JP2011169649A - Nuclear reactor well gate and nuclear reactor inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology easily and speedily completing inspection of piping to submerged valves, or the submerged valves. <P>SOLUTION: The nuclear reactor well gate is equipped with: an approximately disk-shaped partition 202 at near an outer edge of which two or more attaching holes are formed; an airtight sealing section (elastic packing 210) which is provided inside of the two or more attaching holes of the partition 202 and seals a gap between a contact surface; a duct 220 connected to the partition; and an air intake and exhaust system 228 intaking and exhausting air through the duct 220. The well gate is attached to a flange section 104 of a nuclear reactor pressure vessel 100 via two or more attaching holes to seal an opening 100a of the nuclear reactor pressure vessel 100 under a state of filling the nuclear reactor well 134 with water. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pipe to a submergence valve connected to a reactor pressure vessel, a reactor well gate for inspecting the submergence valve, and a nuclear reactor inspection method using the reactor well gate.

  In boiling water reactors (BWRs) and advanced boiling water reactors (ABWRs), the core is housed in a reactor pressure vessel, and the reactor pressure vessel is stored in the reactor containment vessel. Be contained. Cooling water (light water) is poured into the reactor pressure vessel, and high-temperature and high-pressure steam is generated by the heat generated from the reactor core, which is used as power for rotating the turbine.

  In the nuclear reactor (nuclear power plant) as described above, in order to operate safely, periodic inspection is obliged every predetermined period. Such inspection includes inspection of piping up to the submergence valve connected to the reactor pressure vessel and submergence valve. The submergence valve is the first valve on the pipe connected to the reactor pressure vessel, and cannot be checked unless water is drained from the reactor pressure vessel.

  In general, pipes up to the submergence valve and submergence valve inspection, repair, or modification (hereinafter referred to as inspection, etc.) are performed after reactor removal, spent fuel pool (SFP) and dryer separator pool. (DSP: Dryer Separator Pool) From the state where water is stretched, insert the SFP gate and DSP gate, drain the water in the reactor well, and then drain the water in the reactor pressure vessel. It was.

  In some cases, pipes up to the submergence valve and inspection of the submergence valve can be inspected by remote control from a fuel handling machine (FHM) that runs on rails laid on the operation floor (submersion valve). ) Was closed with a nozzle plug, and the water in the pipe was discharged to a low-conductivity waste liquid treatment system (LCW system).

  However, in any of the above-described methods, it takes a long time to complete draining. On the other hand, periodic inspections of nuclear power plants are carried out by stopping the operation of the nuclear reactor and mobilizing thousands of workers, etc., so that inspections can be completed as quickly and efficiently as possible. Was requested.

  Therefore, the group of the present inventors has developed a reactor well cover that is installed on the operation floor and hermetically seals the reactor well, and can continuously drain the reactor well and the reactor pressure vessel (in one step). I made it. As a result, the time required for draining can be greatly shortened (see Patent Document 1).

Japanese Patent Application No. 2009-255709

  However, there is still a demand for a technique for more efficiently (rapidly) completing the piping to the submergence valve and the inspection of the submergence valve. Then, an object of this invention is to provide the technique which can complete the inspection to piping and a water immersion valve to a water immersion valve more simply and rapidly.

  In order to solve the above-mentioned problems, the present inventors have intensively studied, and if the reactor well and the opening of the reactor pressure vessel can be sealed, the piping up to the submersion valve without draining the water stretched on the reactor well I thought that I could carry out the inspection of the submergence valve. Through further research, the inventors have found a specific structure of the gate and completed the present invention.

  That is, a typical configuration of a reactor well gate according to the present invention is a substantially disk-shaped partition wall in which a plurality of mounting holes are formed in the vicinity of the outer edge, and inside the plurality of mounting holes in the partition wall. Provided with an airtight seal portion that closes the gap between the contact surface, a duct connected to the partition wall, and an air intake / exhaust system that intakes and exhausts air through the duct, and in a state where water is stretched in the reactor well, It is attached to the flange portion of the reactor pressure vessel through a plurality of attachment holes, and the opening of the reactor pressure vessel is sealed.

  According to this configuration, it is possible to inspect the pipes up to the submergence valve and the submergence valve without draining the reactor well. Therefore, the total amount of drainage is reduced, and the time required for draining (water filling) can be further shortened. In addition, the reduction of the total drainage amount leads to a reduction in the burden on the radioactive liquid waste treatment system. In addition, since the water stretched in the reactor well shields the radiation from inside the reactor pressure vessel, the exposure dose on the operation floor can be kept extremely low. Compared with the prior art, there is no need to insert an SFP gate separating the reactor well from the spent fuel pool and a DSP gate separating the reactor well from the dryer separator pool.

  A sharp guide pin replaced with a part of a plurality of flange bolts for mounting an RPV head (RPV: Reactor Pressure Vessel) installed on the flange, and a mounting bolt with a small diameter on the upper side, The reactor well gate may have a flange bolt insertion hole through which the flange bolt is inserted, a guide pin insertion hole through which the guide pin is inserted, and a mounting bolt insertion hole through which the installation bolt is inserted as a plurality of mounting holes. . Thereby, the said reactor well gate can be easily attached to the flange part of a reactor pressure vessel.

  The mounting bolt may have a lower end diameter that is substantially the same as that of the flange bolt, and an upper end diameter that is substantially the same as or less than that of the shroud head bolt of the reactor pressure vessel. By setting the diameter of the upper end of the mounting bolt to be equal to or smaller than the diameter of the shroud head bolt that has been proven to be tightened by remote operation, the nut can be securely fastened to the upper end of the mounting bolt by remote operation.

