JPH0160796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in pressurized water nuclear reactors.

To explain a conventional pressurized water reactor with reference to FIG. 1, 1 is a reactor vessel which has a coolant inlet nozzle 1a and an outlet nozzle 1b on the upper side, and 2 is a reactor vessel that is suspended and supported within the reactor vessel 1 and has a reactor core. The supporting core barrel 3 has a fuel assembly each having a plurality of fuel rods 3.
a, a plurality of control rod guide tubes 3b, and a support grid 3c for bundling and fixing each fuel rod 3a and each control rod guide tube 3b, and each of the fuel assemblies is arranged in a forest shape. These are multiple fuel assemblies that make up the core. The upper lid is detachably attached to the upper part of the reactor vessel 1, and a plurality of control rod drive devices are arranged in a forest shape on the upper surface, and the control rod guide tubes 3b of the fuel assembly 3 are inserted into and removed from the upper cover. A plurality of control rod assemblies are shown in which a plurality of control rods are attached to a spider in a cluster, and each control rod drive shaft extending upward from each spider is detachably attached to a control rod drive device of the upper cover. was omitted. Reference numeral 5 denotes an upper core having an upper core plate 5a that presses the upper end of each fuel assembly 3 constituting the core, and a plurality of control rod assembly guide tubes 5b arranged in a forest shape on the upper core plate 5a. The structure 6 consists of a large number of hollow tubes 6a through which control rod drive shafts of the control rod assembly pass individually, and upper and lower tube plates 6b and 6c connecting the upper and lower ends of each hollow tube 6a, and A calandria structure that is disposed above the core structure 5 and forms a coolant outlet diversion plenum, and the calandria structure 6 is directly attached to the control rod assembly guide tube 5b of the upper core structure 5. , the control rod drive shaft 4c of the control rod assembly is passed through the hollow tube 6a of the calandria structure 6 to prevent the control rod drive shaft 4c from being affected by the lateral flow of primary cooling water.

In the pressurized reactor, when replacing fuel, etc.,
When the calandria structure 6 is removed, the control rod drive shaft 4c in the standing state is slightly tilted and deflected. Therefore, when reinstalling the calandria structure 6, the center of each control rod drive shaft 4c and the center of each hollow tube 6a of the calandria structure 6 do not match, and all control rod drive shafts 4c are connected to all hollow tubes 6a. It was difficult to insert them at the same time. Furthermore, when the primary cooling water flows from the upper core structure 5 to the calandria structure 6, the flow direction changes rapidly between each hollow tube 6a toward the outlet nozzle 1b (horizontal direction), but the control rod assembly guide If the tube 5b is directly attached to the calandria structure 6, the above-mentioned lateral flow will be caused by the control rod assembly guide tube 5b.
The spider 4b located in the upper part is affected by the lateral flow in the upper part, and
There was a possibility of vibration.

The present invention addresses the above-mentioned problems, and consists of a reactor vessel having a coolant inlet nozzle and an outlet nozzle on the upper side, a reactor vessel that is suspended in the reactor vessel and supports the reactor core, and a fuel assembly. each of which consists of a plurality of fuel rods, a plurality of control rod guide tubes, and a support grid for bundling and fixing the fuel rods and control rod guide tubes, and each of the fuel assemblies is arranged in a forest shape. multiple fuel assemblies that make up the core,
an upper cover that is detachably attached to the upper part of the reactor vessel and has a plurality of control rod drive devices arranged in a forest on the upper surface; a plurality of control rods that are inserted into and removed from each control rod guide tube of the fuel assembly; a plurality of control rod assemblies, each of which comprises a plurality of control rod assemblies, each of which is attached to a spider in the form of a tuft, and in which each control rod drive shaft extending upward from each spider is detachably attached to a control rod drive device of the upper lid; An upper core structure having an upper core plate that presses the upper end of a fuel assembly and a plurality of control rod assembly guide tubes arranged in a forest on the upper core plate, and a control rod drive shaft of the control rod assembly. A calandria consisting of a number of hollow tubes through which the tubes individually pass, and upper and lower tube plates connecting the upper and lower ends of each hollow tube, and is disposed above the upper core structure to form a coolant outlet diversion plenum. a structure, and a plurality of drive shaft guide holes each having a guide conical surface opening downward, each drive shaft guide hole facing each hollow tube of the calandria structure directly below the calandria structure, and the calandria structure a guide structure for directing coolant through the lower tube plate of the reactor to the exit diverting plenum, the purpose of which is to The rod drive shaft can be smoothly inserted into all hollow tubes at the same time. Another object of the present invention is to provide an improved nuclear reactor that can prevent vibration of the spider of the control rod assembly as much as possible.

Next, the nuclear reactor of the present invention will be described with reference to an embodiment shown in FIGS. 2 to 14. 1 in FIG. 3 is a reactor core tank that is suspended in the reactor vessel 1 and supports the reactor core, and 3 is a fuel assembly that includes a plurality of fuel rods 3a, a plurality of control rod guide tubes 3b, each fuel rod 3a, and each control rod. It consists of a support grid 3c that bundles and fixes rod guide tubes 3b, and each of the fuel assemblies is arranged in a forest shape to constitute a reactor core.
Note that the upper cover, which is detachably attached to the upper part of the reactor vessel 1 and has a plurality of control rod drive devices arranged in a forest on the upper surface, is not shown. Also, 4 in Figure 3
A plurality of control rods 4a to be inserted into and removed from each control rod guide tube 3b of the fuel assembly 3 are attached to a spider 4b in a cluster, and each control rod drive shaft 4c extending upward from each spider 4b is connected to the control rod guide tube 3b of the fuel assembly 3. a plurality of control rod assemblies that are removably attached to the control rod drive device in the top lid;
5 in FIG. 2 denotes each fuel assembly 3 constituting the core.
The upper core plate 5a that presses the upper end of the upper core plate 5a and the upper core plate 5
6 in FIGS. 2 and 3 is an upper core structure having a plurality of control rod assembly guide tubes 5b arranged in a forest shape on the upper core structure. It consists of a large number of hollow tubes 6a that pass through it, and upper and lower tube plates 6b and 6c that connect the upper and lower ends of each hollow tube 6a, and is arranged above the core structure 5 to form a coolant outlet diversion plenum. The calandria structure 7 has a large number of drive shaft guide holes 7d, 7 each having a guide conical surface that opens downward.
e (or 7f), each drive shaft guide hole is opposite to each hollow tube 6a of the calandria structure 6 directly below, and the coolant is passed through the lower tube plate 6c of the calandria structure 6 to the outlet diverting plenum. It is a guide structure that guides people. The details of the calandria structure 6 are shown in FIGS. 3 to 7. In each figure, 6d is a cylindrical body, 6e
6f is a flange provided at the upper end of the body 6d, 6f is a number of passage holes provided in the lower tube plate 6c, 6g is an outlet opening provided in the body 6d, and 6h is a nut for mounting the guide structure 7. . Further, details of the guide structure 7 are shown in FIG. 3 and FIGS. 8 to 13.
In each figure, 7a is an upper passage plate, 7b is a lower passage plate, 7c is a lattice-like partition plate connecting the passage plates 7a and 7b, and 7d is the hollow tube 6a.
A large number of drive shaft guide holes, 7, are provided in the upper channel plate 7a directly below the hollow tubes 6a.
Numerous drive shaft guide holes e are provided in the lower channel plate 7b so as to be directly below and directly opposite each of the drive shaft guide holes 7d, and these drive shaft guide holes 7d and 7e are , has a guide conical surface that opens downward. Note that these drive shaft guide holes 7d, 7
e may be connected by a guide tube 7f having a conical guide surface facing downward. Further, 7g is a large number of channel holes provided in the upper channel plate 7a, 7h is a large number of channel holes provided in the lower channel plate 7b, and 7i is a partition plate 7.
7j is a positioning pin provided in the upper flow path plate 7a, and the positioning pin 7j is inserted into the pin hole (see 6i in FIG. 3) of the calandria structure 6. . Further, 7k is a bolt screwed into the nut 6h of the candoria structure 6;
1 is a pin hole provided in the lower channel plate 7b. Further, 5c in FIG. 3 is a flange fixed to the upper end of the control rod assembly guide cylinder 5b, and 5d is a positioning pin provided on the flange 5c, which is adapted to engage with the pin hole 7l. As is clear from the above description, in the nuclear reactor of the present invention (see FIG. 2), the core structure incorporated in the reactor vessel 1 is
It is composed of an upper core structure 5, a calandria structure 6, a guide structure 7, a control rod assembly guide tube 5b, etc., and a fuel assembly 3 is loaded in the lower part of the core barrel 2. Further, an upper core structure 5 is attached to the upper part of the fuel assembly 3, and a plurality of control rod assembly guide tubes 5 are installed in the upper core structure 5.
b is placed. Further, a calandria structure 6 having a guide structure 7 attached to the bottom thereof via a bolt is installed on each control rod assembly guide tube 5b. In addition, the calandria structure 6 is the fifth to seventh
As shown in the figure, in order to protect the control rod drive shaft 4c from the fluid load due to the lateral flow of primary cooling water, an upper tube plate 6b and a lower tube plate 6c supporting each hollow tube 6a and both ends thereof, and a body 6d are provided. can be,
There is a flange 6e on the upper edge of the body 6d. Further, the lower tube plate 6c is provided with a large number of flow passage holes 6f so that the primary cooling water discharged from the guide structure 7 flows into the calandria structure 6, and the outlet nozzle 1b on the reactor vessel 1 side of the fuselage 6d An opening 6g on the calandria side is provided at the opposing position. Further, nuts 6 for guide structure mounting bolts are provided on the lower tube plate 6c.
h is attached at multiple locations. Further, the same number of hollow tubes 6a as the control rod drive shafts 4c have inner diameters larger than the outer diameters of the control rod drive shafts 4c, and both ends are fixed to the upper tube plate 6b and the lower tube plate 6c by welding or screwing. Further, the guide structure 7 is the eighth
As shown in Figures 1 to 12, it is composed of an upper passage plate 7a, a lower passage plate 7b, a lattice-shaped partition plate 7c, a guide tube 7f, a positioning pin 7j, and the like. The upper channel plate 7a is provided with a channel hole 7g as shown in FIGS. 10 and 11, and the portion through which the control rod drive shaft 4c passes is provided with a drive shaft guide hole 7d and a drive shaft guide tube mounting hole. 7m is provided. The mounting bolt 7k is for fixing the guide structure 7 to the calandria structure 6, and the positioning pin 7j is for aligning the center of the hollow tube 6a with the center of the drive shaft guide hole 7d. Further, the lower flow passage plate 7b is also provided with flow passage holes 7h. Also, the upper channel plate 7a
and a drive shaft guide hole 7 provided in the lower channel plate 7b.
d and 7e have guide conical surfaces that open downward, as shown in FIG. 13, to facilitate guiding the tip of the control rod drive shaft. Drive shaft guide hole 7
The average inner diameter D ₁ of e is larger than the average inner diameter D ₂ of the drive shaft guide hole 7d. Therefore, once the tip of the control rod drive shaft 4c enters the lower guide hole 7e and is guided, as the drive shaft 4c moves upward, the tip approaches the center line of the guide hole, and the tip of the drive shaft 4c moves upward. The tip is designed to smoothly enter the upper guide hole 7d.

Next, the operation of the nuclear reactor will be explained. The primary cooling water that has risen within the control rod assembly guide tube 5b is once collected within the guide structure 7, and then flows into the calandria structure 6. At this time, within the calandria structure 6, the direction of flow suddenly increases in the direction of the outlet nozzle 1b of the reactor vessel 1 (horizontal direction) between the hollow tube 6a, but 5b, there is a guide structure 7 with a rectifying effect, which prevents the influence of the cross flow in the calandria structure 6 from being transmitted to the upper part of the control rod assembly guide tube 5b, and prevents the spider located in the upper part of the control rod assembly guide tube 5b 4b does not vibrate. Also, the control rod assembly guide tube 5b
is not affected by cross flow, so positioning pin 5
The lateral load applied to d is reduced.

When exchanging fuel, etc., the upper cover of the reactor vessel 1 is removed, and then the control rod assembly 4 upper core structure 5 calandria structure 6 guide structure 7 etc. are removed using a lifting rig 8 as shown in FIG. Placed on the upper core structure storage stand 10 in the cavity 9,
Next, as shown in FIG. 16, the calandria structure 6 and the guide structure 7 are removed by the lifting rig 8, and then the control rod assembly 4 is removed as shown in FIG. FIG. 18 shows the control rod assembly 4 completely removed. After the fuel exchange is completed, the control rod assembly 4 is inserted and stood up as shown in FIG. 19. At this time, the upper end side of the control rod drive shaft 4c of each control rod assembly 4 is not supported, and the control rod drive shaft 4c is slightly tilted and bent. Then the second
As shown in Figure 21, the calandria structure 6 and guide structure 7 are transferred above the upper core structure 5 by the lifting rig 8, and then the outer part of the lifting rig 8 is lowered as shown in Figure 21. Then, the lower end of the lifting rig is positioned and fixed on the flange of the upper core structure 5, and then the inner part of the lifting rig 8 is lowered as shown in FIG. 7e, 7d
(Guide hole with a guide conical surface that opens downward)
guides each control rod drive shaft 4c close to the center of each hollow tube 6a of the calandria structure 6, and guides the tip of each control rod drive shaft 4c to each hollow tube 6a of the calandria structure 6. Second
FIG. 3 shows a state in which the positioning pin 5d on the control rod assembly 5 side is engaged with the pin hole 7l of the guide structure 7, and the assembly is completed.

The nuclear reactor of the present invention is configured as described above, and when the calandria structure 6 and the guide structure 7 descend toward each of the control rod drive shafts 4c, the drive shaft guide holes 7e of the guide structure 7 , 7d (guide holes with downwardly open guide conical surfaces) guide each control rod drive shaft 4c so as to approach the center of each hollow tube 6a of the calandria structure 6, and each control rod drive shaft 4c Since the tips of the rods are guided to each hollow tube 6a of the calandria structure 6, when installing the calandria structure 7, all the control rod drive shafts 4c can be smoothly inserted into all the hollow tubes 6a at the same time. Furthermore, when the primary cooling water flows into the calandria structure 6, the flow direction suddenly changes between the hollow tubes 6a toward the outlet nozzle 1b of the reactor vessel 1 (horizontal direction). There is a guide structure 7 with a rectifying effect between the calandria structure 6 and the control rod assembly guide tube 5b, so that the influence of the lateral flow within the calandria structure 6 is transferred to the control rod assembly guide tube 5b.
The vibration is not transmitted to the upper part of the spider 4b, and the spider 4b located in the upper part does not vibrate. Furthermore, since the control rod assembly guide tube 5b is not affected by lateral flow, there is an effect that the lateral load applied to the positioning pin 5d can be reduced.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to such embodiments, and that various design modifications can be made without departing from the spirit of the present invention. .

[Brief explanation of drawings]

Figure 1 is a longitudinal side view of a conventional nuclear reactor;
The figure is a vertical side view showing an embodiment of the nuclear reactor according to the present invention, and FIG. 3 is a partially cutaway perspective view showing the main parts thereof.
Figure 4 is a longitudinal side view of the calandria structure, Figure 5
The figure is a cross-sectional plan view along the line V-V in Figure 4, Figure 6 is an enlarged plan view of the arrowed part in Figure 5, Figure 7 is an enlarged vertical sectional side view of the arrowed part in Figure 4, and Figure 8 is the guide structure. A partially cutaway plan view of the object, FIG. 9 is a longitudinal side view thereof,
Fig. 10 is an enlarged vertical sectional side view of the arrow X portion in Fig. 9;
Figure 11 is a plan view taken along the arrow XI-XI line in Figure 10;
12 is a cross-sectional plan view taken along the arrow XII-XII line in FIG.
5 to 23 are action explanatory diagrams. 1... Reactor vessel, 1a... Inlet nozzle, 1b
... Outlet nozzle, 2 ... Core barrel, 3 ... Fuel assembly, 3a ... Fuel rod, 3b ... Control rod guide tube, 4
...Control rod assembly, 4a...Control rod, 4b...Spider, 4c...Control rod drive shaft, 5...Upper core structure, 5a...Upper core plate, 5b...Control rod assembly guide tube , 6... Calandria structure, 6a...
...Hollow tube, 6a... Upper tube sheet, 6b... Lower tube sheet, 7... Guide structure, 7d, 7e or 7
f...Drive shaft guide hole.

Claims (1)

[Claims] 1. A reactor vessel having coolant inlet and outlet nozzles on the upper side, a core tank that is suspended in the reactor vessel and supports the reactor core, and a fuel assembly each having a plurality of fuel rods and a plurality of control rods. a plurality of fuel assemblies comprising a guide tube and a support grid for bundling and fixing the fuel rods and the control rod guide tubes, and each of the fuel assemblies is arranged in a forest shape to constitute a reactor core; an upper cover that is detachably attached to the upper part of the reactor vessel and has a plurality of control rod drive devices arranged in a forest on the upper surface; a plurality of control rods that are inserted into and removed from each control rod guide tube of the fuel assembly; a plurality of control rod assemblies, each of which comprises a plurality of control rod assemblies, each of which is attached to a spider in the form of a tuft, and in which each control rod drive shaft extending upward from each spider is detachably attached to a control rod drive device of the upper lid; an upper core structure having an upper core plate that presses the upper end of a fuel assembly; and a plurality of control rod assembly guide tubes arranged in a forest on the upper core plate;
The control rod assembly includes a plurality of hollow tubes through which the control rod drive shafts of the control rod assembly pass individually, and upper and lower tube plates connecting the upper and lower ends of each hollow tube, and is disposed above the upper core structure. a calandria structure forming a coolant outlet diverting plenum, and a plurality of drive shaft guide holes having downwardly open guide conical surfaces, each drive shaft guide hole being connected to each hollow tube of the calandria structure. a guide structure directly below and opposing the guide structure for directing coolant to the outlet diverting plenum through the lower tube plate of the calandria structure.