JPH05240996A - Coolant purification system for boiling water reactor - Google Patents

Abstract

PURPOSE:To reduce the construction cost of a plant and the generation of radioactive waste, simplify operation action, improve plant heat efficiency and lower the possibility of occurrence of malfunction. CONSTITUTION:High pressure coolant including impurity ion, suspension and the like driven by the pressure difference from a low pressure water condenser system passes a pipe drawn out of the reactor vessel 1 and a high temperature filtering and demineralizing device 2 capable of eliminating positive ion and suspension at high temperature which is provided in the middle of the pipe and flows in the condenser system. The coolant flow rate is controlled by a flow control valve 8 provided in the piping. To prevent flashing phenomenon due to sudden pressure drop of the coolant, a heat exchanger for cooling at upstream of the flow control valve 8 or a flash tank 9 at downstream is placed. The coolant is eliminated of impurities including negative ion by filtering demineralizing devices 15, 16, heated and pressurized by a heat exchanger and a pump in the condensed water and supply water system and sent into the reactor vessel 1 together with the condensed water from the main steam system side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to impurity ions accumulated in a nuclear reactor as the coolant evaporates in the boiling water reactor.
The present invention relates to a coolant purification system for removing suspended matters and the like and keeping the coolant circulation system normal.

[0002]

2. Description of the Related Art In a reactor pressure vessel of a boiling water reactor, impurities mixed in the coolant accumulate as the coolant evaporates. Such impurities are activated by a large amount of radiation generated from the core, which contaminates the equipment in the nuclear reactor facility and causes mechanical adverse effects such as narrowing of pipes and breakage of pumps. In order to prevent this, conventionally, in boiling water nuclear power plants, the coolant is branched and taken out directly from the core or from the pipe of the coolant recirculation system, and the regenerated heat exchanger, non-regenerated heat exchanger, low-temperature filtration / The reactor coolant is purified by passing it through a coolant purification system consisting of a desalination device and a pump.

In order to further reduce the decrease in the thermal efficiency of the plant due to the coolant purification system, a system using a high temperature demineralizer is arranged in parallel with the coolant purification system as described above, and a part of the system is used here. The method of removing only ions is
It is disclosed in Japanese Patent Laid-Open No. 53-186696. This method is shown in FIG. 1 is a boiling water reactor. Reference numeral 51 is a high-temperature desalination device, which includes a pump 52 and a non-regenerative heat exchanger 5
3. Connected in parallel to the low temperature coolant purification system including the low temperature desalination device 54. 55 is a feed water heater and 56 is a feed pump. In this method, since it is not necessary to use a heat exchanger in the system of the high temperature desalination apparatus 51, the thermal efficiency of the plant is partially improved.

[0004]

In the publicly known example described at the end of the above, it is expected that the thermal efficiency of the plant will be improved by separately installing the system of the high temperature demineralizer, but it should be removed by the high temperature demineralizer. In order to remove difficult anions, conventional regeneration, non-regeneration heat exchanger, low temperature filtration
A coolant purification system including a desalting device and a pump for obtaining driving force for the coolant is also required.

When a dynamic device such as a pump is used, it is usual to provide a standby machine in case of failure, and accordingly,
Increased need for equipment maintenance and inspection. In addition, since the auxiliary material used in the filtration / desalination device is a consumable item, it is regularly discharged as radioactive waste, and the amount of radiation exposure during replacement work also increases. Furthermore, a large number of heat exchangers, pipes, and valves of the coolant purification system complicate the configuration of the plant,
Not only does it make driving difficult, but it also contains potential failures such as leaks.