  The hermetic seal portion may be an elastic packing, and the partition wall may have a protruding portion protruding downward in contact with the flange portion in the vicinity of the outer edge thereof. Thereby, it is possible to suitably seal the opening of the reactor pressure vessel.

  The airtight seal part may be an air packing and an air packing expansion part that supplies air to the air packing. Thereby, it is possible to suitably seal the opening of the reactor pressure vessel.

  The partition wall may have a protective member in the vicinity of the outer edge for preventing damage to the flange portion when contacting the flange portion. Thereby, it is possible to avoid the damage of the flange portion and attach the reactor well gate.

  In order to solve the above problems, a typical configuration of a nuclear reactor inspection method according to the present invention includes a first step of sealing an opening of a reactor pressure vessel in a state where water is stretched in a reactor well, A second step for draining water from the reactor pressure vessel, a third step for inspecting, repairing or modifying the submergence valve connected to the reactor pressure vessel and the submergence valve; after the third step; The method includes a fourth step of refilling the reactor pressure vessel with water and a fifth step of uncovering the opening.

  According to such a configuration, it is possible to complete the piping up to the submergence valve and the inspection of the submergence valve more easily and quickly. Further, it is possible to significantly reduce the total time required for water filling for the fuel loading operation after completion of inspection and the like and opening of the opening of the reactor pressure vessel.

  In the first step, a part of the plurality of flange bolts for mounting the RPV head standing on the flange portion of the reactor pressure vessel is replaced with a sharp guide pin and a mounting bolt having a small diameter on the upper side, and the flange bolt and guide A reactor well gate having a substantially disc-shaped partition wall through which a pin and a mounting bolt are inserted as a main body is placed on the flange, a nut is fastened to the mounting bolt, and the opening is sealed with the reactor well gate. . Thereby, it is possible to suitably seal the opening of the reactor pressure vessel.

  The reactor well gate includes a duct and an air intake / exhaust system that performs intake / exhaust of air through the duct. In the second step, the air intake / exhaust system passes through the duct as the water level of the reactor pressure vessel decreases. In order to maintain the negative pressure inside the reactor pressure vessel before the air is pumped into the reactor pressure vessel and the drainage outside the reactor pressure vessel shroud is completed, the air intake / exhaust system is connected to the air through the duct. In the fourth step, the air intake / exhaust system may extract the air inside the reactor pressure vessel through the duct as the water level of the reactor pressure vessel rises. This makes it possible to suitably drain and fill the reactor pressure vessel without fear of releasing contaminated air.

  In the second step, water outside the reactor pressure vessel shroud is drawn from the nozzle connected to the lower part of the reactor pressure vessel to the suppression pool via the reactor recirculation system and the residual heat removal system, and the shroud It is preferable to drain the water from the front side of the reactor coolant purification system pump to the low-conductivity waste liquid treatment system via the bottom drain pipe of the reactor pressure vessel. Thereby, the water outside the shroud can be quickly drained due to the difference in water level (drop) from the suppression pool, and the water inside the shroud can also be drained to the low-conductivity waste liquid treatment system. In draining water, a pump or the like is not used, and therefore it is not necessary to consider an effective suction head (NPSH) of the pump.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which can complete | finish the inspection to piping to a water immersion valve connected to a nuclear reactor pressure vessel and a water immersion valve more simply and rapidly can be provided.

It is a figure explaining a nuclear reactor pressure vessel. It is a figure explaining a reactor pressure vessel, a reactor well, a spent fuel pool, and a dryer separator pool. It is a figure explaining a flange bolt, a guide pin, and a mounting bolt. It is a figure explaining the reactor well gate concerning this embodiment. It is a figure explaining attachment to the flange part of the reactor well gate of FIG. It is a figure explaining attachment to the flange part of the reactor well gate of FIG. It is a figure which illustrates other examples of the nuclear reactor well gate concerning this embodiment. It is a figure explaining the airtight seal part of the reactor well gate of FIG. It is a flowchart which illustrates the nuclear reactor inspection method concerning this embodiment. FIG. 3 is a schematic view illustrating a reactor pressure vessel, a reactor well, a spent fuel pool and a dryer separator pool after fuel removal work, and each system. It is a figure which illustrates the state which attached the reactor well gate to the flange part of the reactor pressure vessel of FIG. It is a figure which illustrates the state which drained the water outside the shroud of the reactor pressure vessel of FIG. It is a figure which illustrates the state which drained the water in the shroud of the reactor pressure vessel of FIG. FIG. 14 is a diagram illustrating a state in which water has been added to the reactor pressure vessel of FIG. 13 again. It is a figure explaining the piping to the conventional submergence valve as a comparative example, and the inspection method of a submergence valve. It is a figure explaining the piping to the conventional submergence valve as a comparative example, and the inspection method of a submergence valve.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

[Reactor pressure vessel]
FIG. 1 is a diagram for explaining a reactor pressure vessel. Hereinafter, a boiling water reactor (BWR) will be described as an example for easy understanding, but the present embodiment can also be applied to an improved boiling water reactor (ABWR).

  As illustrated in FIG. 1, a BWR reactor pressure vessel 100 is a vessel that accommodates about 764 fuel assemblies 102 in which fuel rods made of uranium or the like are bundled. An edge portion called a flange portion 104 is formed at the upper end of the reactor pressure vessel 100, and the RPV head 106 is attached by a flange bolt 104 a standing on the flange portion 104.

