JP3133812B2 - Boiling water reactor and start-up method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiling water reactor and, more particularly, to a method for starting a boiling water reactor in which a circulation flow is ensured by a difference in hydrostatic head inside and outside a reactor core.

[0002]

2. Description of the Related Art In a current boiling water reactor, when a reactor is started after a cold shutdown, cooling water is circulated to a reactor core by a recirculation pump, a control rod is pulled out, and the cooling water is heated by nuclear heating. , Boost. At this time, since the core is cooled by forced circulation, the cooling water is in a single-phase flow state until the temperature becomes high, and the cooling water monotonically transitions from a single-phase flow state to a two-phase flow state with heating. Stable start-up of the reactor becomes possible.

On the other hand, at the time of start-up, at least during the period from the subcritical state to the opening of the isolation valve and the discharge of steam from the reactor, a boiling water type of a type in which the core is cooled by natural circulation of cooling water. In a natural circulation type reactor having a nuclear reactor, for example, without a recirculation pump, the natural circulation of cooling water in the core is driven by a hydrostatic head inside and outside a shroud surrounding the core. For this reason, when the cooling water is nuclear-heated in the core at the time of start-up after the cold shutdown of the reactor, the cooling water inside and outside the shroud circulates at a low flow velocity with the density difference due to the temperature difference as the driving force, and the water temperature rises and the core inlet When the cooling water subcooling degree becomes smaller than the maximum boiling start subcooling degree determined by the physical properties and the circulation flow rate, boiling occurs in the core. At this time, the difference in hydrostatic head inside and outside the shroud increases due to the generation of steam bubbles, and the circulation speed of the cooling water increases. As a result, the cooling amount of the core increases, and the cooling water in the core returns to a single-phase flow state,
These are repeated, and the two-phase flow and the single-phase flow state alternate, and flow fluctuation occurs. This unstable phenomenon becomes remarkable at a low temperature where the gas-liquid density ratio is large, and continues until the subcool degree of the cooling water at the core inlet becomes smaller than the unstable generation limit subcool degree.

[0004] In this unstable phenomenon of low-temperature two-phase flow,
Since the void reactivity of nuclear fuel also fluctuates due to the flow fluctuation, there is a problem that the stability of the core is not improved.

In order to avoid the instability of the low-temperature two-phase flow by raising the temperature of the cooling water to the highest possible temperature in a single-phase flow by delaying the start of boiling, the cooling water must be cooled at a very low nuclear heating rate. It must be heated for a long time. But,
In this method, since the circulation flow velocity in the core is very small, the cooling water in the lower plenum in the pressure vessel undergoes thermal stratification, and the low-temperature water stagnates in the lower plenum. Therefore, when most of the cooling water becomes high in temperature and starts boiling, low temperature water in the lower plenum flows into the core due to an increase in the core circulation flow rate, and the same unstable phenomenon occurs.
Further, since the cooling water is heated with a low nuclear heating amount, it takes a long time to start the reactor, and the economics associated with the operation of the reactor deteriorates significantly.

A conventional apparatus for preventing the occurrence of the unstable phenomenon of the low-temperature two-phase flow is disclosed in Japanese Unexamined Patent Publication Nos. 59-143997 and 59-217188. When the reactor is started, heat from the heat supply boiler for periodic inspection is supplied to the cooling water in the reactor pressure vessel to raise the temperature of the cooling water. This prevented the core stability from deteriorating due to the unstable flow in the phase flow state. Further, as another conventional method, as described in JP-A-60-69598, the temperature of the coolant inside the pressure vessel is increased through a heat exchanger to reduce the degree of subcooling at the core inlet to an unstable occurrence limit. After setting the range to be smaller than the subcool degree, the core stability at the time of starting the reactor was secured by starting the power increase.

[0007]

In the above prior arts, heat is supplied by equipment inside and outside the containment vessel, and none of them improves the equipment, starting method and starting characteristics of the primary cooling system of the reactor itself. . Also, since nuclear heat is not used to raise the temperature of the cooling water, a large boiler is needed to obtain the same amount of heat as nuclear heating, in addition to generating heat and transferring heat by the boiler. Or it takes a lot of time to start up the reactor, and the economic efficiency decreases. In addition, a heat exchanger and heat supply system are provided inside and outside the containment vessel or inside the pressure vessel to raise the temperature of the cooling water, requiring piping groups and control systems, and complicating the structure of the reactor, resulting in economical efficiency. There was a problem that reliability did not improve.

[0008] Even if the cooling water is heated with an extremely low nuclear heating amount for a long time in order to avoid the unstable phenomenon of the low-temperature two-phase flow, it takes a long time to start up the reactor. Therefore, there arises a problem that the economical efficiency related to the start of the nuclear reactor is not improved.

It is a primary object of the present invention to prevent a flow fluctuation and a decrease in core stability due to the occurrence of an unstable phenomenon of a low-temperature two-phase flow at the time of starting a nuclear reactor, and to provide a boiling water that enables a stable nuclear reactor startup. It is an object of the present invention to provide a method for starting a nuclear reactor and an apparatus for carrying out the method.

It is another object of the present invention to provide a method for starting a boiling water reactor which is excellent in economy and reliability by shortening the start-up time of the reactor, and an apparatus for implementing the method. .

[0011]

According to a first aspect of the present invention, there is provided a fuel cell system having a built-in reactor core made of nuclear fuel, containing cooling water therein, and generating steam therein. In the method for starting a boiling water reactor equipped with a vessel, when the temperature of the cooling water in the pressure vessel is raised, the pressure vessel
Lower inner than the rated operating pressure of the reactor and higher comb than saturation pressure that corresponds to the coolant temperature of NoboriAtsushichu, then the pressure in the pressure vessel to a saturation pressure corresponding to the coolant temperature of NoboriAtsushichu A method for starting a boiling water reactor is provided.

In order to achieve the above object, according to a second aspect of the present invention, there is provided a pressure vessel which has a built-in core made of nuclear fuel, holds cooling water inside, and generates steam inside. In the startup method of the boiling water reactor, when raising the temperature of the cooling water in the pressure vessel, the pressure in the pressure vessel is made higher than the saturation pressure of the cooling water corresponding to the temperature of the cooling water in the pressure vessel, Heat in that state, and then set the pressure in the pressure vessel to a saturation pressure corresponding to the cooling water temperature in the pressure vessel,
There is provided a method for starting a boiling water reactor, wherein cooling water is heated in that state.

