JPH03296695A - Condensing apparatus of rare gas - Google Patents

Abstract

PURPOSE:To attain an increase in a rising speed in a heating mode, reduction in a temperature difference in an apparatus and an improvement in temperature controllability and to improve an adsorptive condensation performance by providing a heat-insulating vessel into which a pressurized gas supply pipe and a liquid nitrogen discharge pipe are inserted. CONSTITUTION:A double-cylinder-shaped heat-insulating vessel 4 has a heat-insulating material 4c under a cap 4d constructed of a inner cylinder 4a and an outer cylinder 4b. A gas introduction pipe 6 is connected to an active adsorption bed 5 in this vessel 4. A gas outflow pipe 8 is connected onto the outlet side of the adsorption bed 5, while the introduction pipe 6 and the outflow pipe 8 pierce the cap 4d and are connected to a tank outside the vessel 4. A spray nozzle 11 disposed in the vessel 4 is connected to a liquid nitrogen supply system C. Moreover, a heater 12 inserted into the vessel 4 is connected to a controller 14 to which a signal of a thermocouple 13 provided for the adsorption bed 15 is inputted. Piercing the cap 4d, a nitrogen gas outlet pipe 15, a pressurized gas supply pipe 16 and a liquid nitrogen discharge pipe 17 are inserted into the vessel 4. The supply pipe 16 is connected to a nitrogen gas supply system E, while the outlet pipe and the discharge pipe 17 are connected to an exhaust system D.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention is a method for detecting low concentration rare gases, which are used in, for example, a lagging method failure fuel detection device of a fast breeder reactor (FBR), using activated carbon. The present invention relates to a rare gas concentrator suitable for a device that condenses by cold adsorption and analyzes its components.

(Prior art) A damaged fuel detection device using the lagging method seals tag gas into the fuel rods of a nuclear fuel assembly placed in the reactor core as a mark indicating the address of the nuclear fuel assembly, and when a fuel rod is damaged, Tag gas leaks from the damaged area and mixes with the cover gas, so by analyzing the tag gas components in the cover gas, it is possible to detect which fuel rod address is damaged. The cover gas is an inert gas such as argon gas filled in the cover gas space covering the surface of the liquid sodium coolant for cooling the core.

In addition, rare gases such as xenon and krypton and their isotopes are used as tag gases.

A conventional tagging method-based damaged fuel detection device and its rare gas concentrator will be described with reference to FIGS. 10 to 12. In Figure 1, × indicates the valve is open, H indicates the valve is closed, and
indicates a state in which the valve is repeatedly opened and closed. Also, 啼 indicates the flow of cover gas containing tag gas, and → indicates the flow of liquid nitrogen.

That is, as shown in Figure 1O, the cover gas containing the tag gas is transferred from the reactor cover gas system A to the second stage noble gas concentrator [1 (in the figure, two units are arranged, so la,
lb, one unit is on standby). In FIG. 10, B indicates a waste gas treatment system, C indicates a liquid nitrogen supply system, and D indicates an exhaust system, and the flow of gas, etc. to each system is indicated by the arrow direction.

In this first stage rare gas concentrator 1a, liquid nitrogen is supplied from the liquid nitrogen supply system C and cooled, and the rare gas is cryopreserved by a cryoadsorption method using activated carbon.

The cryogenic adsorption method is a method in which low concentration tag gases, such as rare gas isotopes such as xenon and krypton, contained in the cover gas are adsorbed and concentrated on activated carbon at a cryogenic temperature of about -180°C.

The cover gas containing the tag gas adsorbed in the first stage noble gas concentrator 1a is heated to about 150°C and desorbed, and the
As shown in the figure, it is transferred to the second stage rare gas concentrator w2. Also in the second stage rare gas concentrator 2, the liquid nitrogen supply system C
Liquid nitrogen is supplied from the reactor and cooled, and the noble gas is again cryogenically adsorbed and concentrated using the cryogenic adsorption method using activated carbon. After that, the temperature is raised to about -80°C to selectively desorb and separate only the cover gas, and then heated to about 150°C to desorb the tag gas. The tag gas is sent to the analyzer 13, and the exhaust gas is sent to the exhaust system. It will be done. This analyzer 3 analyzes the components of the tag gas, that is, rare gas isotopes. Based on the analysis results, it is possible to determine which address in the core the fuel rod is damaged. After analysis, the tag gas is transferred to waste gas treatment system B.
is discharged to.

