CN111613349A - Device and method for removing trace gas based on fluid self-oscillation and micro-interface strengthening - Google Patents

Abstract

The invention provides a trace gas removal device based on fluid self-oscillation and micro-interface enhancement, including a venturi micro-bubble generating device, a fluid oscillator, a reaction kettle and a gas-liquid separation device; the bottom end of the gas-liquid separation device is provided with a cutting The bottom flow port is provided with a tangential inlet on the side and an overflow pipe on the top; the side of the reaction kettle is provided with a tangential outlet, and the top is provided with a gas-liquid mixture inlet; the bottom of the venturi micro-bubble generating device is communicated with the molten salt circuit, The top is connected to the bottom of the fluid oscillator; the top of the fluid oscillator is connected to the bottom of the reactor; the gas-liquid mixture inlet at the top of the reactor is communicated with the overflow pipe; the tangential inlet on the side of the gas-liquid separation device is connected to the tangential inlet of the reactor. Connect to the outlet; the tangential underflow port at the bottom end communicates with the molten salt circuit. The trace gas removal device of the invention can effectively remove the fission gases krypton, xenon, etc. in the molten salt circuit of the molten salt reactor, reduce neutron loss, reduce equipment maintenance costs, and significantly improve the economic benefits of the molten salt reactor.

Description

Device and method for removing trace gas based on fluid self-oscillation and micro-interface strengthening

technical field

The invention relates to the technical field of fission gas removal, in particular, to a trace gas removal device and a removal method, in particular, to a trace gas removal device and removal method based on fluid self-oscillation and micro-interface strengthening technology method.

Background technique

Thorium-based nuclear energy has the characteristics of good neutron breeding performance, less high-level waste and abundant reserves. As one of the candidate reactors of the fourth generation advanced reactor, the molten salt reactor has the advantages of efficient utilization of thorium, high-temperature hydrogen production, water-free cooling, suitable for Advantages and potentials such as small modular design. However, a large amount of gaseous neutron poisons such as xenon and krypton will be produced during the reaction of the molten salt reactor, which not only hinders the chain reaction of the molten salt reactor, but also causes great harm to the pipeline equipment. Since the neutron poison is slightly soluble in the fuel salt and exists in the form of tiny bubbles, the United States proposes a mode of infusing the bubbles first, so that the fission gas diffuses into the bubbles, and then separates. In view of the characteristics of small bubbles and high viscosity of the molten salt medium in the molten salt reactor circuit, the international mainstream adopts the cyclone separation method to remove neutron poisons.

Cyclone separation technology is a high-efficiency separation technology that utilizes centrifugal force and two-phase density difference to achieve multi-phase separation. However, the specific separation conditions of cyclone separation technology are harsh, and there are certain requirements for the back pressure of the separator.

After searching the prior art, in the article "Working Characteristics of Cyclone Gas-Liquid Separator under Different Back Pressures" published in the journal "Nuclear Technology", Li Hua et al. disclosed a degassing system suitable for molten salt reactors. The cyclone gas-liquid separator, the separation condition of the separator is mainly to control the back pressure, and the robust performance is not good.

SUMMARY OF THE INVENTION

In view of the defects in the prior art, the purpose of the present invention is to provide a trace gas removal device and method based on fluid self-oscillation and micro-interface enhancement.

The purpose of this invention is to realize through the following scheme:

A first aspect of the present invention provides a trace gas removal device based on fluid self-oscillation and micro-interface enhancement, including a venturi micro-bubble generating device, a fluid oscillator, a reaction kettle and a gas-liquid separation device; The bottom end is provided with a tangential underflow port, the side is provided with a tangential inlet, and the top is provided with an overflow pipe; the side of the reaction kettle is provided with a tangential outlet, and the top is provided with a gas-liquid mixture inlet; the venturi microbubbles are formed The bottom of the device is connected to the molten salt circuit, the top is connected to the bottom of the fluid oscillator, and the middle of the venturi microbubble generating device is also provided with a gas injection hole; the top of the fluid oscillator is connected to the reactor of the reactor. the bottom end; the gas-liquid mixture inlet at the top of the reaction kettle is communicated with the overflow pipe at the top of the gas-liquid separation device; the tangential inlet on the side of the gas-liquid separation device is connected with the tangential outlet on the side of the reaction kettle; The tangential underflow port at the bottom end of the gas-liquid separation device is communicated with the molten salt circuit.