  The fuel assembly 102 accommodated in the reactor pressure vessel 100 reaches criticality, and heats water (reactor water) filled in the vessel to generate steam. Between the fuel assemblies 102, the control rod 112 is taken in and out through the inside of the control rod guide tube 110 by the control rod driving mechanism 108. The control rod 112 is made of boron (B), cadmium (Cd), hafnium (Hf), etc., which have a large neutron absorption effect, and adjusts the number of neutrons so as to constantly maintain the fission chain reaction.

  The fuel assembly 102 (core) is surrounded by a shroud 114. Outside the shroud 114, a jet pump nozzle 116 for injecting water cooled by a nuclear reactor recirculation system (PLR system) into the core is provided. The jet pump nozzle 116 is for the purpose of adjusting the reactor power, changes the water circulated by the reactor recirculation system into a jet water flow, and injects water into the core while enclosing the surrounding water. Near the jet pump nozzle 116, an N1 nozzle 118 of the reactor recirculation system connected to the reactor pressure vessel 100 is provided.

  Water supply to the core is also performed from the core sparger 120 and the water sparger 122. The core spare purger 120 is a part of a core spray system that injects cooling water into the core in the event of a coolant loss accident, and is disposed on the inner upper portion of the shroud 114. The core place purger 120 is a sprinkler pipe having about 600 jet nozzles.

  The water supply sparger 122 is a sprinkler pipe having about 100 jet nozzles that are divided into four parts on the entire inner periphery of the reactor pressure vessel 100. The water supply sparger 122 injects water fed from the main water supply pipe toward the reactor core.

  On the other hand, the upper part of the fuel assembly 102 is supported by the upper lattice plate 124. A shroud head 126 that is a lid of the shroud 114 is provided on the upper lattice plate 124.

  The shroud head 126 is fixed by a shroud head bolt 128. Thereby, the shroud head 126 is prevented from being lifted or displaced in the event of a disaster such as an earthquake. The shroud head bolt 128 is integrated with the steam separator 130 via a fastened nut. The steam separator 130 is a device that removes water droplets contained in the generated steam.

  A steam dryer 132 is provided on the steam separator 130. The steam dryer 132 reduces the moisture content of the steam supplied from the steam separator 130 and supplies the steam to a power generation turbine (not shown) through the main steam pipe 133.

[Reactor well, spent fuel pool and dryer separator pool]
FIG. 2 is a diagram illustrating a reactor pressure vessel, a reactor well, a spent fuel pool, and a dryer separator pool. As illustrated in FIG. 2, a substantially circular reactor well 134 is provided above the reactor pressure vessel 100 as viewed from above. The reactor well 134 is connected on one side to a substantially square spent fuel pool 136 (SFP) and on the other side to a substantially square dryer separator pool 138 (DSP).

  Upper portions of the reactor well 134, the spent fuel pool 136 and the dryer separator pool 138 are connected to the operation floor 140. The operation floor 140 is provided with a fuel changer 142 (FHM) and its rails 144. Further, an overhead crane 146 (see FIG. 10) is provided on the upper portion of the operation floor 140. The refueling machine 142 and the overhead crane 146 remove and install the RPV head 106, the steam dryer 132, and the steam separator 130 of the reactor pressure vessel 100, and move various devices on the operation floor 140 during the periodic inspection. Used in cases.

[Reactor well gate]
FIG. 3 is a diagram illustrating the flange bolt, the guide pin, and the mounting bolt. FIG. 3A is an enlarged view of the flange portion 104 of the reactor pressure vessel 100. As illustrated in FIG. 3A, a plurality of flange bolts 104 a are erected on the flange portion 104. The flange bolt 104a can be removed from the fuel exchanger 142 by remotely operating a dedicated fitting tool (not shown). When the flange bolt 104a is removed, the screw hole 104b of the flange portion 104 is exposed.

  FIG. 3B is a diagram illustrating the external appearance of the flange bolt 104 a, the guide pin 148, and the mounting bolt 150. As illustrated in FIG. 3B, the flange bolt 104a is a so-called stud bolt in which an upper end and a lower end are threaded. The guide pin 148 is a conical sharp pin that can be fastened to the screw hole 104b. The mounting bolt 150 is a bolt having a two-stage diameter. Specifically, the diameter of the lower end is the same as that of the flange bolt 104a so as to be fastened to the screw hole 104b, and the diameter of the upper end is the same as that of the shroud head bolt 128. By matching the diameter of the mounting bolt 150 with the shroud head bolt 128, an operator can use the T-type nut tightening jig 224 for the shroud head bolt 128 (long socket wrench; see FIG. 6 (d)). The gate 200 can be attached and detached.

  FIG. 3C is a view for explaining the removal position of the flange bolt 104a. FIG. 3D is a diagram illustrating a state in which the guide pin 148 and the mounting bolt 150 are attached to FIG. In this embodiment, in order to attach the reactor well gate 200 described later to the flange portion 104, a part of the flange bolt 104a is removed and replaced with the guide pin 148 and the attachment bolt 150 described above.

  That is, as illustrated in FIG. 3C, the flange bolt 104 a to be replaced with the guide pin 148 and the mounting bolt 150 is removed from the flange portion 104. Further, the flange bolt 104a in the region 152 that becomes an obstacle during the fuel transfer operation is removed from the flange portion 104.

  Then, as illustrated in FIG. 3D, the guide pin 148 and the mounting bolt 150 are attached to the flange portion 104. Preferably, three or more guide pins 148 are attached at equal positions, and four or more attachment bolts 150 are attached at equal positions.

