JP2015049164A - Nuclear reactor pressure vessel decontamination method and nuclear reactor pressure vessel decontamination system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nuclear reactor pressure vessel decontamination technique capable of realizing a high decontamination effect only by operating a temporary pump without operating a recirculation pump.SOLUTION: A nuclear reactor pressure vessel decontamination method according to an embodiment of the present invention includes: a first decontamination step of injecting a decontamination liquid flowing in from a first supply line 26 in a direction of an inner wall of a nuclear reactor pressure vessel 11 from an upper portion within the nuclear reactor pressure vessel 11, thereby decontaminating an outside of a shroud 12; and a first circulation step flowing out the decontamination liquid flowing down the inner wall of the nuclear reactor pressure vessel 11 from the nuclear reactor pressure vessel 11, and recirculating the decontamination liquid using a temporary pump 21.

Description

  Embodiments of the present invention relate to a decontamination technique for removing oxide films and deposits containing radioactivity generated inside a reactor pressure vessel.

  Chemical decontamination inside the reactor pressure vessel is implemented as a measure to reduce exposure during the entry of workers and the dismantling of the reactor during the construction of the reactor internals.

This chemical decontamination requires a large scale system capacity of several hundred cubic meters, and it is necessary to improve the decontamination effect in a short time.
Further, in chemical decontamination, a decontamination solution dissolves an oxide film or a deposit that is a contaminated surface. The dissolved radioactivity and metal ions are transported to the ion exchange resin and collected. For this reason, decontamination progresses efficiently, so that the linear flow rate of a decontamination liquid is large.

  For this reason, conventionally, for chemical decontamination inside the reactor pressure vessel, a recirculation pump that can secure a large circulation flow rate and can obtain a large linear flow rate is operated, and the decontamination solution is forced to circulate for decontamination. A method of dyeing has been employed (for example, Patent Documents 1 to 4).

Japanese Patent Laid-Open No. 10-48394 JP-A-11-14796 JP 2000-65989 A JP 2008-304353 A

  However, in the decontamination method using the recirculation pump, it is necessary to adjust the circulation flow rate according to the rise in the reactor water level due to the inflow of cooling water supplied to the mechanical seal of the pump into the furnace and the conditions in the reactor. There is a problem that the operation control is complicated.

In addition, when the recirculation pump is not in a state where it can be operated, or when the recirculation system piping is less contaminated than the degree of contamination in the furnace, the decontamination inside the furnace can be performed using only the temporary pump without operating the recirculation pump. There are cases where it must be done.
At this time, a temporary pump having a smaller flow rate than the recirculation pump has a problem that a sufficient linear flow velocity cannot be obtained and a high decontamination effect cannot be obtained.

  The present invention has been made in view of such circumstances, and provides a reactor pressure vessel decontamination technique that realizes a high decontamination effect by operating only a temporary pump without operating a recirculation pump. With the goal.

  In the reactor pressure vessel decontamination method of the present embodiment, the decontamination liquid introduced from the first supply line is ejected from above in the reactor pressure vessel toward the inner wall surface of the reactor pressure vessel. And a first decontamination step for decontaminating the outside of the shroud, and allowing the decontamination liquid accumulated between the inner wall of the reactor pressure vessel and the outside of the shroud to flow out of the reactor pressure vessel, and using a temporary pump And a first circulation step for circulation.

  ADVANTAGE OF THE INVENTION According to this invention, the decontamination technique of the reactor pressure vessel which implement | achieves a high decontamination effect by driving | operation of only a temporary pump, without operating a recirculation pump is provided.

The systematic diagram of the reactor pressure vessel decontamination system which concerns on this embodiment. Explanatory drawing which shows the method of decontaminating the outer side of the shroud in this embodiment. The figure which shows the attachment structure of the splaying applied to this embodiment. Explanatory drawing which shows the method of decontaminating the inner side of the shroud in this embodiment. The figure which shows the decontamination flow of the reactor pressure vessel which concerns on this embodiment. The figure which shows the modification of the decontamination flow of the reactor pressure vessel which concerns on this embodiment. Schematic which shows the bubbling method to the CRD housing of the reactor pressure vessel bottom.