In this way, the tag gas concentration is concentrated to a concentration that can be analyzed by the activated carbon cryogenic adsorption and selective separation of the cover gas in the first stage rare gas concentrator 1 and the second stage rare gas concentrator 2. In step 3, the components of the tag gas are analyzed to detect the location of fuel damage within the reactor core.

Next, the structure of the rare gas concentrator will be explained with reference to FIG.

Although the first and second stage rare gas concentrators 1 and 2 differ in size, they are structurally the same.

The main body of the rare gas concentrator is an insulated container 4 with a vacuum double structure consisting of an inner cylinder 4a and an outer cylinder 4b, and the upper opening in this insulated container 4 is hermetically closed with a lid 4d fitted with a heat insulating material 4C. . Furthermore, an activated carbon adsorption bed 5 filled with activated carbon is disposed inside the heat insulating container 4. Activated carbon adsorption bed 5
Gas inlet pipe 6. A heat exchanger tube 7 and a gas outlet tube 8 are connected. The cover gas containing the tag gas flows in from the gas introduction pipe 6, passes through the heat transfer pipe 7, and is introduced into the activated carbon adsorption bed 5.
The tag gas is adsorbed on activated carbon. The cover gas from which the tag gas has been removed flows out from the gas outflow pipe 8.

Next, the temperature control system for the activated carbon adsorption bed 5 will be explained.

Liquid nitrogen is used as the cooling medium, and liquid nitrogen supply system C
Liquid nitrogen is supplied through a supply valve 9 and a connecting pipe 10, and is ejected from a spray nozzle 11 above the activated carbon adsorption bed 5.

As the heating medium, a plurality of electric heaters 12 inserted around the sides of the activated carbon adsorption bed 5 are used. Activated carbon adsorption bed 5
A thermocouple 13 is attached to the thermocouple 13.
The controller 14 outputs the opening/closing signal of the valve 9 and the output signal of the electric heater 12, adjusts the supply amount of liquid nitrogen and the output of the electric heater 12, and controls the temperature of the activated carbon adsorption bed 5. . Most of the liquid nitrogen supplied by the eruption is vaporized in the rare gas concentrator, becomes nitrogen gas, and is discharged from the nitrogen gas outlet pipe 15 to the exhaust system.

(Problems to be Solved by the Invention) First, as mentioned above, the sprayed liquid nitrogen becomes atmospheric and is released into the exhaust system as nitrogen gas, but at -180°C
During the operation mode in which the rare gas concentrator is controlled to an extremely low temperature, a portion of the supplied liquid nitrogen remains at the bottom of the rare gas concentrator without being vaporized.

This is because when the activated carbon adsorption bed is stably controlled at -180°C for a long period of time, the temperature at the bottom drops to -196°C at once, and liquid nitrogen accumulates because the difference in temperature from -196°C of liquid nitrogen is small. If liquid nitrogen accumulates, the temperature will be more stable,
Furthermore, the frequency of opening and closing of the valve 9 is reduced, which is preferable in terms of control.

However, when moving to the next operating mode, that is, heating mode, this residual liquid nitrogen adversely affects temperature control. That is, at the same time as the temperature rise is slowed down, the temperature difference between the lower part and the upper part of the rare gas concentrator increases, and temperature controllability deteriorates.

In FIG. 12, the heating mode is heating by an electric heater 12. In FIG. In this case, natural convection occurs within the rare gas concentrator. However, since there is no means for forcibly stirring the inside, a temperature difference of several tens of degrees Celsius occurs inside.

Further, an overshoot of 20 to 30°C occurs when the temperature reaches -80°C and 150°C.

This temperature difference, or overshoot, results in temperature variations and excess temperatures within the activated carbon adsorption bed 5.

This temperature control system applies the temperature dependence of adsorption performance of activated carbon, and temperature controllability is an important issue in terms of the performance of this system.

To solve this problem, a device can be considered that intermittently jets liquid nitrogen from a spray nozzle during heating mode to stir the inside of the rare gas concentrator to equalize the temperature and suppress overshoot. However, this device has problems such as a slow heating rate and a temporary temperature drop.

The present invention has been made in order to solve the above problems, and has means for discharging residual liquid nitrogen when transitioning from cooling mode to heating mode, and utilizes bracket means to drain the inside of the apparatus during heating mode. An object of the present invention is to provide a rare gas concentrator that can make the temperature uniform.

