JPH0132902B2 - - Google Patents

Description

Detailed Description of the Invention The present invention is a central control room ventilation air conditioning system for preventing radioactive materials from directly flowing into the central control room (hereinafter referred to as the "main control room") in the event of a radiation release accident in a nuclear power plant. system (hereinafter referred to as the central operation ventilation system).

At a nuclear power plant, operators are permanently stationed in the central control room, and during normal operation they operate and monitor the plant, and in the event of an accident, they check the functionality of the various safety equipment installed in the plant or take safety measures. It is the place that performs the central functions of the Ituta Nuclear Power Plant. Therefore, an environment must be maintained in the central control room that does not interfere with the proper behavior of operators under any circumstances. As one measure to this end, the central operating room is equipped with a central operating room ventilation system, which appropriately controls the atmospheric temperature and humidity inside the central operating room, and at the same time, under normal conditions, outside air is introduced at a fixed rate. The design is such that the atmosphere inside the central control room is fresh and that operators do not suffer from oxygen deficiency. However, in the event of a nuclear reactor accident that involves the release of radioactive materials, if the central operating room ventilation system is not isolated, the radioactive materials will flow directly into the central operating room, causing operators to be exposed to radiation. In this case, it becomes necessary for operators to evacuate from the central control room. To avoid such situations, nuclear power plants have traditionally
A central operating room ventilation system has been installed to prevent radioactive materials from directly flowing into the central operating room in the event of a loss of coolant accident, which would have the most severe impact on the inner core fuel.

A conventional example of a central operating ventilation system will be described below based on the drawings.

In Figure 1, when the reactor is in normal operation, the atmosphere inside the central operating room 1 passes through the recirculation pipe 2,
The suction force of the blower 3 causes the air to pass through the air conditioner 4 and return to the central operating room 1 again. The air conditioner 4 includes a cooler, a heater, a filter, etc., and has the function of maintaining the circulated atmosphere at an appropriate temperature and at the same time removing dust floating in the atmosphere to purify the atmosphere. On the other hand, a certain amount of outside air is taken in from the outside air intake port 5, passes through the isolation valve 6, merges with the circulating atmosphere, and is passed through the air conditioner 4 by the suction force of the blower 3 to the central control room. be introduced within. A part of the atmosphere in the central operating room 1 is discharged into the atmosphere from an exhaust port 8 by an exhaust fan 7. The amount of exhaust air discharged from the exhaust port 8 and the amount of intake air introduced from the outside air intake port 5 are balanced and equal. If a reactor loss of coolant accident occurs while the central operating room ventilation system is operating under these conditions, an accident signal will be input to the central operating room ventilation system isolation switch 9 installed in the central operating room 1. Central operation ventilation system isolation switch 9 is turned on.
As a result, the isolation valve 6 and the exhaust fan 7, which are electrically connected to the central operation ventilation system isolation switch 9, are automatically closed and stopped, respectively.

When a loss of coolant accident occurs, the accident signal that is detected in the nuclear power plant and input to the central control ventilation system isolation switch is shown below.

1A Reactor containment vessel pressure high signal, 2A Reactor water level low signal, 3A Reactor building radioactivity high signal.

A loss of coolant accident occurs when a pipe connected to a reactor pressure vessel ruptures, and the high-temperature, high-pressure coolant contained within the reactor pressure vessel causes damage to the reactor capacity that houses the reactor pressure vessel. This was an accident in which the liquid leaked into the container. In the event of a loss-of-coolant accident, high-temperature, high-pressure coolant flows out and rapidly depressurizes and boils, causing a sudden rise in pressure inside the reactor containment vessel, and pressure gauges installed inside the reactor containment vessel indicate that the reactor An accident signal of high containment vessel pressure is detected. In addition, since coolant flows out from the reactor pressure vessel, a water level gauge installed in the reactor pressure vessel detects an accident signal indicating a low reactor water level. Furthermore, radioactive fission products are released from the core fuel stored in the reactor pressure vessel and fill the reactor containment vessel, but these fission products are released outside the reactor containment vessel, albeit in very small amounts. leak. As a result, the radiation level inside the reactor building, which is installed to further contain the reactor containment vessel, increases. A radiation monitor installed inside the reactor building detects this increase in radiation level, and an accident signal of high radioactivity inside the reactor building is detected. These accident signals of high reactor containment vessel pressure, low reactor water level, and high radioactivity in the reactor building are all input to the central operating room ventilation system isolation switch. The ventilation system isolation switch is turned on. However, depending on the design of the plant, only the accident signal of high radioactivity in the reactor building is input to the central operation ventilation system isolation switch. In this way, when a loss of coolant accident occurs within a nuclear power plant, the central operating room ventilation system is always urgently isolated, and fission products are prevented from flowing directly into the central operating room. However, in nuclear power plants, the radioactivity release accident that must be assumed to occur for safety reasons is not limited to the aforementioned loss of coolant accident, but there are many other accidents that can be considered. Despite this, the conventional design has been such that automatic isolation of the central operating room ventilation system is not performed in the event of a radioactivity release accident other than a loss of coolant accident, and there is a risk that operators in the central operating room may be unduly exposed to radiation. It was hot.

The purpose of the present invention is to improve the shortcomings of conventional central operating room ventilation systems, and to prevent radioactive materials from directly flowing into the central operating room even in the event of a nuclear power plant accident involving the release of radioactive materials other than a loss of coolant accident. The objective is to obtain a central operation ventilation system that can prevent the above problems.

An embodiment of the present invention will be described below based on the drawings. The present invention has an outside air intake 5 as shown in FIG.
A new radiation monitor 10 is installed near the radiation monitor, and the electrical signal from this radiation monitor is used as an input signal to the central operation ventilation system isolation switch. The configuration of other parts of the central operating ventilation system according to the present invention is the same as that of the conventional central operating ventilation system.
However, all accident signals that can be detected at the nuclear power plant shall be input to the central control ventilation system isolation switch.

In addition, when multiple reactors are installed on the same site, the accident signal from any reactor is used as the input signal to the isolation switch for the internal ventilation system of all remaining reactors.

The accident signals that can be detected in a nuclear power plant and serve as input signals for the central control ventilation system isolation switch are shown below.

1A Reactor containment pressure high signal, 2A Reactor water level low signal, 3A Reactor building radiation high signal, 4A Main steam flow rate large signal, 5A Main steam tunnel temperature high signal, 6A Main steam radiation high signal, 7A Cooling Material purification system differential flow rate large signal, 8A Coolant purification system equipment room temperature high signal, 9A Residual heat removal system flow rate large signal, 10A Residual heat removal system equipment room temperature high signal, 11A Turbine building area radiation monitor radioactivity high signal, 12A Waste treatment building area radiation monitor radioactivity high signal, 13A Exhaust stack monitor radioactivity high signal. ” Here, the above 1A to 13A signals will be explained. Note that the above-mentioned signals from 1A to 3A were explained in the conventional example, so they will be omitted, and the signals below 4A will be explained.

A loss of coolant accident occurred when the piping connected to the reactor pressure vessel was ruptured, and the high-temperature, high-pressure coolant contained within the reactor pressure vessel was used to damage the reactor containment vessel that houses the reactor pressure vessel. This is an accident where the water leaks out of the system. 1A above to detect this accident
There is a 10A signal from.

First, the main steam flow rate large signal 4A is a signal that is transmitted when main steam in the main steam piping connected to the reactor pressure vessel leaks and the flow rate of the main steam exceeds a predetermined value. The main steam tunnel temperature high signal 5A indicates that when main steam leaks from the main steam pipe as described above, the main steam accumulates in the main steam tunnel surrounding the main steam pipe and the temperature exceeds the predetermined value. This is the signal sent when The main steam radioactivity high signal 6A occurs when the water level in the reactor pressure vessel decreases, part of the fuel is damaged, and the radioactivity in the main steam where the fuel is diffused into the cooling water exceeds a predetermined value. This is a signal sent to The large differential flow rate signal 7A of the coolant purification system indicates that a leakage accident has occurred in a part of the coolant purification system connected to the reactor pressure vessel via piping, and the flow rate at the inlet and outlet of the coolant purification system are different. This is a signal that is sent when the differential flow rate calculated from the difference in flow rates at the two points exceeds a predetermined value. The high temperature signal 8A in the coolant purification system equipment room indicates that a leak has occurred from the coolant purification system in the coolant purification system equipment room where equipment (pumps, etc.) that constitute a part of the coolant purification system are installed. In this case, the indoor temperature rises to a predetermined value or higher due to the leaked steam. This is the signal sent in this case. The residual heat removal system flow rate large signal
9A, a leakage accident occurred in a part of the residual heat removal system connected to the reactor pressure vessel via piping.
This is a signal sent when the flow rate of the residual heat removal system exceeds a predetermined value. In addition, the residual heat removal system equipment room temperature high signal 10A indicates that a leakage accident occurred from the residual heat removal system in the residual heat removal equipment room where equipment (pumps, etc.) that constitute a part of the residual heat removal system is installed. However, this signal is sent when the indoor temperature rises to a predetermined value or higher due to the leaked steam.

Furthermore, due to some reason, such as an accident occurring at another nuclear reactor on the same site, radioactivity exceeding a specified value is detected in the turbine building, waste treatment building, or exhaust stack attached to the reactor building. Turbine building area radiation monitor in case of high radioactivity signal
11A, waste treatment building area radiation monitor high radiation activity signal 12A, and exhaust stack monitor high radiation activity signal 13A are transmitted.

Next, the operation of the present invention will be explained. When a nuclear power plant accident involving the release of radioactive materials occurs, depending on the wind direction, the radioactive materials move to the vicinity of the outside air intake port 5 of the central operating ventilation system. The radiation monitor 10 detects the radiation of this radioactive substance and inputs an accident signal indicating the radioactivity level of the outside air intake port to the central operation ventilation system isolation switch 9 via the electric cable 11. In response to this, the central operating ventilation system isolation switch 9 is turned on, and the isolation valve 6 and exhaust fan 7, which are electrically connected to the central operating ventilation system isolation switch 9, are urgently closed and stopped, respectively. Additionally, if an accident signal is generated directly at the location of the accident in the nuclear power plant, the accident signal is directly input to the central operation ventilation system isolation switch, and thereafter the central operation ventilation system is isolated in the same way as above. .

The following effects can be obtained by the central ventilation system of the present invention having the above-mentioned functions. Even if a nuclear power plant accident occurs in a nuclear power plant that involves the release of radioactive materials, the radiation level in the central control room will be kept sufficiently low and will not interfere with post-accident countermeasures that are important for the safety of operators. must not. For this reason, conventional designs have been such that in the event of a loss of coolant accident, the central control ventilation system is immediately isolated and disconnected from outside air. However, there are many radioactivity release accidents other than coolant loss accidents that need to be assumed to occur for safety reasons at nuclear power plants, and when these occur, the central operating ventilation system is There was no automatic isolation, and there was a risk that radioactive materials could flow directly into the central control room. Since the central operating room ventilation system according to the present invention has its own radiation monitor, even if not only a coolant loss accident but also other radioactivity release accidents occur, an accident due to high radioactivity at the outside air intake will be detected. The isolation valve automatically closes in response to a signal, cutting off outside air and preventing radioactive materials from directly flowing into the central operating room. Additionally, if an accident signal is generated directly at the location of an accident within a nuclear power plant, the accident signal will directly isolate the central operation ventilation system, preventing radioactive materials from reaching the vicinity of the outside air intake of the central operation ventilation system. It is possible to isolate the central operating ventilation system before.

Furthermore, even if an accident occurs at another reactor on the same site, the central operating room ventilation system can be isolated based on the accident signal sent from that reactor.
As described above, according to the central operating ventilation system according to the present invention,
In the case of any radioactivity release accident that occurs on the premises of a nuclear power plant, the central operating ventilation system is immediately disconnected from the outside air, preventing radioactive materials from directly flowing into the interior, allowing operators to avoid undue radiation exposure. This has the effect of making it possible to take measures after an accident without being exposed to radiation.

[Brief explanation of drawings]

FIG. 1 is a system diagram schematically showing a central operating ventilation system in a conventional nuclear power plant, and FIG. 2 is a system diagram schematically showing an embodiment of a central operating ventilation system according to the present invention. 1... Central control room (center control room), 2... Recirculation piping, 3... Blower, 4... Air conditioner, 5... Outside air intake, 6... Isolation valve, 7... Exhaust fan, 8 ...Exhaust port, 9...Central ventilation system isolation switch, 10...
Radiation monitor, 11...electric cable.

Claims (1)

[Claims] 1 Air is taken into the central control room located in the nuclear power plant from the outside air intake via the isolation valve,
In a central control room ventilation air conditioning system that exhausts air from the central control room from an exhaust port via an exhaust fan, the isolation valve and the exhaust fan collect a predetermined amount of radiation from a radiation monitor disposed near the outside air intake. an accident signal of high outdoor air intake radioactivity that is transmitted when a high radiation level is detected; a high pressure signal of the reactor containment vessel that is transmitted when the pressure inside the reactor containment vessel exceeds a predetermined value; The reactor water level low signal is sent when the water level in the reactor pressure vessel installed in the reactor pressure vessel falls below a predetermined value, and the radioactivity in the reactor building housing the reactor containment vessel exceeds a predetermined value. The reactor building radioactivity high signal is sent when the reactor building radioactivity is high, and the main steam flow rate is sent when the flow rate of main steam flowing in the main steam piping connected to the reactor pressure vessel exceeds a predetermined value. A large signal, a main steam tunnel temperature high signal that is sent when the temperature in the main steam tunnel surrounding the main steam pipe exceeds a predetermined value, and a radiation dose in the main steam flowing through the main steam pipe is a predetermined value. The main steam radioactivity high signal is transmitted when the radioactivity exceeds the specified value, and the differential flow rate determined from the difference between the inlet flow rate and outlet flow rate of the coolant purification system connected to the reactor pressure vessel via piping is a predetermined value. A coolant purification system difference flow rate large signal is sent when the temperature exceeds a predetermined value, and the temperature of the coolant purification system equipment room in which equipment forming part of the coolant purification system is installed exceeds a predetermined value. A high temperature signal in the coolant purification system equipment room is transmitted when the temperature in the equipment room of the coolant purification system is high, and a residual heat signal is transmitted when the flow rate in the residual heat removal system connected to the reactor pressure vessel via piping exceeds a predetermined value. Removal system flow rate large signal,
A residual heat removal system equipment room temperature high signal that is transmitted when the temperature of the residual heat removal system equipment room in which equipment constituting a part of the residual heat removal system is installed exceeds a predetermined value; Turbine building area radiation monitor radioactivity high signal transmitted when the value measured by the radiation monitor installed in the turbine building located on the side of the building exceeds a predetermined value, the reactor building A waste treatment building area radiation monitor radioactivity high signal that is transmitted when the value measured by a radiation monitor installed in the waste treatment building located on the side of the waste treatment building exceeds a predetermined value; Closes and stops in response to one of the exhaust stack monitor radioactivity high signals that are sent when the measured value of radioactivity in the stack, which releases exhaust gas from the nuclear power plant into the atmosphere, exceeds a predetermined value. A central control room ventilation air conditioning system characterized by comprising: