High-temperature melt pump, and high-temperature melt pump system

Abstract

The objective of the present invention is to provide a technology for achieving a high-temperature melt pump that can be used in devices requiring a high-temperature melt to be circulated, and that is more economical and practical.　This high-temperature melt pump is a pump for transporting a fuel salt (10) within a pipe (15) in a predetermined direction, and comprises: the pipe (15); a plurality of fluid diodes (16) provided midway along the pipe (15); a pump main body container (7) which is connected to the pipe (15) and which is filled with a cover gas (17) that comes into contact with the fuel salt (10); and a gas vibration generating device (12) for transmitting vibrations to the fuel salt (10) in the pump main body container (7) by way of the cover gas (17).

Description

High-temperature melt pumps and high-temperature melt pump systems

[0001] The present invention relates to a high temperature melt pump and a high temperature melt pump system.

[0002] Patent Document 1 below discloses a technique for a sodium pump used in a fast reactor.

[0003] Japanese Patent Application Publication No. 4-219476

[0004] In devices that use molten salt or molten metal (hereinafter, high-temperature liquids other than molten salt and molten metal are referred to as "high-temperature melt") as a coolant to transport heat or cool nuclear reactors, such as nuclear fusion reactors, molten salt reactors, and molten metal-cooled fast reactors, a pump for circulating the high-temperature melt (hereinafter, referred to as "high-temperature melt pump") is required. A high-temperature melt pump must be able to transport extremely high-temperature melt at a certain flow rate or above, have a seal structure that prevents leakage of the high-temperature melt and cover gas inside the high-temperature melt pump, and be able to accommodate regular maintenance. Therefore, it is quite difficult to develop a high-temperature melt pump that can achieve the required performance.

[0005] The most common type of high-temperature melt pump is a turbo-type pump, such as a centrifugal pump or mixed-flow pump, which uses an impeller to transport high-temperature melt. These pumps are used as high-temperature melt pumps in the Molten Salt Experimental Reactor (MSRE) at Oak Ridge National Laboratory and as sodium pumps in the fast reactors Joyo and Monju. Although bearings are essential for the shaft that rotates the impeller, considerable ingenuity is required to design a bearing system that functions stably in high-temperature environments and to design seals to prevent leakage of the high-temperature melt and cover gas inside the high-temperature melt pump. Furthermore, because the motor that rotates the shaft stops functioning at high temperatures, the shaft must either be significantly longer or a special cooling system must be considered.

[0006] Regarding the bearing problem, the MSRE uses ball bearings and an oil lubricant that also serves as a coolant. However, there have been problems with this oil contaminating the fuel salt. While oil contamination may be acceptable in an experimental reactor that operates for only about four years, it is difficult to tolerate in a commercial reactor that must operate for several decades or more.

[0007] On the other hand, the lower bearings in Joyo and Monju, which are immersed in liquid sodium, use fluid bearings that use this liquid sodium as a lubricant. In fast reactors, liquid sodium is used only as a coolant, so there is little chance of impurities being mixed in, and this does not pose any particular problems, but in molten salt reactors, rare earths and rare metals, which are fission products, are present in the molten salt. These fission products can precipitate and damage the bearings, making it inappropriate to use fluid bearings.

[0008] When fluid bearings are not available, ceramic bearings or magnetic bearings are the options, but ceramic bearings have the problem of wear on the sliding parts, making them unsuitable for long-term stable operation. Magnetic bearings, on the other hand, solve the problem of friction, but because they use magnetic force for bearing, they cannot be used in high-temperature environments above 200°C. In order to use magnetic bearings, they must be cooled to below 200°C.

[0009] The motor that drives the impeller is also magnetically driven, so there are very few products that can be used in high temperature environments above 200°C. Therefore, it is essential to design a motor that can be cooled to below 200°C.

[0010] A high-temperature melt pump that can solve the above problems and meet the required conditions would necessarily have an extremely complex structure. To cool the driving devices such as bearings and motors, the shaft connecting the impeller, which comes into direct contact with the high-temperature melt, to the driving device would need to be quite long; Monju requires a shaft length of about 7 m, and Joyo requires a shaft length of about 5 m.

