JP2022083567A - Fast reactor control rod, fast reactor, and fast reactor control rod manipulation method - Google Patents

Abstract

To provide a fast reactor control rod that can increase a thermal margin of a fast reactor in a load follow-up operation.SOLUTION: A main reactor shutdown system control rod 1 has: an inner control rod cluster 2; and an annular outer control rod cluster 5 that surrounds the inner side control rod cluster 2. According to a load follow-up operation in a certain operation cycle of a fast reactor having the main reactor shutdown system control rod 1, the operation is configured to withdraw the outer control rod cluster 5 as a whole from a core fuel zone while the inner control rod cluster 2 as a whole is inserted into the core fuel zone; raise reactor power of the fast reactor up to target power; withdraw the inner control rod cluster 2 from the core fuel zone when the reactor power falls from target reactor power; and raise the reactor power up to the target reactor power. Then, when withdrawing the inner control rod cluster 2 with a small control rod worth from the core fuel zone, an output peak which is formed near a lower end of the inner control rod cluster 2 becomes small, and a thermal margin of the fast reactor in the load follow-up operation increases.SELECTED DRAWING: Figure 1

Description

The present invention relates to control rods for fast reactors, fast reactors and control rods for fast reactors, and control rods for fast reactors, control rods for fast reactors and fast reactors suitable for realizing load-following operation in fast reactors. Regarding the operation method.

A fast breeder reactor, which is a fast reactor, is described in Japanese Patent Publication No. 6-5426. The fast breeder reactor has a reactor vessel filled with liquid sodium as a coolant, and a core arranged in the reactor vessel and loaded with a plurality of fuel assemblies. In the fuel assembly, a plurality of fuel rods containing nuclear fuel material containing plutonium and depleted uranium are arranged in a trumpet tube having a regular hexagonal cross section. An entrance nozzle having an opening through which liquid sodium flows is provided at the lower end of the trumpet tube. By inserting this trumpet tube into the core support plate installed in the reactor vessel, the fuel assembly is supported by the core support plate. A coolant outflow portion that allows liquid sodium to flow out of the fuel assembly is formed at the upper end of the trumpet pipe.

The core of a fast breeder reactor has a core fuel region having an inner core region and an outer core region surrounding the inner core region, a blanket fuel region surrounding the core fuel region, and a shield region surrounding the blanket region. In the case of a standard homogeneous core, the Pu enrichment of the fuel assembly loaded in the outer core region is higher than the Pu enrichment of the fuel assembly loaded in the inner core region. As a result, the output distribution in the radial direction of the core is flattened.

A rotating plug is rotatably attached to the top of the reactor vessel over the core. A plurality of lower control rod guide pipes having a regular hexagonal cross section are arranged between the fuel assemblies in the core, and the lower end of each lower control rod guide pipe is supported by the core support plate. A plurality of upper control rod guide tubes having a regular hexagonal cross section are arranged directly above each lower control rod guide tube and above the core, and the upper end of each upper control rod guide tube is attached to a rotary plug. A plurality of control rod drive mechanisms are arranged at the upper end of each upper control rod guide tube and installed in a rotary plug.

In the fast breeder reactor, two independent control rods, a main reactor shutdown system control rod (adjustment rod) and a rear-end furnace shutdown system control rod (safety rod), are used as control rods. The main reactor shutdown control rods are used to adjust the reactivity and output distribution associated with the combustion of nuclear fuel material. The rear-end furnace shutdown system control rods are installed for backup in the unlikely event that the main furnace shutdown system control rods fail. The fast breeder reactor can be urgently stopped by either the main reactor shutdown system control rod or the retrofit reactor shutdown system control rod. Each control rod of the main reactor shutdown system control rod and the retrofit reactor shutdown system control rod has a plurality of neutron absorption rods in which pellets of boron carbide (B _4C ) are enclosed in a stainless steel cladding tube, and these neutron absorption rods are used. The rods are bundled in a cluster shape and stored in a cylindrical protective tube.

The main reactor stop system control rods are arranged in some lower control rod guide pipes, and are connected to the control rod drive mechanism to extend downward in the upper control rod guide pipes and the lower control rod guide pipes. It is connected to the lower end of. The rear-end reactor stop system control rods are located in the remaining lower control rod guide tubes and are connected to the control rod drive mechanism to extend downwards in the upper control rod guide tubes and the lower control rod guide tubes. It is connected to the lower end of the shaft. The main reactor stop system control rods and the rear-end reactor stop system control rods are moved in the axial direction of the core in the upper control rod guide pipe and the lower control rod guide pipe by the control rod drive mechanism.

Pellets of mixed oxide fuel (MOX fuel), which is a mixture of oxides of Pu and depleted uranium, are filled in the central portion in the axial direction in the fuel rod. Further, in the fuel rod, an axial blanket region filled with a plurality of uranium dioxide pellets made of depleted uranium is arranged above and below the filling region of the MOX fuel, respectively. The inner core fuel assembly loaded in the inner core region and the outer core fuel assembly loaded in the outer core region thus have multiple fuel rods filled with multiple pellets of MOX fuel.

The blanket fuel region surrounding the core fuel region is loaded with a blanket fuel assembly having multiple fuel rods filled with multiple pellets made of depleted uranium. The fuel rods of the blanket fuel assembly do not contain plutonium. Of the neutrons generated by the fission reaction generated in the fuel assembly loaded in the core fuel region, the neutrons leaked from the core fuel region are U-238 in each fuel rod of the blanket fuel assembly loaded in the blanket fuel region. Is absorbed by. As a result, the fissile nuclide Pu-239 is newly generated in each fuel rod of the blanket fuel assembly.

In boiling water reactors, control rods (gray nose control rods) in which a region formed of a member (for example, stainless steel) having a neutron absorption cross section smaller than that of boron carbide are arranged at the tip are used as control rods. .. The region below the tip is filled with boron carbide, which has a large neutron absorption cross section. By using such a control rod, it is possible to suppress an increase in the output of the core near the tip of the control rod when the control rod is pulled out, and it is possible to flatten the output distribution in the axial direction of the core.

Gazette No. 6-5426

As described above, by using a control rod whose tip is made of a member having a small neutron absorption cross section (for example, stainless steel), output peaking near the tip of the control rod is reduced when the control rod is pulled out. , The output distribution in the axial direction of the core is flattened.

However, unlike BWRs, which can adjust the reactor power by operating the control rods and adjusting the core flow rate, the fast reactor needs to adjust the reactor power using only the main reactor shutdown system control rods. In such a load-following operation of a fast reactor, a part of the main reactor stop system control rods in the axial direction is inserted into the effective fuel length of the core. In this case, similar to the reactor power shown by the broken line in FIG. 9 of the Hitachi review above, the power distribution in the axial direction of the core is distorted, so that the power peaking increases and the thermal margin in the core decreases. there is a possibility.

An object of the present invention is to provide a control rod for a fast reactor, a method for operating a control rod for a fast reactor and a fast reactor, which can increase the thermal margin of the fast reactor in load-following operation.

A feature of the present invention that achieves the above-mentioned object is that the control rods of the fast reactor have an inner control rod cluster and an annular outer control rod cluster surrounding the inner control rod cluster.

With the outer control rod clusters fully drawn out of the core fuel region and the inner control rod clusters with smaller control rod values fully inserted into the core fuel region, the axial output distribution of the core fuel region is cosine. It becomes a distribution, and the output peak of the output distribution becomes smaller. Therefore, when the control rods are used, the thermal margin of the fast reactor in the load following operation increases.

Further, when the outer control rod cluster is completely pulled out from the core fuel region and a part of the inner control rod cluster is inserted into the core fuel region, an output peak is formed near the lower end of the inner control rod cluster. However, due to the small control rod value of the inner control rod clusters, its output peak is such that some of the conventional main reactor shutdown control rods without inner control rod clusters and annular outer control rod clusters are pulled from the core fuel region. When pulled out, it becomes smaller than the output peak formed near the lower end of the conventional main reactor shutdown system control rod. Therefore, even when a part of the inner control rod cluster is inserted into the core fuel region, the thermal margin of the fast reactor in the load following operation is increased.

According to the present invention, it is possible to increase the thermal margin of the fast reactor in the load following operation.

It is a vertical sectional view of the control rod of the fast reactor of Example 1, which is a preferable example of this invention, that is, the control rod of a main reactor shutdown system. It is explanatory drawing which shows the state which the outer control rod cluster shown in FIG. 1 was engaged with a control rod holding unit. It is a vertical sectional view of the state where each of the inner control rod cluster and the outer control rod cluster of the control rods shown in FIG. 1 is fully inserted into the core fuel region of the fast reactor. FIG. 3 is a sectional view taken along line IV-IV of FIG. It is a vertical sectional view of the rear-stage furnace stop system control rod in the fast reactor in which the control rod of Example 1 is used. It is a cross-sectional view of the rear-stage furnace stop system control rod. It is a vertical cross-sectional view of a fast reactor using the control rod shown in FIG. 1 and the control rod of the rear reactor shutdown system shown in FIG. It is a block diagram of the control rod control system which operates the control rod shown in FIG. It is a block diagram of the control rod control system which operates the control rod of the rear furnace stop system shown in FIG. It is a cross-sectional view of the 1/2 core of the fast reactor shown in FIG. 7. It is explanatory drawing which shows the insertion state into the core at the time of the load follow-up operation of the fast reactor, each of the control rods shown in FIG. It is explanatory drawing which shows the insertion state into the core fuel region (fuel effective length) of the conventional main furnace stop system control rod. FIG. 12 is a cross-sectional view taken along the line XX of FIG. Output at each position in the axial direction with each of the main reactor shutdown control rods shown in FIG. 1 and the conventional main reactor shutdown control rods shown in FIG. 12 inserted into the core fuel region. It is a characteristic diagram which shows the relationship with the axial position of the effective fuel length. It is a vertical cross-sectional view of the fast reactor using the control rod shown in FIG. 1 and the rear reactor shutdown system control rod shown in FIG. 5 in Example 2, which is another preferred embodiment of the present invention. It is explanatory drawing which shows the insertion state of each of the inner control rod cluster and the outer control rod cluster of the main reactor stop system control rod shown in FIG. 15 into the core fuel region at the time of load follow-up operation of a fast reactor. It is explanatory drawing which shows the fully inserted state of each of the inner control rod cluster and the outer control rod cluster shown in FIG. 16 into the core fuel region. It is explanatory drawing which shows the operation state of each of the inner control rod cluster and the outer control rod cluster of the rear furnace stop system control rod shown in FIG. It is explanatory drawing which shows the fully inserted state of each of the inner control rod cluster and the outer control rod cluster of the rear reactor stop system control rod shown in FIG. 17 into the core fuel region at the time of the load follow-up operation of the fast reactor. In the method of operating the control rods of the fast reactor in Example 3, which is another preferred embodiment of the present invention, the description showing the state in which the control rods of the main reactor shutdown system are inserted into the core fuel region during the load following operation of the fast reactor. It is a figure. It is explanatory drawing which shows the fully inserted state of each of the inner control rod cluster and the outer control rod cluster in the main reactor stop system control rod shown in FIG. 20 into the core fuel region. It is explanatory drawing which shows the insertion state in the core fuel region at the time of the load follow-up operation of the fast reactor in the control rod operation method of the fast breeder reactor of Example 3. FIG. It is explanatory drawing which shows the fully inserted state of each of the inner control rod cluster and the outer control rod cluster of the rear reactor stop system control rod shown in FIG. 22 into the core fuel region.

