JPS6060598A - Radioactive gas waste treater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to radioactive gaseous waste treatment equipment.

[Technical background of the invention and its problems] In general, in a rising water type nuclear power plant, radioactive gases such as N2.02, Xe, Kr, etc. accumulated in the main condenser are extracted and the radioactivity is sufficiently removed. Radioactive gaseous waste disposal equipment is provided for the purpose of attenuation and release into the atmosphere.

In this system, activated carbon selectively adsorbs and desorbs ×8 gas and Kr gas in the exhaust gas, so that Xs gas and l(r gas pass through the activated carbon layer at a very slow speed compared to the overall flow of exhaust gas. Taking advantage of this fact, an activated carbon diluted gas-hold up tower is installed to sufficiently attenuate Xe and Kr, which have a longer half-life than N2.02.

The residence time of this Xs gas, l(r gas in the activated carbon layer is
It is greatly influenced by the temperature of the activated carbon layer and the relative humidity of the exhaust gas. In order to increase the residence time, it is necessary to lower the temperature of the activated carbon layer and, in particular, to lower the humidity of the exhaust gas. For this reason, the temperature inside the activated carbon rare gas hold up tower is adjusted to around 20℃ at high temperatures.
Additionally, a dryer is installed upstream of the activated carbon rare gas hold up tower to reduce the humidity of the exhaust gas.
The exhaust gas is cooled to 20 to -30°C to freeze moisture in the exhaust gas and remove -C.

At this time, if the dryer is operated for a long time, frost will build up inside the dryer, impeding the cooling effect and causing a large pressure loss, so it is necessary to install multiple dryers and switch them as needed. It is necessary to carry out defrosting.

In other words, consider an operation mode in which, for example, three dryers are installed, one for cooling operation, one for defrosting, and one as a backup to dry exhaust gas continuously. There is a need.

FIG. 1 is a piping system diagram showing the dryer and activated carbon rare gas hold up tower in a conventional radioactive gas waste treatment equipment. It shows. Dryer 1a, 1
b, 1c have on-off valves 2.b and 1c on their respective upstream and downstream sides.
It has 3.

In such a radioactive gas waste treatment equipment, during normal operation, for example, among the three dryers 1a, 1b, and 1C, only the dryer 1a is in operation, and the dryer 1b is in the process of defrosting and drying. The dryer 1G is on standby in case the dryer 1a is unable to maintain sufficient capacity due to some abnormality. In Fig. 0, dryers 1b and Ic have on-off valves 2.3 disposed upstream and downstream thereof closed, and are separated from the system by η.
1 has been done.

In the radioactive gas waste treatment apparatus configured as described above, the drain water after being defrosted is supplied to the dryer 1a.

After flowing into the drain trap 4 from the lower part of 1b and 1c, it is discharged from the drain 5.

That is, in the dryer 1b during the defrosting operation, the ice that has adhered to the surface of the heat transfer tube in the dryer 1b (=J) is warmed by an ice melting device (not shown) disposed in the dryer 1b, It becomes water and flows into the drain trap 4. At this time, the dryer 1
Inside b is saturated with water vapor generated at the same time, and the internal temperature is about 50°C.

Since the ice melting device described above is stopped after a certain period of time, the temperature inside the dryer 1b decreases to the ambient environment temperature, and the temperature inside the dryer 1b decreases to the ambient temperature.
Accordingly, the water vapor in the dryer 1b condenses and adheres to the wall surface of the dryer 1b, and the remaining water vapor remains in the dryer 1b.

Activated carbon rare gas hold up towers 6a, 6b.

6C is arranged in series on the downstream side of these three dryers 1a, 1b, and 1c. Now, the inside of the dryer 1c, which is currently on standby, is in a state where the frost (c) deposited during the previous operation has been removed by the defrosting operation.

Therefore, the dryer 1c is filled with humid exhaust gas,
Water droplets that have not been completely dropped adhere to the cooling fins and the wire mesh for separating the floating mist at the outlet of the dryer 10. Therefore, if cooling operation is started immediately, it will take some time for the main body of the dryer 10 to be cooled and the exhaust gas and water droplets inside to be frozen. On the other hand, the inflowing exhaust gas is not sufficiently dried and flows out into the downstream activated carbon rare gas holding up tower 6a. This has a very negative effect on the adsorption performance of activated carbon - 0 there C1 dryer 1C
Before starting the cooling operation, a precooling operation is performed for several minutes.

