Installation method for reactor structure of fast reactor

Abstract

This installation method is a method for installing a reactor structure of a fast reactor (S100). The fast reactor (S100) includes a large rotating plug (14), a small rotating plug (15), a reactor core upper mechanism (30) provided with a plurality of control rod drive mechanisms (40), a strongback (17), and a plurality of control rod assemblies (27) disposed in a reactor core component group inserted into a diagrid (18). The plurality of control rod drive mechanisms (40) are provided and disposed in one-to-one correspondence with the plurality of control rod assemblies (27), and move control rods (27a) of the control rod assemblies (27) individually in the up-down direction. The installation method comprises an adjustment step for moving the control rod drive mechanisms (40) so that each control rod drive mechanism (40) is positioned above the control rod assembly (27) corresponding to the control rod drive mechanism (40) by rotating the large rotating plug (14), the small rotating plug (15), and the reactor core upper mechanism (30).

Description

Method for installing reactor structure of fast reactor

[0001] The present invention relates to a method for installing a reactor structure of a fast reactor.

[0002] Conventionally, control rods have been used to start, stop, and change the output of a fast breeder reactor (FBR). Patent Document 1 discloses a control rod drive mechanism connected to the control rods.

[0003] Japanese Patent Application Laid-Open No. 2009-085650

[0004] When installing a fast reactor, a problem occurs in that the dimensional error between the control rod drive mechanism and the control rod assembly is large due to dimensional errors and assembly errors of the components that make up the fast reactor. If the dimensional error between the control rod drive mechanism and the control rod assembly is large, there is a risk that the components will interfere with each other physically, causing damage to the components and reducing the performance of the fast reactor.

[0005] Therefore, the present invention has been made in consideration of these points, and an object of the present invention is to provide a method for installing a reactor structure of a fast reactor that can reduce dimensional errors between a control rod drive mechanism and a control rod assembly.

[0006] One embodiment of the installation method of the present invention is a method for installing a reactor structure of a fast reactor, the fast reactor comprising: a large rotation plug configured to be rotatable about a first rotation axis in a vertical direction on a roof slab; a small rotation plug configured to be rotatable relative to the large rotation plug about a second rotation axis offset from the first rotation axis; an upper core mechanism configured to be rotatable relative to the small rotation plug and provided with a plurality of control rod drive mechanisms; a strongback located near the bottom of a main vessel; and a plurality of control rod assemblies arranged among a group of core components inserted into a diagrid located above the strongback, the plurality of control rod drive mechanisms being provided in an arrangement corresponding to the plurality of control rod assemblies and moving the control rods of the control rod assemblies up and down individually, and the installation method includes an adjustment step of rotating the large rotation plug, the small rotation plug, and the upper core mechanism to move the control rod drive mechanisms so that each control rod drive mechanism is positioned above the control rod assembly corresponding to the control rod drive mechanism.

[0007] The adjusting step may include rotating the large rotation plug, then rotating the small rotation plug, and then rotating the upper core mechanism.

[0008] The fast reactor may have a diagrid arranged on top of the strongback, and the adjustment step may include rotating the large rotating plug and then rotating the small rotating plug so that the distance between the center of the diagrid and the center of the upper core mechanism in a plan view is shortened.

[0009] The adjusting step may include rotating the core upper mechanism so that each of the plurality of control rod drive mechanisms is positioned above a corresponding one of the plurality of control rod assemblies.

[0010] The control rod drive mechanism may have a control rod drive shaft guide tube and a control rod drive shaft that moves up and down inside the control rod drive shaft guide tube, and the installation method may further include a first measurement step of temporarily installing the control rod drive mechanism and measuring an installation angle of the control rod drive shaft guide tube, and a first adjustment step of placing a first shim member between a component constituting the control rod drive mechanism and a part of the upper core mechanism and adjusting the installation angle of the control rod drive shaft guide tube so that the extension direction of the control rod drive shaft guide tube approaches the vertical direction.

[0011] The above installation method may further include a second measurement step of temporarily installing the diagrid and measuring the installation angle of the diagrid, and a second adjustment step of placing a second shim member between the diagrid and the strongback to adjust the installation angle of the diagrid so that the extension direction of the diagrid approaches the vertical direction.

