JP7094900B2 - Decontamination method and decontamination equipment - Google Patents

Description

An embodiment of the present invention relates to a decontamination method and a decontamination device for a boiling water reactor.

In the decommissioning of the reactor, fuel is taken out from the reactor after the reactor operation is stopped, and then decontamination before dismantling the system including the reactor pressure vessel is carried out. The system including the reactor pressure vessel is, for example, the reactor primary system, that is, the reactor pressure vessel (RPV: Reactor Presser Vessel), the reactor recirculation (PLR: Primary Loop Reculation) system, and the reactor coolant purification (CUW: Reactor). It is a system including a Water Clean-Up) system and a residual heat removal (RHR) system.

When chemically decontaminating a system including a reactor pressure vessel ^, the system capacity to be filled with the decontamination solution reaches several hundred m3. Conventionally, for chemical decontamination of the inside of a reactor pressure vessel, a method of circulating a decontamination liquid by a PLR pump, which is a device mainly installed in the primary reactor system, has been adopted. This PLR pump can secure a huge circulation flow rate and can obtain a large linear flow velocity. On the other hand, there is also disclosed a technique for carrying out chemical decontamination by circulating a decontamination liquid by operating a temporary pump without operating the PLR pump.

Japanese Unexamined Patent Publication No. 2000-69589 JP-A-2017-223524

In the embodiment of the present invention, when chemical decontamination is performed using a temporary pump without starting the PLR pump, the chemical decontamination of the reactor pressure vessel or the system including the reactor pressure vessel is carried out more efficiently. It is an object of the present invention to provide a decontamination method and a decontamination device.

The decontamination method according to the embodiment of the present invention is a decontamination method in which a reactor pressure vessel or a system including the reactor pressure vessel is decontaminated and chemical decontamination is performed. A step of closing at least one of the main steam pipes connected to the reactor, a first nozzle provided in the reactor pressure vessel, and a second nozzle provided below the first nozzle of the reactor pressure vessel. A step of connecting a nozzle to a reactor via a temporary system installed outside the reactor pressure vessel and constructing a circulation path including the first nozzle, the reactor pressure vessel, the second nozzle and the temporary system. The temporary system has a step of circulating the decontamination liquid in the circulation path, a temporary pump for circulating the decontamination liquid in the circulation path, and a drug supply unit for supplying the drug to the decontamination liquid. , A temperature regulator that adjusts the temperature of the decontamination liquid in the circulation path, a first temporary pipe that connects the temporary system and the first nozzle, and a second temporary pipe that connects the temporary system and the second nozzle. The first temporary pipe is provided with the temporary pump that gives a flow in only one direction and a plurality of valves connected in parallel with the temporary pump, and by switching the opening and closing of the plurality of valves, the said The circulation of the decontamination liquid in the circulation path is reversed, and the decontamination target of the chemical decontamination further includes at least one peripheral system of the reactor cooling material purification system and the residual heat removal system, and the reactor pressure vessel, at least. Including the step of isolating each of the peripheral systems into individual water flow areas, in this step, the chemical decontamination is sequentially carried out from the water flow area having a low contaminated radioactivity amount and a small decontamination capacity. It is characterized by that.

Further, the decontamination implementation device according to the embodiment of the present invention is a decontamination implementation device for chemically decontaminating a reactor pressure vessel or a system including the reactor pressure vessel as a decontamination target, and is a steam outlet nozzle and the decontamination implementation apparatus. From the closing plug that closes at least one of the main steam pipes connected to the steam outlet nozzle, the first nozzle installed outside the reactor pressure vessel and provided in the reactor pressure vessel, and this first nozzle. Also has a temporary system that connects to a second nozzle provided below the reactor pressure vessel to construct a circulation path, and the temporary system is a temporary pump that circulates the decontamination liquid in the circulation path. , A drug supply unit that supplies a drug to the decontamination liquid, a temperature regulator that adjusts the temperature of the decontamination liquid in the circulation path, a first temporary pipe that connects the temporary system and the first nozzle, and the temporary installation. A second temporary pipe connecting the system and the second nozzle is provided, and the first temporary pipe is provided with the temporary pump that gives a flow in only one direction and a plurality of valves connected in parallel with the temporary pump. By switching the opening and closing of the plurality of valves, the circulation of the decontamination liquid in the circulation path is reversed , and at least one of the reactor cooling material purification system and the residual heat removal system is targeted for decontamination of the chemical decontamination. The peripheral system is further included, and the reactor pressure vessel and at least one peripheral system are separated from each other into separate water flow areas, and the chemical decontamination is performed from the water flow area having a low contaminated radioactivity amount and a small decontamination capacity. Is characterized by sequentially carrying out .

According to the embodiment of the present invention, the chemical decontamination of the reactor pressure vessel or the system including the reactor pressure vessel can be carried out more efficiently.

The schematic block diagram of the nuclear power plant which the decontamination implementation method which concerns on 1st Embodiment is a decontamination target. Explanatory drawing explaining the decontamination execution method which concerns on 1st Embodiment. The flowchart which shows the decontamination execution method which concerns on 1st Embodiment. Explanatory drawing explaining the decontamination execution method which concerns on 2nd Embodiment. Explanatory drawing explaining the decontamination execution method which concerns on 3rd Embodiment. Explanatory drawing which shows the state which the decontamination liquid was circulated backflow in the decontamination execution method which concerns on 3rd Embodiment. Explanatory drawing explaining the decontamination execution method which concerns on 4th Embodiment. Explanatory drawing which shows the state which the decontamination liquid was backflow-circulated by the decontamination execution method which concerns on 4th Embodiment. Explanatory drawing explaining the decontamination execution method which concerns on 5th Embodiment. Explanatory drawing explaining the decontamination execution method which concerns on 6th Embodiment. Explanatory drawing explaining the decontamination execution method which concerns on 7th Embodiment. Explanatory drawing explaining the decontamination execution method which concerns on 8th Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
[I] First Embodiment (FIGS. 1 to 3)
FIG. 1 is a schematic configuration diagram of a nuclear power plant targeted for decontamination by the decontamination implementation method according to the first embodiment. Further, FIG. 2 is an explanatory diagram illustrating a decontamination implementation method according to the first embodiment.

1. 1. Main system First, the reactor pressure vessel 13 (RPV: Reactor Presser Vessel), the reactor recirculation system (PLR system: Primary Loop Recyclation System) 200, and the surrounding main system will be described.

In the boiling water reactor plant 9, the core 10 is housed in the reactor pressure vessel 13, and an annular downkama 14 is formed between the core shroud 11 surrounding the core 10 and the reactor pressure vessel 13. .. For example, 16 or 20 jet pumps 16 are arranged in a ring shape at predetermined intervals on the downcomer 14. A shroud head 17 that covers the upper part of the core 10 is fixedly provided on the core shroud 11. A steam separator 18 is installed on the shroud head 17, and a steam dryer 19 is provided above the steam separator 18.

A top lid cooling spray nozzle 1, a top lid instrumentation nozzle 2, and a vent nozzle 3 are installed on the crown of the reactor pressure vessel 13. An RHR (residual heat removal) head spray tube 26 for spraying a liquid such as a primary cooling material is connected to the top lid cooling spray nozzle 1.

Two or three PLR systems 200 are provided on the outside of the reactor pressure vessel 13. The primary cooling material flowing out from the lower part of the downkama 14 in the reactor pressure vessel 13 to the PLR system 200 via the recirculating water outlet nozzle 20 is boosted by the PLR pump 21 provided in the PLR system 200. The flow rate of the primary coolant flowing into the PLR pump 21 is adjusted by the PLR suction valve 22 and the PLR discharge valve 23 provided on the suction side and the discharge side of the PLR pump 21, respectively.

The primary cooling material is guided to the jet pump 16 via the recirculating water inlet nozzle 24, is ejected from the nozzle of the jet pump 16 as a jet drive fluid, and sucks the primary cooling material on the upper part of the downkama 14 to form a jet flow. The primary coolant ejected from the jet pump 16 is heated while passing through the core 10 to form a gas-liquid two-phase flow. The gas-liquid two-phase flow sent into the air-water separator 18 is separated into steam and water, and the steam is further dehumidified by the steam dryer 19, and then the steam outlet nozzle at the top of the reactor pressure vessel 13. It flows out from 27 and is supplied to a turbine system (not shown). The above configuration is an example of a nuclear power plant, and some plants may not have a jet pump.

