JPH0445078B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to the structure of a nuclear reactor.

In conventional pressurized water reactors, the reactor coolant is
After rising through the reactor core while being heated and passing through a number of holes in the upper core plate, the flow direction is changed laterally in an exit plenum defined by the core barrel, the upper support plate, and the upper core plate, and the control rods It flows towards the outlet nozzle through the wide gap between the guide tube and the upper core support column.

The control rod guide tube guides the control rod assembly vertically and protects the thin control elements from the flow of coolant radially outward or lateral to the reactor vessel, preventing long-term wear of the control elements. Preventing.

However, in a nuclear reactor where the number of control elements is extremely large and they are distributed throughout the reactor core, if the reactor superstructure is adopted as described above,
There is almost no clearance between adjacent control rod guide tubes, and the flow of coolant toward the exit nozzle is obstructed, making it difficult to obtain a sufficient flow rate of coolant. Furthermore, even if a sufficient flow rate can be obtained, the flow velocity will inevitably increase, and the fluid force acting on the guide tube will increase, leading to various problems.

The present invention has been made in view of the above-mentioned circumstances.

That is, the present invention provides a reactor vessel having an inlet nozzle and an outlet nozzle for coolant on its upper side, a lid detachably attached to the upper opening of the vessel, and a lid that is suspended and supported within the vessel. a core tank that cooperates with the vessel to form a descending annular space for the coolant; a lower core support plate supported at the bottom of the core tank and extending horizontally;
A plurality of fuel assemblies are loaded vertically on the lower core support plate and constitute the reactor core, a plurality of control rod drive devices are installed on the top of the lid, and each of the fuel assemblies has a single drive shaft. In a nuclear reactor having a plurality of control rod assemblies, the control element is inserted into a guide tube of the fuel assembly and moved, and the drive shaft is individually connected to the drive device, A plurality of guide tubes individually surrounding the control rod assembly, a plurality of protective hollow tubes individually surrounding only the drive shaft of the control rod assembly, and an intermediate support located between the protective hollow tubes and the guide tube. a calandria structure including a plate, a short sleeve located between a core plate located directly above the core and a lower end of the guide tube and individually surrounding the control elements; An upper reactor internal structure having an inner cylinder surrounding the cylinder and the calandria structure and forming an outlet annular flow path for the coolant between the core barrel and the inner cylinder is provided above the core, The upper end portion with holes, the plurality of protective hollow tubes, the upper support plate and the intermediate support plate located above and below the protective hollow tubes work together to divert the coolant to the main outlet. To provide a nuclear reactor structure in which a turning plenum is formed, and a small hole bored in the lower end of the inner cylinder forms a bypass flow path that communicates the outlet annular flow path with the inside of the calandria structure. It is. According to the present invention, the coolant flows along the longitudinal direction around the thin control element and does not cause a lateral flow, so the occurrence of fluid vibration in the control element is suppressed, and in the event of an accident, the coolant flows from the calandri structure to A bypass flow path toward the coolant outlet nozzle of the reactor vessel is formed, and a coolant circulation flow path is formed in cooperation with a coolant recirculation system outside the reactor vessel, thereby maintaining the reactor safely. Can be done.

The present invention will be explained below based on illustrated embodiments. In FIG. 1, a reactor core barrel 5 is suspended and supported in a reactor vessel 3 to which a lid 1 is removably attached. define. A core 9 made up of a large number of fuel assemblies 11 is supported on a lower core support plate 7 located below the core tank 5 . Although there are many fuel assemblies 11 forming the reactor core 9, only two are shown to avoid complicating the drawing.

The fuel assembly 11 is a conventional fuel assembly, in which a large number of fuel rods and control element guide tubes arranged in parallel are fixed in a bundle by an egg-frame-shaped support grid, and further has end plate nozzles at the top and bottom. be.

Above the core 9, an upper core plate 13 for positioning the fuel assemblies 11 extends horizontally, forming an in-core upper structure 15 as described later. The inner cylinder 17 of the in-reactor upper structure 15 has a lower end connected to the upper core plate 1.
3, and its upper end is joined to the upper support plate 19.

Between the upper support plate 19 and the upper core plate 13, an intermediate support plate, that is, a middle plate 21 is provided extending horizontally, and a plurality of control rod assemblies 23 (partially shown) are individually surrounded. A guide tube 25 is provided extending vertically. When the control elements of the control rod assembly 23 are lowered into the core 9, the guide tube 25
The drive shaft 27 of the control rod assembly 23 is located therein, and the control element is retracted into the guide tube 25 when the control rod assembly 23 is pulled up. Control rod assembly 23
The number corresponds to the number of guide tubes 25.

The control rod assembly 23 is made up of a spider (not shown) located at the lower end of the drive shaft 27 and a large number of thin rod-shaped control elements hanging in the shape of a bunch. The control element moves inside the guide tube. A plurality of drive devices 29 and 31 provided on the lid 1 are individually connected to one of the many control rod assemblies 23, and move them up and down during operation of the reactor to perform reactivity control and power control. .

A plurality of protective hollow tubes 33 whose upper and lower ends are connected to the middle plate 21 and the upper support plate 19
individually surrounds only the drive shaft 27.

A calandria structure 6 is provided at the lower end of the guide tube 25.
0 is fixed to the upper surface of the upper tube plate 61 of 0. The lower tubesheet 63 of the calandria structure 60 is located above the upper core plate 13, and both tubesheets 61, 63 are formed by a number of short hollow tubes 65 individually surrounding the control elements of the control rod assembly 23. are connected together.

FIG. 2 shows a plan cross section of the guide tube 25, which has a non-perforated can 41 with a substantially rectangular cross section and a guide plate 43 disposed at a proper position in the axial direction.

The control element is supported laterally through a small hole 45 in the guide plate 43, and the drive shaft 27 is supported through a large hole 4 in the center.
Pass through 7. A narrow passageway interconnecting a number of small holes 45 is traversed by a spider that connects the control elements together.

The coolant rises primarily between the can 41 and the guide plate 43 and flows out into a diverting plenum 49 formed on the outside of the hollow tube 33.

In the embodiment described above, the coolant flowing from the primary cooling system piping (not shown) through the inlet nozzle 35 of the vessel 3 flows downward in the annular channel 37 and reaches the lower plenum 39 .

The coolant whose flow direction has been reversed in the lower plenum 39 rises through flow holes (not shown) in the lower core support plate 7 and enters the core 9 .

In the core 9, the coolant flows through the fuel assemblies 11.
The fuel rises around the fuel rods, during which time it is heated by the heat of the nuclear reaction. Thereafter, it flows into and out of the hollow tube 65 of the calandria structure 60 through holes (not shown) in the upper core plate 13 and the lower tube sheet 63. Inside the hollow tube 65 the coolant flows along the longitudinal direction of the control element and outside the hollow tube 65 along this, flowing mainly into the guide tube 25 through the holes in the upper tube plate 61. .

A very small amount of coolant flows through the narrow gap between the guide tubes 25.

The main flow of the coolant that has flowed in the guide tube 25 in the axial direction along the drive shaft 27 of the control rod assembly 23 or the outer surface of the control element passes through the hole in the intermediate plate 21 and
Diverting plenum 4 between middle plate 21 and upper support plate 19
It flows out within 9.

In the diverting plenum 49, the coolant whose flow direction has been changed laterally flows through a plurality of holes 5 in the upper part of the inner cylinder 17.
1 to the outlet annular channel 67 on the outside of the inner cylinder 3, and further descends through the outlet nozzle 53 to the container 3.
and flows into the primary cooling system piping. These heated coolants return to the inlet nozzle 35 through a steam generator included in a typical primary cooling system.

Short hollow tube 6 of calandria structure 60
5 is in communication with the outlet annular flow path 67 through the small hole 55 below the inner cylinder 17, and a small portion of the coolant flows through the hole 55 and the outlet annular flow path 67 into the outlet. It flows to the nozzle 53 and the pressure loss is relatively small. Furthermore, if the primary cooling system piping or the like is damaged, the reactor core 9 is scrammed and the circulation pump is stopped.

Even after the core 9 is scrammed, the fuel assembly 11 generates decay heat, and the coolant heated by this changes its direction between the tube sheets 61 and 63 of the calandria structure 60, and flows through the small holes 55 and It exits the outlet nozzle 53 through an outlet annular channel 67 to a coolant recirculation system (not shown). The steam generator and coolant pump that constitute the coolant recirculation system of a pressurized water reactor have conventionally been installed in a positional relationship that allows natural circulation of the coolant.
The coolant flowing out from No. 3 is cooled by a steam generator and returned to the reactor vessel through natural circulation. This results in
The reactor core 9, which is scrammed and generates decay heat, can be efficiently cooled and a high level of safety can be ensured.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG.
The figure is a partial sectional view of FIG. 1. 1... Lid, 3... Container, 9... Core, 15...
Furnace upper structure.

Claims (1)

[Claims] 1. A reactor vessel having an inlet nozzle and an outlet nozzle for coolant on the upper side thereof, a lid detachably attached to the upper opening of the vessel, and a lid suspended within the vessel and cooperating with the vessel. a core tank forming a descending annular space for the coolant; a lower core support plate supported at the bottom of the core tank and extending horizontally; a core loaded vertically on the lower core support plate; a plurality of fuel assemblies, a plurality of control rod drive devices installed on the top of the lid, each of which has one drive shaft and a plurality of control elements, and the control elements guide the fuel assemblies. In a nuclear reactor having a plurality of control rod assemblies that are inserted into a tube and moved and the drive shafts are individually connected to the drive device, a plurality of guide cylinders that individually surround the control rod assemblies, and the control rods. A plurality of protective hollow tubes that individually surround only the drive shaft of the assembly, an intermediate support plate located between the protective hollow tubes and the guide tube, a core plate located directly above the reactor core, and the lower end of the guide tube. a calandria structure including a short sleeve located between and individually surrounding the control element; and a calandria structure depending within the core barrel and surrounding the guide tube and the calandria structure and extending between the core barrel and the calandria structure. An upper reactor internal structure having an inner cylinder forming a coolant outlet annular flow path is provided above the reactor core, an upper end portion of the inner cylinder having a plurality of holes formed therein, and the plurality of protective hollow tubes. , an upper support plate located above and below the protective hollow tube, and the intermediate support plate cooperate to form a main outlet flow diversion plenum for the coolant, and a small hole bored at the lower end of the inner tube is formed. A nuclear reactor structure characterized in that a hole forms a bypass passage connecting the outlet annular passage and the inside of the calandria structure.