[0011] Such a high-temperature melt pump with a complex structure is difficult to maintain and poses various problems in terms of economy and practicality.

[0012] To solve these problems, a fundamental shift in thinking is required: how can we create a high-temperature melt pump that does not require any moving parts inside the pump, has a simple structure, and can be operated almost maintenance-free?

[0013] The present invention has been made in consideration of the above circumstances, and aims to provide technology for realizing a high-temperature melt pump that is more economical and practical and can be used in devices that require the circulation of high-temperature melt.

[0014] To achieve the above objective, the high-temperature melt pump of the present invention employs a reciprocating positive displacement pump similar to a piston pump or diaphragm pump. In these reciprocating positive displacement pumps, a piston or diaphragm reciprocates to transport the liquid. Because reciprocating positive displacement pumps alternately draw and discharge the liquid, they are equipped with a fluid diode as a mechanism for transporting the liquid in a predetermined direction, similar to a typical reciprocating positive displacement pump. However, in typical reciprocating positive displacement pumps, the piston or diaphragm is in direct contact with the liquid. However, while diaphragms are not available in materials suitable for high-temperature liquids such as high-temperature melts, and the sliding parts of pistons function similarly to fluid bearings, problems similar to those of turbopumps arise in molten salt reactors. Furthermore, because the piston drive device (e.g., a motor) is connected to the piston, problems with motor operation at high temperatures similar to those of the turbopump described above arise. Therefore, in the present invention, instead of directly transporting the high-temperature melt by the reciprocating motion of the piston, the piston generates a reciprocating motion of a cover gas, which is then transferred to the high-temperature melt, generating a motion that alternates between drawing and discharging the high-temperature melt, thereby achieving the same functionality as a typical reciprocating positive displacement pump. Since the piston is a device that generates reciprocating motion of the cover gas, it does not necessarily have to be placed near the high-temperature melt, can be easily cooled, and various methods can be selected for the bearing mechanism of the piston sliding part. Therefore, one aspect of the present invention is a high-temperature melt pump that transports high-temperature melt in a pipe in a predetermined direction, characterized in that it comprises: the pipe, a plurality of fluid diodes provided midway along the pipe, a pump main container to which the pipe is connected and which contains a cover gas that comes into contact with the high-temperature melt, and a gas vibration generator that transmits vibrations to the high-temperature melt in the pump main container via the cover gas.

[0015] According to the present invention, it is possible to provide a technology for realizing a high-temperature melt pump that is more economical and practical and can be used in devices that require the circulation of high-temperature melt.

[0016] Fig. 6 is a configuration diagram showing an example of a high-temperature melt pump and a high-temperature melt pump system of the present invention. Fig. 7 is an enlarged view of the high-temperature melt pump of Fig. 1. Fig. 8 is an enlarged cross-sectional view of a Tesla valve, which is an example of the fluid diode of Fig. 2. Fig. 9 is a diagram showing an example of the transition of oscillating pressure in a gas vibration generator that drives pistons by a triple eccentric mechanism of Fig. 1. Fig. 10 is a diagram showing an example of the transition of pump transport volume in the pump main body of Fig. 1. Fig. 11 is a diagram showing an example of the transition of oscillating pressure in a gas vibration generator that drives pistons by a double cam mechanism instead of the triple eccentric mechanism of Fig. 1. Fig. 6 is a diagram showing an example of the transition of pump transport volume in the pump main body when the gas vibration generator assumed in Fig. 6 is used.

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following description is merely an example, and the technical scope of the present invention is not limited thereto. FIG. 1 is a configuration diagram showing an example of a high-temperature melt pump and a high-temperature melt pump system according to this embodiment. In this embodiment, a molten salt reactor plant will be used as an example for the following description. Note that the present invention is not limited to molten salt reactor plants. The present invention can also be applied to nuclear fusion reactors, fast reactors, and the like. The present invention can also be applied to, for example, solar thermal power generation systems that use molten salt to store solar heat, and material manufacturing plants that use high-temperature melts.

