JP6469972B2 - Local output region neutron detector assembly and local output region neutron detector assembly assembly method - Google Patents

Description

  Embodiments of the present invention relate to a local power region neutron detector assembly and its assembly method.

  In general, a boiling water reactor measures a neutron flux or a gamma ray flux of a core, and a plurality of neutron detectors inserted in gaps between a plurality of fuel assemblies in the core through a reactor pressure vessel, Local power range neutron detector assembly (hereinafter referred to as LPRM) incorporating a conduit (hereinafter referred to as a calibration conduit) of a mobile in-core instrument that performs calibration of the neutron detector. Is installed.

  FIG. 6 is a vertical partial sectional view showing a configuration of a part of a conventional local output region neutron detector assembly. In this LPRM, a calibration conduit 13 and a signal output cable 12 connected to the neutron detector 11 are hermetically welded at a seal portion 17 below the LPRM. Further, the calibration conduit 13 and the signal output cable 12 connected to the neutron detector 11 are covered with a housing pipe 15 welded to the seal portion 17 and a cover pipe 8 welded to the housing pipe 15. Yes. Since the cover pipe 8 is inserted into the gap of the fuel assembly, the outer diameter is restricted, and the inner diameter is also restricted in order to secure a cooling water flow rate for reducing the temperature rise effect due to the gamma ray heating of the neutron detector 11. . On the other hand, since the housing pipe 15 is not restricted as compared with the cover pipe 8, the wall thickness thereof is thicker than that of the cover pipe 8 (Patent Document 1).

  As the welding inspection of the welded portion A between the cover pipe 8 and the housing pipe 15, a liquid penetration test (PT) on the outer surface of the welded portion can be performed as a nondestructive test. However, the radiation transmission test (RT) for the inner surface of the welded portion cannot be appropriately performed because the calibration conduit 13 and the signal output cable 12 are built inside the welded portion A.

  In addition, when the calibration pipe 13 and the signal output cable 12 are attached after the RT is performed without welding the calibration pipe 13 and the signal output cable 12 after welding the cover pipe 8 and the housing pipe 15, These lengths after installation of the conduit 13 and the signal output cable 12 cannot be measured, and the height position in the core of the neutron detector 11 at the time of measurement by LPRM becomes unclear, so that accurate measurement cannot be performed. .

JP 2001-221886 A

  The cover pipe 8 vibrates in the radial direction at a gap in the fuel assembly during an earthquake. Since the bending moment increases toward the lower side of the cover pipe 8, the stress is most severe at the welded portion A with the housing pipe 15 at the lower end of the cover pipe 8.

  Here, in the welded portion, it is necessary to allow for joint efficiency for strength evaluation. The joint efficiency can be 1.0, i.e., the same value as that of the base material when RT is carried out for all locations. When the rate of performing RT decreases, the usable welding efficiency becomes a low value.

  For the welded part of the cover pipe 8 and the housing pipe 15 pipe, since RT cannot be performed as a nondestructive test, a low value must be used as the joint efficiency of the welded part, and sufficient strength margin cannot be secured. was there.

  Therefore, an embodiment of the present invention has been made to solve the above-described problem, and an object thereof is to secure a margin in structural strength in LPRM.

In order to achieve the above-described object, the present embodiment is directed to a local power region neutron detector that measures a local power region neutron flux of a core housed in a reactor pressure vessel during power operation of a nuclear reactor in a local power region neutron detector assembly. In the detector assembly, in the reactor pressure vessel, a tubular cover pipe that surrounds the radially outer side of the neutron detector and the neutron detection housing and has an upper end and a lower end open and extends vertically, and an upper end and a lower end A housing pipe that is opened and extends in the vertical direction, the upper end of which is welded to the cover pipe and extends through the lower part of the reactor pressure vessel, and the neutron detection container extends through the lower end. A housing-like pipe, and a disc-shaped seal portion that is provided between the upper end and the lower end of the housing pipe and through which the neutron detection storage product penetrates in an airtight manner, Serial cover pipe has an enlarged portion whose outer diameter is enlarged from the upper end until the lower end in a portion and lower than the lower end of the core of the reactor core, of the lower end of the enlarged portion of the connection portion between the housing pipe The area where the cross section overlaps the cross section of the upper end of the housing pipe is larger than the cross sectional area of the portion of the cover pipe in the core.

Further, in the present embodiment, a local power region neutron detector assembly that measures a local neutron flux of a core housed in a reactor pressure vessel during power operation of the reactor, the neutron detection is performed in the reactor pressure vessel. A tubular cover pipe that surrounds the outer side in the radial direction of the detector and the neutron detection container and has an upper end and a lower end that are open and extend in the vertical direction; A housing pipe having an upper end and a lower end opened and extending in a vertical direction, the upper end being welded to the lower end of the adapter and extending through a lower portion of the reactor pressure vessel, and the neutron detection container is A tubular housing pipe that extends through the lower end, and a disc that is provided between the upper end and the lower end of the housing pipe and through which the neutron detection storage product penetrates hermetically The adapter has an enlarged portion between the upper end and the lower end, and an area where the cross section of the lower end of the adapter and the cross section of the upper end of the housing pipe overlap each other at the connection portion with the housing pipe Is larger than the cross-sectional area of the upper end of the enlarged portion.

Further, according to the present embodiment, in the method for assembling the local output region neutron detector assembly, a tubular cover pipe whose upper end and lower end are opened and extended in the vertical direction in the reactor pressure vessel, and upper and lower ends are opened. A tubular housing pipe extending in the vertical direction and having an upper end welded to the cover pipe and extending through the lower part of the reactor pressure vessel, a neutron detector disposed inside the cover pipe, and an inner side of the cover pipe A neutron detection storage article extending through the lower end of the housing pipe from the top, and a disc-shaped seal portion provided between the upper end and the lower end of the housing pipe and through which the neutron detection storage article passes airtightly , a method of assembling a local power range neutron detector assembly comprising, the neutron detection accommodating articles is passed through the seal portion, for the neutron detection And the seal portion bonding step of bonding the delivery to the sealing portion and airtightly, after the seal portion bonding step, the neutron detection storage products inserting the sealing portion penetrating into the housing pipe, wherein said housing pipe seal and the seal portion outer bonding step of bonding the part hermetically, after the seal portion outer bonding step, the cover pipe having said housing pipe, the enlarged portion having an outer diameter is enlarged from the upper end to the lower up to the lower end An overall joining step of welding the lower end of the enlarged portion or the lower end of the enlarged portion.

Further, in this embodiment, in the method of assembling the local output region neutron detector assembly , the upper and lower ends are opened in the reactor pressure vessel and the tubular cover pipe extending in the vertical direction is opened, and the upper and lower ends are opened. An upper end is welded to the lower end of the cover pipe, an adapter having an enlarged portion whose outer diameter expands from the upper end to the lower end, the upper end and the lower end are opened and extend in the vertical direction, and the upper end is welded to the adapter. A tubular housing pipe extending through the lower part of the reactor pressure vessel, a neutron detector disposed inside the cover pipe, and a neutron detection extending from the inside of the cover pipe through the lower end of the housing pipe And a disc-shaped seal provided between the upper end and the lower end of the housing pipe and through which the neutron detection storage product penetrates hermetically. , A method of assembling a local power range neutron detector assembly comprising said neutron detecting accommodating articles is passed through the seal portion, the seal portion and the seal portion bonded to hermetically bonded to said neutron detector housing parts a step, after the seal portion bonding step, inserting the said seal portion for neutron detection storage products penetrating in the housing pipe, and the seal portion outer bonding step of bonding the housing pipe and the sealing part in an airtight , welded to the upper end of the said cover pipe adapter comprises an adapter welded performing a radiological examination, after the adapter welding step, and a total bonding step for welding the lower end of the said housing pipe adapter It is characterized by that.

  According to the embodiment of the present invention, it is possible to secure a margin on the structural strength of the LPRM.