Therefore, the present invention reduces the equipment required for constructing the coolant purification system while maintaining the necessary functions of the coolant purification system of the boiling water reactor, thereby reducing the cost of plant construction. An object of the present invention is to provide a reactor coolant purification system capable of reducing unnecessary radioactive waste, simplifying operation and reducing the possibility of failure.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, one end is connected to a portion where a coolant exists in a reactor pressure vessel and the other end is condensate / condensate filtration / desalination of a water supply system. Provide piping connected to the upstream part of the equipment. High-temperature filtration / desalination that operates at high temperature to prevent activated impurity ions and suspended solids in the reactor pressure vessel from flowing into the relatively clean condensate / water supply system through the above piping. Install the device in the middle of the above piping. Further, in order to adjust the flow rate of the coolant flowing in the pipe, a flow rate adjusting valve is provided in the pipe. In order to prevent flushing that occurs when the coolant flowing into the condensate / feedwater system through this pipe as described above is suddenly decompressed by the flow control valve from the high pressure state in the reactor vessel, the flow control valve A flash tank is provided upstream of the heat exchanger for cooling the coolant or downstream of the flow rate adjusting valve in the pipe.

[0008]

[Operation] Impurity ions accumulated in the reactor pressure vessel,
High-pressure coolant containing suspended matter, etc., uses the pressure difference between the high pressure in the reactor pressure vessel and the low pressure in the upstream part of the condensate filtration / desalination device in the condensate / feedwater system as the driving force. , From the reactor pressure vessel, through the above piping, flows into the condensate / water supply system. In this case, in order to maintain the cleanliness of the condensate / water supply system, the coolant is allowed to pass through a filtration / desalination device that operates at high temperature installed in the middle of the above pipe, and in this filtration / desalination device, At least cations and suspensions are removed from the coolant. Due to this action, the cleanliness of the coolant is such that the condensate / water supply system is not contaminated or damaged even if it is discharged to the upstream side of the condensate / water supply system condensate filtration / desalination system. The filtration in the above piping
It is possible to adjust the flow rate of the coolant flowing through the pipe by using a flow rate adjusting valve provided upstream or downstream of the desalination device. Furthermore, in order to prevent flushing development that occurs due to a sudden pressure drop of the coolant due to this flow control valve, a heat exchanger for cooling the coolant installed upstream of the flow control valve or downstream of the flow control valve was installed. The flash tank reduces the saturation pressure of the coolant. The coolant that has flowed into the upstream side of the condensate filtration / desalination system of the condensate / water supply system through such a route has impurities such as anions removed by the condensate filtration / desalination system, and the main steam is removed. Along with the condensate from the system side, it is heated and pressurized by a condensate / feed water heat exchanger (feed water heater) and a pump, and then fed into the reactor pressure vessel.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention according to claim 2 will be described with reference to FIG. In this embodiment, a high temperature filtration / desalination apparatus 2 is installed in a pipe 5 drawn from a reactor pressure vessel 1 of a boiling water reactor.
(For example, a filter using a cobalt adsorption alloy or an electromagnetic filter) is connected, the flow rate adjusting valve 8 is connected to the downstream side of the high temperature filtration / desalination apparatus 2, and the flash tank 9 is further provided to the downstream side of the flow rate adjusting valve 8. , And the liquid phase portion of the flash tank 9 is connected to a pipe at an upstream portion of the condensate filtration / desalination apparatus by a pipe 6. 7 is a check valve. As shown in the figure, from the condenser 11 for condensing steam from a steam turbine (not shown), a low-pressure condensate pump 12, a condensate filter 15, a condensate demineralizer 16, and a high-pressure condensate pump 17 in that order. , Low pressure feed water heater 18, feed water pump 19, high pressure feed water heater 2
As in the conventional boiling water reactor plant, a condensate / water supply system that goes from 0 to the reactor pressure vessel 1 is provided. The pipe 6 is connected to the upstream pipe of the condensate filter 15 of the condensate / water supply system at a confluence A. The pipe 5 is not limited to the one directly drawn out from the reactor pressure vessel 1, and may be a pipe branched from a recirculation system pipe or a residual heat removal system pipe of the nuclear reactor.

The reactor coolant purification system of this embodiment is connected to a condensate / water supply system from the reactor pressure vessel 1 through a pipe 5, a high temperature filtration / desalination device 2, a regulating valve 8, a flash tank 9 and a pipe 6. From the confluence point A to the confluence point A of
Condensate filter 1 as a common part of the condensate / water supply system
5, a condensate demineralizer 16, a high-pressure condensate pump 17, a low-pressure feed water heater 18, and a system leading to a reactor pressure vessel via a feed water pump 19.

