JPH0437393B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a purification device for a reactor cooling system of a nuclear power plant, particularly a boiling water nuclear power plant.

[Technical background of the invention and its problems] In a boiling water nuclear power plant, a condensate storage tank is provided and is used for regulating surplus water and as a water source for a cooling system. This will be explained below with reference to FIG.

FIG. 1 is a schematic system diagram showing the flow of water around a conventional nuclear reactor.

A reactor containment vessel 2 is provided surrounding a reactor pressure vessel 1 having a plurality of control rod drive devices 26 provided at its bottom. A partition wall 3 is provided that divides the inside of the reactor containment vessel 2 into an upper reactor well 4a and a lower dry well 4b. Reactor containment vessel 2
A pressure suppression pool 5 is provided below the outside, and a reactor building 6 is provided surrounding it.
A turbine 7 and a main condenser 8 are provided on the outside of the reactor building 6, and a valve 10 is connected to the reactor pressure vessel 1.
They are connected by main steam piping 9 via a, 10b, and 10c. A pipe 11 is provided from upstream of the valve 10b via a valve 12, bypassing the turbine 7, and connecting to the main condenser 8. This main condenser (8) communicates with the turbine 7, and furthermore, the condensate pump 1
3, condensate purification device 14, feed water heaters 15, 17,
Boost pump 16a, water supply pump 16b and valve 1
8 and is connected to the reactor pressure vessel 1 by a water supply 19 . Condensate storage tank 2 with built-in condensate
0 is communicated with the reactor pressure vessel 1 via a water supply pipe 19 and a pipe 21, and is also communicated with the main condenser 8 via a make-up water pump 22 and a pipe 23. This condensate storage tank 20 includes a control rod drive device 26
, control rod drive pump 24, and water pressure control unit 2
The return pipe 27b is also connected via the water pressure control unit 25 to a waste treatment device 28 having a drain pipe to the pit 29, and furthermore, the pipe 30 connects the condensate storage tank 20. It is connected to the. The reactor pressure vessel 1 is provided with a recirculation system in the reactor containment vessel 2, which includes a recirculation pump 31 and piping 32 for forcibly circulating the reactor core flow rate. The mechanical seal portion of the recirculation pump 31 is provided with a pipe 33 that communicates with the waste treatment device 28 .

On the other hand, the pressure suppression pool 5 is connected to the reactor pressure vessel 1 and the piping 3 via an emergency cooling pump 34 and a valve 35.
6 and also connected by an emergency cooling pump 34
A pipe 37 is connected to the suction side pipe in communication with the condensate storage tank 20 to constitute an emergency core cooling system. In addition, a fuel storage pool 38 and a skimmer surge tank 39 connected to the fuel storage pool 38 are provided in the upper part of the reactor building 6, and a valve 40, a pump 41, a heat exchanger 42, a purification device 43, and a reactor well 4a are provided.
A fuel storage pool cooling and purification system is constructed by a pipe 44 that connects the fuel storage pool. Piping 44 communicating with skimmer surge tank 39 and reactor well 4a
is connected to the condenser 8 by a pipe 44'.

Next, the operation will be explained with respect to the schematic system diagram shown in FIG. 1 showing the flow of water around the nuclear reactor. Steam generated in the reactor pressure vessel 1 is sent to the turbine 7 through the main steam pipe 9, causing the turbine 7 to rotate.
It is condensed in the main condenser 8. In some cases, the main condenser 8
It is condensed in The pressure of the condensed water is increased by the condensate pump 13 and purified by the condensate purification device 14, and then a part of the water passes through the pipe 21 and is transferred to the condensate storage tank 20.
The remaining water is heated by the feed water heaters 15 and 17, pressurized by the pressure boost pump 16a and the feed water pump 16b, and returned to the reactor pressure vessel 1 through the water feed pipe 19. The control rod drive device 26 provided at the bottom of the reactor pressure vessel 1 is cooled by water in the condensate storage tank 20 during normal reactor operation. This water is
It flows into the reactor pressure vessel 1 through the control rod drive device 26 . During a reactor scram, the waste water from the control rod drive device 26 is transferred to the waste treatment device 28.
sent to. Furthermore, a staging flow rate from the mechanical seal portion of the recirculation pump 31 that forcibly circulates the coolant inside the nuclear reactor is also sent to the waste treatment device 28 . This water is purified here and returned to the condensate storage tank 20 for reuse, while the remaining water is discharged into a pit 29 and taken out of the plant.