The steam as the primary coolant that worked in the turbine system is condensed by a condenser (not shown) and heated by a water supply heater (not shown) to supply water, and the water supply nozzle 12 provided in the reactor pressure vessel 13 is provided. Guided by. A water supply spray ring 12A formed in an annular shape along the inner wall of the reactor pressure vessel 13 is connected to the water supply nozzle 12. The primary coolant as water supply guided to the water supply nozzle 12 is supplied from the water supply spray ring 12A into the reactor pressure vessel 13.

Further, in the reactor pressure vessel 13, a core spray ring 15A formed in an annular shape along the inner wall of the reactor pressure vessel 13 is arranged below the water supply spray nozzle 12A. The core spray ring 15A is connected to the core spray nozzle 15 provided in the reactor pressure vessel 13 at substantially the same height as the water supply nozzle 12. In an emergency of the core 10, the primary coolant is injected into the core 10 from the core spray ring 15A via the core spray nozzle 15.

In the reactor pressure vessel 13, the water separated by the air-water separator 18 and the steam dryer 19 flows down into the downkama 14 between the core shroud 11 and the reactor pressure vessel 13, and is sucked into the jet pump 16. It is guided to the core 10 and circulates in the reactor pressure vessel 13.

Further, a control rod drive mechanism housing 29, a neutron flux measurement housing 28, and a drain nozzle 30 are installed at the bottom of the reactor pressure vessel 13. The control drive mechanism housing 29 accommodates a control rod drive mechanism (not shown), and the control rod drive mechanism drives a control rod (not shown) to control the output of the core 10. Further, a neutron flux measuring instrument (not shown) is housed in the neutron flux measuring housing 28, and the neutron flux measuring instrument measures the neutron flux in the core 10. Further, the drain nozzle 30 is connected to the bottom drain line 31 to discharge the reactor water in the reactor pressure vessel 13.

Corrosion products are generated in the primary coolant flowing through the reactor pressure vessel 13, the PLR system 200, and the turbine system, and of these, the corrosion products that have passed through the core 10 and are activated are the constituents of the PLR system 200. It adheres to and accumulates on various devices including devices (20 to 24) and becomes a radiation source. Therefore, it is necessary to carry out chemical decontamination of contaminated pipes and equipment as a measure to reduce the exposure dose of workers at the time of decommissioning. The decontamination method and the decontamination device of each embodiment including the first embodiment chemically decontaminate the reactor pressure vessel 13 or the PLR system 200 including the reactor pressure vessel 13 as the main decontamination target. It is for dyeing.

In each embodiment, the above-mentioned reactor pressure vessel 13, PLR system 200 and RHR head spray pipe 26 are the main systems. In each figure, the PLR system 200 and the RHR head spray tube 26 are indicated by thick broken lines. Further, for the sake of simplification of the explanation, the other main system connected to the reactor pressure vessel 13 is omitted. Further, in the figure, the configurations provided on the left and right with symmetry centered on the reactor pressure vessel 13 are appropriately added with the words "left side" and "left side" as "left side PLR system 200L" and the like. Refer to.

2. 2. Decontamination implementation device 100A
Next, the decontamination implementation device 100A that implements the decontamination implementation method will be described. The decontamination implementation device 100A includes a closing plug 40 that closes the steam outlet nozzle 27, and a temporary system 300A that is installed outside the reactor pressure vessel 13 and constructs a circulation path 401 in which the decontamination liquid circulates. Consists of having.

In the closing plug 40, for example, when the steam separator 18 and the steam dryer 19 are removed from the inside of the reactor pressure vessel 13, the steam outlet nozzle 27 of the reactor pressure vessel 13 is placed inside the reactor pressure vessel 13. Close from. Further, the closing plug 40 cuts the main steam pipe (not shown) connected to the steam outlet nozzle 27, for example, when the steam separator 18 and the steam dryer 19 are present in the reactor pressure vessel 13. The steam outlet nozzle 27 is closed by closing the closing plug 40 at this cutting point. However, when the closing plug 40 closes the cut portion of the main steam pipe, the main steam pipe is used when the concentration of the decontamination liquid (described later) in the reactor pressure vessel 13 becomes low and the decontamination effect is reduced. The liquid (water) mixed with the decontamination liquid stored in the temporary system 300A may be drained.

In the temporary system 300A, the temporary system 300A is connected to the first nozzle (described later), the first temporary pipe 39 for connecting the decontamination liquid to the first nozzle (described later), and the temporary system 300A is connected to the second nozzle (described later). It is configured to have a second temporary pipe 48 to be connected so that it can be distributed, and a third temporary pipe 56 to connect the first temporary pipe 39 and the second temporary pipe 48. Further, the temporary system 300A includes a temporary pump 25 arranged in the first temporary pipe 39, the second temporary pipe 48, or the third temporary pipe 56 (the first temporary pipe 39 in the first embodiment), and the third temporary pipe. It is configured to have a drug preparation unit 50 and an ozone generator 51 as a drug supply unit arranged in 56, a heat exchanger 49 as a temperature regulator, and a purification system 57.

The first nozzle is at least one of a water supply nozzle 12 and a core spray nozzle 15 (in the first embodiment, all or a part of the four water supply nozzles 12 and the two core spray nozzles 15). In the first embodiment, the first temporary pipe 39 is directly connected to at least one of these water supply nozzles 12 and the core spray nozzle 15, but is connected to each of these water supply nozzles 12 and the core spray nozzle 15. It may be connected to a pipe.

The second nozzle includes at least one of a control rod drive mechanism housing 29, a neutron flux measurement housing 28, and a drain nozzle 30 (in this embodiment, a plurality of control rod drive mechanism housings 29 and a plurality of neutron flux measurement housings 28). All or part of each of the drain nozzles 30). Of these, the drain nozzle 30 is connected to the bottom drain line 31. The second temporary pipe 48 may be directly connected to at least one of the control rod drive mechanism housing 29, the neutron flux measurement housing 28, and the bottom drain line 31, but in the first embodiment, the control rod drive mechanism housing 29, It is connected to the bottom header pipe 32 connected to the neutron flux measurement housing 28 and the bottom drain line 31. A bottom valve 69 is arranged in the bottom header pipe 32.

By the first temporary pipe 39, the second temporary pipe 48, and the third temporary pipe 56 of the temporary system 300A, at least one of the water supply nozzle 12 and the core spray nozzle 15 of the reactor pressure vessel 13, and these water supply nozzle 12, the core spray At least one of the control rod drive mechanism housing 29, the neutron bundle measurement housing 28, and the drain nozzle 30 provided below the reactor pressure vessel 13 is connected so that the decontamination liquid can flow, and the circulation path 401 is established. Will be built.

Therefore, the circulation path 401 includes the temporary system 300A, the water supply nozzle 12, and at least one of the core spray nozzle 15 and the top lid cooling spray nozzle 1 in a state where the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40. One or two of the upper lid instrumentation nozzle 2 and the vent nozzle 3, the reactor pressure vessel 13, the control rod drive mechanism housing 29, the neutron bundle measurement housing 28, at least one of the drain nozzles 30, and the temporary system 300A. The decontamination liquid is made to flow from the upper side to the lower side in the reactor pressure vessel 13 by the action of the temporary pump 25 of the temporary system 300A, and the decontamination liquid is circulated.

That is, when circulating in the circulation path 401, the decontamination liquid is withdrawn from the reactor pressure vessel 13 to the temporary system 300A via at least one of the control rod drive mechanism housing 29, the neutron bundle measurement housing 28, and the drain nozzle 30. Then, from the temporary system 300A, the reactor pressure vessel 13 passes through at least one of the water supply nozzle 12 and the core spray nozzle 15, and further passes through one or two of the top lid cooling spray nozzle 1, the top lid instrumentation nozzle 2, and the vent nozzle 3. It flows in.

The piping configuration of the temporary system 300A including the first temporary piping 39, the second temporary piping 48, and the third temporary piping 56 will be described in more detail.

In the temporary system 300A, the PLR bottom pipe 33 is connected between the PLR pump 21 and the PLR discharge valve 23, and the PLR middle pipe 34 is connected to the downstream side of the PLR discharge valve 23 for each of the left and right PLR systems 200. To. Of these, the PLR bottom pipe 33 is connected to the second temporary pipe 48.

Further, the right side PLR middle pipe 34R is connected to the left side PLR middle pipe 34L via the left and right connecting pipes 34C, and the decontaminating liquid flowing through the right side PLR middle pipe 34R is supplied to the left side PLR middle pipe 34L. It should be noted that the two circles A described on the left and right connecting pipes 34C in the figure indicate that they are continuous with each other. The left and right connecting pipes 34C are provided with left and right connecting valves 37.