Further, in order to achieve the above object, according to a third concept of the present invention, there is provided a pressure vessel which contains a reactor core made of nuclear fuel, holds cooling water inside, and generates steam inside. In the method of starting a boiling water reactor,
(A) a first procedure of heating the cooling water while maintaining the cooling water in a single-phase flow state while pressurizing the inside of the pressure vessel from outside the pressure vessel when the reactor is started; Thereafter, a second procedure for changing the cooling water in the pressure vessel from the single-phase flow state to the two-phase flow state; and (c) a third procedure for heating the cooling water in the two-phase flow state. A method for starting a boiling water reactor is provided.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

Further, according to a fourth aspect of the present invention, there is provided a pressure vessel which contains a core made of nuclear fuel, holds cooling water therein and generates steam therein, Placed outside the vessel and communicated to the pressure vessel,
A boiling water reactor comprising: a pressure adjusting means for pressurizing the inside of a pressure vessel; and a control means for operating the pressure adjusting means at the time of starting the reactor and performing the above-described starting method. Is done.

[0029]

[0030]

[0031]

[0032]

[0033]

The operation of the present invention constructed as described above is as follows. First, in the first and second concepts of the present invention,
When raising the temperature of the cooling water in the pressure vessel, the subcooling of the cooling water in the pressure vessel is performed by making the pressure in the pressure vessel higher than the saturation pressure of the cooling water corresponding to the temperature of the cooling water in the pressure vessel. As the degree of cooling increases, the boiling of cooling water is prevented,
The cooling water is heated to a high temperature in a single-phase flow state. For this reason, the gas-liquid density ratio is reduced, the density difference between the single-phase flow state and the two-phase flow state is reduced, and the flow fluctuation is reduced. Further, since the cooling water temperature itself is high, the transition from the single-phase flow state to the two-phase flow state becomes easy, and the flow fluctuation is reduced. Therefore, after that, by setting the pressure in the pressure vessel to a saturation pressure corresponding to the temperature of the cooling water in the pressure vessel, the cooling water transitions to a two-phase flow state in a state where occurrence of instability is suppressed. Thereafter or concurrently, the cooling water is heated to cause boiling, so that the rated operating temperature and pressure of the reactor can be easily obtained.

With the above-described starting method, it is possible to prevent a flow fluctuation and a decrease in core stability due to the occurrence of an unstable phenomenon of a low-temperature two-phase flow at the time of starting a boiling water reactor, and to start a stable and highly reliable reactor. Enable. In addition, the startup time of the reactor can be shortened, and the economic efficiency can be improved.

In the third concept of the present invention, the pressure in the pressure vessel is heated and heated in the first step.
The pressure in the pressure vessel becomes higher than the saturation pressure of the cooling water corresponding to the temperature of the cooling water in the pressure vessel, and the above-described action is obtained. As a result, when the two-phase flow is changed in the second procedure, ,
The occurrence of instability is suppressed. Thereafter, by heating the cooling water in a two-phase flow state in the third procedure, the subcooling degree of the cooling water is reduced to cause boiling, and the reactor rated operating temperature and pressure can be easily obtained.

In the first procedure, the pressure in the pressure vessel is controlled so that the pressure in the pressure vessel becomes higher than the saturation pressure of the cooling water corresponding to the temperature of the cooling water in the pressure vessel, and the cooling water is discharged. By maintaining the single-phase flow state, the cooling water can be reliably maintained in the single-phase flow state up to a high temperature.

In the first procedure, the heating of the cooling water is started and the pressurization in the pressure vessel is started at the same time, and the heating of the cooling water and the pressurization in the pressure vessel are simultaneously and continuously performed. Accordingly, the start-up time can be reduced as compared with the procedure in which the pressure in the pressure vessel is independently applied first.

In the second procedure, the cooling water is changed from the single-phase flow state to the two-phase flow state by controlling at least the pressure in the pressure vessel. By controlling the pressure in the pressure vessel so that the pressure in the pressure vessel approaches the saturation pressure corresponding to the cooling water temperature in the pressure vessel until a predetermined pressure is reached,
By shifting the cooling water to the two-phase flow state, the cooling water can be reliably shifted to the two-phase flow state. In this case, by keeping the pressure in the pressure vessel almost constant, or reducing the pressure in the pressure vessel to approach the saturation pressure, the cooling water is cooled before the pressure in the pressure vessel reaches the reactor rated operating pressure. The cooling water in the core can be transitioned to the two-phase flow state early, and the time required to transition to the two-phase flow state can be shortened, and the boiling in the saturated state after that can be achieved. , The startup time can be further reduced.

When controlling the pressure, the heating amount of the cooling water is reduced or the heating of the cooling water is temporarily stopped, so that the heating in the core is suppressed and the boiling does not occur. It is possible to make a transition to the two-phase flow state in a state where the reactor is prevented, and it is possible to start the reactor more stably.

In the first procedure, the critical heat output of the single-phase flow is calculated based on the measured values of the temperature of the cooling water, the pressure in the pressure vessel, and the flow rate of the core. Along with setting the withdrawal amount of the control rod for controlling the output of the core so as to be smaller than the heat output, the third procedure is based on the measured values of the temperature of the cooling water, the pressure in the pressure vessel, and the flow rate of the core. By calculating the critical heat output of the two-phase flow and setting the control rod withdrawal amount so that the core heat output is less than this critical heat output, the safe start-up of the reactor and further increase of the start-up time Shortening becomes possible.

Further, an electric heater is installed in at least one of the pressure vessel, the main steam pipe and the water supply pipe, and the cooling water is nuclear-heated in at least one of the first to third procedures. By heating the cooling water by nuclear heating of the cooling water or in at least one of the first to third procedures, and operating the water supply pump;
By heating the cooling water by the heat input by the rotation of the pump, the start-up time of the nuclear reactor is further shortened by using nuclear heating and other procedures in combination.

Further, a water supply pipe is branched and a water supply pipe for starting having a water supply stop valve for water supply is installed, and a cooling water outlet of the water supply pipe for startup is connected to a lower part of a core in a pressure vessel, and the first to the first water supply pipes are connected. 3
In at least one of the above procedures, the nuclear heating of the cooling water is carried out, and the cooling water is forcibly circulated to the core by the water supply pump through the starting water supply pipe to increase the core flow rate, thereby making the nuclear heating and the nuclear heating possible. The core stability at the time of starting the reactor is further improved by using other procedures in combination.

