JP2021096189A - Decontamination implementation method and decontamination implementation apparatus - Google Patents

Abstract

To provide a decontamination implementation technique capable of improving decontamination effect on chemical decontamination of a reactor pressure vessel.SOLUTION: A decontamination implementation method includes the steps of: connecting a temporary system 4 to upper facilities 12, 15, and 27 provided above at least the vertical center of a reactor pressure vessel 2 and lower facilities 28, 29 and 30 provided below the upper facilities 12, 15 and 27; circulating a decontamination liquid in a circulation path structured with the reactor pressure vessel 2 and temporary system 4 by a temporary pump 25 provided for the temporary system 4; and using the upper facilities 12, 15 and 27 and lower facilities 28, 29 and 30 to put the decontamination liquid in and out of the reactor pressure vessel 2, and changing modes of a flow in the reactor pressure vessel 2.SELECTED DRAWING: Figure 12

Description

Embodiments of the present invention relate to a decontamination method and a decontamination device.

In the decommissioning of nuclear reactors, chemical decontamination is carried out using a decontamination liquid before dismantling the reactor. This chemical decontamination aims to reduce the exposure of workers during the dismantling of a nuclear reactor and to reduce the radioactivity level of waste generated by the dismantling.

Japanese Patent No. 6467080

Even if the decontamination liquid is introduced into the reactor from the upper part of the reactor pressure vessel, the decontamination liquid is not sufficiently sprayed into the inside of the structure such as the dryer, separator, jet pump, etc. It may run down the wall surface or hit the side surface of the structure. Further, even if the inside of the furnace is filled with the decontamination liquid, if the decontamination liquid is not sufficiently circulated, contaminated fine particles may remain in the furnace. In such a case, the effect of chemical decontamination cannot be sufficiently obtained.

An embodiment of the present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a decontamination technique capable of improving the decontamination effect of chemical decontamination of a reactor pressure vessel. ..

In the decontamination method according to the embodiment of the present invention, the temporary system is connected to the upper equipment provided at least above the center of the reactor pressure vessel in the vertical direction and the lower equipment provided below the upper equipment. The step of circulating the decontamination liquid in the circulation path constructed by the reactor pressure vessel and the temporary system by the temporary pump provided in the temporary system, and the upper equipment and the lower equipment are used. A step of moving the decontamination liquid in and out of the reactor pressure vessel to switch the mode of the flow inside the reactor pressure vessel is included.

An embodiment of the present invention provides a decontamination technique capable of improving the decontamination effect of chemical decontamination of a reactor pressure vessel.

The schematic block diagram which shows the decontamination execution apparatus of the 1st decontamination mode. The longitudinal side view which shows the reactor pressure vessel of the 1st decontamination mode corresponding to FIG. The schematic block diagram which shows the decontamination execution apparatus of the 2nd decontamination mode. Longitudinal side view showing the reactor pressure vessel of the second decontamination mode corresponding to FIG. The schematic block diagram which shows the decontamination execution apparatus of the 3rd decontamination mode. The longitudinal side view which shows the reactor pressure vessel of the 2nd decontamination mode corresponding to FIG. The schematic block diagram which shows the decontamination execution apparatus of the 4th decontamination mode. Longitudinal side view showing the reactor pressure vessel of the second decontamination mode corresponding to FIG. 7. Cross-sectional plan view showing a reactor pressure vessel. Explanatory drawing which shows the example of housing assembly. Longitudinal side view showing a reactor pressure vessel during bubbling. The flowchart which shows the decontamination execution method.

Hereinafter, the decontamination method and the embodiment of the decontamination device will be described in detail with reference to the drawings.

Reference numeral 1 in FIG. 1 is the decontamination implementation device of the present embodiment. This decontamination execution device 1 is used for decontaminating the reactor pressure vessel 2 provided in the nuclear power plant. In the decommissioning of nuclear power plants, fuel is taken out from the reactor after the shutdown, and then decontamination before dismantling the primary reactor system is carried out. In this embodiment, chemical decontamination using a decontamination liquid is carried out.

The primary reactor system is the reactor pressure vessel 2 (RPV: Reactor Presser Vessel), the reactor recirculation system 3 (PLR system: Primary Loop Recirculation System), and the reactor coolant purification system (CUW: Reactor Water Clean-). It includes an Up System) and a Residual Heat Removal System (RHR).

In the decontamination implementation method of the present embodiment, chemical decontamination of a boiling water reactor (BWR) as a nuclear power plant will be described. The decontamination method of the present embodiment may be applied to an advanced boiling water reactor (ABWR), a pressurized water reactor (PWR), or the like.

First, with reference to FIG. 1, the reactor pressure vessel 2 provided in the boiling water reactor, the reactor recirculation system 3, and the basic structure around them will be described. In addition, the actions that passively occur during normal operation, such as the flow of steam and reactor water (coolant), will be described. In FIG. 1, the main (existing) system is shown by a broken line, and the temporary system 4 constructed for decontamination is shown by a solid line. Further, for the sake of understanding, the illustration of the other main system connected to the reactor pressure vessel 2 is omitted.

Inside the reactor pressure vessel 2, a core 10 in which nuclear fuel is arranged is provided. In a boiling water reactor, a core shroud 11 surrounding the core 10 is provided. A down cam 14 which is an annular space is formed between the outer peripheral surface of the core shroud 11 and the inner peripheral surface of the reactor pressure vessel 2. For example, 16 or 20 jet pumps 16 are arranged in a ring shape at predetermined intervals in a plan view on the downcomer 14.

A shroud head 17 covering the upper plenum of the core is provided above the core 10. A steam separator 18 is provided above the shroud head 17. Further, a steam dryer 19 is provided above the steam separator 18.

A head spray nozzle 13 is arranged on the crown (ceiling) of the reactor pressure vessel 2. An RHR head spray tube 26 extending to the outside of the reactor pressure vessel 2 is connected to the head spray nozzle 13. The head spray nozzle 13 can spray a liquid such as a primary coolant inside the reactor pressure vessel 2.

Two or three reactor recirculation systems 3 are provided on the outside of the reactor pressure vessel 2. The primary coolant flows into the reactor recirculation system 3 from the lower part of the downcomer 14 inside the reactor pressure vessel 2 through the recirculation water outlet nozzle 20. The inflowed primary coolant is boosted by the PLR pump 21 provided in the reactor recirculation system 3. The flow rate of the primary coolant flowing into the PLR pump 21 is adjusted by the PLR suction valve 22 provided on the suction side and the PLR discharge valve 23 provided on the discharge side of the PLR pump 21, respectively.

The primary coolant that has flowed through the reactor recirculation system 3 is guided to the jet pump 16 via the recirculation water inlet nozzle 24, is ejected from the nozzle of the jet pump 16 as a jet drive fluid, and enters the furnace above the downcomer 14. A certain primary coolant is sucked in to form a jet stream.

The primary coolant ejected from the jet pump 16 is heated while passing through the core 10, and becomes a gas-liquid mixture two-phase flow. Then, the gas-liquid mixed flow sent to the inside of the gas-water separator 18 is separated into steam and water, and after the steam is further dehumidified by the steam dryer 19, the upper part of the reactor pressure vessel 2 It flows out from the main steam nozzle 27 (steam outlet nozzle). This spilled steam is supplied to the turbine system (not shown). These configurations are examples of nuclear power plants, and some plants may not have the jet pump 16.