Further, the right side PLR middle pipe 34R is provided with a PLR middle valve 38 between the connection point to the left and right connecting pipes 34C and the connection point to the PLR system 200. The right side PLR middle pipe 34R is connected in a T shape to the first temporary pipe 39 connected to the water supply nozzle 12 or the furnace water spray nozzle 15. Further, the right side PLR middle pipe 34R is connected between the temporary pump 25 and the nozzle valve 47 (described later) in the first temporary pipe 39.

In the first temporary pipe 39, a first backflow pipe 41 for reversing the circulation of the decontamination liquid is connected in an annular shape at a position sandwiching the temporary pump 25 and the nozzle valve 47. The first backflow pipe 41 is provided with a first backflow valve 42 that is closed when the decontaminating liquid circulates in the forward direction. Further, the second backflow pipe 62 having the second check valve 61 is connected to the right side PLR middle pipe 34R and the third temporary pipe 56 in parallel with the temporary pump 25. The third backflow valve 63 is provided in the third temporary pipe 56 between the connection point to the second backflow pipe 62 and the connection point to the first temporary pipe 39.

Further, the head spray pipe connecting pipe 44 connected to the RHR head spray pipe 26 branches from the first temporary pipe 39. The head spray pipe connecting pipe 44 is provided with a head spray pipe connecting valve 46. Further, in the first temporary pipe 39, a nozzle valve 47 is provided between the connection point to the right side PLR middle pipe 34R and the connection point to the head spray pipe connection pipe 44.

The RHR head spray pipe 26 connected to the head spray pipe connecting pipe 44 is originally connected to the top lid cooling spray nozzle 1, but the configuration of the decontamination implementation device 100A includes the top lid cooling spray nozzle 1 and the top lid instrumentation nozzle. It is connected to any one or two of 2 and the vent nozzle 3. One of the upper lid cooling spray nozzle 1, the upper lid instrumentation nozzle 2, and the vent nozzle 3 to which the RHR head spray tube 26 is not connected has the reactor pressure when the decontamination liquid is injected into the reactor pressure vessel 13. It is used as an air vent for discharging a gas such as air in the container 13 or discharging a gas generated when the reducing agent as a chemical injected into the decontamination liquid is decomposed.

Further, the reactor pressure vessel 13 is connected to an exhaust gas treatment system 64 that discharges the gas generated in the reactor pressure vessel 13. The exhaust gas treatment system 64 includes a gas treatment mechanism 65, and when ozone gas is injected into the decontamination liquid as an oxidant, the gas generated in the reactor pressure vessel 13 is treated by the gas treatment mechanism 65 and discharged.

The heat exchanger 49 of the temporary system 300A heats or cools the decontamination liquid flowing through the temporary system 300A to adjust the temperature to a predetermined temperature. Further, the drug preparation unit 50 of the temporary system 300A supplies the drug to the decontamination liquid flowing in the third temporary pipe 56 by operating the preparation pump 45, and adjusts the content of the drug in the decontamination liquid. The chemicals are an oxidizing agent and a reducing agent, ozone or permanganate is used as the oxidizing agent, and an organic acid is used as the reducing agent. When the oxidizing agent is ozone, ozone is injected into the decontamination liquid from the ozone generator 51 via the gas mixer 75.

Here, the organic acid as the reducing agent is preferably at least one of oxalic acid, formic acid, virbic acid, glyoxylic acid, malonic acid, maleic acid, citric acid and ascorbic acid. That is, in chemical decontamination, oxalic acid is usually preferably used as a reducing agent. Since this oxalic acid is a strong acid having a small acid dissociation constant (pKa) among the organic acids that can be decomposed, a decontamination effect can be obtained by using it at a relatively low concentration. However, oxalic acid may not be suitable for strains with a large amount of iron elution due to the low solubility of iron oxalate. In addition, since oxalic acid has a slow dissolution rate in water, it is difficult to dissolve oxalic acid at a high concentration.

Therefore, for example, when it is difficult to use oxalic acid, it is desirable to use an organic acid having solubility in water or a liquid organic acid in the temperature range from room temperature to the decontamination condition temperature. Examples of the organic acid having a relatively low acid dissociation constant (pKa) of about 3 or less and having the above-mentioned solubility in water or being in a liquid state include formic acid and pyruvate as monocarboxylic acids. There are glyoxylic acid and the like, dicarboxylic acids include malonic acid, tartaric acid, maleic acid and the like, and tricarboxylic acids include citric acid and the like. In order to obtain a higher decontamination effect, a plurality of these organic acids may be used as appropriate.

The purification system 57 of the temporary system 300A is operated when it is necessary to purify the decontamination liquid, and includes a decontamination agent decomposition unit 52, a filter 53, and an ion exchange unit 54. The decontamination agent decomposition unit 52 is, for example, an ultraviolet irradiation device that decomposes the decontamination agent with ultraviolet rays. The filter 53 removes insoluble components in the decontamination liquid. The ion exchange unit 54 removes the dissolved component, and uses, for example, two types of resin towers, a cation exchange resin tower and a mixed bed resin tower in which a cation exchange resin and an anion exchange resin are mixed. ..

The purification system 57 configured in this way is connected to a purification system pipe 58 provided with a purification valve 59 and a purification pump 55. The purification system pipe 58 is connected to the third temporary pipe 56 in an annular shape. When purification of the decontamination liquid is required, the purification valve 59 is opened, the purification pump 55 is activated, the decontamination liquid flowing through the third temporary pipe 56 is guided to the purification system pipe 58, and the purification system 57 is used. It is sequentially purified by the decontamination agent decomposition unit 52, the filter 53, and the ion exchange unit 54.

The decontamination implementation device 100A described above does not necessarily have to include all the configurations. Among the above configurations, it is sufficient that the configuration in which the decontamination implementation method according to each embodiment described below can be implemented is included. Further, the description of the above configuration does not limit the number and position of installation of each component device such as a valve and a pump arranged in the temporary system 300A of the decontamination execution device 100A, and the piping. For example, a valve or the like may be added to the above configuration as appropriate.

3. 3. Decontamination implementation method Next, the decontamination implementation method will be described with reference to FIGS. 2 and 3. FIG. 2 is an explanatory diagram illustrating a decontamination implementation method according to the first embodiment. Further, FIG. 3 is a flowchart showing a decontamination implementation method according to the first embodiment.

In the decontamination method, first, the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40 (S10). The closing plug 40 closes the steam outlet nozzle 27 from the inside of the reactor pressure vessel 13 when the air-water separator 18 and the steam dryer 19 are not present in the reactor pressure vessel 13. When the steam separator 18 and the steam dryer 19 are present in the reactor pressure vessel 13, the main steam pipe (not shown) connected to the steam outlet nozzle 27 is cut, and the cut point is closed by the plug 40. The steam outlet nozzle 27 is closed by closing the steam outlet nozzle 27. By closing the steam outlet nozzle 27, it is prevented that the decontamination liquid flows into the reactor pressure vessel 13 or is taken out of the reactor pressure vessel 13 through the steam outlet nozzle 27.

Next, using the temporary system 300A, the circulation path 401 is constructed so that the reactor pressure vessel 13 becomes the flow path of the decontamination liquid (S11). Here, this step S11 may be performed before step S10 by changing the order from the above-mentioned step S10. Further, in the first embodiment, as shown in FIG. 2, an example will be described in which the furnace bottom header pipe 32 is included in the circulation path 401 of the decontamination liquid and the PLR system 200 is not included in the circulation path 401.

Specifically, for example, the third check valve 63, the nozzle valve 47, the head spray pipe connecting valve 46, and the bottom valve 69 provided in the bottom header pipe 32 are opened. On the other hand, the PLR suction valve 22, the PLR discharge valve 23, the left / right connecting valve 37, the PLR middle valve 38, the first check valve 42, the second check valve 61, and the purification valve 59 are closed. The black-painted valve indicates the closed state, and the white-painted valve indicates the valve open state.

As a result, one or two of the temporary system 300A, the water supply nozzle 12, the core spray nozzle 15, one or two of the top lid cooling spray nozzle 1, the top lid instrumentation nozzle 2, and the vent nozzle 3, the reactor pressure vessel 13, and the control rod drive. A circulation path 401 is constructed around at least one of the mechanism housing 29, the neutron flux measurement housing 28, and the drain nozzle 30, and the temporary system 300A.

