JPH0136080B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nuclear reactor in which a cooling water circulation pump is built into a reactor pressure vessel.

[Conventional technology]

Boiling water reactors are usually equipped with a circulation system for forced circulation of cooling water within the reactor. Conventionally, this forced circulation system installed a pump outside the reactor pressure vessel to temporarily take out the cooling water inside the reactor outside the reactor, pump it up, and then return it into the reactor. However, in such reactors, the external circulation piping must be maintained and inspected according to standards similar to those for reactor pressure vessels, and there is a risk that workers may be exposed to some form of radiation during maintenance inspections. It was hot. Furthermore, the external circulating water outlet nozzle installed at the bottom of the reactor core is a large-diameter nozzle, and a large-capacity emergency core cooling system was required in case this system were to break. In addition, the external circulation piping and pump occupy a considerable amount of space, which necessitates making the containment vessel large. Furthermore, in order to force the cooling water to circulate, two large-capacity, high-head pumps are usually required, and the in-house power consumption to drive these pumps is approximately 1% of the plant output, so this power consumption can be reduced. It was hoped that this would be reduced.

Due to the above circumstances, a nuclear reactor with a built-in circulation pump has appeared in which a forced circulation device is provided inside the reactor pressure vessel. This reactor is as shown in USP 3,723,247.

[Problem that the invention seeks to solve]

In conventional nuclear reactors with built-in circulation pumps, the configuration for obtaining steam pressure output has been established, but consideration must be given to establishing safety and reliability by improving cooling characteristics.

An object of the present invention is to provide a nuclear reactor that is safer and more reliable than ever before.

[Means for solving problems]

The present invention includes a reactor core, a shroud head located above the reactor core, a lower plenum located below the reactor core, and a downcomer disposed around the outer periphery of the reactor core and the lower plenum. , a pump provided at a lower part of the downcomer and discharging cooling water in the downcomer into the lower plenum; and an air-water separation device communicated with the shroud head and located above the shroud head; In a nuclear reactor, the nuclear reactor has a main steam nozzle for discharging dry steam separated by the steam/water separator to the outside of the pressure vessel in the body of the reactor, and a support provided between the pressure vessel and the pedestal. A cooling water inlet nozzle and an outlet nozzle are provided in the body of the vessel during reactor shutdown,
The nuclear reactor with a built-in reactor cooling water circulation pump is characterized in that the opening position of the inlet nozzle into the downcomer is disposed at a lower position than the opening position of the outlet nozzle into the body.

[Effect]

In a nuclear reactor configured as described above, cooling water is injected into the downcomer from the inlet nozzle in order to remove decay heat after the reactor is shut down. The injected cooling water descends through the downcomer and enters the core, and after the core has cooled, it exits from the outlet nozzle, but since the outlet nozzle is located above the inlet nozzle, the injected cooling water flows directly from the inlet nozzle to the exit. Most of the injected cooling water is efficiently used for core cooling because it does not escape as if shot through the nozzle.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows a longitudinal sectional view of a nuclear reactor with a built-in reactor cooling water circulation pump according to the present invention. In the figure, the nuclear reactor is shown as reactor pressure vessel 1, which is the outer shell of the nuclear reactor.
and shroud head 2, which partitions the reactor core.
A reactor cooling water circulation pump 3 is provided in a space defined by the pressure vessel 1 and the shroud 2, that is, in the downcomer section A. It is already well known that the circulation pump 3 forces the cooling water in the furnace to circulate.

The cooling water inside the reactor pressure vessel 1 is circulated from the downcomer part A to the lower plenum B by the pump 3.
It enters the core C from the lower plenum B, is heated, passes through the shroud head 27, then passes through the steam-water separator 51, where it is separated into steam and liquid, and the steam passes through the dryer 52. It becomes dry steam and is sent from the main steam nozzle 13 to the turbine through the main steam pipe connected to the main steam nozzle 13. Then, the liquid portion separated by the dryer 52 or the steam/water separator is injected into the downcomer section A and recirculated.

In this nuclear reactor, the pressure vessel 1 has the following structure. That is, the pressure vessel 1 consists of a body 5, a lower mirror 6, and an upper mirror 7, and the pressure vessel body 5 has an emergency core cooling water nozzle 8, a reactor shutdown cooling water outlet nozzle 9, and an inlet. nozzle 10,
A water level instrumentation nozzle 11 and a water supply nozzle 12 are attached. Here, the reactor shutdown cooling water outlet nozzle 9 and the same inlet nozzle 10 are provided as inlet/outlet nozzles of the residual heat removal system, and in a conventional external recirculation type reactor, the outer recirculation piping However, in the present invention, since there is no external recirculation piping, nozzles 9 and 10 are provided directly in the pressure vessel 1 to connect it to the inside of the furnace. However, in the pressure vessel body 5 above the shroud 2, there are installed a main steam nozzle 13 with an inner surface tape, a water supply nozzle 12, and an emergency core cooling water nozzle to reduce the amount of steam released even if the main steam pipe is destroyed. There are 8 class nozzles, outlet and inlet nozzles 9 and 1.
0 must be placed in very limited positions.
Therefore, in the present invention, as shown in FIG. do. When removing residual heat, the reactor water in the pressure vessel 1 is first drawn out from the outlet nozzle 9, cooled by a heat exchanger (not shown), and then returned to the inlet nozzle 10 as cooling water. Cooling water entering from the inlet nozzle 10 flows downward through the downcomer section A, and then passes through the circulation pump 3 and ascends within the shroud 2 to cool the reactor core. In this way, the inlet nozzle 10 is connected to the outlet nozzle 9.
By arranging it below the inlet nozzle, the cold cooling water can flow downward, so even if the outlet and inlet nozzles 9 and 10 are arranged close to each other in the circumferential direction, the cooling water entering from the inlet nozzle 10 There is no risk of a short-circuit phenomenon in which the system is immediately pulled out from the adjacent outlet nozzle 9, and efficient cooling is possible.

On the other hand, the circulation pump 3 is placed at the lower part of the downcomer section A as described above. FIG. 3 is a detailed view of the attachment part of the circulation pump 3. The circulation pump 3 is composed of an impeller 13, a motor 14 for driving the impeller 13, and a diff user 15 surrounding the impeller 13. A large number of diff users 15 pass through a partition plate 16 provided in the downcomer section A. Therefore, when the impeller 13 is driven by the motor 14, the cooling water in the downcomer section A is forcibly passed through the shroud support leg 17, sent to the plenum section B at the bottom of the core, and further rises to the core section C. enter,
Cool the reactor core C. Knowing this forced circulation flow rate, that is, the core flow rate, is extremely important in controlling the operation of a nuclear reactor. Therefore, the differential pressure between the downcomer section A and the lower plenum section B, and between the lower plenum section B and the reactor core section C is measured. In order to measure this differential pressure,
A differential pressure instrumentation pipe 18 is installed at the entrance and exit of the differential user 15,
19 are provided. The amount of cooling water passing through each circulation pump can be measured from the differential pressure ΔP determined by the differential pressure instrumentation pipes 18 and 19 and the pump characteristic curve determined separately. 4 and 5 show differential pressure instrumentation between the core C and the lower plenum B. One end of the differential pressure instrumentation tube 20 is located above the fuel support 22 supported by the control rod guide tube 21, and the other end passes through the core support 23 and is drawn out to the bottom. As a result, it is possible to measure the differential pressure between the inside and outside of the fuel orifice 24 provided in the fuel support 22, that is, between the core C and the lower plenum B, and thereby the average core flow rate can be determined.

In FIG. 1, the emergency core spray 25 is
It is fixed to the shroud head 27 by the spray support 26 and connected to the bent core core pipe 29 (water supply piping) which is separably connected to the emergency core cooling water nozzle 8 by the slip joint 28. FIG. 6 is a single item diagram of the emergency core spray, in which two pairs of annular distribution pipes 30 are connected to branch pipes 31 and 31, respectively.
branches, and a spray nozzle 32 is attached to the branch pipe 31.
are installed in a grid pattern facing downwards. With this device, emergency core cooling water is sprayed onto the core fuel assemblies from directly above, so the cooling water is evenly distributed over each fuel assembly, increasing the core cooling effect. 29 is separated at the slip joint 28 and removed together with the shroud head 27 and the emergency core spray 25. Therefore, the emergency spray does not interfere with fuel exchange.

In addition to the above-mentioned emergency core spray system 25, cooling water injection from the above-mentioned reactor shutdown cooling water inlet nozzle 10 is used for emergency core cooling of this nuclear reactor. Since the nuclear reactor according to the present invention has no external circulation piping, and therefore there is no possibility of a rupture accident, the possibility that a large amount of primary cooling water will be lost and the reactor core will be exposed is extremely small. method becomes effective.

FIG. 7 shows another embodiment of the emergency core spray in the nuclear reactor according to the present invention. This emergency core spray structure is characterized in that the spray ring 33 is arranged in a circular manner in the shroud head 27, and the distribution pipe 34 is arranged outside the shroud head 27, thereby reducing the flow resistance in this part during operation.

The above configuration eliminates rupture accidents of external circulating water waste pipes, provides an emergency core spray with a higher core cooling effect, and also cools the core from the bottom with a separate system from the core spray as an emergency core cooling system. Therefore, the reliability of the emergency core cooling system can be increased and the safety of the nuclear reactor can be improved.

The nuclear reactor configured as described above is placed on the reactor pressure vessel pedestal 35, and the pressure vessel 1 is surrounded by a biological shield 36. FIG. 8 is a detailed view of the installation part. At the bottom of the pressure vessel there is an annular two-stage support 37, which is fixed on the pedestal 35. In this reactor,
Since the circulation pump 3 is located near the outer periphery of the pressure vessel 1, the support 37 has a structure that projects outward from the support 37, and is provided in an annular groove 38 provided in the pedestal 35. The first stage support 39 is welded to the pressure vessel lower mirror 6, and its outermost diameter can be made slightly smaller than the inner diameter of the pedestal 35. The second stage support 40 is coupled to the first stage support 39 by bolts 41. At the time of reactor construction, the second stage support 40 was constructed simultaneously with the construction of the pedestal 35 and biological shielding wall 36.
By installing this, it is possible to suspend the pressure vessel after constructing the biological shielding wall 36.

As for the emergency core spray, another modification may be as shown in FIG. 9. The upper structure of the shroud head 27 has a hollow double structure, and a water supply pipe 29 is installed in communication with the hollow inside. Then, on the inner surface side, spray nozzles 32 are installed in communication with the hollow interior, with spray nozzles 32 facing downward and being approximately evenly distributed. At this time, the water inlet 50 is left open to drain water. In this example, the structure is small and simple.

The above embodiment has the following effects.

(1) The reactor shutdown cooling water inlet nozzle of the residual heat removal system was placed lower than the outlet nozzle. The residual heat removal system removes decay heat during reactor shutdown by drawing cooling water out of the reactor from the outlet nozzle, cooling it with a heat exchanger, and then returning the cooling water back into the reactor through the inlet nozzle. However, by configuring as described above, it becomes possible to effectively cool the nuclear reactor.

(2) Pressure measuring instruments are placed in each room of the reactor downcomer, lower plenum, and core, and by measuring the differential pressure in each of these rooms, it is possible to measure the core flow rate.

(3) The emergency core spray is attached to the shroud head so that it can be removed as a unit with the shroud head. Not only is it possible to inject cooling water from directly above the fuel assembly using the emergency core spray, but it also has the effect of not interfering with operations such as fuel exchange.

(4) The first stage support, which is the reactor pressure vessel support welded to the reactor pressure vessel lower mirror, and this first stage support.
The second stage support is bolted to the stage support. This is because in the reactor of the present invention, the circulating water pump is installed in the lower mirror part, and this drive device is installed in the space below the lower mirror, so the reactor support has to be tilted. This was done taking into consideration that the reactor pressure vessel support diameter would be larger than the reactor main body diameter, and by creating a splittable two-stage support, the upper space (slightly larger than the reactor main body diameter) after the biological shield was completed was created. It is possible to suspend the pressure vessel using the

〔Effect of the invention〕

As described above, according to the present invention, when a nuclear reactor is shut down, cooling water is introduced into the pressure vessel through the inlet nozzle and discharged from the outlet nozzle, and at that time, both inlet and outlet nozzles are arranged such that the outlet nozzle is at a high place and the inlet nozzle is at a high place. By arranging the reactor at a lower location than the nozzle, the cooling water between the inlet and outlet nozzles improves cooling efficiency without causing a system short circuit, and it is possible to provide a nuclear reactor with a built-in circulation pump that can improve safety and reliability.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a nuclear reactor with a built-in reactor cooling water circulation pump according to the present invention, FIG. 2 is a cross-sectional view of FIG. 1 showing the circumferential direction of the nozzle, and FIG. A detailed view of the circulation pump attachment part, FIGS. 4 and 5 are explanatory views of the core flow rate instrumentation of the fuel support part in the core of FIG. 1, and FIG. 6 is a perspective view showing the shape of the core spray of FIG. 1, Figure 7 is a cross-sectional view of the core spray, which is an improvement on the core spray in Figure 6.
FIG. 8 is a detailed cross-sectional view of the reactor pressure vessel support portion shown in FIG. 1, and FIG. 9 is a longitudinal cross-sectional view showing a modification of the core spray shown in FIG. 1. A...Downcomer, B...Lower plenum, C...
...Reactor core, 1...Reactor pressure vessel, 2...Shroud, 3...Circulation pump, 9...Cooling water outlet nozzle at reactor shutdown, 10...Cooling water inlet nozzle at reactor shutdown, 13...Main Steam nozzle, 15... Diffusion user, 18, 19, 20... Differential pressure instrumentation pipe, 22
... Fuel support, 25 ... Emergency core spray, 26 ... Spray support, 27 ... Shroud head, 28 ... Slip joint, 29
...Curved furnace piping, 30...Circular distribution pipe, 31
... Branch pipe, 32 ... Spray nozzle, 33 ... Spray ring, 34 ... Distribution pipe, 35 ... Pedestal, 36 ... Living body shielding wall, 39 ... First stage support, 40 ... Second stage support , 41...Bolt.

Claims (1)

[Scope of Claims] 1 A reactor pressure vessel includes a reactor core, a shroud head located above the reactor core, a lower plenum located below the reactor core, and arranged around the outer periphery of the reactor core and the lower plenum. a downcomer, a pump provided at a lower part of the downcomer and discharging cooling water in the downcomer into the lower plenum, and an air-water separation device communicated with the shroud head and located above the shroud head, In the nuclear reactor, the reactor has a main steam nozzle in the body of the pressure vessel for discharging dry steam separated by the steam-water separator to the outside of the pressure vessel, and a support provided between the pressure vessel and the pedestal. A reactor shutdown cooling water inlet nozzle and an outlet nozzle are provided in the body of the reactor pressure vessel, and the opening position of the inlet nozzle into the downcomer is lower than the opening position of the outlet nozzle into the body. A nuclear reactor with a built-in reactor cooling water circulation pump, which is characterized by the fact that it is located in a central location. 2. The built-in reactor cooling water circulation pump according to claim 1, characterized in that pressure instrumentation pipes of a pressure detector are connected to both sides of the entrance/exit of the differential user of the pump and to the inside of the fuel support of the reactor core, respectively. type reactor. 3. In claim 1, the shroud head is provided with a plurality of spray nozzles arranged to overlap vertically with the reactor core, and each spray nozzle is provided with water supply piping fixed to the shroud head. A nuclear reactor with a built-in reactor cooling water circulation pump that is interconnected with 4. A nuclear reactor with a built-in reactor cooling water circulation pump according to claim 3, wherein the water supply piping is detachable in the middle outside the shroud head. 5. In claim 1, the support comprises a first stage support that is integrated with the pressure vessel and a second stage support that is connected to a lower part of the first stage support with bolts. A nuclear reactor with a built-in reactor cooling water circulation pump.