In the fourth and fifth concepts of the present invention, the start-up method of the present invention can be carried out by providing the pressure adjusting means or the pressure adjusting means and its control means.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a boiling water type atomic reactor in which the core is cooled by natural circulation of cooling water at least during a period from the subcritical state to before steam is discharged from the nuclear reactor at the time of starting the reactor. Can be applied to furnaces. The embodiments of the present invention described below will be described by taking a natural circulation type reactor as an example. The reactor is started from a subcritical state to a critical state, and thereafter, operations such as a temperature raising and pressure raising operation, a reactor power increase, steam supply from the reactor to the turbine, and reaching a rated reactor output are sequentially performed. The present invention particularly relates to a temperature raising operation for raising the temperature of a reactor to a rated temperature and a rated pressure during the start-up of the reactor. The temperature raising / pressurizing operation is performed in a natural circulation state.

First Embodiment A first embodiment of the present invention will be described with reference to FIGS. In FIGS. 1 and 3 to 5, a black-painted valve indicates a state in which the valve is closed, and a white valve indicates a state in which the valve is open. FIG. 2 shows a time change of the system pressure, the cooling water temperature, and the core inlet subcool degree at the time of starting the reactor.

In FIG. 1, a core 2 loaded with nuclear fuel is built in a pressure vessel 1, and the core power is controlled by moving a control rod 3 in and out. The pressure vessel 1 and the turbine 8 are connected by a main steam pipe 5 having a main steam isolation valve 4, a turbine steam stop valve 6 and a turbine steam flow regulating valve 7. A generator 25 is connected to the turbine 8. The steam after turbine driving is condensed in a condenser 11, and the condenser 11 is connected to the pressure vessel 1 by a water supply pipe 14 having a water supply pump 12 and a water supply stop valve 13. The main steam pipe 5 from the main steam isolation valve 4 to the turbine steam stop valve 6 is connected to a condenser 11.
The water supply pipe 14 on the discharge side of the water supply pump 12 and the inlet of the condenser 11 are connected to a water supply bypass stop valve 1
6 are connected by a water supply bypass flow path 15 having the same.

A water supply pipe 14 between the pressure vessel 1 and the water supply stop valve 13 has a pressure adjusting device 4 for pressurizing the inside of the pressure vessel 1.
4 are connected. The pressure adjusting device 44 includes a pressurized tank 17 connected to the water supply pipe 14 via the valve 18, a high-pressure gas tank 19 for supplying high-pressure gas to the pressurized tank 17 via the valve 20 and the flow path 21, The pressurized tank 17 is connected to a high-pressure gas tank 19, and includes a compressor 22 for discharging gas from the pressurized tank to reduce the pressure, a valve 23, and a flow path 24. The gas in the pressurized tank 17 may be directly discharged to the gas treatment system in the containment vessel to reduce the pressure. The high-pressure gas tank 19 is preferably of a replaceable cylinder type.

The water supply pipe 14 is connected to a condensate storage tank 34 on the discharge side of the water supply pump 12 via a condensate water supply / drainage passage 32 having a condensate water supply / drainage valve 33 and a condensate pump 36.

FIG. 2 shows a method of starting the above natural circulation type reactor.
This will be described with reference to FIG.

When the reactor is started after a cold shutdown, first, the main steam isolation valve 4, the turbine steam stop valve 6, the water supply stop valve 13
With the turbine bypass stop valve 10 open, for example, by opening the condensate supply / drain valve 33 and driving the condensate pump 36 to supply condensate from the condensate storage tank 34,
The reactor primary cooling water system consisting of the pressure vessel 1, the main steam pipe 5, and the water supply pipe 14 is filled with water. At this time, the pipe section of the main steam pipe 5 from the pressure vessel 1 to the steam isolation valve 4 is normally inclined upward and the level is high, so that the connection portion of the main steam pipe 5 in the pressure vessel 1 It is possible to fill up to the water level. If the level of the main steam pipe 5 is not sufficient, for example, a vent valve may be provided at the top of the pressure vessel 1, and the vent valve may be opened to perform similar water filling.

After the water filling is completed, as shown in FIG. 1, the main steam isolation valve 4, the turbine steam stop valve 6, the water supply stop valve 13
And the turbine bypass stop valve 10 is closed to isolate the reactor primary cooling system. Next, preferably, the cooling water is pump-heated and the cooling water is preliminarily circulated by opening the water supply bypass stop valve 16 and operating the water supply pump 12 to circulate the water supply to the condenser 11. Put on standby. Next, the inside of the pressure vessel 1 is pressurized to a pressure P1 by the pressure adjusting device 44 (see 1 in FIG. 2). Hereinafter, the pressure P1 in the pressure vessel 1 is appropriately referred to as “system pressure”. In the example of FIG. 2, the system pressure P1 is 0.5 MPa. Also, the system pressure P1
Assuming that the saturation temperature corresponding to T1 is T1, P1 is 0.5MP
In a, T1 is 151 ° C.

After pressurizing the reactor primary cooling water as described above, the control rod 3 is pulled out and the cooling water is heated by nuclear heat generated in the reactor core 2 (see 1 in FIG. 2). here,
As described above, the system pressure P1 is 0.5 PMa, the corresponding saturation temperature T1 is 151 ° C., and even when the cooling water temperature T2 rises to 100 ° C. due to the nuclear heating in the core 2, the cooling of the inlet of the core 2 is performed. The water subcooling degree is 50 ° C. or higher, and the cooling water remains in a single-phase flow state.

In the above procedure, the cooling water is further subjected to nuclear heating to increase the cooling water temperature T2 to 200 ° C. (see 1 in FIG. 2). In this process, the system pressure P1 is always made higher than the saturation pressure P2 corresponding to the cooling water temperature T2 by the pressure adjusting device 44 (P1> P2), and the system pressure P1 is set to a value satisfying the following condition. The cooling water is heated to a high-temperature high-pressure state with a single-phase flow.

T2 <T1−Tb (1) Here, Tb is the maximum subcooling at the start of the boiling core, which depends on the cooling water temperature, the system pressure, the flow rate, the nuclear heating amount, and the like. In the example of FIG. 2, when the cooling water temperature T2 is 150 ° C., the system pressure P1 is set to 1.6 MPa (corresponding saturation temperature 200 ° C.).
When the cooling water temperature T2 is 200 ° C., the system pressure P1
Is set to 4.1 MPa (corresponding saturation temperature 250 ° C.), and the core inlet subcool degree is set to 50 ° C. or more.

By raising the cooling water temperature T2 as described above, a state in which the occurrence of an unstable phenomenon is suppressed even when the state transits to the two-phase flow state. That is, as the cooling water temperature increases, the gas-liquid density ratio decreases, the density difference between the single-phase flow state and the two-phase flow state decreases, and the flow fluctuation decreases. Further, since the cooling water temperature itself is high, the transition from the single-phase flow state to the two-phase flow state becomes easy, and the flow fluctuation is reduced.