The fuel of the core 10 is carried out from the reactor pressure vessel 13 after the reactor is shut down. On the other hand, the in-core equipment such as the jet pump 16, the core shroud 11, the air-water separator 18, and the steam dryer 19 may be in a built-in state. However, the steam separator 18 and the steam dryer 19 may have already been carried out at the time of decontamination.

Next, the decontamination liquid or the water-filled water is injected into the reactor pressure vessel 13 (S12). This decontamination liquid is obtained by injecting a drug into water-filled water from the drug preparation unit 50, and is one of the top lid cooling spray nozzle 1, the top lid instrumentation nozzle 2, and the vent nozzle 13 via the RHR head spray tube 26. It is supplied into the reactor pressure vessel 13 from one or two, and further from at least one of the water supply nozzle 12 and the core spray nozzle 15. The decontamination liquid from the water supply nozzle 12 is sprayed by the water supply spray ring 12A, and the decontamination liquid from the core spray nozzle 15 is sprayed and supplied toward the inner wall surface of the reactor pressure vessel 13 by the core spray ring 15A. The decontamination liquid is supplied and stored in the reactor pressure vessel 13 to the same height as the steam outlet nozzle 27 or to a position above the steam outlet nozzle 27.

Next, the connection valve with the temporary system 300A is opened (S13). For example, the bottom valve 69 is opened as a connection valve, and the decontamination liquid stored in the reactor pressure vessel 13 is drawn out to the bottom header pipe 32. Sludge, which is an insoluble component, is often deposited on the bottom of the reactor pressure vessel 13. This sludge obstructs the flow of the decontamination liquid at the bottom of the reactor pressure vessel 13, causes the linear flow velocity of the decontamination liquid to be insufficient, and in addition, causes the decontamination liquid to come into contact with the bottom of the reactor pressure vessel 13. Also inhibits.

Therefore, the accumulated sludge is directly collected at the control rod drive mechanism housing 29, the neutron flux measurement housing 28, and the drain nozzle 30 at least one of the decontamination liquid collection points in the second temporary pipe 48. By collecting the sludge in this way, in addition to adding a linear flow velocity to the decontamination liquid at the bottom of the reactor pressure vessel 13, the decontamination liquid is brought into contact with the bottom of the reactor pressure vessel 13 for decontamination. It becomes possible to improve the dyeing efficiency.

Next, the decontamination liquid extracted from the furnace bottom header pipe 32 is extracted to the temporary system 300A including the second temporary pipe 48 and recovered (S14). The recovered decontamination liquid is heated or cooled by the heat exchanger 49 while flowing through the third temporary pipe 56 of the temporary system 300A to adjust the temperature. At the same time, the drug (reducing agent, reducing agent) prepared by the drug preparation unit 50 is injected into the decontamination solution by the preparation pump 45, and the content of the drug in the decontamination solution is adjusted. In particular, when the oxidizing agent is ozone, ozone is injected from the ozone generator 51 into the decontamination liquid via the gas mixer 75.

Next, with the steam outlet nozzle 27 of the reactor pressure vessel 13 closed, the temporary pump 25 of the temporary system 300A is operated, and the decontamination liquid from the temporary system 300A is applied to the first temporary pipe 39 and the RHR head. It is returned to the reactor pressure vessel 13 via the spray pipe 26, and the decontamination liquid is circulated in the circulation path 401 including the temporary system 300A and the reactor pressure vessel 13 to chemically decontaminate the inside of the reactor pressure vessel 13 ( S15).

The decontamination liquid that has flowed through the first temporary pipe 39 is supplied from the water supply spray ring 12A and the core spray ring 15A to the reactor pressure vessel 13 and returned via at least one of the water supply nozzle 12 and the core spray nozzle 15. .. Further, the decontamination liquid flowing through the RHR head spray tube 26 is supplied into the reactor pressure vessel 13 from any one or two of the upper lid cooling spray nozzle 1, the upper lid instrumentation nozzle 2, and the vent nozzle 3 and returned. Will be done.

Further, when the decontamination liquid circulates in the circulation path 401, it is preferable to adjust the water flow time of the decontamination liquid according to the flow rate of the decontamination liquid with respect to the target site of chemical decontamination. Normally, in the chemical decontamination of a plant in service, it is required to carry out decontamination in as short a time as possible in order to reduce the influence on the subsequent inspection work process. However, in the case of decommissioning, there are few time constraints, so it is possible to take a long water flow time for the part where the linear flow velocity of the decontamination liquid becomes slow. Therefore, in the first embodiment, the output of the temporary pump 25 is controlled to lengthen the water flow time of the decontamination liquid at the portion where the linear flow velocity of the decontamination liquid becomes slow, and conversely, the linear flow velocity of the decontamination liquid is increased. Adjust the water flow time of the decontamination solution to be shorter in the area where the speed becomes faster.

Further, in the chemical decontamination, it is desirable to decontaminate while alternately switching between the oxidation step using an oxidizing agent for the decontamination liquid and the reducing step using a reducing agent for the decontamination liquid. As the oxidizing agent, for example, ozone or permanganate is used. Further, as the reducing agent, it is desirable to use at least one organic acid of oxalic acid, formic acid, virbic acid, glyoxylic acid, malonic acid, maleic acid, citric acid and ascorbic acid. In the decontamination implementation method according to each embodiment for decommissioning before decommissioning, it is less necessary to consider the influence on the constituent materials with which the decommissioning liquid comes into contact. Therefore, the chemicals (oxidizing agent, reducing agent) to be added to the decontamination liquid may be selected in consideration of the decontamination effect or ease of handling.

It is determined whether or not the decontamination liquid needs to be purified during the chemical decontamination (S16), and when purifying, the purification valve 59 is opened and the purification pump 55 is started to decontaminate. The liquid is guided to the purification system pipe 58 (S17). The decontamination liquid guided to the purification system pipe 58 is sequentially purified by the decontamination agent separation unit 52, the filter 53, and the ion exchange unit 54 of the purification system 57. The purified decontamination liquid is returned from the temporary system 300A to the reactor pressure vessel 13 and circulated through the circulation path 401 to continue decontamination (S15). For example, the decontamination liquid is supplied into the reactor pressure vessel 13 from the first temporary pipe 39 and the RHR head spray pipe 26.

In step S16, when it is not necessary to purify the decontamination liquid (NO), it is determined whether or not the chemical decontamination of the reactor pressure vessel 13 as the decontamination target has been sufficiently performed (S18). In step S18, when it is determined that the chemical decontamination of the reactor pressure vessel 13 has been sufficiently performed, the chemical decontamination is terminated, and when the chemical decontamination is not sufficient, steps S14 to S18 are sequentially carried out, and the circulation path. In 401, the decontamination liquid is circulated to continue the chemical decontamination of the reactor pressure vessel 13.

Since it is configured as described above, according to the first embodiment, the following effects (1) to (4) are obtained.
(1) Since the decontamination liquid is circulated and circulated in the circulation path 401 including the reactor pressure vessel 13 and the temporary system 300A in a state where the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40. The decontamination liquid does not flow to the main steam pipe (not shown) connected to the steam outlet nozzle 27. That is, the circulation path 401 is a reduced region in which a large-diameter main steam pipe does not exist. As a result, even if the temporary pump 25 of the temporary system 300A is installed in a limited space and has a small flow rate, the decontamination liquid can be efficiently circulated in the circulation path 401, and the reactor pressure vessel 13 can be circulated. Chemical decontamination can be carried out efficiently.

(2) When the decontamination liquid is circulated in the circulation path 401 including the reactor pressure vessel 13 and the temporary system 300A to chemically decontaminate the reactor pressure vessel 13, the temporary pump 25 of the temporary system 300A is used. The PLR pump 21 is never used. Therefore, it is possible to avoid the complexity of the decontamination work and the soaring decontamination cost caused by using the PLR pump 21.

(3) Chemical decontamination of the reactor pressure vessel 13 is carried out in a state where the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40. Therefore, the decontamination liquid is supplied into the reactor pressure vessel 13 from any one or two of the top lid cooling spray nozzle 1, the top lid instrumentation nozzle 2, and the vent nozzle 3 provided on the crown of the reactor pressure vessel 13. At this time, it is possible to reliably prevent the supplied decontamination liquid from flowing out of the reactor pressure vessel 13 from the steam outlet nozzle 27.