The operation of this embodiment will be described with reference to FIG. The high-pressure coolant containing impurities in the reactor pressure vessel 1 is
The pressure difference from the low-pressure condensate system is used as a drive source, passes through the pipe 5, and flows into the high-temperature filtration / desalination apparatus 2 that operates at high temperature.
To adjust the flow rate of the coolant flowing into the high temperature filtration / desalination apparatus 2 through the pipe 5, the adjustment valve 8 is operated. In the high temperature filtration / desalination apparatus 2, cations such as activated metal ions and foreign matters such as suspended matter are removed from the coolant. The temperature and pressure are lowered by causing adiabatic change in the coolant in the flash tank 9 installed downstream of the adjusting valve 8. At this time, the steam generated in the flash tank 9 is guided to the condenser 11 through the pipe 10 to be condensed, while the liquid coolant from the liquid phase portion of the flash tank 9 passes through the pipe 6 and the check valve 7. From the confluence A into the upstream pipe of the condensate filter 15. Since the temperature and pressure of the coolant are lowered in the flash tank 9, the adjustment valve 8
Even if the pressure is reduced by, the coolant does not cause the flushing phenomenon at the confluence A with the condensate system, and flows into the condensate system in a liquid state.

Condensate filter 1 through check valve 7 and pipe 6.
In the condensate filtering device 15, foreign substances are removed again from the coolant that has flowed into No. 5, and then into the condensate demineralizing device 16, where impurity ions including anions are removed. The coolant thus purified is pressurized and heated in two stages by the high-pressure condensate pump 17, the low-pressure feed water heater 18, and the feed water pump 19 and the high-pressure feed water heater 20, and the reactor pressure vessel 1 again. Delivered in.

As a modification of the embodiment shown in FIG. 1,
As shown in FIG. 2, the flash tank 9 may be arranged upstream of the high temperature filtration / desalination apparatus 2 depending on the temperature characteristics of the high temperature filtration / desalination apparatus 2. Further, as shown in FIG. 2, the adjusting valve 8
It is possible to lower the design pressure of the high temperature filtration / desalination apparatus 2 by arranging the high temperature filtration / desalination apparatus 2 on the upstream side. The portion that actually becomes high pressure is from the reactor pressure vessel 1 to the position of the adjusting valve 8. Therefore, by arranging the adjusting valve 8 on the upstream side, it is possible to cool the entire coolant purification system with high pressure as in the conventional case. Compared to the case where material flows, the length of equipment and piping with high pressure specifications can be significantly reduced.

Next, an embodiment of the present invention according to claim 3 will be described with reference to FIG. In the present embodiment, instead of the flash tank 9 in the embodiment of the present invention according to claim 2, a non-regenerative heat exchanger 3 cooled by an auxiliary equipment cooling system is arranged upstream of the regulating valve 8. This reduces the temperature of the coolant. As a result, the saturation pressure of the coolant is reduced, the flushing phenomenon does not occur even when the regulating valve 8 suddenly reduces the pressure, and the liquid coolant flows into the confluence A.

Also in this embodiment, as a modified embodiment, the positions of the regulating valve 8 and the non-regenerative heat exchanger 3 may be arranged on the upstream side of the high temperature filtration / desalination apparatus 2. Thereby, the operating pressure of the high temperature filtration / desalination device 2 and the non-regenerative heat exchanger 3 can be lowered.

An embodiment of the present invention according to claim 4 will be described with reference to FIG. In this embodiment, a regenerative heat exchanger 30 for heat recovery is further installed on the upstream side or the downstream side of the non-regenerated heat exchanger 3 in the embodiment shown in FIG. The regenerative heat exchanger 30 can be used as a heater for the control rod drive water supplied to the water pressure control unit 32 of the control rod drive system. In this case, the non-regeneration heat exchanger 3 may be deleted depending on the flow rate of the control rod driving water and the heating temperature. By recovering the heat by heating the control rod driving water and returning it to the inside of the reactor pressure vessel 1, the thermal efficiency of the plant can be improved.