When replenishing water to the main condenser 8, the replenishment water pump 22 replenishes the water in the condensate storage tank 20,
To replenish water to the condensate storage tank 20, another system is provided for feeding water from outside.

The fuel storage pool cooling and purification system uses a heat exchanger 41 and a purification device 42 to remove decay heat from spent fuel and purify the pool water.

Furthermore, the pressure control pool 5, which is part of the containment system, stores pool water and absorbs the energy of the high-temperature, high-pressure coolant that is released in the event of a primary system piping rupture accident. It functions as a water source that is pressurized by the cooling pump 24 and injected into the reactor pressure vessel 1. Condensate storage tank 2
0 water also has a function as a water source.

However, this pressure suppression pool water is rarely used except in the event of a loss of coolant accident as mentioned above, and is used for periodic inspections of turbine-driven pump operations, equipment and piping during reactor shutdown, and when the cooling system is operating. Reactor water containing radioactive materials such as crud flows in and accumulates due to warm-up, subsequent pump tests, activation of the relief safety valve of the main steam pipe 9, etc., and if this continues for a long period of time, it will cause damage to the pressure suppression pool 5 and its surroundings. may increase the dose rate. Therefore, the equipment,
Injecting water into the reactor pressure vessel 1 when repairing piping or by activating the emergency core cooling system may also have an adverse effect on the reactor internal structures.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
The purpose of this is to remove crud containing radioactive materials that flow into the pressure suppression pool during test runs of reactor safety pumps, etc. The solids that settle early are allowed to settle in the pressure suppression pool, and are then placed in the pool water. The object of the present invention is to provide a purification device for a nuclear reactor cooling system in which floating crud and the like are removed in a pressure suppression pool water cooling and purification system to obtain pressure suppression pool water as clean as condensate.

[Summary of the invention]

In order to achieve the above object, the present invention provides an emergency core cooling system and a fuel storage system in which condensate from a main condenser flows into a pressure suppression pool and the pool water stored in the pressure suppression pool is used as a water source. In a reactor cooling system purification device equipped with a fuel storage pool cooling and purification system that cools and purifies pool water, the pressure suppression pool also serves as a condensate storage tank for adjusting surplus water and serving as a water source for the cooling system. This pressure suppression pool has a waste treatment system connected to the drain pipe of the control rod drive unit and piping led from the mechanical seal part of the recirculation pump, and a pressure suppression pool equipped with at least a heat exchanger for water cooling and purification. system is connected to the pressure suppression pool, and of the crud flowing into the pressure suppression pool, the crud that precipitates in the pool is left as is, and the floating crud is removed by the pressure suppression pool water cooling purification system. shall be.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic system diagram showing the flow of water around a nuclear reactor according to an embodiment of the present invention. The same parts as in FIG. 1 will be described with the same reference numerals.

A reactor containment vessel 2 is provided surrounding a reactor pressure vessel 1 having a plurality of control rod drive devices 26 provided at its bottom. A partition wall 3 is provided that divides the inside of the reactor containment vessel 2 into an upper reactor well 4a and a lower dry well 4b. Reactor containment vessel 2
A pressure suppression pool 5 is provided below the outside, and a reactor building 6 is provided surrounding it. A turbine 7 and a main condenser 8 are provided outside the reactor building 6, and the reactor pressure vessel 1 is connected to a valve 10a,
They are connected by main steam piping 9 via 10b and 10c. A pipe 11 is provided from upstream of the valve 10b to bypass the turbine 7 and connect to the main condenser 8 via a valve 12. This main condenser 8 communicates with the turbine 7, and is further connected to a water supply pipe 19 via a condensate pump 13, a condensate purification device 14, feed water heaters 15, 17, a boost pump 16a, a water supply pump 16b and a valve 18. The connection to the furnace pressure vessel 1 is the same as in the conventional case. Pressure suppression pool 5
The control rod drive device 26 and the control rod drive pump 2
4. Piping 27a connecting the water pressure control unit 25
The return pipe 27b is also connected to the waste treatment device 28 having a drain pipe to the pit 29 via the water pressure control unit 25, and further connected to the pressure suppression pool 5 by the pipe 30 via the pump 54. ing. The reactor pressure vessel 1 includes a recirculation pump 31 and piping 32 that forcefully circulate the reactor core flow rate.
A recirculation system consisting of the following is provided within the reactor containment vessel 2. The mechanical seal portion of this recirculation pump 31 is connected to a pipe 33 that communicates with the waste treatment device 28.
is provided.

There is a fuel storage pool 38 in the upper part of the reactor building.
And the skimmer surge tank 39 connected to this
are provided, a valve 40, a pump 41, a heat exchanger 4
2. A fuel storage pool cooling and purification system is constituted by the purification device 43 and the pipe 44 connected to the reactor well 4a.

The pressure suppression pool 5 includes an emergency cooling pump 34,
It is connected to the reactor pressure vessel 1 through a valve 35 and a piping 36 to constitute an emergency core cooling system. Furthermore, outside the pressure suppression pool 5, there is a pump 47, a heat exchanger 48, a purification device 49, and piping 5 connecting these.
0, a heat exchanger 48, and a pipe 51 that bypasses the purification device 49. A pressure suppression pool cooling and purification system is provided. The downstream side of the purifier 49 in this system is the valve 52.
It is connected to the waste treatment device 28 via a pipe 53. Further, the suction side of the pump 41 of the fuel storage pool cooling purification system and the pressure suppression pool 5 are connected by a pipe 45, and the downstream side of the purification device 14 of the water supply system is connected by a pipe 21. The pressure suppression pool 5 and the main condenser 8 are connected via a makeup water pump 22 and a pipe 23 .

FIG. 3 is a system diagram showing details of the pressure suppression pool cooling and purification system of FIG. 2, and the same parts as in FIGS. 1 and 2 are given the same reference numerals for explanation.

A pump 47 is provided outside the pressure suppression pool 5 and connects the pressure suppression pool 55 and piping 50 via a valve 55.
The piping 50 connects the heat exchanger 48, the purification device 49, the flow rate detection device 56, and the valves 57, 58, 5.
9 are connected to each other to form a closed loop returning to the pressure suppression pool 5. Heat exchanger 48, purification device 49
Piping 51 and valves 60a, 60b,
60c is provided. In addition, valve 55 and valve 5
9 shall be automatically driven and have the function of an isolation valve.

Furthermore, FIGS. 4 and 5 show details of the suction and discharge parts in the pressure suppression pool 5 of this system, and the same parts as in FIGS. 1 to 3 are given the same reference numerals and explained. shall be carried out.

In the Mark I reactor, the pressure suppression pool 5 has a donut shape with a circular cross section as shown in FIG. It is provided. Since these reinforcing rings 5a are attached in the form of protrusions within the pressure suppression pool 5, contaminants that accumulate at the bottom of the pressure suppression pool 5 will accumulate in each segment and are not expected to migrate between them.

Experiments have shown that it is impossible to stir up all the contaminants such as crud that have settled at the bottom of the pressure suppression pool by water agitation, and that methods such as jet flow using high-pressure water are effective. To purify the pool water while blowing up all the contaminants such as crud accumulated at the bottom of the suppression pool 5 using a jet flow using high-pressure water,
This would waste a considerable amount of time and energy, and it would be impractical to remove the crud deposited at the bottom of the pool by other means. Therefore, contaminants such as crud that have settled at the bottom of the pressure suppression pool are excluded from the purification of the pool water, and the pool water is purified. To do this, the suction pipe 5 must be
0a and the discharge pipe 50b may be provided on opposite sides of the pressure suppression pool 5, respectively.

Next, the operation of the nuclear power plant of the present invention will be explained.