(4) In the chemical decontamination of the reactor pressure vessel 13, the liquid level of the decontamination liquid supplied into the reactor pressure vessel 13 is at the same level as the steam outlet nozzle 27 or at a position above the steam outlet nozzle 27. It is supplied to be. As a result, especially when the steam separator 18 and the steam dryer 19 are present in the reactor pressure vessel 13, these steam separator 98 and the steam dryer 19 are immersed in the decontamination liquid. Therefore, these air-water separator 18 and steam dryer 19 can be suitably decontaminated.

[II] Second Embodiment (FIG. 4)
FIG. 4 is an explanatory diagram illustrating a decontamination implementation method according to the second embodiment. In this second embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The difference between the decontamination method of the second embodiment and the first embodiment is that a circulation path 402 is constructed by using the same decontamination implementation device 100 as that of the first embodiment, and the circulation path 402 is circulated. The point is that the circulating decontamination liquid is flowed in the direction opposite to that of the first embodiment to reverse the circulation of the decontamination liquid. In the circulation path 402, the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40, and at least one of the temporary system 300A, the control rod drive mechanism housing 29, the neutron bundle measurement housing 28, and the drain nozzle 30. It is a route around the reactor pressure vessel 13, at least one of the water supply nozzle 12 and the core spray nozzle 15, and the temporary system 300A.

That is, when the decontamination liquid is circulated and circulated in the circulation path 402 including the reactor pressure vessel 13 and the temporary system 300A, the decontamination liquid in the reactor pressure vessel 13 is at least the water supply nozzle 12 and the water supply spray nozzle 15. The decontamination liquid in the temporary system 300A is extracted from one side and flows into the reactor pressure vessel 13 from at least one of the control rod drive mechanism housing 29, the neutron bundle measurement housing 28, and the drain nozzle 30.

In the second embodiment, the first check valve 42 and the second check valve 61, which were closed in the first embodiment, are opened in order to reverse the circulation of the decontamination liquid. On the other hand, the head spray pipe connecting valve 46, the nozzle valve 47, and the third check valve 63, which have been opened in the first embodiment, are closed. Also in the decontamination implementation method of the second embodiment, the steam outlet nozzle 27 is closed by the closing plug 40.

Depending on the open / closed state of the valve or the like, the decontamination liquid flows through the first backflow pipe 41 and the second backflow pipe 62 and circulates in the reverse direction as shown in FIG. That is, the decontamination liquid rises in the reactor pressure vessel 13 and is extracted from at least one of the water supply nozzle 12 and the core spray nozzle 15. By circulating the decontamination liquid through the first backflow pipe 41 and the second backflow pipe 62, the temporary pump 25 can be used for the reverse circulation of the decontamination liquid without changing the direction of the pumping water. ..

Further, in the case of reverse circulation of the decontamination liquid as described above, the entire amount of the decontamination liquid is transferred to the reactor pressure vessel 13 via at least one of the control rod drive mechanism housing 29, the neutron bundle measurement housing 28 and the drain nozzle 30. By flowing in from the bottom, it becomes possible to agitate the sludge accumulated on the bottom of the reactor pressure vessel 13 and promote the movement of the sludge.

Further, along with the inflow of the decontamination liquid from the bottom of the reactor pressure vessel 13, gas 43 is injected into the decontamination liquid from a bubbling device (not shown) set in the temporary system 300A to bubbling the decontamination liquid. However, the stirring of the decontamination liquid at the bottom of the reactor pressure vessel 13 may be strengthened to promote the movement of sludge accumulated at the bottom. The gas 43 to be supplied is preferably ozone gas as an oxidizing agent in the oxidizing step. This is because ozone gas exerts an effect as an oxidizing agent at the same time as promoting stirring of the decontaminating liquid.

On the other hand, in the reduction step, the gas 43 is preferably a gas having poor reactivity such as nitrogen. This is because the redox potential in the decontamination liquid may be controlled in order to control the decontamination effect during the reduction step. When the redox potential is not particularly controlled, the gas 43 may be air.

Further, since the decontamination method in each embodiment including the first and second embodiments is chemical decontamination performed before decommissioning, it is less necessary to consider the time required for chemical decontamination. Therefore, when the decontamination liquid is circulated and circulated in the circulation path 402, the decontamination liquid for the reactor pressure vessel 13 is extracted from at least one of the control rod drive mechanism housing 29, the neutron flux measurement housing 28, and the drain nozzle 30. And the inflow to at least one of the control rod drive mechanism housing 29, the neutron flux measurement housing 28, and the drain nozzle 30 may be alternately reversed and repeated. That is, the forward circulation of the decontamination liquid flowing through the circulation path 401 of the first embodiment and the reverse circulation of the decontamination liquid flowing through the circulation path 402 of the second embodiment are performed, for example, at regular time intervals. You may switch and repeat.

Since it is configured as described above, according to the second embodiment, in addition to the same effects as the effects (1) to (4) of the first embodiment, the following effects (5) and (6) are obtained. Play.

(5) The decontamination liquid is flowed from the second temporary pipe 48 of the temporary system 300A into the reactor pressure vessel 13 via at least one of the control rod drive mechanism housing 29, the neutron bundle measurement housing 28 and the drain nozzle 30. The sludge deposited on the bottom of the reactor pressure vessel 13, in particular, can be moved to effectively perform chemical decontamination of the bottom. In this case, by injecting the gas 43 into the decontamination liquid and causing it to hub ring, the stirring of the decontamination liquid in the reactor pressure vessel 13 is promoted, and the decontamination effect can be further improved.

(6) The forward circulation of the decontamination liquid flowing through the circulation path 401 of the first embodiment and the reverse circulation of the decontamination liquid flowing through the circulation path 402 of the second embodiment are alternately switched and repeated. You may. In this case, even in a place where the linear flow velocity of the decontamination liquid is not sufficient in the forward or reverse unidirectional circulation in the reactor pressure vessel 13, the linear flow velocity of the decontamination liquid is sufficient in the other direction circulation. By doing so, the decontamination effect can be improved.

[III] Third Embodiment (FIGS. 5 and 6)
FIG. 5 is an explanatory diagram illustrating a decontamination implementation method according to the third embodiment. In this third embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The decontamination method of the third embodiment is different from that of the first embodiment by opening the PLR suction valve 22, the left / right connecting valve 37, and the PLR middle valve 38, which were closed in the first embodiment. The point is that the reactor pressure vessel 13 and the PLR system 200 are targeted for decontamination by chemical decontamination. As a result, the circulation route 403A is obtained by adding a route for the temporary system 300A, the PLR system 200, the reactor pressure vessel 13, and the temporary system 300A to the decontamination route 401 of the first embodiment or the decontamination route 402 of the second embodiment. , 403B is constructed.

Generally, in a reactor plant scheduled to be decommissioned, the PLR pump 21 is shut down due to the shutdown of the reactor, and is usually in a state of being shut down for a long period of time thereafter. In the valve open state of the above-mentioned valves (PLR suction valve 22, left / right connecting valve 37, PLR middle valve 38), substantially the entire area of the PLR system 200 including the PLR pump 21 is connected to the circulation paths 403A and 403B through which the decontamination liquid flows. Become. The circulation path 403A shown in FIG. 5 is a temporary system 300A, a PLR system 200, and a reactor pressure vessel 13 in the circulation path 401 of the first embodiment in which the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40. , And a route around the temporary system 300A is added.

At this time, in order to sufficiently flow the decontamination liquid in the reactor pressure vessel 13, it is desirable to circulate the decontamination liquid in the PLR system 200. However, when the PLR pump 21 is stopped, the decontamination liquid is blocked by the PLR pump 21 and it becomes difficult to circulate in the PLR system 200. Therefore, the motor and the rotating body of the PLR pump 21 are removed, the opening is temporarily closed with a pressure resistant cap or the like, and the inside of the PLR pump 21 is used as a flow path for the decontamination liquid. As a result, the decontamination liquid that has flowed into the PLR system 200 from the reactor pressure vessel 13 via the recirculating water outlet nozzle 20 passes through the PLR pump 21 and is drawn out from the closing cap portion of the PLR pump 21 to the PLR bottom pipe 33. ..

Further, the decontamination liquid branched from the first temporary pipe 39 into the PLR middle pipe 34 flows into the PLR system 200 and then flows into the jet pump 16 from the recirculation water inlet nozzle 24 to drive the jet pump 16. It flows out into the reactor pressure vessel 13 by force. That is, in the third embodiment, most of the PLR system 200 is chemically decontaminated, and the flow of the decontaminating liquid in the reactor pressure vessel 13 is promoted by utilizing the driving force of the jet pump 16.