Preferably, the fluid oscillator includes an inlet tapered section, a diffusion cavity, a guide boss and an outlet diffusion section, the top of the venturi microbubble generating device is connected to the inlet tapered section, and the inlet is tapered The diffuser section is connected with the diffusion chamber, the guide boss is placed in the diffusion chamber, the diffusion chamber is connected with the outlet diffusion section, and the outlet diffusion section is communicated with the bottom end of the reaction kettle.

Preferably, the reaction kettle includes a gradually expanding section and a straight cylinder cavity from bottom to top, a tangential outlet is set on the side of the straight cylinder cavity, and a gas-liquid mixture inlet is set on the top of the straight cylinder cavity; the expanding section and the fluid The outlet diffuser of the oscillator is connected.

Preferably, the diffusion angle of the gradually expanding section is consistent with the diffusion angle of the outlet diffusion section.

Preferably, the gas-liquid separation device is a centrifugal columnar gas-liquid separator, comprising an overflow pipe with an inner diameter of D1 arranged from top to bottom, a length of L1, a large-diameter straight cylindrical cavity with an inner diameter of D2, and a large-diameter cylindrical cavity with a length of L2. The tapered cavity and the small-diameter straight cylindrical cavity with a length of L3 and a diameter of D3, the side of the large-diameter straight cylindrical cavity is provided with a tangential inlet with a tangential angle of α, and the bottom end side wall of the small-diameter straight cylindrical cavity is provided with an inner diameter of α. For the tangential underflow port of D4, one end of the overflow pipe is partially inserted into the large-diameter straight cylindrical cavity, and the other end is connected to the gas-liquid mixture inlet of the reactor.

Preferably, the inner bottom of the small diameter straight cylinder cavity is provided with a conical flow stabilizer with an apex angle of β.

Preferably, the apex angle β of the conical flow stabilizer is 30°.

Preferably, the inner diameter D1 of the overflow pipe is 40-50mm, the length L1 of the large-diameter straight cylinder cavity is 600mm, the inner diameter D2 is 96-150mm, and the tangential angle α of the tangential inlet is 24°-30° , the length L2 of the tapered cavity is 300-675mm, the length L3 of the small diameter straight cylinder cavity is 50-75mm, the inner diameter D3 is 64-100mm, and the inner diameter D4 of the tangential underflow port is 40-50mm.

The second aspect of the present invention provides a trace gas removal method, which adopts the above-mentioned trace gas removal device based on fluid self-oscillation and micro-interface enhancement, and specifically includes the following steps:

S1, pass the molten salt carrying the fission gas into the venturi microbubble generating device, and the carrier gas is injected through the gas injection hole of the venturi microbubble generating device;

S2. The molten salt and carrier gas loaded with fission gas enter the flow channel of the fluid oscillator from the Venturi microbubble generating device, and due to the Coanda effect, an oscillating jet will be generated to realize the fluid self-oscillation;

S3. The molten salt and the carrier gas carrying the fission gas enter the reaction kettle from the fluid oscillator. In the reaction kettle, the turbidity of the fluid is strengthened to speed up the mass transfer efficiency, so that the carrier gas can fully absorb the fission gas, and the molten salt forms an entrained microbe bubbly flow of bubbles;

S4. The bubbly flow of molten salt entrained with micro-bubbles enters the tangential inlet of the centrifugal columnar gas-liquid separator on the side and then forms a swirling flow around the cavity. Due to the difference in gas-liquid density, different gravity and centrifugal force are generated, thereby forming a gas core. The overflow pipe from the upper part returns to the reaction kettle, and the molten salt after removing the fission gas returns to the molten salt circuit from the tangential bottom flow port.

Further, the fission gas to be removed is krypton and xenon.

Compared with the prior art, the present invention has the following beneficial effects: the centrifugal separator does not have such a disadvantage, so the centrifugal separator is considered to replace the existing cyclone separation technology.