[0012] The present invention has the effect of providing a method for installing a reactor structure of a fast reactor that can reduce dimensional errors between a control rod drive mechanism and a control rod assembly.

[0013] 8( a ) is a cross-sectional view showing the configuration of a fast reactor;

[0033] FIG. 8( a ) is a view showing the state of the fast reactor as viewed from above;

[0034] FIG. 8( b ) is an enlarged schematic view of a group of core components arranged in a core barrel as viewed from the top side;

[0035] FIG. 8( c ) is a view showing the structure of a control rod assembly and a part of the control rod drive mechanism;

[0036] FIG. 8( c ) is a view for explaining the configuration of the upper core mechanism and the control rod drive mechanism;

[0037] FIG. 8( a ) is a schematic view showing the state after the state of FIG. 8( a ) is a diagram showing the specific orientation of a plurality of control rod assemblies in the state of FIG. 8( a ).

[0038] FIG. 8( c ) is a view for explaining the movement of the control rod drive mechanism;

[0039] FIG. 8( a ) is a schematic view showing the state in which the control rod drive mechanism is slightly tilted with respect to the vertical direction and the state in which a shim member is arranged;

[0039] FIG. 8( b ) is a view showing the state in which a shim member is interposed in a diagrid.

[0014] The configuration of a fast reactor will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of a fast reactor. FIG. 2 is a view showing the fast reactor as seen from above. Arrows in FIG. 1 indicate the flow of sodium, which is the coolant. In the following, terms indicating directions such as "upper," "lower," "horizontal," and "vertical" are used according to the orientation of objects depicted in the drawings, but these terms are not intended to limit the present invention. The "vertical direction" corresponds to the height direction of the main vessel.

[0015] The fast reactor S100 is, for example, a tank-type fast reactor, which extracts energy by controlling a nuclear fission chain reaction using, for example, uranium, plutonium, etc. as fuel. The fast reactor S100 includes, as its main components, a main vessel 10, a roof slab 11, a reactor core 20, an upper core mechanism 30, a control rod drive mechanism 40, an intermediate heat exchanger 50, and a circulation pump 60.

[0016] The present invention relates to a method for installing a fast reactor S100. Before describing the installation method in detail, the configuration of the fast reactor S100 will be described first.

[0017] (Main Vessel) The main vessel 10 is a cylindrical vessel with a bottom and an open top, and has a diameter of, for example, about 15 m to 20 m. The main vessel 10 accommodates a reactor core 20 together with sodium, which is the primary system coolant. The main vessel 10 is provided with an upper core mechanism 30, a control rod drive mechanism 40, an intermediate heat exchanger 50, a circulation pump 60, and the like. The upper end side of the main vessel 10 is closed by a roof slab 11. A partition plate 19 is provided inside the main vessel 10.

[0018] A strongback 17 and a diagrid 18 are provided near the bottom of the main vessel 10. The strongback 17 is a member on which the diagrid 18 is placed.

[0019] The diagrid 18 is disposed on top of the strongback 17 and supports the core barrel 10a. The diagrid 18 is a frame-shaped member that forms a space through which coolant passes. Core components are inserted into the diagrid 18, including multiple control rod assemblies (described in detail below). The diagrid 18 is fixed to the strongback 17 by, for example, bolting (including a fastening method in which nuts are fastened to fixedly disposed bolts).

[0020] (Roof slab and surrounding structure) The roof slab 11 is a lid that is placed on top of the main container 10 and closes the main container 10. The structure of the roof slab 11 viewed from the top side will be described. As shown in FIG. 2 , the roof slab 11 includes a roof slab member 12 and a rotating plug 13. The roof slab member 12 is a structure that covers the top of the main container 10. Specifically, the roof slab member 12 is a member that is open in the central region, and covers the top of the main container 10 in the region around the rotating plug 13.

[0021] The rotary plug 13 is arranged in the central region of the roof slab 11, inside the roof slab member 12. The rotary plug 13 includes a large rotary plug 14 and a small rotary plug 15.

[0022] The large rotary plug 14 has, for example, a circular outline. The large rotary plug 14 is configured to be rotatable about a first rotation axis Xa. The first rotation axis Xa is an axis extending in the vertical direction. For example, the first rotation axis Xa is coaxial with the central axis of the main container 10 (see FIG. 2 ).