Hereinafter, this embodiment is described based on an accompanying drawing.
FIG. 1 shows a system diagram of a reactor pressure vessel decontamination system 10 (hereinafter referred to as decontamination system 10) according to this embodiment.

  The present embodiment is applied to a nuclear reactor in which the outer side and the inner side of the core shroud are separated. This makes it possible to store the decontamination liquid that has flowed into a cylindrical space (hereinafter referred to as an annulus) formed between the reactor pressure vessel 11 and the shroud 12. Examples of this type of nuclear reactor include a natural circulation boiling water reactor and a boiling water reactor having no jet pump.

  The decontamination system 10 circulates a decontamination solution by a temporary pump 21 provided in a power plant, and chemically decontaminates oxide films and deposits containing radioactivity generated inside the reactor pressure vessel 11.

The decontamination liquid is prepared in the chemical injection tank 32 and is supplied to the temporary circulation line 24 via the chemical injection line stop valve 34 by driving the chemical injection pump 33. And it circulates through the temporary circulation line 24 via the reactor pressure vessel 11.
The decontamination liquid is heated to a predetermined temperature by the heater 22 provided in the temporary circulation line 24, and the circulating temperature is maintained at a high temperature.

  For the metal and radioactivity dissolved in the decontamination liquid, the cation resin tower inlet valve 37 and the cation resin tower outlet valve 39 are kept open for a certain period of time (the temporary circulation line stop valve 23 is adjusted and opened). 35 is passed through and collected.

  In the decontamination system 10, the outer region and the inner region of the shroud 12 are decontaminated separately. Therefore, the temporary circulation line 24 is divided into a first supply line 26 and a second supply line 27 on the inflow side of the decontamination liquid.

  Then, at the time of decontamination of the shroud outer region, the decontamination liquid is caused to flow into the reactor pressure vessel 11 via the first supply line 26. On the other hand, at the time of decontamination of the inner region of the shroud, the second supply line 27 is used. Switching between the two lines is performed by opening and closing the first supply line stop valve 28 and the second supply line stop valve 29.

  At the time of decontamination of the shroud outer region, the first supply line stop valve 28 is opened and the second supply line stop valve 29 is closed. On the other hand, when decontaminating the shroud inner region, the first supply line stop valve 28 is closed and the second supply line stop valve 29 is opened.

  In the decontamination system 10 configured as described above, the decontamination method for the reactor pressure vessel 11 according to the present embodiment is such that the decontamination liquid introduced from the first supply line 26 is atomized from above in the reactor pressure vessel 11. A first decontamination step in which the inner wall and the outer side of the shroud 12 are decontaminated by jetting toward the inner wall surface of the reactor pressure vessel 11, and the decontamination accumulated between the inner wall of the reactor pressure vessel 11 and the outer side of the shroud 12. A first circulation step of causing the liquid to flow out of the reactor pressure vessel 11 and circulating using a temporary pump.

  Furthermore, the step of switching between the first supply line 26 and the second supply line 27, and the decontamination liquid introduced from the second supply line 27 are jetted from the upper side of the shroud 12 to the inside of the shroud 12 so as to move inside the shroud 12. A second decontamination step for decontamination, and a second circulation step for allowing the decontamination liquid accumulated inside the shroud 12 to flow out of the reactor pressure vessel 11 and circulate using the temporary pump 21. Note that either the first decontamination step or the second decontamination step may be executed first.

As described above, the decontamination is performed by dividing the outer region and the inner region of the shroud 12, and the decontamination solution is circulated in each decontamination step. That is, the entire reactor pressure vessel 11 including the shroud 12 is not immersed in the decontamination liquid and the decontamination liquid is circulated for decontamination.
Thereby, the flow volume of the decontamination liquid required for decontamination can be reduced, and sufficient linear flow velocity can be obtained. Therefore, a high decontamination effect can be realized even when only the temporary pump 21 is operated with a smaller flow rate than the recirculation pump.

A method for decontaminating the outer region and the inner region of the shroud 12 will be specifically described.
First, a method for decontaminating the outer region of the shroud 12 will be described with reference to FIG. FIG. 2 is an explanatory view showing the flow of the decontamination liquid at the time of decontamination by enlarging the reactor pressure vessel 11 portion of the decontamination system 10 shown in FIG.

  At the time of decontamination of the shroud outer region, the recirculation water outlet nozzle 14 is in contact with the reactor pressure vessel 11 and the temporary circulation line 24. For this reason, the shroud outer drawing line stop valve 19 is opened to allow the decontamination liquid to flow through the temporary circulation line 24. At this time, the shroud inner drawing line stop valve 20 is closed.

  In addition, although the recirculation piping is connected to the recirculation water outlet nozzle 14, it is good also as a structure which cut | disconnects this connection and connects only the temporary circulation line 24. FIG.

  The first supply line 26 is inserted into the reactor pressure vessel 11 through a nozzle provided in the reactor pressure vessel head (RPV head) 18. Then, the decontamination liquid is supplied to the spraying 30 connected in the reactor pressure vessel 11.

The spraying 30 is provided in the upper part in the reactor pressure vessel 11 and ejects the supplied decontamination liquid to the inner wall of the reactor pressure vessel 11. The spray ring 30 has a ring shape with a circular cross section, and ejects the decontamination liquid toward the inner wall surface of the reactor pressure vessel 11.
The ejected decontamination liquid reaches the inner wall of the reactor pressure vessel 11, forms a liquid film, and flows down the wall surface. Thereby, the whole inner wall of the reactor pressure vessel 11 is decontaminated.

A specific fixing method of the spraying 30 will be described.
The spraying 30 is fixedly installed on the RPV head 18 via a header suspension balance 45. By fixing the spraying 30 to the RPV head 18, the decontamination liquid can be stably ejected from a high position.

Further, at the time of decontamination, since the temperature of the decontamination solution is close to 100 ° C., it is necessary to cover the reactor pressure vessel 11 and close the inside.
The reactor pressure vessel 11 and the RPV head 18 are in a container-lid relationship, respectively. For this reason, by fixing the spray ring 30 to the RPV head 18 side, the flange surface with the reactor pressure vessel 11 main body has better adhesion than the production of a temporary lid for decontamination, and the interior can be stabilized. Can be closed.
Furthermore, by using the RPV head 18, it is possible to effectively use the equipment and to save the trouble of manufacturing a temporary lid.

FIG. 3 shows a mounting configuration of the spraying 30.
The header suspension balance 45 is fixed using a dryer hold-down bracket 46 provided inside the RPV head 18. The spraying 30 is fixed to the header suspension balance 45.
In this way, the spray ring 30 is fixed to the RPV head 18 via the header suspension balance 45 using the dryer hold-down bracket 46.

Returning to FIG. 2, the description will be continued.
When a steam dryer and a steam / water separator (not shown) are taken out, the inner wall of the reactor pressure vessel 11 becomes a decontamination target above the shroud 12.

  Compared with the case where the entire inner wall is immersed in the decontamination liquid by decontaminating the inner wall by flowing down the decontamination liquid from the upper part of the reactor pressure vessel 11 using the splaying 30. The water level at the time can be lowered. Furthermore, the amount of decontamination liquid necessary for decontamination can be greatly reduced.

In addition, when the liquid film of the decontamination solution becomes thin in the process of flowing down the inner wall of the reactor pressure vessel 11 or evaporates, the decontamination effect is reduced. For this reason, the spraying 30 ejects the decontamination liquid so that the liquid film thickness of the decontamination liquid is maintained. For example, when the inner diameter of the reactor pressure vessel 11 is 5.5 m and the flow-down distance is 8 m, the liquid film can be maintained with an ejection flow rate of about 200 m ³ / h.

  The decontamination liquid flowing down the inner wall of the reactor pressure vessel 11 is accumulated in the annulus. Thereby, the outer side (outer wall) of the shroud 12 is immersed and decontaminated in the decontamination liquid of the annulus part.

  The decontamination liquid stored in the annulus portion flows out from the recirculation water outlet nozzle 14 and is returned again to the first supply line 26 via the temporary circulation line 24. By such circulation of the decontamination solution, the outer region of the shroud 12 is decontaminated.

At the time of decontamination of the outer area of the shroud, the inner area of the shroud 12 is not filled with the decontamination liquid, and the circulation of the decontamination liquid is only the annulus portion. Thereby, the circulation flow rate of the decontamination liquid required for decontamination can be reduced, and sufficient linear flow velocity can be obtained.
Therefore, it is possible to achieve a high decontamination effect even when only the temporary pump 21 (FIG. 1) is operated with a smaller flow rate than the recirculation pump.

  In addition, at the time of decontamination of the shroud outer region, a part of the decontamination liquid ejected from the spray ring 30 or a part of the decontamination liquid stored in the annulus part may flow into the shroud 12. The inflowing decontamination solution stays at the bottom of the reactor pressure vessel 11.

  In this case, if the shroud inner region is decontaminated following the shroud outer region, it can be used as a decontamination solution, so there is no need to cope with it. On the other hand, when the decontamination is not continued, the reactor pressure vessel (RPV) bottom drain line stop valve 43 is closed and discharged from the reactor pressure vessel (RPV) bottom drain line 17 via the drain valve 44 to the outside of the system. There is a need to.

  Next, a method for decontaminating the inner region of the shroud 12 will be described with reference to FIG. FIG. 4 is an explanatory diagram showing the flow of the decontamination liquid during decontamination of the shroud inner region.

  At the time of decontamination of the inner area of the shroud, the reactor pressure vessel 11 and the temporary circulation line 24 are interlinked with the recirculation water inlet nozzle 13, the in-core monitor (ICM) housing 15, the core differential pressure gauge nozzle 16, and the reactor pressure vessel 11. The RPV bottom drain line 17 comes out from the bottom of the bottom. Moreover, you may comprise also from a part of control rod drive mechanism (CRD) housing (illustration omitted) of the reactor pressure vessel 11 bottom part as needed.

  For this reason, the shroud inner drawing line stop valve 20 is opened, and the decontamination liquid is circulated through the temporary circulation line 24. At this time, the shroud outer drawing line stop valve 19 is closed.

  The ICM housing 15 is removed from the monitor and connected to the temporary circulation line 24 at the frenzy part. The core differential pressure gauge nozzle 16 and the RPV bottom drain line 17 are cut outside the furnace, welded to the flange, and connected to the temporary circulation line 24. Is done.

  Although recirculation piping is connected to the recirculation water inlet nozzle 13 (usually, three locations), it is possible to disconnect this connection and connect only the temporary circulation line 24.

In addition, in the above-mentioned, the structure which isolate | separates the recirculation water exit nozzle 14 from recirculation piping was shown. By disconnecting the recirculation water inlet nozzle 13 and the recirculation water outlet nozzle 14 from the recirculation pipe, the temporary circulation system and the recirculation system are separated.
Thereby, during the decontamination of the reactor pressure vessel 11, maintenance work in the reactor containment vessel can be performed in parallel.

First, switching from the first supply line 26 to the second supply line 27 is performed.
The second supply line 27 is inserted into the reactor pressure vessel 11 via a nozzle provided in the RPV head 18, and supplies the decontamination liquid to the spray nozzle 31 connected in the reactor pressure vessel 11. .

  The spray nozzle 31 ejects the decontamination liquid from above the shroud 12 to the inside of the shroud 12. Thereby, the whole inside of the shroud 12 including an internal structure is decontaminated.

  In addition, the spray nozzle 31 should just be able to eject a decontamination liquid to the whole inner side of the shroud 12, and a shape, a structure, etc. will not ask | require. As for the fixing method, a configuration supported by the second supply line 27, a configuration held by the flange portion of the shroud 12, and the like are conceivable.

  The decontamination water accumulated inside the shroud 12 flows out from the recirculation water inlet nozzle 13 and the like, and is returned to the second supply line 27 again through the temporary circulation line 24. By such a circulation of the decontamination liquid, the inner region of the shroud 12 is decontaminated.

  At the time of decontamination of the inner area of the shroud, the outside of the shroud 12 is not filled with the decontamination liquid, and the circulation of the decontamination liquid is only inside the shroud 12. Thereby, the flow volume of the decontamination liquid required for decontamination can be reduced, and sufficient linear flow velocity can be obtained. Therefore, a high decontamination effect can be realized even when only the temporary pump 21 is operated with a smaller flow rate than the recirculation pump.