Steam generated within the reactor pressure vessel 1 is sent to the turbine 7 through the main steam pipe 9, rotates the turbine 7, and is condensed in the main condenser 8. In some cases, the water passes through a pipe 11 that bypasses the turbine and is condensed in the main condenser 8. The pressure of the condensed water is increased by the condensate pump 13 and purified by the condensate purifier 14. A portion of the water is returned to the pressure suppression pool 5 through the pipe 21, and the rest is heated by the feed water heaters 15 and 17. It is pressurized by the booster pump 16a and the water supply pump 16b and returned to the reactor pressure vessel 1 through the water supply pipe 19. Furthermore, the control rod drive device 26 provided at the bottom of the reactor pressure vessel 1 is cooled by pressure suppression pool water during normal reactor operation. This water flows into the reactor pressure vessel 1 through the control rod drive device 26 .

The control rod driving device 26 may be cooled by taking water from the downstream side of the condensate purification device 14 of the condensate water supply system. Further, when the reactor is scrammed, the waste water from the control rod drive device 26 is sent to the waste treatment device 28 through the pipe 27b. A staging flow rate from the mechanical seal of the recirculation pump 31 that forcibly circulates the coolant inside the reactor is also sent to the waste treatment device 28, where this water is purified and pumped for reuse. 54, the remaining water is returned to the pressure suppression pool 5, and the remaining water is discharged into the pit 29 and taken out of the plant.

In the fuel storage pool cooling and purification system, the pressure is increased by a pump 41 as in the conventional case, and the pressure is returned to the fuel storage pool 38 through a heat exchanger 42 and a purification device 43 to remove decay heat from the spent fuel and purify the pool water. Furthermore, in case of an emergency, the pressure suppression pool water can be pumped 34.
The reactor core is cooled by injecting it into the reactor pressure vessel 1 through the piping 36. At the time of fuel exchange, the reactor well 4a is filled with water, and at that time, this system also injects pressure suppression pool water into the reactor pressure vessel 1 with the top removed, and fills the upper part of the reactor pressure vessel 1 with the top removed. Water flows out into the reactor well 4a to fill it with water. In addition, reactor well 4a
When draining water, open the valve of the pipe connected to the reactor well of the fuel storage pool cooling and purification system, and drain the pipe 45.
The pressure is discharged through the pressure suppression pool 5. In either case, the reactor is shut down and the reactor core is filled with water, so there is no safety problem.

In the nuclear power plant with the above configuration, the pressure suppression pool water is purified by increasing the pressure of the pressure suppression pool water with the pump 47, using the heat exchanger 48, and the purification device 49.
The pool water is cooled and purified, and then returned to the pressure suppression pool 5 for purification. However, when purifying pool water, test runs of the reactor safety pumps, which are the source of inflow of contaminants such as crud into the pressure suppression pool 5, are conducted about once a month, according to actual results. Since safety piping is mainly made of carbon steel, corrosion-induced crud flows into the pressure suppression pool once a month. As shown in the results of the sedimentation test of pressure suppression pool water crud iron in Fig. 7, it was found that more than 90% of the crud iron that flows into the crud sediments in about 10 hours. In addition, Figure 8 shows the particle size of crud in the pressure suppression pool water, which shows the particle size distribution of crud deposited at appropriate locations A, B, C, D, and E in the pressure suppression pool. It is a distribution map. Furthermore, from this research example, it can be assumed that most of the particle sizes of the deposited crud are 3μ or more, and it is easy to blow up crud of this size with the flow velocity of the pressure suppression pool water. Instead, if we were to use a purification system to treat the deposited crud in a Mark I 800,000 class model, the flow rate in the pressure suppression pool would need to be at least 2500 m ³ /hr in order to lift the crud, as shown in Figure 9. However, pumps from other systems cannot be used in common because their capacity does not match, and a pump with this capacity must be installed separately, resulting in a completely uneconomical power generation plant. Furthermore, even if it is installed separately, it is difficult to completely remove the deposited crud due to the influence of the structure within the pressure suppression pool.

From the above, it is best to remove the deposited crud and purify the pressure suppression pool water, and this purification is done using a purification device after the reactor safety system pump test run, which is carried out once a month. If this is done, clean pool water can be obtained in a short time with a small processing flow rate.