After the cooling water temperature T2 is increased as described above, the pressure P1 in the pressure vessel 1 is gradually approached to the saturation pressure P2 corresponding to the cooling water temperature T2 by the pressure adjusting device 44 (FIG. 2).
1-). In the example of FIG. 2, the control rod is continuously pulled out, the cooling water is heated by nuclear heat generated in the core 2, and when the cooling water temperature T2 reaches the rated operation temperature (that is, the cooling water temperature T2 Corresponding saturation pressure P2
At the time when the pressure reaches the rated operating pressure), the system pressure is adjusted by the pressure regulator 44 so that the system pressure P1 almost reaches the rated operating pressure. In this process, the degree of subcooling at the core inlet decreases, and the cooling water in the core 2 transitions to a two-phase flow state through a state in which the gas-liquid density ratio is small at a high temperature and the unstable phenomenon is suppressed. The point in time when the cooling water transitions to the two-phase flow state is a point in time when the system pressure reaches a predetermined pressure equal to or lower than the rated operating pressure, and corresponds to a point in time when the following conditions are almost satisfied.

P1> P2, T1 <T2 + Ts (2) Here, Ts is the maximum subcool degree in the stable boiling region depending on the cooling water temperature, system pressure, flow rate, nuclear heating amount, and the like.

In this process (1- in FIG. 2),
While the pressurization by the pressure adjusting device 44 is released, as shown in FIG. 3, the main steam isolation valve 4 and the turbine bypass stop valve 10 are opened to release the pressurization of the cooling water, and a water level is formed in the pressure vessel 1. By doing so, it is possible to smoothly transition to the rated operation state. At this time, the condensate water supply / drainage valve 33 and the water supply stop valve 13 are opened and closed so that the water level in the pressure vessel 1 becomes an appropriate water level.

"Release the pressurization by the pressure adjusting device 44" means that the valve 23 is opened in FIG.
Is driven to discharge gas from the pressurized tank 17. When a configuration is provided in which the gas in the pressurized tank 17 is directly discharged to the gas treatment system in the containment vessel to reduce the pressure, That is. This pressure control corresponds to reducing the difference between the system pressure P1 indicated by the solid line and the saturation pressure P2 corresponding to the coolant temperature T2 indicated by the broken line in the characteristic diagram of the system pressure in FIG.

Next, as the system pressure and the cooling water temperature reach the rated operating pressure and temperature, as shown in FIG. 4, the water supply stop valve 13 is opened to start supplying water to the pressure vessel 1, and FIG. As shown, the turbine steam stop valve 6 and the turbine steam flow control valve 7 are opened, the turbine bypass stop valve 10 is closed, and the rotation of the turbine 8 is started. The feedwater flow rate at this time is determined from the nuclear heating amount of the reactor core 2 and the heat balance between the circulating water and the feedwater, and is adjusted by the feedwater stop valve 13 and the feedwater bypass stop valve 16.

According to the above-described starting method, when the cooling water is at a low temperature, the cooling water is heated in a single-phase flow state. When the cooling water is heated to a high temperature, the cooling water is changed to a two-phase flow state. The flow instability of the phase flow can be avoided. Further, since the inside of the pressure vessel 1 is pressurized and the cooling water is heated, the time required for raising the temperature of the cooling water in the single-phase flow state can be reduced, and the startup time can be reduced.

According to this embodiment, it is possible to prevent a flow fluctuation and a decrease in core stability due to the occurrence of a low-temperature two-phase flow instability at the time of startup of a natural circulation type reactor. This has the effect of enabling startup. Further, the start-up time of the reactor can be shortened, and the economy can be improved.

Modification A modification of the first embodiment will be described with reference to FIG. In the first embodiment, at the start of heating the primary cooling water of the reactor,
Although the system pressure was previously increased by the pressure adjusting device 44 (1 in FIG. 2), in the example of FIG. 6, the system pressure was gradually and continuously increased with the start of the cooling water heating (in FIG. 6). 2
-), The cooling water is heated to a high temperature with a single-phase flow.
According to the present embodiment, the procedure of only pressurization in the first embodiment (1 in FIG. 2) can be omitted, and thus there is an effect that the start-up time of the reactor can be further reduced.

Second Embodiment A second embodiment of the present invention will be described with reference to FIG. In the first embodiment, in the start-up procedure of the natural circulation reactor, the cooling water is heated in a single-phase flow to a high-temperature and high-pressure state by nuclear heating, the cooling water temperature T2 rises, and the gas-liquid density ratio decreases sufficiently. Then, after reaching the state in which the occurrence of the unstable phenomenon is suppressed, the pressure regulator 44 controls the pressure P1 in the pressure vessel 1 to gradually approach the saturation pressure P2 corresponding to the cooling water temperature T2. In the example of FIG. 7, when the system pressure P1 is gradually approached to the saturation pressure P2, the system pressure is almost constant or gradually approached to the saturation pressure P2 as slightly increasing (see 3- in FIG. 7).
As a result, before the system pressure P1 reaches the rated operating pressure,
Since the cooling water can be surely brought into the saturated state, the cooling water in the core 2 can be shifted to the two-phase flow state at an early stage. The point in time when the cooling water transitions to the two-phase flow state corresponds to the point in time when the system pressure satisfies approximately the following condition that is equal to or lower than the rated operating pressure.

P1 = P2, T1 <T2 + Ts (3) where Ts is the maximum subcool degree in the stable boiling region depending on the cooling water temperature, system pressure, flow rate, nuclear heating amount, and the like.

In the control of the pressure, as in the first embodiment, the pressurization by the pressure adjusting device 44 is released, and the main steam isolation valve 4 and the turbine bypass stop valve 10 are switched as shown in FIG. By opening and releasing the pressurization in the pressure vessel 1 and forming a water level in the pressure vessel 1, it is possible to smoothly shift to the rated operation state. At this time, the condensate water supply / drainage valve 33 and the water supply stop valve 13 are opened and closed so that the water level in the pressure vessel 1 becomes an appropriate water level.

Thereafter, the control rod 3 is continuously pulled out, and the cooling water is heated in a two-phase flow state by nuclear heat generated in the reactor core 2 to obtain the rated operating temperature and pressure of the reactor (3--3 in FIG. 7).
reference). Subsequent procedures are the same as in the first embodiment.