Further, FIG. 6 is an explanatory diagram showing a state in which the decontamination liquid is circulated in the reverse direction in the circulation path 403B in the decontamination implementation method according to the third embodiment. The circulation path 403B is provided in the circulation path 402 of the second embodiment in which the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40, and the temporary system 300A, the PLR system 200, the reactor pressure vessel 13, and the temporary connection are provided. A route around the system 300A is added.

In the reverse circulation of the decontamination liquid in the circulation path 403B, the PLR suction valve 22 or the PLR is in the open / closed state (FIG. 4) of the valve of the second embodiment in order to circulate the decontamination liquid in the PLR system 200. The discharge valve 23 is further opened (only the PLR discharge valve 23 is opened in FIG. 6). Further, as in the case of forward circulation of the decontaminating liquid in the third embodiment (FIG. 5), the left and right connecting valve 37 and the PLR middle valve 38 are opened (the PLR discharge valve 23 is opened in FIG. 6). Therefore, only the left and right connecting valves 37 are opened), and the decontamination liquid is circulated to most of the PLR system 200.

At this time, the decontamination liquid flows into the PLR system 200 from the PLR bottom pipe 33 via the second temporary pipe 48 of the temporary system 300A. Then, as in the case of forward circulation shown in FIG. 5, when the decontamination liquid is discharged in the reactor pressure vessel 13 by using the driving force of the jet pump 16, the PLR suction valve 22 is closed as described above. Then, the PLR discharge valve 23 is opened.

Since it is configured as described above, according to the third embodiment, in addition to the same effects as the effects (1) to (6) of the first and second embodiments, the following effect (7) is obtained. Play.

(7) By distributing the decontamination liquid of the temporary system 300A not only to the reactor pressure vessel 13 but also to the PLR system 200, the PLR system 200 can be chemically decontaminated. Then, the decontamination liquid decontaminated from the PLR system 200 is circulated toward the recirculating water inlet nozzle 24, so that the driving force of the jet pump 16 is used to stir the decontamination liquid in the reactor pressure vessel 13. Therefore, the decontamination efficiency can be improved.

[IV] Fourth Embodiment (FIGS. 7 and 8)
FIG. 7 is an explanatory diagram illustrating a decontamination implementation method according to the fourth embodiment. In this fourth embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The decontamination implementation device 100B that implements the decontamination implementation method of the fourth embodiment is different from the first embodiment in that the temporary pump 25 is located upstream of the purification system pipe 58 in the third temporary pipe 56 of the temporary system 300B. In the decontamination method using the decontamination device 100B, the circulation path 404A (FIG. 7) or the circulation path 404B (FIG. 8) is constructed by operating the temporary pump 25, respectively. The point is to carry out chemical decontamination of the reactor pressure vessel 13.

Here, as shown in FIG. 7, the circulation path 404A has at least the temporary system 300B, the water supply nozzle 12, and the core spray nozzle 15 in a state where the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40. On the other hand, one or two of the top lid cooling spray nozzle 1, the top lid instrumentation nozzle 2, and the vent nozzle 3, the reactor pressure vessel 13, the control rod drive mechanism housing 29, the neutron bundle measurement housing 28, and at least one of the drain nozzles 30 and This is a route that goes around the temporary system 300B. Further, as shown in FIG. 8, the circulation path 400B includes a temporary system 300B, a control rod drive mechanism housing 29, and a neutron bundle measurement housing in a state where the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40. It is a route around at least one of 28 and the drain nozzle 30, the reactor pressure vessel 13, at least one of the water supply nozzle 12 and the core spray nozzle 15, and the temporary system 300B.

In this fourth embodiment, for example, when it is not preferable to install the temporary pump 25 in the first temporary pipe 39 in relation to other components (not shown), the direction of the decontamination liquid in the reactor pressure vessel 13 is set. , The temporary pump 25 is moved to the upstream side of the purification system pipe 58 while maintaining the same as that of the first or second embodiment. In the temporary system 300B in the decontamination implementation device 100B of the fourth embodiment, the relative arrangement relationship between the first check valve 42, the second check valve 61, and the temporary pump 25 is the same as that of the first and second embodiments. It is maintained as in the case of the temporary system 300A.

The open / closed state of each valve in the temporary system 300B or the like when constructing the circulation path 404A is the same as that in the first embodiment, the head spray pipe connecting valve 46 and the third check valve 63 are opened, and the PLR middle valve 38, The first check valve 42 and the second check valve 61 are closed. Further, the open / closed state of each valve in the temporary system 300B or the like when constructing the circulation path 404B is the same as that in the second embodiment, and the PLR middle valve 38, the first check valve 42, and the second check valve 61 are opened. , The head spray pipe connecting valve 46 and the 31st check valve 63 are closed.

Since it is configured as described above, in the fourth embodiment, the installation position of the temporary pump 25 is set while maintaining the same effects as the effects (1) to (6) of the first and second embodiments. Can be changed.

[V] Fifth Embodiment (FIG. 9)
FIG. 9 is an explanatory diagram illustrating a decontamination implementation method according to the fifth embodiment. In the fifth embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The difference between the decontamination implementation device 100C that implements the decontamination implementation method of the fifth embodiment and the first and third embodiments is that the temporary system 300C of the decontamination implementation device 100C is connected to the second temporary pipe 48. The PLR bottom pipe 33 is not directly connected to the PLR system 200, but is connected to a bypass line 81 that bypasses the PLR pump 21. Therefore, in the decontamination implementation method of the fifth embodiment, the steam outlet nozzle 27 of the reactor pressure vessel 13 is decontaminated through the PLR system 200 in the circulation path 403 of the third embodiment closed by the closing plug 40. A circulation path 405 is constructed in which the dyeing liquid bypasses the PLR pump 21 and flows from the bypass line 81 to the second temporary pipe 48 via the bottom drain line 31.

In the above-mentioned third embodiment, it is necessary to temporarily close the PLR pump 21 in order to distribute the decontamination liquid to the PLR system 200 without operating the PLR pump 21. However, depending on the dismantling status of the PLR pump 21, the motor or the like may not have been removed yet and may not be temporarily closed. Therefore, in the fifth embodiment, by bypassing the PLR pump 21 by the bypass line 81, the reactor pressure vessel 13 and the PLR system 200 are chemically decontaminated regardless of the dismantling status of the PLR pump 21 after the reactor is shut down. To carry out. Further, by using this bypass line 81, it is possible to carry out chemical decontamination without any special treatment for the PLR pump 21.

Specifically, for example, a sluice valve and a temporary hose are connected to the suction side and the discharge side of the PLR pump 21 to form a bypass line 81. As shown in FIG. 9, this sluice valve may be a modified PLR intake valve 22 and PLR discharge valve 23 into a three-way valve.

Since it is configured as described above, in the fifth embodiment, the same effects as the effects (1) to (7) of the first to third embodiments are obtained, and the PLR pump 21 is disassembled regardless of the disassembly status. Chemical decontamination can be carried out on the reactor pressure vessel 13 and the PLR system 200 without any special treatment on the PLR pump 21.

[VI] Sixth Embodiment (FIG. 10)
FIG. 10 is an explanatory diagram illustrating a decontamination implementation method according to the sixth embodiment. In this sixth embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The decontamination implementation device 100D that implements the decontamination implementation method of the sixth embodiment is different from the first embodiment in that the temporary system 300D of the decontamination implementation device 100D is at least the water supply nozzle 12 and the core spray nozzle 15. The assisting pump 83 has an assisting path 84 connecting one side and the left side PLR system 200L, an assisting pump 83 connected to the assisting path 84, and an assisting valve 86 arranged in the left side PLR bottom pipe 33L. It is a point that the linear flow velocity of the decontamination liquid circulating in the left side PLR system 200L is increased by the operation.

Therefore, in the sixth embodiment, the reactor pressure vessel 13 and the recirculating water outlet nozzle are mainly connected to the circulation path 401 of the first embodiment in which the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40. 20, PLR system 200, assistive path 84, at least one of the water supply nozzle 12 and the core spray nozzle 15, and the circulation path 406 with the addition of a path around the reactor pressure vessel 13 are constructed.

The reason for installing the assist pump 83 and the like is as follows. That is, since the reactor pressure vessel 13 has a very large capacity, a sufficient flow velocity can be obtained with the temporary pump 25 installed at one place when performing chemical decontamination on the path including the reactor pressure vessel 13. May not be. In particular, in the left PLR system 200L which is separated from the temporary pump 25 and inflows the decontamination liquid through the left and right connecting pipes 34C (FIG. 5), a sufficient linear flow velocity cannot be obtained for the decontamination liquid. Therefore, the auxiliary pump 83 directly assists the distribution of the decontamination liquid in the left PLR system 200L.