However, since such precooling operation is performed with the on-off valves 2 and 3 closed, there is a possibility that some parts may not be sufficiently cooled. The moisture adhering to this part 92 The water vapor accumulated in the dryer 1C flows out as soon as the exhaust air 7J flows in, and the temperature does not drop sufficiently (-11,'1). There is white exhaust gas coming out of the dryer 1C.

Furthermore, before the dryer 1C enters the pre-cooling operation, it is conceivable that some abnormality occurs in the dryer 1a and an emergency switch is made to the dryer 1C.

As a countermeasure, it is possible to keep the dryer 1C in a pre-cooling state, but it is economically problematic to perform a pre-cooling operation in order to deal with a small abnormal switching with a probability of non-7:(. Also, there is a technical problem in operating the dryer 1C for a long time with zero heat load.

Therefore, it is unreasonable to constantly operate the dryer 1C in pre-cooling mode.

In such a case, a considerably larger amount of water will flow out from the dryer 1c than when switching from the normal dryer 1a to the dryer 1c described above. It is conceivable that excess moisture is contained in the exhaust gas and flows into the activated carbon layer in this way, but in these cases it is thought that the relative humidity will naturally be high.

However, the operator diagram for activated carbon is as shown in FIG. 2, and as is clear from the diagram, the water adsorption ffi by activated carbon increases rapidly when the relative humidity exceeds 40%. That is, the adsorption performance for Xe and Kr decreases accordingly.

In other words, the dryers ia, ib, and 1c are originally installed to lower this relative humidity, and in such radioactive gas waste treatment equipment, it is necessary to minimize the inflow of moisture when switching them. Measures are required to do so.

[Object of the invention] The present invention has been made in response to such conventional circumstances, and
It is an object of the present invention to provide a radioactive gas waste processing apparatus that can suppress as much as possible the inflow of moisture into a rare gas hold up tower when switching dryers.

[Summary of the Invention] That is, the present invention includes dryers arranged in parallel to dry radioactive gas, and a dryer arranged downstream of these dryers via an open valve to dry radioactive gas from the dryer. A radioactive gas waste treatment apparatus equipped with a diluted gas hold up tower for attenuating radioactivity, characterized in that a drain pipe disposed in the dryer C1 is connected to a container maintained in a negative pressure state. This is a radioactive gas waste treatment equipment.

[Embodiment of the Invention] The details of the present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 2 shows a radioactive gas waste treatment apparatus according to an embodiment of the present invention, and in the figure, the symbols 'C'@ia, ib, and 1c indicate dryers arranged in parallel.

Inlet pipes 2a, 2b, 2c are arranged on the inlet sides of the dryers 1a, 11), 'l, respectively, and on-off valves 3a13b, 3c are inserted into the inlet pipes 2a, 2b, 2c. There is. In addition, outlet pipes 4a, 4b, and 4G are arranged on the outlet sides of the dryers 1a, 1b, and 1c, and on-off valves 5a, 5b, and 5c are inserted into these outlet pipes 4a, 14b, and 4c, respectively. There is. The outlet pipes 4a, 4b, and 4c meet at one point and are connected to rare gas hold up towers 5a, 5b, and 16C. A drain pipe is connected to each of the dryers 1a and 1b11C, and these drain pipes w7a% 71), 7
Opening/closing valves 8a, 81+, and 8c are inserted in each of the opening and closing valves 8a, 81+, and 8c. And these drain arrangements k 8 a , 8
b N 8 C merges at one point and is connected to the main condenser 9.

That is, in the radioactive gas waste treatment apparatus configured as described above, when the dryer 1a is in operation, the on-off valve 8a is closed.
is automatically closed. That is, at this time, all the water in the dryer 1a is frozen, and the dryer 1a
Since no condensate is generated from the tank, the on-off valve 8a is closed and no problem occurs in C. At this time, the on-off valves 8b and 8c of the dryers lb and ic are open during defrosting or standby.