[0023] As an example, the large rotation plug 14 is configured to be manually rotated by an operator. In the present invention, the large rotation plug 14 may be configured to be rotated by power from a drive source such as a motor. The drive source may be operated in response to an operator's operation.

[0024] The small rotary plug 15 is rotatably arranged relative to the large rotary plug 14. In this example, the small rotary plug 15 has a circular outline, similar to the large rotary plug 14. The small rotary plug 15 is arranged inside the outline of the large rotary plug 14. The small rotary plug 15 rotates around a second rotation axis Xb located at its center. The second rotation axis Xb is offset from the first rotation axis Xa in the plan view of FIG. 2. The second rotation axis Xb is an axis extending in the vertical direction.

[0025] Like the large rotation plug 14, the small rotation plug 15 is configured to be manually rotated by an operator, for example. The small rotation plug 15 may be configured to rotate by power from a drive source such as a motor, and the drive source may be operated in response to an operator's operation.

[0026] The small rotary plug 15 is provided with an upper core mechanism 30. The upper core mechanism 30 is provided with a plurality of control rod drive mechanisms 40, which will be described later with reference to other drawings.

[0027] (Core) The core 20 includes fuel assemblies, control rod assemblies, and the like. As shown in FIG. 1 , the core 20 is accommodated inside a core barrel 10a (specifically, in the center of the main vessel 10 in a plan view) provided in the main vessel 10. The core barrel 10a forms a space in which the core 20, a shield (radial shield), and the like are disposed. Coolant is supplied to the core barrel 10a from a circulation pump 60 via piping 61 and a diagrid 18, and is configured to pass through the interior of the core components to the upper plenum side.

[0028] 3 is an enlarged schematic diagram of the core components arranged in the core barrel 10a as viewed from above. The core 20 includes fuel assemblies 25 and control rod assemblies 27. For convenience of illustration, only some of the components are labeled with the reference numerals 25 and 27 in FIG. 3.

[0029] The fuel assembly 25 is an assembly in which a plurality of fuel rods are bundled together. In the reactor core 20, the plurality of fuel assemblies 25 are arranged in a densely packed state.

[0030] The control rod assemblies 27 are assemblies for controlling the output of the fast reactor S100. A plurality of control rod assemblies 27 are arranged among a plurality of fuel assemblies 25, dispersed within the reactor core 20. The number of control rod assemblies 27 is not limited to a specific number.

[0031] (Control Rod Drive Mechanism) Figure 4 is a diagram showing the structure of a control rod assembly and a part of the control rod drive mechanism. As shown in Figure 4, the control rod assembly 27 has a control rod 27a and a guide tube 27b. The guide tube 27b is formed in a cylindrical shape. The control rod 27a is disposed inside the guide tube 27b and is provided so as to be movable in the axial direction (vertical direction). The control rod 27a moves up and down in this manner to control nuclear fission in the reactor core 20.

[0032] 5 is a diagram illustrating the configuration of the above core structure and the control rod drive mechanism. The above core structure (ACS) 30 has an overall cylindrical shape and is disposed above the reactor core 20. The above core structure 30 is installed relative to the small rotation plug 15. The above core structure 30 is provided with a plurality of control rod drive mechanisms 40, as well as various measuring instruments (not shown), such as thermometers and fuel damage detectors. In FIG. 5, only one control rod drive mechanism 40 is depicted for ease of explanation.

[0033] The control rod drive mechanism 40 is a mechanism that raises and lowers the control rods 27a of the control rod assembly 27. As shown in FIG. 4 , the control rod drive mechanism 40 has a control rod drive shaft guide tube 43 and a control rod drive shaft 45.

[0034] The control rod drive mechanism guide tube (CRDGT) 43 is formed in a cylindrical shape. The control rod drive mechanism guide tube 43 is provided so as to extend in the vertical direction when the fast reactor S100 is in an assembled state. The control rod drive mechanism guide tube 43 is installed in the upper core mechanism 30, for example.