  FIG. 4 is a diagram for explaining a reactor well gate according to the present embodiment. FIG. 4A is a diagram illustrating the appearance of the surface side of the reactor well gate 200, and FIG. 4B is a diagram illustrating the appearance of the back side of the reactor well gate 200.

  As illustrated in FIG. 4A, the main body portion of the reactor well gate 200 is formed by a substantially disc-shaped partition wall 202. On the surface side of the partition wall 202, ribs 202a are erected in a lattice shape in order to have resistance against water pressure. In addition, a suspension piece 204 is provided to be lifted by the overhead crane 146.

  Near the outer edge of the partition wall 202, a plurality of mounting holes are formed. Specifically, a flange bolt insertion hole 206b for inserting the flange bolt 104a, a guide pin insertion hole 206c for inserting the guide pin 148, and a mounting bolt insertion hole 206d for inserting the mounting bolt 150 are formed. An indicator hole 206a is formed in the vicinity of the mounting bolt insertion hole 206d.

  The flange bolt insertion hole 206b may be formed slightly larger than the diameter of the flange bolt 104a. That is, the flange bolt 104a used for mounting the RPV head 106 is prevented from being damaged by ensuring a sufficient gap between the flange bolt insertion hole 206b and the flange bolt 104a when the flange bolt 104a is inserted. .

  Near the center of the partition wall 202, a duct nozzle 208a to which one side of the duct 220 is connected by a joint or the like is provided. The duct 220 is a lightweight tube having flexibility such as a pressure hose and having a cross-sectional area that is not excessively deformed and blocked even when subjected to external pressure in water. It connects with the air intake / exhaust system 228 (refer FIG. 10) to perform. The details of the air intake / exhaust system 228 will be described later.

  A device mounting nozzle (hereinafter referred to as a device mounting nozzle 208b) is provided around the duct nozzle 208a. A monitoring camera 222, illumination, a water level gauge, and the like are attached to the device mounting nozzle 208b.

  As illustrated in FIG. 4B, an airtight seal portion that closes a gap with the flange portion 104 (contact surface) is provided on the back side of the partition wall 202 inside the plurality of mounting holes. Here, the elastic packing 210 is used as an airtight seal portion.

  In the vicinity of the outer edge of the partition wall 202, a protruding portion 210a protruding downward is formed. The protruding portion 210 a plays a role of preventing excessive compression of the elastic packing 210 to the flange portion 104. The protrusion 210a may be formed over the entire circumference or may be formed partially.

  The amount of compression of the elastic packing 210 is measured by an indicator 226 attached to the indicator hole 206a. As the indicator 226, for example, a bar-shaped metal with stoppers that are considerably longer than the thickness of the partition wall 202 and provided with stoppers can be used. If the scale of the indicator 226 is recorded in a state where the lower end of the elastic packing 210 and the lower end of the indicator 226 are horizontally aligned in advance, the amount of compression of the elastic packing 210 is determined by taking the difference from the scale of the indicator 226 during compression. Can be measured.

  5 and 6 are views for explaining the attachment of the reactor well gate to the flange portion. As illustrated in FIGS. 5A to 5C, the reactor well gate 200 is lifted by the overhead crane 146, and is first hung so that the guide pin 148 is inserted into the guide pin insertion hole 206c.

  As illustrated in FIGS. 5D to 5F, when the guide pin 148 is passed through the guide pin insertion hole 206c, this serves as a guide, and the flange bolt 104a is inserted into the flange bolt insertion hole 206b. The mounting bolt 150 is inserted through 206d.

  As illustrated in FIGS. 6A to 6C, the reactor well gate 200 is placed (sitting) on the flange portion 104 as described above. Since the flange portion 104 is pressed by the water head pressure and its own weight applied to the reactor well gate 200, the opening 100a of the reactor pressure vessel 100 is sealed (covered). In addition, since the protrusions 210a are provided on the partition wall 202 of the reactor well gate 200, the elastic packing 210 is not excessively compressed and may not be damaged.

  Next, as illustrated in FIGS. 6D to 6F, the nut 230 is tightened from the upper end of the mounting bolt 150 by a predetermined amount using the T-type nut tightening jig 224 from above the fuel changer 142. This operation is performed while the scale of the indicator 226 is read by the underwater camera 232 lowered from the refueling machine 142 and the amount of compression of the elastic packing 210 is monitored.

  In the present embodiment, the diameter of the upper end of the mounting bolt 150 is the same as that of the shroud head bolt 128. Conventionally, there is a track record of tightening a nut by remote control of the shroud head bolt 128, and the above-described nut 230 can be tightened without any problem. On the other hand, when a nut is fastened to the flange bolt 104a by remote operation, the diameter of the nut becomes large, so that the fastening work becomes extremely difficult.

  FIG. 7 is a diagram illustrating another example of a reactor well gate according to this embodiment. FIG. 7A is a diagram illustrating the appearance of the surface side of the reactor well gate 200a, and FIG. 7B is a diagram illustrating the appearance of the back side of the reactor well gate 200a.

  As illustrated in FIG. 7A, in the reactor well gate 200a, the surface side of the partition wall 202 is formed in a dome shape so as to have resistance against water pressure. Further, as illustrated in FIG. 7B, a protective member 238 is provided near the outer edge on the back side of the partition wall 202 to prevent damage when contacting the flange portion 104. As the protection member 238, hard rubber or the like can be used.