[Structure of the invention]

(Means for Solving the Problems) In the present invention, an activated carbon adsorption bed through which a gas to be treated containing a rare gas flows in and out is housed in an insulated container, and the activated carbon adsorption bed has a spray nozzle on the top and a heating heater on the side. is placed,
The inlet side of the spray nozzle is connected to the liquid nitrogen supply system via a supply valve, and the discharge nozzle for the nitrogen gas vaporized in the insulated container is provided at the upper part of the insulated container and connected to the exhaust system, and the activated carbon A detection control system having a thermocouple and a controller for measuring the temperature in the adsorption bed is provided, and the controller is connected to the supply valve and the heater by a signal line. is provided with a pressurized gas supply pipe and a liquid nitrogen discharge pipe inserted to the bottom of the container, the pressurized gas supply pipe is connected to the pressurized gas supply system via a valve, and the liquid nitrogen discharge pipe is connected to the pressurized gas supply system through a valve. It is characterized by being connected to an exhaust system or a storage container.

(Function) When switching to the heating mode, the downstream valve of the nitrogen gas outlet pipe is closed, the pressurized gas supply system valve is opened, and the inside of the rare gas concentrator is pressurized with nitrogen gas pressure to reduce the liquid by the siphon effect. Exhaust the nitrogen through the liquid nitrogen exhaust pipe into the exhaust system. The required nitrogen gas pressure varies depending on the connection conditions with the exhaust system, but
~3 kg/J is sufficient.

In the heating mode, the valve downstream of the nitrogen gas outlet pipe is opened, and nitrogen gas is intermittently supplied from the pressurized gas supply pipe to stir the inside of the rare gas concentrator and equalize the temperature.

(Example) A first example of the rare gas concentrator according to the present invention will be described with reference to FIGS. 1 to 4.

In FIG. 1, reference numeral 4 denotes a double cylindrical heat-insulating container having a heat insulating material 4c at the bottom of a lid 4d consisting of an inner cylinder 4a and an outer cylinder 4b, and an activated adsorption bed 5 is disposed within this heat-insulating container 4. , to this activated carbon adsorption bed 5, a gas introduction pipe 6 is connected to a heat transfer pipe 7.
connected via. A gas outflow pipe 8 is connected to the outlet side of the activated carbon adsorption bed 5, and the gas introduction pipe 6 and the gas outflow pipe 8 are connected to respective tanks (not shown) outside the heat insulating container 4 by passing through the lid 4d. ing. Further, a spray nozzle 11 is arranged inside the heat insulating container 4, and this spray nozzle 11 is connected to the liquid nitrogen supply system C via a supply valve 9 and a connecting pipe 10. Furthermore, a heater 12 is inserted into the heat insulating container 4, and the heater 12 is connected to a controller 14 which inputs a signal from a thermocouple 13 provided in the activated carbon adsorption bed 5.

A nitrogen gas outlet pipe 15 passes through the lid 4d. A pressurized gas supply pipe 16 and a liquid nitrogen discharge pipe 17 are inserted into the heat insulating container 4. The pressurized gas supply pipe 16 is connected to the connecting pipe 19 and the valve 1.
8 to a nitrogen gas supply system E as a pressurized gas supply system. The nitrogen gas outlet pipe 15 is connected to an exhaust system via a connecting pipe 21 and a valve 22. The liquid nitrogen discharge pipe 17 is connected to an exhaust system via a connecting pipe 20. Note that the connecting pipe 20 is provided with a heater 23, and the reference numeral 24 in the drawing indicates liquid nitrogen.

Next, the effects of the above embodiment will be explained with reference to FIGS. 1 to 4.

In the figure, ← indicates the flow of liquid nitrogen, ke indicates the flow of nitrogen gas, × indicates the valve is open, -ne indicates the valve is closed, and H indicates the state in which the valve is repeatedly opened and closed intermittently. .

Figure 2 shows the cooling mode. In this case, the valve 22 is open;
Valve 18 is in the closed state, and valve 9 is opened and closed to control the supply of liquid nitrogen to control the temperature of the activated carbon adsorption bed at -180°C. In this case, the liquid nitrogen 24 that remains without being vaporized is shown in FIG. The vaporized nitrogen gas is discharged from the nitrogen gas outlet pipe 15 to the exhaust system.

Next, FIG. 3 shows the transition to the heating mode.

In this case, valves 9 and 22 are closed, valve 18 is opened, and pressurized nitrogen gas is supplied from nitrogen gas supply system E as a pressurized gas supply system, so that the inside of the rare gas concentrator is supplied with nitrogen gas pressure. Apply pressure.

