JPH0651087A - Water refilling method for nuclear reactor - Google Patents

Abstract

PURPOSE:To facilitate restitution to normal operation after the end of a transient phenomenon in a nuclear reactor by using only a condensate storage chamber during transient phenomenon using a logic circuit for changing over of refill water source. CONSTITUTION:A nuclear reactor containment 2 has a pressure vessel 1, dry well 3, and suppression pool 4, and the water in a condensate storage chamber 7 is refilled to the vessel 1 by a pump 8 in the condition that motor-driven valves 5, 6 are opened and shut, respectively, when the reactor water has sunk due to transient phenomenon in the nuclear reactor. Also when the reactor water is missing due to rupture of the piping, the refill water in the chamber 7 is supplied with the valves 5, 6 opened and shut. When the water level in the chamber 7 measured by a water level gauge 10 has become below the specified level, it is sensed and a low-level informing signal is emitted 11, and a logic circuit for changing over of water source turned open and shut the valves 5, 6, respectively, and thus changing-over of the refill water source takes place, and the pump 8 sends the water stored in the pool 4 into the vessel 1. During the transient phenomenon in the reactor, therefore, the water in the pool 4 will never flow into the reactor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying reactor water to a nuclear reactor.

[0002]

2. Description of the Related Art Conventionally, a system having a function of replenishing reactor water when the reactor water level is lowered due to a reactor transient event, that is, a makeup water source of a reactor isolation cooling system (RCIC), has a condensate storage tank and a suppression pool. However, the water sources are diversified by using them together.

Further, in the reactor isolation cooling system of a boiling water reactor (BWR) plant, when the water level in the condensate storage tank drops, the makeup water source is switched to the suppression pool, and this switching work is done manually. Has been done.

On the other hand, an improved boiling water reactor (ABWR)
In the plant, the reactor isolation cooling system is incorporated into an emergency core cooling system (ECCS) network to strengthen the high pressure system emergency core cooling system. Along with this, when reactor water is lost due to pipe breakage and reactor water flows into the suppression pool, and the water level in the suppression pool rises, the pressure in the containment vessel is rising.

In order to automatically suppress the pressure increase in the containment vessel, the initial design of the improved boiling water reactor is similar to the high pressure emergency core cooling system in the conventional boiling water reactor plant. The following automatic switching logic was planned for water source switching. An explanatory diagram of this automatic switching logic is shown in FIG.

That is, FIG. 5 shows that when a condensate storage tank is used as a supplementary source of reactor water, when the condensate storage tank has a low water level or the suppression pool has a high water level, It indicates that the condensate storage tank will be switched to the suppression pool.

[0007] The automatic switching logic is based on the Kashiwazaki-Kariwa Nuclear Power Plant, Reactor Installation Change Permission Application (3,
(Addition of No. 4 reactor) [April 1985 (partial amendment in April 1986) (Partial amendment in February 1987) Attachment 8, Section 5.2.4.3 of Tokyo Electric Power Company ],
This is a known technique.

In addition to the function of the emergency core cooling system, the reactor isolation cooling system also has the function of replenishing reactor water at the time of a transient reactor event installed in a conventional boiling water reactor plant. ing.

That is, when the suppression pool has a high water level not only when the reactor water is lost but also when the reactor transient event occurs, as shown in the automatic switching logic of FIG.
The makeup water source was switched, and the stored water in the suppression pool, which was not desirable in terms of water quality as makeup water, was being supplemented into the furnace.

[0010]

As described above, in the example of the prior art, if the suppression pool has a high water level even during a reactor transient event, a suppression pool that is not preferable in terms of water quality is used as a makeup water source.

However, the stored water in the suppression pool contains a large amount of Fe clad and the like, and when a large amount of Fe clad flows into the reactor, complicated work such as draining of water is required after the reactor transient event has been safely completed. Is required, and recovery to normal operation is not easy. In addition, even if the amount of water in the suppression pool is small, it is not preferable in terms of operation and maintenance.

It is an object of the present invention to use a condensate storage tank as a source of make-up water for reactor water during a reactor transient event,
It is to facilitate recovery to normal operation after the end of a reactor transient event.

[0013]

The above object can be achieved as follows.

(1) Reactor water replenishment function when reactor water level is lowered due to reactor transient event and reactor water replenishment function when reactor water is lost due to pipe breakage A condensate storage tank that stores water of the same quality as that of water and a suppression pool that stores water that is not suitable for reactor water are installed. In the method, a condensate storage tank is used as a source of supplementary water for reactor water when the reactor water level decreases due to a reactor transient event, and a condensate storage tank is used as a source of supplementary water for reactor water when pipe water is lost. Use tank or suppression pool.