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 become water supply, which is provided in the reactor pressure vessel 2. It is guided to the water supply nozzle 12. A water supply spray ring 77 formed in an annular shape along the inner wall of the reactor pressure vessel 2 is connected to the water supply nozzle 12. The water supply spray ring 77 is a ring-shaped pipe arranged along the inner circumference of the reactor pressure vessel 2, and a plurality of holes into which the primary coolant is ejected are formed. The primary coolant as water supply guided to the water supply nozzle 12 is supplied to the inside of the reactor pressure vessel 2 from the plurality of holes of the water supply spray ring 77.

Further, inside the reactor pressure vessel 2, a core spray ring 78 formed in an annular shape along the inner wall of the reactor pressure vessel 2 is arranged at a position substantially the same height as the water supply spray ring 77. The core spray ring 78 is connected to the core spray nozzle 15 provided in the reactor pressure vessel 2 at a position substantially the same height as the water supply nozzle 12. The core spray nozzle 15 is a ring-shaped pipe arranged along the inner circumference of the reactor pressure vessel 2, and a plurality of holes into which the primary coolant is ejected are formed. In an emergency of the core 10, the primary coolant is injected into the reactor pressure vessel 2 from the plurality of holes of the core spray ring 78 via the core spray nozzle 15.

In the reactor pressure vessel 2, the water separated by the steam separator 18 and the steam dryer 19 flows down into the downcomer 14 between the core shroud 11 and the reactor pressure vessel 2, and is sucked into the jet pump 16. It is guided to the core 10 and circulates inside the reactor pressure vessel 2.

Further, a control rod drive mechanism housing 29, a neutron flux measurement housing 28, and a reactor pressure vessel drain nozzle 30 are installed at the bottom of the reactor pressure vessel 2.

The control rod drive mechanism housing 29 accommodates a control rod drive mechanism (not shown). During the operation of the nuclear reactor, the control rod drive mechanism drives the control rods (not shown) to control the output of the core 10.

Further, the neutron flux measurement housing 28 accommodates a neutron flux measuring instrument (not shown). When the reactor is in operation, this neutron flux measuring instrument measures the neutron flux in the core 10.

The reactor pressure vessel drain nozzle 30 is connected to the RPV bottom drain line 31 and is used to drain the reactor water inside the reactor pressure vessel 2. The reactor pressure vessel drain nozzle 30 and the RPV bottom drain line 31 are part of the main system. Further, the furnace bottom pipe 32 extending below the RPV bottom drain line 31 is a part of the temporary system. Further, the bottom valve 69 provided between the RPV bottom drain line 31 and the bottom pipe 32 may be a part of the main system or a part of the temporary system. The RPV bottom drain line 31 is connected to the bottom valve 69, and the neutron flux measurement housing 28 and the control rod drive mechanism housing 29 are connected to the furnace bottom valve 69.

After many years of use of the reactor, corrosion products are generated in the primary coolant flowing through the reactor pressure vessel 2, the reactor recirculation system 3, and the turbine system, respectively. Of these, the corrosion products activated through the core 10 adhere to and accumulate on various devices arranged in the reactor pressure vessel 2 and the reactor recirculation system 3 to become a radiation source. Therefore, as a measure to reduce the exposure dose of workers at the time of decommissioning, it is necessary to carry out chemical decontamination of contaminated pipes or equipment.

The decontamination method of the present embodiment mainly targets the reactor pressure vessel 2 or the reactor recirculation system 3 including the reactor pressure vessel 2 for chemical decontamination. The above-mentioned RHR head spray pipe 26 and the reactor recirculation system 3 are main systems that are also used during the operation of the reactor. When decontaminating, a temporary system 4 for decontamination is constructed in addition to the main system.

Next, the temporary system 4 (temporary circulation system) of the present embodiment will be described. In the temporary system 4, in the reactor pressure vessel 2, the main steam nozzle 27, the water supply nozzle 12, and the core spray nozzle 15 are cut from the main pipe, and a new temporary pipe is connected. Will be built. Further, in the reactor pressure vessel 2, a temporary pipe or hose is newly connected to the control rod drive mechanism housing 29, the neutron flux measurement housing 28, and the reactor pressure vessel drain nozzle 30 to be constructed.

As shown in FIG. 1, the temporary system 4 is mainly connected to the upper equipment and the lower equipment of the reactor pressure vessel 2. Further, the temporary system 4 includes a temporary pump 25. By driving the temporary pump 25 and the PLR pump 21, the decontamination liquid can be circulated between the reactor pressure vessel 2 and the temporary system 4.

In the reactor pressure vessel 2 of the present embodiment, the upper equipment includes at least one of a main steam nozzle 27, a water supply nozzle 12, a core spray nozzle 15, and a head spray nozzle 13. In this way, the existing upper equipment of the reactor pressure vessel 2 can be used. Further, the lower equipment includes at least one of the control rod drive mechanism housing 29, the neutron flux measurement housing 28, the reactor pressure vessel drain nozzle 30, and the reactor recirculation system 3. In this way, the existing lower equipment of the reactor pressure vessel 2 can be used.

The upper equipment may be equipment provided at least above the center of the reactor pressure vessel 2 in the vertical direction. Further, the lower equipment may be equipment provided below the upper equipment. Here, the terms "upper equipment" and "lower equipment" of the present embodiment are not limited to specific equipment. The equipment constituting the "upper equipment" and the "lower equipment" may be changed according to the mode of decontamination. For example, when the main steam nozzle 27 is used as the upper equipment, the water supply nozzle 12 or the core spray nozzle 15 provided below the main steam nozzle 27 may be used as the lower equipment.

The temporary system 4 includes a first temporary main pipe 39 and a second temporary main pipe 48. The first temporary main pipe 39 can circulate the decontamination liquid to the main steam nozzle 27, the water supply nozzle 12, the core spray nozzle 15, and the head spray nozzle 13 as the upper equipment of the reactor pressure vessel 2 in the temporary system 4. Connect to. A temporary pump 25 is provided in the first temporary main pipe 39. That is, the decontamination liquid is taken in and out of the reactor pressure vessel 2 from the first temporary main pipe 39 via the upper equipment.

In the present embodiment, a circulation path is constructed between the reactor pressure vessel 2 and the temporary system 4. By driving the temporary pump 25 provided in the temporary system 4, the decontamination liquid is circulated through this circulation path. If the PLR pump 21 can be driven, the PLR pump 21 may be driven in addition to the temporary pump 25. Further, a temporary pump that assists or replaces the PLR pump 21 may be provided in the vicinity of the recirculation water inlet nozzle 24 of the reactor recirculation system 3.

The second temporary main pipe 48 connects the control rod drive mechanism housing 29, the neutron flux measurement housing 28, the reactor pressure vessel drain nozzle 30, and the reactor recirculation system 3 as lower equipment so that the decontamination liquid can flow. To do. For example, the second temporary main pipe 48 is connected to the neutron flux measurement housing 28, the control rod drive mechanism housing 29, and the RPV bottom drain line 31 at the bottom of the furnace via the bottom pipe 32. That is, the decontamination liquid is taken in and out of the reactor pressure vessel 2 from the second temporary main pipe 48 via the lower equipment.