[0035] The control rod drive shaft 45 is a rod-shaped member disposed inside the control rod drive shaft guide tube 43. The control rod drive shaft 45 is configured to move up and down (i.e., move up and down) inside the control rod drive shaft guide tube 43. The control rod drive shaft 45 moves up and down by, for example, a driving force from a driving source (not shown).

[0036] The control rod drive shaft 45 is configured so that its lower end can be connected to the control rod 27 a. When the control rod drive shaft 45 is connected to the control rod 27 a, the control rod 27 a moves up and down by raising and lowering the control rod drive shaft 45.

[0037] In this embodiment, a plurality of control rod drive mechanisms 40 are provided. Specifically, the number of control rod drive mechanisms 40 provided corresponds to the number of control rod assemblies 27.

[0038] Since the explanation using drawings showing a large number of control rod assemblies 27 and a large number of control rod drive mechanisms 40 would be complicated, the following explanation will be simplified with reference to FIG. 6. FIG. 6 is a schematic diagram showing a simplified configuration of the control rod assemblies and control rod drive shaft guide tubes. FIG. 6 is a view from the top side. In this embodiment, as shown in FIG. 6(b), a plurality of control rod assemblies 27 are arranged at predetermined positions. In this example, control rod assembly 27-1 to control rod assembly 27-4 are arranged in a predetermined positional relationship with each other.

[0039] 6(a), control rod drive mechanisms 40-1 to 41-4 are provided as the multiple control rod drive mechanisms 40. The control rod drive mechanisms 40 are provided so that the control rod drive mechanism 40-1 corresponds to the position of the control rod assembly 27-1, the control rod drive mechanism 40-2 corresponds to the position of the control rod assembly 27-2, the control rod drive mechanism 40-3 corresponds to the position of the control rod assembly 27-3, and the control rod drive mechanism 40-4 corresponds to the position of the control rod assembly 27-4.

[0040] When the fast reactor S100 is in an assembled state, the control rod drive mechanisms 40 are positioned above the corresponding control rod assemblies 27, which allows the control rods 27a of the control rod assemblies 27 to be moved up and down smoothly by the control rod drive mechanisms 40. In this regard, it is desirable that the fast reactor S100 be installed so that each control rod drive mechanism 40 is positioned above the control rod assembly 27 corresponding to that control rod drive mechanism 40. This will be described in detail later in the description of the installation method according to the present invention.

[0041] 1 and 2 again. The circulation of coolant within the main vessel 10 is well known, but will be briefly described below. The partition plate 19 is, for example, an annular member and is provided to divide the interior of the main vessel 10 into an upper plenum and a lower plenum. The upper plenum and the lower plenum are connected to each other via a circulation pump 60, piping 61, a diagrid 18, the core barrel 10a, and an intermediate heat exchanger (IHX) 50.

[0042] The intermediate heat exchanger 50 is a heat exchanger that cools the primary system coolant, whose temperature has been raised by heat from the reactor core 20, by exchanging heat between the primary system coolant and the secondary system coolant (not shown) inside the intermediate heat exchanger 50. The intermediate heat exchanger 50 is formed in a cylindrical shape. The intermediate heat exchanger 50 is arranged vertically so as to penetrate the roof slab 11 and the partition plate 19. The intermediate heat exchanger 50 has an entrance window 51 located in the upper plenum and an exit window 52 located in the lower plenum. The entrance window 51 is an opening through which high-temperature coolant in the upper plenum flows in. The exit window 52 is an opening through which coolant that has passed through the interior of the intermediate heat exchanger 50 flows out to the lower plenum.

[0043] The circulation pump 60 is a pump for circulating the coolant. Similar to the intermediate heat exchanger 50, the circulation pump 60 also extends vertically so as to penetrate the roof slab 11 and the partition plate 19. The circulation pump 60 pumps the coolant to the diagrid 18 via piping 61 located in the lower plenum.

[0044] The coolant pumped to the diagrid 18 by the circulation pump 60 flows through the diagrid 18 and upward within the core barrel 10a while thermally contacting the fuel assemblies, shields, control rod assemblies, and other components arranged within the core barrel 10a. After receiving heat from the core 20, the coolant reaches, for example, approximately 500°C and then flows into the upper plenum. The coolant then flows into the intermediate heat exchanger 50 through its inlet window 51. The coolant is then cooled to, for example, approximately 400°C within the intermediate heat exchanger 50. The cooled coolant then flows downward within the intermediate heat exchanger 50 and exits through the outlet window 52 of the lower plenum.