Examples of the present invention will be described below.

The control rods of the fast reactor of Example 1, which is a preferred embodiment of the present invention, will be described with reference to FIGS. 1, 2, and 4.

In the fast breeder reactor 8 (see FIG. 7) described later, the control rods are two independent control rods, the control rod 1 (FIG. 1), which is the main reactor shutdown system control rod, and the rear reactor shutdown system control rod 23 (FIG. 5). It is composed. The control rod 1, which is a control rod for stopping the main reactor, is used for changing the reactivity of the fissile material contained in the nuclear fuel material and adjusting the output distribution during the operation of the fast breeder reactor 8. The rear-end furnace shutdown system control rod 23 is installed for backup in the unlikely event that the control rod 1 which is the main furnace shutdown system control rod fails. The fast breeder reactor 8 can be stopped urgently with only one of the control rod 1 and the rear reactor stop system control rod 23.

The control rod 1 of this embodiment will be described in detail with reference to FIGS. 1, 2 and 4. The control rod 1 has an inner control rod cluster (first inner control rod cluster) 2 and an outer control rod cluster (first outer control rod cluster) 5. The outer control rod cluster 5 has an annular cross section and surrounds the inner control rod cluster 2 (see FIG. 4). In the inner control rod cluster 2, a plurality of rod-shaped control rod elements 3 are arranged in a cylindrical control rod protection tube 4 having both ends sealed (see FIGS. 1 and 4). The control rod element 3 is filled with a plurality of pellets of boron carbide (B _4C ), which is a neutron absorber, in a sealed cladding tube (not shown). The outer control rod cluster 5 has a plurality of rod-shaped control rod elements 6 arranged in an annular control rod protection tube 7 having both ends sealed (see FIGS. 1 and 4). The control rod element 6 is also filled with a plurality of pellets of boron carbide in a sealed cladding tube (not shown). The axial length of each of the control rod elements 3 and 6 is the same as the effective fuel length, which is the axial length of the core fuel region 12, which will be described later.

The rearrangement furnace shutdown system control rod 23 will be described in detail with reference to FIGS. 5 and 6. The rear-end furnace shutdown system control rod 23 has an inner control rod cluster (second inner control rod cluster) 36 and an outer control rod cluster (second outer control rod cluster) 55. The outer control rod cluster 55 has an annular cross section and surrounds the inner control rod cluster 36 (see FIG. 6). The inner control rod cluster 36 arranges a plurality of rod-shaped control rod elements 37 in a cylindrical control rod protection tube 38 whose ends are sealed (see FIG. 6). The control rod element 37 is filled with a plurality of pellets of boron carbide in a sealed cladding tube (not shown). The outer control rod cluster 55 has a plurality of rod-shaped control rod elements 56 arranged in an annular control rod protection tube 57 whose ends are sealed (see FIG. 6). The control rod element 56 is also filled with a plurality of pellets of boron carbide in a sealed cladding tube (not shown). The axial lengths of the control rod elements 37 and 56 are the same as the effective fuel length, which is the axial length of the core fuel region 12, which will be described later.

The structure of a fast breeder reactor, which is a type of fast reactor to which control rod 1 is applied, will be described with reference to FIG. 7. The electric output of the fast breeder reactor 8 is 750,000 kW. The fast breeder reactor 8 includes a reactor vessel 9, a rotary plug 10, a core 11, a control rod 1, a rear reactor stop system control rod 23, a lower inner control rod guide pipes 26 and 58, and a lower outer control rod guide pipes 27 and 59. To prepare for. In addition to these configurations, the fast breeder reactor 8 includes an upper core support plate 50, a take-up device 30, a control rod drive mechanism 32, upper inner control rod guide pipes 28 and 60, upper outer control rod guide pipes 29 and 61, and winding. The taking device 62 and the control rod drive mechanism 64 are provided. The take-up devices 30 and 62 are first control rod moving devices, and the control rod drive mechanisms 32 and 64 are second control rod moving devices. Liquid sodium 24, which is a liquid metal, is used as a coolant and is filled in the reactor vessel 9. The upper core support plate 50 is arranged in the reactor vessel 9 and attached to the inner surface of the reactor vessel 9. The core support structure 52 is attached to the lower surface of the upper core support plate 50, and the lower core support plate 51 arranged in the core support structure 52 is attached to the inner surface of the core support structure 52. The lower core support plate 51 is located below the upper core support plate 50.

The rotary plug 10 is rotatably attached to the upper end of the reactor vessel 9. The core 11 is located in the reactor vessel 9 below the rotary plug 10 and has a core fuel region 12 and a gas plenum region 13 in the axial direction. The gas plenum region 13 is located on the core fuel region 12 (see FIG. 11). A cross section of the core 11 in the core fuel region 12 is shown in FIG. The core fuel region 12 includes an inner core fuel region 14 and an outer core fuel region 15, and the outer core fuel region 15 surrounds the inner core fuel region 14. Further, in the core 11, the radial blanket region 16 surrounds the outer core fuel region 15, and the reflector region 17 surrounds the radial blanket region 16.

A plurality of inner core fuel assemblies 18 are loaded in the inner core fuel region 14, and a plurality of outer core fuel assemblies 19 are loaded in the outer core fuel region 15. Each of the inner core fuel assembly 18 and the outer core fuel assembly 19 uses a ternary alloy (metal fuel) of U-Pu-10Zr as a nuclear fuel material, and a plurality of fuels produced by U-Pu-10Zr. It has a plurality of fuel rods (not shown) filled with pellets in a cladding tube. Each fuel rod has a nuclear fuel filling region filled with their fuel pellets and a gas plenum region formed above the nuclear fuel filling region in the cladding tube. When the burnups of the inner core fuel assembly 18 and the outer core fuel assembly 19 are 0 GWd / t, the Pu enrichment degree in the outer core fuel assembly 19 is higher than the Pu enrichment degree of the inner core fuel assembly 18. Is also high, and the average Pu enrichment of the outer core fuel region 15 is higher than that of the inner core fuel region 14. Therefore, the output distribution in the radial direction of the core fuel region 12 is flattened. In the inner core fuel assembly 18 and the outer core fuel assembly 19, a plurality of fuel rods are arranged in a tubular trumpet tube (not shown) having a regular hexagonal cross section.

A plurality of blanket fuel assemblies 20 are loaded into the radial blanket region 16. The 0 GWd / t blanket fuel assembly 20 has a plurality of fuel rods in which a plurality of fuel pellets made of depleted uranium are sealed in a cladding tube. The blanket fuel assembly 20 arranges these fuel rods in a tubular trumpet tube (not shown) having a regular hexagonal cross section. A plurality of reflectors are loaded in the reflector region 17. The reflector is made of stainless steel with a regular hexagonal cross section.

An entrance nozzle (not shown) is provided at the lower end of each trumpet pipe of the inner core fuel assembly 18, the outer core fuel assembly 19, and the blanket fuel assembly 20. The entrance nozzle of each fuel assembly penetrates the upper core support plate 50 and reaches the lower core support plate 51. Each of the inner core fuel assembly 18, the outer core fuel assembly 19, and the blanket fuel assembly 20 is supported by the upper core support plate 50. A high-pressure plenum 41 is formed in the core support structure 52 between the upper core support plate 50 and the lower core support plate 51. The low pressure plenum 42 is formed in the core support structure 52 below the lower core support plate 51. The lower plenum 40 is formed below the upper core support plate 50 between the bottom of the reactor vessel 9 and the core support structure 52. An opening 25 formed in the side wall of the core support structure 52 connects the lower plenum 40 and the high pressure plenum 41.

The inlet pipe 9A is attached to the reactor vessel 9. Liquid sodium 24, which is a cooling material, is filled in the reactor vessel 9, and the inlet pipe 9A penetrates the side wall of the reactor vessel 9 above the liquid level of the liquid sodium 24 and is inside the reactor vessel 9. To reach. In the reactor vessel 9, the inlet pipe 9A descends between the inner surface of the reactor vessel 9 and the core 11, penetrates the upper core support plate 50, and reaches the lower plenum 40. The lower end of the inlet pipe 9A is attached to the side surface of the core support structure 52, and the inlet pipe 9A communicates with the high pressure plenum 41 through the above opening 25. The outlet pipe 9B attached to the side wall of the reactor vessel 9 is connected to the upper plenum 53 formed in the reactor vessel 9 above the core 11. One end of the primary cooling system pipe (not shown) in which the primary main cooling material pump (not shown) and the intermediate heat exchanger (not shown) are installed is connected to the inlet pipe 9A, and the primary cooling system pipe is connected to the inlet pipe 9A. The other end is connected to the outlet pipe 9B.

Each of the control rods 1 is arranged between the inner core fuel assemblies 18 in the inner core fuel region 14 and between the outer core fuel assemblies 19 in the outer core fuel region 15 (see FIG. 10). .. Control rod guide pipes 46 (see FIG. 4) having a regular hexagonal cross section for control rod 1 are located between the inner core fuel assemblies 18 in the inner core fuel region 14 and outside in the outer core fuel region 15. The core fuel assemblies 19 are arranged between each other. The lower end of the control rod guide pipe 46 is attached to the upper core support plate 50, and the upper end of the control rod guide pipe 46 is located above the upper end of the core 11. The cylindrical lower outer control rod guide tube 27 is arranged in the control rod guide tube 46, and the cylindrical lower inner control rod guide tube 26 is arranged in the lower outer control rod guide tube 27. The lower ends of the lower inner control rod guide pipe 26 and the lower outer control rod guide pipe 27 are attached to the upper core support plate 50. The upper ends of the lower inner control rod guide pipe 26 and the lower outer control rod guide pipe 27 are also located above the upper end of the core 11.

A cylindrical upper outer control rod guide tube 29 is arranged directly above the lower outer control rod guide tube 27, and the upper end portion of the upper outer control rod guide tube 29 penetrates the rotary plug 10 and is attached to the rotary plug 10. .. The support plate 54 covers the upper end of the upper outer control rod guide tube 29 and is attached to the upper surface of the rotary plug 10. The cylindrical upper inner control rod guide tube 28 is arranged directly above the lower inner control rod guide tube 26 and is arranged in the upper outer control rod guide tube 29, and the upper end portion of the upper inner control rod guide tube 28 is a support plate. Attached to 54. The control rod drive mechanism 32, which is the second control rod moving device, is installed on the support plate 54. The drive extension shaft 33 connected to the control rod drive mechanism 32 extends downward from the rotary plug 10 and is arranged in the upper inner control rod guide pipe 28 and the lower inner control rod guide pipe 26. The inner control rod cluster 2 of the control rod 1 is arranged in the lower inner control rod guide pipe 26 and is connected to the lower end portion of the drive extension shaft 33.

