Reactor shutdown system and reactor shutdown method

Abstract

To provide a nuclear reactor shutdown system and nuclear reactor shutdown method for emergency shutdown, which are applicable to small reactors while maintaining safety and speed.SOLUTION: A nuclear reactor shutdown system is provided, comprising: a shielded passage extending through between reactor core fuels hermetically contained in a reactor vessel and arranged such that one end thereof is open and the other end is closed; neutron absorbers that can be introduced into the shielded passage from the opening; an elastic member designed to push the neutron absorbers into the shielded passage through the opening when released form a compressed state; and control unit disposed to maintain the compressed state of the elastic member and configured to cause the elastic member to be released from the compressed state when the temperature rises to a threshold temperature or above.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a reactor shutdown system and a reactor shutdown method.

Background Art

[0002] In a nuclear power generation system that uses nuclear fuel and generates electricity by utilizing the heat of a nuclear reaction, the heat generated in the reactor is recovered in a primary cooling system in which a primary coolant circulates between the reactor and a secondary cooling system, heat exchange is performed between the primary coolant and the secondary coolant, and a turbine provided in the secondary cooling system is rotated by the energy of the secondary coolant to generate electricity. In such nuclear facilities, a system for stopping the nuclear reaction of the reactor in an emergency is provided. For example, Patent Document 1 discloses a fuel assembly including a control element pin having a neutron absorber fixed to the upper part by a stopper that melts when the reactor output increases. In a reactor equipped with such a fuel assembly, when the reactor output increases, the stopper melts and the neutron absorber falls between the fuel portions to stop the reactor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, as power generation facilities using reactors, facilities using relatively small reactors have been studied. For example, a microreactor having a heat conduction part that does not have a temporary cooling system in which a primary coolant circulates and transfers the heat in the reactor vessel to the outside by solid heat conduction has been proposed. When using such a small reactor, it may be difficult to directly apply the conventional reactor shutdown system.

[0005] The present disclosure solves the above-described problems, and an object thereof is to provide a reactor shutdown system and a reactor shutdown method for emergency shutdown applicable to a small-sized nuclear reactor while maintaining safety and speed.

Means for Solving the Problems

[0006] To achieve the above object, a reactor shutdown system according to an aspect of the present disclosure includes a shielding passage that passes between core fuels stored in a sealed state in a reactor vessel, has one end open and the other end closed, a neutron absorber that can enter from the opening of the shielding passage, an elastic member that biases the neutron absorber in a direction to enter the inside from the opening of the shielding passage by being released from a compressed state, and a braking portion that is arranged to maintain the compressed state of the elastic member and releases the compressed state of the elastic member when the temperature becomes equal to or higher than a threshold temperature.

[0007] To achieve the above object, a reactor shutdown method according to an aspect of the present disclosure includes a shielding passage that passes between core fuels stored in a sealed state in a reactor vessel, has one end open and the other end closed, a neutron absorber that can enter from the opening of the shielding passage, an elastic member that biases the neutron absorber in a direction to enter the inside from the opening of the shielding passage by being released from a compressed state, and a braking portion that is arranged to maintain the compressed state of the elastic member and releases the compressed state of the elastic member when the temperature becomes equal to or higher than a threshold temperature. When the braking portion reaches the threshold temperature or higher and the compressed state of the elastic member is released, the neutron absorber biased by the elastic member enters the inside from the opening of the shielding passage.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to obtain an effect that it is applicable to a small-sized nuclear reactor while maintaining safety and speed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0010] (Embodiment) Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the drawings. Note that the present invention is not limited by this embodiment. Also, the components in the following embodiments include those that can be replaced and are easy for those skilled in the art, those that are substantially the same, or those within an equivalent range. Furthermore, the components in the following embodiments can be variously omitted, replaced, or changed without departing from the gist of the present disclosure. In the following embodiments, for the purpose of exemplifying the embodiments, the necessary components will be described, and other components will be omitted. The same components will be denoted by the same reference numerals, and different components will be denoted by different reference numerals.

[0011] FIG. 1 is a schematic diagram showing the schematic configuration of the nuclear power generation system according to the present embodiment. The nuclear facility shown in FIG. 1 will be described as an example of nuclear power generation that generates electricity using the heat generated in the nuclear reactor, but the present disclosure is not limited thereto. The present disclosure is also applicable to facilities that use the heat generated in the nuclear reactor for purposes other than power generation. Further, it can also be used as a facility for producing radioactive substances using the radiation generated in the nuclear reactor. The nuclear power generation system 10 shown in FIG. 1 includes a nuclear reactor unit 12 and a power generation unit 13. The power generation unit 13 includes a refrigerant circulation means 16, a turbine 18, a generator 20, a cooler 22, a compressor 24, and a regenerative heat exchanger 26.

