Power supply unit and decay heat removal system for fast reactors

Abstract

To reduce cost while properly dealing with start-up currents from a load in a system that starts up the load by switching to an emergency generator when no power is fed from a power-supply.SOLUTION: A power-supply device comprises: a power-supply bus bar; a generator for feeding power to an AC motor; a storage battery for charging part of the power fed from an external power-supply; a charging / discharging switching part for switching charging / discharging of the storage battery; and a charging / discharging control part for controlling an operation of the charging / discharging switching part. The charging / discharging control part that makes the charging / discharging switching part be in a charging state during a steady operation switches the charging / discharging switching part from a charging state to a discharging state to feed the power charged in the AC motor when operating a damper in an emergency operation in which no power can be fed from the external power-supply.SELECTED DRAWING: Figure 3

Description

Technical Field

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[0001] The present invention relates to a power supply device and a decay heat removal system used in a fast reactor.

Background Art

[0002] In a plant such as a fast reactor, a system that operates by driving an AC motor that drives a damper, an electric valve, etc. is known (for example, see Patent Document 1). When the power supply from the power source cannot be obtained due to a power failure or the like, such a system switches to an emergency generator and supplies power to the load.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Such a system is a direct starting method in which the power supply voltage is directly applied to the load for starting, so a starting current that reaches 8 to 10 times the rated value may flow when the load is started. Therefore, measures have been taken such as providing a large-capacity generator corresponding to the large starting current, and providing a compensation device such as a star-delta starter or a reactor starter for each load, but there has been a problem that the system has become large and the cost has increased.

[0005] ​​​​​​​​In a first aspect of the present invention, a power supply device for a decay heat removal system for cooling decay heat generated in the core of a fast reactor using a liquid metal, the system having an air cooler for cooling a circulating liquid metal, the power supply device being connectable to an external power grid, comprising: a power bus for transmitting power supplied from an external power source to an AC motor for operating a damper of the air cooler; a generator for supplying power to the AC motor when power cannot be supplied from the external power source; a storage battery connected to the power bus for charging a portion of the power supplied from the external power source; a charge / discharge switching unit for switching between charging and discharging the storage battery; and a charge / discharge control unit for controlling the operation of the charge / discharge switching unit, wherein the charge / discharge control unit keeps the charge / discharge switching unit in a charging state during steady-state operation when power is supplied from the external power source, and switches the charge / discharge switching unit from a charging state to a discharging state to supply the charged power to the AC motor when operating the damper during emergency operation when power cannot be supplied from the external power source.

[0007] The charge / discharge control unit may further include a current detection unit for detecting the magnitude of the current flowing from the generator to the AC motor, and in the emergency operation, if the magnitude of the current detected by the current detection unit is greater than or equal to a predetermined value, the charge / discharge switching unit may switch from the charging state to the discharging state.

[0008] The charge / discharge control unit may, after switching the charge / discharge switching unit from a charging state to a discharging state, switch the charge / discharge switching unit from a discharging state to a charging state if the magnitude of the current detected by the current detection unit falls below a predetermined value.

[0009] The charge / discharge control unit further includes a receiving unit that receives an instruction signal from the decay heat removal system to operate the damper, and the charge / discharge control unit may switch the charge / discharge switching unit from a charging state to a discharging state when the receiving unit receives an instruction signal indicating that the damper should be operated during the emergency operation.

[0010] The charge / discharge control unit may switch the charge / discharge switching unit from the discharge state to the charge state after a predetermined time has elapsed since switching the charge / discharge switching unit from the charge state to the discharge state.

[0011] A second embodiment of the present invention provides a decay heat removal system for cooling decay heat generated in the core of a fast reactor, comprising: a temperature detector for detecting the temperature of the liquid metal circulating in the core of the fast reactor; an air cooler having a damper and an AC motor, which cools the circulating liquid metal by taking in outside air when the damper is opened; a damper control unit that supplies an instruction signal to the air cooler to open and close the damper based on the temperature detection result of the temperature detector; and a power supply device of the first embodiment that switches the supply of power from the storage battery to the AC motor in accordance with the operation of the damper by the damper control unit.

[0012] The damper control unit may set the damper opening to a predetermined first opening in response to the switch from steady-state operation to emergency operation.