As an example, let us consider the case of purification using a purification device for a 1.3 million MWe class fuel storage pool cooling purification system.
As shown in the figure. Curve B shows the initial crud concentration in the suppression pool water after the reactor safety pump test run.
In the case of 10-odd ppm, if purification is started at the same time as sedimentation starts, it is possible to purify the pool water into clean pool water in about one day.Curve A shows the case where all the inflowing clades are somehow swept up and purified. It shows that it takes approximately 50 to 70 hours to purify the water. In addition, to purify pool water, the suction pipe of the purification device installed in the pressure suppression pool is set, and the discharge pipe is set in the opposite position from where it is set.
To uniformly purify pool water in a short time by preventing short passes of water in the pool water.

According to the pressure suppression pool water purification method described in detail above, by purifying the pool water by settling most of the inflowing crud, it becomes possible to obtain clean pool water that can be used as condensate. Therefore, there is no need to purify the pool water by raising the sedimentary crud with enormous energy, and there is no need to treat the sedimentary crud at the bottom with the purification device, so the burden on the purification device is light. Therefore, the equipment cost, operating cost, and amount of waste generated for the purification device are minimized, making it possible to purify the pressure suppression pool with an overall inexpensive configuration. Furthermore, it is possible to purify pool water with a purification device for the fuel pool purification system, which requires less effort.In this case, all that is required is the additional setting of connection pipes, valves, and pumps for the pool water, and it can be used in existing plants. Pool water can be purified easily and inexpensively. It is preferable to periodically remove the crud deposited on the bottom by other means.

In the embodiment described above, the condensate storage tank is omitted and the pressure suppression pool also functions as the condensate storage tank, so that the installation space of the plant can be significantly reduced.

FIG. 6 is a system diagram showing another embodiment of the pressure suppression pool cooling and purification system for a nuclear power plant according to the present invention, and the same parts as in FIGS. 1 to 5 will be described with the same reference numerals.

There is a fuel storage pool 3 in the upper part of the reactor building 6.
8 and a skimmer surge tank 39 communicating therewith, the fuel storage pool is cooled and purified by a pump 41, a heat exchanger 42, a purification device 43, and piping 44 connecting this to the reactor well 4a and valves 40, 40a. The structure of the system is the same as before. On the other hand, a pipe 61 and valves 61, 63 that connect the pressure suppression pool 5 provided below the reactor containment vessel 2, an auxiliary pump 62 located outside of this pool, and the suction side pipe of the pump 41 of the fuel storage pool cooling and purification system;
Furthermore, a pressure suppression pool cooling and purifying system is provided which is comprised of a pump 41, a heat exchanger 42, a purifying device 43, and piping 68 and valves 65, 66, and 67 that connect these. In other words, the pump 41 of the fuel storage pool cooling purification system,
The structure is such that the heat exchanger 42 and the purification device 43 are also shared in the pressure suppression pool cooling and purification system. Of course, the arrangement order of the pump 41, heat exchanger 42, and purifier 43 does not necessarily have to be as shown in the figure. Note that the auxiliary pump 62 may not necessarily be necessary due to the arrangement of the equipment.

In the fuel storage pool cooling and purification system, water overflowing from the fuel storage pool 38 flows into the skimmer surge tank 39 through a weir, is pressurized by a pump 41, and is cooled and purified by a heat exchanger 42 and a purification device 43, respectively.
The fuel is purified and returned to the fuel storage pool 38 again. On the other hand, the pressure suppression pool cooling and purification system allows the pressure suppression pool water to flow into the suction side of the pump 41 of the fuel storage pool cooling and purification system located several tens of meters above the ground.
The pressure is increased by the auxiliary pump 62. Then, the pressure of the pool water is increased by the pump 41, and the pool water is cooled and purified through the heat exchanger 42 and the purification device 43, and is returned to the pressure suppression pool 5.

Reactor water flows into the pressure suppression pool 5 when the turbine exhaust main steam relief safety valve for driving the pump of the emergency core cooling system is activated and when the reactor shutdown cooling system is started or stopped, and once the pressure is suppressed. If the pool water is purified, the pool water will not be contaminated by radioactivity as much unless the above devices are activated. On the other hand, the fuel storage pool cooling and purification system requires continuous operation immediately after fuel exchange to remove heat from the fuel storage pool and purify it, but even in this case, once the fuel storage pool water is purified, it will not become contaminated. If the decay heat of the fuel removed from the reactor core and stored falls, continuous operation is no longer necessary. Therefore, by combining both the emergency core cooling system and the thermal storage pool cooling and purification system and sharing some equipment, it is possible to rationalize the system without impairing the functions of both systems. I can do it.