[0018] <Regarding the Molten Salt Reactor Plant> The molten salt reactor plant shown in Figure 1 is composed of a containment vessel 1, a molten salt reactor 2 (reactor) enclosed by this containment vessel 1, a drain tank (not shown) also enclosed by the containment vessel 1, a high-temperature melt pumping system 3, a heat exchanger 4, and piping 6 connecting the core 5 of the molten salt reactor 2 and the heat exchanger 4.

[0019] In a molten salt reactor plant, when fuel salt 10, which will be described later, flows into the core 5 of the molten salt reactor 2, a nuclear fission reaction occurs, and the thermal energy generated by the nuclear fission reaction is extracted via the heat exchanger 4. The extracted thermal energy is then converted into rotational energy, which is then converted into electrical energy by a generator to generate electricity.

[0020] The heat exchanger 4 is provided to transfer thermal energy generated by the nuclear fission reaction to the cooling salt of the secondary loop. The high-temperature melt pump system 3 is provided to forcibly convect the fuel salt 10, which will be described later. The heat exchanger 4 is connected to the piping of the secondary loop through which the cooling salt flows.

[0021] <Regarding the high-temperature melt pump system 3> The high-temperature melt pump system 3 will be described with reference to Figures 1 and 2. As mentioned above, Figure 1 is a configuration diagram showing an example of a high-temperature melt pump, a high-temperature melt pump system, and a nuclear reactor plant according to the present invention, and Figure 2 is an enlarged view of the high-temperature melt pump in Figure 1.

[0022] Such a high-temperature melt pump system 3 includes a plurality of high-temperature melt pumps (FIG. 1 shows an example of three pumps, and FIG. 2 shows a single high-temperature melt pump), a drive control device 8, and a pulsation adjustment device 9. The high-temperature melt pump system 3 functions between the molten salt reactor 2 and the heat exchanger 4, and transports fuel salt 10 in a direction from the molten salt reactor 2 toward the heat exchanger 4.

[0023] <Regarding the High-Temperature Melt Pump> The high-temperature melt pump is mainly composed of a pump body 11 and a gas vibration generator 12. The high-temperature melt pump also includes a pulsation adjustment device 9 as needed. In the high-temperature melt pump, the pump body 11 is disposed inside the containment vessel 1, and the gas vibration generator 12 is disposed outside the containment vessel 1. In an example of use as a thorium molten salt reactor, the temperature of the cover gas 13 filled inside the containment vessel 1 is maintained at approximately 500°C, and the temperature of the external environment 14 outside the containment vessel 1 is assumed to be, for example, 100°C or lower.

[0024] [Regarding the pump body 11] The pump body 11 includes a pipe 15, a fluid diode 16, and a pump body container 7 in which a fuel salt 10 is held and a cover gas 17 is sealed. The pump body 11 is connected to the gas vibration generator 12 via a pipe 19. Note that, although the pump body 11 is shown in FIG. 1 as being located between the molten salt reactor 2 and the containment vessel 1, the position of the pump body 11 is not particularly limited to that shown in FIG. 1.

[0025] [Regarding the piping 15] The piping 15 is composed of a first piping 151 on the upstream side and a second piping 152 on the downstream side. One end of the first piping 151, i.e., an upstream piping end 151a, is connected to the top of the molten salt reactor 2. The other end 151b of the first piping 151 is arranged inside the pump main vessel 7. Continuing the explanation based on the state shown in Figures 1 and 2, the first piping 151 extends straight upward from the upstream piping end 151a, makes a U-turn at the top of the pump main vessel 7, and enters the inside of the pump main vessel 7. The other end 151b of the first piping 151 is arranged at the bottom inside the pump main vessel 7. A fluid diode 16 is provided midway along the first piping 151, on the side of the other end 151b.

[0026] One end 152a of the second pipe 152 is arranged at the bottom inside the pump main container 7. The one end 152a is arranged at a position lower than the other end 151b of the first pipe 151. The second pipe 152 extends straight upward from the one end 152a, makes a U-turn at the top position of the pump main container 7, and is then drawn out to the outside of the pump main container 7. A fluid diode 16 is provided midway along the second pipe 152 drawn out to the outside of the pump main container 7. The other end of the second pipe 152, which is a downstream pipe end 152b, is connected to the heat exchanger 4 via the pulsation adjustment device 9.

