JP2014174138A - Operation method of fast reactor decay heat removal system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation method of a fast reactor decay heat removal system which is capable of stabilizing primary coolant in a reactor vessel at a level close to appropriate temperature in the case of loss of power source.SOLUTION: A fast reactor decay heat removal system comprises: a first direct reactor core cooling system 5 of a forced air cooling type; a second direct reactor core cooling system 6 of a natural air cooling type; and a reactor vessel cooling system 7 of a natural air cooling type. The second direct reactor core cooling system 6 is configured so that heat-removing capability is higher than that of the first direct reactor core cooling system 5 in the case where a cooling fan 11 is stopped. The reactor vessel cooling system 7 is configured so that heat-removing capability is lower than that of the second direct reactor core cooling system 6. In an operation method of such a fast reactor decay heat removal system, the second direct reactor core cooling system 6 is activated in addition to the first direct reactor core cooling system 5 in the case of the state of loss of power source, and then, when the temperature of the primary coolant in the reactor vessel 2 drops to a predetermined value Tb, the second direct reactor core cooling system 6 is stopped, and the reactor vessel cooling system 7 is activated.

Description

  The present invention relates to a decay heat removal system that removes decay heat of core fuel when an abnormality occurs in a fast reactor, and more particularly to an operation method of a fast reactor decay heat removal system.

  The Fast Reactor (FS) is equipped with a decay heat removal system that removes the decay heat of the core fuel when an abnormality occurs for the principle of ensuring safety. As a component of this decay heat removal system, a direct reactor cooling system (DRACS) that cools a primary coolant in a reactor vessel is known (see, for example, Non-Patent Document 1).

  The direct core cooling system described in Non-Patent Document 1 includes a heat removal unit, a heat radiation unit located above the heat removal unit, and a heat transport pipe connecting the heat removal unit and the heat radiation unit. . Then, the working fluid naturally circulates between the heat removal unit and the heat radiation unit. If it demonstrates in detail, the heat removal part will be immersed in the primary coolant in a reactor vessel. In this heat removal unit, the primary coolant in the reactor vessel is cooled by heat exchange between the primary coolant (sodium) in the reactor vessel and the working fluid, and the working fluid is heated. In the heat radiating portion, the working fluid is cooled by the cooling air induced by the cooling fan. And natural convection arises by the density change accompanying the temperature change of a working fluid, and a working fluid circulates naturally.

Masao Hori, “Basic Fast Reactor Engineering”, Nikkan Kogyo Shimbun, October 1993, p. 105-107

  In the direct core cooling system described above, the heat removal capability can be varied by variably controlling the rotation speed of the cooling fan. Then, by changing the heat removal capability according to the elapse of the cooling time (that is, according to the temperature drop of the primary coolant in the reactor vessel), the primary coolant in the reactor vessel is adjusted to an appropriate temperature (details). Can be stabilized in the vicinity of a temperature slightly higher than the freezing point of sodium. However, if the power supply is lost due to an unexpected situation, the cooling fan cannot be driven, so the heat removal capability is reduced. Therefore, as one of the improvement measures, it is conceivable to provide another cooling system for directly or indirectly cooling the primary coolant in the reactor vessel so as to supplement the heat removal capability when the power source is lost. However, since the heat removal capability of each cooling system cannot be changed when the power source is lost, there is room for further improvement in terms of stabilizing the primary coolant in the reactor vessel near an appropriate temperature.

  The present invention has been made in view of the above matters, and its purpose is to collapse the fast reactor in which the primary coolant in the reactor vessel can be stabilized in the vicinity of an appropriate temperature when the power supply is lost. The object is to provide a method of operating a heat removal system.

  In order to achieve the above object, the first invention cools the primary coolant in the reactor vessel of the fast reactor with a naturally circulating working fluid and cools the working fluid when the power supply is not lost. The first direct core cooling system that is cooled by cooling air generated by a fan and the primary coolant in the reactor vessel are cooled by a naturally circulating working fluid, and the working fluid is cooled by natural convection of air. A second direct core cooling system, and a reactor vessel cooling system that cools the outside of the reactor vessel by natural convection of air, and the second direct core cooling system is configured so that the cooling fan is stopped. It is configured such that the heat removal capability of the primary coolant in the reactor vessel is higher than that of the first direct core cooling system, and the reactor vessel cooling system is more reliable than the second direct core cooling system. Inside An operating method of a fast reactor decay heat removal system configured to reduce the heat removal capability for the primary coolant, and when the power supply is lost, in addition to the first direct core cooling system, Two direct core cooling systems are started, and then, when the temperature of the primary coolant in the reactor vessel is reduced to a predetermined value, the second direct core cooling system is stopped and the reactor vessel cooling system is started. .