Therefore, in this embodiment, the core 2
Since the cooling water in the inside can be changed to the two-phase flow state, boiling occurs in the two-phase flow state and heat transfer in the core is improved, so that the amount of nuclear heating can be increased, and the system pressure P1
The time required for the cooling water to rise until the pressure reaches the rated operating pressure can be shortened (see 3- in FIG. 7). Also, in FIG.
The time required for the cooling water core inlet subcool degree to pass between the boiling start maximum subcool degree Tb and the stable boiling region maximum subcooled Ts is also reduced. Therefore, the economics involved in starting the reactor are improved, and the flow instability of the low-temperature two-phase flow is more easily avoided than in the first embodiment, and the reliability related to starting the reactor is improved.

According to the present embodiment, in addition to the effects of the first embodiment, there is an effect of enabling a more stable start-up of the reactor and an effect of further shortening the reactor start-up time.

Modification A modification of the second embodiment will be described with reference to FIG. In the embodiment of FIG. 7, when the system pressure P1 is gradually approached to the saturation pressure P2, the system pressure is almost constant or slightly increased (see 3- in FIG. 7). That is, the pressure is asymptotically approached to the saturation pressure P2 while being reduced (see 4- in FIG. 8). As a result, the cooling water can be brought into the saturated state in a shorter time than in the case of FIG. 7, so that the cooling water in the core can be changed to the two-phase flow state earlier, and the system pressure P1 can be reduced to the rated value. The time for raising the temperature of the cooling water until the operating pressure is reached can be further shortened (4-- in FIG. 8).
reference). Further, the time required for the cooling water core inlet subcool degree to pass between the boiling start maximum subcool degree Tb and the stable boiling region maximum subcooled Ts is further reduced (see 4- in FIG. 8). Therefore, according to the present embodiment, the economy related to the start of the nuclear reactor is improved, and the flow instability of the low-temperature two-phase flow can be more easily avoided than in the case of FIG.
The reliability related to the start of the reactor is improved.

Third Embodiment A third embodiment of the present invention will be described with reference to FIG. In the embodiment shown in FIG. 8, in the start-up procedure of the natural circulation reactor, the control rod 3 is continuously pulled out in the process 4 in FIG. 8, and the pressure adjusting device 44 is used while allowing the cooling water temperature T2 to rise. The system pressure P1 has been reduced. In the example of FIG. 9, the control rod 3 is once inserted into the core 2, the output of the core 2 is reduced, and the system pressure P <b> 1 is reduced by the pressure adjusting device 44 (4 in FIG. 9). As a result, when the system pressure P1 is reduced, the core heating in the core 2 is suppressed and boiling does not occur. Therefore, in a state in which the occurrence of the unstable phenomenon is completely prevented, the core inlet subcooling degree is set to be equal to or less than the stable boiling region maximum subcooled Ts. Can be reduced. System pressure P1 is saturated pressure P
After asymptotically approaching 2 and satisfying the above expression (3), the cooling water is induced to boil under reduced pressure. Then, the control rod 3 is pulled out again and the core is heated in the core 2 so that the cooling water is in a two-phase flow state. The temperature can be raised (4- in FIG. 9). In the example of FIG. 9, since the core 2 does not boil when the cooling water core inlet subcool degree passes between the boiling start maximum subcool degree Tb and the stable boiling region maximum subcool degree Ts, the flow unstable phenomenon occurs. Is completely prevented.

The suppression of nuclear heating during depressurization is achieved by the control rod 3
May be partially inserted to reduce the nuclear heating amount of the cooling water, or the nuclear heating may be temporarily stopped. FIG. 9 shows the latter example, in which the temperature of the cooling water is substantially constant.

According to the present embodiment, in addition to the effect of the second embodiment, there is an effect that enables a more stable start-up of the nuclear reactor.

Modifications Several modifications relating to the procedure for raising the temperature of the cooling water to a single-phase flow will be described with reference to FIGS. FIG.
When the system pressure is previously increased by the pressure adjusting device 44 at the start of cooling water heating, the system pressure P1 is directly increased to a level that satisfies the above equation (1) (5 in FIG. 10).
Thereafter, the pressurization by the pressure adjusting device 44 is stopped until the cooling water rises to the target temperature. As a result, the system pressure naturally rises as the saturated steam pressure increases as the cooling water temperature rises (5--5 in FIG. 10).
reference). The subsequent procedure is almost the same as in the third embodiment. FIG. 11 shows that, in the embodiment of FIG. 10, after the system pressure P1 is increased, until the cooling water rises to the target temperature,
The pressurization by the pressure adjusting device 44 is released to suppress the increase in the saturated steam pressure and keep the system pressure constant (see 6 in FIG. 11). Further, FIG. 12 shows that the system pressure is continuously kept constant even in the process of changing the cooling water from the single-phase flow to the two-phase flow (see 7-7 in FIG. 12).
11) and 3- in the example of FIG.
This corresponds to the combination with According to these examples,
The same effect as that of the second or third embodiment can be obtained, and the necessary pressure is obtained in advance at the time of starting the heating of the cooling water, so that the subsequent pressure control becomes easy and the starting procedure is simplified. There is.

Fourth Embodiment A fourth embodiment of the present invention will be described with reference to FIG. The natural circulation reactor according to the present embodiment further includes an optimum valve control amount and a control rod insertion amount based on the measured values of the state quantities of the respective parts of the reactor, in addition to the natural circulation reactor described in the first embodiment. The main steam isolation valve 4, turbine steam stop valve 6, turbine bypass stop valve 10, water supply stop valve 13, water supply bypass stop valve 16,
Condensate supply / drain valve 33, turbine steam flow control valve 7, valve 1
8, an arithmetic and control unit 26 for controlling the opening and closing of the valve 20 and the valve 23 and the control rod driving mechanism 27 is provided. As the state quantities of each part of the reactor, the pressure in the pressure vessel 1 is measured by a pressure gauge 28, the water level is measured by a water level gauge 29, and the water temperature is measured by a water temperature gauge 43, and the cooling water temperature and the circulation flow rate at the inlet of the reactor core 2 are measured by a flow meter 4.
2 and the water thermometer 30, and the output of the reactor core 2 is measured by the neutron detector 31.

Hereinafter, as an example of the reactor start-up method according to the present embodiment using the arithmetic and control unit 26, the start-up method shown in FIG. 2 of the first embodiment will be described.