[0013] The damper control unit may, when the temperature of the liquid metal drops below a predetermined first temperature, set the damper opening to a second opening, which is smaller than the first opening.

[0014] The damper control unit may increase the damper's opening degree beyond the second opening degree after a predetermined time has elapsed since setting the damper to the second opening degree. [Effects of the Invention]

[0015] According to the present invention, in a system that switches to an emergency generator to start a load when power supply from the power source becomes unavailable, it is possible to reduce costs while responding to the starting current of the load. [Brief explanation of the drawing]

[0016] [Figure 1]Shows a configuration example of the fast reactor S according to this embodiment. [Figure 2] Shows a configuration example of the conventional power supply device 200 of the decay heat removal system 100. [Figure 3] Shows an example of the power supply current supplied to the load of the power supply device 200. [Figure 4] Shows a configuration example of the power supply device 300 according to this embodiment. [Figure 5] Shows an example of the relationship between the temperature of the primary sodium of the fast reactor S according to this embodiment, the operating state of the damper, and the change in the input current Iin.

Mode for Carrying Out the Invention

[0017] <Configuration Example of Fast Reactor S> FIG. 1 shows a configuration example of the fast reactor S according to this embodiment. The fast reactor S generates electricity by driving a steam turbine with the heat generated by nuclear fission of atoms such as plutonium. The fast reactor S includes a main vessel 10, a primary system pump 20, an intermediate heat exchanger 30, a secondary system pump 40, a steam generator 50, a turbine 60, a feed water pump 70, a generator 80, a control device 90, and a decay heat removal system 100.

[0018] The main vessel 10 houses the reactor core 11, the primary system pump 20, the intermediate heat exchanger 30, and a liquid metal for cooling, and holds the primary coolant inside. The reactor core 11 contains fuels such as plutonium and uranium and control rods, and generates energy by a chain reaction of nuclear fission.

[0019] The primary system pump 20 circulates the liquid metal to cool the reactor core 11. The liquid metal, as an example, contains metallic sodium. The primary system pump 20 constitutes the primary cooling system of the fast reactor S. FIG. 1 shows an example in which the primary system pump 20 supplies low-temperature metallic sodium to the reactor core 11 to cool the reactor core 11, and the metallic sodium heated by the heat of the reactor core 11 is discharged from the reactor core 11.

[0020] The intermediate heat exchanger 30 transfers the heat of the high-temperature liquid metal discharged from the reactor core 11 to the liquid metal circulating in a secondary cooling system different from the primary cooling system. In other words, the intermediate heat exchanger 30 is a heat exchanger that transfers the heat generated in the reactor core 11 to the secondary cooling system outside the primary container 10. As a result, the high-temperature liquid metal in the primary cooling system releases heat and becomes low-temperature liquid metal. Then, the primary system pump 20 supplies the cooled liquid metal to the reactor core 11 and circulates it. In this embodiment, the liquid metal circulated by the primary system pump 20 may also be referred to as primary sodium.

[0021] The secondary system pump 40 circulates the liquid metal and transfers the heat transmitted from the intermediate heat exchanger 30 to the steam generator 50. The secondary system pump 40 constitutes the secondary cooling system of the fast reactor S. The liquid metal in the secondary cooling system releases heat in the steam generator 50. Then, the secondary system pump 40 supplies the cooled liquid metal to the intermediate heat exchanger 30 and circulates it. In this embodiment, the liquid metal circulated by the primary system pump 20 may also be referred to as secondary sodium.

[0022] The steam generator 50 generates steam by the heat transmitted by the circulating liquid metal. The turbine 60 rotates a rotating body having a wheel, a rotor, etc. using the flow of the generated steam. In other words, the turbine 60 converts the flow of the generated steam into a mechanical rotational motion. The feed water pump 70 supplies the water obtained by liquefying the steam used in the turbine 60 to the steam generator 50 and circulates it. The generator 80 is a turbine generator that converts the rotational motion of the rotating body by the turbine 60 into electric power.

[0023] The control device 90 controls various parts within the fast reactor S. This allows the fast reactor S to function as a power-generating plant during steady-state operation. If any abnormality occurs, the fast reactor S will perform an emergency shutdown (reactor trip). For example, upon detecting an abnormality, the control device 90 supplies reactor trip signals to various parts, transitioning them to a shutdown state. The control device 90 is, for example, a computer such as a server or PC. The detailed structure and operation of such a fast reactor S are based on known technology, so a detailed explanation is omitted here.