  In order to achieve the above object, the second invention cools the primary coolant in the reactor vessel of the fast reactor with a naturally circulating working fluid and cools the working fluid when the power supply is not lost. The first direct core cooling system that is cooled by cooling air generated by a fan and the primary coolant in the reactor vessel are cooled by a naturally circulating working fluid, and the working fluid is cooled by natural convection of air. A second direct core cooling system, and a chassis cooling system that cools the enclosure provided outside the reactor containment vessel containing the reactor vessel with a naturally circulating working fluid and cools the working fluid with seawater. The second direct core cooling system has a higher heat removal capability for the primary coolant in the reactor vessel than the first direct core cooling system when the cooling fan is stopped. The enclosure cooling system is an operating method of a fast reactor decay heat removal system configured to have a lower heat removal capability for the primary coolant in the reactor vessel than the second direct core cooling system. When the power supply is lost, the second direct core cooling system is started in addition to the first direct core cooling system, and then the temperature of the primary coolant in the reactor vessel reaches a predetermined value. If it falls, while stopping said 2nd direct core cooling system, said housing cooling system is started.

  In order to achieve the above object, the third invention cools the primary coolant in the reactor vessel of the fast reactor with a naturally circulating working fluid and cools the working fluid when the power supply is not lost. The first direct core cooling system that is cooled by cooling air generated by a fan and the primary coolant in the reactor vessel are cooled by a naturally circulating working fluid, and the working fluid is cooled by natural convection of air. A second direct core cooling system, a reactor vessel cooling system that cools the outside of the reactor vessel by natural convection of air, and a housing provided outside the reactor containment vessel that houses the reactor vessel, And a cooling system that cools the working fluid with seawater, and the second direct core cooling system includes the first direct reactor when the cooling fan is stopped. The reactor system is configured to have a higher heat removal capability for the primary coolant in the reactor vessel than the cooling system, and the reactor vessel cooling system and the enclosure cooling system are more reliable than the second direct core cooling system. An operation method of a fast reactor decay heat removal system configured to reduce the total heat removal capacity of the primary coolant in the vessel, and when the power is lost, the first direct core cooling system is In addition, when the temperature of the primary coolant in the reactor vessel is lowered to a predetermined value after starting the second direct core cooling system, the second direct core cooling system is stopped and the reactor vessel Start the cooling system and the enclosure cooling system.

  According to the present invention, when the power supply is lost, the primary coolant in the reactor vessel can be stabilized near the appropriate temperature.

1 is a schematic diagram showing a configuration of a fast reactor decay heat removal system in a first embodiment of the present invention. FIG. 2 is a diagram showing a temperature change of a primary coolant in a reactor vessel in order to explain an operating method of the fast reactor decay heat removal system and its operation and effects in the first embodiment of the present invention. It is the schematic showing the structure of the fast reactor decay heat removal system in the 2nd Embodiment of this invention. It is the schematic showing the structure of the housing cooling system in the 2nd Embodiment of this invention. It is a figure showing the temperature change of the primary coolant in a reactor vessel in order to demonstrate the operating method of the fast reactor decay heat removal system in the 2nd Embodiment of this invention, and its effect. It is the schematic showing the structure of the fast reactor decay heat removal system in the 3rd Embodiment of this invention. It is a figure showing the temperature change of the primary coolant in a reactor vessel in order to demonstrate the operating method of the fast reactor decay heat removal system in the 3rd Embodiment of this invention, and its effect. It is the schematic showing the structure of the fast reactor decay heat removal system in the 1st modification of this invention. It is the elements on larger scale of the IX section in FIG. It is a pipe radial direction sectional view showing the structure of the 2nd direct core cooling system in the 2nd modification of the present invention. It is the schematic showing the structure of the fast reactor decay heat removal system in the 3rd modification of this invention.

  First, the specific example of the principal part structure of the fast reactor which is an application object of this invention is demonstrated.

  A reactor containment vessel (not shown) is accommodated in the reactor building 1, and a reactor vessel 2 and an intermediate heat exchanger (not shown) are accommodated in the reactor containment vessel (FIG. 4 described later). reference). The nuclear reactor vessel 2 contains a core 3 containing nuclear fuel (see FIGS. 4 and 1 described later).

  Further, a primary system pipe and a primary system circulation pump (not shown) for circulating a primary coolant (sodium) between the reactor vessel 2 and the intermediate heat exchanger are provided. The primary coolant is heated by the core 3 in the reactor vessel 2 and supplied to the intermediate heat exchanger via the high temperature side pipe 4A (see FIG. 1 and the like described later). The primary coolant is cooled by exchanging heat with the secondary coolant (sodium) in the intermediate heat exchanger, and returned to the reactor vessel 2 through the low temperature side pipe 4B (see FIG. 1 and the like described later). It has become.

  Moreover, although not shown in figure, the main steam system is accommodated in the turbine building. The main steam system includes a steam generator for evaporating water, a high-pressure turbine driven by steam from the steam generator, a low-pressure turbine driven by steam from the high-pressure turbine, and steam discharged from the low-pressure turbine. And a feed water pump and a feed water heater provided in a feed water line for supplying water from the condenser to the steam generator. Moreover, the generator connected to the rotating shaft of a high pressure turbine and a low pressure turbine is provided.

  Further, although not shown, a secondary system pipe and a secondary system circulation pump for circulating the secondary coolant between the intermediate heat exchanger and the steam generator are provided. The secondary coolant is heated by exchanging heat with the primary coolant in the intermediate heat exchanger, and supplied to the steam generator. In addition, the secondary coolant is cooled by exchanging heat with water in a steam generator and returned to the intermediate heat exchanger.

  The fast reactor described above is equipped with a decay heat removal system that removes decay heat of the core fuel when an abnormality occurs for the principle of ensuring safety. The configuration of the fast reactor decay heat removal system in the first embodiment of the present invention will be described with reference to FIG.

  The fast reactor decay heat removal system of the present embodiment includes a forced air cooling type first direct core cooling system 5, a natural air cooling type second direct core cooling system 6, and a natural air cooling type reactor vessel cooling system (RVACS: Reactor Vessel Auxiliary Cooling System) 7. In the present embodiment, only one second direct core cooling system 6 is provided, but a plurality of second direct core cooling systems 6 may be provided.

  The first direct core cooling system 5 includes a heat removal unit 8, a heat radiation unit 9 positioned above the heat removal unit 8, and a heat transport pipe 10 connecting the heat removal unit 8 and the heat radiation unit 9. ing. The working fluid is naturally circulated between the heat removal unit 8 and the heat radiation unit 9.

  More specifically, the heat removal unit 8 is immersed in a primary coolant in the reactor vessel 2. In the heat removal unit 8, the primary coolant in the reactor vessel 2 is cooled by heat exchange between the primary coolant in the reactor vessel 2 and the working fluid, and the working fluid is heated. The heat dissipating part 9 is arranged in an air duct (not shown) provided outside the reactor building 1. In the heat radiating portion 9, the working fluid is cooled by the cooling air induced by the cooling fan 11 when the power source is not lost. And natural convection arises by the density change accompanying the temperature change of a working fluid, and a working fluid circulates naturally.

  The final heat sink of the first direct core cooling system 5 is the atmosphere. The air duct described above is provided with a damper (not shown) that can be opened and closed, and the first direct core cooling system 5 can be switched between operation and stop by opening and closing the damper. Further, an inverter device (not shown) that variably controls the rotation speed of the cooling fan 11 is provided. When the power source is not lost, the heat removal capability of the first direct core cooling system 5 can be varied by variable control of the rotation speed of the cooling fan 11.

  The second direct core cooling system 6 includes a heat pipe 14 having a lower end side evaporation unit 12 and an upper end side condensing unit 13, and a working fluid is enclosed in the heat pipe 14. The working fluid is naturally circulated between the evaporation unit 12 and the condensing unit 13.

  More specifically, the evaporating unit 12 is immersed in the primary coolant in the reactor vessel 2 in the same manner as the heat removal unit 8 of the first direct core cooling system 5. In the evaporation section 12, the primary coolant in the reactor vessel 2 is cooled by heat exchange between the primary coolant in the reactor vessel 2 and the working fluid, and the working fluid is heated and evaporated. The condensing unit 13 is disposed in an air duct (not shown) provided outside the reactor building 1. In the condensing unit 13, the working fluid is cooled and condensed by natural convection of air. The condensing unit 13 is provided with a large number of radiating fins 15 in order to increase the cooling capacity. The working fluid circulates naturally due to the change in specific gravity accompanying the phase change of the working fluid.

  The final heat sink of the second direct core cooling system 6 is the atmosphere. The air duct described above is provided with a damper (not shown) that can be opened and closed, and the opening and closing of the damper enables switching between operation and stop of the second direct core cooling system 6. In this embodiment, a gravity heat pipe that does not have a wick (capillary structure) on the inner wall of the pipe is employed, but a pipe having a wick may be employed.

  The reactor vessel cooling system 7 is configured to cool the outside of the reactor vessel 2 by natural convection of air.

  More specifically, a guard vessel 18 having double cylindrical flow paths 16A and 16B and a lower plenum 17 that communicates the lower side of the cylindrical flow paths 16A and 16B is provided outside the reactor vessel 2. ing. And since temperature falls as it goes to the radial direction outer side of the reactor vessel 2, the temperature difference has arisen between the outer side flow path 16A and the inner side flow path 16B. Natural convection occurs due to the difference in air density associated with this temperature difference. That is, air having a relatively low temperature and high density flows into the outer flow path 16A and descends, and thereafter, air having a relatively high temperature and a low density rises and flows out in the inner flow path 16B. The reactor vessel 2 is cooled by such natural convection of air.

  In addition, air ducts for introducing air from the outside of the reactor building 1 to the outer flow path 16A and leading the air from the inner flow path 16B to the outside of the reactor building 1 using the natural convection of air described above ( (Not shown) is provided. That is, the heat sink of the reactor vessel cooling system 7 is the atmosphere. The air duct described above is provided with a damper (not shown) that can be opened and closed, and the operation and stop of the reactor vessel cooling system 7 can be switched by opening and closing the damper.

  The heat removal capacity of the first direct core cooling system 5 with respect to the primary coolant in the reactor vessel 2 is stopped when the cooling fan 11 is driven at the maximum rotational speed to a reference value (100%). In this case, for example, it is reduced to 30% of the reference value. The heat removal capacity of the second direct core cooling system 6 with respect to the primary coolant in the reactor vessel 2 is higher than the heat removal capacity (30%) of the first direct core cooling system 5 when the cooling fan 11 is stopped, for example, This corresponds to 120% of the reference value. The heat removal capability of the reactor vessel cooling system 7 for the primary coolant in the reactor vessel 2 is lower than the heat removal capability (120%) of the second direct core cooling system 6 and corresponds to, for example, 50% of the reference value.

  Next, an operation method of the fast reactor decay heat removal system and its operation and effects in this embodiment will be described with reference to FIG. The horizontal axis in FIG. 2 represents the number of days after the occurrence of an abnormality in the fast reactor, and the vertical axis represents the temperature of the primary coolant in the reactor vessel 2. The primary coolant (sodium) has a boiling point of about 1108K and a freezing point of about 373K. Therefore, considering that the primary coolant is not boiled or solidified, an appropriate range of the temperature of the primary coolant in the reactor vessel 2 after the occurrence of abnormality is, for example, 400K or more and 900K or less. In addition, the temperature of the primary coolant in the reactor vessel 2 during normal operation is, for example, about 700 K, and considering that the temperature is lower than this temperature, the temperature of the primary coolant in the reactor vessel 2 after the occurrence of an abnormality The appropriate range is, for example, 400K or more and 700K or less. Further, considering that the load on the equipment is reduced, the final appropriate temperature (target temperature) of the primary coolant is slightly higher than the freezing point of sodium (specifically, for example, a temperature between 450 to 500K). ).

  When an abnormality occurs in the fast reactor, the core fuel emits decay heat of about several percent of the heat output during normal operation, so the primary coolant in the reactor vessel 2 is heated. In order to cool the primary coolant in the reactor vessel 2, the damper is operated to activate the first direct core cooling system 5. At this time, when the power loss state (SBO: Station Blackout) does not occur, the heat removal capability of the first direct core cooling system 5 can be varied from 100% to 30% by variable control of the rotation speed of the cooling fan 12. . Then, as the cooling time elapses, that is, as the temperature of the primary coolant in the reactor vessel 2 decreases, the heat removal capability of the first direct core cooling system 5 is reduced, so that the inside of the reactor vessel 2 The primary coolant can be stabilized in the vicinity of the appropriate temperature (see the alternate long and short dash line U in FIG. 2).

  On the other hand, if the power supply is lost due to unforeseen circumstances, the cooling fan 12 cannot be driven, so that the heat removal capability of the first direct core cooling system 5 is limited to 30%, resulting in insufficient cooling. That is, the temperature of the primary coolant in the reactor vessel 2 rises (see the two-dot chain line S in FIG. 2). In this case, even if the temperature of the primary coolant is finally suppressed to 900K or less, the load on the facility increases.

  Therefore, in this embodiment, for example, the temperature of the primary coolant in the reactor vessel 2 measured by a thermometer (not shown) is a predetermined value Ta (specifically, the primary temperature in the reactor vessel 2 during normal operation). When the value is set in advance so as to be slightly higher than the temperature of the coolant and rises to, for example, 800 K), the second direct core cooling system 6 is started by operating the damper. Thereby, the sum total of the heat removal capability of the cooling system is 150%. Therefore, as the cooling time elapses, the temperature of the primary coolant in the reactor vessel 2 decreases (see the solid line (S + A) in FIG. 2). However, even if the cooling time elapses to some extent, if the operation of the first direct core cooling system 5 and the second direct core cooling system 6 is continued as it is, overcooling occurs. That is, the temperature of the primary coolant may be less than 400K.

  Therefore, in this embodiment, for example, the temperature of the primary coolant in the reactor vessel 2 measured by a thermometer is a predetermined value Tb (specifically, a first direct core cooling system 5 and a reactor vessel cooling system 7 described later). In consideration of the sum of the heat removal capacities, the second direct core cooling system 6 is stopped by operating the damper and the damper is operated. The reactor vessel cooling system 7 is activated. Thereby, the sum total of the heat removal capability of the cooling system becomes 80%. As a result, the primary coolant in the reactor vessel 2 can be stabilized in the vicinity of an appropriate temperature (see the solid line (S + B) in FIG. 2).