The take-up device 30 which is the first control rod moving device is installed on the upper surface of the rotary plug 10, and the lower end portion of the stainless steel rope 31 extending downward from the take-up device 30 is the upper outer control rod guide tube 29. It is attached to a control rod holding unit 44 arranged between the lower inner control rod guide tube 26 and the lower outer control rod guide tube 27 through an annular region formed between the upper inner control rod guide tube 28 and the upper inner control rod guide tube 28. The annular outer control rod cluster 5 of the control rod 1, which is arranged between the lower inner control rod guide tube 26 and the lower outer control rod guide tube 27, is held by the control rod holding unit 44. Specifically, by inserting the rotary hook 45 provided in the control rod holding unit 44 into the ring of the hanging metal fitting 22 provided at the upper end of the outer control rod cluster 5, the outer control rod cluster 5 is formed. It is connected to the control rod holding unit 44 and held by the control rod holding unit 44. The rotary hook 45 is a connecting means for detachably connecting the outer control rod cluster 5 and the control rod holding unit 44. As will be described later, the control rod holding unit 44 operates the rotary hook (connecting means) 45 by inputting a scrum signal, and the outer control rod cluster 5 and the control rod holding unit 44 are separated from each other.

In addition, in order to smoothly move the outer control rod cluster 5 up and down, at least three hanging metal fittings 22 are attached to the upper ends of the outer control rod cluster 5 at equal intervals. On the upper surface of the rotary plug 10 directly above each of the three hanging metal fittings 22, three winding devices 30 having the same number as the number of hanging metal fittings 22 are installed. Three control rod holding units in which the lower end of the stainless steel rope 31 extending downward from the take-up device 30 is arranged between the lower inner control rod guide pipe 26 and the lower outer control rod guide pipe 27. Attached to each of the 44. The rotary hooks 45 provided on each of the three control rod holding units 44 are inserted into the rings of the above three hanging metal fittings 22. The outer control rod cluster 5 is held by three control rod holding units 44.

The winding device 30 may move the inner control rod cluster 2 in the axial direction of the core 11, and the control rod drive mechanism 32 may move the outer control rod cluster 5 in the axial direction of the core 11. In this case, one take-up device 30 and each of the three control rod drive mechanisms 32 are installed on the support plate 54 attached to the upper surface of the rotary plug 10. The three control rod drive mechanisms 32 are arranged around the take-up device 30. The lower end of the stainless steel rope 31 extending downward from the take-up device 30 passes through the upper inner control rod guide pipe 28 and the lower inner control rod guide pipe 26, and enters the lower inner control rod guide pipe 26. It is attached to the control rod holding unit 44 to be arranged. By inserting the rotary hook 45 provided in the control rod holding unit 44 into the ring of the hanging metal fitting 22 provided at the upper end of the inner control rod cluster 2 arranged in the lower inner control rod guide pipe 26, The inner control rod cluster 2 is connected to the control rod holding unit 44 and held by the control rod holding unit 44.

The lower end of the drive extension shaft 33 connected to each of the three control rod drive mechanisms 32 and extending downward is an annular shape formed between the upper outer control rod guide pipe 29 and the upper inner control rod guide pipe 28. Through the region, it is connected to the upper end of the annular outer control rod cluster 5 arranged in the annular region formed between the lower outer control rod guide tube 27 and the lower inner control rod guide tube 26. The positions where the drive extension shafts 33 of the three control rod drive mechanisms 32 are connected to the upper ends of the outer control rod clusters 5 are arranged at equal intervals on the upper ends of the annular outer control rod clusters 5. The three control rod drive mechanisms 32 synchronously move the outer control rod cluster 5 in the axial direction of the core 11.

Emergency insertion of the outer control rod cluster 5 extracted from the core fuel region 12 into the core fuel region 12 is performed by the control rod drive mechanism 32, and the core of the inner control rod cluster 2 extracted from the core fuel region 12 is performed. Emergency insertion into the fuel region 12 is performed by disconnecting the rotary hook 45 of the control rod holding unit 44 from the hanging bracket 22 attached to the upper end of the inner control rod cluster 2.

Each of the rear core control rods 23 is also arranged between the inner core fuel assemblies 18 in the inner core fuel region 14 and between the outer core fuel assemblies 19 in the outer core fuel region 15 ( See FIG. 10). Control rod guide pipes 73 (see FIG. 6) having a regular hexagonal cross section for the rear reactor stop system control rods 23 are provided between the inner core fuel assemblies 18 in the inner core fuel region 14 and in the outer core fuel region. The outer core fuel assemblies 19 in 15 are respectively arranged between each other. The lower end of the control rod guide pipe 73 is attached to the upper core support plate 50, and the upper end of the control rod guide pipe 73 is located above the upper end of the core 11. The cylindrical lower outer control rod guide tube 59 is arranged in the control rod guide tube 73, and the cylindrical lower inner control rod guide tube 58 is arranged in the lower outer control rod guide tube 59. The lower ends of the lower inner control rod guide pipe 58 and the lower outer control rod guide pipe 59 are attached to the upper core support plate 50. The upper ends of the lower inner control rod guide pipe 58 and the lower outer control rod guide pipe 59 are also located above the upper end of the core 11.

The cylindrical upper outer control rod guide pipe 61 is arranged directly above the lower outer control rod guide pipe 59, and the upper end portion of the upper outer control rod guide pipe 61 penetrates the rotary plug 10 and is attached to the rotary plug 10. .. The support plate 54A covers the upper end of the upper outer control rod guide pipe 61 and is attached to the upper surface of the rotary plug 10. The cylindrical upper inner control rod guide pipe 60 is arranged directly above the lower inner control rod guide pipe 58 and is arranged in the upper outer control rod guide pipe 61, and the upper end portion of the upper inner control rod guide pipe 60 is a support plate. It is attached to 54A. A control rod drive mechanism 64, which is a fourth control rod moving device, is installed on the support plate 54A. The drive extension shaft 65 connected to the control rod drive mechanism 64 extends downward from the rotary plug 10 and is arranged in the upper inner control rod guide pipe 60 and the lower inner control rod guide pipe 58. The inner control rod cluster 36 of the rear furnace stop system control rod 23 is arranged in the lower inner control rod guide pipe 58 and connected to the lower end portion of the drive extension shaft 65.

The lower inner control rod guide pipe 26 is separated from the upper inner control rod guide pipe 28, the lower outer control rod guide pipe 27 is separated from the upper outer control rod guide pipe 29, and the lower inner control rod guide pipe 58 is further separated from the upper inner side. Since it is separated from the control rod guide pipe 60 and the lower outer control rod guide pipe 59 is separated from the upper outer control rod guide pipe 61, the rotation of the rotary plug 10 is not hindered by those control rod guide pipes.

The take-up device 62, which is a third control rod moving device, is installed on the upper surface of the rotary plug 10, and the lower end of the stainless steel rope 63 extending downward from the take-up device 62 is the upper inner control rod guide tube 60. It is attached to the control rod holding unit 66 arranged between the lower inner control rod guide pipe 58 and the lower outer control rod guide pipe 59 through the annular region formed between the upper outer control rod guide pipe 61 and the lower outer control rod guide pipe 61. The annular outer control rod cluster 55 of the rear furnace stop system control rod 23, which is arranged between the lower inner control rod guide pipe 58 and the lower outer control rod guide pipe 59, is held by the control rod holding unit 66. Specifically, the outer control rod cluster 55 is controlled by inserting the rotary hook 67 provided in the control rod holding unit 66 into the ring of the hanging metal fitting 75 provided at the upper end of the outer control rod cluster 55. It is held by the rod holding unit 66.

In addition, in order to smoothly move the outer control rod cluster 55 up and down, at least three hanging metal fittings 75 are attached to the upper ends of the outer control rod cluster 55 at equal intervals. Directly above each of the three hanging metal fittings 75, on the upper surface of the rotary plug 10, three winding devices 62 having the same number as the number of hanging metal fittings 75 are installed. The lower end of the rope 63 extending downward from the take-up device 62 is attached to each of the three control rod holding units 66 arranged between the lower inner control rod guide pipe 58 and the lower outer control rod guide pipe 59. It is attached. Rotating hooks 67 provided on each of the three control rod holding units 66 are inserted into the loops of the above three hanging brackets 75. The outer control rod cluster 55 is held by three control rod holding units 66.

In the fast breeder reactor 8, the outer control rod cluster, the first control rod moving device for moving the outer control rod cluster in the axial direction of the core 11, the inner control rod cluster, and the inner control rod cluster are moved in the axial direction of the core 11. 2 It has a control rod system including a control rod moving device. The first control rod moving device and the second control rod moving device have different mechanisms for moving the control rod cluster in the axial direction of the core 11. Specifically, the control rod system in the fast breeder reactor 8 is a first method in which the outer control rod cluster 5 and the outer control rod cluster 5 of the control rod 1 (main reactor shutdown system control rod) are moved in the axial direction of the core 11. Control rod moving device, inner control rod cluster 2 of control rod 1, second control rod moving device for moving inner control rod cluster 2 in the axial direction of the core 11, outer control rod cluster 55 of the rear furnace stop system control rod 23, The first control rod moving device for moving the outer control rod cluster 55 in the axial direction of the core 11, the inner control rod cluster 36 for the rear-end control rod 23, and the inner control rod cluster 36 for moving the inner control rod cluster 36 in the axial direction of the core 11. 2 Includes control rod moving device. The first control rod moving device for moving each of the outer control rod cluster 5 of the control rod 1 and the outer control rod cluster 55 of the rear furnace stop system control rod 23 in the axial direction is a take-up device. The second control rod moving device for moving each of the inner control rod cluster 2 of the control rod 1 and the inner control rod cluster 36 of the rear furnace stop system control rod 23 in the axial direction is a control rod drive mechanism.

Further, in the rear reactor stop system control rod 23, the inner control rod cluster 36 is moved in the axial direction of the core 11 by the take-up device 62, and the outer control rod cluster 55 is moved in the axial direction of the core 11 by the control rod drive mechanism 64. You may let me. In this case, one take-up device 62 and each of the three control rod drive mechanisms 64 are installed on the support plate 54 attached to the upper surface of the rotary plug 10. The three control rod drive mechanisms 64 are arranged around the take-up device 62. A control in which the lower end of the rope 63 extending downward from the take-up device 62 passes through the upper inner control rod guide pipe 60 and the lower inner control rod guide pipe 58 and is arranged in the lower inner control rod guide pipe 58. It is attached to the rod holding unit 66. By inserting the rotary hook 67 provided in the control rod holding unit 66 into the ring of the hanging bracket 22 provided at the upper end of the inner control rod cluster 36 arranged in the lower inner control rod guide tube 58. The inner control rod cluster 36 is connected to the control rod holding unit 66 and held by the control rod holding unit 66.