The residual liquid nitrogen 24 is pushed out by the nitrogen gas pressure and is pushed out from the liquid nitrogen discharge pipe 17 by the siphon effect, and is transferred to the connecting pipe 20.
It is heated by an electric heater 23 installed in the tank, vaporizes it, and discharges it to the exhaust system.

FIG. 4 shows the heating mode.

The valve 22 is opened, the valve 18 is opened and closed intermittently, and nitrogen gas is supplied to forcibly stir the inside of the rare gas concentrator to equalize the temperature.

In addition, when it is necessary to increase the cooling effect in the mode of preventing overshoot and controlling the temperature to -80° C., the valve 9 can be opened and closed to supply liquid nitrogen at the same time.

Note that nitrogen gas is used as the pressurized gas in this embodiment. This is because nitrogen gas is supplied at room temperature, which is sufficiently higher than the liquid nitrogen temperature of -196°C, so that in the short term, the nitrogen gas will not condense and no pressure will be applied. Helium gas may be used to ensure functionality.

According to the above embodiment, by pushing out and discharging the liquid nitrogen remaining in the rare gas concentrator at the time of transition to the heating mode, the temperature rise during the heating mode can be accelerated, and the temperature inside the device can be increased. Temperature difference can be reduced.

Since the inside of the apparatus can be stirred during the heating mode, the temperature difference within the apparatus can be further reduced.

Thus, the temperature controllability in the heating mode is improved, and the adsorption concentration performance of this system, which emphasizes the temperature-dependent adsorption performance of activated carbon, is improved.

Next, other embodiments of the present invention will be described with reference to FIGS. 5 to 9. Figures 5 to 9 show changes in operating modes.

The heat insulating container in this embodiment is the same as the structure inside the heat insulating container 4 shown in FIGS. 1 to 4, so its explanation will be omitted.

This embodiment differs from the previous embodiment in that the exhaust system is removed, a liquid nitrogen recovery container 25 is provided in its place, and a liquid nitrogen discharge pipe 17 is connected to the liquid nitrogen recovery container 25. In order to explain the function of the recovery container 25, the relationship between each of the first and second stage rare gas concentrators 1 and 2 and the recovery container 25 is shown in FIGS. 5 to 9. In addition, in the figure, the first stage device is marked with a, and the second stage device is marked with b to distinguish them. The liquid nitrogen discharge pipe 17 (17a, 17b) is connected to the recovery container 25 via the valve 26 (26a, 26b).

Further, it branches from the connecting pipe 21 (21a, 21b) of the nitrogen gas outlet pipe 15 (15a, 15b), and connects to the valve 2.
7 (27a, 27b), and the nitrogen gas supply system E and the recovery container 25 are connected via a valve 28 and a connecting pipe 29. Furthermore, the liquid nitrogen discharge pipe 30 inserted to the bottom of the recovery container 25 is connected to the valve 31 (3
1a, 31b) to the liquid nitrogen supply pipe 32 (32a, 32b) of the rare gas concentrator.

FIG. 5 shows both the first-stage rare gas concentrator 1 and the second-stage rare gas concentrator 2 in the cooling mode. In this case, both valves 15a and 15b are open, and valves 22a and 22b are open.
The temperature is controlled at -180° C. by supplying liquid nitrogen, and the vaporized nitrogen gas is supplied to the nitrogen gas outlet pipe 150a.

15b to the exhaust system.

FIG. 6 shows a case where the first stage rare gas concentrator 1 shifts to the heating mode. The second stage rare gas concentrator 2 is in cooling mode. In this case, valves 18a and 26a are opened and valve 9a is opened.
, 22a is closed, the residual liquid nitrogen in the first stage rare gas concentrator is pushed out by nitrogen gas pressure, and the recovery container 25 is closed.
Excrete inside. In this case, the pressure inside the recovery container 25 is a slight negative pressure due to the connection to the exhaust system. Further, since the gas in the recovery container 25 is released to the exhaust system, liquid nitrogen 33 flows into the recovery container 25.

FIG. 7 shows the heating mode of the first-stage rare gas concentrator 11, and shows the case where the second-stage rare gas concentrator 2 shifts to the heating mode. The first stage noble gas concentrator 1 has valves 9a and 18a.
Nitrogen gas (liquid nitrogen if necessary) is supplied intermittently by opening and closing. The inside of the chamber M1 is forcibly stirred, and nitrogen gas is discharged from the nitrogen gas outlet pipe 15a to the exhaust system. On the other hand, the second stage noble gas concentrator 2 has valves 18b and 26.
b is opened, and with valves 9b and 22b closed, residual liquid nitrogen is pushed out into the recovery container 25 by the pressure of nitrogen gas.

