JPH04236396A - Emergency core cooling device - Google Patents

Abstract

PURPOSE:To provide the emergency core cooling device efficiently utilizing GDCS pool water even if a rupture occurs in a piece of GDCS tubing of a nuclear reactor. CONSTITUTION:In the emergency core cooling system a differential pressure detector 12 is provided in the entrance side of a nuclear pressure vessel 1 of GDCS tubing 11 and an infection valve 13 opened on the basis of a loss-of- coolant accident signal and closed in the case where a reversed flow differential pressure signal is detected from said differential pressure detector 12 at the time of the opening actuation is connected to the GDCS tubing 11.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emergency core cooling system for cooling a boiling water reactor in the event of a loss of coolant accident.

0002

2. Description of the Related Art FIG. 4 shows a schematic diagram of a conventional direct cycle type simplified boiling water reactor. This will be explained below with reference to the drawings.

In FIG. 4, a reactor pressure vessel 1 housing a reactor core 2 is housed in a reactor containment vessel (not shown). The reactor core 2 is composed of a plurality of fuel assemblies and control rods (not shown), and the coolant 3 flows through the reactor core 2 from below to above, and is heated by the heat of nuclear reaction in the reactor core 2 . The heated coolant 3 enters a two-phase flow state of water and steam. The coolant 3 in this two-phase flow state is introduced into a steam separator (not shown) installed above the reactor core 2 and separated into steam and water. Further, the separated steam is introduced into a steam dryer (not shown) installed above the steam separator and dried to become dry steam. This dry steam is sent from above the reactor pressure vessel 1 via the main steam pipe 4 to a turbine generator in a turbine building (not shown) installed outside the reactor containment vessel, and is used for power generation. The steam used for power generation is condensed and guided into the reactor pressure vessel 1 through the water supply pipe 5.
The core 2 is cooled again using the coolant 3.

Incidentally, in a nuclear power plant, an accident (hereinafter referred to as LOCA) occurs in which various piping connected to the reactor pressure vessel 1 ruptures and part or most of the coolant 3 is released outside the reactor in a short period of time. With this in mind, various safety equipment has been installed to prevent the spread of these accidents.

That is, during a LOCA, coolant 3 is released from the reactor pressure vessel 1 into the reactor containment vessel. At this time, in order to prevent the water level of the cooling water 3 in the reactor pressure vessel 1 from falling and exposing the reactor core 2, a pressure reducing valve 6 is provided in the main steam pipe 4, and a gravity drop type core cooling system is installed. Pool (hereinafter referred to as GDCS pool) 7 is reactor pressure vessel 1
is installed above. GDCS pool 7 has GDC
S pipe 9 is connected. One end of this GDCS pipe 9 is connected to the reactor pressure vessel 1, and the coolant 3 is connected to the GDCS pipe 9.
A check valve 10 is provided in the GDCS pipe 9 to prevent leakage to the outside of the reactor pressure vessel 1 via the S pipe 9. In addition,
Although six GDCS pipes 9 are installed in one nuclear reactor facility, one pipe is shown in FIG. 4 for convenience.

[0006] In the nuclear reactor configured as above, the LOC
When A occurs, the pressure reducing valve 6 is opened by a signal indicating a low reactor water level or a high pressure in the containment vessel, that is, a LOCA signal, and the pressure in the reactor pressure vessel 1 rapidly decreases. When the pressure inside the reactor pressure vessel 1 drops to near atmospheric pressure,
GDCS pool water 8 in the GDCS pool 7 flows into the reactor pressure vessel 1 via the GDCS piping 9. Therefore, even if the coolant 3 flows out due to the occurrence of LOCA and the water level in the reactor pressure vessel 1 drops, the exposure of the reactor core 2 can be prevented by injecting the GDCS pool water 8 into the reactor pressure vessel 1. prevent the reactor from being cooled down safely.

[0007]

[Problem to be solved by the invention] As mentioned above, LOC
When reactor water level and reactor pressure decrease due to occurrence of A, GDCS pool water is injected into the reactor pressure vessel through all GDCS piping.

By the way, if a break occurs in the GDCS piping for some reason, a portion of the GDCS pool water flows out from the break and enters the GDC without being used for core cooling.
S pool water will be lost.

The present invention has been made in view of the above problems, and provides an emergency core cooling system that can effectively utilize GDCS pool water even if a rupture occurs in the GDCS piping due to some reason. The purpose is to [Structure of the invention]

0010

[Means for Solving the Problems] In order to achieve the above object, the present invention uses a gravity drop type core cooling system pool installed above the reactor pressure vessel as a water supply source, and in the event of a loss of coolant accident, the gravity In an emergency core cooling system that guides pool water in a drop-type core cooling system pool into the reactor pressure vessel via an injection pipe, a differential pressure detector is provided on the reactor pressure vessel inlet side of the injection pipe to cool the reactor pressure vessel. The injection pipe is provided with an injection valve that opens based on a coolant loss accident signal that is output at the time of a coolant loss accident, and that closes when a backflow differential pressure signal that is evaluated as a backflow is detected from the differential pressure detector during this operation. It is characterized by being arranged in.

[0011]

[Operation] In the emergency core cooling system configured in this way, even if a rupture occurs for some reason in the injection pipe that leads pool water into the reactor pressure vessel in the event of a loss of coolant accident, the rupture will not occur. The differential pressure detector evaluates that there is a backflow in the injection pipe, and the injection valve closes to detect the backflow differential pressure signal. Therefore, the pool water does not flow out from the fracture opening of the injection pipe, and therefore, there is no loss of pool water and it can be effectively used for core cooling.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of an emergency core cooling system according to an embodiment of the present invention. In addition, in the figure, the same parts as in FIG. 4 are indicated by the same reference numerals, and the explanation of the overlapping parts will be omitted. In FIG. 1, the GDCS piping 11 is connected to the GDCS pool 7 and is installed to guide the GDCS pool water 8 into the reactor pressure vessel 1 housing the reactor core 2. This GDCS piping 11 has an injection valve 1 that does not open normally.
3 is provided, and a differential pressure detector 12 is provided downstream of this injection valve.
is provided. Note that the injection port of the GDCS pipe 11 into the reactor pressure vessel 1 is provided above the reactor core 2.

FIG. 2 is a system diagram of an emergency core cooling system according to an embodiment of the present invention. In Figure 2, the reactor water level low 20 or dry well pressure high 21 signal, that is, the loss of coolant accident signal (hereinafter referred to as LOCA signal) and the differential pressure ΔP in the GDCS piping detected by the differential pressure detector are evaluated as backflow. A signal for opening the injection valve 23 is output based on both signals that are larger than the differential pressure α, that is, ΔP>α. here,
It is assumed that the flow direction in the GDCS piping is positive when it is from the GDCS pool to the reactor pressure vessel. Also,
The above-mentioned differential pressure α, which is evaluated as backflow, may vary depending on the nuclear reactor facility, so it should be investigated and set for each nuclear reactor facility.

FIG. 3 shows a schematic configuration diagram for explaining the functions of an emergency core cooling system according to an embodiment of the present invention when a GDCS pipe is ruptured. In the figure, parts that are the same as those in FIGS. 1 and 4 are designated by the same reference numerals, and overlapping explanations will be omitted.

In FIG. 3, when a rupture port 14 occurs in the GDCS pipe 11, the differential pressure detector 12 detects that the differential pressure ΔP in the GDCS pipe 11 is less than the differential pressure α, which is evaluated as a backflow. In other words, since ΔP≦α, even if the LOCA signal is output, the injection valve 13 is closed by the system shown in FIG.

By the way, there are usually multiple GDCS pipes, and in other healthy GDCS pipes with no breaks,
Since the differential pressure ΔP in the GDCS piping is larger than the differential pressure α that is evaluated as backflow, that is, ΔP>α, when the LOCA signal is output, the injection valve 13 is opened by the system shown in Fig. 2, and the GDCS pool is Water 8 flows into the reactor pressure vessel. With the above configuration, if a break occurs in the GDCS piping, the GDCS pool water will flow to the GDCS where the break occurred.
Since it is supplied into the reactor pressure vessel without going through piping, G
Prevents DCS pool water from flowing out from the break and prevents GD.
Core cooling can be performed without loss of CS pool water.

[0018]

[Effects of the Invention] As described above, according to the present invention, GD
Even if a break occurs in the CS piping, it is possible to prevent the GDCS pool water from flowing out from the break in the GDCS pipe, reducing the loss of GDCS pool water, allowing core cooling, and improving reactor safety. can contribute to improvement.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an emergency core cooling system according to an embodiment of the present invention.

FIG. 2 is a system diagram of an emergency core cooling system according to an embodiment of the present invention.

FIG. 3 is a functional explanatory schematic configuration diagram of an emergency core cooling system according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional emergency core cooling system.

[Explanation of symbols]

1...Reactor pressure vessel 2...Reactor core
3... Coolant 4... Main steam piping 5... Water supply piping
6...Pressure reducing valve 7...GDCS pool 8...GDCS pool water
9, 11...GDCS piping 10...Check valve 12...Differential pressure detector 13...Injection valve

Claims (1)

[Claims] Claim 1: A gravity drop type core cooling system pool installed above the reactor pressure vessel is used as a water supply source, and in the event of a loss of coolant accident, the pool water in the gravity drop type core cooling system pool is used as a water supply source. In the emergency core cooling system, which is guided into the reactor via an injection pipe, a differential pressure detector is installed on the reactor pressure vessel inlet side of the injection pipe, and an opening operation is performed based on a loss of coolant accident signal output in the event of a loss of coolant accident. An emergency core cooling system characterized in that an injection valve that closes when a backflow differential pressure signal that is evaluated as a backflow is detected from the differential pressure detector during this operation is disposed in the injection pipe. .