It is a longitudinal cross-sectional view which shows the state which attached the local power range neutron detector assembly which concerns on 1st Embodiment to the nuclear reactor. It is a vertical fragmentary sectional view which shows the structure of a part of local output region neutron detector assembly which concerns on 1st Embodiment. It is a flowchart which shows the procedure of the assembly method of the local output area | region neutron detector assembly which concerns on 1st Embodiment. It is a vertical fragmentary sectional view which shows the structure of a part of local output region neutron detector assembly which concerns on 2nd Embodiment. It is a flowchart which shows the procedure of the assembly method of the local output region neutron detector assembly which concerns on 2nd Embodiment. It is a vertical fragmentary sectional view which shows the structure of a part of conventional local output region neutron detector assembly.

  Hereinafter, a local output region neutron detector assembly and a method for assembling a local output region neutron detector assembly according to an embodiment of the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is a longitudinal sectional view showing a state in which the local power region neutron detector assembly according to the first embodiment is attached to a nuclear reactor. In FIG. 1, illustration of a core shroud of a boiling water reactor (BWR), a jet pump for recirculation of a reactor coolant, a steam-water separator at the top of the core, and the like are omitted.

  A reactor core 2 is accommodated in a reactor pressure vessel (RPV) 1. A core support plate 3 extending in the horizontal direction is provided below the core 2. Further, an upper lattice plate 4 extending in the horizontal direction is provided above the core 2.

  At the bottom of the RPV 1, an RPV pedestal portion 5 and a lower closing portion 7 are provided so that the local output region neutron detector assembly (LPRM) 10 penetrates the RPV 1. The RPV nozzle section 5 is an RPV 1 nozzle base and its extension. The RPV tube base part 5 and the lower closing part 7 and the outer part of the LPRM 10 separate the atmosphere inside the RPV 1 from the atmosphere outside the RPV 1. Inside the RPV 1, a guide tube 6 extending in the vertical direction for guiding and protecting the LPRM 10 is provided from the bottom of the RPV 1 to the lower surface of the core support plate 3.

  The LPRM 10 includes a housing pipe 15 and a cover pipe 16 that are connected to each other up and down, and a neutron detector 11 (FIG. 2) and a neutron detection container housed in the cover pipe 16. Here, the storage product for neutron detection includes a signal output cable 12 (FIG. 2) and a calibration conduit 13 (FIG. 2).

  The cover pipe 16 has a tubular shape extending vertically, and an upper end and a lower end are opened. The LPRM 10 is provided in the core 2 between fuel assemblies (not shown) arranged at the position of the core 2. For this reason, the diameter of the cover pipe 16 which is a part in the core 2 of the LPRM 10 is limited so as not to exceed a predetermined dimension in terms of arrangement.

  An enlarged portion 16 a is formed below the portion corresponding to the position of the lower end height of the core 2 of the cover pipe 16. In addition, an extendable portion 16 b is attached to the upper end of the cover pipe 16. The expansion / contraction part 16b incorporates, for example, a coil spring that expands and contracts up and down, and is formed to be expandable and contractable up and down. The housing pipe 15 has a tubular shape whose upper and lower ends are open. The housing pipe 15 is welded to the lower end of the cover pipe 16.

  In a state where the LPRM 10 is provided in the RPV 1, the LPRM 10 is installed in the vertical direction inside the RPV 1 as a whole. The upper end of the LPRM 10, that is, the upper end of the expansion / contraction part 16 b is fitted in a recess formed on the lower surface of the upper grid plate 4. The LPRM 10, specifically, the housing pipe 15 passes through the core support plate 3, and the lower portion, that is, the lower part of the housing pipe 15 passes through the bottom of the RPV 1.

  The housing pipe 15 is accommodated in the guide tube 6 until it passes through the core support plate 3 and reaches the bottom of the RPV 1. The housing pipe 15 extends further downward and penetrates the bottom of the RPV 1. After passing through the bottom of the RPV 1, the housing pipe 15 extends through the RPV tube base part 5 and extends through the lower closing part 7 into the external air atmosphere.

  FIG. 2 is a vertical partial cross-sectional view showing a configuration of a part of the local output region neutron detector assembly 10. The RPV 1, the RPV pipe pedestal portion 5, and the lower closing portion 7 are surrounding structures that are not joined to the LPRM 10, and are indicated by broken lines. In FIG. 2, the expansion / contraction part 16 b attached to the upper end of the cover pipe 16 and a part of the lower closing part 7 are omitted.

  As described above, the enlarged portion 16a is formed in the lower portion of the cover pipe 16. In the enlarged portion 16 a, the outer diameter gradually increases from the diameter of the portion of the cover pipe 16 that passes through the core 2 (FIG. 1) toward the lower side and becomes equal to the outer diameter of the housing pipe 15. It extends while maintaining the diameter. Therefore, in the welded portion B between the cover pipe 16 and the housing pipe 15, the cross section of the cover pipe 16 and the cross section of the housing pipe 15 facing each other have the same outer diameter. It is not always necessary that the outer diameters are the same. If the area where the cross section of the cover pipe 16 and the cross section of the housing pipe 15 that are opposite to each other overlap is sufficient for strength evaluation, the outer diameter and the inner diameter of both are mutually equal. Big or small

  The cover pipe 16 accommodates four neutron detectors 11, a signal output cable 12 connected to each neutron detector 11, and a calibration conduit 13 in the RPV 1. The neutron detectors 11 are vertically arranged at intervals. The signal output cable 12 extends downward from the connection point with the neutron detector 11. The calibration conduit 13 extends downward from the height of the uppermost neutron detector 11.

  That is, the signal output cable 12 and the calibration conduit 13 extend downward in parallel with each other, and extend further downward in the housing pipe 15 after passing through the lower end of the cover pipe 16. The signal output cable 12 and the calibration conduit 13 extend until the housing pipe 15 passes through the lower closing portion 7 and reaches the air atmosphere. The end of the signal output cable 12 is connected to a connector (not shown) provided in an air atmosphere. That is, the connector can be connected to and disconnected from an external cable (not shown).

  A plurality of spacers 14 are provided in the cover pipe 16 so as to be spaced apart from each other in the vertical direction. The signal output cable 12 and the calibration conduit 13 are caused to vibrate in the horizontal direction so that the inner walls of the cover pipe 16 and the housing pipe 15 are provided. The signal output cable 12 and the calibration conduit 13 are supported in order to prevent the occurrence of problems due to contact with each other or with each other.

  A seal portion 17 is provided in the housing pipe 15. The seal portion 17 has a disk shape and is provided horizontally in the housing pipe 15. The outer periphery of the seal portion 17 is airtightly joined to the inner surface of the housing pipe 15. Further, four signal output cables 12 and a calibration conduit 13 penetrate vertically through the seal portion 17. The portions of the four signal output cables 12 and the calibration conduit 13 that pass through the seal portion 17 are airtightly joined. Therefore, the seal part 17 is a partition that hermetically isolates the upper and lower sides. That is, on the inner side of the housing pipe 15, the upper reactor coolant and the lower air are isolated in the seal portion 17.

  The calibration conduit 13 is a tube that is closed at the top and is not open in the RPV 1. In order to calibrate the output signal of the neutron detector 11 of the LPRM 10 during the power operation of the nuclear reactor, a traveling neutron detector (TIP) (not shown) neutrons at the same height as each neutron detector 11 of the LPRM 10. Detection is performed and the neutron detector 11 of the LPRM 10 is calibrated. The calibration conduit 13 forms a passage through which the TIP moves up and down. Therefore, the lower end portion of the calibration conduit 13 is connected to a driving device (not shown) of the TIP.

  The outer surface of the housing pipe 15 has an outer shape that is different between an upper portion and a lower portion, and a tapered portion 15a is formed so that the outer diameter decreases from the top to the bottom in the circumferential direction at a middle height portion. Further, a taper portion 7a is formed in the lower closing portion 7 so as to cut out in a downward conical shape so as to correspond to the taper portion 15a. The contact surface between the taper portion 15a and the taper portion 7a is formed airtight, and serves as a boundary that separates the atmosphere inside the RPV1 and the atmosphere outside the RPV1 on the outside of the housing pipe 15.

  A flange portion 5 a is formed at the lower end of the RPV tube base portion 5. The upper surface of the lower closing part 7 is formed so as to face the flange part 5a of the RPV nozzle base part 5 and to be in close contact with each other by a bolt (not shown). Although not shown in FIG. 2, the space between the through hole formed in the lower closing portion 7 and the outer surface of the housing pipe 15 is hermetically formed. For this reason, this portion is also a boundary that separates the atmosphere inside the RPV 1 and the atmosphere outside the RPV 1, as in the contact surface between the tapered portion 15 a and the tapered portion 7 a.

  By tightening the bolt, the upper surface of the lower closing portion 7 and the flange portion 5a are brought into close contact with each other, and the tapered portion 15a of the housing pipe 15 and the tapered portion 7a of the lower closing portion 7 are brought into close contact with each other. At this time, the expansion and contraction portion 16b at the upper end of the LPRM 10 expands and contracts in the vertical direction, so that an excessive compressive force is not applied to the LPRM 10.

  FIG. 3 is a flowchart showing the procedure of the method for assembling the local output region neutron detector assembly 10. First, the seal portion 17, the four signal output cables 12, and the calibration conduit 13 are assembled (step S101). That is, the four signal output cables 12 and the calibration conduit 13 pass through the seal portion 17. Next, each of the four signal output cables 12 and the calibration conduit 13 is airtightly joined to the seal portion 17 at a portion where the seal portion 17 penetrates.

  Next, the combination of the seal portion 17 assembled in step S101, the signal output cable 12 and the calibration conduit 13 and the housing pipe 15 are assembled (step S102). Specifically, first, the seal portion 17 in which the four signal output cables 12 and the calibration conduit 13 are penetrated and joined is inserted into the housing pipe 15. Then, the outer periphery of the seal portion 17 and the inner surface of the housing pipe 15 are joined over the entire periphery. At this stage, an airtight partition in the housing pipe 15 is formed.

  Next, the housing pipe 15 and the cover pipe 16 are welded in series (step S103). That is, the upper end surface of the housing pipe 15 and the enlarged portion 16 a of the cover pipe 16 are welded at the welded portion B.

  In the LPRM 10 according to this embodiment as described above, the cross-sectional area of the cover pipe 16 at the welded portion B of the housing pipe 15 and the cover pipe 16 is large. That is, conventionally, the cross-sectional area at the welded portion with the housing pipe 15 is the same as the cross-sectional area of the portion in the core 2. On the other hand, in this embodiment, welding is performed at a portion after the cross-sectional area increases at the enlarged portion 16a.

  Since RT cannot be performed in the weld inspection of the welded portion B between the housing pipe 15 and the cover pipe 16, it is necessary to multiply the allowable stress by a welding efficiency that is lower than that in the case of performing RT. However, since the allowable shear force is the allowable stress, the welding efficiency, and the cross-sectional area of the welded portion, the allowable shear force increases by an area increase rate. For this reason, a margin for stress evaluation in the welded portion can be secured.

  In addition, the boundary where the thickness shifts from the thin portion to the thick portion is the conventional welded portion, but in this embodiment, since this portion is no longer the welded portion, the allowable value by multiplying the joint efficiency There is no decrease, and a margin for stress evaluation can be secured even in this portion.

  As described above, according to the present embodiment, it is possible to secure a margin on the structural strength of the LPRM by separating the portion where the cross-sectional area changes and the welded portion.

[Second Embodiment]
FIG. 4 is a vertical partial cross-sectional view illustrating a partial configuration of the local output region neutron detector assembly 10 according to the second embodiment. This embodiment is a modification of the first embodiment. In the second embodiment, the cover pipe 22 of the LPRM has no portion like the enlarged portion in the first embodiment, and has the same outer shape from the upper end to the lower end. In the second embodiment, an adapter 21 is provided between the cover pipe 22 and the housing pipe 15.