At this time, it is preferable to close the assist valve 86 so that all the decontamination liquid flowing through the left PLR system 200L is guided into the reactor pressure vessel 13 from at least one of the water supply nozzle 12 and the core spray nozzle 15. .. Since the distribution of the decontamination liquid in the left PLR system 200L is mainly controlled by the assist pump 83, FIG. 10 shows the left and right connecting pipes 34C and the left PLR middle pipe 34L shown in the third embodiment and the like. Is omitted. However, the distribution of the decontamination liquid by the left and right connecting pipes 34C and the PLR middle pipes 34 (34L, 34R) may be appropriately maintained.

Since it is configured as described above, according to the sixth embodiment, the effects of the first and third embodiments (1) to (4) and (7) are exhibited, and the decontamination liquid is obtained. By assisting the linear flow velocity of the left side PLR system 200L in which the linear flow velocity is insufficient by the assisting pump 83, the decontamination of the left side PLR system 200L can be sufficiently carried out and the decontamination time can be shortened.

[VII] Seventh Embodiment (FIG. 11)
FIG. 11 is an explanatory diagram illustrating a decontamination implementation method according to the seventh embodiment. In the seventh embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The difference between the decontamination implementation device 100E that implements the decontamination implementation method of the seventh embodiment from the first and second embodiments is that the first backflow pipe 41 (FIG. 1) was deleted, and a backflow pump 87 was installed in the second backflow pipe 62, and the decontamination liquid was circulated in the reverse direction in the circulation path 407 by the operation of the backflow pump 87.

In the second embodiment, the decontamination liquid was circulated through the first backflow pipe 41 (FIG. 4 and the like) and the second backflow pipe 62, and the decontamination liquid was circulated in the reverse direction. However, depending on the arrangement of other devices, the first backflow pipe 41 may not be able to be connected to the first temporary pipe 39. Therefore, in the temporary system 300E in the decontamination implementation device 100E of the seventh embodiment, the backflow pump 87 is arranged in the second backflow pipe 62, and the backflow pump 87 is used to provide the reactor pressure vessel as in the second embodiment. The decontamination liquid is circulated in the 13 from the lower side to the upper side in the opposite direction.

Further, in the seventh embodiment, in order to guide all the decontaminating liquid flowing into the PLR middle pipe 34 to the second backflow pipe 62, a fourth backflow valve 88 is arranged in the PLR middle pipe 34. Further, a pump shutoff valve 78 is arranged on the downstream side of the temporary pump 25 in the first temporary pipe 39. The pump shutoff valve 78 is closed when the decontaminating liquid is circulated in the reverse direction.

Therefore, in the circulation path 407, the third temporary pipe 56 and the second temporary pipe 48 of the temporary system 300E and the control rod drive mechanism housing 29 are in a state where the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40. And at least one of the neutron bundle measurement housing 28 and the drain nozzle 30, at least one of the reactor pressure vessel 13, the water supply nozzle 12, and the core spray nozzle 15, the first temporary pipe 39, the second backflow pipe 62, and the temporary system of the temporary system 300E. It is a route around the third temporary pipe 56 of 300E.

Since it is configured as described above, according to the seventh embodiment, the decontamination liquid circulates in the circulation path 407 in the direction opposite to that of the first embodiment and circulates in the first backflow pipe 41. The effect similar to the effect (5) and (6) of the second embodiment is obtained without using.

[VIII] Eighth embodiment (FIG. 12)
FIG. 12 is an explanatory diagram illustrating a decontamination implementation method according to the eighth embodiment. In the eighth embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The decontamination implementation device 100F that implements the decontamination implementation method of the eighth embodiment is different from the first embodiment in that, in addition to the reactor pressure vessel 13 and the PLR system 200 as decontamination targets, the CUW system and the RHR. The point is that at least one peripheral system that allows circulation of the decontamination solution, including the system, is included.

In this eighth embodiment, the reactor pressure vessel 13, the PLR system 200 and the peripheral system are isolated from each other to form a circulation path 408 as a separate water flow area. Also in this circulation path 408, the steam outlet nozzle 27 of the reactor pressure vessel 13 is closed by the closing plug 40. Further, the temporary system 300F of the decontamination implementation device 100F is provided with a platform 89 that is directly or indirectly connected to all the water flow areas. This platform 89 is provided with a heat exchanger 49, a drug preparation unit 50, an ozone generator 51, a purification system 57, a purification system pipe 58, and a temporary pump 25, and manages the state of the decontamination liquid to purify it. Control the supply and return of decontamination liquid to each water flow area.

For example, the platform 89 is configured as a closed circulation path by connecting the first temporary pipe 39 and the second temporary pipe 48 to the platform pipe 91. In order to form this closed circulation path, a closed circulation configuration valve 92 and a closed circulation open valve 93 are provided at each connection portion between the platform 89 and the second temporary pipe 48.

The platform 89 is provided with a decontamination liquid supply header 94a and a decontamination liquid return header 94b. Branch pipes connected to each water flow area are connected to these headers 94 (94a, 94b). Each of the branch pipes is provided with a selection valve 98 (98a to 98f) that adjusts the water flow to each branch pipe and selects a water flow area to be decontaminated.

The decontamination liquid is supplied to the selected water passage area from the decontamination liquid supply header 94a to decontaminate the water passage area. When the decontamination liquid is supplied from the decontamination liquid supply header 94a to the water flow area, the supply valve 97 provided between the decontamination liquid supply header 94a and the decontamination liquid return header 94b is closed. By closing the supply valve 97, the decontamination liquid flowing through the platform pipe 91 is blocked, and all of the flowing decontamination liquid flows into the decontamination liquid supply header 94a. The decontamination liquid circulated in the water flow area and decontaminated is returned to the platform 89 from the decontamination liquid return header 94b. By switching the selection valve 98 one after another, it becomes possible to sequentially decontaminate each water flow area.

By the way, in the case of sequentially decontaminating each water flow area in this way, if the water flow area such as the reactor pressure vessel 13 having a high dose rate is initially decontaminated, the platform 89 is immediately contaminated to a high level. In this case, in a water flow area where the dose rate is low, a liquid having a high radioactive concentration may accumulate in the stagnant part of the flow. For example, if a water flow area such as a PLR system with a high dose rate is decontaminated and then a water flow area with a low dose rate is decontaminated, the contamination accumulated in the water flow area with a high dose rate may spread. .. Therefore, it is preferable to carry out chemical decontamination for each water flow area in order from the area with low contaminated radioactivity to the area with high contaminated radioactivity.

In addition, the required water flow rate of the reactor pressure vessel 13 is an order of magnitude larger than the capacity of other water flow areas. Therefore, when decontaminating other decontamination targets after decontaminating the reactor pressure vessel 13 at the initial stage, it is necessary to drain a large amount of the decontamination liquid. Since this wastewater requires decomposition treatment and purification treatment of the decontamination agent, a large amount of time is required for these treatments.

On the other hand, if decontamination is carried out sequentially from the water flow area where the decontamination capacity is small and the amount of contaminated radioactivity is low, in the reduction step of the final cycle, the radioactivity and the eluted metal are to some extent by passing water to the cation exchange resin. It will be enough if you remove it. In other words, by decontaminating from a system with a small decontamination capacity and a low amount of contaminated radioactivity, water and chemicals can be added to the next decontamination target without decomposing the decontaminating agent and performing final purification. Decontamination can be transferred. Therefore, in the eighth embodiment, decontamination is sequentially performed from the water flow area having a small decontamination capacity and a low amount of contaminated radioactivity.

Further, it is desirable that the platform pipe 91 is provided with a buffer tank 99 in order to maintain a decontamination liquid having a liquid level and a liquid amount sufficient for decontaminating the water passage area to be decontaminated. The buffer tank 99 is provided with a buffer valve 96 in order to perform buffering only when necessary. The platform 89 is not limited to the above-mentioned arrangement relationship as long as it has a configuration that exhibits the same function. For example, the connection position of the platform pipe 91, the header 94, and the position of the buffer tank 99 may be appropriately changed in consideration of the arrangement with other devices.

Since it is configured as described above, according to the eighth embodiment, the effects of the first and third embodiments (1) to (4) and (7) are exhibited, and the following effects are obtained. Play (8) and (9).

(8) Since the reactor pressure vessel 13, PLR system 200 and peripheral systems to be decontaminated are separated and divided into small separate water flow areas, the decontamination liquid is decontaminated even when the flow rate of the temporary pump 25 is small. The decontamination effect can be improved by increasing the linear flow velocity of.

(9) Since chemical decontamination is carried out sequentially from the water flow area where the amount of contaminated radioactivity is low and the decontamination capacity is small, decontamination of the next water flow area can be performed without decomposing the decontaminating agent or performing final purification. The transition is possible, and as a result, chemical decontamination can be carried out efficiently.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention, and their replacements and changes can be made. Is included in the scope and gist of the invention, as well as the invention described in the claims and the equivalent scope thereof.

1 ... Top lid cooling spray nozzle, 2 ... Top lid instrument nozzle, 3 ... Vent nozzle, 10 ... Core, 12 ... Water supply nozzle (1st nozzle), 13 ... Reactor pressure vessel, 15 ... Core spray nozzle (1st nozzle) , 25 ... Temporary pump, 27 ... Steam outlet nozzle, 28 ... Neutral bundle measurement housing (second nozzle), 29 ... Control rod drive mechanism housing (second nozzle), 30 ... Drain nozzle (second nozzle), 39 ... First Temporary piping, 40 ... Closing plug, 43 ... Gas, 48 ... Second temporary piping, 49 ... Heat exchanger (temperature regulator), 50 ... Drug preparation section (drug supply section), 51 ... Ozone generator (drug supply section) ), 100A-100F ... Decontamination implementation device, 300A-300F ... Temporary system, 401, 402, 403A, 403B, 404A, 404B, 405-407 ... Circulation route.

Claims (16)

In a decontamination method in which a reactor pressure vessel or a system including this reactor pressure vessel is decontaminated and chemically decontaminated.
A step of closing at least one of the steam outlet nozzle and the main steam pipe connected to the steam outlet nozzle,
A temporary system in which the first nozzle provided in the reactor pressure vessel and the second nozzle provided below the reactor pressure vessel below the first nozzle are installed outside the reactor pressure vessel is provided. A step of constructing a circulation path including the first nozzle, the reactor pressure vessel, the second nozzle and the temporary system by connecting via the step.
It has a step of circulating the decontamination liquid in the circulation path, and has.
The temporary system includes a temporary pump that circulates the decontamination liquid in the circulation route, a drug supply unit that supplies a drug to the decontamination liquid, a temperature regulator that adjusts the temperature of the decontamination liquid in the circulation route, and the like. It is provided with a first temporary pipe connecting the temporary system and the first nozzle, and a second temporary pipe connecting the temporary system and the second nozzle.
The first temporary pipe is provided with the temporary pump that gives a flow in only one direction and a plurality of valves connected in parallel with the temporary pump, and by switching the opening and closing of the plurality of valves, in the circulation path. By reversing the circulation of the decontamination liquid ,
The decontamination target of the chemical decontamination further includes at least one peripheral system of the reactor cooling material purification system and the residual heat removal system, and the reactor pressure vessel and the at least one peripheral system are separated from each other and individually passed. A decontamination method comprising a step of making a water area, wherein the chemical decontamination is sequentially carried out from the water flow area having a low contaminated radioactivity amount and a small decontamination capacity . The first aspect of claim 1, wherein in the step of closing at least one of the steam outlet nozzle and the main steam pipe connected to the steam outlet nozzle, the main steam pipe is cut and the cut portion is closed. The decontamination implementation method described. The decontamination implementation method according to claim 1 or 2, further comprising a step of draining the decontamination liquid stored in the closed main steam pipe to the temporary system. The first nozzle includes at least one of a water supply nozzle, a core spray nozzle, and a top lid cooling spray nozzle.
The second nozzle includes at least one of a control rod drive mechanism housing, a neutron flux measurement housing and a drain nozzle.
In the step of circulating and circulating the decontamination liquid in the circulation path, the decontamination liquid in the reactor pressure vessel is extracted from the second nozzle, and the decontamination liquid in the temporary system is discharged from the first nozzle to the reactor. The decontamination method according to any one of claims 1 to 3, wherein the liquid is flowed into a pressure vessel. With the air-water separator and steam dryer present inside the reactor pressure vessel, the decontamination liquid was applied to the reactor pressure vessel from at least one of the water supply nozzle as the first nozzle and the core spray nozzle. The decontamination according to any one of claims 1 to 4, further comprising a step of inflowing and spraying from the top lid cooling spray nozzle as the first nozzle to the air-water separator and the steam dryer. Implementation method. The first nozzle includes at least one of a water supply nozzle and a core spray nozzle.
The second nozzle includes at least one of a control rod drive mechanism housing, a neutron flux measurement housing and a drain nozzle.
In the step of circulating and circulating the decontamination liquid in the circulation path, the decontamination liquid in the reactor pressure vessel is extracted from the first nozzle, and the decontamination liquid in the temporary system is discharged from the second nozzle to the reactor. The decontamination method according to any one of claims 1 to 3, wherein the liquid is flowed into a pressure vessel. The first temporary pipe is connected to a first nozzle or a pipe connected to the first nozzle, and the second temporary pipe is connected to a second nozzle or a pipe connected to the second nozzle. The decontamination implementation method according to any one of claims 1 to 6. One of claims 1 to 7, wherein the step is to inject the decontamination liquid into the reactor pressure vessel at the same height as the steam outlet nozzle or at a position above the steam outlet nozzle. Decontamination implementation method described in. The step of circulating and circulating the decontamination liquid in the circulation path is characterized in that the extraction of the decontamination liquid from the second nozzle to the reactor pressure vessel and the inflow into the second nozzle are alternately reversed. The decontamination implementation method according to any one of claims 1 to 8 . The step of circulating and circulating the decontamination liquid in the circulation path is characterized in that a gas is supplied to the decontamination liquid flowing into the reactor pressure vessel from the second nozzle to bubbling the decontamination liquid. Item 9. The decontamination method according to any one of Items 1 to 9 . Claims 1 to 1, wherein in the step of circulating and circulating the decontamination liquid in the circulation path, the water flow time of the decontamination liquid is adjusted according to the flow velocity of the decontamination liquid flowing through the decontamination target. The decontamination implementation method according to any one of 10 . In a decontamination machine that performs chemical decontamination of a reactor pressure vessel or a system including this reactor pressure vessel as a decontamination target.
A steam outlet nozzle and a closing plug that closes at least one of the main steam pipes connected to the steam outlet nozzle.
A first nozzle installed outside the reactor pressure vessel and provided in the reactor pressure vessel and a second nozzle provided below the reactor pressure vessel below the first nozzle are connected and circulated. Has a temporary system to build a route,
The temporary system includes a temporary pump that circulates the decontamination liquid in the circulation route, a drug supply unit that supplies a drug to the decontamination liquid, a temperature regulator that adjusts the temperature of the decontamination liquid in the circulation route, and the temporary installation. It is provided with a first temporary pipe connecting the system and the first nozzle, and a second temporary pipe connecting the temporary system and the second nozzle.
The first temporary pipe is provided with the temporary pump that gives a flow in only one direction and a plurality of valves connected in parallel with the temporary pump, and by switching the opening and closing of the plurality of valves, in the circulation path. By reversing the circulation of the decontamination liquid ,
The decontamination target of the chemical decontamination further includes at least one peripheral system of the reactor cooling material purification system and the residual heat removal system, and the reactor pressure vessel and the at least one peripheral system are separated from each other and individually passed. An apparatus for carrying out decontamination, wherein the chemical decontamination is sequentially carried out from the water passage area having a low contaminated radioactivity amount and a small decontamination capacity in a water area . The decontamination implementation device according to claim 12 , wherein the closing plug is a closing plug that closes a cut portion where the main steam pipe is cut. The first temporary pipe is connected to the first nozzle or a pipe connected to the first nozzle, and the second temporary pipe is connected to the second nozzle or a pipe connected to the second nozzle. The decontamination performing apparatus according to claim 12 or 13 . The first nozzle includes at least one of a water supply nozzle and a core spray nozzle.
The decontamination implementation device according to any one of claims 12 to 14 , wherein the second nozzle includes at least one of a control rod drive mechanism housing, a neutron flux measurement housing, and a drain nozzle. The decontamination implementation device according to any one of claims 12 to 15 , wherein the temporary system includes a bubbling device that supplies a gas to the decontamination liquid to bubbling the decontamination liquid.

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