(2) It has a function of supplying reactor water when the water level of the reactor water drops due to a transient event of the reactor, and a function of supplying reactor water when the reactor water is lost due to pipe breakage, and serves as a source of reactor water supply. A condensate storage tank that stores water of the same quality as that of water and a suppression pool that stores water that is not suitable for reactor water are installed. In the method, a condensate storage tank is normally used as a makeup water source, and only when the water level in the condensate storage tank falls below the specified value, or when the water level in the suppression pool is above the specified value and the reactor water is lost. , Switching the make-up water source The make-up water source is switched from the condensate storage tank to the suppression pool by the logic circuit.

(3) In (2), a branch pipe for draining a part of the stored water from the middle of the pipe for replenishing the stored water of the suppression pool to the core is installed, and an electric valve is attached to the pipe and the branched pipe. When the condensate storage tank is used as a makeup water source, if the water level in the suppression pool exceeds the specified value and drainage of the stored water in the suppression pool becomes necessary, electric power is supplied to drain the stored water in the suppression pool. Actuating the valve.

[0017]

In the present invention, the logic circuit for switching the makeup water source from the condensate storage tank to the suppression pool is assembled. That is, the water level high signal of the suppression pool and the reactor water loss signal are combined by an AND circuit, and the AND circuit and the water level low signal of the condensate storage tank are combined by an OR circuit.

In the above circuit, even if the suppression pool water level signal is output during a reactor transient event, as long as the reactor water loss signal or the condensate storage tank water level signal is not output,
The source of makeup water to the core will not be switched from the condensate storage tank to the suppression pool.

Therefore, during a reactor transient event,
Only the high water level signal of the suppression pool prevents the stored water of the suppression pool, which is not desirable in terms of water quality, from flowing into the furnace.

The stored water in the suppression pool is
Since a facility for draining water is provided as needed, the space above the suppression pool can be maintained, and the function of suppressing the pressure increase of the containment vessel caused by the high water level of the suppression pool can be maintained.

[0021]

EXAMPLE An example of the present invention will be described with reference to FIGS.

First, an embodiment of the present invention will be described. FIG. 1 is an explanatory diagram of an embodiment of the present invention, showing an embodiment of a water source switching logic in a reactor isolation cooling system.

The reactor containment vessel 2 has a reactor pressure vessel 1, a drywell 3 and a suppression pool 4. When the reactor water drops due to a transient reactor event, the motor-operated valve A5 is opened and the motor-operated valve is operated. Condensate storage tank 7 with B6 closed
Is stored in the reactor pressure vessel 1 by the pump A8.

Similarly, when the reactor water is lost due to pipe breakage, the stored water in the condensate storage tank 7 is used with the electric valve A5 open and the electric valve B6 closed.

Then, the water level of the condensate storage tank 7 is measured using the water level gauge 10 for the condensate storage tank, and when the water level of the condensate storage tank 7 becomes less than a specified value, it is sensed, A signal for informing the low water level of the condensate storage tank 7 is transmitted, and by this signal,
By the logic circuit, the electric valve A5 is closed and the electric valve B6 is opened to switch the makeup water source, and the stored water in the suppression pool 4 flows into the reactor pressure vessel 1 by the pump A8.

The above logic circuit is shown in FIGS. FIG. 2 is a flow chart of a makeup water source switching logic of one embodiment, and FIG. 3 is a flow chart of a transmission valve switching logic of one embodiment.

2 and 3, the suppression pool water level high signal and the reactor water loss signal are combined by an AND circuit, and the AND circuit and the water level low signal of the condensate storage tank 7 are combined by an OR circuit. 2 is when the makeup water source is changed from the condensate storage tank 7 to the suppression pool 4, and FIG.
What is actually performed to bring the state of FIG. 2, that is, when the electric valve A5 is opened and the electric valve B6 is closed and the electric valve A5 is closed and the electric valve B6 is opened,
Shown respectively.

With the water level gauge 9 for the suppression pool,
When it is detected that the water level in the suppression pool 4 has exceeded the specified value, a signal notifying the high water level in the suppression pool 4 is transmitted. However, in this state, a signal (L in FIG.
Only when the (OCA signal) is transmitted from the transmission point 11, the motor-operated valve A5 is closed and the motor-operated valve B6 is opened by the logic circuit of FIG. 3, and the makeup water source is condensed as shown in the logic circuit of FIG. The storage tank 7 is switched to the suppression pool 4.

When the makeup water source is switched to satisfy the condition of FIG. 2, the logic circuit of FIG. 3 is used.
If 6 does not open, the motor-operated valve A5 will not close.
Therefore, the route of the makeup water source is not blocked and the makeup water can be continuously supplied.

For each signal (low water level in the condensate storage tank, high water level in the suppression pool, reactor water loss signal due to pipe breakage) in the logic circuit of the present embodiment, the instrument is multiplexed, for example, 2OUT OF 3 By incorporating logic etc. for each signal, malfunction due to a single failure of the instrument can be avoided.

Next, another embodiment of the present invention will be described. FIG. 4 is an explanatory view of another embodiment of the present invention, showing the connection of the supply system of makeup water to the core in the suppression pool shown in FIG. 1 to the drainage system.
That is, another embodiment of the present invention is incidental to the above-described one embodiment of the present invention.

In FIG. 4, the condensate storage tank 7 (see FIG. 1)
When the suppression pool 4 reaches a high water level in a state in which is used as a makeup water source, the stored water in the suppression pool 4 is in a state where the electric valve C13 is open, the electric valve D16 is open, and the electric valve E17 is closed. Then, the water is drained through the heat exchanger 15 by the pump B14.

In the above state, when the signal of reactor water loss due to pipe breakage is transmitted, the suppression pool 4
The motor-operated valve D16 on the line leading to the drainage of the stored water is closed, the motor-operated valve E17 is opened in synchronization with this, and the stored water in the suppression pool 4 is passed through the heat exchanger 15 by the pump B14 to the reactor pressure. It is sent into the container 1.

In this embodiment, a residual heat removal system is used as a means for draining the stored water in the suppression pool 4 at the time of a nuclear reactor transient event, and the residual heat removal system is used to pass through the heat exchanger 15. In this case, the stored water in the suppression pool 4 is drained, and it is not necessary to install a heat exchanger in order to drain the stored water in the suppression pool 4.

[0035]

EFFECTS OF THE INVENTION According to the present invention, as a supplementary water source for reactor water at the time of a transient reactor event, until the water level in the condensate storage tank falls below a specified value, the stored water in the condensate storage tank which is preferable in terms of water quality. Can be used to facilitate recovery to normal operation after the successful completion of a reactor transient.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is a flow chart of makeup water source switching logic of one embodiment of the present invention.

FIG. 3 is a flow chart of a transmission valve switching logic according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram of another embodiment of the present invention.

FIG. 5 is an explanatory diagram of a makeup water source switching logic of a conventional example.

[Explanation of symbols]

1 ... Reactor pressure vessel, 2 ... Reactor containment vessel, 3 ... Dry well, 4 ... Suppression pool, 5 ... Motorized valve A, 6
… Motor operated valves B, 7… Condensate storage tank, 8… Pump A, 9… Suppression pool water level gauge, 10… Condensate storage tank water level gauge, 11… Signal transmission point, 12… Check valve, 13… Electric Valve C, 14 ... Pump B, 15 ... Heat exchanger, 16 ... Motorized valve D, 17 ... Motorized valve E.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Kikuchi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (3)

[Claims] 1. A reactor water replenishment function when the reactor water level is lowered due to a reactor transient event, and a reactor water replenishment function when the reactor water is lost due to pipe breakage. A condensate storage tank that stores water of the same quality as the reactor water as a water source, and a suppression pool that stores water that is not desirable in terms of water quality as the reactor water are installed to replenish the reactor water. In the reactor water supply method for a nuclear reactor, the condensate storage tank is used as a source of the supply water for the reactor water when the reactor water level decreases due to the reactor transient event, and the reactor water is lost when the reactor water is lost due to the pipe breakage. The reactor water supply method for a nuclear reactor, wherein the condensate storage tank or the suppression pool is used as a supply source of reactor water. 2. The reactor water replenishment function when the reactor water level is lowered due to a reactor transient event, and the reactor water replenishment function when the reactor water is lost due to pipe breakage. A condensate storage tank that stores water of the same quality as the reactor water as a water source, and a suppression pool that stores water that is not desirable in terms of water quality as the reactor water are installed to replenish the reactor water. In the reactor water replenishment method of the nuclear reactor, normally use the condensate storage tank as the makeup water source, if the water level of the condensate storage tank is less than a specified value,
Alternatively, the water level of the suppression pool is a specified value or more, and only when the reactor water is lost, the makeup water source switching logic circuit switches the makeup water source from the condensate storage tank to the suppression pool. Reactor water supply method to do. 3. A branch pipe for draining a part of the stored water from the middle of a pipe for supplying stored water of the suppression pool to the core is installed, and an electric valve is attached to the pipe and the branch pipe. In the state where the condensate storage tank is used as a makeup water source, when the water level of the suppression pool is equal to or higher than a specified value and the stored water of the suppression pool needs to be drained, the stored water of the suppression pool is drained. The reactor water supply method for a nuclear reactor according to claim 2, wherein the motor-operated valve is operated so as to do so.