  As described above, by temporarily decontaminating the outer region and the inner region of the shroud 12 and circulating the decontamination liquid in each decontamination step, only the temporary pump 21 having a smaller flow rate than the recirculation pump. Even in this operation, a high decontamination effect can be realized.

Specifically, in general, a system capacity of 200 to 300 m ³ is required for decontamination inside the reactor pressure vessel 11, but by using this embodiment, the system capacity can be reduced to 40 to 70 m ^3. It becomes possible.
For this reason, the temporary pump 21 is not required to be large, and in the case of a 400 MWe class boiling water reactor, a sufficient decontamination effect can be obtained with about two temporary pumps 21 of about 60 m ³ / h.

  In addition, since the high decontamination effect can be obtained by operating only the temporary pump 21, the operation of the recirculation pump becomes unnecessary, and the operation control necessary for the operation of the recirculation pump and the workload of the operator accompanying it are increased. Eliminates operational risks.

Next, the multi-step chemical decontamination method applied to this embodiment will be described.
The multi-step chemical decontamination method is a method of performing decontamination by alternately repeating an oxidation step of injecting an oxidizing agent into a decontamination solution and a reduction step of injecting a reducing agent. By repeatedly performing an oxidation process and a reduction process on an oxide film composed of an iron-based outer layer containing chromium and an chromium-based inner layer, the oxide film is almost dissolved and removed, and a high decontamination rate is obtained.

  FIG. 5 is a diagram showing a decontamination flow of chemical decontamination applied in the present embodiment (see FIG. 1 as appropriate). Here, the flow of decontamination in order of the outer region and the inner region of the shroud 12 will be described, and the case where ozone is used as the oxidizing agent and oxalic acid is used as the reducing agent will be described.

  First, the temporary circulation system is filled with water, and after the temperature is raised by the temporary pump 21 and the heater 22, the oxalic acid solution prepared in the chemical injection tank 32 is injected into the temporary circulation line 24 by the chemical injection pump 33 (S10 to S10). S12).

Then, a decontamination solution (oxalic acid solution) is caused to flow into the reactor pressure vessel 11 from the first supply line 26 to perform decontamination outside the shroud, which is a reduction process (first cycle decontamination: S13). .
At this time, the cation resin tower inlet valve 37 and the cation resin tower outlet valve 39 are opened for a certain period of time, and the metal and radioactivity dissolved by decontamination are collected in the cation resin tower 35 through water.

  When the dissolution of the radioactivity is stopped, the decontaminating agent decomposing apparatus 25 is activated to decompose oxalic acid (S14).

  Next, the ozone generator 41 is started and the ozone injection valve 42 is opened to inject ozone into the temporary circulation line 24 (S15). In addition, it is good also as a structure which inject | pours the ozone water prepared with the chemical injection tank 32 into the temporary circulation line 24 with the chemical injection pump 33. FIG.

  And decontamination liquid (ozone water) is made to flow into the reactor pressure vessel 11 from the 1st supply line 26, and this becomes an oxidation process (2nd cycle oxidation: S16).

  After the oxidation process is completed, the process proceeds to the reduction process again. Note that ozone does not require a decomposition step because it decomposes itself.

Similar to the first cycle decontamination, a decontamination solution (oxalic acid solution) is caused to flow into the reactor pressure vessel 11 from the first supply line 26 (S17), and decontamination of the outer region of the shroud is performed (second cycle decontamination). Dyeing: S18).
When the dissolution of radioactivity is stopped, the decontaminating agent decomposing apparatus 25 is activated to decompose oxalic acid (S19).

Although the dose rate can be reduced with the progress of decontamination, the oxidation process and the reduction process are repeated as necessary. Ultimately, final purification is performed after oxalic acid is decomposed.
In the final purification, the mixed water resin tower inlet valve 38 and the mixed bed resin tower outlet valve 40 are opened and water is passed through the mixed bed resin tower 36 to purify the system water (S20).

Subsequently, the first supply line 26 is switched to the second supply line 27, and water is transferred to the second supply line 27 (S21, S22).
And decontamination of a shroud inner side area | region is performed by the method similar to the time of decontamination of a shroud outer side area | region (S23-S32).

Thus, at the time of decontamination of the shroud outer region and the shroud inner region, a high decontamination rate can be obtained by alternately repeating the oxidation step and the reduction step.
In addition, in FIG. 5, although the structure which decontaminates the outer area | region of the shroud 12 first was shown, it is good also as a structure which decontaminates the inner area | region of the shroud 12 previously.

  FIG. 6 is a view showing a modified example of the decontamination flow shown in FIG. 5 (see FIG. 1 as appropriate). The same steps as those in FIG. 5 are denoted by the same reference numerals, and the description of the overlapping operations is omitted.

This configuration is characterized in that the first supply line 26 and the second supply line 27 are switched during the oxidation process or the reduction process.
For example, during the oxidation process in the shroud inner area (S28), the second supply line 27 is switched to the first supply line 26 (S21), and the oxidation process is continuously performed in the shroud outer area (S16).

  In this way, by switching between the outside and inside of the shroud 12 and using the decontamination liquid in the same process, it is possible to reduce the number of times the chemical solution is changed, and to reduce the generation amount of the decontamination liquid waste. Can do.

  FIG. 7 shows an example of a method for injecting gas into the bottom of the reactor pressure vessel 11, and a bubbling method to a control rod drive mechanism (CRD) housing 47 provided at the bottom of the reactor pressure vessel 11. Is shown.

At the bottom of the reactor pressure vessel 11 is a CRD housing 47, which is equipped with a control rod drive piston 48.
Since the CRD housing 47 is in a built-in state, the CRD housing 47 tends to be a decontamination liquid retaining portion. Bubbling is performed on this portion by injecting a gas such as air from the water pressure control unit (HCU) 49 side using the air header 58 in the power plant.

A specific method will be described.
First, residual water in the control rod insertion / extraction piping is drained by valve operation on the HCU side in conjunction with draining of the furnace water before decontamination is started.
Thereafter, the control rod withdrawal side vent valve 53, the control rod withdrawal side HCU isolation valve 55, the control rod insertion side vent valve 54, and the control rod insertion side HCU isolation valve 56 are fully closed.

Next, an air injection hose 59 is connected to the connection joint 57 at the tip of the control rod pull-out side vent valve 53 so that air is pressurized from the air header 58.
At the time of decontamination, the control rod extraction side vent valve 53 is appropriately opened to inject air into the control rod extraction water pipe 51.

  The air injected into the CRD loses its escape because the control rod insertion side vent valve 54 and the control rod insertion side HCU isolation valve 56 on the control rod insertion water pipe 52 side are fully closed. Leaks from and rises toward the core. By continuously performing this air injection, the decontamination solution staying in the CRD is bubbled. Reference numeral 50 denotes a control rod drive water pump.

  Accordingly, stirring and replacement of the staying decontamination liquid is promoted and the CRD structure is decontaminated, so that a high decontamination effect is obtained.

  According to the reactor pressure vessel decontamination method described above, the outer region and inner region of the shroud are separately decontaminated, so that a high decontamination can be achieved even when only the temporary pump is operated without operating the recirculation pump. It is possible to achieve a dyeing effect.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
Moreover, this embodiment can be applied by isolating the inner side and the outer side of the shroud by closing the communication part before the decontamination operation even in a nuclear reactor in which the inner side and the outer side of the shroud are not isolated. It becomes.

  DESCRIPTION OF SYMBOLS 10 ... Reactor pressure vessel decontamination system, 11 ... Reactor pressure vessel, 12 ... Shroud, 13 ... Recirculation water inlet nozzle, 14 ... Recirculation water outlet nozzle, 15 ... In-core monitor (ICM) housing, 16 ... Core difference Pressure gauge nozzle, 17 ... Nuclear pressure vessel (RPV) bottom drain line, 18 ... Reactor pressure vessel (RPV) head, 19 ... Shroud outer drawing line stop valve, 20 ... Shroud inner drawing line stop valve, 21 ... Temporary pump, 22 DESCRIPTION OF SYMBOLS ... Heater, 23 ... Temporary circulation line stop valve, 24 ... Temporary circulation line, 25 ... Decontamination agent decomposition device, 26 ... First supply line, 27 ... Second supply line, 28 ... First supply line stop valve, 29 ... Second supply line stop valve, 30 ... spray ring, 31 ... spray nozzle, 32 ... chemical injection tank, 33 ... chemical injection pump, 34 ... chemical injection line stop Valve 35, cationic resin tower, 36 ... mixed bed resin tower, 37 ... cationic resin tower inlet valve, 38 ... mixed bed resin tower inlet valve, 39 ... cationic resin tower outlet valve, 40 ... mixed bed resin tower outlet valve, 41 DESCRIPTION OF SYMBOLS ... Ozone generator, 42 ... Ozone injection valve, 43 ... Nuclear pressure vessel (RPV) bottom drain line stop valve, 44 ... Drain valve, 45 ... Header hanging balance, 46 ... Dryer hold down bracket, 47 ... Control rod drive mechanism ( CRD) housing, 48 ... control rod drive piston, 49 ... water pressure control unit (HCU), 50 ... control rod drive water pump, 51 ... control rod extraction water piping, 52 ... control rod insertion water piping, 53 ... control rod extraction side Vent valve, 54 ... Control rod insertion side vent valve, 55 ... Control rod withdrawal side HCU isolation valve, 56 ... Control rod insertion side HCU isolation valve, 57 ... Connection joint, 58 ... Air header, 59 ... Empty Injection hose.

Claims (11)

A first decontamination step of decontaminating the inner wall and the outside of the shroud by ejecting the decontamination liquid introduced from the first supply line from above in the reactor pressure vessel toward the inner wall surface of the reactor pressure vessel; ,
A first circulation step of causing the decontamination liquid accumulated between the inner wall of the reactor pressure vessel and the outside of the shroud to flow out of the reactor pressure vessel and circulating using a temporary pump;
A decontamination method for a reactor pressure vessel, comprising: Switching between the first supply line and the second supply line;
A second decontamination step of decontaminating the inside of the shroud by ejecting the decontamination liquid introduced from the second supply line from above the shroud to the inside of the shroud;
A second circulation step of causing the decontamination liquid accumulated inside the shroud to flow out of the reactor pressure vessel and circulating using the temporary pump;
The reactor pressure vessel decontamination method according to claim 1, further comprising:   The recirculation water inlet nozzle and the recirculation water outlet nozzle of the reactor pressure vessel are characterized by disconnecting a recirculation system pipe and connecting a temporary circulation line through which the decontamination liquid is circulated by the temporary pump. The method for decontaminating a reactor pressure vessel according to claim 1 or claim 2. The first decontamination step includes
The said decontamination liquid spouts by spraying which is provided in the upper part in the said reactor pressure vessel, and injects the said decontamination liquid to the inner wall of the said reactor pressure vessel. The decontamination method for a reactor pressure vessel according to any one of the preceding claims.   The method for decontaminating a reactor pressure vessel according to claim 4, wherein the spraying is fixed to a reactor pressure vessel head. The first decontamination step and the second decontamination step include
The reactor pressure vessel according to any one of claims 1 to 5, wherein an oxidation step of injecting an oxidant into the decontamination solution and a reduction step of injecting a reducing agent are alternately repeated. Decontamination method.   The method for decontaminating a reactor pressure vessel according to claim 6, wherein the first supply line and the second supply line are switched during the oxidation step or the reduction step.   The reactor pressure according to any one of claims 1 to 7, further comprising a step of injecting a gas into a bottom of the reactor pressure vessel and bubbling the staying decontamination liquid. Container decontamination method.   2. The reactor pressure vessel decontamination method according to claim 1, further comprising a step of closing the communicating portion before the decontamination in the case of a nuclear reactor in which the inside and the outside of the shroud communicate with each other. Spraying provided above the inside of the reactor pressure vessel and ejecting the decontamination liquid introduced from the first supply line toward the inner wall surface of the reactor pressure vessel;
A temporary pump for circulating the decontamination liquid that has flowed out of the reactor pressure vessel;
A reactor pressure vessel decontamination system comprising:   The spray nozzle further includes a spray nozzle that switches between the first supply line and the second supply line and ejects the decontamination liquid flowing in from the second supply line from above the shroud to the inside of the shroud. The decontamination system for a reactor pressure vessel according to claim 10.

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