  The second direct core cooling system 6 will be described supplementarily. The working fluid of the second direct core cooling system 6 employs any one of a liquid metal, a liquid system, a heat medium system, a solvent system, and an inert gas system. Specific examples of the liquid metal include sodium, cesium, rubidium, lithium, and sodium potassium alloy. Specific examples of the liquid system include water and methanol. Specific examples of the heat transfer medium include Dowtherm. Specific examples of the solvent system include naphthalene and phenol. Specific examples of the inert gas system include nitrogen and helium. Water and cesium have high performance, dowtherm and phenol have medium performance, and naphthalene has low performance. When liquid metal is used, it has the advantage of large latent heat of vaporization and is inactive to the primary coolant, so that even if the second direct core cooling system 6 is damaged, there is a problem. Has the advantage that does not occur.

  It is preferable that the heat removal capacity of the second direct core cooling system 6 is rapidly improved when the primary coolant in the reactor vessel 2 rises to a predetermined value Ta (800 K). Moreover, when the primary coolant in the reactor vessel 2 is reduced to 400K, it is preferable that the temperature is rapidly decreased. Therefore, the saturation temperature H of the working fluid in the second direct core cooling system 6 is preferably set so as to satisfy the condition of 800K ≧ H ≧ 400K.

  The configuration of the fast reactor decay heat removal system in the second embodiment of the present invention will be described with reference to FIGS. 3 and 4, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The fast reactor decay heat removal system of the present embodiment includes a forced air cooling type first direct core cooling system 5, a natural air cooling type second direct core cooling system 6, and a natural water cooling type enclosure cooling system 19. Yes.

  The enclosure cooling system 19 is configured to cool the enclosure 20 provided outside the reactor containment vessel with a naturally circulating working fluid and cool the working fluid with seawater.

  If it demonstrates in detail, the frame 20 will be comprised, for example so that concrete may be included with a stainless plate, and has played the role as a guard vessel. A plurality of annular lower headers 21, annular upper headers 22, and a plurality of vertical headers connected between the lower headers 21 and the upper headers 22 inside the cylindrical side wall portion of the housing 20. A cooling channel 23 is formed. In addition, a water tank 24 for storing seawater is provided outside the reactor building 1, and a heat exchanger 25 is installed in the water tank 24. A pipe 26 </ b> A for leading the working fluid from the heat exchanger 25 to the lower header 21 and a pipe 26 </ b> B for leading the working fluid from the upper header 22 to the heat exchanger 25 are provided. And the working fluid in the housing lower header 21, the cooling flow path 23, and the upper header 22 cools the housing 20, and the temperature rises. On the other hand, the working fluid in the heat exchanger 25 is cooled by seawater, and its temperature falls. The natural convection is generated by the density change accompanying the temperature change of the working fluid, and the working fluid is naturally circulated.

  Further, a valve (not shown) is provided in the piping 26A and / or 26B, and the operation / stop of the housing cooling system 19 can be switched by opening and closing the valve. Further, the water storage tank 24 communicates with the sea 28 via communication pipes 27A and 27B arranged above and below. Thereby, seawater naturally circulates between the reservoir 24 and the sea 28. That is, the final heat sink of the enclosure cooling system 19 is seawater.

  As in the first embodiment, the heat removal capability of the first direct core cooling system 5 with respect to the primary coolant in the reactor vessel 2 is the reference value (100%) when the cooling fan 11 is driven at the maximum rotational speed. If it takes, when the cooling fan 11 stops, it will fall, for example to 30% of a reference value. The heat removal capacity of the second direct core cooling system 6 with respect to the primary coolant in the reactor vessel 2 is higher than the heat removal capacity (30%) of the first direct core cooling system 5 when the cooling fan 11 is stopped, for example, This corresponds to 120% of the reference value.

  The heat removal capacity of the enclosure cooling system 19 with respect to the primary coolant in the reactor vessel 2 is lower than the heat removal capacity (120%) of the second direct core cooling system 6 and corresponds to, for example, 30% of the reference value.

  Next, an operation method of the fast reactor decay heat removal system and its operation and effect in this embodiment will be described with reference to FIG. Similar to FIG. 2 described above, the horizontal axis of FIG. 5 represents the number of days after the occurrence of an abnormality in the fast reactor, and the vertical axis represents the temperature of the primary coolant in the reactor vessel 2.

  When an abnormality occurs in the fast reactor, if the power supply is not lost, it is the same as in the first embodiment. That is, the first direct core cooling system 5 is started by operating the damper. Then, as the cooling time elapses, that is, as the temperature of the primary coolant in the reactor vessel 2 decreases, the heat removal capability of the first direct core cooling system 5 is reduced, so that the inside of the reactor vessel 2 The primary coolant can be stabilized in the vicinity of the appropriate temperature (see the alternate long and short dash line U in FIG. 5).

  On the other hand, if the power supply is lost due to unforeseen circumstances, the cooling fan 12 cannot be driven, so that the heat removal capability of the first direct core cooling system 5 is limited to 30%, resulting in insufficient cooling. That is, the temperature of the primary coolant in the reactor vessel 2 rises (see the two-dot chain line S in FIG. 5). In this case, even if the temperature of the primary coolant is finally suppressed to 900K or less, the load on the facility increases.

  Therefore, as in the first embodiment, for example, when the temperature of the primary coolant in the reactor vessel 2 measured by the thermometer rises to a predetermined value Ta, the damper is operated to set the second direct core cooling system 6. Start. Thereby, the sum total of the heat removal capability of the cooling system is 150%. Therefore, as the cooling time elapses, the temperature of the primary coolant in the reactor vessel 2 decreases (see the solid line (S + A) in FIG. 5). However, even if the cooling time elapses to some extent, if the operation of the first direct core cooling system 5 and the second direct core cooling system 6 is continued as it is, overcooling occurs. That is, the temperature of the primary coolant may be less than 400K.

  Therefore, in the present embodiment, for example, the temperature of the primary coolant in the reactor vessel 2 measured with a thermometer is a predetermined value Tc (more specifically, the first direct core cooling system 5 and the enclosure cooling system 19 are removed later). In consideration of the sum of the heat capacities, when the temperature drops to a value set in advance so as to be slightly higher than the target temperature), the damper is operated to stop the second direct core cooling system 6 and the valve is operated to operate the housing. The cooling system 19 is activated. Thereby, the sum total of the heat removal capability of the cooling system becomes 60%. As a result, the primary coolant in the reactor vessel 2 can be stabilized in the vicinity of an appropriate temperature (see the solid line (S + C) in FIG. 5).

  The configuration of the fast reactor decay heat removal system in the third embodiment of the present invention will be described with reference to FIG. In FIG. 6, the same parts as those in the first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The fast reactor decay heat removal system of the present embodiment includes a forced air cooling type first direct core cooling system 5, a natural air cooling type second direct core cooling system 6, a natural air cooling type reactor vessel cooling system 7, A natural water cooling type enclosure cooling system 19 is provided.

  As in the first and second embodiments, the heat removal capability of the first direct core cooling system 5 with respect to the primary coolant in the reactor vessel 2 is the reference value (when the cooling fan 11 is driven at the maximum rotational speed). 100%), for example, when the cooling fan 11 is stopped, it is reduced to, for example, 30% of the reference value. The heat removal capacity of the second direct core cooling system 6 with respect to the primary coolant in the reactor vessel 2 is higher than the heat removal capacity (30%) of the first direct core cooling system 5 when the cooling fan 11 is stopped, for example, This corresponds to 120% of the reference value.

  The heat removal capability of the reactor vessel cooling system 7 with respect to the primary coolant in the reactor vessel 2 is lower than the heat removal capability (120%) of the second direct core cooling system 6 and corresponds to, for example, 35% of the reference value. The heat removal capacity of the enclosure cooling system 19 with respect to the primary coolant in the reactor vessel 2 is lower than the heat removal capacity (120%) of the second direct core cooling system 6 and corresponds to, for example, 15% of the reference value. Therefore, the sum total of the heat removal capabilities of the reactor vessel cooling system 7 and the enclosure cooling system 19 is lower than the heat removal capability (120%) of the second direct core cooling system 6 and is 50% of the reference value.

  Next, an operation method of the fast reactor decay heat removal system and its operation and effects in this embodiment will be described with reference to FIG. Like the above-mentioned FIG.2 and FIG.5, the horizontal axis | shaft of FIG. 7 represents taking the days after abnormality of a fast reactor, and the vertical axis | shaft represents the temperature of the primary coolant in the reactor vessel 2. FIG.

  When an abnormality occurs in the fast reactor, the power supply is not lost, which is the same as in the first and second embodiments. That is, the first direct core cooling system 5 is started by operating the damper. Then, as the cooling time elapses, that is, as the temperature of the primary coolant in the reactor vessel 2 decreases, the heat removal capability of the first direct core cooling system 5 is reduced, so that the inside of the reactor vessel 2 The primary coolant can be stabilized in the vicinity of the appropriate temperature (see the dashed line U in FIG. 7).

  On the other hand, if the power supply is lost due to unforeseen circumstances, the cooling fan 12 cannot be driven, so that the heat removal capability of the first direct core cooling system 5 is limited to 30%, resulting in insufficient cooling. That is, the temperature of the primary coolant in the reactor vessel 2 rises (see the two-dot chain line S in FIG. 7). In this case, even if the temperature of the primary coolant is finally suppressed to 900K or less, the load on the facility increases.

  Therefore, as in the first and second embodiments, for example, when the temperature of the primary coolant in the reactor vessel 2 measured by the thermometer rises to a predetermined value Ta, the damper is operated to cool the second direct core. System 6 is activated. Thereby, the sum total of the heat removal capability of the cooling system is 150%. Therefore, as the cooling time elapses, the temperature of the primary coolant in the reactor vessel 2 decreases (see the solid line (S + A) in FIG. 7). However, even if the cooling time elapses to some extent, if the operation of the first direct core cooling system 5 and the second direct core cooling system 6 is continued as it is, supercooling occurs. That is, the temperature of the primary coolant may be less than 400K.

  Therefore, in the present embodiment, for example, the temperature of the primary coolant in the reactor vessel 2 measured by a thermometer is a predetermined value Td (specifically, a first direct core cooling system 5 and a reactor vessel cooling system 7 described later). In consideration of the sum of the heat removal capabilities of the enclosure cooling system 19 and a value that is set in advance to be slightly higher than the target temperature), the damper is operated to stop the second direct core cooling system 6. At the same time, the reactor vessel cooling system 7 and the enclosure cooling system 19 are started by operating the damper and the valve. Thereby, the sum total of the heat removal capability of the cooling system becomes 80%. As a result, the primary coolant in the reactor vessel 2 can be stabilized in the vicinity of an appropriate temperature (see the solid line (S + B + C) in FIG. 7).

  In the third embodiment, when the temperature of the primary coolant in the reactor vessel 2 decreases to the predetermined value Td, the second direct core cooling system 6 is stopped, and the reactor vessel cooling system 7 and the enclosure are stopped. Although the case where the cooling system 19 is started at the same time has been described as an example, the present invention is not limited to this, and modifications can be made without departing from the technical idea and spirit of the present invention. That is, for example, when the temperature of the primary coolant in the reactor vessel 2 is lowered to a predetermined value, the second direct core cooling system 6 is stopped and the reactor vessel cooling system 7 is first started, and then the body cooling is performed. System 19 may be activated. Further, for example, when the temperature of the primary coolant in the reactor vessel 2 is lowered to a predetermined value, the second direct core cooling system 6 is stopped and the enclosure cooling system 19 is first started, and then the reactor vessel cooling is performed. System 7 may be activated. In these cases, the same effect as described above can be obtained.

  In the first to third embodiments, first, when the first direct core cooling system 5 is started and then the temperature of the primary coolant in the reactor vessel 2 rises to a predetermined value Ta, the second Although the case where the core cooling system 6 is directly activated has been described as an example, the present invention is not limited to this, and the core cooling system 6 can be modified without departing from the technical idea and spirit of the present invention. That is, if it is clear that the power supply is lost when an abnormality occurs in the fast reactor, the first direct core cooling system 5 and the second direct core cooling system 6 may be activated simultaneously. In this case, the same effect as described above can be obtained.

  Moreover, in the said 1st and 3rd embodiment, although the reactor vessel cooling system 7 demonstrated as an example the case where it comprised so that the outer side of the reactor vessel 2 might be cooled by the natural convection of air, mist ( The outside of the reactor vessel 2 may be cooled by natural convection of air containing droplets. In other words, a mist generating mechanism may be provided. Such a modification will be described with reference to FIGS. FIG. 8 is a schematic diagram showing the configuration of the fast reactor decay heat removal system in the present modification, and FIG. 9 is a partially enlarged view of a portion IX in FIG. 8, showing a part of the configuration of the atomic vessel cooling system. .

  In the reactor vessel cooling system 7A of the present modification, a throttle portion 29 is formed as a communication portion between the outer channel 16A and the inner channel 16B. In addition, a liquid storage part 30 that stores liquid is provided below the inner flow path 16 </ b> B, and a plurality of liquid supply holes 31 that communicate with the liquid storage part 30 and the throttle part 29 are formed. In the throttle unit 29, the flow rate of air is increased and negative pressure is generated, and the liquid is sprayed from the liquid supply hole 31 by this negative pressure (mist generation mechanism). Thereby, the air containing mist is supplied to the inner flow path 16B. Since the mist adheres to the outside of the reactor vessel 2 and evaporates, the cooling capacity can be improved.

  Although not particularly described in the first to third embodiments, when the diameter of the heat pipe 14 of the second direct core cooling system 5 is large, for example, as shown in FIG. The plate 32 may be divided into a lattice shape. Specifically, for example, the equivalent diameter is about 1 inch. Thereby, the influence of the radial direction of a heat pipe can be suppressed and the wettability of a condensate can be improved.