  FIG. 8 is a diagram illustrating an airtight seal portion of the reactor well gate. As illustrated in FIG. 8, the reactor well gate 200a is provided with an air packing 234 and an air packing expansion part 236 (an air supply nozzle 236a and an air supply hose 236b) as an airtight seal part.

  As illustrated in FIG. 8A, an air packing storage groove 202 b for storing the air packing 234 and a nozzle insertion nozzle 208 c are formed in the partition wall 202 in advance. As illustrated in FIG. 8B, when constructing the reactor well gate 200a, the air packing 234 is housed in the air packing housing groove 202b, and the air supply nozzle 236a connected to the air packing 234 is a nozzle insertion tube base. It is attached so as to pass through 208c. In addition, the protective member 238 is attached so as to sandwich the air packing 234.

  As illustrated in FIG. 8C, the air supply hose 236 b is attached to the air supply nozzle 236 a before placing the reactor well gate 200 a on the flange portion 104. The air supply hose 236b is connected to a device (not shown) that supplies air.

  As illustrated in FIG. 8D, when the reactor well gate 200a is placed on the flange portion 104, air is supplied from the air supply hose 236b to the air packing 234 via the air supply nozzle 236a. As a result, the air packing 234 exhibits elasticity and closes the opening 100a by closing the gap with the flange portion 104 (contact surface). It is more preferable that an instrument (valve) for preventing the backflow of air is attached to the air supply hose 236b or the like.

  In addition, the floating of the reactor well gate 200 a due to the air supply to the air packing 234 is prevented because the nut 230 is fastened to the mounting bolt 150.

[Reactor inspection method]
FIG. 9 is a flowchart illustrating a nuclear reactor inspection method according to this embodiment. Hereinafter, a nuclear reactor inspection method using the reactor well gate 200 (the same applies to the reactor well gate 200a) will be described in detail with reference to FIGS. .

  When carrying out the periodic inspection of the nuclear power plant, the operation of the nuclear reactor is first stopped as step 300. In step 302, the RPV head 106 is removed and the reactor pressure vessel 100 is opened.

  In step 304, a part of the plurality of flange bolts 104a standing on the flange portion 104 is removed. In step 306, the guide pin 148 and the mounting bolt 150 are attached to the screw hole 104b from which the flange bolt 104a has been removed.

  In step 308, the duct 220 (air supply hose 236b), the monitoring camera 222, and the like are attached to the reactor well gate 200.

  FIG. 10 is a schematic view illustrating a reactor pressure vessel, a reactor well, a spent fuel pool and a dryer separator pool after fuel removal operation, and each system, where (a) is a side view and (b) is ( It is A arrow view of a). In step 310, a fuel removal operation for the reactor pressure vessel 100 is performed.

  Specifically, 1) about 2.5 m of water is filled in the reactor well 134 and the dryer separator pool 138, 2) the steam dryer 132 is removed, 3) the shroud head bolt 128 is loosened, and 4) the shroud head 126 is removed. The fuel removal operation is carried out in the procedure of 5) filling the reactor well 134 and the dryer separator pool 138 to a predetermined water level, 6) removing the steam separator 130, and 7) taking out the fuel assembly 102. In addition to refueling work, other work (such as in-furnace inspection work) for periodic inspections shall be performed.

  FIG. 11 is a diagram illustrating a state in which a reactor well gate is attached to the flange portion of the reactor pressure vessel, where (a) is a side view and (b) is a view as viewed from the arrow B in (a). In step 312, the reactor well gate 200 is suspended (placed) on the flange portion 104 of the reactor pressure vessel 100 using the overhead crane 146. In step 314, the nut 230 is tightened by a predetermined amount from the upper end of the mounting bolt 150 by remote control from the fuel exchanger 142. As shown in FIG. 11 (b), the air intake / exhaust system 228 is placed on the operation floor 140.

  FIG. 12 is a diagram illustrating a state in which water outside the shroud of the reactor pressure vessel has been drained, in which (a) is a side view and (b) is a view taken in the direction of arrow C in (a). In step 316, water outside the shroud 114 of the reactor pressure vessel 100 is transferred from the N1 nozzle 118 of the reactor recirculation system 250 (PLR system) to the suppression pool 260 via the residual heat removal system 252 (RHR system). And begin to unplug.

  The reactor recirculation system 250 is a forced circulation path for taking out water from the reactor pressure vessel 100 and increasing the pressure by the PLR pump 250a and returning it to the reactor. The reactor power is adjusted by changing the rotation speed of the PLR pump 250a. The reactor recirculation system 250 is formed in pairs with the reactor pressure vessel 100 interposed therebetween.

  Residual heat removal system 252 is used for shutdown cooling to remove decay heat after reactor shutdown, removal of decay heat and residual heat during reactor isolation (condensate / water supply shutdown state), and loss of reactor coolant. This system performs core cooling and the like. Specifically, the residual heat removal system 252 is configured by two systems that are substantially mutually related, that is, an RHR (A) system and an RHR (B) system, and each includes an RHR pump 252a and an RHR heat exchanger 252b.

  The suppression pool 260 is a storage tank for condensing the generated steam and reducing the pressure in order to suppress an increase in internal pressure in the reactor containment vessel at the time of an accident.