The lower end of the drive extension shaft 65 connected to each of the three control rod drive mechanisms 64 and extending downward is an annular shape formed between the upper outer control rod guide pipe 61 and the upper inner control rod guide pipe 60. Through the region, it is connected to the upper end of the annular outer control rod cluster 5 arranged in the annular region formed between the lower outer control rod guide tube 59 and the lower inner control rod guide tube 58. The positions where the drive extension shafts 65 of the three control rod drive mechanisms 64 are connected to the upper ends of the outer control rod clusters 55 are arranged at equal intervals on the upper ends of the annular outer control rod clusters 55. The three control rod drive mechanisms 64 synchronously move the outer control rod cluster 55 in the axial direction of the core 11.

Emergency insertion of the outer control rod cluster 55 extracted from the core fuel region 12 into the core fuel region 12 is performed by the control rod drive mechanism 64, and the core of the inner control rod cluster 36 extracted from the core fuel region 12 is performed. Emergency insertion into the fuel region 12 is performed by disconnecting the rotary hook 67 of the control rod holding unit 66 from the hanging bracket 22 attached to the upper end of the inner control rod cluster 36.

In FIG. 7, the lower inner control rod guide tubes 26 and 58, the lower outer control rod guide tubes 27 and 59, the upper inner control rod guide tubes 28 and 60, the upper outer control rod guide tubes 29 and 61, and the inner control of the control rod 1 are controlled. The rod clusters 2 and outer control rod clusters 5 have been expanded to facilitate understanding of the interrelationships of their configurations. Further, the lower inner control rod guide pipe 58, the lower outer control rod guide pipe 59, the upper inner control rod guide pipe 60, the upper outer control rod guide pipe 61, the inner control rod cluster 36 and the outer control of the rear furnace stop system control rod 23. The rod clusters 55 are also expanded and described to facilitate the understanding of the interrelationships of their configurations.

As shown in FIG. 8, the control unit 43 for the control rod 1 is connected to each take-up device 30, the control rod drive mechanism 32, and the control rod holding unit 44. As shown in FIG. 9, the control unit 43A for the rear-loading furnace stop system control rod 23 is connected to each take-up device 62, the control rod drive mechanism 64, and the control rod holding unit 66. The control unit 43 may not be provided, and the control unit 43 may be connected to the take-up device 62, the control rod drive mechanism 64, and the control rod holding unit 66.

During the operation of the fast breeder reactor 8, the main coolant pump provided in the primary cooling system pipe described above is driven, and the liquid sodium 24 existing in the upper plenum 53 in the reactor vessel 9 is primarily cooled from the outlet pipe 9B. It is discharged to the system piping. The liquid sodium 24 is boosted by the main coolant pump and supplied to the intermediate heat exchanger. The liquid sodium 24 is heat exchanged with the secondary liquid sodium flowing through the shell side of the intermediate heat exchanger and flowing in the heat transfer tube of the intermediate heat exchanger. The liquid sodium 24 discharged from the intermediate heat exchanger to the primary cooling system pipe is supplied from the inlet pipe 9A to the lower plenum 40 in the reactor vessel 9. The liquid sodium 24 in the lower plenum 40 is guided to the high pressure plenum 41 through the opening 25.

The liquid sodium 24 in the high-pressure plenum 41 passes through the cooling material inlet formed on the side wall of each entrance nozzle of the inner core fuel assembly 18, the outer core fuel assembly 19, and the blanket fuel assembly 20 to collect the inner core fuel assembly. It reaches the inside of each of the body 18, the outer core fuel assembly 19 and the blanket fuel assembly 20. The liquid sodium 24 rising in the inner core fuel assembly 18 and the outer core fuel assembly 19 is a fissile material contained in the nuclear fuel material filled in the fuel rods in each fuel assembly (for example, Pu-239). It is heated by the heat generated by the fission of the fuel and the temperature rises. The liquid sodium 24 whose temperature has risen flows out from the upper ends of the inner core fuel assembly 18 and the outer core fuel assembly 19 to the upper plenum 53. This high temperature liquid sodium 24 is supplied to the intermediate heat exchanger as described above. The liquid sodium 24 supplied into the blanket fuel assembly 20 also rises in the blanket fuel assembly 20 and flows out from the upper end of the blanket fuel assembly 20 to the upper plenum 53.

The liquid sodium 24 in the high-pressure plenum 41 is an annular shape formed in the lower inner control rod guide tube 26 provided for the control rod 1 and between the lower inner control rod guide tube 26 and the lower outer control rod guide tube 27. Guided into each region, they ascend within the lower inner control rod guide tube 26 and its annular region. The liquid sodium 24 rising in the lower inner control rod guide tube 26 cools the inner control rod cluster 2 existing in the lower inner control rod guide tube 26, and from the upper end of the lower inner control rod guide tube 26 to the upper plenum 53. It is discharged. The liquid sodium 24 rising in the annular region between the lower inner control rod guide tube 26 and the lower outer control rod guide tube 27 cools the outer control rod cluster 5 present in the annular region and is above the annular region. It is discharged to Plenum 53.

Further, the liquid sodium 24 in the high-pressure plenum 41 is used in the lower inner control rod guide pipe 58 provided for the rear furnace stop system control rod 23, and in the lower inner control rod guide pipe 58 and the lower outer control rod guide pipe 59. They are guided into the annular region formed between them, and ascend in the lower inner control rod guide pipe 58 and the annular region thereof. The liquid sodium 24 rising in the lower inner control rod guide tube 58 cools the inner control rod cluster 36 existing in the lower inner control rod guide tube 58, and from the upper end of the lower inner control rod guide tube 58 to the upper plenum 53. It is discharged. The liquid sodium 24 rising in the annular region between the lower inner control rod guide tube 58 and the lower outer control rod guide tube 59 cools the outer control rod cluster 55 present in the annular region and is above the annular region. It is discharged to Plenum 53.

A load-following operation is performed in a certain operation cycle of the fast breeder reactor 8 provided with the control rod 1 of this embodiment. The operation method of the control rod in the load following operation of the fast breeder reactor 8 will be described below.

When the operation of the fast breeder reactor 8 is stopped, the inner control rod clusters 2 and the outer control rod clusters 5 of all the control rods 1 are fully inserted into the core fuel region 12 (the portion of the effective fuel length) as shown in FIG. Has been done. For full insertion of the outer control rod cluster 5 into the core fuel region 12, the rotating drum around which the rope 31 of the take-up device 30 is wound is rotated in the reverse direction, the rope 31 is unwound from the rotating drum, and the outer control rod cluster 5 is held. This is done by lowering the control rod holding unit 44. In FIG. 3, the outer control rod cluster 5 is separated from the control rod holding unit 44 and fully inserted into the core fuel region 12, but when the fast breeder reactor 8 is normally shut down, the core fuel is as described above. The outer control rod cluster 5 fully inserted into the region 12 is held by the control rod holding unit 44. Full insertion of the inner control rod cluster 2 into the core fuel region 12 is performed by the control rod drive mechanism 32.

After the operation of the fast breeder reactor 8 is started in a certain operation cycle, the inside of the control chamber (not shown) existing outside the reactor containment vessel (not shown) in which the fast breeder reactor 8 is installed inside. The outer control rod cluster from the control unit 43 to each take-up device 30 based on the outer control rod cluster withdrawal command, which is a control command output from the control panel (not shown) in the control room by the operation of the operator in A pull-out signal is output. By this pull-out signal, each rotating drum of the three winding devices 30 is rotated in the forward direction. Each rotating drum is rotated in the forward direction by the synchronous rotation of the motor provided for each rotating drum. Since the rotational speed of the motor is reduced to a predetermined speed by the reduction gear, each rotating drum is rotated forward at the predetermined speed. By rotating each of the rotating drums of the three winding devices 30 in the forward direction, each of the three ropes 31 is separately wound around each rotating drum, and the outer control rod cluster 5 of the control rod 1 controls the lower inner side. It is gradually raised in the annular region between the rod guide tube 26 and the lower outer control rod guide tube 27.

In that certain operation cycle, all the control rods 1 operate normally, so that all the rear reactor stop system control rods 23 are not operated and are completely pulled out from the core fuel region 12 (see FIG. 11).

As the outer control rod cluster 5 rises, fissionable plutonium contained in the nuclear fuel material in the inner core fuel assembly 18 and the outer core fuel assembly 19 loaded in the core 11 of the fast breeder reactor 8 undergoes fission, and eventually. , The fast breeder reactor 8 reaches criticality. Further, the outer control rod cluster 5 is pulled out from the core fuel region 12, and the fission of the fissionable material in the inner core fuel assembly 18 and the outer core fuel assembly 19 loaded in the core 11 is promoted, and the fuel assembly thereof is promoted. The temperature of the liquid sodium 24 that rises in the body rises. At the same time, the reactor output of the fast breeder reactor 8 also increases.

The extraction of the outer control rod cluster 5 from the core fuel region 12 is performed by rotating the rotary drum of each take-up device 30 in the forward direction and winding the rope 31 around the rotary drum, as described above. Further, when the outer control rod cluster 5 is completely pulled out from the core fuel region 12, at least a part of the control rod holding unit 44 is connected to the upper end of the lower inner control rod guide pipe 26 and the upper end of the lower outer control rod guide pipe 27. It is located between (see Fig. 1).

When the outer control rod clusters 5 of a predetermined number of control rods 1 are completely pulled out from the core fuel region 12 while the inner control rod clusters 2 of all the control rods 1 are fully inserted into the core fuel region 12, they are The forward rotation of the rotating drum of the take-up device 30 is stopped. In a state where the outer control rod clusters 5 of the control rods 1 having a predetermined number of bodies are completely pulled out from the core fuel region 12 (see FIG. 1), the reactor output of the fast breeder reactor 8 is the first in the load following operation. It is increased to the target reactor output (a certain reactor output less than the rated output (100% reactor output) at the rated operation of the fast breeder reactor 8). When the outer control rod clusters 5 are completely pulled out from the core fuel region 12 and the reactor output rises to the first target reactor output, the rotation stop of the rotating drum of each take-up device 30 is as follows. It is done. That is, a drive stop signal is output from the control unit 43 to each take-up device 30 based on the outer control rod cluster pull-out stop command output from the control panel to the control unit 43. In each take-up device 30 to which the drive stop signal is input, the rotation of the rotating drum is stopped. After the reactor power reaches its first target reactor power, the load following operation of the fast breeder reactor 8 at the first target reactor power is continuously carried out until the end of the above-mentioned certain operation cycle. ..