1. The trace gas removal device of the present invention can effectively remove the fission gas krypton, xenon, etc. in the molten salt circuit of the molten salt reactor, reduce neutron loss, reduce equipment maintenance costs, and significantly improve the economic benefits of the molten salt reactor.

2. The trace gas removal device of the present invention adopts the combination of a fluid oscillator and a reaction kettle for mass transfer. Due to the self-oscillation of the fluid, the fluid can be fully turbid without using a stirrer, thereby enhancing the mass transfer efficiency.

3. The trace gas removal device of the present invention adopts a centrifugal columnar gas-liquid separator, which changes the shortcomings of the traditional cyclone separator, which has harsh separation conditions and high requirements for back pressure, and has good robust performance.

4. The trace gas removal device of the present invention adopts the integrated design of the mass transfer device and the separator, which greatly reduces the floor space of the equipment and provides the possibility for the small modular design of the molten salt reactor.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

1 is a perspective view of a trace gas removal device of the present invention;

Fig. 2 is a schematic diagram of the structure of the trace gas removal device of the present invention;

Fig. 3 is the perspective view of the micro-bubble generation device of Chinese Churi micro-bubble generation device of the trace gas removal device of the present invention;

Fig. 4 is the perspective view of the micro-bubble generation device of Chinese Churi micro-bubble of the trace gas removal device of the present invention;

5 is a perspective view of a fluid oscillator in the trace gas removal device of the present invention;

Fig. 6 is the front view of Fig. 5;

Fig. 7 is the front view of the reactor in the trace gas removal device of the present invention;

Fig. 8 is the perspective view of the reactor in the trace gas removal device of the present invention;

9 is a schematic structural diagram of a centrifugal columnar gas-liquid separator in the trace gas removal device of the present invention;

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the inventive concept. These all belong to the protection scope of the present invention.

During the operation of the molten salt reactor, a large amount of gaseous neutron poisons such as xenon and krypton will be produced, which will endanger the safety and efficiency of the reactor. Therefore, it is necessary to separate the fission gas products online. In view of the high viscosity of liquid molten salt medium of molten salt reactor and the tiny bubbles in the primary circuit, an online primary circuit removal device including a venturi microbubble generator, fluid oscillator, reactor and centrifugal columnar gas-liquid separator is designed. gas device. The molten salt entrained with micro-bubbles enters the overall device. The Venturi micro-bubble generating device, fluid oscillator and reaction kettle adsorb the fission gas on the carrier gas, and pass through the inlet section of the centrifugal columnar gas-liquid separator in its column. A swirling flow is formed, a low pressure area is formed in the center of the cylinder, so that the bubbles gather to the center, and are led out of the separator from the upper overflow port, and the molten salt along the wall of the cylinder is led out from the bottom flow port of the separator and returned to the molten salt circuit to complete the gas-liquid separation.

As shown in FIG. 1 to FIG. 9 , the present invention will be further described in detail below with reference to specific embodiments.

Example 1

A trace gas removal device based on fluid self-oscillation and micro-interface strengthening, comprising a venturi micro-bubble generating device 1, a fluid oscillator 2, a reactor 3 and a gas-liquid separation device 4; the bottom end of the gas-liquid separation device 4 A tangential bottom flow port 41 is provided, and a tangential inlet 42 is provided on the side. The tangential inlet is conducive to the flow of fluid along the wall to form a swirl, and the top is provided with an overflow pipe 43; the side of the reaction kettle 3 is provided with a tangential outlet 31 , the top is provided with a gas-liquid mixture inlet 32; the bottom of the venturi microbubble generating device 1 is connected with the molten salt circuit, the top is connected with the bottom of the fluid oscillator 2, and the middle of the venturi microbubble generating device 1 There is also a gas injection hole 11; the top of the fluid oscillator 2 is connected to the bottom end of the reactor 3; the gas-liquid mixture inlet 32 at the top of the reactor 3 and the overflow at the top of the gas-liquid separation device 4 The pipe 43 is connected; the tangential inlet 42 on the side of the gas-liquid separation device 4 is connected with the tangential outlet 31 on the side of the reaction kettle 3; the tangential bottom flow port 41 at the bottom end of the gas-liquid separation device 4 is communicated with the molten salt circuit .

The specific structures of the venturi microbubble generating device 1, the fluid oscillator 2, the reaction kettle 3 and the gas-liquid separation device 4 are as follows:

The venturi microbubble generating device 1 includes from bottom to top: an inlet straight pipe section 12, a constricted section 13, a cylindrical throat 14, an expansion section 15, an outlet straight pipe section 16 and six parts of the gas injection hole 11 in the throat, the gas injection hole 11 Connect with an external gas source and introduce nitrogen as a carrier gas into the Venturi tube. Preferably, a dissolved oxygen detector is installed in front of the venturi tube for detecting the oxygen concentration.

The fluid oscillator 2 includes an inlet tapered section 21, a diffusion cavity 22, a guide boss 23 and an outlet diffusion section 24. The top of the venturi microbubble generating device 1 is connected to the inlet tapered section 21, so The inlet tapered section 21 is connected to the diffusion cavity 22, the guide boss 23 is placed in the diffusion cavity 22, the diffusion cavity 22 is connected to the outlet diffusion section 24, and the outlet diffusion section 24 communicates with the bottom end of the reactor 3 .

The reaction kettle 3 includes a gradually expanding section 33 and a straight cylinder cavity 34 from bottom to top, a tangential outlet 31 is set on the side of the straight cylinder cavity 34, and a gas-liquid mixture inlet 32 is set on the top of the straight cylinder cavity 34; 33 communicates with the outlet diffusion section 24 of the fluid oscillator 2 .

The gas-liquid separation device 4 is a centrifugal columnar gas-liquid separator, including an overflow pipe 43 with an inner diameter of D1 arranged from top to bottom, a length of L1, a large-diameter straight cylindrical cavity 44 with an inner diameter of D2, and a large-diameter cylindrical cavity 44 with an inner diameter of D2. The tapered cavity 45 and the small diameter straight cylindrical cavity 46 with a length of L3 and a diameter of D3, the side of the large diameter straight cylindrical cavity 44 is provided with a tangential inlet 42 with a tangential angle α, and the bottom end side of the small diameter straight cylindrical cavity 46 The wall is provided with a tangential underflow port 41 with an inner diameter of D4, one end of the overflow pipe 43 is partially inserted into the large-diameter straight cylindrical cavity 44, and the other end is connected to the gas-liquid mixture inlet of the reactor 3. 32 connections. Wherein, the inner diameter D1 of the overflow pipe 43 is 50mm, the length L1 of the large-diameter straight cylindrical cavity 44 is 600mm, the inner diameter D2 is 150mm, the tangential angle α of the tangential inlet 42 is 27°, and a tangential direction is provided. The angle can better form a swirl flow and enhance the separation effect. The length L2 of the tapered cavity 45 is 675mm, the length L3 of the small diameter straight cylinder cavity 46 is 75mm, and the inner diameter D3 is 100mm. The inner diameter D4 is 50mm.

Example 2

Embodiment 2 is a preferred example of Embodiment 1.

In Embodiment 2, the diffusion angles of the gradually expanding section 33 and the outlet diffusion section 24 are the same, and the inner bottom of the small diameter straight cylindrical cavity 46 is provided with a conical flow stabilizer 47 with an apex angle β=30° to stabilize The flow device can better form the gas core in the gas-liquid separation device. Others are the same as those in Embodiment 1.

Example 3

Embodiment 3 is an application example of Embodiment 1 or Embodiment 2.

The method for removing trace gas using the above-mentioned trace gas removal device based on fluid self-oscillation and micro-interface enhancement specifically includes the following steps:

S1, pass the molten salt loaded with fission gas into the venturi microbubble generating device 1, and the carrier gas is injected by the gas injection hole 11 of the venturi microbubble generating device through a circulating pump; the fission gas that needs to be removed is krypton ,xenon.

S2, the molten salt and carrier gas carrying the fission gas enter the flow channel of the fluid oscillator 2 from the venturi microbubble generating device 1, and due to the Coanda effect, an oscillating jet will be generated to realize the fluid self-oscillation;

S3, the molten salt and the carrier gas carrying the fission gas enter the reactor 3 from the fluid oscillator 2. In the reactor 3, the fluid is turbid and the mass transfer efficiency is accelerated, so that the carrier gas can fully absorb the fission gas and the molten salt Formation of a bubbly flow with entrained microbubbles;

S4. The bubbly flow of molten salt entrained with micro-bubbles enters the tangential inlet of the centrifugal columnar gas-liquid separator on the side and then forms a swirling flow around the cavity. Due to the difference in gas-liquid density, different gravity and centrifugal force are generated, thereby forming a gas core. Return to the reaction kettle 2 from the overflow pipe 43 at the upper part, and the molten salt after removing the fission gas returns to the molten salt circuit from the tangential bottom flow port 41 .

In order to test the operation of the loop and verify the separation effect, the following experiments are designed:

Specifically, the gas fission products to be removed are replaced with oxygen, and the carrier gas argon in the molten salt reactor is replaced with nitrogen. After the oxygen is dyed with the resazurin reagent, it is photographed and analyzed by the high-speed camera, so as to facilitate the observation of the oxygen distribution. After the oxygen concentration is detected by the dissolved oxygen detector, the gas removal efficiency is determined by comparing the change of the oxygen concentration before and after the fluid passes through the oscillator, the reactor and the separation device.

Specifically, the oscillating jet will be generated due to the Coanda effect when the distilled water and the carrier gas nitrogen carrying "fission gas" oxygen pass through the flow channel of the fluid oscillator, and the turbidity of the fluid will be strengthened when passing through the reactor, and the mass transfer efficiency will be accelerated. Nitrogen carrier gas fully absorbs oxygen.

Specifically, the bubble-like flow of distilled water entrained with micro-bubbles enters the tangential inlet on the side of the centrifugal columnar gas-liquid separator and then forms a swirling flow around the cavity. Different gravitational and centrifugal forces are generated due to the difference in gas-liquid density, thereby forming a gas core. Return to the reactor from the upper overflow port, and the distilled water after degassing returns to the circulation pump from the bottom flow port to form a loop circulation.

In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", The orientation or positional relationship indicated by "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying the indicated device. Or elements must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as a limitation of the present application.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essential content of the present invention. The embodiments of the present application and features in the embodiments may be arbitrarily combined with each other without conflict.

Claims (10)

1. A micro gas removing device based on fluid self-oscillation and micro-interface strengthening is characterized by comprising a Venturi micro-bubble generating device (1), a fluid oscillator (2), a reaction kettle (3) and a gas-liquid separating device (4);

the bottom end of the gas-liquid separation device (4) is provided with a tangential underflow port (41), the side surface is provided with a tangential inlet (42), and the top end is provided with an overflow pipe (43);

a tangential outlet (31) is arranged on the side surface of the reaction kettle (3), and a gas-liquid mixture inlet (32) is arranged at the top of the reaction kettle;

the bottom of the Venturi microbubble generation device (1) is communicated with the molten salt loop, the top of the Venturi microbubble generation device is connected with the bottom of the fluid oscillator (2), and the middle of the Venturi microbubble generation device (1) is also provided with a gas injection hole (11);

the top of the fluid oscillator (2) is connected to the bottom end of the reaction kettle (3); a gas-liquid mixture inlet (32) at the top end of the reaction kettle (3) is communicated with an overflow pipe (43) at the top end of the gas-liquid separation device (4); a tangential inlet (42) on the side surface of the gas-liquid separation device (4) is connected with a tangential outlet (31) on the side surface of the reaction kettle (3); and a tangential underflow port (41) at the bottom end of the gas-liquid separation device (4) is communicated with the molten salt loop.

2. The micro-gas removal device based on fluid self-oscillation and micro-interface strengthening as claimed in claim 1, wherein the fluid oscillator (2) comprises an inlet tapered section (21), a diffusion cavity (22), a flow guiding boss (23) and an outlet diffusion section (24), the top of the venturi micro-bubble generation device (1) is connected to the inlet tapered section (21), the inlet tapered section (21) is connected to the diffusion cavity (22), the flow guiding boss (23) is disposed in the diffusion cavity (22), the diffusion cavity (22) is connected to the outlet diffusion section (24), and the outlet diffusion section (24) is communicated to the bottom end of the reaction kettle (3).