  Further, in the second and third embodiments, the lower header 21, the upper header 22, and the cooling flow path 23 are formed inside the cylindrical side wall portion of the casing 20 as a constituent of the casing cooling system 19. However, as shown in FIG. 11, for example, a lattice-shaped cooling flow path 33 connected to the lower header 21 may be formed inside the bottom wall portion of the housing 20. Thereby, for example, the internal core catch 34 is provided inside the reactor vessel 2, and the external core catch 35 is provided inside the bottom wall portion of the enclosure 20 (in other words, outside the reactor vessel 22). In some cases, the core catch 35 can be cooled. Alternatively, instead of the lower header 21, the upper header 22, and the cooling flow path 23 (and the cooling flow path 33), for example, a cooling pipe in contact with the housing 20 may be provided. In this case, the same effect as described above can be obtained.

  Needless to say, the present invention may be applied to a fast breeder reactor, a transuranium extinguishing reactor, or the like.

2 Reactor vessel 5 First direct core cooling system 6 Second direct core cooling system 7, 7A Reactor vessel cooling system 11 Cooling fan 19 Chassis cooling system 20 Chassis

Claims (4)

The first direct core in which the primary coolant in the reactor vessel of the fast reactor is cooled by the naturally circulating working fluid and, if power loss is not lost, the working fluid is cooled by the cooling air generated by the cooling fan. A cooling system;
A second direct core cooling system that cools the primary coolant in the reactor vessel with a naturally circulating working fluid and cools the working fluid by natural convection of air;
A reactor vessel cooling system for cooling the outside of the reactor vessel by natural convection of air,
The second direct core cooling system is configured to have a higher heat removal capability for the primary coolant in the reactor vessel than the first direct core cooling system when the cooling fan is stopped,
The reactor vessel cooling system is an operating method of a fast reactor decay heat removal system configured to have a lower heat removal capability for the primary coolant in the reactor vessel than the second direct core cooling system. ,
In the case of power loss, in addition to the first direct core cooling system, the second direct core cooling system is activated,
Thereafter, when the temperature of the primary coolant in the reactor vessel is reduced to a predetermined value, the second direct core cooling system is stopped and the reactor vessel cooling system is started. Operation method of removal system. The first direct core in which the primary coolant in the reactor vessel of the fast reactor is cooled by the naturally circulating working fluid and, if power loss is not lost, the working fluid is cooled by the cooling air generated by the cooling fan. A cooling system;
A second direct core cooling system that cools the primary coolant in the reactor vessel with a naturally circulating working fluid and cools the working fluid by natural convection of air;
A housing provided outside the reactor containment vessel that houses the reactor vessel is cooled with a working fluid that circulates naturally, and a housing cooling system that cools the working fluid with seawater,
The second direct core cooling system is configured to have a higher heat removal capability for the primary coolant in the reactor vessel than the first direct core cooling system when the cooling fan is stopped,
The enclosure cooling system is an operating method of a fast reactor decay heat removal system configured to have a lower heat removal capability for the primary coolant in the reactor vessel than the second direct core cooling system,
In the case of power loss, in addition to the first direct core cooling system, the second direct core cooling system is activated,
After that, when the temperature of the primary coolant in the reactor vessel is lowered to a predetermined value, the second direct core cooling system is stopped and the enclosure cooling system is started. Driving method. The first direct core in which the primary coolant in the reactor vessel of the fast reactor is cooled by the naturally circulating working fluid and, if power loss is not lost, the working fluid is cooled by the cooling air generated by the cooling fan. A cooling system;
A second direct core cooling system that cools the primary coolant in the reactor vessel with a naturally circulating working fluid and cools the working fluid by natural convection of air;
A reactor vessel cooling system for cooling the outside of the reactor vessel by natural convection of air;
A housing provided outside the reactor containment vessel that houses the reactor vessel is cooled with a working fluid that circulates naturally, and a housing cooling system that cools the working fluid with seawater,
The second direct core cooling system is configured to have a higher heat removal capability for the primary coolant in the reactor vessel than the first direct core cooling system when the cooling fan is stopped,
The reactor vessel cooling system and the enclosure cooling system are fast reactor decay heat removal configured such that the sum of the heat removal capacities for the primary coolant in the reactor vessel is lower than the second direct core cooling system. A system operation method,
In the case of power loss, in addition to the first direct core cooling system, the second direct core cooling system is activated,
After that, when the temperature of the primary coolant in the reactor vessel is lowered to a predetermined value, the second direct core cooling system is stopped and the reactor vessel cooling system and the enclosure cooling system are started. To operate the fast reactor decay heat removal system. In the operation method of the fast reactor decay heat removal system according to claim 1 or 3,
The method of operating a fast reactor decay heat removal system, wherein the reactor vessel cooling system is configured to cool the outside of the reactor vessel by natural convection of air containing mist.

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