If the reactor power drops below the first target reactor power in the middle of a certain operation cycle, the control rod drive mechanism 32 from the control unit 43 based on the inner control rod cluster withdrawal command output from the control panel. The inner control rod cluster withdrawal signal is output to. The control rod drive mechanism 32 is operated by the inner control rod cluster withdrawal signal. The inner control rod cluster 2 of the control rod 1 is gradually pulled out from the core fuel region 12 by the operation of the control rod drive mechanism 32, and increases the reactor output of the fast breeder reactor 8. When the reactor output reaches the first target reactor output, an inner control rod cluster extraction stop signal is sent from the control unit 43 to the control rod drive mechanism 32 based on the inner control rod cluster extraction stop command output from the control panel. It is output and the ascent of the inner control rod cluster 2 by the control rod drive mechanism 32 is stopped. By repeating the ascent and stop of the inner control rod cluster 2 in this way, the operation of the fast breeder reactor 8 is continued while the reactor output is maintained at the first target reactor output throughout the operation cycle. ..

It should be noted that the fissionable material contained in the respective nuclear fuel materials of the inner core fuel assembly 18 and the outer core fuel assembly 19, for example, the fission reactivity fluctuates with the combustion of the fissionable plutonium, or the fast breeder reactor When the temperature of the liquid sodium 24, which is the cooling material of No. 8, changes and the Doppler reactivity and the expansion reactivity of the nuclear fuel material thereof are input, the surplus reactivity of the fast breeder reactor 8 changes. When such a change in the excess reactivity of the fast breeder reactor 8 occurs, the change in the excess reactivity can be dealt with by adjusting the number of insertions of the inner control rod cluster 2 of the control rod 1 into the core fuel region 12. Then, the operation of the fast breeder reactor 8 can be continued.

When the operation of the fast breeder reactor 8 in its operation cycle is completed, the operation of the fast breeder reactor 8 is stopped. The operation stop command of the fast breeder reactor 8 is output from the control panel to the control unit 43. The control unit 43 to which the operation stop command is input outputs the operation stop signal to all the winding devices 30 and all the control rod drive mechanisms 32. The three winding devices 30 to which the operation stop signal is input rotate each rotating drum in the reverse direction to unwind the rope 31 wound around each rotating drum, and the outer control rod cluster 5 is connected to the lower inner control rod guide pipe 26. And the lower outer control rod guide tube 27 is lowered in the annular region. The control rod drive mechanism 32 to which the operation stop signal is input lowers the inner control rod cluster 2 in the lower inner control rod guide pipe 26. When the outer control rod cluster 5 and the inner control rod cluster 2 of all the control rods 1 are fully inserted into the core fuel region 12, that is, the outer control rod cluster 5 and the inner control rod cluster 2 are shown in FIG. When the indicated position is reached, the operation of the fast breeder reactor 8 is stopped, and the cold breeder reactor 8 is put into a cold shutdown state.

The target reactor power in load-following operation may vary within one operating cycle and may vary between different operating cycles. In addition to the load-following operation at the first target reactor output, the load-following operation may be performed at the second target reactor output higher than the first target reactor output and lower than the rated output in the operation cycle. .. In this case, the outer control rod clusters 5 of the control rods 1 having a larger number than the number of the control rods 1 in the load follow-up operation at the first target reactor output are completely pulled out from the core fuel region 12. Further, it is also conceivable to carry out the load follow-up operation at the third target reactor output lower than the above-mentioned first target reactor output. In the load-following operation at the third target reactor output, the outer control rod cluster 5 of the control rod 1 having a smaller number of bodies than the number of control rods 1 in the load-following operation at the first target reactor output described above It is completely withdrawn from the core fuel region 12.

An abnormal situation occurs in the fast breeder reactor 8, and the fast breeder reactor 8 must be stopped urgently. At this time, a scrum signal is output to the control unit 43 from the control panel in the control room. The control unit 43 that has input the scrum signal outputs the scrum signal to all the control rod holding units 44 and all the control rod drive mechanisms 32. The control rod holding unit 44 to which the scram signal is input rotates the rotary hook 45 in the reverse direction to remove the rotary hook 45 from the hanging metal fitting 22 provided on the outer control rod cluster 5. As a result, the outer control rod cluster 5 is separated from the control rod holding unit 44, and the outer control rod cluster 5 falls toward the upper core support plate 50. That is, the outer control rod cluster 5 is rapidly inserted into the core fuel region 12. Further, the control rod drive mechanism 32 to which the scram signal is input releases the connection state between the inner control rod cluster 2 and the drive extension shaft 33 of the control rod drive mechanism 32. Therefore, the inner control rod cluster 2 also falls toward the upper core support plate 50 and is rapidly inserted into the core fuel region 12. In this way, the fast breeder reactor 8 is urgently shut down. The rapidly inserted inner control rod cluster 2 and outer control rod cluster 5 are located in the core fuel region 12 (see FIG. 3).

When an abnormal situation occurs in the fast breeder reactor 8 with all the inner control rod clusters 2 fully inserted in the core fuel region 12, the control unit 43 inputting the scram signal output from the control panel may be used. The scram signal is output only to all control rod holding units 44. At this time, all the outer control rod clusters 5 are separated from the control rod holding units 44 and rapidly inserted into the core fuel region 12.

Since the rear reactor stop system control rod 23 used in this embodiment has the inner control rod cluster 36 and the outer control rod cluster 55, the range of load following operation of the fast breeder reactor 8 can be expanded. That is, the outer control rod clusters 5 of all the control rods 1 are completely drawn out from the core fuel region 12, and further, a predetermined body which is a part of all the rear reactor stop system control rods 23 provided in the fast breeder reactor 8. Atomic arrival when the outer control rod clusters 5 are fully withdrawn from the core fuel region 12 by fully withdrawing the outer control rod clusters 55 of the number (plural) rear reactor stop system control rods 23 from the core fuel region 12. The load-following operation of the fast breeder reactor 8 can be performed at the fourth target reactor output lower than the reactor output. The load following operation at the fourth target reactor output in the fast breeder reactor 8 using both the control rods 1 and the control rods 23 for shutting down the rear reactor with a predetermined number of bodies will be described below.

In this load-following operation, as described above, the outer control rod clusters 5 of all control rods 1 are operated by the take-up device 30, and the inner control rod clusters 3 of all control rods 1 are operated by the control rod drive mechanism 32. Will be done. Therefore, here, the operations of the outer control rod cluster 55 and the inner control rod cluster 36 of the rear-end furnace shutdown system control rod 23 will be described.

After the operation of the fast breeder reactor 8 in a certain operation cycle is started, the three winding devices 30 provided for each of the outer control rod clusters 5 are operated to operate the outer control rod clusters 5 of all the control rods 1. Is completely withdrawn from the core fuel region 12. In addition to the total extraction of all the outer control rod clusters 5 from the core fuel region 12, the rotating drums of the three winding devices 62 are rotated in the forward direction, and the rope 63 is wound around each rotating drum. The outer control rod cluster 55 of the rear reactor stop system control rod 23 is gradually raised in the annular region between the lower inner control rod guide pipe 58 and the lower outer control rod guide pipe 59. An outer control rod cluster extraction signal is output from the control unit 43A to each take-up device 62 based on the outer control rod cluster extraction command which is a control command output from the control panel in the control room by the operation of the operator. By this pull-out signal, the rotary drum of each take-up device 62 is rotated forward, and the outer control rod cluster 55 of the rear furnace stop system control rod 23 having a predetermined number of bodies rises.

Inside the inner core fuel assembly 18 (or outer core fuel assembly 19) near the operated rear-end reactor shutdown system control rods 23 loaded in the core 11 of the fast breeder reactor 8 as the outer control rod cluster 55 rises. Fissionable plutonium contained in the nuclear fuel material of the above is fissioned, and in combination with the rise of the outer control rod cluster 5 of each control rod 1, the fast breeder reactor 8 eventually reaches the criticality. Further, a predetermined number of outer control rod clusters 55 are withdrawn from the core fuel region 12 to promote fission of fissionable materials in the inner core fuel assembly 18 (or outer core fuel assembly 19) and fuel them. The temperature of the liquid sodium 24 rising in the assembly rises. Along with the withdrawal of the outer control rod clusters 55 and each outer control rod cluster 5, the reactor output of the fast breeder reactor 8 also increases.

When the outer control rod cluster 55 is fully withdrawn from the core fuel region 12, at least part of the control rod holding unit 66 is between the upper end of the lower inner control rod guide tube 58 and the upper end of the lower outer control rod guide tube 59. It is located in (see Fig. 5).

When the outer control rod cluster 55 of the rear reactor stop system control rod 23 having a predetermined number of bodies is completely pulled out from the core fuel region 12, the forward rotation of the rotating drum of the take-up device 62 thereof is stopped. In the state where the outer control rod clusters 5 of all the control rods 1 and the outer control rod clusters 55 of the rear reactor shutdown system control rods 23 having a predetermined number of bodies are all pulled out from the core fuel region 12, the fast breeder reactor 8 The reactor power is increased to the above-mentioned fourth target reactor power in the load following operation. When the reactor power rises to the fourth target reactor power, the rotation of the rotary drum of the take-up device 62 is stopped as follows. That is, a drive stop signal is output from the control unit 43A to the take-up device 62 based on the outer control rod cluster pull-out stop command output from the control panel to the control unit 43A. In the winding device 62 to which the drive stop signal is input, the rotation of the rotating drum is stopped. After the reactor power reaches its 4th target reactor power, the load-following operation of the fast breeder reactor 8 at the 4th target reactor power is continuously carried out until the end of the above-mentioned certain operation cycle. ..

If the reactor power drops below the fourth target reactor power in the middle of a certain operation cycle, the control rod drive mechanism from the control unit 43 is based on the inner control rod cluster withdrawal command output from the control panel. An inner control rod cluster extraction signal is output from 32 and the control unit 43A to each of the control rod drive mechanism 64. The control rod drive mechanisms 32 and 64 are operated by the inner control rod cluster withdrawal signal. By operating the control rod drive mechanism 32, all the inner control rod clusters 2 are gradually pulled out from the core fuel region 12, and by operating the control rod drive mechanism 64, a predetermined number of inner control rod clusters 36 are gradually pulled out from the core fuel region 12 and rapidly propagated. Increase the reactor power of reactor 8. When the reactor output reaches the 4th target reactor output, the inner control rod cluster extraction stop signal from the control unit 43 to the control rod drive mechanism 32 based on the inner control rod cluster extraction stop command output from the control panel. Is output, and an inner control rod cluster withdrawal stop signal is output from the control unit 43A to the control rod drive mechanism 64. Therefore, the withdrawal of the inner control rod cluster 2 by the control rod drive mechanism 32 and the withdrawal of the inner control rod cluster 36 by the control rod drive mechanism 64 are stopped. By repeating the withdrawal and withdrawal stop of the inner control rod clusters 2 and 36 in this way, the fast breeder reactor 8 is hatched while the reactor output is maintained at the fourth target reactor output throughout a certain operation cycle. Follow-up operation is continued.

When the operation of the fast breeder reactor 8 in a certain operation cycle is completed, the operation of the fast breeder reactor 8 is stopped. The operation stop command of the fast breeder reactor 8 is output from the control panel to the control units 43 and 43A. The control unit 43 to which the operation stop command is input outputs an operation stop signal to the winding device 30 corresponding to all the control rods 1 and all the control rod drive mechanisms 32. The control unit 43A to which the operation stop command is input outputs an operation stop signal to the take-up device 62 and the control rod drive mechanism 64 corresponding to the rear furnace stop system control rods 23 having a predetermined number of bodies.