When the reactor is started after the cold shutdown, first, the reactor primary cooling water system including the pressure vessel 1, the main steam pipe 5 and the water supply pipe 14 is filled with water, and then the main steam isolation valve 4, the turbine steam stop valve 6 and the like. Then, the water supply stop valve 13 and the turbine bypass stop valve 10 are closed. In addition, the water supply bypass stop valve 16
Is opened and the water supply pump 12 is operated to circulate the water supply to the condenser 11. Next, the valve 20 is opened by the arithmetic and control unit 26, and while the opening degree of the valve 20 is adjusted according to the pressure in the pressure vessel 1 measured by the pressure gauge 28, the pressure in the pressure vessel 1 is adjusted by the pressure adjusting device 44. Increase P1. In the example of FIG. 2, the system pressure P1 is increased to 0.5 MPa.

Next, the operation controller 26 controls the pressure gauge 2.
8. The pressure in the pressure vessel 1, the output of the core 2, the temperature of the cooling water, the cooling water temperature at the inlet of the core 2 (core cooling subcooling degree) with the neutron detector 31, the water thermometer 43, the water thermometer 30, and the flow meter 42 While monitoring the flow rate and the flow rate, the control rod 3 is pulled out and the cooling water is heated by nuclear heat generated in the core 2.
At this time, the optimal nuclear heating amount is measured by the pressure gauge 28 and the neutron detector 3.
1. The arithmetic controller 26 calculates from the measured values of the water thermometer 43, the water thermometer 30, and the flow meter 42, and sends a control signal to the control rod drive mechanism 27 to set the amount of pull-out of the control rod 3. Here, the withdrawal amount of the control rod 3 is set so that the core heat output is smaller than the critical heat output of the single-phase flow calculated from the cooling water temperature, the system pressure, and the core flow rate. At this time, since the cooling water is in a pressurized state, the subcooling degree is larger than the maximum core entrance subcooling degree Tb at the start of boiling, and remains in a single-phase flow state.

Next, as the cooling water temperature exceeds 100 ° C. and rises, the measured values of the pressure gauge 29, the water thermometer 43, and the water thermometer 30 monitored by the arithmetic and control unit 26 are:
The control signal is sent from the arithmetic and control unit 26 to the pressure adjusting device 44 so that the system pressure P1 is always higher than the saturation pressure of the cooling water and the core inlet subcool degree becomes larger than the maximum core inlet subcool degree Tb at which boiling starts. Keep state. After the cooling water temperature rises and reaches a temperature at which the occurrence of the unstable phenomenon of the low-temperature two-phase flow is suppressed (about 200 ° C. in the example of FIG. 5), the arithmetic controller 26 reduces the system pressure P1 to the cooling water temperature. A control signal for releasing the pressurized state is sent to the pressure adjusting device 44 so as to asymptotically approach the saturation pressure corresponding to the main steam isolation valve 4 and the turbine bypass stop valve while monitoring the measured values of the coolant temperature and the pressure. A control signal for adjusting the opening degree of No. 10 is sent.
As a result, high-temperature cooling water flows into a part of the main steam pipe 5 and into the turbine bypass flow path 9, evaporates to generate a vapor phase, and a water level is formed in the pressure vessel 1. Further, the core inlet subcool degree decreases to become smaller than the maximum core inlet subcool degree Ts in the stable boiling region, and the cooling water is in a high temperature and low subcool state, so that boiling easily occurs. In this process, the arithmetic controller 26 controls the condensate water supply / drainage valve 33 and the water supply stop valve 13 based on the measured value of the water level gauge 29 so that the water level in the pressure vessel 1 becomes an appropriate water level. A signal is sent to adjust the water level in the pressure vessel 1. By the above procedure, the boiling of the cooling water occurs in the core 2, and the cooling water in the core 2 transitions from the single-phase flow state to the two-phase flow state.

At this time, the optimum amount of nuclear heating was measured with a pressure gauge 2
8. The arithmetic controller 26 calculates from the measured values of the neutron detector 31, the water thermometer 43, the water thermometer 30, and the flow meter 42, and sends a control signal to the control rod drive mechanism 27 to set the amount of pull-out of the control rod 3. . Here, the withdrawal amount of the control rod 3 is set so that the core heat output is smaller than the critical heat output of the two-phase flow calculated from the cooling water temperature, the system pressure, and the core flow rate.

As the system pressure and temperature asymptotically approach the rated operating pressure and temperature, the water supply stop valve 13 is opened by the operation controller 26 to start water supply into the pressure vessel 1, and the operation controller 26 controls the system pressure. When the cooling water temperature reaches the rated operating pressure and temperature, the turbine steam stop valve 6 and the turbine steam flow regulating valve 7 are opened, the turbine bypass stop valve 10 is closed, and the rotation of the turbine 8 is started. At this time, the operation controller 26 controls the water supply stop valve 1 so that the pressure, temperature and water level in the pressure vessel 1 are constant.
3 and the opening degree of the turbine steam flow control valve 7 is adjusted.

According to this embodiment, in addition to the effects of the first, second, and third embodiments, the effect of simplifying the start-up procedure at the time of starting the natural circulation reactor, and the effects of pressure, water temperature, This has the effect of improving the controllability of the water level in the pressure vessel.

Fifth Embodiment A fifth embodiment of the present invention will be described with reference to FIG. The natural circulation type nuclear reactor of this embodiment further includes a heater 35 for electrically heating the lower plenum below the reactor core 2 in the pressure vessel 1 in addition to the configuration of the first embodiment.

When the reactor is started after the cold shutdown, the heater 3
The cooling water in the pressure vessel 1 is heated to a water temperature at which the low-temperature two-phase flow instability does not occur using the auxiliary 5. Heater 35
In the example of FIG. 2, the auxiliary heating by
, 1-, 1-, or a part of them, for example, the procedure of 1-, 1- after pressurization. To obtain a stable high-temperature two-phase flow state. Then, after the cooling water temperature is increased, the control rod 3 is continuously pulled out and the cooling water is heated in a two-phase flow state by nuclear heating to obtain a predetermined turbine operating steam temperature and pressure. The flow control valve 7 is opened, the turbine bypass stop valve 10 is closed, and the rotation of the turbine is started.

According to this embodiment, in addition to the effect of the first embodiment, there is an effect that the start-up time of the reactor can be shortened.