Further, a purification system 58 is connected to the second temporary main pipe 48. The purification system 58 includes a heat exchanger 49 as a temperature controller, a drug preparation section 50 as a drug supply section, an ozone generator 51, a decontamination agent decomposition section 52, a filter 53, an ion exchange section 54, and the like. Multiple devices are connected to maintain optimal liquid condition. Of these devices, the decontamination agent decomposition unit 52, the filter 53, and the ion exchange unit 54 constitute the purification device 57. The purification device 57 may be operated only when it is necessary to purify the decontamination liquid. Therefore, it is preferable that the purification device 57 is connected and the purification system 58 having the purification system valve 59 is connected to the second temporary main pipe 48 in an annular shape. Then, the purification system valve 59 is opened only when necessary, and the purification pump 55 of the purification system 58 is started to guide the decontamination liquid from the second temporary main pipe 48 to the purification system 58.

The drug preparation unit 50 is connected to the second temporary main pipe 48 via the adjustment pump 56. For example, the decontamination liquid extracted from the reactor pressure vessel 2 via the bottom pipe 32 is recovered by the second temporary main pipe 48. The recovered decontamination liquid is heated or cooled by the heat exchanger 49 to adjust the temperature by the time it reaches the first temporary main pipe 39. At the same time, the content of a drug such as a reducing agent prepared by the drug preparation unit 50 in the decontamination liquid is adjusted by the adjusting pump 56.

Further, the ozone generator 51 is connected to the second temporary main pipe 48 via the gas mixer 60. For example, when the oxidizing agent is ozone, ozone is mixed into the decontamination liquid of the second temporary main pipe 48 from the ozone generator 51 via the gas mixer 60.

Here, the organic acid as the reducing agent is preferably at least one of oxalic acid, formic acid, pyruvic 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 decomposable organic acids, 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. Here, 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 a liquid state include the following. For example, monocarboxylic acids include formic acid, pyruvic acid, and glyoxylic acid. Dicarboxylic acids include malonic acid, tartaric acid, and maleic acid. Examples of tricarboxylic acids include citric acid. In order to obtain a higher decontamination effect, a plurality of these organic acids may be used as appropriate.

When purifying the decontamination liquid flowing through the temporary system 4, the purification system valve 59 is opened and the purification pump 55 is started to introduce the decontamination liquid into the purification system 58.

The decontamination agent decomposition unit 52 includes, 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. The ion exchange unit 54 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 purified decontamination liquid is returned to the reactor pressure vessel 2 from, for example, the first temporary main pipe 39, the PLR middle pipe 34, and the RHR head spray pipe 26.

In the reactor recirculation system 3, the PLR bottom pipe 33 is connected between the PLR pump 21 and the PLR discharge valve 23. The PLR bottom pipe 33 is connected to the second temporary main pipe 48. Further, the PLR middle pipe 34 is connected between the PLR discharge valve 23 and the recirculating water inlet nozzle 24. The PLR middle pipe 34 is connected to the first temporary main pipe 39. For example, the PLR middle pipes 34 connected to the plurality of reactor recirculation systems 3 merge with each other and are connected to the first temporary main pipe 39. Further, a middle valve 37 is provided in each PLR middle pipe 34.

The merged PLR middle pipe 34 is connected to the first temporary main pipe 39 connected to the main steam nozzle 27. The PLR middle pipe 34 is connected between the temporary pump 25 and the temporary main valve 47 provided on the downstream side of the temporary pump 25 in the first temporary main pipe 39.

Further, a first backflow pipe 41 for reversing the circulation of the decontamination liquid is connected to the first temporary main pipe 39. The first backflow pipe 41 is connected to two connection points of the first temporary main pipe 39 so as to sandwich the temporary pump 25. That is, an annular flow path is formed by the first temporary main pipe 39 and the first backflow pipe 41. Further, the first backflow pipe 41 is provided with a first backflow valve 42 that is closed during forward circulation.

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

In the present embodiment, the RHR head spray pipe 26 connected to the head spray pipe connecting pipe 44 is connected to the head spray nozzle 13, but other embodiments may be used. For example, the head spray pipe connecting pipe 44 may be connected to an upper lid instrumentation nozzle (not shown) or a vent nozzle (not shown) provided on the crown of the reactor pressure vessel 2.

Further, as the configuration of the decontamination executing device 1, it may be connected to any one or two of the head spray nozzle 13, the upper lid instrumentation nozzle, and the vent nozzle. Then, when the decontamination liquid is injected into the reactor pressure vessel 2, the other nozzle to which the RHR head spray tube 26 is not connected discharges a gas such as air inside the reactor pressure vessel 2. It may also be used as an air vent for discharging the gas generated when the reducing agent as a chemical injected into the decontamination liquid is decomposed.

A bottom valve 69 is provided in the bottom pipe 32 arranged below the reactor pressure vessel 2. The furnace bottom pipe 32 is connected to the second temporary main pipe 48. The second temporary main pipe 48 extends above the reactor pressure vessel 2 and is connected to the first temporary main pipe 39 on the upstream side of the temporary pump 25. Further, the RPV bottom drain line 31 is connected to the bottom pipe 32 via the bottom valve 69.

Further, the PLR middle pipe 34 and the second temporary main pipe 48 are connected so that the second backflow pipe 62 having the second backflow valve 61 is parallel to the temporary pump 25. Further, of the second temporary main pipe 48, a third check valve 63 is provided between the connection point of the second backflow pipe 62 and the connection point of the first temporary main pipe 39.

Further, an exhaust gas treatment system 64 for discharging the gas accumulated inside the reactor pressure vessel 2 is connected to the reactor pressure vessel 2. The exhaust gas treatment system 64 includes a gas treatment mechanism 65. When gas is generated inside the reactor pressure vessel 2 by using ozone gas or the like for decontamination, the gas is discharged from the exhaust gas treatment system 64. The gas treatment mechanism 65 has a filter and the like so as to purify the gas discharged from the inside of the reactor pressure vessel 2. Although the exhaust gas treatment system 64 is shown by a solid line as a part of the temporary system, the exhaust gas treatment system 64 may be provided as a part of the main system.

The reactor pressure vessel 2 is provided with a plurality of main steam nozzles 27. For example, four main steam nozzles 27 are provided. These main steam nozzles 27 are provided at the same height position in the reactor pressure vessel 2, and are arranged side by side in the circumferential direction of the reactor pressure vessel 2. The temporary system 4 includes a main steam nozzle pipe 35 provided corresponding to each main steam nozzle 27. These main steam nozzle pipes 35 are connected to the first temporary main pipe 39 via the main steam nozzle valve 38. By opening the main steam nozzle valve 38, the decontamination liquid can be taken in and out of the reactor pressure vessel 2 from the main steam nozzle 27.

Further, the reactor pressure vessel 2 is provided with a plurality of water supply nozzles 12. For example, four water supply nozzles 12 are provided. These water supply nozzles 12 are provided at the same height position in the reactor pressure vessel 2, and are arranged side by side in the circumferential direction of the reactor pressure vessel 2.

The temporary system 4 includes a water supply nozzle pipe 36 provided corresponding to each water supply nozzle 12. A water supply nozzle valve 40 is provided in these water supply nozzle pipes 36. Further, the water supply nozzle pipe 36 is connected to the first temporary main pipe 39 via the first switching pipe 74 provided with the first switching valve 71. By opening the water supply nozzle valve 40 and the first switching valve 71, the decontamination liquid can be taken in and out of the reactor pressure vessel 2 via the water supply spray ring 77 connected to the water supply nozzle 12.

The water supply nozzle pipe 36 is connected to the reactor recirculation system 3 via a second switching pipe 75 provided with a second switching valve 72. Further, the water supply nozzle pipe 36 is connected to the PLR middle pipe 34 via a third switching pipe 76 provided with a third switching valve 73. By controlling the opening and closing of the first switching valve 71, the second switching valve 72, and the third switching valve 73, the decontamination liquid that is taken in and out of the reactor pressure vessel 2 via the water supply spray ring 77 The circulation mode can be switched.

Further, the reactor pressure vessel 2 is provided with a plurality of core spray nozzles 15. For example, two core spray nozzles 15 are provided. These core spray nozzles 15 are provided at the same height position in the reactor pressure vessel 2, and are arranged side by side in the circumferential direction of the reactor pressure vessel 2.

The temporary system 4 includes a core spray nozzle pipe 43 provided corresponding to each core spray nozzle 15. A core spray nozzle valve 45 is provided in these core spray nozzle pipes 43. Further, the core spray nozzle pipe 43 is connected to the first temporary main pipe 39 via the first switching pipe 74 provided with the first switching valve 71. By opening the core spray nozzle valve 45 and the first switching valve 71, the decontamination liquid can be taken in and out of the reactor pressure vessel 2 via the core spray nozzle 15 connected to the core spray nozzle 15.

The core spray nozzle pipe 43 is connected to the reactor recirculation system 3 via a second switching pipe 75 provided with a second switching valve 72. Further, the core spray nozzle pipe 43 is connected to the PLR middle pipe 34 via a third switching pipe 76 provided with a third switching valve 73. By controlling the opening and closing of the first switching valve 71, the second switching valve 72, and the third switching valve 73, the decontamination liquid that is taken in and out of the reactor pressure vessel 2 via the core spray ring 78 The circulation mode can be switched.

Further, the decontamination execution device 1 includes a control unit 66 that controls various devices such as valves and pumps provided in the reactor recirculation system 3 and the temporary system 4. The control unit 66 is connected to various devices via a control line 67. Then, the circulation mode of the decontamination liquid is controlled by the control of the control unit 66. That is, the control unit 66 can control the direction of the flow of the decontamination liquid. In the piping of the temporary system 4, a check valve may be provided at a position where the flow of the decontamination liquid is always in one direction.

In the present embodiment, the control unit 66 controls the open / closed state of the valve to switch the decontamination mode in a plurality of modes. In addition, in FIG. 1, FIG. 3, FIG. 5, and FIG. 7, the black-painted valve shows the closed state, and the white-painted valve shows the open state. Further, in FIGS. 1 to 8, the direction of the arrow in the figure indicates the direction in which the decontamination liquid flows.

1 and 2 show the open / closed state of the valve and the flow mode of the decontamination liquid in the first decontamination mode. The first decontamination mode may be referred to as a normal cleaning mode (forward circulation mode).

As shown in FIG. 1, in the first decontamination mode (normal cleaning mode), the first check valve 42, the second check valve 61, the second switching valve 72, and the third switching valve 73 are closed in the temporary system 4. And the other valves are opened. Further, in the reactor recirculation system 3, the PLR discharge valve 23 is closed and the other valves are opened. When the temporary pump 25 and the PLR pump 21 are driven in this state, the decontamination liquid flows in the circulation mode of the first decontamination mode.

In the first decontamination mode, the decontamination liquid flowing through the temporary system 4 is mainly introduced into the reactor pressure vessel 2 from the first temporary main pipe 39 and the RHR head spray pipe 26. Further, the decontamination liquid discharged from the inside of the reactor pressure vessel 2 mainly flows to the second temporary main pipe 48.

As shown in FIG. 2, in the first decontamination mode, the inside of the reactor pressure vessel 2 is passed through the head spray nozzle 13, the main steam nozzle 27, the water supply nozzle 12, the core spray nozzle 15, and the recirculating water inlet nozzle 24. Decontamination liquid is introduced into. That is, the decontamination liquid is introduced into the reactor pressure vessel 2 by using the upper equipment such as the head spray nozzle 13, the main steam nozzle 27, the water supply nozzle 12, and the core spray nozzle 15.

The decontamination liquid introduced by the water supply nozzle 12 is ejected into the reactor pressure vessel 2 via the water supply spray ring 77. Further, the decontamination liquid introduced by the core spray nozzle 15 is ejected into the reactor pressure vessel 2 via the core spray ring 78. Further, the decontamination liquid introduced by the recirculating water inlet nozzle 24 is ejected into the reactor pressure vessel 2 via the jet pump 16.

Further, in the first decontamination mode, the decontamination liquid is decontaminated from the inside of the reactor pressure vessel 2 via the recirculating water outlet nozzle 20, the neutron flux measurement housing 28, the control rod drive mechanism housing 29, and the reactor pressure vessel drain nozzle 30. Is discharged.

In this first decontamination mode, a down flow (flow of the first aspect) in which the decontamination liquid drops is generated inside the reactor pressure vessel 2. By this downflow, it is possible to decontaminate the reactor internal structures such as the core 10 or the steam separator 18 existing inside the reactor pressure vessel 2.

Further, since a large amount of decontamination liquid can be introduced into the inside of the reactor pressure vessel 2 from the upper part by using the head spray nozzle 13 and the main steam nozzle 27 provided on the upper part of the reactor pressure vessel 2, there is momentum. A flow of decontamination liquid can be generated.

3 and 4 show the open / closed state of the valve and the flow mode of the decontamination liquid in the second decontamination mode. The second decontamination mode may be referred to as a backwash mode (backflow circulation mode).

As shown in FIG. 3, in the second decontamination mode (backwash mode), in the temporary system 4, the head spray pipe connecting valve 46, the temporary main valve 47, the third check valve 63, the second switching valve 72, and the third The switching valve 73 is closed, and the other valves are opened. Further, in the reactor recirculation system 3, the PLR intake valve 22 is closed and the other valves are opened. When the temporary pump 25 is driven in this state, the decontamination liquid flows in the circulation mode of the second decontamination mode.

In the second decontamination mode, the decontamination liquid flowing through the temporary system 4 is mainly introduced from the second temporary main pipe 48 into the reactor pressure vessel 2. Further, the decontamination liquid discharged from the inside of the reactor pressure vessel 2 mainly flows to the first temporary main pipe 39.

As shown in FIG. 4, in the second decontamination mode, the reactor pressure vessel 2 is connected via the recirculation water inlet nozzle 24, the neutron flux measurement housing 28, the control rod drive mechanism housing 29, and the reactor pressure vessel drain nozzle 30. A decontamination liquid is introduced inside. That is, the decontamination liquid is introduced into the reactor pressure vessel 2 by using the recirculating water inlet nozzle 24, the neutron flux measurement housing 28, the control rod drive mechanism housing 29, and the lower equipment such as the reactor pressure vessel drain nozzle 30. To.

Further, in the second decontamination mode, the decontamination liquid is discharged from the inside of the reactor pressure vessel 2 via the main steam nozzle 27, the water supply nozzle 12, and the core spray nozzle 15. The decontamination liquid inside the reactor pressure vessel 2 is discharged from the water supply nozzle 12 via the water supply spray ring 77, and is also discharged from the core spray nozzle 15 via the core spray ring 78.

In this second decontamination mode, an upflow (flow of the second aspect) in which the decontamination liquid rises is generated inside the reactor pressure vessel 2. By this upflow, it is possible to decontaminate the internal structure of the reactor such as the core 10 or the steam separator 18 existing inside the reactor pressure vessel 2.

Further, the state in which the downflow of the decontamination liquid is generated inside the reactor pressure vessel 2 in the first decontamination mode (normal cleaning mode) is switched to the second decontamination mode (backwash mode). In this way, the inside of the reactor pressure vessel 2 can be backwashed by generating not only a flow in one direction but also a flow in the opposite direction.

5 and 6 show the open / closed state of the valve and the flow mode of the decontamination liquid in the third decontamination mode.

As shown in FIG. 5, in the third decontamination mode, in the temporary system 4, the head spray pipe connecting valve 46, the temporary main valve 47, the second check valve 61, the first switching valve 71, and the third switching valve 73 are It is closed and the other valves are opened. Further, in the reactor recirculation system 3, the PLR discharge valve 23 is closed and the other valves are opened. When the temporary pump 25 and the PLR pump 21 are driven in this state, the decontamination liquid flows in the circulation mode of the third decontamination mode.

In the third decontamination mode, the decontamination liquid flowing through the temporary system 4 is mainly introduced from the PLR middle pipe 34 into the reactor pressure vessel 2. Further, the decontamination liquid discharged from the inside of the reactor pressure vessel 2 mainly flows to the second temporary main pipe 48.

As shown in FIG. 6, in the third decontamination mode, the decontamination liquid is introduced into the reactor pressure vessel 2 via the water supply nozzle 12, the core spray nozzle 15, and the recirculating water inlet nozzle 24. That is, the decontamination liquid is introduced into the reactor pressure vessel 2 by using the upper equipment such as the water supply nozzle 12 and the core spray nozzle 15.

Further, in the third decontamination mode, the reactor pressure vessel 2 is connected via the main steam nozzle 27, the recirculated water outlet nozzle 20, the neutron bundle measurement housing 28, the control rod drive mechanism housing 29, and the reactor pressure vessel drain nozzle 30. The decontamination liquid is discharged from the inside.

In this third decontamination mode, a downflow in which the decontamination liquid drops is generated inside the reactor pressure vessel 2 in a portion below the water supply spray ring 77 and the core spray ring 78. Further, an upflow in which the decontamination liquid rises occurs in the portion above the water supply spray ring 77 and the core spray ring 78. By these flows (flow of the third aspect), it is possible to decontaminate the internal structure of the reactor such as the core 10 or the steam separator 18 existing inside the reactor pressure vessel 2.

7 and 8 show the open / closed state of the valve and the flow mode of the decontamination liquid in the fourth decontamination mode.

As shown in FIG. 7, in the fourth decontamination mode, the first check valve 42, the second check valve 61, the first switching valve 71, and the second switching valve 72 are closed in the temporary system 4, and other valves are used. Is released. Further, in the reactor recirculation system 3, the PLR intake valve 22 is closed and the other valves are opened. When the temporary pump 25 is driven in this state, the decontamination liquid flows in the circulation mode of the fourth decontamination mode.

In the fourth decontamination mode, the decontamination liquid flowing through the temporary system 4 is mainly introduced into the reactor pressure vessel 2 from the first temporary main pipe 39 and the RHR head spray pipe 26. The decontamination liquid is also introduced into the reactor pressure vessel 2 from a part of the second temporary main pipe 48. The second temporary main pipe 48 has a role of flowing a decontamination liquid discharged from the inside of the reactor pressure vessel 2.

As shown in FIG. 8, in the fourth decontamination mode, the head spray nozzle 13, the main steam nozzle 27, the recirculating water inlet nozzle 24, the neutron flux measurement housing 28, the control rod drive mechanism housing 29, and the reactor pressure vessel drain nozzle 30 The decontamination liquid is introduced into the reactor pressure vessel 2 via the above. That is, the decontamination liquid is introduced into the reactor pressure vessel 2 by using the upper equipment such as the head spray nozzle 13 and the main steam nozzle 27. Further, the decontamination liquid is introduced into the reactor pressure vessel 2 by using the recirculating water inlet nozzle 24, the neutron flux measurement housing 28, the control rod drive mechanism housing 29, and the lower equipment such as the reactor pressure vessel drain nozzle 30. To.

Further, in the fourth decontamination mode, the decontamination liquid is discharged from the inside of the reactor pressure vessel 2 via the water supply nozzle 12 and the core spray nozzle 15. The decontamination liquid inside the reactor pressure vessel 2 is discharged from the water supply nozzle 12 via the water supply spray ring 77, and is also discharged from the core spray nozzle 15 via the core spray ring 78.

In this fourth decontamination mode, an upflow in which the decontamination liquid rises occurs in the portion below the water supply spray ring 77 and the core spray ring 78 inside the reactor pressure vessel 2. Further, a downflow in which the decontamination liquid drops is generated in the portion above the water supply spray ring 77 and the core spray ring 78. By these flows (flow of the fourth aspect), it is possible to decontaminate the internal structure of the reactor such as the core 10 or the steam separator 18 existing inside the reactor pressure vessel 2.

Although not particularly shown, there may be other decontamination modes. For example, in the first decontamination mode (normal cleaning mode) shown in FIG. 2 described above, the decontamination liquid is discharged inside the reactor pressure vessel 2 by using the main steam nozzle 27, the water supply nozzle 12, and the core spray nozzle 15. Although it has been introduced, other aspects may be used.

For example, the decontamination liquid may be introduced into the reactor pressure vessel 2 by using the main steam nozzle 27 and the water supply nozzle 12, and the core spray nozzle 15 may not be used. Further, it is not necessary to use the main steam nozzle 27 and the core spray nozzle 15 to introduce the decontamination liquid into the reactor pressure vessel 2 and not to use the water supply nozzle 12. Further, it is not necessary to introduce the decontamination liquid into the reactor pressure vessel 2 by using the main steam nozzle 27 and not to use the water supply nozzle 12 and the core spray nozzle 15. Further, it is not necessary to introduce the decontamination liquid into the reactor pressure vessel 2 by using the water supply nozzle 12 and not to use the main steam nozzle 27 and the core spray nozzle 15. Further, it is not necessary to use the core spray nozzle 15 to introduce the decontamination liquid into the reactor pressure vessel 2 and not to use the main steam nozzle 27 and the water supply nozzle 12.

Further, in the second decontamination mode (backwash mode) shown in FIG. 4 described above, the decontamination liquid is discharged from the inside of the reactor pressure vessel 2 by using the main steam nozzle 27, the water supply nozzle 12, and the core spray nozzle 15. Although it is discharged, other aspects may be used.