The liquid nitrogen 3 accumulated in the recovery container 25 during the above process
3 is used at the start of cooling of the rare gas concentrator in the next process of FIGS. 8 and 9. FIG. 8 shows the start of cooling of the first stage rare gas concentrator 1, and the second stage rare gas concentrator 12 is in the heating mode. In this case, the valve 28.31a is opened, the recovery container 25 is pressurized with nitrogen gas, the liquid nitrogen 33 is pushed out, and the liquid nitrogen 33 is supplied via the connecting pipe 3o valve 31a and the connecting pipe 32a, and the first stage noble gas concentrator 1 is shown.

FIG. 9 shows a case where the liquid nitrogen 33 in the recovery container 25 is supplied to cool the second stage rare gas concentrator 2 when it starts cooling.

In this embodiment, residual liquid nitrogen is heated and vaporized by an electric heater and discharged into the exhaust system. In this case, there is a possibility that liquid nitrogen or nitrogen gas will flow back due to pressure increase due to vaporization, and it is necessary to provide a backflow prevention device. In other embodiments, the liquid nitrogen is stored and reused as it is without being vaporized, so there is no possibility of backflow, and the liquid nitrogen can be used effectively and energy can be saved.

[Effects of the Invention] According to the present invention, the liquid nitrogen remaining in the rare gas concentrator during the cooling mode is discharged to the outside of the device at the start of the heating mode, thereby increasing the rising speed during the heating mode and reducing the temperature difference within the device. can be reduced, temperature controllability can be improved, and adsorption concentration performance can be improved.

Furthermore, the liquid nitrogen discharge means forcibly stirs the inside of the apparatus during the heating mode, thereby further reducing the temperature difference within the apparatus.

By storing the discharged residual liquid nitrogen in a recovery container and reusing it when starting the cooling mode, the liquid nitrogen can be used effectively and the loss of thermal energy in the system is improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing an embodiment of the rare gas concentrator according to the present invention, and FIGS. A schematic system diagram for explaining the operation in mode, FIGS. 5 to 9 are schematic system diagrams for explaining the operation in other embodiments of the present invention, and FIGS. 10 and 11 are for the lagging method. FIG. 12 is a schematic system diagram for explaining a damaged fuel inspection device according to the present invention, and FIG. 12 is a vertical cross-sectional view showing a conventional rare gas concentrator. A... Reactor cover gas system B waste gas treatment system C.
...Liquid nitrogen supply system D...Exhaust system E...Nitrogen gas supply system 1...First stage rare gas concentrator 2...Second stage rare gas concentrator 3...Analyzer 4. ...Insulating container 5...Activated carbon adsorption bed 6...Gas inlet pipe 7...Heat transfer tube 8...Gas outlet pipe 9...Supply valve 10.19, 20, 21, 29, 30, 32 ... Connection pipe 11 ... Spray nozzle 12, 23 ...
Heater 13... Thermocouple 14... Controller 15... Nitrogen gas outlet pipe 16... Pressurized gas supply pipe 17... Liquid nitrogen discharge pipe 18,2
2, 26, 27, 28, 31...Valve 24.33...
Liquid nitrogen 25...Recovery container (8733)
Agent Patent Attorney Yoshiaki Inomata (and 1 other person) Figure 7 Figure 7

Claims (1)

[Claims] An activated carbon adsorption bed through which a gas to be treated containing a rare gas flows in and out is housed in a heat insulating container, a spray nozzle is placed above the activated carbon adsorption bed, a heater is placed on the side, and a liquid is placed on the inlet side of the spray nozzle. It is connected to a nitrogen supply system via a supply valve, and a discharge nozzle for the nitrogen gas vaporized in the insulated container is provided at the upper part of the insulated container and connected to an exhaust system to measure the temperature in the activated carbon adsorption bed. In the rare gas concentrator, a detection control system having a thermocouple and a controller is provided, and the controller is connected to the supply valve and the heater by a signal line. A liquid nitrogen exhaust pipe inserted to the bottom of the container is provided, the pressurized gas supply pipe is connected to the pressurized gas supply system via a valve, and the liquid nitrogen exhaust pipe is connected to the exhaust system or the storage container. A rare gas concentrator characterized by: