JP2953787B2 - Light water reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light water reactor having a nuclear reactor with improved resistance to severe accidents.

[0003]

2. Description of the Related Art An improved boiling water reactor (hereinafter referred to as ABWR) is one of the safest reactors of a conventional light water reactor plant. This ABWR
FIG. 8 is a basic configuration diagram of an emergency core cooling system (hereinafter, referred to as ECCS) arranged in the reactor building 1 of the first embodiment. A
The BWR ECCS basically consists of three sections, two of which are a high pressure core flooding system (hereinafter referred to as HPCF) 2, and the other section is a reactor isolation cooling system (hereinafter referred to as RCIC). 3) are arranged respectively.

A low-pressure core flooding system (hereinafter referred to as LPCF) 4 is disposed in each section of the reactor building 1, and each of the LPCF 4 and the HPCF 2 is driven by an electric pump (motor-driven pump). Water is injected into the reactor. For this reason, HP
AC power supply is required for operation of CF2 and LPCF4,
Emergency AC power supply (Emergency D) for each section in reactor building 1
G) 5 are arranged one by one. In addition, since LPCF4 also has a function as a residual heat removal system (hereinafter, referred to as RHR), it is represented as LPCF / RHR in FIG.

On the other hand, a reactor isolation cooling system (RCI)
C) 3 drives a pump directly by a turbine using steam generated from the reactor to inject water into the reactor. Therefore, no AC power supply is required for the operation of the RCIC 3, but on the other hand, it is designed to require a DC power supply for turbine control and the like, and an emergency DC power supply (emergency DC) 6 is separately provided. It is provided as a station battery. Although the station battery is shown in FIG. 8 as being included in the same section as the RCIC 3, the station battery is not actually included in a specific section and is commonly used throughout the light water nuclear power plant.

Further, the reactor building 1 of the ABWR shown in FIG.
In the description of each section means a physically separated section,
In consideration of the safety importance of the Emergency Core Cooling System (ECCS), each of the ECCSs is designed to increase the separation and independence of each other so that a fire or flood in one section does not adversely affect other sections. Classification is set. Actually, the sections are physically separated from each other by a fire wall or a waterproof door for safety, and the power sections are also set independently of each other electrically.

As described above, in the design of the ABWR ECCS, the redundancy and separation independence of the equipment are sufficiently enhanced, and the ABWR has much higher safety than the conventional light water reactor. In this sense, ABWR can be said to be a second-generation safety reactor if the conventional light water reactor is the first generation.

[0008] However, even if the ABWR is driven by a human being, and a human being has a basic ergonomic position that there is a risk of making a mistake, the ABWR may be so-called that the core fuel is excessively damaged. A serious core damage accident (SCDA) may occur. To be more precise, such a possibility may not exist at all, but nevertheless, a safety design shall be made so that even if such a case would occur, it would not have an undue adverse effect on the general public. There is also the idea.

If a core damage accident (SCDA) occurs in the ABWR, external power is lost due to a lightning strike, typhoon, snowfall, earthquake, or some other internal factor. One of the most probable causes is the occurrence of a so-called all AC power loss event (hereinafter referred to as SBO) in which all the AC power supplies (emergency DGs) 5 fail.

When the total AC power loss (SBO) occurs, the high pressure core flooding system (HPCF) 2 and the low pressure core flooding system (LPCF) 4 driven by electric motors are all disabled, and the operable ECCS is a turbine driven RCIC 3. However, if it breaks down for some other reason, RCIC3 will not work,
There is no means for injecting water into the reactor, and the core starts to be damaged after about 1 hour, and core melting may occur after about 2 to 3 hours. Due to the melting of the core, the core may penetrate the lower part of the reactor pressure vessel and drop on the concrete floor surface of the lower drywell of the containment vessel.

When the molten state of the core is left as it is, the molten core further erodes the concrete floor surface, and the steam (carbon dioxide) separated from the concrete and the metal (Z
r and Fe) cause an oxidation reaction to promote heat generation. For this reason, due to the synergistic effect of the decay heat by the molten core and the heat generated by the oxidation reaction of this metal, the ambient temperature inside the containment vessel reaches an abnormally high temperature. ABWR
Of the containment vessel may be overheated, and radioactive materials that existed in the containment vessel during a core damage accident (SCDA) may be released to the environment. This will affect the general public and cause severe accidents (hereinafter referred to as SA).
That. ) Has occurred.

In the above description, the cooling system (RC
Although it is assumed that the IC 3 has failed for some reason, a DC power source (station battery) 6 is required for controlling the RCIC 3 turbine and the like. However, the battery 6 is designed to be depleted after about 8 hours, and if the total AC power loss (SBO) event continues for 8 hours or more, even if the RCIC 3 is not initially faulty, the same severe An accident may occur.

In the case of such a situation, in the United States and Europe, pipes are connected after the accident so that water can be injected into the reactor with a diesel-powered digestion pump so that some measures can be taken. Measures have already been taken, such as connecting a portable diesel-driven water injection pump truck from outside the reactor building to enable spray water to be sprayed into the reactor containment vessel.

However, since the digestive diesel-driven pump is not originally designed for such a purpose, sufficient seismic design has not been performed, and an earthquake is considered as a triggering event.
When BO occurs, it is highly possible that the BO becomes unusable.
In addition, when connecting pipes at the site after an accident, there is a situation in which total AC power loss (SBO) occurs at night and natural conditions such as earthquakes and typhoons overlap as a cause of SBO. It has to be assumed, and its feasibility is very uncertain. This is exactly the same when a portable diesel-driven water injection pump truck is used, and there is a great obstacle to the feasibility such as the problem of securing a water source.

[0015]

As described above, if AB
Assuming that a serious core damage accident (SCDA) occurs even in the case of WR, if this is left unchecked, the ambient temperature inside the reactor containment vessel (RCV) will reach an abnormally high temperature, and the reactor containment vessel will overheat. There is a risk of damage. Also,
If such a situation is dealt with by connecting digestive pumps or using a portable diesel-driven water injection pump truck, the feasibility is expected to be accompanied by large uncertainties and difficulties are expected.

The present invention has been made in view of the above-described circumstances, and prevents damage to the reactor core even if total AC power loss (SBO) has occurred, while preventing failure of the reactor core. An object of the present invention is to provide a highly reliable light water reactor capable of preventing overheating damage of a containment vessel even if damage occurs.

[Configuration of the Invention]

[0018]

In order to solve the above-mentioned problems, a light water reactor according to the present invention has an emergency cooling system and a low pressure core submergence system, as described in claim 1. And a second section and a third section basically comprising a high-pressure core flooding system, a low-pressure core flooding system, and an emergency power supply. A light water reactor, a high pressure water injection system having a high pressure water pump directly driven by a first diesel engine, in addition to the first, second and third sections physically separated from each other; And a low-pressure water injection system having a low-pressure water injection pump driven directly by a diesel engine.

Further, in order to solve the above-mentioned problem, the light water reactor according to the present invention, as described in claim 2, is characterized in that the high-pressure water injection pump and the low-pressure water injection pump include:
The motor is connected to a motor connected to an in-house power supply and an emergency power supply, and is also pump-driven by the motor in place of the first or second diesel engine.

[0020]

In the light water reactor according to the present invention, a new dedicated section is provided in the reactor building, and a high-pressure water injection system and a low-pressure water injection system driven by a diesel engine are installed in this section. Even when an event occurs, water is injected into the reactor to prevent damage to the core,
Even if core damage occurs, spraying water into the reactor containment using a low-pressure water injection system driven by a diesel engine prevents overheating damage to the containment and leakage of radioactive materials to the environment. This has further improved the performance.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a light water reactor according to the present invention will be described below with reference to the accompanying drawings.

The light water reactor according to the present invention has an ABWR
This is a so-called third-generation safety reactor, which is more improved in safety than (improved boiling water reactor). As shown in FIG. 1, this reactor has four safety systems 11 including an emergency core cooling system (ECCS) in a reactor building 10,
It is divided into 12, 13, and 14. The ECCS cools the reactor core in the event of a primary system rupture accident, maintains the integrity of the reactor core, and prevents the release of radioactive materials together with the containment vessel.

The first section 11 includes a cooling system (R
CIC) 15, a low pressure core flooding system (LPCF) and a residual heat removal system (RHR) 16, and an emergency AC power supply (emergency D
G) 17 are installed one by one. In addition, the second section 12 and the third section 13 include a high pressure core flooding system (HP
CF) 18, LPCF / RHR 16, and emergency DG 17 are installed one by one, and the first to third sections basically constitute an ECCS. Further, the fourth section 14 includes a high-pressure diesel-driven water injection system (hereinafter, referred to as HDIS) 19 as a high-pressure water injection system and a low-pressure diesel-driven water injection system (hereinafter, referred to as LDIS) as a low-pressure water injection system.
20 are installed one by one.

High-pressure diesel-driven water injection system (HDIS) 1
Numeral 9 is configured as shown in FIG.
This is a high-pressure water injection system in which water is injected from a suppression pool 23 or an external water source 24 into a nuclear reactor 22 stored in the reactor. The HDIS 19 has a high-pressure water injection pump 26 driven directly by a diesel engine 25 on the way. The diesel engine 25 is connected to a fuel tank 27,
Refueling is performed from the refueling tank 27.

The high pressure water injection pump 26 of the HDIS 19
The suction side is selectively connected to an external water source 24 and a suppression pool 23 via electric valves 28 and 29, and the pump discharge side is similarly connected to the reactor 22 via electric valves 31 and 32.
And a suppression pool 23.

However, water is injected into the reactor 22 by the electric valve 3
1 is opened, and the system test of the HDIS 19 is performed by opening the motor-operated valve 32.
The operation of each of the motor-operated valves 28, 29, 31, and 32 is all performed by a DC motor, and a dedicated DC power supply (not shown) is separately provided for driving the valves. This DC power supply can be charged from the small generator 33 as well. It has become. The small generator 33 is driven by the diesel engine 25.

FIG. 3 shows a low-pressure diesel-driven water injection system (LDI).
S) Schematic diagram of 20. LDIS20
Is a low-pressure water injection system for injecting cooling water in the external water source 24 and the suppression pool 23 into the upper and lower dry wells 35 and 36 in the reactor 22 and the containment vessel 21.
A low-pressure water injection pump 38 directly driven by a diesel engine 37 is provided on the way. The diesel engine 37 is supplied with oil from a fuel tank 39, and the small generator 40 is also driven by the diesel engine 37.

The suction side of the low-pressure water injection pump 38 is selectively connected to the external water source 24 and the suppression pool 23 via electric valves 41 and 42, and the pump discharge side is
It is connected to the spray header 47 in the upper drywell 35, the reactor 22, and the suppression pool 23 via the electric valves 43, 44, 45, 46. Although FIG. 3 shows an example in which the spray header 47 is provided only on the upper dry well 35 side, a spray header (not shown) may be separately provided on the lower dry well 36 side.

However, water is injected into the reactor 22 by the electric valve 4
5 and by opening the motor-operated valve 46 during the LDIS 20 system test. further,
The spraying of water into the reactor containment vessel 21 is performed by the electric valve 4
This is done by opening 3,44. Each motorized valve 4
All of the operations 1 to 46 are performed by a DC motor, and therefore a dedicated DC power supply (not shown) is separately provided. This DC power supply can be charged from the small generator 40.

FIGS. 2 and 3 show examples in which the high pressure diesel driven water injection system (HDIS) 19 and the low pressure diesel driven water injection system (LDIS) 20 are provided with an electric valve.
An air-operated valve or the like can be used in place of the electric valve. In this case, a nitrogen gas supply system or the like is provided for valve operation as needed.

Next, the operation of the light water reactor will be described.

When a light water reactor as a third generation safety reactor causes a total loss of AC power (SBO) due to any cause, a high pressure core flooding system (HPCF) which requires an AC power source for operation.
18 and the low pressure core flooding system (LPCF) 16 are all inoperable. Further, when the turbine driven reactor isolation cooling system (RCIC) 15 fails or the total AC power loss (SBO) event continues for 8 hours or more, and the battery is depleted and the RCIC 15 stops, the reactor pressure vessel (RPV)
The ECCS loses all functions as water injection means.
As a result, the cooling water in the reactor 22 evaporates due to the decay heat of the core fuel and is discharged from the steam relief valve, so that the reactor water level starts to decrease. High-pressure diesel-driven water injection system (HDIS) 1 by detecting that the reactor water level has dropped abnormally
9 automatically starts, and water injection into the reactor 22 is started. For this reason, the reactor water level is maintained at or above a certain value, the integrity of the core fuel is maintained, and the occurrence of a serious core damage accident (SCDA) is prevented.

Further, a high pressure diesel driven water injection system (HD
If the IS 19 fails, an abnormal drop in the reactor water level is detected and the low pressure diesel-driven water injection system (LDIS) 20 is detected.
Automatically starts, and enters a standby state in which water injection into the reactor 22 is started. Here, if the station battery still remains without being depleted, an automatic pressure reduction system (ADS) is operated using this DC power supply to depressurize the reactor. The detection system confirms that the reactor pressure has dropped below a predetermined pressure, and the low-pressure diesel-driven water injection system (LD
IS) 20 to issue a permission signal for water injection to the reactor 22. In response to the water injection permission signal, the LDIS 20 switches from the standby state to the water injection mode to the reactor, and starts water injection into the reactor 22. As a result, the reactor water level is maintained above a certain level, the integrity of the core fuel is maintained, and the core damage accident (SC
DA) is prevented.

On the other hand, if the station battery has already been depleted, the operation of the automatic pressure reduction system (ADS) becomes impossible, and the LDIS 20 remains in the standby state while the reactor 2
It is not possible to start water injection into 2. In this case, the reactor water level continues to decrease, and the core fuel is exposed, so that the core fuel may be damaged and melted by the decay heat generated by itself. The melting core then melts and penetrates the lower part of the reactor pressure vessel in a relatively short time, and the containment vessel 21
May be released into When the molten core is released into the containment vessel 21, the ambient temperature in the containment vessel 21 starts to rise rapidly due to its decay heat or the like. The low pressure diesel driven water injection system (LDIS) 20 detects that the ambient temperature inside the reactor containment vessel 21 has become abnormally high.
From the water injection mode to the reactor pressure vessel
The mode is switched to the water injection mode to 1 and spray water is sprayed into the reactor containment vessel 21, and the ambient temperature in the reactor containment vessel 21 decreases.

As a result, the reactor containment vessel 21 is prevented from being overheated and damaged, and the soundness of the reactor containment vessel 21 is maintained. A large amount of radioactive material is prevented from accumulating in the reactor containment vessel 21 and being directly released into the environment. Even if a serious core damage accident (SCDA) occurs, it is likely to occur around the reactor building (site) 10. This also prevents the occurrence of a severe accident (SA) that has a severe adverse effect.

Next, another embodiment of the light water reactor according to the present invention will be described with reference to FIGS.

FIGS. 4 and 5 show pumps 26 and 38 of the high-pressure water injection system and the low-pressure water injection system, respectively.
In addition to 7, the motor can be driven.

Specifically, the high-pressure water injection pump 26 of the high-pressure diesel-driven water injection system (HDIS) 19 is connected not only to the diesel engine 25 but also to a motor 50.
Even if it is 0, the pump driving force can be performed. The motor 50 is powered and driven by an in-house power supply and a new emergency AC power supply (emergency DG) 51.

Similarly, a low-pressure water injection pump 38 of a low-pressure diesel-driven water injection system (LDIS) 20 shown in FIG. 5 is connected to a motor 52 in addition to the diesel engine 37 so that the motor can be driven. Also in this case, the motor 52
Is connected to an in-house power supply and an emergency AC power supply (emergency DG) 51 and is driven in the same manner.

Another configuration is the HDI shown in FIGS.
Since they are not different from S19 and LDIS20, the same reference numerals are given and the description is omitted.

Thus, as shown in FIGS. 4 and 5,
By adding a motor drive function to the high-pressure diesel-driven water injection system (HDIS) 19 and the low-pressure diesel-driven water injection system (LDIS) 20, the reactor building 1 of the light water reactor can be used.
0, a new emergency AC power supply (emergency DG) 51 is newly installed as shown in FIG.
1 to 5 motors of HDIS19 and LDIS20
0, 52 are supplied. This emergency DG
Instead of 51, in some cases other categories 11, 12, 1
It is also conceivable to supply power to each of the motors 50 and 52 from the emergency DG 17 of No. 3.

In the light water reactor shown in FIGS. 4 to 6,
Since the HDIS 19 and the LDIS 20 can be driven by the motors 50 and 52 using an AC power supply, except for a total AC power loss (SBO) event, the normal high pressure core flooding system (HPCF) 2 and the low pressure core flooding system are used. (LPCF)
4 can also be used as an electric ECCS. This allows ABWR's ECCS network to meet the so-called N-2 standards in Europe and Germany and Sweden, where a single fault criterion is applicable even if one system is down for maintenance. That is, in this embodiment, a high-pressure diesel-driven water injection system (HDIS) added as a measure against severe accidents
19 and low pressure diesel driven water injection system (LDIS) 20
Can also be used to meet European regulatory standards.

Also, HDIS1 which is a severe accident countermeasure equipment
The HDIS can be shared with other plants in the reactor building (site) 10 by integrating the high-pressure water injection pump 26, the diesel engine 25, and the small generator 33, which are the main parts of 9, into a portable type. . This is LD
The same applies to the IS 20. It is conceivable that the low pressure water injection pump 38, the diesel engine 37, and the small generator 40 are integrated into a portable type. Here, the term “portable” refers to placing these devices on an integrated trolley so that they can be towed by a truck or other vehicle, or using these devices in a state where they are always installed on the truck bed from the beginning. There are things to do.

By making the HDIS 19 and LDIS 20 portable, even in the event of a severe accident, if a further failure occurs, a human response to the severe accident can be made by switching to the HDIS 19 and LDIS 20 of another plant on the same site. (Accident management) is obtained.

FIG. 7 shows a third embodiment of the light water reactor according to the present invention.
It shows an embodiment.

The light water reactor shown in this embodiment has a residual heat removal system (RH) in the fourth section 14 of the reactor building 10.
A heat exchanger of R) and an auxiliary equipment cooling system as a secondary system thereof are installed, and the low pressure diesel driven water injection system (LDIS) 20 has a function as a primary system of the RHR 55. The other configuration is not different from that shown in FIG.

In this case, an AC power supply is used as a drive source of the auxiliary cooling system, and power is supplied from the emergency DG 51. This will make it possible to meet European N-2 standards, including the RHR network, and greatly reduce the possibility of core damage due to loss of residual heat removal function when a nuclear plant is shut down (at regular inspection). The effect that can be reduced is obtained.

[0048]

As described above, in the light water reactor according to the present invention, the fourth section is provided as a new dedicated section in the reactor building, and the fourth section is directly provided by the first diesel engine. A high pressure water injection system with a driven high pressure water injection pump and a low pressure water injection system with a low pressure water injection pump driven directly by a second diesel engine ensure that even if a full AC power loss event occurs, Water is injected into the reactor to prevent damage to the core, and even if the core is damaged, spray water into the reactor containment vessel by spraying water into the reactor containment vessel using a diesel engine-driven low-pressure water injection system. It is possible to prevent the containment vessel from being damaged by overheating and to prevent radioactive substances from leaking into the environment, thereby further improving safety.

Even if the functions of the emergency core cooling systems of the first, second, and third categories are lost due to a situation such as a total AC power loss (SBO) event continuing for a long time, Since the cooling water in the reactor pressure vessel evaporates and is released from the steam relief valve, the reactor water level drops.In the present invention, however, the water level drop is detected, and the high-pressure core system automatically starts up and the reactor water level is reduced. Since water injection is started, the reactor water level is maintained to some extent, and the integrity of the core fuel can be maintained.

Further, in the light water reactor according to the present invention, the high pressure water injection system and the low pressure water injection system provided in the fourth section are the first water injection system.
And a high-pressure water pump and a low-pressure water pump directly driven by the second diesel engine, and a generator for driving the pump is not necessarily required. Therefore, the weight of the high-pressure water supply system and the low-pressure water supply system is reduced, and the system is simplified. This can contribute to improvement in maintainability.

Still further, as described in claim 2,
When the high-pressure water pump and the low-pressure water pump are connected to a motor connected to an in-house power supply and an emergency power supply and are configured to be driven by a motor instead of the first or second diesel engine, And low-pressure irrigation pumps can be driven by both diesel engines and motors, and in cases other than a total AC power loss event, these pumps can be driven by motors to provide high-pressure or low-pressure irrigation systems. Can also be used as an electric emergency core cooling system similar to the high pressure core flooding system and low pressure core flooding system, and each system of high pressure water injection system and low pressure water injection system of the fourth category as a countermeasure against severe reactor accidents And a highly reliable system capable of meeting European regulatory standards can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view of a light water reactor according to an embodiment of the present invention, showing a schematic layout of a safety system installed in a reactor building.

FIG. 2 is a system diagram showing an example of a high pressure diesel driven water injection system (HDIS) as a high pressure water injection system of a light water reactor.

FIG. 3 is a system diagram showing an example of a low-pressure diesel-driven water injection system (LDIS) as a low-pressure water injection system of a light water reactor.

FIG. 4 is a system diagram showing another example of a high-pressure diesel driven water injection system as a high-pressure water injection system.

FIG. 5 is a system diagram showing another example of a low-pressure diesel-driven water injection system as a low-pressure water injection system.

FIG. 6 shows another embodiment of the light water reactor according to the present invention, and is a schematic layout diagram of a safety system installed in a reactor building.

FIG. 7 is a schematic diagram of a light water reactor according to a third embodiment of the present invention, showing a safety system arranged inside a reactor building.

FIG. 8 is a schematic layout diagram of a safety system arranged in a reactor building of a conventional light water reactor.

[Explanation of symbols]

Reference Signs List 10 Reactor building 11 First section 12 Second section 13 Third section 14 Fourth section 15 Reactor isolation cooling system (RCIC) 16 Low-pressure core flooding system (LPCF) and residual heat removal system (RHR) 17 Emergency AC Power supply (emergency DG) 18 High pressure core flooding system (HPCF) 19 High pressure diesel driven water injection system (HDIS) 20 Low pressure diesel driven water injection system (LDIS) 21 Reactor containment vessel 22 Reactor 23 Suppression pool 24 External water source 25, 37 Diesel Engine 26 High-pressure water injection pump 27,39 Oil tank 33,40 Small generator 35,36 Drywell 38 Low-pressure water injection pump 47 Spray header 50,52 Motor 51 Emergency AC power supply (Emergency DG) 55 Residual heat removal system (RHR)

Claims (2)

(57) [Claims] A first section having a reactor isolation cooling system, a low-pressure core flooding system, and an emergency power source; a second section having a high-pressure core flooding system, a low-pressure core flooding system, and an emergency power source; In a light water reactor provided with an emergency core cooling system basically comprising a third section, a first diesel engine is provided in addition to the first, second and third sections which are physically partitioned. And a fourth section comprising a high-pressure water supply system having a high-pressure water supply pump directly driven by a second diesel engine and a low-pressure water supply system having a low-pressure water supply pump directly driven by a second diesel engine. Light water reactor. 2. The high-pressure water pump and the low-pressure water pump are connected to a motor connected to an in-house power supply and an emergency power supply, and are also pump-driven by the motor instead of the first or second diesel engine. The light water reactor according to claim 1, wherein: