A high temperature gas cooled reactor core structure with embedded control rods

Abstract

The present application relates to the technical fields of high temperature gas cooled reactor control rod, and discloses a high temperature gas cooled reactor core structure with embedded control rods, which comprises a cold helium channel, a second control rod extending along the axial direction of the cold helium channel and rotatably arranged around the axis of the cold helium channel, wherein the radial section of the second control rod is arc-shaped, and the number of the second control rods is equal to that of the cold helium channels; a control rod channel; and a first control rod extending along the axial direction of the control rod channel and slidably arranged along the axis of the control rod channel, wherein the number of the first control rods is not equal to that of the control rod channels.The present application has the beneficial effect that by arranging the second control rods in the cold helium channel, the number of adjusting rods and corresponding driving mechanisms in the first control rods can be reduced, the circumferential space can be saved, the staff can easily maintain and replace the adjusting rods, and the reactor can be easily controlled.

Description

Technical Field

[0001] This invention relates to the field of high-temperature gas-cooled reactor control rod technology, and in particular to a high-temperature gas-cooled reactor core structure with embedded control rods and a high-temperature gas-cooled reactor core structure with embedded control rods. Background Technology

[0002] The pebble bed high-temperature gas-cooled reactor (PBT) is a fourth-generation advanced nuclear reactor that uses helium as a coolant. Helium is an inert gas that does not absorb neutrons and does not undergo a phase transition, thus improving the safety and stability of the reactor operation. Furthermore, the PBT employs a continuous online refueling strategy, resulting in a relatively flat power and burnup distribution within the reactor core, which is beneficial for improving fuel utilization.

[0003] In the prior art, the core of a pebble bed type high-temperature gas-cooled reactor is provided with a fuel zone 101, a middle reflector layer 102, a shielding layer 105, and control rod channels 103 and cold helium channels 104 arranged in the middle reflector layer. The cold helium channel 104 is used to transport helium gas. The first control rod 103a is placed inside the control rod channel 103. The first control rod 103a is divided into three types: adjustment rod R, safety rod S, and compensation rod C. Both the control rod channel 103 and the cold helium channel 104 extend along the axial direction of the core and are circumferentially distributed around the core. Both the control rod channel 103 and the cold helium channel 104 are arranged in the middle reflector layer 102, and the cold helium channel 103 is located away from the core.

[0004] The top and bottom of the shielding layer 105 are respectively provided with a feed pipe 101c and a discharge pipe 101e. The upper and lower parts of the shielding layer 105 are respectively provided with an upper fuel reflective layer 101b and a lower fuel reflective layer 101d. The upper fuel reflective layer 101b and the fuel area 101 form a top cavity 101a.

[0005] Each control rod channel 103 contains a first control rod 103a. Each first control rod 103a is driven by a drive mechanism 103b, causing the first control rod 103a to rise or fall. Taking 16 first control rods 103a as an example, there are 4 safety rods S, 6 adjusting rods R, and 6 compensating rods C. The specific distribution is shown in the attached figure. Figure 1 As shown.

[0006] For the drive mechanism 103b, a stepper motor can be used as the power source. The operation of the stepper motor is controlled by the controller of the reactor power control system. The controller causes the stepper motor to rotate in the forward or reverse direction according to the operator's manual or automatic command to raise or lower the rod, thereby raising or inserting the first control rod 103a as required. Alternatively, the drive mechanism 103b can also be a cylinder or other device that can be controlled by the controller of the reactor power control system and can drive the first control rod 103a to perform the raising and inserting actions.

[0007] Due to the large core height, the first control rod 103a has a long stroke. The first control rod 103a adopts a segmented inner and outer sleeve structure, and the number of circumferential first control rods is too large, resulting in a dense arrangement of the first control rod drive mechanism at the top of the reactor, which occupies a large amount of circumferential space, making maintenance difficult and adjustment cumbersome. Summary of the Invention

[0008] In this section, as well as in the abstract and title of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this section, the abstract, and the title of this application, and such simplifications or omissions shall not be used to limit the scope of the invention.

[0009] The purpose of this invention is to provide a high-temperature gas-cooled reactor core structure with embedded control rods, which can solve the problems of using segmented inner and outer sleeve structures for control rods and having too many circumferential control rods, resulting in a dense arrangement of control rod drive mechanisms at the top of the reactor, occupying a large amount of circumferential space, causing maintenance difficulties, and making adjustment cumbersome.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-temperature gas-cooled reactor core structure with embedded control rods, comprising: a cold helium channel; a second control rod extending axially along the cold helium channel and rotatably disposed about the axis of the cold helium channel, wherein the radial cross-section of the second control rod is arc-shaped, and the number of the second control rods is equal to the number of cold helium channels; a control rod channel; and a first control rod extending axially along the control rod channel and slidably disposed about the axis of the control rod channel, wherein the number of the first control rods is unequal to the number of control rod channels.

[0011] In a preferred embodiment of the high-temperature gas-cooled reactor core structure with embedded control rods as described in this invention, the interior of the second control rod is hollow.

[0012] In a preferred embodiment of the high-temperature gas-cooled reactor core structure with embedded control rods as described in this invention, the second control rod is made of a neutron-absorbing material.

[0013] In a preferred embodiment of the high-temperature gas-cooled reactor core structure with embedded control rods as described in this invention, the second control rod has an arc range of 60 degrees to 120 degrees.

[0014] In a preferred embodiment of the high-temperature gas-cooled reactor core structure with embedded control rods as described in this invention, the outer arc surface of the second control rod is in close contact with the sidewall of the cold helium channel.

[0015] As a preferred embodiment of the high-temperature gas-cooled reactor core structure with embedded control rods described in this invention, the thickness of the second control rod depends on the neutron absorption cross section and the neutron energy spectrum.

[0016] As a preferred embodiment of the high-temperature gas-cooled reactor core structure with embedded control rods according to the present invention, the thickness of the second control rod is the thickness of the hollow side inside the second control rod; wherein the thickness of the second control rod is the same on both sides of the hollow part.

[0017] In a preferred embodiment of the high-temperature gas-cooled reactor core structure with embedded control rods as described in this invention, the second control rod rotates synchronously.

[0018] As a preferred embodiment of the high-temperature gas-cooled reactor core structure with embedded control rods according to the present invention, wherein: a connecting post is fixedly connected to the top of the second control rod, the top end of the connecting post penetrates through the core, and the length of the second control rod is greater than the length of the cold helium channel.

[0019] As a preferred embodiment of the high-temperature gas-cooled reactor core structure with embedded control rods described in this invention, the connecting column is cylindrical, and the contact portion between the connecting column and the reactor core is sealed by a through-hole.

[0020] The beneficial effects of the present invention are as follows: By setting the second control rod, the present invention can reduce the number of regulating rods and their corresponding drive mechanisms in the first control rod, reduce the use of circumferential space, facilitate maintenance and replacement by staff, and facilitate reactivity control of the reactor. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0022] Figure 1 This is a top-view cross-sectional structural diagram of a conventional reactor core.

[0023] Figure 2This is a schematic diagram of the core structure of a high-temperature gas-cooled reactor with embedded control rods.

[0024] Figure 3 This is a frontal sectional view of the core structure of a high-temperature gas-cooled reactor with embedded control rods.

[0025] Figure 4 This is a top-view cross-sectional view of the core structure of a high-temperature gas-cooled reactor with embedded control rods.

[0026] Figure 5 The diagram shows the first control rod in the core structure of a high-temperature gas-cooled reactor with embedded control rods.

[0027] Figure 6 The diagram shows the first control rod in the half-rotation state of the high-temperature gas-cooled reactor core structure with embedded control rods.

[0028] Figure 7 The diagram shows the state transition of the first control rod in the core structure of a high-temperature gas-cooled reactor with embedded control rods. Detailed Implementation

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0030] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0032] Example 1

[0033] Reference Figures 2-7This is the first embodiment of the present invention, which provides a high-temperature gas-cooled reactor core structure with embedded control rods, comprising: a cold helium channel 104; a second control rod 104a extending axially along the cold helium channel 104 and rotatably configured about the axis of the cold helium channel 104, wherein the radial cross-section of the second control rod 104a is arc-shaped, and the number of the second control rod 104a is equal to that of the cold helium channel 104; a control rod channel 103; and a first control rod 103a extending axially along the control rod channel 103 and slidably configured about the axis of the control rod channel 103, wherein the number of the first control rod 103a is unequal to that of the control rod channel 103.

[0034] When only the first control rod 103a exists in the reactor core, and the second control rod 104a is absent, in use, taking 16 first control rods 103a as an example, they are respectively...

[0035] In the shutdown state, all the regulating rods R, safety rods S and compensation rods C in the control rod channel 103 are inserted into the control rod channel 103.

[0036] During reactor operation, the four safety rods S are first raised to the top via a drive mechanism. Then, the regulating rods R and compensation rods C are raised to the top via the same drive mechanism. While the reactor is reacting, the regulating rods R are raised or lowered via a drive mechanism to precisely control the reactor's reactivity. When adjusting reactivity via the regulating rods R, all six regulating rods R need to be adjusted to ensure that they reach the same height. Each regulating rod R needs to be adjusted individually. First, the required adjustment height for each regulating rod R is calculated using existing methods. Then, the drive mechanism corresponding to each regulating rod R is activated sequentially to adjust the regulating rod R to the appropriate height. Only one regulating rod R can be raised at a time until all are adjusted.

[0037] Safety rod S is used for emergency reactor shutdown, while compensating rod C is used to compensate for reactivity during power regulation. During normal operation, safety rod S is always pulled out of the reactor. Regulating rod R is responsible for reactivity regulation within the 100% to 50% power range. Reactivity regulation below 50% power requires the participation of compensating rods. The reactor maintains approximately 1000 pcm of backup reactivity for reactivity compensation during operational transients such as power regulation. Here, 1000 pcm is an example representing regulation within the 100% to 50% power range; the specific value needs to be determined based on the specific reactor core model and size.

[0038] When the reactor core has the second control rod 104a but the first control rod 103a is absent, the simulated parameters during use are as follows:

[0039] Fuel zone 101 is located in the center of the reactor core, with a radius of 150cm and a height of 1100cm;

[0040] The thickness of the intermediate reflective layer 102 is 75 cm;

[0041] The cold helium channels 104 arranged in the middle reflector layer 102 have a radius of 30 cm and a number of 16. The bottom of the cold helium channels 104 is flush with the upper edge of the bottom funnel of the reactor core.

[0042] The thickness of the shielding layer 105 is 25cm;

[0043] Fuel spheres and graphite spheres are deposited in the sphere bed of fuel zone 101. The fuel spheres are based on graphite and contain a large number of dispersed uranium dioxide TRISO fuel particles. The fuel enrichment is 4.2%. The radius of both fuel spheres and graphite spheres is 3 cm.

[0044] The absorber material of the second control rod 104a is boron carbide. The second control rod 104a has a hollow arc structure of 120 degrees, with an inner diameter of 20 cm and an outer diameter of 30 cm.

[0045] The thickness of the upper fuel reflective layer 101b is 100cm, the thickness of the lower fuel reflective layer 101d is 300cm, the radius of the feed pipe 101c is 25cm, and the radius of the discharge pipe 101e is 25cm.

[0046] To analyze the core physics characteristics of a pebble bed high-temperature gas-cooled reactor with an embedded control drum in the cold helium channel, based on the above model parameters, the Monte Carlo physics calculation software NECP-MCX was used to model and analyze the pebble bed high-temperature gas-cooled reactor with an embedded control drum in the cold helium channel, assuming a core temperature of 30℃. The four states of the second control rod 104a are as follows: Figures 4-7 As shown in the table below, the reactive values ​​of the second control rod 104a at the outward, half-turn, and inward states of the model under three different control drum states were calculated.

[0047] Controlling the drum state Reactivity value / pcm Transfer out 4149 Half turn 4307 Transfer 4671

[0048] "Turn in": This refers to the position where the apex of the arc of the second control rod 104a points towards the center of the reactor core, and the outer arc of the second control rod 104a is closest to the reactor core.

[0049] Half-rotation: refers to the direction of the arc apex of the second control rod 104a being perpendicular to the line connecting the center of the cold helium channel 104 and the center of the reactor core.

[0050] "Transfer out" refers to the position where the outer arc surface of the second control rod 104a is away from the core.

[0051] The Monte Carlo physics calculation software NECP-MCX is a deep-penetrating, multi-scale radiation field analysis software developed by the Nuclear Engineering Computational Physics Laboratory and possessing completely independent intellectual property rights.

[0052] like Figure 7 As shown, when the second control rod 104a is in the transition state, its outer arc surface is closest to the center of the core, absorbing the most neutrons. When the second control rod 104a rotates from the transition state to the... Figure 6 During the half-rotation process shown, the area of ​​the second control rod 104a facing the core center decreases, and the number of neutrons absorbed gradually decreases. When the second control rod 104a rotates to the point shown... Figure 5 In the transition state shown, the inner arc surface of the second control rod 104a is furthest from the core, absorbing the fewest neutrons and providing the least reactivity value.

[0053] As shown in the table above, the reactivity difference of 522 pcm between the input and output of the second control rod 104a can be used for reactivity compensation during reactor operation. For a reactor core with the first control rod 103a, the high-temperature gas-cooled reactor maintains a backup reactivity of approximately 1000 pcm during normal operation for reactivity compensation during transient events such as power regulation. The reactivity control method using the second control rod 104a can essentially replace about half of the reactivity compensation function of the commonly used first control rod 103a. In other words, taking 16 first control rods 103a as an example, the second control rod 104a can replace 2 to 4 of the 6 regulating rods R, depending on the specific core model. Therefore, it can be used as one of the reactivity control systems, providing a certain reactivity control capability, reducing the number of first control rods 103a required, and saving space for the installation of the control rod drive mechanism above the reactor cavity.

[0054] With both the first control rod 103a and the second control rod 104a present in the reactor core, the second control rod 104a is positioned in the cold helium channel 104 and participates in the reactivity control of the reactor core. This effectively reduces the number of regulating rods R in the first control rod 103a, thereby reducing the number of drive mechanisms corresponding to the first control rod 103a above the reactor cavity and saving installation space. The drive structure required for the second control rod 104a is located outside the first control rod 103a, with a certain distance between them. The drive structure of the second control rod 104a can drive multiple second control rods 104a to rotate synchronously, ensuring the stability of the regulation.

[0055] Furthermore, when adjusting the adjusting rod R in the first control rod 103a, since the drive mechanism 103b corresponds one-to-one with the adjusting rod R and their positions are asymmetrical, each adjusting rod R needs to be adjusted individually. However, the second control rod 104a does not have the above situation. Multiple second control rods 104a can be controlled to rotate synchronously through a single drive structure. This avoids the situation of local overheating or insufficient power caused by lifting a single adjusting rod R. When adjusting the first control rod 103a and the second control rod 104a, they need to be operated separately and cannot be operated simultaneously.

[0056] Because the cold helium channel 104 is a cold helium channel, when helium gas passes through the cold helium channel 104, it will cool the second control rod 104a. There is no need to set up a functional bypass, and the effective flow rate of the core is not reduced, which has advantages in reactor thermal safety. However, since the second control rod 104a is added to the core, the number of first control rods 103a in the core will be reduced accordingly. At the same time, the functional bypass is reduced, the consumption of helium gas is reduced, and resources are saved.

[0057] Example 2

[0058] Reference Figures 2-7 This is the second embodiment of the present invention, which differs from the first embodiment in that: the interior of the second control rod 104a is hollow.

[0059] Furthermore, the second control rod 104a is made of a neutron-absorbing material.

[0060] The absorber material of the second control rod 104a is boron carbide, but it can also be other neutron absorbing materials, such as indium or molybdenum, so that the second control rod 104a can fully absorb neutrons, thereby achieving control and regulation of the reactor and ensuring the normal operation of the reactor.

[0061] The second control rod 104a is hollow inside, which reduces damage caused by thermal expansion and contraction. During the reactor core reaction, gamma rays generated inside the core deposit energy as they pass through the second control rod 104a, generating heat. This causes excessive heat buildup inside the second control rod 104a. The hollow structure facilitates heat dissipation, preventing excessive internal heat and potential damage. Furthermore, the hollow design of the second control rod 104a reduces its weight while ensuring normal neutron absorption, thus minimizing energy loss in the corresponding drive structure.

[0062] Specifically, the arc range of the second control rod 104a is 60 degrees to 120 degrees.

[0063] Furthermore, the outer arc surface of the second control rod 104a is in close contact with the side wall of the cold helium channel 104.

[0064] Furthermore, the second control rod 104 rotates synchronously.

[0065] The curvature of the second control rod 104a can be selected according to the core model and actual usage. When selecting, the curvature of the second control rod 104a should not be too large or too small. If it is too large, it will cause neutrons to be absorbed at the same rate after adjusting a certain angle. Excessive neutron absorption may lead to poor neutron economy and reduced reactivity of the reactor, thereby affecting the critical state and energy output of the reactor. Excessive curvature will also cause material waste and increase the weight, resulting in resource waste. If the curvature of the second control rod 104a is too small, it will result in too few neutrons being absorbed, and the purpose of adjustment cannot be achieved.

[0066] The outer arc surface of the second control rod 104a is in close contact with the inner wall of the cold helium channel 104, ensuring stability when the drive structure of the second control rod 104a rotates, further ensuring the stable regulation of the reactor. The synchronous rotation of all the second control rods 104a in the core ensures stability during rotation and prevents the power difference at a certain point in the core due to different rotation angles, which may cause problems in the core reaction.

[0067] Specifically, the thickness of the second control rod 104a depends on the neutron absorption cross section and the neutron energy spectrum.

[0068] Furthermore, the thickness of the second control rod 104a is the thickness of the hollow side inside the second control rod 104a; wherein the thickness of the second control rod 104a on both hollow sides is the same.

[0069] The second control rod 104a consists of an absorber and an outer shell. The selection of absorber and shell materials is determined based on the specific reactor design; this is existing technology and will not be elaborated upon further. The thickness of the absorber in the second control rod 104a is mainly related to its neutron absorption cross-section and neutron energy spectrum. The larger the neutron absorption cross-section of the absorber, the thinner the absorber; the smaller the neutron absorption cross-section, the thicker the absorber. The optimal thickness of the absorber can be defined as the thickness at which all neutrons passing through the absorber are absorbed.

[0070] If the absorber is too thin, it will not absorb neutrons sufficiently, and the reactivity value of the second control rod 104a will be low. If the absorber is too thick, neutrons will be absorbed at the surface, and the absorber will not be able to absorb neutrons inside, which will waste materials, increase the mass of the second control rod 104a, and be detrimental to the drive. It will also cause an increase in the heat generated by the control rod (gamma heat sink). When designing the control rod structure, a reactor design program is used to determine the appropriate thickness of the absorber. This design program is existing technology and will not be described in detail here.

[0071] In operation, before reactor startup, a suitable number of first control rods 103a and a matching number of second control rods 104a are selected based on the reactor type and size and inserted into the control rod channels 103 and 104, respectively. The drive mechanism 103b and the required drive structure for the second control rods 104a are then installed in appropriate positions. After installation, before starting the reactor, the safety rod S is first pulled to the top using the drive mechanism 103b, followed by the compensation rod C and the regulating rod R. Then, based on the reactor's reactivity, the regulating rod R is placed in an appropriate position using the drive mechanism. The reactor is then started. During reactor operation, the regulating rod R can be gradually raised or lowered to a designated position using the drive mechanism 103b, depending on the reaction power. During adjustment, each regulating rod R is adjusted individually to stabilize the reactor power at a certain power platform. For reactors with high overall reactivity control requirements, both the first control rod 103a and the second control rod 104a need to participate simultaneously; for reactors with low requirements, the first control rod 103a may not be involved.

[0072] For reactors with smaller reactivity, the rotation of the second control rod 104a needs to be controlled. The drive structure is used to synchronously rotate all the second control rods 104a to achieve a balance and match of reactivity.

[0073] Example 3

[0074] Reference Figures 2-7 This is the third embodiment of the present invention. Based on the first two embodiments, this embodiment further includes a connecting column 104b fixedly connected to the top of the second control rod 104a. The top end of the connecting column 104b penetrates the core. The length of the second control rod 104a is greater than the length of the cold helium channel 104.

[0075] Furthermore, the connecting post 104b is cylindrical, and the part of the connecting post 104b in contact with the reactor core is sealed by a through-hole.

[0076] The connecting post 104b connected to the top of the second control rod 104a penetrates the reactor core and extends outside the reactor core. It can be adapted to the external drive structure of the second control rod 104a, so that the drive structure can drive the second control rod 104a to rotate.

[0077] The top of the connecting column 104b can be equipped with a gear, which can mesh with the drive structure to achieve the effect of transmission. Alternatively, it can be driven by a belt to achieve the rotation of the second control rod 104a. The specific choice can be made according to the actual situation.

[0078] The purpose of using the through-hole is to ensure the seal at the connection while the connecting post 104b rotates normally, preventing the leakage of internal radioactive materials. The through-hole is existing technology and will not be described in detail here.

[0079] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-temperature gas-cooled reactor core structure with embedded control rods, characterized in that: include, Cold helium channel (104); The second control rod (104a) extends along the axial direction of the cold helium channel (104) and is rotatably configured about the axis of the cold helium channel (104). The radial cross section of the second control rod (104a) is arc-shaped, and the number of the second control rods (104a) is equal to the number of cold helium channels (104). Control rod channel (103); The first control rod (103a) extends along the axial direction of the control rod channel (103) and is slidably disposed along the axis of the control rod channel (103). The number of the first control rod (103a) and the number of control rod channels (103) are not equal. The first control rod (103a) is divided into an adjustment rod (R), a safety rod (S) and a compensation rod (C).

2. The high-temperature gas-cooled reactor core structure with embedded control rods as described in claim 1, characterized in that: The interior of the second control rod (104a) is hollow.

3. The high-temperature gas-cooled reactor core structure with embedded control rods as described in claim 1, characterized in that: The second control rod (104a) is made of neutron-absorbing material.

4. The high-temperature gas-cooled reactor core structure with embedded control rods as described in claim 1, characterized in that: The second control rod (104a) has an arc range of 60 degrees to 120 degrees.

5. The high-temperature gas-cooled reactor core structure with embedded control rods as described in claim 1, characterized in that: The outer arc surface of the second control rod (104a) is in close contact with the side wall of the cold helium channel (104).

6. The high-temperature gas-cooled reactor core structure with embedded control rods as described in claim 5, characterized in that: The thickness of the second control rod (104a) depends on the neutron absorption cross section and the neutron energy spectrum.

7. The high-temperature gas-cooled reactor core structure with embedded control rods as described in claim 6, characterized in that: The thickness of the second control rod (104a) is the thickness of the hollow side inside the second control rod (104a); wherein the thickness of the second control rod (104a) is the same on both sides of the hollow side.

8. The high-temperature gas-cooled reactor core structure with embedded control rods as described in claim 7, characterized in that: The second control rod (104a) rotates synchronously.

9. The high-temperature gas-cooled reactor core structure with embedded control rods as described in claim 8, characterized in that: The top of the second control rod (104a) is fixedly connected to a connecting post (104b), the top of which penetrates the core. The length of the second control rod (104a) is greater than the length of the cold helium channel (104).

10. The high-temperature gas-cooled reactor core structure with embedded control rods as described in claim 9, characterized in that: The connecting post (104b) is cylindrical, and the part of the connecting post (104b) in contact with the reactor core is sealed by a through-hole.

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