[0024] The decay heat removal system 100 is activated upon receiving such a reactor trip signal and removes the decay heat generated in the core of the fast reactor S after the emergency shutdown operation has started, thereby cooling the core. The decay heat removal system 100 includes a temperature detector 110, an air cooler 120, a damper control unit 130, and a power supply unit 200.

[0025] The temperature detector 110 detects the temperature of the high-temperature primary sodium inside the main container 10. The temperature detector 110 is installed, for example, at the inlet of the primary sodium in the intermediate heat exchanger 30 and detects the temperature of the incoming primary sodium.

[0026] The air cooler 120 is installed in the secondary cooling system and cools the liquid metal (secondary sodium) circulated by the secondary system pump 40. The air cooler 120 has an inlet damper 121, an outlet damper 122, an outside air duct 123, and an AC motor. The inlet damper 121 is installed on the intake side of the outside air duct 123, which takes in and passes outside air, and the outlet damper 122 is installed on the exhaust side of the outside air duct 123. The inlet damper 121 and the outlet damper 122 are each provided with an AC motor, which will be described later. The rotation of the AC motor causes the corresponding damper to open and close.

[0027] The outside air duct 123 is equipped with a fan or the like so that outside air can be drawn in when the inlet damper 121 and outlet damper 122 open. In addition, liquid metal heat transfer tubes for circulating secondary sodium are provided inside the outside air duct 123.

[0028] This type of air cooler 120 takes in outside air by opening the inlet damper 121 and the outlet damper 122, and cools the circulating secondary sodium by removing heat from the liquid metal heat transfer tube with the taken-in outside air. In this embodiment, the inlet damper 121 and the outlet damper 122 are sometimes collectively referred to as the damper.

[0029] The damper control unit 130 supplies instruction signals to the air cooler 120 for opening and closing the damper. The damper control unit 130 supplies instruction signals to the air cooler 120 based, for example, on the temperature detection result of the temperature sensor 110. In response to receiving such instruction signals, the air cooler 120 drives the damper with an AC motor to open and close the damper. The damper control unit 130 may also supply instruction signals to the air cooler 120 to change the opening degree of the damper. The damper control unit 130 is, for example, a computer such as a server or PC. Alternatively, the damper control unit 130 may be a control circuit including a processor such as a CPU. The computer functions as the damper control unit 130 by executing a program stored in a memory unit or the like.

[0030] The power supply unit 200 supplies power to the loads within the decay heat removal system 100 (the loads may exclude fans). The power supply unit 200 may also supply power to loads used in the fast reactor S outside the decay heat removal system 100. First, an example of a conventional power supply unit 200 configuration will be explained using Figure 2.

[0031] <Example of a conventional power supply unit 200 configuration> Figure 2 shows an example of the configuration of a conventional power supply unit 200 for the decay heat removal system 100. The power supply unit 200 comprises a power bus 210, an extra-high voltage switchgear 220, a generator 230, an AC bus 240, a switch 250, and a compensation device 260. The power supply unit 200 shown in Figure 2 is an example of supplying power to the loads in the fast reactor S. The loads include a steady-state load 270 and an intermittent load 280.

[0032] The power busbar 210 is connected to an external power grid via an extra-high voltage switchgear 220, and can receive power from an external source. The extra-high voltage switchgear 220 functions as an extra-high voltage receiving device. In addition, one or more generators 230 are provided so as to be connectable to the power busbar 210. The power busbar 210 is a bus for transmitting power supplied from an external power source, generators 230, etc., to a load. The load is, for example, an AC motor for operating the damper of an air cooler 120.

[0033] The generator 230 is connected to the power bus 210 and supplies power to the load when the external power supply becomes unavailable due to some malfunction. Furthermore, a temporary generator 230a may be provided that is connected to the power bus 210 and supplies power when the generator 230 becomes unavailable due to some malfunction. The generator 230 is, for example, a diesel generator.

[0034] The AC bus 240 is connected to the power bus 210 and various loads, supplying power distributed from the power bus 210 to the various loads. The steady-state load 270 is a load that operates continuously, and the intermittent load 280 is a load that operates intermittently. The steady-state load 270 and the intermittent load 280 are, for example, power supplies for measurement and control devices and AC motors for damper drive.