For example, it is not necessary to use the main steam nozzle 27 and the water supply nozzle 12 to discharge the decontamination liquid from the inside of the reactor pressure vessel 2 and not to use the core spray nozzle 15. Further, it is not necessary to use the main steam nozzle 27 and the core spray nozzle 15 to discharge the decontamination liquid from the inside of the reactor pressure vessel 2 and not to use the water supply nozzle 12. Further, it is not necessary to use the main steam nozzle 27 to discharge the decontamination liquid from the inside of the reactor pressure vessel 2 and not to use the water supply nozzle 12 and the core spray nozzle 15. Further, it is not necessary to use the water supply nozzle 12 to discharge the decontamination liquid from the inside of the reactor pressure vessel 2 and not to use the main steam nozzle 27 and the core spray nozzle 15. Further, it is not necessary to use the core spray nozzle 15 to discharge the decontamination liquid from the inside of the reactor pressure vessel 2 and not to use the main steam nozzle 27 and the water supply nozzle 12.

In the present embodiment, by appropriately switching between a plurality of types of decontamination modes and performing decontamination, decontamination can be performed according to the contamination status of the reactor pressure vessel 2 and the internal structure inside the reactor.

Further, the decontamination mode may be switched between the early stage, the middle stage and the late stage during the decontamination period. That is, the decontamination mode may be switched between the first period during the decontamination period and the second period different from the first period.

Further, the number of main steam nozzles 27, water supply nozzles 12, core spray nozzles 15, and head spray nozzles 13 used as upper equipment may be controlled during the decontamination period. For example, in the initial stage of decontamination, all of the plurality of nozzles are opened to slow down the flow rate of the decontamination liquid and suppress extreme radioactive elution. On the other hand, in the latter stage of decontamination, the flow rate of the decontamination liquid is increased by passing water through a plurality of nozzles individually to perform finish decontamination. In the intermediate stage of decontamination, about half of the nozzles may be used as appropriate.

In the present embodiment, a main steam nozzle valve 38 corresponding to each of the plurality of main steam nozzles 27 is provided. By controlling the opening and closing of each of the main steam nozzle valves 38, the mode of the flow of the decontamination liquid generated inside the reactor pressure vessel 2 may be switched.

As shown in FIG. 9, the main steam pipes (not shown) of the four main steam nozzles 27A to 27D are cut, and temporary main steam nozzle pipes 35A to 35D are connected to the cut points of the respective main steam pipes. To. Main steam nozzle valves 38A to 38D, which can be individually controlled to open and close, are connected to the main steam nozzle pipes 35A to 35D.

When all the main steam nozzle valves 38A to 38D are opened, the decontamination liquid is introduced into the reactor pressure vessel 2 from all four main steam nozzles 27A to 27D. Here, it is assumed that the discharge amount of the temporary pump 25 is constant and the flow rate of the decontamination liquid flowing through the first temporary main pipe 39 is constant. In this state, one main steam nozzle valve 38A is opened, and the other main steam nozzle valves 38B to 38D are closed. Then, the decontamination liquid is introduced into the reactor pressure vessel 2 from only one main steam nozzle 27A. Assuming that the discharge amount of the temporary pump 25 is constant, the case where the decontamination liquid is introduced from one main steam nozzle 27A is better than the case where the decontamination liquid is introduced from all the main steam nozzles 27A to 27D. The flow rate of the decontamination liquid flowing only from the main steam nozzle 27A increases.

For example, if contamination remains in the predetermined portion P of the furnace structure such as the air-water separator 18 (when there is high-dose contamination), only the main steam nozzle 27A closest to the predetermined portion P is used. Decontamination can be promoted by increasing the flow rate of the decontamination liquid flowing from.

Further, at the initial stage (first stage) of the decontamination period, the decontamination liquid is introduced into the reactor pressure vessel 2 from all four main steam nozzles 27A to 27D. Then, in the latter stage (second stage) of the decontamination period, the decontamination liquid may be introduced into the reactor pressure vessel 2 by sequentially using the main steam nozzles 27A to 27D individually. For example, after using only the main steam nozzle 27A, only the main steam nozzle 27B is used, then only the main steam nozzle 27C is used, and further, only the main steam nozzle 27D is used, and this is repeated.

That is, in the first period, all the main steam nozzles 27A to 27D are used simultaneously to pass the decontamination liquid, and in the second period different from the first period, the respective main steam nozzles 27A to 27D are sequentially used individually. Pass the decontamination liquid through. In this way, since the decontamination liquid can be passed through in different water flow modes during different periods, it is possible to generate various modes of decontamination liquid flow inside the reactor pressure vessel 2. Since the number of main steam nozzles 27A to 27D through which water is passed changes between the first period and the second period, the flow velocity of the decontamination liquid flow can be changed. When the discharge amount of the temporary pump 25 is the same, the flow velocity becomes slow when the number of main steam nozzles 27A to 27D through which water is passed is large. On the other hand, the number of main steam nozzles 27A to 27D through which water is passed is small, and the flow velocity becomes high. In this way, the flow velocity of the decontamination liquid flowing out from the main steam nozzles 27A to 27D can be controlled. The discharge amount of the temporary pump 25 may be changed during the decontamination period.

Further, when the decontamination liquid is circulated, it is preferable to adjust the water flow time of the decontamination liquid according to the flow rate of the decontamination liquid at the target site of chemical decontamination. Normally, systematic decontamination of a plant in service affects the subsequent inspection work process, so decontamination in the shortest possible time is required. However, in the case of decommissioning, since there are few time constraints, it is possible to take a long water flow time in the part where the linear flow velocity of the decontamination liquid is slow. Therefore, in consideration of the output of the temporary pump 25, the water flow time may be lengthened when the flow velocity is slow, and conversely, the water flow time may be shortened when the flow velocity is high.

In the present embodiment, the insoluble matter inside the reactor pressure vessel 2 is removed before or after the period during which the reactor pressure vessel 2 is chemically decontaminated. In this way, it is possible to prevent insoluble matter from depositing on the bottom of the furnace or the structure inside the furnace. The insoluble substance is, for example, a substance that does not dissolve in a decontamination liquid such as rust.

For example, before the period of chemical decontamination of the reactor pressure vessel 2, the water inside the reactor pressure vessel 2 before injecting the decontamination agent is heated, and the water is passed through the filter 53 to be insoluble. Remove things. By doing so, the insoluble matter is removed during the temperature rise of the water in the furnace, so that the subsequent chemical decontamination can be smoothly performed.

In the present embodiment, as shown in FIGS. 2 and 4, the control rod drive mechanism housing 29, the neutron flux measurement housing 28, and the reactor pressure vessel drain nozzle 30 are used as lower equipment to remove the inside of the reactor pressure vessel 2. The dyeing liquid is taken in and out. Here, only one reactor pressure vessel drain nozzle 30 is provided, but many control rod drive mechanism housings 29 and neutron flux measurement housings 28 are provided. For example, by using a large number of control rod drive mechanism housings 29 and neutron flux measurement housing 28, the decontamination liquid can be taken in and out of the reactor pressure vessel 2, and gas is introduced into the reactor pressure vessel 2. Bubbling can be performed (see FIG. 11).

Next, the connection of the valves to the control rod drive mechanism housing 29 and the neutron flux measurement housing 28 will be specifically described. It should be noted that each of the plurality of housings 28 and 29 has the same configuration.

As shown in FIG. 10, a closing flange 80 provided with a first connection valve 81 is attached to the lower ends of the housings 28 and 29. The first connection valve 81 is provided with a first plug 82. A pipe joint 90 is connected to the first plug 82. A first socket 83 connected to the first plug 82 is provided at the upper end of the pipe joint 90.