[0045] The coolant that flows out of the outlet window 52 and into the lower plenum is sucked in by the circulation pump 60. The sucked coolant is pumped back to the diagrid 18 by the action of the circulation pump 60. In this way, the coolant cools the reactor core 20 while circulating within the main vessel 10.

[0046] Although FIG. 2 shows a specific example of the arrangement of the intermediate heat exchanger 50, the circulation pump 60, and the like, the number and arrangement positions of these components may be changed as appropriate depending on the specifications of the fast reactor S100, etc.

[0047] (Method of Installing a Fast Reactor) As described above, in the fast reactor S100, the operation of the fast reactor S100 is controlled by vertically moving the control rods 27a of the reactor core 20 by the control rod drive mechanism 40. In such a configuration, it is desirable to keep the amount of misalignment (meaning the amount of misalignment between one central axis and the other central axis in a plan view) between the control rod drive mechanism 40 and the corresponding control rod assembly 27 small.

[0048] On the other hand, in the manufacture of the fast reactor S100, dimensional errors may become large due to the dimensional accuracy and assembly accuracy of each component. Specifically, there is a possibility that the amount of misalignment between the upper core mechanism 30, in which the control rod drive mechanism 40 is provided, and the core barrel 10a and diagrid 18, in which the control rod assemblies 27 are loaded, may become large. As a result, the amount of misalignment between the control rod drive mechanism 40 and the corresponding control rod assembly 27 may become large.

[0049] Therefore, in this embodiment, the fast reactor S100 is installed in the following steps. Fig. 7 is a flowchart of an example of a method for installing a fast reactor according to this embodiment. Fig. 8 is a diagram for explaining the method for installing a fast reactor. Fig. 9 is a diagram for explaining the method for installing a fast reactor, showing a state subsequent to the state shown in Fig. 8. Fig. 10 is a diagram showing a specific orientation of a plurality of control rod assemblies in the state shown in Fig. 8(a).

[0050] The following installation process is assumed to start with a plurality of control rod assemblies 27 and the like positioned inside the diagrid 18 in the main vessel 10. In this example, the plurality of control rod assemblies 27 are assumed to be slightly rotated counterclockwise about the axis Xc from their intended positions (shown by dashed lines), as shown in FIG.

[0051] First, in step S1, an operator identifies a predetermined reference position (meaning a position in a plan view) of the diagrid 18. Since the diagrid 18 and the control rod assemblies 27 are both components provided on the main vessel 10 side, it is possible to identify the reference position of the diagrid 18 and then identify the position of the control rod assemblies 27 based on the identified position.

[0052] In the example of Figure 8, as shown by the dashed double-dashed line in Figure 8(a), it is assumed that the multiple control rod assemblies 27 are slightly shifted to the upper left and top position relative to the multiple control rod drive mechanisms 40 on the temporarily installed upper core mechanism 30 (although not shown in this figure, in this state the diagrid 18 on which the multiple control rod assemblies 27 are arranged is also slightly shifted to the upper left and top position).

[0053] The reference position of the diagrid 18 is determined, for example, by detecting the position of a portion of the diagrid 18. Specifically, the center position of the diagrid 18 may be determined to determine the amount of deviation of the diagrid 18 from a predetermined reference position (and thus the amount of deviation of the multiple control rod assemblies 27). As a non-limiting example, assuming that the diagrid 18 is installed, the amount of deviation between the centers of the diagrid 18 and the upper core mechanism 30 may be measured after the rotating plug 13, upper core mechanism 30, and control rod drive mechanism 40 are all installed on the roof slab 11 side. This measurement may be performed, for example, by using a plumb bob (a method using a hanging weight) or laser measurement.

[0054] Next, in step S2, if the identified position of the diagrid 18 deviates from the target position by a predetermined amount or more, the operator determines, as an example, the amount of rotation of the large rotation plug 14 and the small rotation plug 15 required to position the plurality of control rod drive mechanisms 40 above the plurality of control rod assemblies 27. In addition, the operator determines the amount of rotation of the upper core mechanism 30 about the vertical axis required to position the plurality of control rod drive mechanisms 40 at appropriate positions relative to the plurality of control rod assemblies 27.