[0035] The steady-state load 270 and the intermittent load 280 are connected to the AC bus 240 via a switch 250. The switch 250 electrically connects or disconnects the loads and the power bus 210 in response to instruction signals supplied, for example, from the damper control unit 130. The switch 250 may also be configured to switch the rotation direction of an AC motor if the load is an AC motor. This allows the damper to be opened and closed by supplying an instruction signal to the switch 250, which includes the rotation direction of the AC motor, from the damper control unit 130.

[0036] Figure 2 shows an example in which the damper control unit 130 instructs whether or not to connect the AC bus 240 to the intermittent load 280 and the steady load 270, but it is not limited to this. Alternatively, the control device 90 of the fast reactor S may instruct the connection of a portion of the load. In this case, the control device 90 may control the connection of a portion or all of the steady load 270, or the damper control unit 130 may control the connection of a portion or all of the intermittent load 280.

[0037] The power supply unit 200 shown in Figure 2 is an example in which an extra-high voltage switchgear 220, a generator 230, and an AC bus 240 are provided so that they can be connected to the power bus 210 via switches. In this case, for example, the control device 90 is configured to set whether or not to connect these components to the power bus 210 by supplying control signals to the switches.

[0038] As described above, the steady-state load 270 and the intermittent load 280 are started by direct-on-line starting, where the power supply voltage is applied directly from the AC bus 240. In this case, the load may experience a starting current of 8 to 10 times its rated value during startup. This starting current will be explained using Figure 3.

[0039] <An example of the power supply current supplied to the load> Figure 3 shows an example of the power supply current supplied to the load of the power supply unit 200. The horizontal axis of Figure 3 shows the elapsed time after the reactor trip signal is supplied to the decay heat removal system 100, and the vertical axis shows the power supply current supplied to the load of the power supply unit 200. Since power supply from the external power grid is no longer available, power is supplied to the load from the generator 230. The dotted line in the figure indicates the capacity of the generator 230.

[0040] The power supply current includes a current that is approximately constant over time due to the steady-state load 270 which operates continuously. In addition, the damper of the decay heat removal system 100 operates intermittently, for example, by opening fully at startup, and then repeatedly opening and closing or changing the opening degree depending on the amount of heat removed thereafter, so the AC motor operates intermittently. When driving such an intermittent load 280, the power supply current may intermittently flow to such an extent that it exceeds the capacity of the generator 230.

[0041] To cope with such large starting currents, possible solutions include installing a high-capacity generator or providing devices to compensate for the starting current at each individual load. Figure 2 shows an example where each load of the power supply unit 200 is equipped with a compensation device 260. The compensation devices 260 include star-delta starters, reactor starters, etc. Such starters are known as circuits that limit the starting current of the load, and a detailed explanation is omitted.

[0042] The decay heat removal system 100, using the power supply unit 200 described above, is activated in response to the reception of a reactor trip signal, and by lowering the temperature of the liquid metal, it removes the decay heat generated in the core 11 of the fast reactor S, thereby safely transitioning the fast reactor S to a low-temperature shutdown state.

[0043] However, the conventional power supply unit 200 shown in Figure 2 requires multiple compensation devices 260 for each load, resulting in a large system and high costs. While it is conceivable to replace the multiple compensation devices 260 with a large-capacity generator, this would still result in a larger system and higher costs. Furthermore, this could compromise portability. Therefore, the decay heat removal system 100 according to this embodiment aims to reduce costs by suppressing system size while responding to the load's starting current. The power supply unit used in such a decay heat removal system 100 will be described next.

[0044] <Example configuration of power supply unit 300> Figure 4 shows an example of the configuration of the power supply unit 300 according to this embodiment. The power supply unit 300 functions as a power source that supplies power to loads used in the fast reactor S, similar to the power supply unit 200 shown in Figure 2. In the power supply unit 300 according to this embodiment, components that are substantially the same as those in the conventional power supply unit 200 shown in Figure 2 are given the same reference numerals, and redundant explanations are omitted. The power supply unit 300 further comprises a storage battery 310, a charge / discharge switching unit 320, a current detection unit 330, and a charge / discharge control unit 340.