The pipe joint 90 includes a pipe portion 91 extending in the vertical direction and a branch portion 92 protruding laterally from the pipe portion 91. That is, the pipe joint 90 is a member forming a T shape when viewed from the side. A gas introduction hose 84 extending from a gas supply device (not shown) is connected to the branch portion 92. The gas is exemplified by air or an inert gas. Further, the branch portion 92 is provided with a gas supply valve 85 corresponding to the gas introduction hose 84.

A drain valve 86 is provided at a position below the branch portion 92 in the pipe portion 91 of the pipe joint 90. Further, a second plug 87 is provided at the lower end of the pipe portion 91. The second socket 88 of the second connection valve 89 is connected to the second plug 87. A drain hose 79 is connected to the second connection valve 89. The drain hose 79 is connected to the above-mentioned bottom valve 69 (FIG. 1). The RPV bottom drain line 31 may be provided with a connection valve for connecting the drain hose 79, and the drain hose 79 may be joined to the RPV bottom drain line 31.

When the decontamination liquid is taken in and out of the reactor pressure vessel 2 using the housings 28 and 29, the first connection valve 81, the drain valve 86, and the second connection valve 89 are opened, and the gas supply valve 85 is opened. To close. In this state, the decontamination liquid can be introduced or discharged from the RPV bottom drain line 31 into the reactor pressure vessel 2 via the housings 28 and 29.

When gas is introduced into the reactor pressure vessel 2 using the housings 28 and 29 to perform bubbling, the first connection valve 81 and the gas supply valve 85 are opened, and the drain valve 86 and the second connection are made. Close the valve 89. In this state, the gas supplied from the gas supply device (not shown) is introduced into the reactor pressure vessel 2 via the housings 28 and 29, and bubbling can be performed (see FIG. 11).

In the present embodiment, bubbling can remove insoluble matter adhering to the housings 28, 29 or the furnace structure. Further, after bubbling for a predetermined time, insoluble matter can be discharged together with the decontamination liquid from the inside of the reactor pressure vessel 2 using the housings 28 and 29.

Further, bubbling may be performed by introducing gas into the reactor pressure vessel 2 using some of the housings 28 and 29 out of a large number of housings 28 and 29. Then, the insoluble matter blown up by the bubbling may be discharged from the inside of the reactor pressure vessel 2 by using the housings 28 and 29 that are not used for the bubbling. In this way, the insoluble matter accumulated in the housings 28 and 29 can be efficiently removed.

Regarding the control rod drive mechanism housing 29 and the neutron flux measurement housing 28 as the lower equipment, in order to prevent sludge from accumulating on the bottom of the furnace, basically all the decontamination liquids are always passed through, but the dose Depending on the rate, the number of housings 28 and 29 used for water flow may be reduced.

Further, the dose rates of the control rod drive mechanism housing 29 and the neutron flux measurement housing 28 may be measured before or during decontamination, respectively. Then, bubbling may be performed using the control rod drive mechanism housing 29 or the neutron flux measurement housing 28 having a dose rate higher than the average value of the measurement results to remove the insoluble matter. In this way, the insoluble matter that is a factor that raises the dose rate can be efficiently removed. A predetermined threshold value may be set, and as a result of measurement, bubbling may be performed using the control rod drive mechanism housing 29 or the neutron flux measurement housing 28 having a dose rate higher than this threshold value.

Further, during at least a part of the period during which the reactor pressure vessel 2 is chemically decontaminated, the decontamination liquid is continuously passed through at least one of the control rod drive mechanism housing 29 and the neutron flux measurement housing 28. , The decontamination liquid may be intermittently passed through the reactor pressure vessel drain nozzle 30. In this way, various forms of decontamination liquid flow can be generated at the bottom of the reactor inside the reactor pressure vessel 2. Since the reactor pressure vessel drain nozzle 30 is made of carbon steel, there is a risk of corrosion. Therefore, by intermittently passing the decontamination liquid through the reactor pressure vessel drain nozzle 30, corrosion of the reactor pressure vessel drain nozzle 30 can be suppressed.

Next, the decontamination execution method executed by the decontamination execution apparatus 1 will be described with reference to the flowchart of FIG. The action passively generated by the operation of the decontamination executing device 1 will be described. In addition, the above-mentioned FIGS. 1 to 11 are referred to as appropriate.

As shown in FIG. 12, first, in step S11, before decontamination, the reactor pressure vessel 2 and the temporary system 4 are laid out based on the information such as the design drawings of the main system and the temporary system 4 of the nuclear power plant. The flow mode of the decontamination liquid flowing during decontamination is analyzed in advance. A computer may be used to simulate the flow mode of the decontamination liquid flowing inside the reactor pressure vessel 2.

In the next step S12, the main piping connected to the main steam nozzle 27, the water supply nozzle 12, the core spray nozzle 15, the reactor recirculation system 3, and the like is cut. For example, in the case of the main steam nozzle 27, the main steam pipe (not shown) provided for sending steam toward the turbine (not shown) is cut.

In the next step S13, the temporary system 4 is connected to the portion where the main piping is cut. In addition, temporary equipment such as a temporary pump 25 is also provided. Here, a circulation path is constructed between the reactor pressure vessel 2 and the temporary system 4. If the cut portion is not connected to the temporary system 4, it is closed with a predetermined member.

In the next step S14, the dose rate of each part of the reactor pressure vessel 2 and the internal structure is measured. Here, the dose rates of the control rod drive mechanism housing 29 and the neutron flux measurement housing 28 may also be measured. The measurement of the dose rate includes not only actual measurement but also an aspect of estimating the dose rate of each part of the reactor pressure vessel 2 and the internal structure based on past recorded information such as operation history. Here, the most effective decontamination mode and decontamination liquid flow mode are set based on the dose rate of each part of the reactor pressure vessel 2 and the structure inside the reactor.

In the next step S15, the control unit 66 removes the insoluble matter inside the reactor pressure vessel 2. For example, while raising the temperature of the water inside the reactor pressure vessel 2 before injecting the decontamination agent, the water is passed through the filter 53 to remove the insoluble matter. Further, by bubbling the inside of the reactor pressure vessel 2, insoluble matter adhering to the housings 28 and 29 or the structure inside the reactor is removed.

In the next step S16, the control unit 66 starts driving the temporary pump 25 and the PLR pump 21. Here, the decontamination liquid is circulated in the circulation path formed by the reactor recirculation system 3 and the temporary system 4. For example, the decontamination liquid is circulated in the first decontamination mode (normal cleaning mode) (FIG. 1).

In the next step S17, a down flow (flow of the first aspect) in which the decontamination liquid drops is generated inside the reactor pressure vessel 2 (FIG. 2).

In the next step S18, after circulating the decontamination liquid in the first decontamination mode for a predetermined period, the control unit 66 controls the direction of the flow of the decontamination liquid. For example, the control unit 66 controls to switch from the first decontamination mode to the second decontamination mode (backwash mode) (FIG. 3).

In the next step S19, an upflow (flow of the second aspect) in which the decontamination liquid rises is generated inside the reactor pressure vessel 2 (FIG. 4). Then, the process ends.

In addition, you may repeat steps S17 to S19. Further, the control unit 66 may switch the decontamination mode to the third decontamination mode (flow of the third aspect) or the fourth decontamination mode (flow of the fourth aspect).

Although the flowchart of the present embodiment illustrates a mode in which each step is executed in series, the context of each step is not necessarily fixed, and even if the context of some steps is exchanged. good. Also, some steps may be executed in parallel with other steps.