[0055] The determination of the rotation amount may be performed using an imaging device and a computer. Specifically, in order to position the plurality of control rod drive mechanisms 40 above the plurality of control rod assemblies 27, the computer may calculate the rotation amount of the large rotation plug 14, the rotation amount of the small rotation plug 15, and the rotation amount of the upper core mechanism 30 required to reduce the deviation between the positions of the plurality of control rod assemblies 27 and the positions of the plurality of control rod drive mechanisms 40, based on an image of the loading positions of the plurality of control rod assemblies 27 on the diagrid 18 captured by the imaging device. In addition to the rotation amount, the direction of rotation (clockwise or counterclockwise) may also be determined. In determining this rotation direction, the direction that reduces the rotation amount to the target position may be selected from clockwise and counterclockwise.

[0056] It should be noted that step S2 is not an essential step, and an operator may, for example, visually rotate the large rotation plug 14 and the small rotation plug 15 so that the plurality of control rod drive mechanisms 40 are positioned above the plurality of control rod assemblies 27. During the construction of the fast reactor S100, an operator can enter the main vessel 10, and therefore such work can also be performed by an operator using his or her visual inspection.

[0057] Next, in step S3, the worker rotates the large rotation plug 14. Specifically, the worker rotates the large rotation plug 14 around the first rotation axis Xa so as to change from the state shown in FIG. 8( a) to the state shown in FIG. 8( b). In this example, the large rotation plug 14 rotates counterclockwise by approximately 45° from the state shown in FIG. 8( a) to the state shown in FIG. 8( b). Accordingly, the small rotation plug 15 also rotates in the same direction.

[0058] Next, in step S4, the worker rotates the small rotation plug 15. Specifically, the worker rotates the small rotation plug 15 around the second rotation axis Xb so as to change from the state shown in Fig. 8(b) to the state shown in Fig. 9. In this example, the small rotation plug 15 rotates clockwise by several degrees from the state shown in Fig. 8(b) to the state shown in Fig. 9.

[0059] As a result of the rotation of the large rotating plug 14 and the small rotating plug 15 as described above, the control rod drive mechanisms 40 move above the control rod assemblies 27. In one example, the large rotating plug 14 and the small rotating plug 15 are rotated so that the distance between the center of the diagrid and the center of the upper core mechanism in a plan view becomes shorter than a predetermined threshold. After the rotation, as shown in FIG. 9 , the control rod drive mechanisms 40 overlap the control rod assemblies 27 in a plan view (however, in this state, the positions of the individual control rod drive mechanisms 40 and the control rod assemblies 27 are not yet aligned).

[0060] Next, in step S5, the operator rotates the upper core mechanism 30. The upper core mechanism 30 rotates on the small rotation plug 15. FIG. 11 is a diagram for explaining the movement of the control rod drive mechanism. As shown in FIG. 11, the control rod drive mechanism 40 rotates slightly counterclockwise around the third rotation axis Xc as the upper core mechanism 30 rotates. Specifically, in step S5, the upper core mechanism 30 is rotated so that the multiple control rod drive mechanisms 40-1 to 40-4 are positioned above the corresponding control rod assemblies 27-1 to 27-4 (so that the control rod drive mechanisms overlap the control rod assemblies in a plan view).

[0061] For example, the rotation of the upper core mechanism 30 is stopped when each of the control rod drive mechanisms 40 has moved to a position above each of the control rod assemblies 27-1 to 27-4. As described above, the rotation of the upper core mechanism 30 may be performed manually by an operator or by using the driving force of a drive source such as a motor. In the latter case, the upper core mechanism 30 may be rotated by a predetermined rotation amount by a rotation drive mechanism (not shown).

[0062] The rotation of the upper core mechanism 30 may be performed, for example, by capturing images of the control rod assemblies 27 with an imaging device, detecting predetermined reference positions of the control rod assemblies 27 in real time through image analysis based on the captured images, and continuing until the distance between the reference positions and the predetermined reference positions of the control rod drive mechanisms 40 becomes less than a threshold value.