[0045] The battery 310 is connected to the power bus 210 and charges a portion of the power supplied from the external power source. If the battery 310 is unable to receive power from the external power source due to some malfunction, it will discharge the power it has stored for a predetermined period and supply it to the load. The predetermined period will be described later.

[0046] The charge / discharge switching unit 320 switches between charging and discharging the battery 310. For example, the charge / discharge switching unit 320 connects a converter that converts AC current from the power bus 210 to DC current to the battery 310, thereby charging the battery 310 with power supplied from the power bus 210. The charge / discharge switching unit 320 also connects an inverter that converts DC current from the battery 310 to AC current to the power bus 210, thereby discharging the power charged in the battery 310 back to the power bus 210.

[0047] The charge / discharge switching unit 320 switches between charging or discharging the battery 310 in accordance with the control signal received from the charge / discharge control unit 340. The charge / discharge switching unit 320 is configured to switch between a circuit that passes through the converter and a circuit that passes through the inverter using, for example, multiple switches.

[0048] The current detection unit 330 detects the magnitude of the power supply current flowing from the generator 230 to the AC motor, which is the load. Alternatively, the current detection unit 330 may detect the difference between the power supply current output from the generator 230 and the charging current that charges the battery 310 from the generator 230. The current detection unit 330 is, for example, an AC ammeter. Figure 4 shows an example in which the current detection unit 330 detects the magnitude of the power supply current flowing to the steady load 270 and the intermittent load 280. Here, the current detected by the current detection unit 330 is denoted as the input current Iin.

[0049] The charge / discharge control unit 340 controls the operation of the charge / discharge switching unit 320. In steady-state operation when power is supplied from an external power source, the charge / discharge control unit 340 transmits a control signal to the charge / discharge switching unit 320 to put it into a charging state. In emergency operation when power cannot be supplied from an external power source, the charge / discharge control unit 340 transmits a control signal to the charge / discharge switching unit 320 to switch it from a charging state to a discharging state and supply the charged power to the AC motor when operating the damper.

[0050] For example, the charge / discharge control unit 340 controls the operation of the charge / discharge switching unit 320 according to the detection result of the input current Iin by the current detection unit 330. In this case, the charge / discharge control unit 340 switches the charge / discharge switching unit 320 from the charging state to the discharging state if the magnitude of the current detected by the current detection unit 330 during emergency operation is greater than or equal to a predetermined value. Here, it is desirable that the predetermined value be set to a value smaller than the capacity value of the generator 230 and greater than the value of the current that flows steadily.

[0051] In an emergency operation where power cannot be supplied from an external power source, the input current Iin detected by the current detection unit 330 changes as shown in Figure 3. For example, when starting an AC motor, which is a load, a value greater than the normally flowing current flows. Therefore, the charge / discharge control unit 340 supplies power charged by the battery 310 to the load in response to the current detection unit 330 detecting an input current Iin greater than a predetermined value. As a result, the power supply unit 300 can compensate for power exceeding the capacity of the generator 230 from the battery 310.

[0052] With this power supply unit 300, the compensation operation by the compensation device 260 described in Figure 2 becomes unnecessary, and the compensation device 260 can be omitted, reducing the size and cost of the device. Furthermore, with the power supply unit 300, it is not necessary to increase the capacity of the generator 230, thus reducing the size and cost of the device while maintaining portability.

[0053] As shown in Figure 3, when the AC motor load is started, the input current Iin decreases in a short time and returns to a steady-state current value. Therefore, the charge / discharge control unit 340 switches the charge / discharge switching unit 320 from the charging state to the discharging state, and then, if the magnitude of the current detected by the current detection unit 330 falls below a predetermined value, it switches the charge / discharge switching unit 320 from the discharging state to the charging state. As a result, the power supply unit 300 reduces the power discharged by the battery 310, so that even if the emergency operation state of the fast reactor S continues, the battery 310 can be used to perform compensatory operation in response.

[0054] Alternatively, or in addition to the above, the charge / discharge control unit 340 may switch the charge / discharge switching unit 320 from the discharge state to the charge state after a predetermined time has elapsed since switching the charge / discharge switching unit 320 from the charge state to the discharge state. Since the period during which the AC motor, which is the load, is operating (the time from the start to the end of the damper's opening and closing operation) can be set in advance, by making the predetermined time longer than this period, the charge / discharge control unit 340 can appropriately switch the storage battery 310 to the charge state.

[0055] As described above, the power supply unit 300 according to this embodiment can reduce costs while responding to the starting current of the load. Furthermore, although an example of the power supply unit 300 being used in a fast reactor S has been described in this embodiment, it is not limited to this. The power supply unit 300 can be used in systems, plants, etc., that switch to an emergency generator to start the load when power supply from the power source becomes unavailable.

[0056] In the power supply device 300 according to this embodiment, an example has been described in which the charge / discharge control unit 340 controls the operation of the charge / discharge switching unit 320 according to the detection result of the current detection unit 330, but it is not limited to this. The power supply device 300 may also control the operation of the charge / discharge switching unit 320 according to an instruction signal that instructs the opening and closing of the damper.

[0057] In this case, the power supply unit 300 further includes a receiving unit that receives an instruction signal from the damper control unit 130 of the decay heat removal system 100 to operate the damper. The charge / discharge control unit 340 then switches the charge / discharge switching unit 320 from the charging state to the discharging state when the receiving unit receives an instruction signal indicating that the damper should be operated during emergency operation. In a power supply unit 300 with this configuration, the current detection unit 330 may be omitted. Even with the power supply unit 300 described above, as mentioned above, it is possible to reduce costs while still being able to handle the starting current of the load.

[0058] The power supply unit 300 according to this embodiment performs compensation operation using the battery 310 based on changes in the input current Iin, reception of instruction signals, etc. This allows the power supply unit 300 to easily perform compensation using the battery 310 in response to the intermittent operation of the damper, for which it is difficult to predict when to operate. In addition to opening and closing the damper, the decay heat removal system 100 may also finely adjust the opening degree of the damper.

[0059] <An example of changes in primary sodium temperature, damper operating state, and input current Iin> Figure 5 shows an example of the relationship between the temperature of the primary sodium in the fast reactor S according to this embodiment, the operating state of the damper, and the change in the input current Iin. The horizontal axis of Figure 5 shows the elapsed time after the reactor trip signal is supplied to the decay heat removal system 100. The vertical axis of Figure 5(a) shows the temperature of the primary sodium detected by the temperature detector 110. The vertical axis of Figure 5(b) shows the opening degree of the inlet damper 121 and the outlet damper 122. The damper opening degrees include fully closed, fully open, and an intermediate opening state between the fully closed and fully open states. The vertical axis of Figure 5(c) shows the magnitude of the input current Iin detected by the current detection unit 330.

[0060] Figure 5 shows an example where some abnormality occurs at time 0, and an emergency shutdown operation of the reactor is initiated. In this case, at time 0, the damper control unit 130 receives a reactor trip signal from the control device 90. Then, in response to the switch from steady-state operation to emergency operation, the damper control unit 130 sets the damper opening to a predetermined first opening. The first opening is, for example, the fully open state.

[0061] In this case, at time 0, the damper control unit 130 sends an instruction signal to the air cooler 120 to fully open the damper. As a result, the AC motor, which is an intermittent load 280, is driven, and the input current Iin rises to exceed the capacity of the generator 230. However, the power supply unit 300 performs a compensation operation using the storage battery 310 based on this input current Iin or instruction signal, so that the AC motor can be operated stably and the damper can be fully opened.

[0062] Then, the input current Iin decreases to a value less than the capacity of the generator 230, and the power supply 300 returns the battery 310 to a charged state and ends the compensation operation. As a result, the temperature of the primary sodium decreases. Figure 5 shows an example in which the temperature of the primary sodium decreases at a predetermined rate. It is desirable that the cooling performance of the air cooler 120 with the damper fully open be preset so that the temperature of the primary sodium decreases stably.

[0063] Then, when the temperature of the liquid metal drops below a predetermined first temperature, the damper control unit 130 sets the damper opening to a second opening, which is smaller than the first opening. Here, the first temperature is, for example, the temperature at which the fast reactor S enters a warm shutdown state. In the example in Figure 5, four hours have elapsed from time 0, and the temperature of the primary sodium is below the first temperature, so the damper control unit 130 sends an instruction signal to the air cooler 120 to set the damper to the first intermediate opening.

[0064] As a result, the input current Iin rises to exceed the capacity of the generator 230, but as described above, the power supply 300 performs a compensation operation using the battery 310, so that the AC motor can operate stably and the damper can be set to the first intermediate opening. Then, the input current Iin decreases to a value less than the capacity of the generator 230, and the power supply 300 returns the battery 310 to a charged state and ends the compensation operation.

[0065] This allows the decay heat removal system 100 to slow down the decrease in the temperature of the primary sodium. In this case, it is desirable that the first intermediate opening of the damper be set in advance so that the temperature of the primary sodium remains at a nearly constant value. Figure 5 shows an example of a warm-state shutdown where the temperature of the primary sodium remains at a nearly constant value.

[0066] Then, after a predetermined time has elapsed since the damper was opened to the second degree, the damper opening is increased beyond the second degree. In the example shown in Figure 5, even after more than 10 hours have passed since the damper was opened to the first intermediate degree, the temperature of the primary sodium remains stable with almost no change from the temperature at which the damper was opened to the first intermediate degree. Next, at 14.5 hours after time 0, the damper control unit 130 sends an instruction signal to the air cooler 120 to open the damper from the first intermediate degree to the fully open state.

[0067] As a result, the input current Iin rises to exceed the capacity of the generator 230, but as described above, the power supply 300 performs a compensation operation using the battery 310, allowing the AC motor to operate stably and the damper to be fully open. Then, the input current Iin decreases to a value less than the capacity of the generator 230, and the power supply 300 returns the battery 310 to a charged state and ends the compensation operation. This further reduces the temperature of the primary sodium. Figure 5 shows an example in which the temperature of the primary sodium is reduced at a predetermined rate.

[0068] Then, when the temperature of the liquid metal drops below a predetermined second temperature, the damper control unit 130 sets the damper opening to a third opening, which is smaller than the first opening. Here, the predetermined second temperature is, for example, the temperature at which the fast reactor S enters a low-temperature shutdown state. In the example in Figure 5, 21 hours have elapsed from time 0, and the temperature of the primary sodium is below the second temperature, so the damper control unit 130 sends an instruction signal to the air cooler 120 to set the damper to the second intermediate opening.

[0069] As a result, the input current Iin rises to exceed the capacity of the generator 230, but as described above, the power supply 300 performs compensation operation using the battery 310, allowing the AC motor to operate stably and the damper to the second intermediate opening. Then, the input current Iin decreases to a value less than the capacity of the generator 230, and the power supply 300 returns the battery 310 to a charged state and ends the compensation operation. In this case, it is desirable that the second intermediate opening of the damper be set in advance so that the temperature of the primary sodium remains at a nearly constant value. Figure 5 shows an example in which the decay heat removal system 100 brings the temperature of the primary sodium to a nearly constant low-temperature stop state.

[0070] As described above, the decay heat removal system 100 according to this embodiment can more safely bring the fast reactor S to a low-temperature shutdown state by finely adjusting the damper opening degree and intermittently opening and closing the damper. The power supply unit 200 can perform compensation operations corresponding to the operation of the decay heat removal system 100 by switching the power supply from the storage battery 310 to the AC motor in response to the operation of the damper by the damper control unit 130.

[0071] Although the power supply device 300 according to this embodiment has been described in an example where it performs compensation operation using a storage battery 310, it is not limited to this. In addition, the storage battery 310 may also supply power to the load on a steady basis. For example, if a malfunction occurs in the generator 230, the generator 230 may be replaced with a temporary generator 230a or the like. In an emergency operation where power cannot be supplied from an external power source, if such a malfunction of the generator 230 occurs, the power supply device 300 will be unable to supply power to the load.

[0072] Therefore, during the period when generator 230 is replaced with a temporary generator 230a, the charge / discharge control unit 340 discharges from the storage battery 310 to supply power to the load steadily. This ensures that even if generator 230 fails during emergency operation, power can be supplied to the load, and the fast reactor S can be safely brought to a low-temperature shutdown state.

[0073] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of its gist. For example, all or part of the apparatus can be configured by functionally or physically distributing and integrating in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combinations are combined with the effects of the original embodiments. [Explanation of symbols]

[0074] 10 Main container 11 Core 20 Primary system pump 30 Intermediate heat exchanger 40 Secondary system pump 50 Steam generator 60 Turbine 70 Water supply pump 80 Generators 90 Control device 100 Decay Heat Removal Systems 110 Temperature Detector 120 Air Cooler 121 Entrance Damper 122 Outlet damper 123 Outdoor air duct 130 Damper Control Unit 200 Power supply 210 Power busbar 220 Extra-high voltage switchgear 230 Generators 240 AC busbar 250 switches 260 Compensation device 270 Steady load 280 Intermittent load 300 power supply 310 Battery 320 Charge / discharge switching section 330 Current detection unit 340 Charge / Discharge Control Unit

Claims

1. A power supply unit for a decay heat removal system that has an air cooler for cooling circulating liquid metal, and uses the liquid metal to cool decay heat generated in the core of a fast reactor, It is provided to be connectable to an external power grid, and includes a power bus for transmitting power supplied from an external power source to an AC motor for operating the damper of the air cooler, An AC bus connected to the aforementioned power bus and the aforementioned AC motor, which supplies power distributed from the power bus to the AC motor, A generator is provided so as to be connectable to the aforementioned power busbar, and in the event that power cannot be supplied from the external power source, it supplies power to the AC motor via the aforementioned AC busbar. A storage battery is provided so as to be connectable to the aforementioned power busbar, and is used to charge a portion of the power supplied from the external power source. A charge / discharge switching unit for switching between charging and discharging the aforementioned storage battery, A charge / discharge control unit that controls the operation of the charge / discharge switching unit, A converter that converts alternating current to direct current, An inverter that converts direct current to alternating current, A current detection unit is provided between the power bus and the AC bus to detect the magnitude of the current flowing from the generator to the AC motor, Equipped with, The charge / discharge control unit, In steady-state operation where power is supplied from the external power source, the converter that converts the AC current from the power bus to a DC current is connected to the storage battery, thereby putting the charge / discharge switching unit into a charging state. In an emergency operation where power cannot be supplied from the external power source, if the damper is operated and the magnitude of the current detected by the current detection unit is greater than or equal to a predetermined value, the inverter that converts the DC current from the storage battery to AC current is connected to the power bus, and the charge / discharge switching unit is switched from the charging state to the discharging state to supply the charged power to the AC motor. power supply.

2. In an emergency operation where power cannot be supplied from the external power source, if the generator fails, the charge / discharge control unit connects the inverter, which converts the DC current from the storage battery to the AC current, to the power bus and discharges the storage battery to supply power to the AC motor on a steady basis. The power supply device according to claim 1.

3. The power supply device according to claim 2, wherein the charge / discharge control unit switches the charge / discharge switching unit from a charging state to a charging state, and then, if the magnitude of the current detected by the current detection unit falls below a predetermined value, the charge / discharge switching unit switches the charge / discharge switching unit from a discharging state to a charging state.

4. The system further includes a receiving unit that receives an instruction signal from the aforementioned decay heat removal system to operate the damper, The charge / discharge control unit switches the charge / discharge switching unit from the charging state to the discharging state when the receiving unit receives an instruction signal indicating that the damper should be operated during the emergency operation. The power supply device according to claim 1.

5. The power supply device according to claim 4, wherein the charge / discharge control unit switches the charge / discharge switching unit from a discharge state to a charge state after a predetermined time has elapsed since switching the charge / discharge switching unit from a charge state to a discharge state.

6. A decay heat removal system for cooling the decay heat generated in the core of the fast reactor, A temperature detector for detecting the temperature of the liquid metal circulating in the core of the fast reactor, The air cooler includes the damper and the AC motor, and by opening the damper, it takes in outside air and circulates it to cool the liquid metal, A damper control unit supplies an instruction signal to the air cooler to open and close the damper based on the temperature detection result of the temperature detector, A power supply device according to any one of claims 1 to 5, which switches the supply of power from the storage battery to the AC motor in accordance with the operation of the damper by the damper control unit, A decay heat removal system equipped with the following features.

7. The decay heat removal system according to claim 6, wherein the damper control unit sets the opening degree of the damper to a predetermined first opening degree in response to a switch from steady-state operation to emergency operation.

8. The decay heat removal system according to claim 7, wherein the damper control unit, when the temperature of the liquid metal falls below a predetermined first temperature, sets the opening of the damper to a second opening, which is smaller than the first opening.

9. The decay heat removal system according to claim 8, wherein the damper control unit increases the opening of the damper to a degree greater than the second opening when a predetermined time has elapsed after the damper has been opened to the second opening.

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