As illustrated in FIGS. 12A and 12B, water outside the shroud 114 flows from the N1 nozzle 118 to the suppression pool 260 (shown by a thick line in the drawing), or from the N1 nozzle 118. A second drainage path (shown by a dotted line in the figure) that reaches the suppression pool 260 through the RHR pump 252a, or both, can be used to drain the suppression pool 260. Without requiring a power source such as a pump in such a drainage (without taking into account the net positive suction head (NPSH), etc. of the pump), it can also weep about Hourly 1300 m ³ by the water level difference between the suppression pool 260 (drop) It is. In the second drainage path, the RHR pump 252a is passed over, but there is no need to operate the RHR pump 252a, and this is idled and drained into the suppression pool 260.

  In step 316, a small amount of water is drained first, and it is preferable to check with the monitoring camera 222 whether water leaks from the hermetic seal portion.

  In step 318, air is sent through the duct 220 following the drop in the water level in the reactor pressure vessel 100. As shown in FIGS. 11B and 12B, the duct 220 is connected to an air intake / exhaust system 228 including an intake port 228a with a gravity damper (non-return damper) and an exhaust treatment device 228b. And air is sent into the duct 220 by the air inlet 228a with a gravity damper. Even if the air in the duct 220 flows backward from the air inlet 228a with the gravity damper, it is not released into the reactor building.

  In order to prevent the duct 220 from irregularly moving due to the reaction force of the air flowing in from the air inlet 228a with the gravity damper, the diameter of the duct 220 is set to keep the internal flow velocity down to about 2 m / s. It is preferable to set to. When this flow velocity cannot be realized by a single duct 220, a plurality of ducts 220 may be installed as in this embodiment. Even if the length of the duct 220 is not the shortest connecting the reactor well gate 200 and the air intake / exhaust system 228, even if the duct 220 moves irregularly due to the reaction force of the inflowing air, excessive stress is applied. It is good to have a slack so as not to get it.

  As step 320, before the drainage outside the shroud 114 is completed, a closing plate or the like is attached to the air inlet 228a with the gravity damper to stop the inflow of air, and the exhaust treatment device 228b is operated to maintain the negative pressure. The exhaust treatment device 228 b includes a demister that absorbs moisture in the sucked air and a filter that removes dust, and processes the air sucked from the reactor pressure vessel 100.

  As step 322, the pipe up to the submergence valve 254 connected to the outside of the shroud 114, inspection of the submergence valve 254, etc. are started. Such pipes are cut, welded after repair or modification, and returned to their original state. The submerged valve 254 is disassembled and inspected.

  In addition, it is possible to start inspection of the reactor recirculation system 250 which requires the most time by draining water outside the shroud 114.

  FIG. 13 is a diagram illustrating a state in which water in the shroud of the reactor pressure vessel has been drained, in which (a) is a side view and (b) is a view taken along arrow D in (a). In step 324, the water in the shroud 114 is fed from the front side of the reactor coolant purification system pump (hereinafter referred to as CUW pump 256a) via the bottom drain pipe 100b of the reactor pressure vessel 100 to the low-conductivity waste liquid treatment system. Unplug to (LCW system).

  The reactor coolant purification system 256 (CUW system) is a system for removing impurities contained in water (reactor water) in the reactor and maintaining water quality. The reactor coolant purification system 256 also plays a role of controlling the water level of the reactor by discharging surplus water during start-up, shutdown, and inspection of the reactor. In the present embodiment, the water in the reactor pressure vessel 100 is discharged to the low-conductivity waste liquid treatment system without using the CUW pump 256a.

  The low-conductivity waste liquid treatment system is a system that treats clean water with waste water and leaked water from equipment in the reactor building, waste liquid from the sampling line, and the like. The water discharged to the low-conductivity waste liquid treatment system is finally sent to a rad waist (not shown) for processing.

  As illustrated in FIGS. 13A and 13B, all the water in the reactor pressure vessel 100 is completely drained as described above. As a result, as step 326, the pipe up to the submersible valve 254 connected to the shroud 114 such as the bottom drain pipe 100b and the inspection of the submerged valve 254 are started.

  FIG. 14 is a diagram illustrating a state in which water has been refilled in the reactor pressure vessel, where (a) is a side view and (b) is a view as viewed from arrow E in (a). In step 328, the reactor pressure vessel 108 is refilled with water for fuel loading. In the water filling, the water filling condition may be monitored with a water level gauge attached to the equipment mounting nozzle 208b, and the water filling may be terminated when the bottom surface of the reactor well gate 200 is reached.

  In step 330, the nut 230 fastened to the mounting bolt 150 by remote operation is removed from the refueling machine 142 or the like, and the reactor well gate 200 is removed by the overhead crane 146 or the like. That is, the covering of the opening 100a by the reactor well gate 200 is released. At the end of the water filling in step 328, the air inside the reactor well gate 200 is replaced by the air intake / exhaust system 228, so that polluted air is released into the reactor building even if the coating by the reactor well gate 200 is removed. There is no risk.

  As described above, with the configuration described above, it is possible to complete the piping up to the submergence valve 254, the inspection of the submergence valve 254, and the like more easily and quickly. And the total time required for water filling after completion of inspection and the like and opening of the opening 100a of the reactor pressure vessel 100 can be greatly shortened.

  In the configuration described above, the fuel pool cooling and purification system 258 (FPC system) is not affected. The fuel pool cooling and purification system 258 has an FPC pump 258a, a filtration desalination device 258b (FPC filter demi), and an FPC heat exchanger 258c, purifies and cools water sent from the skimmer surge tank 136a, and is used again. This is a system that returns the fuel pool 136. Therefore, while maintaining the cooling of the spent fuel pool 136, the piping up to the submergence valve 254, the inspection of the submergence valve 254, and the like can be performed.