[0063] By the above series of steps, even if the positions of the multiple control rod assemblies 27 are misaligned with respect to the multiple control rod drive mechanisms 40 as shown in FIG. 8( a), the multiple control rod drive mechanisms 40 can be positioned above the multiple control rod assemblies 27 by rotating the large rotation plug 14, the small rotation plug 15, and the upper core mechanism 30 of the fast reactor S100.

[0064] (Effects of the installation method of this embodiment) As described above, according to the installation method of this embodiment, even if the multiple control rod assemblies 27 of the core 20 are misaligned with the multiple control rod drive mechanisms 40 due to dimensional errors or assembly errors of components, the dimensional errors between the control rod drive mechanisms 40 and the control rod assemblies 27 can be reduced by rotating the large rotation plug 14, the small rotation plug 15, and the upper core mechanism 30.

[0065] The method of this embodiment is advantageous in that it does not require the provision of a new mechanism for adjusting the installation position of the control rod drive mechanism 40, since the control rod drive mechanism 40 is moved by utilizing the large rotation plug 14 and the small rotation plug 15, etc., which are conventionally provided in tank-type fast reactors.

[0066] The order in which the large rotary plug 14 and the small rotary plug 15 are rotated is arbitrary, but the procedure of rotating the large rotary plug 14 and then rotating the small rotary plug 15 has the following advantage: First, the large rotary plug 14 is rotated to bring the plurality of control rod drive mechanisms 40 closer to the plurality of control rod assemblies 27, and then the small rotary plug 15 is rotated to bring the plurality of control rod drive mechanisms 40 closer to the plurality of control rod assemblies 27 so as to finely adjust the positions of the control rod drive mechanisms 40, thereby enabling work to be carried out efficiently.

[0067] In the above embodiment, a predetermined reference position of the diagrid 18 is specified, but it is of course possible to specify the positions of one or more control rod assemblies 27. The large rotation plug 14, the small rotation plug 15, and the upper core mechanism 30 may be moved so that the corresponding control rod drive mechanisms 40 are positioned above the specified control rod assemblies 27.

[0068] (Adjusting the Position of a Member in the Vertical Direction) The present invention may include adjusting the position of a member in the vertical direction.

[0069] 12A and 12B are schematic diagrams showing a state in which the control rod drive mechanism 40 is slightly tilted with respect to the vertical direction and a state in which a shim member is arranged. As shown in Fig. 12A, when the control rod drive mechanism 40 is installed in the upper core mechanism 30, it is expected that the control rod drive mechanism 40 will be slightly tilted with respect to the vertical direction in the temporarily installed state due to dimensional errors and assembly errors of each member. In order to arrange the control rod drive mechanism 40 in an appropriate orientation, an installation method according to one embodiment of the present invention may include the following steps.

[0070] First, an operator temporarily installs the control rod drive mechanism 40 in the upper core mechanism 30 as shown in Figure 12(a) and measures the installation angle of the control rod drive mechanism 40 (first measurement step). The installation angle of the control rod drive mechanism 40 may be an angle relative to the horizontal direction or an angle relative to the vertical direction.

[0071] After the above-described measurement process is completed, the worker then places a shim member S-1 to adjust the angle of the control rod drive mechanism 40, as shown in FIG. 12( b). The shim member S-1 is a thin-plate spacer. Specifically, the worker places the shim member S-1 between a part of the components constituting the control rod drive mechanism 40 and a part of the upper core mechanism 30 so that the extension direction of the control rod drive mechanism 40 approaches the vertical direction (first placement process). The shim member S-1 may be interposed between a flange portion 40 a of a predetermined component of the control rod drive mechanism 40 and a part of the upper core mechanism 30. Thereafter, the flange portion 40 a is fastened to the upper core mechanism 30, for example, by bolting, thereby fixing the control rod drive mechanism 40 in a state in which its position has been adjusted.

[0072] According to this installation method, the orientation of the control rod drive mechanism 40 can be adjusted so that the extension direction of the control rod drive mechanism 40 approaches the vertical direction.

[0073] (Position Adjustment of Components in the Main Vessel) The position adjustment of components as described above may be performed, for example, when installing the diagrid 18. Figure 13 shows a state in which shim members are interposed in the diagrid. The worker first temporarily installs the diagrid 18 on the strongback 17 and measures the installation angle of the diagrid 18 (for example, the angle relative to the horizontal or vertical direction).