Furthermore, in this embodiment, the condensate storage tank is omitted and the pressure suppression pool also functions as the condensate storage tank, so that the installation space of the plant can be significantly reduced.

Although the present invention has been described above with reference to specific examples thereof,
It goes without saying that the present invention is not limited to these specific embodiments, and that many modifications can be made without departing from the spirit of the invention.

〔Effect of the invention〕

As explained above, according to the present invention, the pressure suppression pool also has the function of a condensate storage tank by keeping the pressure suppression pool water clean at all times, thereby eliminating the need for a condensate storage tank. This can significantly reduce plant space. Furthermore, compared to a condensate storage tank that is open to the atmosphere, the pressure suppression pool is a closed container that is shielded from the atmosphere, including the reactor containment vessel, so the amount of dissolved oxygen and other harmful gases is reduced by piping, etc. will decrease. Furthermore, even if the pressure suppression pool water is injected into the reactor pressure vessel using the emergency core cooling system or the like, the quality of the pool water is controlled, so it will not affect the reactor internal structures. Furthermore, by installing a heat exchanger in the pressure suppression pool water cooling and purification system, it is possible to not only purify the pool water but also lower the pool water temperature to a possible temperature, which is a device that was previously subject to restrictions due to the rise in pool water temperature.・The safety and economic efficiency of nuclear power plants can be further improved as piping, etc. will no longer be subject to such restrictions.

[Brief explanation of drawings]

FIG. 1 is a schematic system diagram showing the flow of water around a conventional nuclear reactor, FIG. 2 is a schematic system diagram showing the flow of water around a nuclear reactor according to an embodiment of the present invention, and FIG.
Figure 4 is a system diagram of the pressure suppression pool cooling and purification system, Figure 4 is a plan view showing the piping arrangement in the pressure suppression pool of the pressure suppression pool cooling and purification system of Figure 3, and Figure 5 is the system diagram of the pressure suppression pool cooling and purification system.
Figure 6 is a system diagram showing another embodiment of the pressure suppression pool cooling and purification system, Figure 7 is a diagram showing the results of a sedimentation test of crud collected from the pressure suppression pool water, and Figure 8 Figure 9 shows the particle size distribution results of crud collected from the pressure suppression pool water, and Figure 9 shows the relationship between the flow rate in the pressure suppression pool and the crud particle size when the crud deposited in the pressure suppression pool water is suspended. The figure shown in FIG. 10 is a diagram showing the change in crud concentration in the pressure suppression pool when the pressure suppression pool is purified by the fuel storage pool purification system after a test run of the reactor safety system pump. 1... Reactor pressure vessel, 2... Reactor containment vessel, 5
... Pressure suppression pool, 7 ... Turbine, 8 ... Main condenser, 20 ... Condensate storage tank, 22 ... Make-up water pump, 24 ... Control rod drive pump, 25 ... Water pressure control unit, 26 ... Control rod drive device, 28 ...waste processing equipment, 31...recirculation pump, 34...emergency core cooling pump, 38...fuel storage pool, 39...skimmer surge tank, 41, 45, 47, 62...pump, 42,48...heat exchanger, 43, 49...Purification device.

Claims (1)

[Claims] 1. An emergency core cooling system that allows condensate from the main condenser to flow into the pressure suppression pool and uses the pool water stored in the pressure suppression pool as a water source, and a fuel storage pool that cools and purifies the pool water of the fuel storage pool. In a reactor cooling system purification device equipped with a cooling purification system, the pressure suppression pool also serves as a condensate storage tank that adjusts surplus water and serves as a water source for the cooling system. a waste treatment device to which pipes led from the drainage pipe and the mechanical seal of the recirculation pump are connected;
A pressure suppression pool water cooling purification system equipped with at least a heat exchanger is connected, and among the crud flowing into the pressure suppression pool, the crud that precipitates in the pool remains as it is, and the floating crud is absorbed by the pressure suppression pool water. A purification device for a nuclear reactor cooling system, characterized in that the removal is carried out by a cooling purification system.