[Effects of the above form]
FIG. 15 and FIG. 16 are diagrams for explaining a conventional method for inspecting piping and submersion valves up to a submergence valve as a comparative example. Hereinafter, in contrast to the comparative example of FIG. 15 and FIG. 16, the effect produced by the above-described embodiment will be described. In the following description, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 15A illustrates the reactor pressure vessel 100, the reactor well 134, the spent fuel pool 136 and the dryer separator pool 138, and each system after the fuel removal operation. As illustrated in FIG. 15B, conventionally, it has been necessary to first insert the SFP gate 12 between the spent fuel pool 136 and the reactor well 134 using the overhead crane 146. Similarly, it was necessary to insert the DSP gate 14 between the dryer separator pool 138 and the reactor well 134. As described above, in the present embodiment, it is not necessary to attach or remove the SFP gate 12 or the DSP gate 14, and it is not necessary to perform such work.

  As illustrated in FIG. 15 (c), it is necessary to draw the water in the reactor well 134 next to the suppression pool 260 using the fuel pool coolant purification system 258 until the water is about 50 cm lower than the flange portion 104. there were. At this time, it was necessary to decontaminate the wall surface, bottom surface, and bulkhead portion of the reactor well 134 in order to simultaneously prevent the radioactive material from scattering and preventing the spread of contamination.

  On the other hand, in the present embodiment, it is not necessary to drain the reactor well 134. For this reason, the total amount of drainage is reduced, and the time required for draining (water filling) can be shortened. In addition, the reduction of the total drainage amount leads to a reduction in the burden on the radioactive liquid waste treatment system. In addition, since the water stretched in the reactor well 134 shields the radiation from the reactor pressure vessel 100, the exposure dose on the operation floor 140 can be kept extremely low. Of course, it was not necessary to perform the above decontamination work.

  As illustrated in FIG. 15D, it was necessary to attach the RPV head 106 in order to shield the radiation from the reactor pressure vessel 100 at the time of draining. In this operation, it is necessary to cure the bulkhead part in advance, and after attaching the RPV head 106 to the flange part 104, it is necessary to cure the edge part of the flange part 104 and the RPV head 106 with a vinyl sheet or the like. Further, it is necessary to connect the exhaust duct 18 for exhausting air to the RPV head 106 and stack the canal plug 16 on the canal.

  On the other hand, in this embodiment, it is not necessary to perform such work at all as described above. In other words, in the present embodiment, piping up to the submergence valve 254, inspection of the submergence valve 254, and the like can be performed with less work man-hours.

  As illustrated in FIG. 16A, the reactor well cover 20 needs to be attached to the reactor well 134 in order to reduce radiation exposure in the next operation on the operation floor 140. In addition, an exhaust treatment device 22 that is connected to the exhaust duct 18 and maintains the inside of the reactor pressure vessel 100 at a negative pressure needs to be installed on the reactor well cover 20.

  On the other hand, in this embodiment, since the water stretched on the reactor well gate 200 and the reactor well 134 shields the radiation from the reactor pressure vessel 100, it is not necessary to provide such additional shielding means.

  As illustrated in FIG. 16B, the water from the bottom of the flange portion 104 of the reactor pressure vessel 100 to the NPW of the CUW pump 256a that satisfies the required NPSH (ie, in the vicinity of the jet pump nozzle 116) is reduced to a low-conductivity waste liquid. It was necessary to remove it to the processing system. Further, as illustrated in FIG. 16C, it was necessary to next drain water from the jet pump nozzle 116 to the N1 nozzle 118 of the reactor pressure vessel 100 into the low-conductivity waste liquid treatment system. At this time, it was necessary to operate the exhaust treatment device 22 in order to maintain the negative pressure. Further, as illustrated in FIG. 16D, the water in the shroud 114 needs to be extracted from the bottom drain pipe 100b to the low-conductivity waste liquid treatment system.

  On the other hand, in this embodiment, as described above, water in the reactor pressure vessel 100 can be drained all at once. Therefore, it is not necessary to follow such a procedure, and the water in the reactor pressure vessel 100 can be drained in a short time. Of course, it is not necessary to consider the effective suction head (NPSH) of the pump.

  Of course, according to the conventional method, after the piping up to the submergence valve 254 and the inspection of the submergence valve 254 are completed, the reactor pressure vessel 100 must be refilled with water and the reactor well 134 must be refilled with water. Further, the exhaust treatment device 22, the reactor well cover 20, the curing portion formed during the draining operation, the canal plug 16 and the like must be removed. On the other hand, in the configuration according to the present embodiment, such various operations can be omitted, the burden on the operator can be reduced, and the time required for the operation can be greatly shortened.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  INDUSTRIAL APPLICABILITY The present invention can be used as a drainage facility for reactor pool water, and a method for draining a reactor well and a dryer separator pool.