In the present embodiment, the main water supply spray ring 77 and the core spray ring 78 are used to introduce or discharge the decontamination liquid into the inside of the reactor pressure vessel 2, but it is another embodiment. You may. For example, a temporary spray ring may be provided inside the reactor pressure vessel 2, and the decontamination liquid may be introduced or discharged using this temporary spray ring.

According to the embodiment described above, the atomic atom includes a step of moving the decontamination liquid in and out of the reactor pressure vessel using the upper equipment and the lower equipment to switch the mode of the flow inside the reactor pressure vessel. The decontamination effect of chemical decontamination of the reactor pressure vessel can be improved.

Although some embodiments of the present invention have been described, 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 forms, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Decontamination equipment, 2 ... Reactor pressure vessel, 3 ... Reactor recirculation system, 4 ... Temporary system, 10 ... Core, 11 ... Core shroud, 12 ... Water supply nozzle, 13 ... Head spray nozzle, 14 ... Down kama , 15 ... Core spray nozzle, 16 ... Jet pump, 17 ... Shroud head, 18 ... Air-water separator, 19 ... Steam dryer, 20 ... Recirculating water outlet nozzle, 21 ... PLR pump, 22 ... PLR suction valve, 23 ... PLR discharge valve, 24 ... recirculating water inlet nozzle, 25 ... temporary pump, 26 ... RHR head spray pipe, 27 ... main steam nozzle, 28 ... neutron bundle measurement housing, 29 ... control rod drive mechanism housing, 30 ... reactor Pressure vessel drain nozzle, 31 ... RPV bottom drain line, 32 ... furnace bottom piping, 33 ... PLR bottom piping, 34 ... PLR middle piping, 35 ... main steam nozzle piping, 36 ... water supply nozzle piping, 37 ... middle valve, 38 ... main Steam nozzle valve, 39 ... 1st temporary main pipe, 40 ... Water supply nozzle valve, 41 ... 1st backflow pipe, 42 ... 1st backflow valve, 43 ... Core spray nozzle pipe, 44 ... Head spray pipe connection pipe, 45 ... Core Spray nozzle valve, 46 ... Head spray pipe connection valve, 47 ... Temporary main valve, 48 ... Second temporary main pipe, 49 ... Heat exchanger, 50 ... Chemical preparation department, 51 ... Ozone generator, 52 ... Decontamination agent decomposition Part, 53 ... Filter, 54 ... Ion exchange part, 55 ... Purification pump, 56 ... Adjustment pump, 57 ... Purification device, 58 ... Purification system, 59 ... Purification system valve, 60 ... Gas mixer, 61 ... Second check valve, 62 ... 2nd check pipe, 63 ... 3rd check valve, 64 ... Exhaust gas treatment system, 65 ... Gas treatment mechanism, 66 ... Control unit, 67 ... Control line, 69 ... Reactor bottom valve, 71 ... 1st switching valve, 72 ... 2nd switching valve, 73 ... 3rd switching valve, 74 ... 1st switching pipe, 75 ... 2nd switching pipe, 76 ... 3rd switching pipe, 77 ... Water supply spraying, 78 ... Core spraying, 79 ... Drain hose, 80 ... Closing flange, 81 ... 1st connection valve, 82 ... 1st plug, 83 ... 1st socket, 84 ... Gas introduction hose, 85 ... Gas supply valve, 86 ... Drain valve, 87 ... 2nd plug, 88 ... No. 2 sockets, 89 ... 2nd connection valve, 90 ... pipe joint, 91 ... pipe part, 92 ... branch part.

Claims (12)

A step of connecting the temporary system to the upper equipment provided above the center of the reactor pressure vessel at least in the vertical direction and the lower equipment provided below the upper equipment.
A step of circulating the decontamination liquid in the circulation path constructed by the reactor pressure vessel and the temporary system by a temporary pump provided in the temporary system.
A step of moving the decontamination liquid in and out of the reactor pressure vessel using the upper equipment and the lower equipment to switch the mode of the flow inside the reactor pressure vessel.
including,
Decontamination method. A step of introducing the decontamination liquid from the upper equipment and discharging it from the lower equipment to cause a downflow in which the decontamination liquid drops into at least a part of the inside of the reactor pressure vessel.
A step of introducing the decontamination liquid from the lower equipment and discharging it from the upper equipment to generate an upflow in which the decontamination liquid rises in at least a part of the inside of the reactor pressure vessel.
including,
The decontamination implementation method according to claim 1. A step of cutting the main steam pipe connected to each of the plurality of main steam nozzles as the upper equipment, and
Steps to connect the temporary system to the cut points of each main steam pipe, and
including,
The decontamination method according to claim 1 or 2. The decontamination liquid is passed through the decontamination liquid by using all the main steam nozzles at the same time in the first period, and the decontamination liquid is sequentially used individually in the second period different from the first period. Pass water,
The decontamination implementation method according to claim 3. The superstructure includes at least one of a main steam nozzle, a water supply nozzle, a core spray nozzle, and a head spray nozzle.
The decontamination implementation method according to any one of claims 1 to 4. The infrastructure includes at least one of a control rod drive housing, a neutron flux measurement housing, a reactor pressure vessel drain nozzle, and a reactor recirculation system.
The decontamination implementation method according to any one of claims 1 to 5. During at least a part of the period during which the reactor pressure vessel is chemically decontaminated, the decontamination liquid is continuously passed through using at least one of the control rod drive mechanism housing and the neutron flux measurement housing. The decontamination liquid is intermittently passed through the reactor pressure vessel drain nozzle.
The decontamination implementation method according to claim 6. A step of removing insoluble matter inside the reactor pressure vessel is included before or after the period of chemical decontamination of the reactor pressure vessel.
The decontamination implementation method according to any one of claims 1 to 7. Before the period of chemical decontamination of the reactor pressure vessel, the insoluble matter is passed through a filter while raising the temperature of the water inside the reactor pressure vessel before injecting the decontamination agent. To remove,
The decontamination implementation method according to claim 8. The infrastructure includes at least one of a plurality of control rod drive mechanism housings or a plurality of neutron flux measurement housings.
In the step of removing the insoluble matter,
Using at least a part of the control rod drive mechanism housing or the neutron flux measurement housing, gas is introduced into the reactor pressure vessel to perform bubbling.
The insoluble matter blown up by the bubbling is discharged using at least a part of the control rod drive mechanism housing or the neutron flux measurement housing.
The decontamination method according to claim 8 or 9. Includes steps to measure the dose rates of the control rod drive housing and the neutron flux measurement housing, respectively.
In the step of removing the insoluble matter, the insoluble matter in the control rod drive mechanism housing or the neutron flux measurement housing higher than the average value of the measurement results is removed.
The decontamination implementation method according to claim 10. A temporary system connected to the upper equipment provided at least above the center of the reactor pressure vessel in the vertical direction and the lower equipment provided below the upper equipment, and
A temporary pump provided in the temporary system to circulate the decontamination liquid in a circulation path constructed by the reactor pressure vessel and the temporary system.
A control unit that controls the flow mode inside the reactor pressure vessel by moving the decontamination liquid in and out of the reactor pressure vessel using the upper equipment and the lower equipment.
To prepare
Decontamination implementation device.

Images