[0012] The nuclear reactor unit 12 includes a nuclear reactor 30, a heat conduction part 32, and a nuclear reactor shutdown system 50. The nuclear reactor 30 includes a nuclear reactor vessel 40, core fuel 42, and a control unit 44. The nuclear reactor vessel 40 stores the core fuel 42 inside. The nuclear reactor vessel 40 stores the core fuel 42 in a sealed state. The nuclear reactor vessel 40 is provided with an opening / closing part so that the core fuel 42 placed inside can be inserted and removed. The opening / closing part is, for example, a lid. The nuclear reactor vessel 40 can maintain a sealed state even when a nuclear reaction occurs inside and the inside becomes high temperature and high pressure. Further, the nuclear reactor vessel 40 is formed of a material having neutron ray shielding performance and is formed with a thickness such that the neutron rays generated inside do not leak to the outside. The nuclear reactor vessel 40 is formed of, for example, concrete. The nuclear reactor vessel 40 may contain an element having high shielding properties such as boron.

[0013] The core fuel 42 includes a plurality of fuel holding plates 43. The fuel holding plates 43 have a plurality of nuclear fuels arranged inside. The fuel holding plates 43 are formed of a material that transfers the heat generated by the nuclear fuel. The fuel holding plates 43 can use graphite, silicon carbide, etc. The core fuel 42 generates reaction heat when the nuclear fuel undergoes a nuclear reaction.

[0014] The control unit 44 has a shielding material that can move between the core fuels 42. The shielding material is a so-called control rod that has the function of shielding radiation and suppressing nuclear reactions. The nuclear reactor 30 controls the reaction of the core fuel 42 by moving the control unit 44 and adjusting the position of the shielding material.

[0015] As shown in FIG. 1, the heat conduction part 32 is arranged inside the reactor vessel 40 and is in contact with the fuel holding plate 43. The heat conduction part 32 of the present embodiment has a plurality of plate shapes and is structured to be alternately laminated with the fuel holding plate 43. The heat conduction part 32 is a plate with an outer shape larger than that of the fuel holding plate 43 and protrudes into the area where the fuel holding plate 43 is not arranged. Here, for example, titanium, nickel, copper, graphite, or graphene can be used for the heat conduction part 32.

[0016] In order to increase the heat transfer efficiency to the protruding part, it is preferable to use graphene arranged in a direction in which heat easily conducts along the surface of the plate for the heat conduction part 32. The heat conduction part 32 transfers heat by solid heat conduction. That is, the heat conduction part 32 transfers heat without using a heat medium (fluid). Specifically, the heat conduction part 32 transfers the heat generated in the core fuel 42 to the power generation unit 13 by solid heat conduction.

[0017] In the nuclear reactor unit 12, a nuclear reaction occurs in the core fuel 42 inside the nuclear reactor 30, generating reaction heat. The generated heat is stored inside the reactor vessel 40, making the inside temperature high. Also, in the nuclear reactor unit 12, a part of the heat generated in the nuclear reactor 30 is transferred to the heat conduction part 32. The heat conduction part 32 heats the refrigerant flowing through the refrigerant circulation means 16 of the power generation unit 13. Here, it is preferable to use carbon dioxide (CO2) as the refrigerant.

[0018] The nuclear reactor shutdown system 50 is a system for urgently shutting down the nuclear reaction of the core fuel 42. The detailed configuration of the nuclear reactor shutdown system 50 of the embodiment will be described later.

[0019] The refrigerant circulation means 16 includes a circulation path 34 that circulates outside the reactor vessel 40, and a heat exchange section 36 that circulates inside the reactor vessel 40. The refrigerant circulation means 16 forms a closed loop with the circulation path 34 and the heat exchange section 36 and is circulated. The circulation path 34 is a path for circulating the refrigerant outside the reactor vessel 40, and the turbine 18, the cooler 22, the compressor 24, and the regenerative heat exchanger 26 are connected thereto. The heat exchange section 36 is inserted into the reactor vessel 40 and disposed therein. Both ends of the heat exchange section 36 are exposed outside the reactor vessel 40 and connected to the circulation path 34. The heat exchange section 36 is a pipe through which the refrigerant flows and contacts a region that does not contact the core fuel 42 of the heat conduction section 32. That is, the heat exchange section 36 contacts a portion that protrudes beyond the core fuel 42 of the heat conduction section 32. The heat exchange section 36 exchanges heat with the heat conduction section 32 and heats the refrigerant.