Sixth Embodiment A sixth embodiment of the present invention will be described with reference to FIG. FIG.
, A black valve indicates a state where the valve is closed, and a white valve indicates a state where the valve is open. In the present embodiment, when the reactor is started after a cold shutdown, the main steam isolation valve 4 and the turbine bypass stop valve 10 are opened, and the turbine steam stop valve 6 is opened.
Close. Operate the water supply pump 12 to supply water to the water supply pipe 1
4, pressure vessel 1, main steam pipe 5, turbine bypass flow path 9
Circulates. At this time, the cooling water is heated by the heat input to the cooling water by the rotation of the pump, and the cooling water in the pressure vessel 1 is not subjected to the low-temperature two-phase flow instability phenomenon by using the cooling water heating by the heat input. Heat to water temperature. That is, in the example of FIG. 2, the heating of the cooling water by the heat input of the pump rotation is used in combination with the entire process of the procedures 1, 1, 1, 1, or a part thereof, for example, the procedure of 1, 1- To obtain a stable high-temperature two-phase flow state. Then, after the cooling water temperature is increased, the control rod 3 is continuously pulled out and the cooling water is heated in a two-phase flow state by nuclear heating to obtain a predetermined turbine operating steam temperature and pressure. The flow control valve 7 is opened, the turbine bypass stop valve 10 is closed, and the rotation of the turbine is started.

According to this embodiment, in addition to the effect of the first embodiment, there is an effect that the start-up time of the reactor can be shortened.

Seventh Embodiment A seventh embodiment of the present invention will be described with reference to FIG. FIG.
, A black valve indicates a state where the valve is closed, and a white valve indicates a state where the valve is open. The natural circulation type nuclear reactor of the present embodiment has a water supply pipe 1 in addition to the configuration of the first embodiment shown in FIG.
4 is provided with a starting water supply pipe 37, and the starting water supply pipe 3 is provided.
A startup water supply stop valve 38 is provided at 7, and a cooling water outlet of the startup water supply pipe 37 is connected to a lower plenum below the core 2 in the pressure vessel 1. When the reactor is started after a cold shutdown, the water supply stop valve 13 is closed, the valve 38 is opened, and the water supply pump 12 is operated to supply water to the reactor core 2. As a result, the cooling water can be circulated to the reactor core 2 by forced circulation, similarly to the existing boiling water reactor, and the cooling water in the pressure vessel 1 is used together with the forced circulation by the starting water supply pipe 37. Is heated to a water temperature at which low temperature two-phase flow instability does not occur. That is, FIG.
In the above example, a stable high-temperature two-phase flow state is obtained by using the forced circulation in combination with the entire process of steps 1-, 1-, 1- and 1- or a part thereof, for example, the steps 1- and 1-. . The circulation flow rate can be adjusted by the water supply bypass stop 16. After obtaining the predetermined reactor rated operation steam temperature and pressure, the turbine steam stop valve 6 and the turbine steam flow regulating valve 7 are opened, the turbine bypass stop valve 10 is closed, and the rotation of the turbine is started.

According to the present embodiment, in addition to the effects of the first embodiment, there is an effect that the core stability can be improved as in the current forced circulation reactor.

Another Embodiment An eighth embodiment of the present invention will be described with reference to FIG. FIG.
, A black valve indicates a state where the valve is closed, and a white valve indicates a state where the valve is open. The natural circulation type nuclear reactor of the present embodiment is the same as the natural circulation type reactor shown in the first embodiment, except that the pressure adjusting means is connected to the reactor primary cooling water system, the flow path 42, the valve 39, the constant pressure pump 40, Cooling water tank 4
The primary cooling of the reactor consisting of the pressure vessel 1, the main steam pipe 5 and the feed water pipe 14 at the time of start-up after cold shutdown of the reactor using the pressure vessel 1 and the watertight test system 44 A of the reactor primary cooling water system consisting of Pressurize the water system.

According to the present embodiment, since the equipment for the periodic inspection is used, the equipment for starting can be simplified, and the simplification of the equipment has the effect of improving the economy and reliability. is there.

A ninth embodiment of the present invention will be described with reference to FIG. In this embodiment, in the natural circulation type reactor shown in the first to eighth embodiments, the structure of the pressure adjusting device is the same as that of the pressurizer of the existing pressurized water reactor. That is, as shown in FIG. 18, the pressurizer of the pressurized water reactor has a structure in which a pressurized tank 45 having a heater 46 therein is connected to the primary cooling water system of the reactor via a valve 47. In the example, this is used as the pressure adjusting device 44B. In the present embodiment, during the pressurization process at the start of reactor startup (corresponding to 1- and 1- in the example of FIG. 2),
The heater 46 is energized to heat the water and steam in the pressurized tank 45 to pressurize it. In the process of gradually approaching the system pressure P1 to the saturation pressure corresponding to the cooling water temperature T2 (corresponding to 1 in the example of FIG. 2), the heating by the heater 46 is stopped, or the pressurized tank is opened by a sprinkler (not shown). The pressure is adjusted by sprinkling water in 45 and lowering the temperature.

According to the present embodiment, the equipment related to the pressure adjustment can be simplified, so that the reliability of starting the reactor is improved.

A tenth embodiment of the present invention will be described with reference to FIG. In the present embodiment, in the natural circulation type reactor shown in the first to eighth embodiments, the pressure adjusting device 44C is configured by the high-pressure gas tank 48, the valve 49, and the flow path 50, and the reactor primary cooling water system, for example, Connect to pressure vessel 1. In the present embodiment, during the pressurization process at the start of the reactor startup (corresponding to 1- and 1- in the example of FIG. 2), the high-pressure gas is supplied from the high-pressure gas tank 48 through the valve 49 and the flow path 50 to the pressure vessel 1. The reactor is pressurized by supplying it to the primary cooling water system. In the process of asymptotically setting the system pressure P1 to the saturation pressure corresponding to the cooling water temperature T2 (corresponding to 1 in the example of FIG. 2), the high-pressure gas in the reactor primary cooling water system is removed by the main steam isolation valve 4, Deaeration system 51 via Turben bypass stop valve 10
Adjust the pressure by pulling in. Or pressure vessel 1
If there is a vent, it may be exhausted from the vent.

According to the present embodiment, the equipment related to the pressure adjustment can be simplified, so that the reliability of starting the reactor is improved.

An eleventh embodiment of the present invention will be described with reference to FIG. This embodiment is different from the pressure adjusting device 44C shown in FIG.
Is connected to the main steam pipe 5 between the pressure vessel 1 and the main steam isolation valve 4. According to this embodiment, effects similar to those of the tenth embodiment can be obtained.

[0097]

As described above, according to the present invention,
Prevent flow fluctuations and decrease in core stability due to the instability of low-temperature two-phase flow when starting a natural circulation reactor,
This has the effect of enabling stable start-up of the reactor. Also,
This has the effect of shortening the reactor start-up time and improving economy and reliability.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an entire configuration of a natural circulation reactor for carrying out a start-up method according to a first embodiment of the present invention and a procedure of the start-up method.

