JPH04289492A - Pressure rise suppression device for reactor container - Google Patents

Abstract

PURPOSE:To provide a device for suppressing pressure rise in a containment which does not require exterior emergency electric power source in case of a loss-of-primary-coolant accident in a nuclear reactor facility and the like. CONSTITUTION:To a primary coolant pipe 2, a pipe 3 from a gravity injection tank 10 placed at higher elevation than a reactor vessel 1 is connected putting an isolation valve 5 and a check valve 7 on the line. Also, a pipe 4 from an accumulator tank 9 is connected to the reactor vessel wall at a downcomer part 11 in the reactor vessel 1 putting an isolation valve 6 and a check valve 8 on the line.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor containment vessel pressure rise suppressing device for suppressing an increase in internal pressure of a containment vessel in the event of a primary coolant loss accident in a nuclear reactor facility or the like.

0002

[Prior Art] In conventional plants, spray equipment is installed inside the reactor containment vessel in order to suppress the rise in pressure inside the containment vessel due to steam released into the reactor containment vessel in the event of a primary system piping rupture accident, etc. is installed.

An example of a conventional containment vessel pressure rise suppression system is shown in FIG. Spray water is pumped out from a spray water source 11 by a spray pump 12, and the spray water cooled by a spray cooler 13 is sprayed from a spray ring header in a containment vessel.

LOCA of a plant equipped with the equipment shown in Figure 4
(Loss of Coolant Accident
Figure 5 shows the change in internal pressure inside the containment vessel at time t). In the initial stage, the primary coolant is released into the reactor containment vessel 10 in a short time, so that the containment vessel pressure increases rapidly. By ensuring an appropriate space volume within the reactor containment vessel 10, the pressure increase at this stage is suppressed. Thereafter, the steam generated during the re-submergence of the reactor core is released from the rupture, and the pressure in the reactor containment vessel rises again. If left as it is, the pressure in the reactor containment vessel will continue to rise, so spraying from the spray equipment shown in Figure 4 is started to reduce the pressure inside the containment vessel.

[0005]

As mentioned above, the conventional method requires related equipment such as spray equipment and emergency power supply equipment as shown in FIG. Since a pump is installed, the system will not start unless power is supplied from outside. Furthermore, if the spray system malfunctions, the inside of the containment vessel will be flooded with water, forcing the plant to be shut down for a long period of time.

In order to solve the above problems, in the present invention, in the event of a primary system piping rupture accident, the rupture port is submerged in water at an early stage, the steam flowing out from the rupture port is absorbed in the submerged water, and the steam inside the containment vessel is absorbed. It is an object of the present invention to provide a containment vessel pressure rise suppressing device that makes it possible to prevent direct release into the containment vessel, thereby eliminating the need for conventional spray equipment inside the containment vessel.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention configures a primary coolant circulation system consisting of a reactor vessel, a steam generator, and a primary coolant pump, and Connect the piping from the gravity injection tank located higher than the reactor vessel to the piping via an isolation valve and check valve, and connect the piping from the pressure accumulation tank to the other isolation valve and check valve. downcomer of the reactor vessel through
It is connected to the wall of the reactor vessel.

[0008]

[Operation] FIG. 5 shows the pressure variation characteristics in the containment vessel when the containment vessel pressure increase suppression system according to the present invention is installed. In addition, the solid line in FIG. 5 shows an example of a conventional system.

[0009] In the initial stage, the primary coolant is released into the containment vessel for a short time, so that the containment vessel pressure increases rapidly. The pressure increase at this stage can be suppressed by ensuring an appropriate space volume within the containment vessel. When the core is re-flooded, steam is released again from the rupture port and the pressure in the containment vessel increases, but once the core is re-flooded, the increase in internal pressure stops (the pressure at this time is called the re-flood peak pressure). , and then gradually decreases. If we assume that all of the decay heat in the reactor core becomes steam and is released from the rupture port, the pressure in the containment vessel will continue to rise again, but in the containment vessel pressure suppression system according to the present invention, the pressure in the containment vessel will continue to rise until re-flooding. - By submerging the rupture port in water before the pressure exceeds the maximum pressure, the release of steam into the containment vessel is stopped, so the pressure in the containment vessel drops as shown by the broken line in the figure. The cause of the drop in containment vessel pressure is that steam release from the rupture port stops and heat is absorbed by the structural materials inside the containment vessel.

[0010] In the present invention, although there is a slight time delay in the pressure drop inside the reactor containment vessel compared to the conventional system, when viewed as a whole, there is no significant difference in pressure suppression effect.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a containment vessel pressure rise suppression system according to the present invention.

A method for preventing the steam generated in the core from continuing to be released from the rupture port into the containment vessel during a large rupture LOCA will be explained below with reference to FIG.

The present invention provides a primary coolant loop (reactor vessel 1→steam generator (SG)→primary coolant pump 20→reactor vessel 1) in a pressurized water reactor. The isolation valve 5 connects the piping 3 from the gravity injection tank 10 located higher than the reactor vessel 1 to the primary coolant piping 2 of the circulation system).
and a check valve 7, and the pipe 4 from the pressure accumulation tank 9 is connected to the reactor vessel 1 through an isolation valve 6 and a check valve 8.
The downcomer section 11 is connected to the wall of the reactor vessel.

Note that the isolation valves 5 and 6 are normally operated in an open state. In addition, a plurality of check valves 7 and 8 (two in the figure) are arranged in one piping system, but this is for backup purposes.

The pressure accumulator tank 9 is filled with emergency cooling water, and the upper gas phase is filled with pressurized N2 gas at 50 kg/cm2.

[0016] In addition, the gravity injection tank 10 has a water height of 10 m.
of cooling water is stored and the injection water pressure is 1Kg/cm.
2 is obtained.

During normal operation, the pressure inside the reactor vessel 1 is approximately 1
60 kg/cm2, but since the check valve 7 or the check valve 8 is arranged, backflow of the primary coolant to the gravity injection tank 10 or the pressure accumulation tank 9 is prevented.

[0018] Primary coolant pipe rupture accident (i.e., LOCA
) Sometimes, the pressure inside the reactor vessel 1 drops suddenly, and when the pressure drops below 50 kg/cm2, emergency cooling is automatically sent from the pressure storage tank 9 to the downcomer section 11 inside the reactor vessel 1 due to the pressure difference. Water is injected. After this, when the pressure further decreases and the pressure within the primary coolant circulation system (i.e., the primary coolant loop) becomes 1 Kg/cm2 or less, the gravity injection tank 10 is automatically The cooling water inside is supplied to the primary coolant pipe 2.

In FIG. 2, 1B and 12B are units indicating the size of the piping. ■In the event of a rupture in the primary coolant pipe at any location, place a water storage tank (gravity injection tank) with enough water to submerge the rupture in a location sufficiently higher than the primary cooling system. installed to enable the supply of submerged water by gravity without the need for an external emergency power source. ■The rupture port must be able to be submerged quickly after the core is re-flooded, so that the pressure rise in the containment vessel can be kept within the permissible range. ■
The hot water that flows into the submerged water from the fracture port on the reactor exit side increases the temperature of the submerged water, but this submerged water flows in from the fracture port on the SG side and is cooled by the SG (Figure 3). When the temperature of the submerged water rises, the amount of heat removed from the core by the SG increases, so when the submerged water rises to a certain temperature, the SG becomes able to remove the entire core decay heat, thereby limiting the temperature rise. Cooling in the SG is performed by natural circulation (convection), so no power source is required. ■As described above, direct steam release from the rupture port into the containment vessel is prevented, the submerged water is cooled by cooling the steam generator, and the pressure increase in the containment vessel is suppressed. ■The layout of the steam generator room is made compact, and the amount of water required to submerge the primary coolant pipes is minimized, allowing for early submersion of the break points.

In the example shown in FIG. 2, an accumulator tank with a line for nitrogen pressurization to carry out a rapid injection into the primary system after LOCA, and an injection line from the accumulator tank into the reactor vessel. In addition, we installed a gravity injection tank, which is the main source of submerged water, and an injection line from there to the primary coolant piping.

[0021]

[Effects of the Invention] As explained above, according to the present invention,
It is possible to eliminate the long piping from the large, high-performance containment vessel spray pump used in conventional technology and the containment vessel spray pump installed outside the reactor containment vessel to the containment vessel. Emergency power supply equipment will also become unnecessary. Furthermore, since it has the same ability as the conventional technology in suppressing the increase in pressure in the containment vessel and reducing the pressure in the event of an accident, it is possible to reduce costs.

[Brief explanation of the drawing]

FIG. 1 illustrates a method of suppressing a pressure rise in a containment vessel according to the present invention.

FIG. 2 shows a configuration example of a pressure rise suppression system according to the present invention.

FIG. 3 shows the concept of a cooling method using a steam generator as an example of a submerged water cooling method.

FIG. 4 shows a design example of a containment vessel pressure suppression system using a spray method within the containment vessel according to the prior art.

FIG. 5 shows changes in containment vessel pressure due to the containment vessel pressure rise suppression system, in which the solid line indicates the conventional technique and the broken line indicates the case according to the present invention.

[Explanation of symbols]

1 Reactor vessel 2, 3, 4 Piping 5, 6 Isolation valve 7, 8 Check valve 9 Pressure accumulator tank 10 Gravity injection tank

Claims (1)

[Claims] Claim 1: In a reactor containment vessel pressure rise suppression device for a pressurized water reactor, a primary coolant circulation system consisting of a reactor vessel, a steam generator, and a primary coolant pump is configured, and Connect the piping from the gravity injection tank located higher than the reactor vessel to the piping via an isolation valve and check valve, and connect the piping from the pressure accumulation tank through another isolation valve and check valve. A reactor containment vessel pressure rise suppressing device, characterized in that the device is connected to a wall of the reactor vessel at a downcomer portion of the reactor vessel.