  The adapter 21 has a tubular shape whose upper and lower sides are open, and the inner surface has a constant diameter. The upper end of the adapter 21 has a cross section facing the cross section of the cover pipe 22, and the lower end has a larger cross sectional area than the upper end. The adapter 21 has a truncated cone-shaped enlarged portion 21a in the middle, and extends downward after the outer diameter increases. The adapter 21 is welded to the cover pipe 22 at the upper end. The lower end of the adapter 21 is welded to the housing pipe 15.

  Note that the lower end of the adapter 21 does not necessarily have the same outer diameter as the housing pipe 15. If the area where the cross section of the adapter 21 and the cross section of the housing pipe 15 that are opposite to each other overlap is sufficient for strength evaluation, both It does not matter whether the outer diameter and inner diameter of each other are large or small.

  FIG. 5 is a flowchart showing the procedure of the method for assembling the local output region neutron detector assembly. In the present embodiment, first, the seal portion 17, the four signal output cables 12, and the calibration conduit 13 are assembled (step S101). Next, the step of assembling with the housing pipe 15 (step S102) is the same as in the first embodiment.

  Next, the adapter 21 is welded to the cover pipe 22 (step S121). At the welded portion between the cover pipe 22 and the adapter 21, the cross-sectional areas of both the cover pipe 22 and the adapter 21 are small. RT is performed on this weld.

  Next, the housing pipe 15 is welded to the adapter 21 welded to the cover pipe 22 (step S122).

  According to the present embodiment, the location where the cross-sectional area changes is the inside of the adapter 21, the both ends of the adapter 21 are the weld locations, and the location where the cross-sectional area changes and the weld location are separated, whereby the structural strength in the LPRM. The top margin can be secured.

  Further, by making the portion where the cross-sectional area changes be within the adapter 21 that is shorter than the cover pipe 22 and the housing pipe 15, the manufacturing burden can be greatly reduced.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, embodiment is shown as an example and is not intending limiting the range of invention. The 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.

  The embodiments and the modifications thereof are included in the scope of the invention and the scope of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel (RPV), 2 ... Core, 3 ... Core support plate, 4 ... Upper lattice plate, 5 ... RPV nozzle base part, 5a ... Flange part, 6 ... Guide pipe, 7 ... Lower closing part, 7a ... Tapered part, 8 ... Cover pipe, 10 ... Local output region neutron detector assembly (LPRM), 11 ... neutron detector, 12 ... signal output cable (neutron detection storage), 13 ... calibration conduit (neutron) 14) spacer, 15 ... housing pipe, 15a ... taper part, 16 ... cover pipe, 16a ... expansion part, 16b ... expansion / contraction part, 17 ... seal part, 21 ... adapter, 21a ... expansion part, 22 ... Cover pipe

Claims (5)

In the local power region neutron detector assembly that measures the local neutron flux of the core stored in the reactor pressure vessel during the power operation of the reactor,
In the reactor pressure vessel, a tubular cover pipe that surrounds the radially outer side of the neutron detector and the neutron detection container and has an upper end and a lower end opened and extending in the vertical direction;
A housing pipe having an upper end and a lower end opened and extending in the vertical direction, the upper end being welded to the cover pipe and extending through the lower part of the reactor pressure vessel, and the neutron detection container passing through the lower end A tubular housing pipe extending as a
A disc-shaped seal portion provided between an upper end and a lower end of the housing pipe, through which the neutron detection storage product penetrates in an airtight manner;
With
The cover pipe has a portion in the core and an enlarged portion whose outer diameter expands from the upper end to the lower end below the lower end of the core, and the lower end of the enlarged portion at the connection portion with the housing pipe. The area where the cross section and the cross section of the upper end of the housing pipe overlap is larger than the cross sectional area of the portion of the cover pipe in the core,
A local output region neutron detector assembly characterized by that. In the local power region neutron detector assembly that measures the local neutron flux of the core stored in the reactor pressure vessel during the power operation of the reactor,
In the reactor pressure vessel, a tubular cover pipe that surrounds the radially outer side of the neutron detector and the neutron detection container and has an upper end and a lower end opened and extending in the vertical direction;
An adapter whose upper end and lower end are opened and whose upper end is welded to the lower end of the cover pipe;
A housing pipe having an upper end and a lower end opened and extending in a vertical direction, wherein the upper end is welded to a lower end of the adapter and extends through a lower portion of the reactor pressure vessel, and the neutron detection container is the lower end A tubular housing pipe extending through the
A disc-shaped seal portion provided between an upper end and a lower end of the housing pipe, through which the neutron detection storage product penetrates in an airtight manner;
With
The adapter has an enlarged portion between an upper end and a lower end, and an area where a cross section of the lower end of the adapter and a cross section of the upper end of the housing pipe overlap each other at a connection portion with the housing pipe Larger than the area,
A local output region neutron detector assembly characterized by that. The neutron detection storage item is:
A signal output cable connected to the neutron detector and extending through the reactor pressure vessel below the neutron detector and transmitting an output signal of the neutron detector;
A traveling neutron detector for calibrating the neutron detector is provided to move up and down inside, and extends downward from the installation level of the neutron detector through the reactor pressure vessel and is closed at its upper end. A calibration conduit with an open bottom;
The local output region neutron detector assembly according to claim 1 or 2, characterized by comprising: A tubular cover pipe whose upper and lower ends are opened in the reactor pressure vessel and extend in the vertical direction;
A tubular housing pipe having an upper end and a lower end opened and extending in a vertical direction, and an upper end welded to the cover pipe and extending through a lower portion of the reactor pressure vessel;
A neutron detector disposed inside the cover pipe;
A neutron detection container that extends through the lower end of the housing pipe from the inside of the cover pipe, and
A disc-shaped seal portion provided between an upper end and a lower end of the housing pipe, through which the neutron detection storage product penetrates in an airtight manner;
A method for assembling a local output region neutron detector assembly comprising:
The neutron detection accommodating articles is passed through the seal portion, the seal portion joining step of joining the neutron detection accommodated article to the sealing portion and airtightly,
After the seal portion bonding step, the neutron detection storage products inserting the sealing portion penetrating into the housing pipe, and the seal portion outer bonding step of bonding the housing pipe and the sealing part in an airtight manner,
After the sealing portion outer bonding step, the housing pipe and, below the lower end or lower end of the enlarged portion of the expansion portion of the cover pipe having an enlarged portion whose outer diameter is enlarged from the upper end to the lower up to the lower end An overall joining step of welding the end of the side;
A method for assembling a local output region neutron detector assembly. A tubular cover pipe whose upper and lower ends are opened in the reactor pressure vessel and extend in the vertical direction;
An adapter having an enlarged portion whose upper end and lower end are opened, the upper end is welded to the lower end of the cover pipe, and the outer diameter expands from the upper end to the lower end;
A tubular housing pipe having an upper end and a lower end opened and extending in the vertical direction, and an upper end welded to the adapter and extending through a lower portion of the reactor pressure vessel;
A neutron detector disposed inside the cover pipe;
A neutron detection container that extends through the lower end of the housing pipe from the inside of the cover pipe, and
A disc-shaped seal portion provided between an upper end and a lower end of the housing pipe, through which the neutron detection storage product penetrates in an airtight manner;
A method for assembling a local output region neutron detector assembly comprising:
The neutron detection accommodating articles is passed through the seal portion, the seal portion joining step of joining the neutron detection accommodated article to the sealing portion and airtightly,
After the seal portion bonding step, the neutron detection storage products inserting the sealing portion penetrating into the housing pipe, and the seal portion outer bonding step of bonding the housing pipe and the sealing part in an airtight manner,
Welded to the upper end of the said cover pipe adapter, and the adapter welding performing a radiographic examination,
An overall joining step of welding the housing pipe and the lower end of the adapter after the adapter welding step;
A method for assembling a local output region neutron detector assembly.

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