FIG. 2 is a diagram showing a time change of a reactor system pressure, a temperature, and a core inlet subcool degree in a startup method according to a first embodiment of the present invention.

FIG. 3 is a system diagram similar to FIG. 1, showing another procedure of a starting method according to the first embodiment of the present invention.

FIG. 4 is a system diagram similar to FIG. 1, showing still another procedure of the activation method according to the first embodiment of the present invention.

FIG. 5 is a system diagram similar to FIG. 1, showing still another procedure of the activation method according to the first embodiment of the present invention.

FIG. 6 is a diagram showing changes over time in pressure, temperature, and core inlet subcool degree of a reactor system in a startup method according to a modification of the first embodiment of the present invention.

FIG. 7 is a diagram showing a temporal change of a pressure, a temperature, and a core inlet subcool degree of a reactor system in a startup method according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a temporal change of a pressure, a temperature, and a core inlet subcool degree of a reactor system in a startup method according to a modification of the second embodiment of the present invention.

FIG. 9 is a diagram showing a temporal change of a reactor system pressure, a temperature and a core inlet subcool degree in a startup method according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a temporal change of a reactor system pressure, a temperature, and a core inlet subcool degree in a startup method according to another modified example of the present invention.

FIG. 11 is a diagram showing a temporal change of a reactor system pressure, a temperature and a core inlet subcool degree in a start-up method according to still another modified example of the present invention.

FIG. 12 is a diagram showing a temporal change of a reactor system pressure, a temperature, and a core inlet subcool degree in a start-up method according to still another modified example of the present invention.

FIG. 13 is a system diagram showing an entire configuration of a natural circulation reactor for carrying out a starting method according to a fourth embodiment of the present invention and a procedure of the starting method.

FIG. 14 is a system diagram showing an entire configuration of a natural circulation reactor for carrying out a starting method according to a fifth embodiment of the present invention and a procedure of the starting method.

FIG. 15 is a system diagram showing an overall configuration of a natural circulation reactor for carrying out a startup method according to a sixth embodiment of the present invention and a procedure of the startup method.

FIG. 16 is a system diagram showing an overall configuration of a natural circulation reactor for carrying out a start-up method according to a seventh embodiment of the present invention and a procedure of the start-up method.

FIG. 17 is a system diagram showing an entire configuration of a natural circulation reactor for carrying out a start-up method according to an eighth embodiment of the present invention and a procedure of the start-up method.

FIG. 18 is a system diagram showing an entire configuration of a natural circulation reactor for carrying out a startup method modified from the ninth embodiment of the present invention and a procedure of the startup method.

FIG. 19 is a system diagram showing an entire configuration of a natural circulation reactor for carrying out a start-up method according to a tenth embodiment of the present invention and a procedure of the start-up method.

FIG. 20 is a system diagram showing an overall configuration of a natural circulation reactor for carrying out a start-up method according to an eleventh embodiment of the present invention and a procedure of the start-up method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure vessel 2 Core 3 Control rod 4 Main steam isolation valve 5 Main steam pipe 6 Turbine steam stop valve 7 Turbine steam flow control valve 8 Turbine 9 Turbine bypass flow path 10 Turbine bypass stop valve 11 Condenser 12 Water supply pump 13 Water supply stop Valve 14 Water supply pipe 15 Water supply bypass flow path 16 Water supply bypass stop valve 17 Pressurized tank 19 High pressure gas tank 26 Operation controller 27 Control rod drive mechanism 28 Pressure gauge 29 Water level gauge 30 Water temperature gauge 31 Neutron detector 32 Condensed water supply / drainage flow path 33 condensate water supply / drain valve 34 condensate water storage tank 35 heater 36 condensate water supply / drainage pump 37 starting water supply pipe 38 starting water supply stop valve 39 valve 40 constant pressure pump 41 cooling water tank 42 flow path 44 pressure regulator

──────────────────────────────────────────────────の Continued on front page (72) Inventor Shigeto Murata 1168 Moriyama-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Energy Research Laboratory (72) Inventor Yoshiyuki Kataoka 1168 Moriyama-machi, Hitachi City, Ibaraki Prefecture Energy, Hitachi, Ltd. In the laboratory (72) Inventor Shunji Nakao 1168 Moriyama-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd.Energy Research Laboratory Co., Ltd. (72) Inventor Shoichiro Kinoshita 3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. (56) References JP-A-63-180896 (JP, A) JP-A-56-180896 (JP, A) JP-A-56-26297 (JP, A) JP-A-57-84394 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G21D 3/00 G21D 3/08

Claims (4)

(57) [Claims] 1. A method for starting a boiling water reactor having a reactor core containing a nuclear fuel and having a pressure vessel for holding cooling water therein and generating steam therein, wherein the cooling water in the pressure vessel is raised. When heating , atoms in the pressure vessel
High comb than saturation pressure that corresponds to the coolant temperature of the low and NoboriAtsushichu than the rated operating pressure of the furnace, to the saturation pressure then the corresponding pressure in the pressure vessel to the cooling water temperature of NoboriAtsushichu Characteristic method of starting a boiling water reactor. 2. A method for starting a boiling water reactor having a pressure vessel which contains a reactor core made of nuclear fuel, has a cooling water inside, and generates steam therein, wherein the cooling water in the pressure vessel is raised. When heating, the pressure in the pressure vessel is made higher than the saturation pressure of the cooling water corresponding to the temperature of the cooling water in the pressure vessel, and heating is performed in that state, and then the pressure in the pressure vessel is cooled in the pressure vessel. A method for starting a boiling water reactor, comprising setting a saturation pressure corresponding to a water temperature and heating cooling water in that state. 3. A method for starting a boiling water reactor having a built-in reactor core made of nuclear fuel and having a pressure vessel for holding cooling water therein and generating steam therein, comprising: (a) when starting up the reactor; A first step of heating the cooling water while maintaining the single-phase flow while cooling the inside of the pressure vessel from outside the pressure vessel; and (b) cooling the water inside the pressure vessel after the first procedure. (C) a third step of heating the cooling water in the two-phase flow state; and a boiling water type comprising: How to start the reactor. 4. A pressure vessel having a core made of nuclear fuel therein, having a cooling water therein and generating steam therein,
The pressure adjusting means which is arranged outside the pressure vessel and is connected to the pressure vessel to pressurize the inside of the pressure vessel, and the pressure adjusting means is operated at the time of starting the nuclear reactor, and the pressure adjusting means is operated .
And a control means for performing a start-up method .