[0027] [Regarding the fluid diode 16] The fluid diode 16 will be described with reference to Fig. 3. Fig. 3 is an example of an enlarged cross-sectional view of the fluid diode of Fig. 1 and Fig. 2. Fig. 1 and Fig. 2 will also be referenced as necessary.

[0028] The fluid diode 16 allows the fuel salt 10 to flow in a predetermined direction. That is, the fluid diode 16 allows liquid to flow in a predetermined direction, but allows no or only a small amount to flow in the reverse direction. A simple "Tesla valve" or "check valve" is used as the fluid diode 16. FIG. 3 shows an example of a "Tesla valve" fluid diode 16 made of the same metal as the piping 15, with a fluidic diode body 161 having a flow path 162 formed therein. The flow path 162 is formed in a shape resembling multiple connected teardrop-shaped loops 163. This type of flow path 162 allows the fuel salt 10 to flow smoothly in the forward direction but inhibits flow in the reverse direction. The fluidic diode 16 inside the pump body container 7 allows the fuel salt 10 to flow into the pump body container 7, while the fluidic diode 16 outside the pump body container 7 allows the fuel salt 10 to flow toward the heat exchanger 4.

[0029] [Regarding the pump main container 7] As described above, the pump main container 7 is a metal container that holds the fuel salt 10 and seals the cover gas 17. In the pump main container 7, vibrations generated in the cover gas 17 in contact with the fuel salt 10 are transmitted to the fuel salt 10. The vibrations are generated by a gas vibration generator 12, which will be described below.

[0030] [Regarding the gas vibration generator 12] The gas vibration generator 12 is a device for generating vibrations in the cover gas 17, and is configured to include a piston unit 20 having a piston, and a motor 21 for moving the piston up and down. The gas vibration generator 12 is controlled by a drive control device 8.

[0031] The piston unit 20 includes a piston, a cylinder, a drive shaft, and a connecting rod. The piston unit 20 is surrounded by a metal container 22 in which a cover gas 17 is sealed. The drive unit (not shown) is a device that rotates the drive shaft of the piston unit 20, and includes a motor, wiring, a power source, etc.

[0032] The gas vibration generator 12 is not particularly limited as long as it can generate gas vibrations, and may be of a type other than the piston type described above.

[0033] [Regarding the pulsation adjusting device 9] The pulsation adjusting device 9 is a tank (adjusting tank) into which the fuel salt 10 flows before flowing into the heat exchanger 4, and which absorbs pulsation generated in the fuel salt 10. The pulsation adjusting device 9 is a device that absorbs excessive pulsation using an air chamber 18 or the like.

[0034] <About the drive control device 8> The drive control device 8 is a device that manages and adjusts the state of vibration generation by each of the gas vibration generators 12 of the multiple high-temperature melt pumps. The drive control device 8 is configured to include a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output unit, a storage unit, a communication unit, and an inverter or the like as necessary, and controls the drive of each gas vibration generator 12 and controls the frequency of gas vibration, etc., to control the pump transport speed.

[0035] <Operation of high-temperature melt pump system 3> Vibrations generated in the cover gas 17 are transmitted to the fuel salt 10 that contacts the cover gas 17, and the fuel salt 10 flows from the top of the molten salt reactor 2 through the first pipe 151 and fluid diode 16 into the pump main vessel 7, and then flows through the second pipe 152 and fluid diode 16 into the pulsation control device 9. After flowing into the heat exchanger 4, the fuel salt 10 returns to the core 5 from the bottom of the molten salt reactor 2 via pipe 6.

[0036] <Regarding pulsation elimination in the high-temperature melt pump system 3> A method for elimination of pulsation by phase adjustment will be described with reference to FIGS. 4 to 7. Also, FIGS. 1 to 3 will be referenced as necessary. FIG. 4 shows an example of the transition of oscillating pressure in the gas vibration generator in which the pistons are driven by the triple eccentric mechanism of FIG. 1. FIG. 5 shows an example of the transition of pump transport volume in the pump body of FIG. 1, with the total transport volume obtained by superimposing the transport volumes of the three pumps indicated by a solid line. In the gas vibration generator 12, the pistons are driven by an eccentric mechanism, and the three pistons move in tandem, each offset by a one-third rotation. Therefore, the transition of oscillating pressure follows a sinusoidal curve. As shown in FIG. 2, each pump uses a Tesla valve (fluid diode 16). Therefore, when the oscillating pressure from the gas vibration generator 12 is positive, a large amount of fuel salt 10 is transported, and when it is negative, a small amount of fuel salt 10 backflows. The pumping rates from the three pump bodies 11 are superimposed as shown in Fig. 5, and the pulsation of the pumping rate of the fuel salt 10 flowing into the pulsation regulator 9 is significantly reduced. Theoretically, the pulsation rate relative to the average pumping rate is about ±7%. This system using three high-temperature melt pumps cannot completely eliminate pulsation, but the pulsation regulator 9 can further absorb a considerable amount of pulsation.

[0037] FIG. 6 shows an example of the transition of oscillating pressure in a piston-driven gas vibration generator using a double cam mechanism instead of the triple eccentric mechanism shown in FIG. 1 . FIG. 7 shows an example of the transition of pump transport volume in a pump body when the gas vibration generator shown in FIG. 6 is used. If pulsation needs to be almost completely eliminated, a method of generating oscillating pressure fluctuations as shown in FIG. 6 can be considered, using a piston-driven gas vibration generator using a double cam mechanism instead of the triple eccentric mechanism shown in FIG. 1 . By incorporating piston movement into the cam such that a positive pressure equivalent to the backflow volume generated by using a Tesla valve (fluid diode 16) is added, pulsation can be almost completely eliminated in the overall pump transport volume of high-temperature melt transported from the two pump bodies, as shown in FIG. 7 . In this case, the pulsation adjustment device 9 does not need to be provided with an air chamber 18. Note that the pulsation elimination method is not limited to the above method, and other pulsation elimination methods can also be used.

[0038] 1 to 7, the pump body 11 holding the fuel salt 10 can provide a pump with an extremely simple structure, and in particular, when a Tesla valve is used for the fluid diode 16, the pump body 11 can have an extremely simple structure with no moving parts. Because the structure of the pump body 11 is extremely simple, for example, it is easy to identify the cause of a failure, and it can also be designed to be basically maintenance-free. Furthermore, because the only object to be maintained is the gas vibration generator 12 outside the containment vessel 1, the maintenance burden can also be significantly reduced.

[0039] As can be seen from the above-described configuration and structure, the high-temperature melt pump can have an extremely simple pump structure compared to known turbo-type pumps. In particular, the pump body 11 is composed only of the piping 15, fluid diode 16, and pump body container 7, which allows for a significant reduction in the number of parts. In the high-temperature melt pump, the gas vibration generator 12 is disposed outside the containment vessel 1, which allows for a simplification of the cooling structure (not shown), resulting in a reduction in the number of parts. For these reasons, a considerable cost reduction can be expected with the high-temperature melt pump compared to turbo-type pumps.

[0040] In the high-temperature melt pump, the gas vibration generator 12 can be located at any position away from the pump main body 11 arranged inside the containment vessel 1. Therefore, compared to known turbo-type pumps, it is easier to cool the drive unit (not shown) of the gas vibration generator 12, and as a result, it can handle high-temperature melt of a considerably high temperature. Furthermore, since the high-temperature melt pump does not use a fluid bearing or the like, when a Tesla valve is used for the fluid diode 16, it can be applied to high-temperature melt containing fine solid particles as long as it is considerably smaller than the flow path 162.

[0041] <Summary> As has been explained above with reference to Figures 1 to 7, the effect is that it is possible to provide a technology for realizing a high-temperature melt pump that is more economical and practical and can be used in devices that require the circulation of high-temperature melt.

[0042] Although one embodiment and other embodiments have been described, the present invention is not limited to these. Furthermore, the effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments.

[0043] A high-temperature melt pump to which the present invention is applicable only needs to have the following configuration, and can take various forms: (1) A high-temperature melt pump to which the present invention is applicable (for example, the high-temperature melt pump in FIG. 1 ) is a high-temperature melt pump that transports a high-temperature melt (for example, fuel salt 10 in FIG. 1 ) in a predetermined direction in a pipe (for example, pipe 15 in FIG. 1 ), and is characterized by comprising: the pipe, a plurality of fluid diodes (for example, fluid diode 16 in FIG. 1 ) provided along the pipe, a pump main vessel (for example, pump main vessel 7 in FIG. 1 ) to which the pipe is connected and which contains a cover gas (for example, cover gas 17 in FIG. 1 ) that comes into contact with the high-temperature melt, and a gas vibration generator (for example, gas vibration generator 12 in FIG. 1 ) that transmits vibrations to the high-temperature melt in the pump main vessel via the cover gas.

[0044] The present invention has the effect of realizing a high-temperature melt pump that is more economical and practical and can be used in devices that require the circulation of high-temperature melt.

[0045] Furthermore, (2) a high-temperature melt pump system to which the present invention is applied (e.g., high-temperature melt pump system 3 in FIG. 1 ) is characterized in that it comprises a plurality of high-temperature melt pumps according to claim 1 , and a drive control device (e.g., drive control device 8 in FIG. 1 ) that adjusts the phase of vibrations generated by each gas vibration generator of the plurality of high-temperature melt pumps.

[0046] The present invention has the effect of realizing a high-temperature melt pump system including a high-temperature melt pump that is more economical and practical and can be used in devices that require the circulation of high-temperature melt.

[0047] (3) The high-temperature melt pump system to which the present invention is applied is characterized in that, in the high-temperature melt pump system of (2), it further includes a pulsation regulating device (e.g., pulsation regulating device 9 in FIG. 1 ) that is arranged downstream of the pipes that constitute the plurality of high-temperature melt pumps and absorbs pulsation of the high-temperature melt to which the vibrations are transmitted. Also, it is characterized in that it further includes a method of using a piston-driven gas vibration generator with a double cam mechanism instead of the triple eccentric mechanism in FIG. 1 .

[0048] According to the present invention, by arranging a pulsation adjustment device on the downstream side of the piping, or by installing a piston-driven gas vibration generator with a double cam mechanism instead of a triple eccentric mechanism, it is possible to achieve the effect of absorbing pulsations generated in the high-temperature melt.

[0049] DESCRIPTION OF SYMBOLS 1...Containment vessel 2...Molten salt reactor (nuclear reactor) 3...High-temperature melt pump system 4...Heat exchanger 5...Reactor core 6...Piping 7...Pump main body vessel 8...Drive control device 9...Pulsation adjustment device 10...Fuel salt 11...Pump main body 12...Gas vibration generator 13...Cover gas 14...External environment 15...Piping 151...First pipe 151a...Upstream end of pipe 151b...Other end 152...Second pipe 152a...One end 152b...Downstream end of pipe 16...Fluid diode 161...Fluid diode main body 162...Flow path 163...Teardrop-shaped loop 17...Cover gas 18...Air chamber 19...Piping 20...Piston part 21...Motor 22...Metal vessel

Claims

1. A high-temperature melt pump that transports high-temperature melt in a pipe in a predetermined direction, The piping; A plurality of fluid diodes provided in the middle of the piping; a pump body container to which the piping is connected and in which a cover gas is sealed and which is in contact with the high-temperature melt; a gas vibration generator that transmits vibrations to the high-temperature melt in the pump body container through reciprocating motion of the cover gas generated by reciprocating drive of a piston; The present invention relates to a method for manufacturing a computer-implemented ...

2. A high-temperature melt pump, wherein the gas vibration generating device is disposed outside a containment vessel in which the plurality of fluid diodes and the pump body container are housed together with the piping, in an external environment where the temperature is lower than the temperature inside the containment vessel.

2. A plurality of high temperature melt pumps according to claim 1; a drive control device for adjusting the phase of vibration generated by each of the gas vibration generating devices of the plurality of high-temperature melt pumps; A high temperature melt pumping system comprising:

3. a pulsation control device or a piston-driven gas vibration generator using a double cam mechanism, the device being disposed downstream of the pipes constituting the plurality of high-temperature melt pumps and absorbing the pulsation of the high-temperature melt to which the vibration is transmitted; 3. The high temperature melt pumping system of claim 2.