The operation of the outer control rod cluster 5 and the inner control rod cluster 2 by the three winding devices 30 and the control rod drive mechanism 32 to which the operation stop signal is input is as described above, and thus the description thereof is omitted here.

When the inner control rod clusters 2 and the outer control rod clusters 5 of all the control rods 1 are fully inserted into the core fuel region 12, the operation of the fast breeder reactor 8 is stopped.

If an abnormal situation occurs in the fast breeder reactor 8 while controlling the reactor output of the fast breeder reactor 8 using a plurality of normal control rods 1 and one rear reactor shutdown system control rod 23, the control chamber The scram signal is output to the control unit 43 from the control panel of the above, and the scram signal is also output to the control unit 43A. The control unit 43 outputs the scrum signal to the control rod holding unit 44 of the normal control rod 1. As described above, the outer control rod cluster 5 is separated from the control rod holding unit 44 and rapidly inserted into the core fuel region 12. The control unit 43A outputs the scrum signal to the control rod holding unit 66 of the rear furnace stop system control rod 23. As a result, the outer control rod cluster 55 is separated from the control rod holding unit 66 and rapidly inserted into the core fuel region 12, and the fast breeder reactor 8 is urgently stopped.

The configuration of the conventional main furnace shutdown system control rod 68 will be described with reference to FIGS. 12 and 13. In the main furnace stop system control rod 68, a plurality of control rod elements 69 are arranged in a cylindrical control rod protection pipe 70 whose upper and lower ends are closed. The control rod element 69 is filled with a plurality of pellets of boron carbide in a sealed cladding tube (not shown). The main reactor shutdown system control rod 68 is arranged in the control rod guide pipe 72 arranged between the fuel assemblies in the core fuel region 12. The main furnace stop system control rod 68 is attached to a drive extension shaft 71 connected to a control rod drive mechanism (not shown).

The number of control rod elements 69 included in the main reactor shutdown system control rod 68 is the number of control rod elements 3 included in the inner control rod cluster 2 and the outer control rod cluster 5 of the control rod 1 used in this embodiment. The number is 21, which is the same as the total number of the included control rod elements 6 (see FIG. 4). Therefore, of the inner control rod cluster 2 and the outer control rod cluster 5, the reactivity value of the control rod 1 when the inner control rod cluster 2 of the control rod 1 is fully inserted into the core fuel region 12 is the main reactor shutdown value. It is smaller than the reactivity value of the main reactor shutdown system control rod 68 when the system control rod 68 is fully inserted into the core fuel region 12.

As described above, in this embodiment, since the inner control rod cluster 2 having a small control rod value is inserted into the core fuel region 12, the output distribution in the axial direction of the core fuel region 12 into which the inner control rod cluster 2 is inserted is inserted. The peak is lower than the peak of the output distribution in the axial direction of the core fuel region 12 into which the conventional main reactor shutdown system control rod 68 is inserted. FIG. 14 shows a core fuel region in the control rod 1 of the present embodiment in a state where the outer control rod cluster 5 is completely pulled out from the core fuel region 12 and the inner control rod cluster 2 is fully inserted into the core fuel region 12. The output distribution in the axial direction of 12 is shown by a solid line. The output distribution in the axial direction when the inner control rod cluster 2 is fully inserted into the core fuel region 12 has a cosine distribution as shown by the solid line. On the other hand, the axial output distribution of the core fuel region 12 when a part of the conventional main reactor shutdown control rod 68 is pulled out from the core fuel region 12 is the conventional output distribution as shown by the broken line in FIG. A large output peak is formed near the lower end of the main reactor stop system control rod. The peak output in the axial output distribution of the core fuel region 12 with the outer control rod clusters 5 fully drawn out of the core fuel region 12 and the inner control rod clusters 2 fully inserted into the core fuel region 12 is It is smaller than the peak of the output of the axial output distribution of the core fuel region 12 when a part of the conventional main reactor shutdown control rod 68 is pulled out from the core fuel region 12. Therefore, when the control rod 1 of this embodiment is used, the thermal margin of the fast breeder reactor 8 in the load following operation increases.

Next, the output distribution in the axial direction of the core fuel region 12 in a state where the outer control rod cluster 5 is completely pulled out from the core fuel region 12 and a part of the inner control rod cluster 2 is inserted into the core fuel region 12. Will be explained. The axial output distribution of the core fuel region 12 in the state where a part of the inner control rod cluster 2 is inserted into the core fuel region 12 is not the cosine distribution as shown by the solid line in FIG. 14, but the inner control rod cluster 2 An output peak is formed near the lower end. Therefore, when the outer control rod cluster 5 is completely pulled out from the core fuel region 12 and a part of the inner control rod cluster 2 is inserted into the core fuel region 12, it is formed near the lower end of the inner control rod cluster 2. The output peak is the output of the cosine distribution in the axial direction of the core fuel region 12 in a state where the outer control rod cluster 5 is completely pulled out from the core fuel region 12 and the inner control rod cluster 2 is fully inserted into the core fuel region 12. Greater than the output peak of the distribution. However, since the control rod value of the inner control rod cluster 2 is smaller than that of the conventional main reactor shutdown system control rod 68, the output peak formed near the lower end of the inner control rod cluster 2 is the conventional main reactor shutdown system. It is smaller than the output peak formed near the lower end of the control rod 68. As described above, even when a part of the inner control rod cluster 2 is inserted into the core fuel region 12, the thermal margin of the fast breeder reactor 8 during the load following operation is increased.

In this embodiment, the rear-end furnace shutdown system control rod 23 also has an inner control rod cluster and an outer control rod cluster, similarly to the control rod 1. Therefore, by using the rear reactor stop system control rod 23 instead of the failed control rod 1, the load following operation of the fast breeder reactor 8 can be performed as in the case where only the control rod 1 is used.

In the load follow-up operation of the fast breeder reactor 8 using the rear reactor stop system control rod 23, the outer control rod cluster 55 of the rear reactor shutdown system control rod 23 is completely pulled out from the core fuel region 12, and the inner control rod cluster 36 is the core. The output distribution in the axial direction of the core fuel region 12 when fully inserted into the fuel region 12 is a cosine distribution as in the case where only the control rods 1 are used, and the output peak of the output distribution is the conventional one. It is smaller than the output peak of the axial output distribution of the core fuel region 12 when a part of the main reactor shutdown system control rod 68 is pulled out from the core fuel region 12. Therefore, when the rear reactor stop system control rod 23 is used, the thermal margin of the fast breeder reactor 8 during the load follow-up operation increases.

Further, the core fuel in a state where the outer control rod cluster 55 of the rear reactor stop system control rod 23 is completely pulled out from the core fuel region 12 and a part of the inner control rod cluster 36 is completely inserted into the core fuel region 12. In the axial output distribution of the region 12, a large output peak is formed near the lower end of the inner control rod cluster 36. However, since the control rod value of the inner control rod cluster 36 is smaller than that of the conventional main reactor shutdown system control rod 68, the output peak formed near the lower end of the inner control rod cluster 36 is the conventional main reactor shutdown system. It is smaller than the output peak formed near the lower end of the control rod 68. As described above, even when a part of the inner control rod cluster 36 is inserted into the core fuel region 12, the thermal margin of the fast breeder reactor 8 during the load following operation is increased.

In the fast breeder reactor 8, the outer control rod cluster 5 of the control rod 1 is moved in the axial direction of the core 11 by the take-up device 30, and the outer control rod cluster 55 of the rear reactor stop system control rod 23 is moved by the take-up device 62 to the core. It is moved in the axial direction of 11. Therefore, the outer control rod clusters 5 and 55 can be moved in the axial direction of the core 11 by a winding device having a simpler structure than the control rod drive mechanism.

In the fast breeder reactor 8, a lower inner control rod guide pipe 26 and a lower outer control rod guide pipe 27 surrounding the lower inner control rod guide pipe 26 are arranged in the core 11, and the inner control rod cluster of the control rod 1 is arranged. 2 is moved in the axial direction of the core 11 in the lower inner control rod guide tube 26, and the outer control rod cluster 5 is moved in the axial direction of the core 11 between the lower inner control rod guide tube 26 and the lower outer control rod guide tube 27. I'm moving it. Therefore, it is possible to prevent the inner control rod cluster 2 and the outer control rod cluster 5 moving in the axial direction of the core 11 from interfering with each other, and the core 11 of each of the inner control rod cluster 2 and the outer control rod cluster 5 can be avoided. Can be smoothly moved in the axial direction.

Further, in the fast breeder reactor 8, a lower inner control rod guide pipe 58 and a lower outer control rod guide pipe 59 surrounding the lower inner control rod guide pipe 58 are arranged in the core 11. Therefore, the inner control rod cluster 36 of the rear reactor stop system control rod 23 is moved in the axial direction of the core 11 in the lower inner control rod guide pipe 58, and the outer control rod cluster 55 is moved to the lower inner control rod guide pipe 58 and the lower part. It is moved in the axial direction of the core 11 between the outer control rod guide pipes 59. Therefore, it is possible to prevent the inner control rod cluster 36 and the outer control rod cluster 55 moving in the axial direction of the core 11 from interfering with each other, and the core 11 of each of the inner control rod cluster 36 and the outer control rod cluster 55 can be avoided. Can be smoothly moved in the axial direction.

The control rods 1 to be operated during the load follow-up operation are arranged in the inner core fuel region 14 rather than the control rods 1 arranged near the center of the core 11, for example, the control rods 1 arranged in the outer core fuel region 15. Further, in the inner core fuel region 14, it is desirable to use the control rods 1 arranged as close to the center of the inner core fuel region 14. The control rod value of the control rod 1 becomes higher as the control rod 1 is arranged near the center of the core 11. Therefore, by using the control rods 1 arranged near the center of the core 11 during the load-following operation, the fluctuation range of the reactor output during the load-following operation can be increased.

Even when it becomes necessary to use the rear-loading reactor stop system control rods 23 during load-following operation, the reactor during load-following operation can be used by using the rear-loading reactor shutdown system control rods 23 arranged near the center of the core 11. The fluctuation range of the output can be increased.

Since the outer control rod cluster 5 of the control rod 1 is detachably connected to the control rod holding unit 44 attached to the rope 31 wound around the rotary drum of the take-up device 30 via the rotary hook 45, the control rod cluster 5 is detachably connected to the control rod holding unit 44. When an abnormal situation occurs in the fast breeder reactor 8, the control rod holding unit 44 to which the scram signal is input activates the rotary hook 45, and the outer control rod cluster 5 can be separated from the control rod holding unit 44. Therefore, even the outer control rod cluster 5 moved in the axial direction of the core 11 by the take-up device 30 can be easily and rapidly inserted into the core fuel region 12 in the abnormal situation of the fast breeder reactor 8.

Further, the outer control rod cluster 55 of the rear reactor stop system control rod 23 can be separated from the control rod holding unit 66 attached to the rope 63 wound around the rotary drum of the take-up device 62 via the rotary hook 45. Since they are connected, when an abnormal situation occurs in the fast breeder reactor 8, the rotary hook 45 is operated by the control rod holding unit 66 to which the scram signal is input, and the reactor output is controlled in place of the failed control rod 1. The outer control rod cluster 55 of the rear reactor shutdown system control rod 23 used in the above can be separated from the control rod holding unit 66. Therefore, even the outer control rod cluster 55, which is moved in the axial direction of the core 11 by the take-up device 62, can be easily and rapidly inserted into the core fuel region 12 in the abnormal situation of the fast breeder reactor 8.

The fast breeder reactor 8 has a rear reactor shutdown system control rod 23 including an inner control rod cluster 36 and an outer control rod cluster 55, and has an outer control rod cluster 5 of all control rods 1 and a predetermined number of rear reactor shutdown system controls. With the outer control rod clusters 55 of the rods 23 fully drawn from the core fuel region 12, the inner control rod clusters 2 of all the control rods 1 and the inner control rod clusters 36 of the rear reactor stop system control rods 23 having a predetermined number of bodies. Can be pulled out from the state of being fully inserted into the core fuel region 12, and the load following operation can be performed while maintaining the fourth target reactor output in a certain operation cycle. In the fast breeder reactor 8 of this embodiment, the range of load following operation can be expanded by using all the control rods 1 and the rear-end reactor stop system control rods 23 having a predetermined number of bodies in combination.

Since the inner control rod clusters 2 of all control rods 1 (or the outer control rod clusters 5 of all control rods 1) are used, the radius of the core fuel region 12 is larger than when some control rods 1 are inserted. The output distribution in the direction is flattened and the thermal margin is improved.

The configuration of the fast breeder reactor in Example 2 which is another suitable embodiment of the present invention will be described with reference to FIGS. 15 to 19. The fast breeder furnace 8A of this embodiment is a winding device that is a first control rod moving device that moves the outer control rod cluster 5 of the control rod 1 in the axial direction of the core 11 in the fast breeder furnace 8 described in the first embodiment. The take-up device 30 is replaced with the control rod drive mechanism 32A, and the take-up device 62, which is the first control rod moving device, moves the outer control rod cluster 55 of the rear reactor stop system control rod 23 in the axial direction of the core 11. It has a configuration replaced with the drive mechanism 64A. The control rod drive mechanisms 32A and 64A are second control rod moving devices. The three control rod drive mechanisms 32A are installed on the upper surface of the support plate 54 provided on the upper surface of the rotary plug 10, and are arranged around the control rod drive mechanism 32. The upper end of the outer control rod cluster 5 existing in the annular region between the lower inner control rod guide tube 26 and the lower outer control rod guide tube 27 is the lower end of each drive extension shaft 33A of the three control rod drive mechanisms 32A. Is linked to. Three control rod drive mechanisms 64A are installed on the upper surface of the support plate 54A provided on the upper surface of the rotary plug 10 and are arranged around the control rod drive mechanism 64. The upper end of the outer control rod cluster 55 existing in the annular region between the lower inner control rod guide pipe 58 and the lower outer control rod guide pipe 59 is the lower end of each drive extension shaft 65A of the three control rod drive mechanisms 64A. Is linked to.

In the fast breeder reactor 8A, the outer control rod cluster, the second control rod moving device for moving the outer control rod cluster in the axial direction of the core 11, the inner control rod cluster, and the inner control rod cluster are moved in the axial direction of the core 11. 2 It has a control rod system including a control rod moving device. The control rod system in the fast breeder reactor 8A specifically moves the inner control rod cluster 2 and the inner control rod cluster 2 of the control rod 1 (main reactor shutdown system control rod) in the axial direction of the core 11. Control rod moving device, outer control rod cluster 5 of control rod 1, second control rod moving device for moving the outer control rod cluster 5 in the axial direction of the core 11, inner control rod cluster 36 of the rear furnace stop system control rod 23, A second control rod moving device that moves the inner control rod cluster 36 in the axial direction of the core 11, an outer control rod cluster 55 of the rear-end reactor stop system control rod 23, and a second control rod cluster 55 that moves the outer control rod cluster 55 in the axial direction of the core 11. 2 Includes control rod moving device. Second control rod movement that moves each of the inner control rod cluster 2 and the outer control rod cluster 5 of the control rod 1 and the inner control rod cluster 36 and the outer control rod cluster 55 of the rear furnace stop system control rod 23 in the axial direction thereof. The device is a control rod drive mechanism.

In the fast breeder reactor 8A, the outer control rod cluster, the second control rod moving device for moving the outer control rod cluster in the axial direction of the core 11, the inner control rod cluster, and the inner control rod cluster are moved in the axial direction of the core 11. 2 It has a control rod system including a control rod moving device. The control rod system in the fast breeder reactor 8A specifically moves the outer control rod cluster 5 and the outer control rod cluster 5 of the control rod 1 (main reactor shutdown system control rod) in the axial direction of the core 11. 2 Control rod moving device, inner control rod cluster 2 of control rod 1, second control rod moving device for moving inner control rod cluster 2 in the axial direction of the core 11, outer control rod cluster 55 of the rear furnace stop system control rod 23. , The second control rod moving device that moves the outer control rod cluster 55 in the axial direction of the core 11, the inner control rod cluster 36 of the rear-end reactor stop system control rod 23, and the inner control rod cluster 36 are moved in the axial direction of the core 11. It includes a second control rod moving device. The second control rod moving device included in the control rod system is a control rod drive mechanism.

In this embodiment, in addition to the inner control rod cluster 2 and the inner control rod cluster 36, the outer control rod cluster 5 is moved in the axial direction of the core 11 by the control rod drive mechanism 32A, and the outer control rod cluster 55 is driven by the control rods. It is moved in the axial direction of the core 11 by the mechanism 64A.

In a certain operation cycle of the fast breeder reactor 8A, the load follow-up operation is carried out at the above-mentioned first target reactor output. When the fast breeder reactor 8A is started in the certain operation cycle, an outer control rod cluster extraction command output from the control panel in the control chamber is input to the control unit 43, and a predetermined number of control rods are input from the control unit 43. The outer control rod cluster withdrawal signal is output to the three control rod drive mechanisms 32A provided for each of the outer control rod clusters 5. Therefore, each of the outer control rod clusters 5 of the control rods 1 having a predetermined number of bodies is pulled out from the core fuel region 12 by the three control rod drive mechanisms 32A, and the reactor output of the fast breeder reactor 8 is the first target reactor. It is raised to the output. When the reactor power reaches its first target reactor power, the control unit 43 drives and stops each of the three control rod drive mechanisms 32A based on the outer control rod cluster pull-out stop command output to the control unit 43. A signal is output. As a result, the movement of the outer control rod cluster 5 of the control rod 1 having a predetermined number of bodies in the axial direction is stopped. The load-following operation of the fast breeder reactor 8A at the first target reactor output continues until the end of a certain operation cycle described above while pulling out the inner control rod cluster 2 as necessary, as in the first embodiment. Will be implemented.

When the load following operation in a certain operation cycle is completed, the inner control rod cluster 2 and the outer control rod cluster 5 are fully inserted into the core fuel region 12 (see FIG. 17), and the operation of the fast breeder reactor 8A is stopped.

In this embodiment as well, as in the first embodiment, the load following operation of the fast breeder reactor 8A can be carried out by using all the control rods 1 and the rear reactor stop system control rods 23 having a predetermined number of bodies together. can. In this load-following operation, the inner control rod cluster 36 of the rear reactor stop system control rod 23 is in the core fuel region while the outer control rod cluster 55 of the rear reactor stop system control rod 23 is completely pulled out from the core fuel region 12. There is a state in which the 12 is fully inserted (see FIG. 18).

When an abnormal event occurs in the fast breeder reactor 8A and the fast breeder reactor 8A is scrammed, each of the inner control rod cluster 36 and the outer control rod cluster 55 of the rear reactor shutdown system control rod 23 is fully inserted into the core fuel region 12. (Fig. 19).

In this embodiment, among the effects generated in the first embodiment, the effect obtained by installing the take-up device 30 and the control rod holding unit 44, and the effect obtained by installing the take-up device 62 and the control rod holding unit 66 are excluded. Other effects can be obtained. Further, in this embodiment, since the outer control rod cluster 5 is moved in the axial direction of the core 11 by the control rod drive mechanism 32A, the combustion state of the nuclear fuel material in the fuel assembly in the core 11 as in the first embodiment. It is not necessary to change the number of control rods 1 inserted during load follow-up operation due to the difference in the temperature of the coolant (liquid sodium 24), and the operation of the outer control rod cluster 5 of the control rod 1 is simplified. .. Further, the output peaking in the radial direction of the core fuel region 12 can also be suppressed.

The control rod operation method of the fast breeder reactor in Example 3 which is another suitable embodiment of the present invention will be described with reference to FIGS. 15 and 20 to 23. The fast breeder reactor to which the control rod operation method of this embodiment is applied is the fast breeder reactor 8A described in the second embodiment, the control rod 1 including the inner control rod cluster 2 and the outer control rod cluster 5, and the inner control rod. It has a rear reactor shutdown system control rod 23 including rod cluster 36 and outer control rod cluster 55.

In the control rod operation method of the fast breeder reactor of this embodiment, when the load following operation of the fast breeder reactor 8A is performed, the inner control rod cluster 2 of the control rod 1 is completely pulled out from the core fuel region 12, and the control rod 1 is operated. There is a state in which the outer control rod cluster 5 is fully inserted into the core fuel region 12. In the control rod operation method of the fast breeder reactor of the present embodiment in which such a state exists, the outer control rod cluster 5 of the control rod 1 is completely pulled out from the core fuel region 12 in the load follow-up operation, and the control rod 1 is operated. It is different from the control rod operation method of each of the fast breeder reactors of Examples 1 and 2 in which the inner control rod cluster 2 is fully inserted into the core fuel region 12.

When the load-following operation in a certain operation cycle is started, the inner control rod clusters 2 of the predetermined number of control rods 1 are inserted while the outer control rod clusters of all the control rods 1 are fully inserted into the core fuel region 12. Operated by the corresponding control rod drive mechanism 32, the core fuel region 12 is fully pulled out (see FIG. 20). As a result, the reactor output of the fast breeder reactor 8A rises to the target reactor output during the load-following operation. After that, if necessary, the outer control rod cluster 5 of the control rod 1 having a predetermined number of bodies is pulled out from the core fuel region 12 by the control rod drive mechanism 32A, and the reactor output is held at the target reactor output. The operation is continued until the end of a certain operation cycle described above.

In this embodiment as well, as in the first embodiment, by using all the control rods 1 and the rear reactor stop system control rods 23 having a predetermined number of bodies in combination, the load tracking of the fast breeder reactor 8A is performed in a certain operation cycle. The operation can be carried out. Similarly to the control rod 1, the inner control rod cluster 36 is completely pulled out from the core fuel region 12 by the control rod drive mechanism 64 in the rear reactor stop system control rod 23 having a predetermined number of bodies to be used together (see FIG. 22). After that, when the reactor output of the fast breeder reactor 8A becomes lower than the target reactor output during the load follow-up operation, the outer control rod cluster 55 of the rear reactor shutdown system control rod 23 having a predetermined number of bodies is subjected to the control rod drive mechanism 64A. It is pulled out from the core fuel region 12 to raise the reactor power to the target reactor power. In the above certain operation cycle, the load following operation of the fast breeder reactor 8A at the target reactor output is performed at the end of the certain operation cycle while pulling out the outer control rod cluster 55 from the core fuel region 12 as needed. Can be continued until.

In this embodiment as well, as in the first embodiment, the load following operation of the fast breeder reactor 8A can be carried out by using all the control rods 1 and the rear reactor stop system control rods 23 having a predetermined number of bodies together. can. In this load-following operation, the inner control rod cluster 36 of the rear reactor stop system control rod 23 is completely pulled out from the core fuel region 12 and the outside of the rear reactor stop system control rod 23. There is a state in which the control rod clusters 55 are fully inserted into the core fuel region 12 (see FIG. 22).

When an abnormal event occurs in the fast breeder reactor 8A and the fast breeder reactor 8A is scrammed, each of the inner control rod cluster 36 and the outer control rod cluster 55 of the rear reactor shutdown system control rod 23 is fully inserted into the core fuel region 12. (Fig. 23).

The control rod value of the outer control rod cluster 5 pulled out from the core fuel region 12 while the inner control rod cluster 2 is fully pulled out from the core fuel region 12 is the inner control pulled out from the core fuel region 12 in FIG. Greater than the control rod value of the rod cluster 2.

In this embodiment, among the effects generated in the first embodiment, the effect obtained by installing the take-up device 30 and the control rod holding unit 44, and the effect obtained by installing the take-up device 62 and the control rod holding unit 66 are excluded. Other effects can be obtained. Further, since the inner control rod cluster 2 and the outer control rod cluster 5 have different reactivity values as described above, the range (type) of the reactor output fluctuation can be doubled. Therefore, by independently moving the inner control rod cluster 2 and the outer control rod cluster 5 having different control rod values in the axial direction of the core 11, the load following operation can be performed diligently.

In this embodiment, when the load following operation is performed, the outer control rod cluster 5 is pulled out from the core 11 instead of pulling out the inner control rod cluster 2 as in the first and second embodiments. By pulling out the outer control rod cluster 5, the reactor output during load-following operation can be further reduced.

In each of the first to third embodiments, the inner control rod cluster 2 of the control rod 1 is pulled out while the outer control rod cluster 5 of the control rod 1 is fully pulled out during the load follow-up operation. Each case of pulling out the outer control rod cluster 5 with the outer control rod cluster 5 pulled out is described. However, the outside control of the control rod 1 is also performed when compensating for the reactivity of the fast breeder reactor 8 (or the fast breeder reactor 8A) during normal operation (for example, during rated operation), not during load-following operation. It is also possible to pull out the inner control rod cluster 2 with the rod cluster 5 fully pulled out, or to pull out the outer control rod cluster 5 with the inner control rod cluster 2 of the control rod 1 fully pulled out. Is. In particular, if more control rods 1 in the core fuel region 12 are used when compensating for combustion of the reactivity, the output distribution in the radial direction of the core fuel region 12 can be flattened, and the thermal margin can be obtained. Can be increased.

In Examples 1 to 3, U-Pu-10Zr, which is a ternary alloy, is used as the nuclear fuel material in each of the inner core fuel assembly 18 and the outer core fuel assembly 19 loaded in the core 11. MOX fuel may be used as the nuclear fuel material for each of the inner core fuel assembly 18 and the outer core fuel assembly 19 instead of the U-Pu-10Zr.

Further, in Examples 1 to 3, liquid sodium is used as a cooling material for the fast breeder furnace, but a liquid metal other than sodium such as lead and lead bismuth may be used instead of the liquid sodium.

1 ... Control rods (main reactor shutdown system control rods), 2,36 ... Inner control rod clusters, 5,55 ... Outer control rod clusters, 8,8A ... Fast breeder reactors, 9 ... Reactor vessels, 10 ... Rotating plugs, 11 ... Core, 12 ... Core fuel region, 14 ... Inner core fuel region, 15 ... Outer core fuel region, 18 ... Inner core fuel assembly, 19 ... Outer core fuel assembly, 23 ... Rear reactor stop system control rods, 24 ... Liquid sodium, 26,58 ... Lower inner control rod guide tube, 27,59 ... Lower outer control rod guide tube, 30,62 ... Winding device, 31,63 ... Rope, 32, 32A, 64, 64A ... Control rod Drive mechanism, 33, 33A, 65, 65A ... Drive extension shaft, 44, 66 ... Control rod holding unit, 45 ... Rotating hook, 50 ... Upper core support plate.

Claims (15)

A control rod of a fast reactor comprising an inner control rod cluster and an annular outer control rod cluster surrounding the inner control rod cluster. It is provided with a reactor vessel and a rotary plug rotatably installed at the upper end of the reactor vessel and covering the reactor vessel.
Each of the inner control rod cluster and the outer control rod cluster of the main reactor shutdown system control rod, which is the control rod according to claim 1, is arranged in the core arranged in the reactor vessel.
A control rod moving device for moving the inner control rod cluster of the main reactor stop system control rod in the axial direction of the core is installed in the rotating plug.
A fast reactor characterized in that another control rod moving device for moving the outer control rod cluster of the main reactor shutdown system control rod in the axial direction of the core is installed in the rotary plug. A core support plate arranged below the core in the reactor vessel is installed in the reactor vessel, and the lower end of the first inner control rod guide tube arranged in the core is attached to the core support plate. The lower end of the second outer control rod guide tube, which is attached and arranged in the core and surrounds the first inner control rod guide tube, is attached to the core support plate and the inner side of the main furnace stop system control rod. The control rod clusters are arranged in the first inner control rod guide pipes, and the outer control rod clusters of the main reactor shutdown system control rods are located between the first inner control rod guide pipes and the second outer control rod guide pipes. The high speed furnace according to claim 2, which is arranged in the formed annular region. In addition to the main furnace stop system control rods, a rear-end furnace stop system control rods are used.
Like the main reactor shutdown system control rods, the rear-end reactor shutdown system control rods have an inner control rod cluster and an annular second outer control rod cluster surrounding the inner control rod clusters.
Each of the inner control rod cluster and the outer control rod cluster of the rear reactor shutdown system control rod is arranged in the core arranged in the reactor vessel.
A control rod moving device for moving the inner control rod cluster of the rear reactor stop system control rod in the axial direction of the core is installed in the rotating plug.
The fast reactor according to claim 3, wherein another control rod moving device for moving the outer control rod cluster of the rear reactor stop system control rod in the axial direction of the core is installed in the rotary plug. The lower end of the second inner control rod guide tube arranged in the core is attached to the core support plate, and the second outer control rod guide is arranged in the core and surrounds the second inner control rod guide tube. The lower end of the pipe is attached to the core support plate, the inner control rod cluster of the rear-end furnace stop system control rod is arranged in the second inner control rod guide tube, and the outside of the rear-end furnace stop system control rod. The high speed furnace according to claim 4, wherein the control rod clusters are arranged in an annular region formed between the second inner control rod guide tube and the second outer control rod guide tube. The method according to any one of claims 2 to 5, wherein the other control rod moving device for moving the outer control rod cluster has a different moving mechanism from the control rod moving device for moving the inner control rod cluster. Fast reactor. The other control rod moving device for moving the outer control rod cluster is a take-up device, and the inner control rod cluster is suspended on a rope wound by the take-up device.
The fast reactor according to claim 6, wherein the control rod moving device for moving the inner control rod cluster is a control rod driving mechanism. The fast reactor according to claim 7, wherein the inner control rod cluster is detachably connected to a control rod holding unit attached to the rope and suspended from the rope via the control rod holding unit. The control rod moving device for moving the inner control rod cluster and the other control rod moving device for moving the outer control rod cluster are each according to any one of claims 2 to 5, which is a control rod driving mechanism. The fast furnace described. A control rod of a fast reactor having the inner control rod cluster and the outer control rod cluster of the main reactor shutdown system control rod, which is the control rod according to claim 1, arranged in the core fuel region of the core in the reactor vessel. It ’s an operation method,
Either the inner control rod cluster or the outer control rod cluster is withdrawn from the core fuel region, and the control rod clusters of the inner control rod cluster and the outer control rod cluster other than those drawn from the core fuel region are obtained. Is a control rod operating method for a fast reactor, characterized in that it remains fully inserted in the core fuel region. The control rod of the fast reactor according to claim 10, wherein the reactor output of the fast reactor is increased to the target reactor output by pulling either the inner control rod cluster or the outer control rod cluster from the core fuel region. Method of operation. When the reactor power of the fast reactor drops from the target reactor power after any of the inner control rod clusters and the outer control rod clusters have been completely withdrawn from the core fuel region, the inner control rod clusters and 11. Claim 11 of the outer control rod clusters, in which control rod clusters other than those completely drawn from the core fuel region are pulled out from the core fuel region to maintain the reactor output of the fast reactor at the target reactor output. How to operate the control rods of the fast reactor described in. The fast reactor has, like the main reactor shutdown system control rods, an inner control rod cluster and a rear reactor shutdown system control rod including an annular second outer control rod cluster surrounding the inner control rod clusters.
Either the inner control rod cluster or the outer control rod cluster of the rear reactor stop system control rod is pulled out from the core fuel region, and the inner control rod cluster and the outer control rod cluster are pulled out from the core fuel region. The control rod operating method for a high-speed reactor according to claim 10, wherein control rod clusters other than those removed are also fully inserted into the core fuel region. The fast reactor is rotatably installed at the upper end of the reactor vessel and includes a rotary plug that covers the reactor vessel and a take-up device installed on the rotary plug.
Either the inner control rod cluster or the outer control rod cluster drawn from the core fuel region is moved axially in the core fuel region by the take-up device.
One of the inner control rod clusters and the outer control rod clusters pulled out of the core fuel region, detachably coupled to a control rod holding unit attached to a rope wound up by the take-up device, is a scram signal. The method for operating a control rod of a fast reactor according to any one of claims 10 to 12, wherein the control rod holding unit is separated from the control rod holding unit and falls in the core fuel region. The fast reactor is rotatably installed at the upper end of the reactor vessel and includes a rotary plug that covers the reactor vessel and a control rod drive mechanism installed in the rotary plug.
One of claims 10 to 12, wherein either the inner control rod cluster or the outer control rod cluster drawn from the core fuel region is axially moved by the control rod drive mechanism. The control rod operation method for the fast reactor described in the section.

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