That is, the drain, air, steam, etc. of these dryers 1b, 1c flow out to the main condenser 9, and the dryers 1b, 1c
There is a vacuum inside.

That is, in the radioactive gas waste treatment equipment configured as described above, the inside of the main condenser 9 is normally maintained at a vacuum state of about 7301 m HQ.
The inside of 1C is also in a vacuum state of almost the same degree. At this time, the saturation temperature of water vapor in the dryers 1b and 1C is 35°C.
The water droplets on the surface of the heat transfer tubes can be evaporated by raising the temperature inside the dryer 1b11C to about 50° C. by operating the ice melting device of the defrost 11N for a certain period of time.

In reality, the structures of the dryers 1a, 1b and IC are extremely complex, and all moisture must be removed by
Since it takes a long time to operate the ice-melting station, it is desirable to continue operating it within a practical range.

That is, in the radioactive gas waste treatment apparatus configured as described above, it is possible to minimize the moisture flowing into the rare gas hold up towers 6a, 16b, 6C from the dryers 1a, 1b, 1c, and Hold up tower 6a,
It is possible to improve the efficiency of 6b and 6c. Furthermore, since the drain from the dryers 1a, 1b, and 1C is returned to the main condenser 9 and reused, it is also economically advantageous.

FIG. 4 shows another embodiment of the present invention, in which drain piping 10 from the dryers 1a, 1b, 1C opens into a drain tank 1.

A pipe 17 is opened in this drain tank 11 and connected upstream of a precooler 14a114b in which on-off valves 12 and 13 are respectively inserted upstream and downstream. In the figure, reference numeral 815 indicates a drain wrap, and reference numeral 1G indicates a pump.

That is, in the radioactive gas waste processing apparatus configured as described above, for example, during the defrosting operation of the dryer 1b,
The water vapor generated in B flows into the C drain tank 11 via the on-off valve 8b, and then is guided from the drain tank 11 through the pipe 17 to the upstream side of the pre-7ε devices 14a and 14b.
Precooler 14. After being cooled in steps a and 14b, it is guided to the dryer 1a.

In other words, in such radioactive gas waste treatment equipment,
Since the system is operated under negative pressure, when water vapor is generated in the dryer 1b, the internal J and t forces increase, and as a result,
A pressure gradient may be created to create the above-described flow. As a result, it is possible to prevent water vapor from condensing on the inner wall as residual moisture in the dryer 1b, thereby preventing the rare gas hold up tower 6a.

It is possible to suppress moisture from flowing into 6b and 6c.

[Effects of the Invention] As described above, according to the radioactive gas waste treatment apparatus of the present invention, the amount of moisture flowing into the diluted gas hold up tower from the dryer can be suppressed to a minimum.

[Brief explanation of drawings]

Figure 1 is a piping system diagram that does not show a conventional radioactive gas waste treatment equipment, Figure 2 is a graph showing the relationship between relative humidity and activated carbon adsorption amount, and Figure 3 is a diagram of the radioactive gas waste treatment equipment of the present invention. FIG. 4 is a piping system diagram showing another embodiment of the radioactive gas waste treatment apparatus of the present invention. 1a 11b, 1c - Dryer 6a, 6b, 6c... Rare Cas Bold Up" 6
9・・・・・・・・・・・・・・・・・・・・・・・・
Main condenser 11・・・・・・・・・・・・・・・・・・
...Drain tanks 14a, 14b...
..., Hiroshi Suyama, patent attorney representing the precooler - Figure 1 Relative excursion (%) Figure 3

Claims (2)

[Claims] (1) Dryers arranged in parallel to dry radioactive gases, and dryers arranged downstream of these dryers via on-off valves to attenuate the radioactivity of the radioactive gases from the dryers. A radioactive gas waste treatment apparatus comprising a gas hold up tower, characterized in that a drain pipe disposed in the dryer is connected to a container maintained in a negative pressure state. . (2) The radioactive gas waste treatment apparatus according to claim 1, wherein the container is a main condenser C. 3) The radioactive gas waste treatment apparatus according to claim 1, wherein the container is a drain tank.