DESCRIPTION OF SYMBOLS 100 ... Reactor pressure vessel, 100a ... Opening part, 100b ... Bottom drain piping, 102 ... Fuel assembly, 104 ... Flange part, 104a ... Flange bolt, 104b ... Screw hole, 106 ... RPV head, 108 ... Control rod drive mechanism 110 ... Control rod guide tube, 114 ... Shroud, 116 ... Jet pump nozzle, 118 ... N1 nozzle, 120 ... Core sparger, 122 ... Feed water sparger, 124 ... Upper grid plate, 126 ... Shroud head, 128 ... Shroud head bolt , 130 ... Steam separator, 132 ... Steam dryer, 133 ... Main steam pipe, 134 ... Reactor well, 136 ... Spent fuel pool, 136a ... Skimmer surge tank, 138 ... Dryer separator pool, 140 ... Operation floor, 142 ... Fuel changer, 144 ... Rail, 46 ... overhead crane, 148 ... guide pin, 150 ... mounting bolt, 152 ... area, 200 ... reactor well gate, 200a ... reactor well gate, 202 ... partition wall, 202a ... rib, 202b ... air packing storage groove, 204 ... Suspension piece, 206a ... Indicator hole, 206b ... Flange bolt insertion hole, 206c ... Guide pin insertion hole, 206d ... Mounting bolt insertion hole, 208a ... Duct nozzle, 208b ... Equipment mounting nozzle, 208c ... Nozzle insertion nozzle, 210 ... Elastic packing, 210a ... Projection, 220 ... Duct, 222 ... Monitoring camera, 224 ... T-type nut tightening jig, 226 ... Indicator, 228 ... Air intake / exhaust system, 228a ... Intake port, 228b ... Exhaust treatment device, 230 ... Nut, 232 ... Underwater camera, 234 ... Air packing, 236 ... Ar packing expansion part, 236a ... air supply nozzle, 236b ... air supply hose, 238 ... protective member, 250 ... reactor recirculation system, 250a ... PLR pump, 252 ... residual heat removal system, 252a ... RHR pump, 252b ... RHR Heat exchanger, 254 ... Submergence valve, 256 ... Reactor coolant purification system, 256a ... Pump, 258 ... Fuel pool cooling / purification system, 258a ... FPC pump, 258b ... Filtration demineralizer, 258c ... FPC heat exchanger, 260 ... Suppression pool, 12 ... SFP gate, 14 ... DSP gate, 16 ... Canal plug, 18 ... Exhaust duct, 20 ... Reactor well cover, 22 ... Exhaust treatment device

Claims (10)

A substantially disc-shaped partition wall in which a plurality of mounting holes are formed in the vicinity of the outer edge;
An airtight seal portion provided inside the plurality of mounting holes of the partition wall and closing a gap with the contact surface;
A duct connected to the bulkhead;
An air intake / exhaust system for performing air intake / exhaust through the duct;
With
A reactor well characterized in that the reactor well is attached to a flange portion of a reactor pressure vessel through the plurality of attachment holes in a state where water is stretched in the reactor well, and the opening of the reactor pressure vessel is sealed. Gate. A sharp guide pin replaced with a part of a plurality of flange bolts for mounting an RPV head standing on the flange portion, and a mounting bolt having a small diameter on the upper side;
The reactor well gate, as the plurality of mounting holes,
A flange bolt insertion hole for inserting the flange bolt;
A guide pin insertion hole for inserting the guide pin;
A mounting bolt insertion hole for inserting the mounting bolt;
The reactor well gate according to claim 1, comprising: The mounting bolt is
The diameter of the lower end is substantially the same as the flange bolt,
The reactor pressure vessel sealing method according to claim 2, wherein the diameter of the upper end is substantially the same as or less than the shroud head bolt of the atomic pressure vessel. The hermetic seal portion is an elastic packing,
2. The reactor well gate according to claim 1, wherein the partition wall has a protruding portion protruding downward in contact with the flange portion in the vicinity of an outer edge thereof.   2. The reactor well gate according to claim 1, wherein the hermetic seal portion is an air packing and an air packing expansion portion that supplies air to the air packing. 3.   The reactor well gate according to claim 5, wherein the partition wall has a protective member for preventing damage to the flange portion when contacting the flange portion in the vicinity of the outer edge thereof. A first step of sealing the opening of the reactor pressure vessel with water filled in the reactor well;
A second step of draining water from the reactor pressure vessel;
A third step of inspecting, repairing or remodeling the submergence valve and piping to the submergence valve connected to the reactor pressure vessel;
After the third step, a fourth step of filling the reactor pressure vessel again with water;
A fifth step of uncovering the opening;
A method for inspecting a nuclear reactor, comprising: In the first step,
Replacing a part of the plurality of flange bolts for mounting the RPV head standing on the flange portion of the reactor pressure vessel with a sharp guide pin and a mounting bolt having a small diameter on the upper side,
A reactor well gate having a substantially disc-shaped partition wall through which the flange bolt, the guide pin and the mounting bolt are inserted is placed on the flange portion,
The reactor inspection method according to claim 7, wherein a nut is fastened to the mounting bolt, and the opening is sealed with the reactor well gate. The nuclear reactor well gate includes a duct and an air intake / exhaust system that performs intake / exhaust of air through the duct,
In the second step, as the water level of the reactor pressure vessel is lowered, the air intake / exhaust system sends air into the reactor pressure vessel through the duct,
Prior to completing draining of the reactor pressure vessel outside the shroud, the air intake and exhaust system draws air through the duct to maintain a negative pressure inside the reactor pressure vessel,
In the fourth step,
The reactor inspection method according to claim 8, wherein the air intake / exhaust system extracts air inside the reactor pressure vessel through the duct as the water level of the reactor pressure vessel rises. In the second step,
Water outside the shroud of the reactor pressure vessel is drawn from a nozzle connected to the lower part of the reactor pressure vessel to a suppression pool via a reactor recirculation system and a residual heat removal system,
The water in the shroud is drained from the front side of the reactor coolant purification system pump to the low-conductivity waste liquid treatment system via the bottom drain pipe of the reactor pressure vessel. Reactor inspection method.

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