are outstanding, such as being able to measure and monitor the concentration of radionuclides in waste gas with high precision and reliability.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a conventional example, and FIG. 2 is a schematic configuration diagram of another conventional example. FIGS. 3(a) and 3(b) are schematic diagrams of the first embodiment of the present invention showing different operating states. FIG. 4 is a schematic diagram of a second embodiment of the present invention. 101... Oxidation mechanism, 105... Inlet pipe, 106a
. 106b...moisture recovery mechanism, 109a, 1θ9b...
・Inlet valve, 110 ... Outlet pipe, 111th, 1ll
b-- Outlet valve, 112h, 112b- Carbon dioxide recovery mechanism, 113... Inlet pipe, 114h, 114b...
Inlet valve, 116... Outlet pipe, 117a, 117b...
Outlet valve, 11'8a, 118b... Absorption liquid recovery mechanism, 121... Connector. Applicant's representative Patent attorney Takehiko Suzue Continued from page 1 0 Inventor Hideaki Hioki, Japan Atomic Energy Corporation, 3-13-12 Mita, Minato-ku, Tokyo Applicant: Sendai Type Ichiban, Tohoku Electric Power Co., Ltd. 3-7-3, Machi ■Applicant Chubu Electric Power Co., Ltd. 1 Higashishinmachi, Higashi-ku, Nagoya ■Applicant Chugoku Electric Power Co., Ltd. 4-33 Komachi, Naka-ku, Hiroshima ■Applicant Japan Atomic Power Co., Ltd. Tokyo 1-6-1 Otemachi, Chiyoda-ku ■Applicant: Tokyo Shibaura Electric Co., Ltd. 72, Horikawa-cho, Saiwai-ku, Kawasaki City ■Applicant: Japan Atomic Energy Corporation, 417-3-13-12, Mita, Minato-ku, Tokyo

Claims (1)

[Scope of Claims] (1) A plurality of moisture recovery mechanisms installed in parallel with each other to recover water in radioactive waste gas, and carbon dioxide in the radioactive waste gas that is installed in parallel with each other and passes through the moisture recovery mechanisms. a plurality of carbon dioxide recovery mechanisms for recovering carbon; large mouth valves and outlet valves provided on the inlet and outlet sides of the moisture recovery mechanism and carbon dioxide recovery mechanism, respectively; and inlets of the moisture recovery mechanism and carbon dioxide recovery mechanism. and a separable connector provided between the inlet valve and the outlet of the moisture recovery mechanism and the carbon dioxide recovery mechanism and the outlet valve, respectively. (2) An oxidation mechanism is provided upstream of the water recovery mechanism to oxidize hydrogen, -carbon oxide, and hydrocarbon bed compounds contained in the radioactive waste gas to produce water and carbon dioxide. Patented monitoring device. (3) An absorption liquid recovery device for recovering vapor of the carbon dioxide absorption liquid used in the carbon dioxide recovery mechanism is provided downstream of the carbon dioxide recovery mechanism. The radioactive waste gas monitoring device according to item 1.