[0017]

According to the present invention, the coolant in the reactor pressure vessel drives the pressure difference between the high pressure in the pressure vessel and the low pressure on the upstream side of the condensate filtration / desalination system of the condensate / water supply system. As a force
After passing through the piping from the reactor pressure vessel and removing cations and suspended matter with a high temperature filtration / desalination unit, condensate /
It flows into the water supply system, impurities such as anions are removed by the condensate filtration / desalination device, and pressurized and heated by the condensate pump, the water supply pump, and the water supply heater, and then returned to the reactor pressure vessel.
Therefore, according to the present invention, at least a pump dedicated to the reactor coolant purification system, a heat exchanger for heating, a filter / desalinator capable of removing anions, and pipes connecting them are not required. Moreover, compared with the flow rate of the condensate / feed water flowing from the condenser of the steam turbine to the condensate / feed water system, It is about 1%, so the condensate / water supply system may be the same as the conventional one. As a result, the following effects can be expected.

(1) The number of installed equipment is reduced, and the construction cost of the plant is reduced.

(2) The structure is simpler than that of the conventional reactor coolant purification system, the operation and maintenance work is facilitated, and the plant thermal efficiency is also improved.

(3) In the present invention, since there is no low-temperature filtration / desalination device used in the conventional reactor coolant purification system,
There is no radioactive waste generated from it, and in the present invention, a high temperature filtration / desalination device is provided in the pipe. However, since a high temperature filtration / desalination device generally has a long life, radioactive waste (used filtration The amount of auxiliary materials) is small. Therefore, in the present invention, the amount of radioactive waste is less than that of the conventional radioactive waste produced by the reactor coolant purification system, and the amount of radiation exposure during the replacement work of the filter aid is small.

(4) In the present invention, the whole system is compared with a conventional reactor coolant purification system in which high-pressure coolant flows,
Since the coolant flows into the condensate system with low pressure, the design condition is eased by shortening the piping part for high pressure specifications.
The effect of reducing the construction cost of the piping portion and the equipment provided in the piping can be expected. In particular, this effect becomes remarkable when the flow rate adjusting valve in the pipe is installed on the upstream side.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment according to the present invention of claim 2.

2 is a schematic view of another embodiment according to the present invention of claim 2; FIG.

FIG. 3 is a schematic diagram of an embodiment according to the present invention of claim 3;

FIG. 4 is a schematic diagram of an embodiment according to the present invention of claim 4;

FIG. 5 is a schematic view of a known example of a coolant purification system using a high temperature filter.

[Explanation of symbols]

1 ... Reactor pressure vessel 2 ... High temperature filtration
Desalination device 7 ... Check valve 8 ... Regulator valve 9 ... Flash tank 11 ... Condenser 12 ... Low pressure condensate pump 15 ... Condensate filtering device 16 ... Condensate desalination device 17 ... High pressure condensate pump 18 ... Low pressure water supply Heater 19 ... Water supply pump 20 ... High pressure water heater

Claims (4)

[Claims] 1. Condensate for condensing steam from a steam turbine for power generation, and condensate including a condensate pump, a condensate filtration / desalination device, a water supply pump and a water supply heater connected downstream of the condenser. -In a boiling water reactor equipped with a water supply system, one end is connected to the part where the coolant exists inside the reactor pressure vessel and the other end is upstream of the condensate / condensate filtration / desalination device of the water supply system. Provide a pipe connected to the side part, and in the middle of the above pipe,
A high temperature filtration / desalination device capable of removing cations and suspended solids from the high temperature coolant flowing in the pipe, and a flow rate adjusting valve capable of adjusting the flow rate of the coolant flowing in the pipe are provided. Characteristic boiling water reactor coolant purification system. 2. The coolant purification system for a boiling water reactor according to claim 1, further comprising a flash tank provided on the downstream side of the flow rate adjusting valve in the middle of the pipe. 3. The boiling water nuclear reactor according to claim 1, further comprising a heat exchanger capable of removing heat from a coolant flowing in the pipe in the middle of the pipe upstream of the flow control valve. Coolant purification system. 4. A heat exchanger for recovering heat from a coolant flowing in the pipe is provided in the middle of the pipe.
Or, the coolant purification system of the boiling water reactor of 3.