[0020] The refrigerant flowing through the refrigerant circulation means 16 is supplied to the heat exchange section 36. The nuclear power generation system 10 performs heat exchange between the heat conduction section 32 and the refrigerant supplied from the refrigerant circulation means 16. The heat exchanger of the present embodiment is composed of the heat conduction section 32 and the heat exchange section 36 of the refrigerant circulation means 16. The heat exchanger recovers the heat of the heat conduction section 32 with the refrigerant flowing through the refrigerant circulation means 16. That is, the refrigerant is heated by the heat conduction section 32. The heat medium heated by the heat exchange section 36 flows in the order of the turbine 18, the cooler 22, the compressor 24, and the regenerative heat exchanger 26. The refrigerant that has passed through the regenerative heat exchanger 26 is supplied to the heat exchange section 36 again. In this way, the refrigerant is circulated through the refrigerant circulation means 16.

[0021] The turbine 18 has the refrigerant that has passed through the heat conduction section 32 flowing into it. The turbine 18 is rotated by the energy of the heated refrigerant. That is, the turbine 18 converts the energy of the refrigerant into rotational energy and absorbs energy from the refrigerant. The generator 20 is connected to the turbine 18 and rotates integrally with the turbine 18. The generator 20 generates electricity by rotating with the turbine 18.

[0022] The cooler 22 cools the refrigerant that has passed through the turbine 18. The cooler 22 is a condenser or the like when the refrigerant is temporarily liquefied in a chiller or the like. The compressor 24 is a pump that pressurizes the refrigerant. The regenerative heat exchanger 26 performs heat exchange between the refrigerant that has passed through the turbine 18 and the refrigerant that has passed through the compressor 24. The regenerative heat exchanger 26 heats the refrigerant that has passed through the compressor 24 with the refrigerant that has passed through the turbine 18. That is, the regenerative heat exchanger 26 performs heat exchange between the refrigerant before being cooled by the cooler 22 and the refrigerant after being cooled by the cooler 22, and recovers the heat discarded by the cooler 22 with the refrigerant before being supplied to the reactor unit 12.

[0023] The nuclear power generation system 10 transfers the heat generated by the reaction of the nuclear fuel of the reactor unit 12 to the refrigerant in the heat exchange section 36 by the heat conduction section 32, and heats the refrigerant flowing through the refrigerant circulation means 16 with the heat of the heat conduction section 32. That is, the refrigerant absorbs the heat transferred by the heat conduction section 32. Thereby, the heat generated in the reactor unit 12 is transferred by solid heat conduction by the heat conduction section 32 and recovered by the refrigerant. The refrigerant is compressed by the compressor 24, then heated when passing through the heat conduction section 32, compressed, and rotates the turbine 18 with the compressed and heated energy. Then, it is cooled to the reference state by the cooler 22 and supplied to the compressor 24 again.

[0024] As described above, the nuclear power generation system 10 transfers the heat of the reactor 30 to the refrigerant that becomes the medium for rotating the turbine 18 by using the heat conduction section 32 that transfers heat by solid heat conduction.

[0025] By using carbon dioxide as the refrigerant, the nuclear power generation system 10 can suppress the contamination of the refrigerant even when the refrigerant flows inside the reactor 30. Thereby, the risk of contamination of the medium that rotates the turbine 18 can be reduced. In addition, by providing the heat conduction section 32 that transfers heat by solid heat conduction, the heat conduction section 32 can shield neutron rays.

[0026] Further, the reactor vessel 40 is preferably formed of a material having a lower thermal conductivity than that of the heat conduction portion 32. Thereby, it is possible to suppress the heat inside the reactor 30 from being discharged from portions other than the heat conduction portion 32, which is a path for discharging heat to the outside.

[0027] FIG. 2 is a schematic diagram showing a schematic configuration of a reactor unit including a reactor shutdown system according to the present embodiment. FIG. 3 is a schematic diagram showing a state in which the reactor shutdown system shown in FIG. 2 is operating. The reactor shutdown system 50 includes a neutron absorber 52, a shielding passage 54, an elastic member 56, and a braking portion 58.

[0028] The neutron absorber 52 is a substance that absorbs neutrons, for example, a substance containing boron (B), cadmium (Cd), xenon (Xe), hafnium (Hf), or the like. The neutron absorber 52 shown in FIGS. 2 and 3 is a so-called control rod extending in the horizontal direction. As shown in FIG. 3, the neutron absorber 52 can be introduced into the core to reduce the neutrons absorbed by the nuclear fuel, suppress the nuclear reaction, or stop the reactor 30.

[0029] The shielding passage 54 is a passage passing between the core fuels 42. The shielding passage 54 is formed to extend on the extension in the extending direction of the neutron absorber 52. The shielding passage 54 of the embodiment is formed to extend horizontally at the center of the core. One end (the left end in FIGS. 2 and 3) of the shielding passage 54 is open to the outside of the core fuel 42. The other end (the right end in FIGS. 2 and 3) of the shielding passage 54 is closed. The neutron absorber 52 can enter the shielding passage 54 from the opening.

[0030] The elastic member 56 is disposed sandwiching the neutron absorber 52 on the extension on the side where the shielding passage 54 opens. In the embodiment, the elastic member 56 is a compression coil spring. One arm of the compression coil spring of the elastic member 56 is fixed to the reactor vessel 40, and the other arm is fixed to the neutron absorber 52, and the neutron absorber 52 side can reciprocate in the axial direction by the elastic force. The elastic member 56 is maintained in a compressed state by the braking portion 58 during the rated operation of the reactor vessel 40. When the elastic member 56 is in a compressed state, the neutron absorber 52 maintains a state where only the tip is supported at the opening of the shielding passage 54.

[0031] The elastic member 56 can be elastically deformed so as to expand in the direction in which the neutron absorber 52 enters the shielding passage 54 when released from the braking portion 58. That is, when the elastic member 56 is released from the compressed state, it biases the neutron absorber 52 in the direction of entering the inside from the opening of the shielding passage 54. The elastic member 56 is formed of a material having a melting point higher than the threshold temperature that can maintain its shape even when the temperature is higher than the temperature during the rated operation of the reactor vessel 40, that is, in an abnormal operating state, and the braking portion 58 described later reaches the threshold temperature.

[0032] The braking portion 58 is disposed so as to maintain the compressed state of the elastic member 56. In the example shown in FIG. 2, the braking portion 58 includes a plate-like portion disposed so as to cover the coil portion except for the arm portion from the side fixed to the neutron absorber 52 of the elastic member 56. The plate-like portion melts and forms a hole or deteriorates and detaches at a temperature equal to or higher than the threshold temperature. The braking portion 58 may include, for example, a valve body that opens at a temperature equal to or higher than the threshold temperature. The braking portion 58 may be, for example, in the form of a string connecting both ends of the elastic member 56 in a compressed state.

[0033] When the temperature is lower than a predetermined threshold temperature, the braking part 58 maintains the compressed state of the elastic member 56 as shown in FIG. 2. When the temperature becomes equal to or higher than the threshold temperature, the braking part 58 releases the compressed state of the elastic member 56 as shown in FIG. 3. The braking part 58 is formed of a material that melts or deteriorates at a temperature equal to or higher than the threshold temperature, for example. The braking part 58 is formed of a material whose melting point is equal to or higher than the temperature during the rated operation of the reactor vessel 40. The braking part 58 is formed of a metal such as brass, for example.

[0034] During the rated operation of the reactor 30, the temperature of the braking part 58 is maintained lower than the threshold temperature in the reactor shutdown system 50. In this state, since the braking part 58 maintains the compressed state of the elastic member 56, only the tip of the neutron absorber 52 is supported at the opening of the shielding passage 54.

[0035] When an abnormality occurs in the reactor 30 and the temperature inside the reactor vessel 40 rises, causing the temperature of the braking part 58 to become equal to or higher than the threshold temperature, as shown in FIG. 3, the end of the elastic member 56 fixed to the neutron absorber 52 is released, and the compressed state is released. When the compressed state of the elastic member 56 is released, the neutron absorber 52 is biased toward the shielding passage 54 side and enters the inside of the shielding passage 54.

[0036] The neutron absorber 52 that has entered the inside of the shielding passage 54, that is, reached the inside of the core, absorbs the neutrons in the core and suppresses the nuclear reaction of the core fuel 42. The neutron absorber 52 biased by the elastic member 56 further advances toward the closed end side inside the shielding passage 54. As the amount of entry into the core increases, the amount of neutron absorption in the core also increases, and the nuclear reaction of the core fuel 42 stops.

[0037] FIG. 4 is a schematic diagram showing a reactor unit including another example of a reactor shutdown system. FIG. 5 is a schematic diagram showing a state in which the reactor shutdown system shown in FIG. 4 is in operation. The reactor shutdown system 50a included in the reactor unit 12a shown in FIGS. 4 and 5 is different from the reactor shutdown system 50 shown in FIGS. 2 and 3 in that instead of the rod-shaped neutron absorber 52, it includes a delivery member 60 and a plurality of spherical neutron absorbers 62. Hereinafter, the delivery member 60 and the neutron absorber 62, which are specific configurations of the reactor shutdown system 50a, will be described, and detailed descriptions of configurations similar to those of the reactor shutdown system 50 will be omitted.

[0038] The delivery member 60 is a member that delivers the neutron absorber 62 from the opening of the shielding passage 54 toward the inside as the elastic member 56 is released from the compressed state. The delivery member 60 is disposed between the side where the shielding passage 54 opens and the elastic member 56. In the embodiment, the delivery member 60 has a cylinder 60a and a piston 60b.

[0039] The cylinder 60a is disposed on an extension of the side where the shielding passage 54 opens. A braking portion 58 is disposed at one end (the left end in FIGS. 4 and 5) of the cylinder 60a. The other end (the right end in FIGS. 4 and 5) of the cylinder 60a opens and communicates with the shielding passage 54.

[0040] The piston 60b is disposed so as to be movable in the axial direction (the left-right direction in FIGS. 4 and 5) inside the cylinder 60a. The piston 60b is fixed to the elastic member 56 so as to be reciprocally movable in the axial direction by the elastic force of the elastic member 56. The piston 60b is biased toward the shielding passage 54 side by the elastic member 56 when the elastic member 56 is released from the braking portion 58 and released from the elastic state.

[0041] The interior of the cylinder 60a is separated by the piston 60b into a space on the shutoff passage 54 side and a space on the elastic member 56 side. As shown in FIG. 4, a neutron absorber 62 is accommodated on the shutoff passage 54 side inside the cylinder 60a. While the neutron absorber 52 of the reactor shutdown system 50 shown in FIGS. 2 and 3 is rod-shaped, the neutron absorber 62 of the reactor shutdown system 50a shown in FIGS. 4 and 5 is in the form of a plurality of granules. The neutron absorber 62 shown in FIGS. 4 and 5 is a plurality of solid spheres, but the individual shapes are not particularly limited as long as they can move finely and separately, and may include, for example, ellipsoids or rod shapes. Also, it is not limited to solids and may include gels, liquids, and gases, but is preferably a solid sphere.

[0042] During the rated operation of the reactor 30, the temperature of the braking part 58 is maintained lower than the threshold temperature in the reactor shutdown system 50a. In this state, as shown in FIG. 2, since the braking part 58 maintains the compressed state of the elastic member 56, the piston 60b is maintained in a state of being attracted to the elastic member 56 side inside the cylinder 60a, and the neutron absorber 62 is maintained in a state of being retained inside the cylinder 60a.

[0043] When an abnormality occurs in the reactor 30 and the temperature inside the reactor vessel 40 rises so that the temperature of the braking part 58 becomes equal to or higher than the threshold temperature in the reactor shutdown system 50a, as shown in FIG. 3, the end of the elastic member 56 fixed to the piston 60b is released, and the compressed state is released. When the compressed state of the elastic member 56 is released, the piston 60b is biased toward the shutoff passage 54 side, and the neutron absorber 62 inside the cylinder 60a is sent out from the opening of the shutoff passage 54 toward the inside.

[0044] The neutron absorber 62 that has entered the inside of the shutoff passage 54, that is, has reached the inside of the reactor core, absorbs the neutrons in the reactor core and suppresses the nuclear reaction of the reactor core fuel 42. The shutoff passage 54 is successively filled with the neutron absorber 62, and the nuclear reaction of the reactor core fuel 42 stops as a result of the plurality of neutron absorbers 62 absorbing the neutrons in the reactor core.

[0045] In the reactor shutdown system 50a shown in FIGS. 4 and 5, since the neutron absorber 62 is a solid sphere, the neutron absorber 62 can roll inside the cylinder 60a. Thereby, when a plurality of neutron absorbers 62 are successively sent to the piston 60b toward the opening of the shielding passage 54, it is possible to prevent the neutron absorber 62 from being clogged at the opening.

[0046] FIG. 6 is a schematic diagram showing a reactor unit including another example of the reactor shutdown system. The reactor shutdown system 50b included in the reactor unit 12b shown in FIG. 6 further includes a heating unit 64 and a control unit 70 in addition to the configuration of the reactor shutdown system 50 shown in FIG. 2. Hereinafter, the heating unit 64 and the control unit 70, which are specific configurations of the reactor shutdown system 50b, will be described, and detailed descriptions of configurations similar to those of the reactor shutdown system 50 will be omitted.

[0047] The heating unit 64 can heat the braking unit 58 to a temperature equal to or higher than a threshold value based on a control signal received from the control unit 70. The configuration and heating method of the heating unit 64 are not particularly limited. For example, it may be heated by directly energizing the braking unit 58, or may be heated by heat radiation from a heat source that is heated by energization.

[0048] The control unit 70 sends a control signal for heating the braking unit 58 to the heating unit 64. The control unit 70 may send a control signal for heating the braking unit 58 when it receives a predetermined operation by an operator. When the control unit 70 detects some abnormality, it may send a control signal for heating the braking unit 58 based on a predetermined criterion. The control unit 70 may be provided as part of a control system that controls the operation of the reactor unit 12, or may be provided as part of, for example, an auxiliary power supply system at the time of abnormality occurrence, in cooperation with the reactor unit 12 or the nuclear power generation system 10.

[0049] (Advantages and effects of the embodiment) The reactor shutdown systems 50, 50a, 50b, and the reactor shutdown method described in the embodiment can be understood as follows, for example.

[0050] The reactor shutdown systems 50, 50a, 50b according to the first aspect include a shielding passage 54 that passes between the core fuels 42 stored in a sealed state in the reactor vessel 40, has one end open and the other end closed, neutron absorbers 52, 62 that can enter from the opening of the shielding passage 54, an elastic member 56 that biases the neutron absorbers 52, 62 to enter the inside from the opening of the shielding passage 54 when released from the compressed state, and a braking portion 58 that is arranged to maintain the compressed state of the elastic member 56 and releases the compressed state of the elastic member 56 when the temperature exceeds a threshold temperature.

[0051] In the reactor shutdown systems 50, 50a, 50b according to the first aspect, when the temperature in the reactor vessel 40 rises during an abnormality and the braking portion 58 that maintains the compressed state of the elastic member 56 exceeds the threshold temperature, the compressed state of the elastic member 56 is released. The elastic member 56 holds the neutron absorbers 52, 62 outside the core fuel 42 in the compressed state, and biases them into the core fuel 42 when the compressed state is released. That is, without requiring a special control function, when the braking portion 58 exceeds the threshold temperature, the neutron absorbers 52, 62 enter between the core fuels 42, so that during an abnormal temperature rise in the reactor vessel 40, the nuclear reaction can be suppressed passively and the function can be stopped safely and quickly. Further, the direction in which the elastic member 56 biases the neutron absorbers 52, 62 is not particularly limited, and can be appropriately changed according to the shape of the reactor vessel 40, the internal configuration, and the arrangement of the core fuel 42, such as the horizontal direction, the vertical direction, the diagonal direction, etc. Therefore, it is also applicable to small reactors.

[0052] The reactor shutdown systems 50, 50a, 50b according to the second aspect are provided in a reactor unit 12 including a reactor 30 including a core fuel 42 and a reactor vessel 40, and a heat conduction part 32 disposed inside the reactor vessel 40 and transferring the heat of the core fuel 42 by solid heat conduction. The reactor shutdown systems 50, 50a, 50b do not require a special control function, and since a configuration can be realized in which the neutron absorber 52, 62 enters between the core fuels 42 when the braking part 58 reaches a threshold temperature or higher, it is also applicable to the reactor unit 12 that transfers the heat of the core fuel 42 by solid heat conduction.

[0053] In the reactor shutdown systems 50, 50a, 50b according to the third aspect, the braking part 58 is formed of a material that melts or deteriorates at a threshold temperature or higher. Such a braking part 58 melts at a threshold temperature or higher to open or break a hole, or deteriorates and detaches from the outer peripheral part. Thereby, a configuration for releasing the compressed state of the elastic member 56 when the communication parts 56, 57 reach a threshold temperature or higher can be realized with a simple configuration.

[0054] In the reactor shutdown systems 50, 50b according to the fourth aspect, the neutron absorber 52 is rod-shaped and extends in the direction in which the shielding passage 54 extends. That is, the neutron absorber 52 is a so-called control rod. Since the control rod enters between the core fuels 42 when the braking part 58 reaches a threshold temperature or higher, a configuration for passively suppressing a nuclear reaction and stopping the function safely and quickly can be realized with a simple configuration when an abnormal temperature rise occurs inside the reactor vessel 40.

[0055] The reactor shutdown system 50a according to the fifth aspect includes a feeding member 60 that feeds the neutron absorber 62 from the opening of the shielding passage 54 toward the inside as the elastic member 56 is released from the compressed state. That is, even if the elastic member 56 and the neutron absorber 62 are not directly connected, the neutron absorber 62 can be held outside the core fuel 42 and biased toward the inside of the core fuel 42.

[0056] In the reactor shutdown system 50a according to the sixth aspect, the delivery member 60 has a cylinder 60a with a braking part 58 arranged at one end and the other end communicating with the opening of the shielding passage 54, and a piston 60b capable of reciprocating inside the cylinder 60a by the elastic force of the elastic member 56. The neutron absorber 62 is accommodated inside the cylinder 60a on the shielding passage 54 side from the piston 60b, and is sent out from the opening of the shielding passage 54 toward the inside when the piston 60b is biased toward the shielding passage 54 side. That is, without directly connecting the elastic member 56 and the neutron absorber 62, a configuration in which the neutron absorber 62 is held outside the core fuel 42 and biased into the core fuel 42 can be realized with a simple configuration.

[0057] In the reactor shutdown system 50a according to the seventh aspect, the neutron absorber 62 is a plurality of solid spheres. Since the neutron absorber 60 is not a single mass but a plurality of substances capable of passing through the opening of the shielding passage 54, there is freedom in the overall shape in the state of being accommodated in the cylinder 60a. That is, there is freedom in the diameter of the cylinder 60a that accommodates the neutron absorber 62, and the shortening in the axial direction can be achieved, so it is applicable to small reactors. Also, since the neutron absorber 62 can roll inside the cylinder 60a, when a plurality of neutron absorbers 62 are successively sent to the piston 60b toward the opening of the shielding passage 54, it is possible to prevent the neutron absorber 62 from being clogged at the opening.

[0058] The reactor shutdown system 50b according to the eighth aspect further includes a heating unit 64 capable of heating the braking part 58 to a threshold temperature or higher, and a control unit 70 that sends a control signal for heating the braking part 58 to the heating unit 64. That is, even when the braking part 58 has not risen to the threshold temperature in case of an abnormality, when a further temperature rise in the reactor vessel 40 is predicted or another abnormality is detected, the nuclear reaction can be suppressed by an active method and the function can be stopped safely and quickly.

[0059] The reactor shutdown method according to the ninth aspect passes through the core fuel 42 stored in a sealed state in the reactor vessel 40, and includes a shielding passage 54 having one end open and the other end blocked, neutron absorbers 52, 62 that can enter from the opening of the shielding passage 54, an elastic member 56 that biases the neutron absorbers 52, 62 to enter the interior from the opening of the shielding passage 54 by being released from a compressed state, and a braking portion 58 that is arranged to maintain the compressed state of the elastic member 56 and releases the compressed state of the elastic member 56 when the temperature reaches or exceeds a threshold temperature. When the braking portion 58 reaches or exceeds the threshold temperature, the compressed state of the elastic member 56 is released, and the neutron absorbers 52, 62 biased by the elastic member 56 enter the interior from the opening of the shielding passage 54.

[0060] In the reactor shutdown method according to the ninth aspect, when the temperature in the reactor vessel 40 rises during an abnormality and the braking portion 58 that maintains the compressed state of the elastic member 56 reaches or exceeds the threshold temperature, the compressed state of the elastic member 56 is released. The elastic member 56 holds the neutron absorbers 52, 62 outside the core fuel 42 in the compressed state and biases them into the core fuel 42 when the compressed state is released. That is, without requiring a special control function, when the braking portion 58 reaches or exceeds the threshold temperature, the neutron absorbers 52, 62 enter between the core fuel 42. Therefore, during an abnormal temperature rise in the reactor vessel 40, the nuclear reaction can be suppressed passively, and the function can be stopped safely and quickly. Further, the direction in which the elastic member 56 biases the neutron absorbers 52, 62 is not particularly limited, and can be appropriately changed according to the shape of the reactor vessel 40, the internal configuration, and the arrangement of the core fuel 42, such as the horizontal direction, the vertical direction, or the diagonal direction. Therefore, it is also applicable to small reactors.

[0061] As described above, the embodiments of the present disclosure have been described, but the embodiments are not limited by the description content of these embodiments.

Description of Reference Numerals

[0062] 10 Nuclear power generation system 12, 12a, 12b Reactor unit 13 Power generation unit 14 Heat exchanger 16 Refrigerant circulation means 18 Turbine 20 Generator 22 Chiller (cooler) 24 Pump (compressor) 26 Regenerative heat exchanger 30 Reactor 32 Heat conduction part 34 Circulation path 36 Heat exchange part 40 Reactor vessel 42 Core fuel 43 Fuel holding plate 44 Control unit 50, 50a, 50b Reactor shutdown system 52, 62 Neutron absorber 54 Shielding passage 56 Elastic member 58 Braking part 60 Feeding member 60a Cylinder 60b Piston 64 Heating unit 70 Control part

Claims

1. A neutron-absorbing passage that passes between the core fuels stored in a sealed state in a reactor vessel, with one end open and the other end closed; A neutron absorber that can enter from the opening of the neutron-absorbing passage; An elastic member that, when released from a compressed state, biases the neutron absorber in a direction to enter the interior from the opening of the neutron-absorbing passage; A braking portion that is arranged to maintain the compressed state of the elastic member and releases the compressed state of the elastic member when the temperature reaches a threshold temperature or higher; A feeding member that feeds the neutron absorber from the opening of the neutron-absorbing passage into the interior as the elastic member is released from the compressed state; Comprising; The feeding member has a cylinder with the braking portion arranged at one end and the other end communicating with the opening of the neutron-absorbing passage, and a piston that can reciprocate inside the cylinder by the elastic force of the elastic member; The neutron absorber is accommodated inside the cylinder on the neutron-absorbing passage side of the piston, and a reactor shutdown system in which the piston is biased toward the neutron-absorbing passage side and the neutron absorber is fed from the opening of the neutron-absorbing passage into the interior.

2. A neutron-absorbing passage that passes between the core fuels stored in a sealed state in a reactor vessel, with one end open and the other end closed; A neutron absorber that can enter from the opening of the neutron-absorbing passage; An elastic member that, when released from a compressed state, biases the neutron absorber in a direction to enter the interior from the opening of the neutron-absorbing passage; A braking portion that is arranged to cover the elastic member from the side where the neutron absorber is arranged and to maintain the compressed state of the elastic member, and releases the compressed state of the elastic member when the temperature reaches a threshold temperature or higher; A reactor shutdown system comprising.

3. The reactor shutdown system according to claim 2, further comprising a feeding member that feeds the neutron absorber from the opening of the neutron-absorbing passage into the interior as the elastic member is released from the compressed state.

4. The feeding member has a cylinder with the braking portion arranged at one end and the other end communicating with the opening of the neutron-absorbing passage, and a piston that can reciprocate inside the cylinder by the elastic force of the elastic member. The neutron absorber is accommodated inside the cylinder on the shielding passage side from the piston, and is sent out from the opening of the shielding passage toward the inside when the piston is urged toward the shielding passage side. The reactor shutdown system according to claim 3.

5. The neutron absorber is a plurality of solid spheres. The reactor shutdown system according to claim 1 or 4.

6. A nuclear reactor including the core fuel and the reactor vessel, A heat conduction part disposed inside the reactor vessel and transferring the heat of the core fuel by solid heat conduction, The reactor shutdown system according to any one of claims 1 to 5, provided in a reactor unit including the above.

7. The braking part is formed of a material that melts or deteriorates at a temperature equal to or higher than the threshold temperature. The reactor shutdown system according to any one of claims 1 to 6.

8. The neutron absorber is rod-shaped and extends in the direction in which the shielding passage extends. The reactor shutdown system according to claim 2, 6 or 7.

9. A heating unit capable of heating the braking part to a temperature equal to or higher than the threshold temperature, A control unit that sends a control signal for heating the braking part to the heating unit. The reactor shutdown system according to any one of claims 1 to 8, further including the above.

10. A shielding passage that passes between core fuels stored in a reactor vessel in a sealed state, has one end open and the other end closed, A neutron absorber that can enter from the opening of the shielding passage, An elastic member that biases the neutron absorber in a direction to enter the inside from the opening of the shielding passage when released from a compressed state, A braking part that is arranged to maintain the compressed state of the elastic member and releases the compressed state of the elastic member when the temperature reaches a threshold temperature or higher, In a feeding member that feeds the neutron absorber from the opening of the shielding passage toward the inside as the elastic member is released from the compressed state, The feeding member has a cylinder in which the braking part is arranged at one end and the other end communicates with the opening of the shielding passage, and a piston that can reciprocate inside the cylinder by the elastic force of the elastic member, The neutron absorber is accommodated inside the cylinder on the shielding passage side from the piston, A reactor shutdown method in which when the braking part reaches a temperature equal to or higher than the threshold temperature, the compressed state of the elastic member is released, so that the piston is biased toward the shutoff passage by the elastic member, and the biased neutron absorber is sent from the opening of the shutoff passage into the interior.

11. A shutoff passage that passes between the core fuels stored in a sealed state in a reactor vessel, has one end open and the other end closed, A neutron absorber that can enter from the opening of the shutoff passage, An elastic member that biases the neutron absorber in a direction to enter the interior from the opening of the shutoff passage when released from a compressed state, A braking part that is arranged to cover the elastic member from the side where the neutron absorber is arranged and is arranged to maintain the compressed state of the elastic member, and releases the compressed state of the elastic member when the temperature reaches a threshold temperature or higher. In this case, A reactor shutdown method in which when the braking part reaches a temperature equal to or higher than the threshold temperature, the compressed state of the elastic member is released, so that the neutron absorber biased by the elastic member enters the interior from the opening of the shutoff passage.

Images