[0074] After completing the above measurement process, the worker then places the shim member S-2 to adjust the installation angle of the diagrid 18. Specifically, the worker places the shim member S-2 between a part of the components constituting the diagrid 18 and the upper surface of the strongback 17 so that the extension direction of the diagrid 18 approaches the vertical direction. This placement process is performed by placing the shim member S-2 so that the extension direction of the diagrid 18 approaches the vertical direction (second placement process). Thereafter, the diagrid 18 is fixed in place with its position adjusted, for example, by bolting. This installation method allows the orientation of the diagrid 18 to be adjusted so that the extension direction of the diagrid 18 approaches the vertical direction.

[0075] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments.

[0076] 10 Main vessel 10a Core barrel 11 Roof slab 12 Roof slab member 13 Rotating plug 14 Large rotating plug 15 Small rotating plug 17 Strongback 18 Diagrid 19 Partition plate 20 Core 25 Fuel assembly 27 Control rod assembly 27a Control rod 27b Guide tube 30 Upper core mechanism 40 Control rod drive mechanism 40a Flange portion 43 Control rod drive shaft guide tube 45 Control rod drive shaft 50 Intermediate heat exchanger 51 Inlet window 52 Exit window 60 Circulation pump 61 Piping S-1 Shim member S-2 Shim member S100 Fast reactor Xa First rotating shaft Xb Second rotating shaft Xc Third rotating shaft

Claims

1. A method for installing a reactor structure of a fast reactor, comprising: a large rotation plug configured to be rotatable about a first rotation axis in a vertical direction on a roof slab; a small rotation plug configured to be rotatable relative to the large rotation plug about a second rotation axis offset from the first rotation axis; an upper core mechanism configured to be rotatable relative to the small rotation plug and provided with a plurality of control rod drive mechanisms; a strongback located near the bottom of the main vessel; and a plurality of control rod assemblies arranged among a group of core components inserted into a diagrid located above the strongback, wherein the plurality of control rod drive mechanisms are arranged in a position corresponding to the plurality of control rod assemblies and move the control rods of the control rod assemblies up and down individually, and the method for installing a reactor structure of a fast reactor, comprising an adjustment step of rotating the large rotation plug, the small rotation plug, and the upper core mechanism to move the control rod drive mechanisms so that each control rod drive mechanism is positioned above the control rod assembly corresponding to the control rod drive mechanism.

2. The method for installing a reactor structure of a fast reactor according to claim 1, wherein the adjustment step includes rotating the large rotation plug, then rotating the small rotation plug, and then rotating the upper core mechanism.

3. The method for installing a reactor structure of a fast reactor according to claim 2, wherein the fast reactor has a diagrid placed on top of the strongback, and the adjustment step includes rotating the large rotation plug and then rotating the small rotation plug so that the distance between the center of the diagrid and the center of the upper core mechanism in a plan view becomes shorter.

4. A method for installing a reactor structure of a fast reactor as described in claim 1 or 2, wherein the adjustment step includes rotating the upper core mechanism so that each of the plurality of control rod drive mechanisms is positioned above the plurality of control rod assemblies corresponding to each control rod drive mechanism.

5. The method for installing a reactor structure of a fast reactor according to claim 1 or 2, wherein the control rod drive mechanism has a control rod drive shaft guide tube and a control rod drive shaft that moves up and down inside the control rod drive shaft guide tube, and further comprises: a first measurement step of temporarily installing the control rod drive mechanism and measuring the installation angle of the control rod drive shaft guide tube; and a first adjustment step of placing a first shim member between a component constituting the control rod drive mechanism and a part of the upper core mechanism and adjusting the installation angle of the control rod drive shaft guide tube so that the extension direction of the control rod drive shaft guide tube approaches the vertical direction.

6. A method for installing a reactor structure of a fast reactor as described in claim 1 or 2, further comprising: a second measurement step of temporarily installing the diagrid and measuring the installation angle of the diagrid; and a second adjustment step of placing a second shim member between the diagrid and the strongback and adjusting the installation angle of the diagrid so that the extension direction of the diagrid approaches the vertical direction.

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