3. The micro-gas removal device based on fluid self-oscillation and micro-interface strengthening as claimed in claim 1 or 2, wherein the reaction kettle (3) comprises a divergent section (33) and a straight cylindrical cavity (34) from bottom to top, a tangential outlet (31) is arranged on the side surface of the straight cylindrical cavity (34), and a gas-liquid mixture inlet (32) is arranged on the top of the straight cylindrical cavity (34); the divergent section (33) communicates with an outlet divergent section (24) of the fluidic oscillator (2).

4. The micro gas removal device based on self-oscillation of fluid and micro interface strengthening according to claim 3, wherein the divergent section (33) is in accordance with the diffusion angle of the outlet divergent section (24).

5. The micro-gas removal device based on fluid self-oscillation and micro-interface strengthening according to claim 1, wherein the gas-liquid separation device (4) is a centrifugal cylindrical gas-liquid separator, and comprises an overflow pipe (43) with an inner diameter of D1, a large-diameter straight cylindrical cavity (44) with a length of L1 and an inner diameter of D2, a tapered cavity (45) with a length of L2 and a small-diameter straight cylindrical cavity (46) with a length of L3 and a diameter of D3, which are arranged from top to bottom, the side surface of the large-diameter straight cylindrical cavity (44) is provided with a tangential inlet (42) with a tangential angle of alpha, the bottom end side wall of the small-diameter straight cylindrical cavity (46) is provided with a tangential underflow port (41) with an inner diameter of D4, one end of a circular pipe section of the overflow pipe (43) is partially inserted into the large-diameter straight cylindrical cavity (44), and the other end of the overflow pipe is connected with the inlet (32) of the gas-.

6. The micro-gas removal device based on self-oscillation of fluid and micro-interface strengthening according to claim 5, characterized in that the bottom of the small diameter straight cylinder cavity (46) is provided with a conical flow stabilizer (47) with a vertex angle β.

7. Micro gas removal device based on fluidic self-oscillation and micro-interface strengthening according to claim 6, characterized in that the conical flow stabilizer (47) has a vertex angle β of 30 °.

8. The micro-gas removal device based on fluid self-oscillation and micro-interface intensification as claimed in claim 5, wherein the inner diameter D1 of the overflow pipe (43) is 40-50mm, the length L1 of the large-diameter straight cylinder cavity (44) is 600mm, the inner diameter D2 is 96-150mm, the tangential angle α of the tangential inlet (42) is 24-30 °, the length L2 of the tapered cavity (45) is 300-675mm, the length L3 of the small-diameter straight cylinder cavity (46) is 50-75mm, the inner diameter D3 is 64-100mm, and the inner diameter D4 of the tangential underflow port (41) is 40-50 mm.

9. A trace gas removal method, which is characterized by adopting the trace gas removal device based on fluid self-oscillation and micro-interface strengthening as claimed in any one of claims 1 to 8, and comprises the following steps:

s1, introducing the molten salt carrying the fission gas into the Venturi microbubble generation device (1), and injecting the carrier gas through a gas injection hole (11) of the Venturi microbubble generation device;

s2, enabling molten salt carrying fission gas and carrier gas to enter a flow channel of the fluid oscillator (2) from the Venturi microbubble generation device (1), and generating oscillation jet flow due to the wall attachment effect to realize self oscillation of the fluid;

s3, enabling the molten salt carrying the fission gas and the carrier gas to enter a reaction kettle (3) from the fluid oscillator (2), and in the reaction kettle (3), enhancing the turbidness of the fluid to enable the carrier gas to fully absorb the fission gas, so that the molten salt forms bubble-shaped flow carrying micro bubbles;

s4, enabling the bubbly flow of the molten salt carrying the micro bubbles to enter a tangential inlet on the side face of the centrifugal columnar gas-liquid separator and then form a rotational flow around the cavity, generating different gravity and centrifugal force due to gas-liquid density difference, further forming a gas core, returning the gas core to the reaction kettle (3) from the upper part of the overflow pipe (43), and returning the molten salt subjected to fission gas removal to a molten salt loop from the tangential underflow port (41).

10. A trace gas removal method as claimed in claim 9, wherein said fission gas to be removed is krypton or xenon.

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