JPS6234094A - Upper mechanism of core - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to improvements in the upper core mechanism of fast breeder reactors.

[Technical Background of the Invention] A fast breeder reactor, for example a loop fast breeder reactor, generally has the following configuration. That is, the reactor vessel contains a coolant (for example, liquid sodium) and a reactor core. This core is composed of a plurality of fuel assemblies, control rods, etc. Further, the reactor core is supported by the reactor vessel via a core support mechanism. The upper opening of the reactor vessel is closed by a shielding plug. This shielding plug is composed of a fixed plug fixed to the reactor vessel and a rotating plug rotatably installed on the inner peripheral side of the fixed plug. There is a gas space between the liquid level of the coolant and the shielding plug, which is filled with an inert gas such as argon gas.A core upper mechanism passes through the rotating plug above the core. It is installed.

In this configuration, the coolant that has flowed into the reactor vessel via the coolant inflow pipe passes directly upward into the reactor core. At that time, the reaction heat of the core causes the reactor to rise 7H and flow out above the core. The coolant flowing above the core is introduced into a heat exchanger installed outside the reactor vessel via a coolant outflow pipe, where it exchanges heat with the secondary cooling shrine. After that, it is supplied again into the reactor vessel via the circulation pump, and the same cycle is repeated thereafter.

The core upper mechanism is configured as shown in FIG. 6, for example. FIG. 6 is a sectional view showing a part of the upper core mechanism.

Reference numeral 101 in the figure is a joint shell, and the inside of this joint shell 101 is hollow, and an upper plate 102 is installed on the top thereof. A heat shielding layer 103 is provided at the bottom of the upper plate 102, and a cover gas space 107 is provided below the heat shielding layer 103.

This cover gas space 107 is filled with an inert gas such as argon gas. In addition, a control rod drive mechanism 104 and a core outlet instrumentation mechanism (not shown) are installed in the upper core mechanism, and the cover gas space 10
A rectifying mechanism (not shown) is installed above the core outlet below 7. Further, the upper part of the upper plate 102 is covered by an upper housing 106.

The control rod drive mechanism 104 includes a drive section 111 and an upper guide tube 112 installed below the drive section 111. The driving section 111 and the upper guide tube 112 are connected via a connecting section 113. A guide tube 114 is installed on the outer peripheral side of the drive section 111. In addition, when carrying out maintenance and inspection, the connection by the connection part 113 described in "1" is released, and the drive part 111 and the upper guide tube 112 are separated from each other. A seal mechanism 116 is installed between the upper guide tube 112 and the upper plate 102, and this seal portion 116 prevents the cover gas in the cover scum space 107 from flowing out of the furnace.

The control rod drive machine (104) will be replaced after being used for a certain period of time, or during the replacement work, the seal portion 116 may be damaged. This is because a quotient or the like occurs on the sealing surface of the plate 102.If this is left as is, there is a risk that the cover gas will leak as a result of the above.In such a case, the upper plate 1
02 will need to be replaced. To replace this upper plate 102, the upper housing 106, drive #111, upper guide tube 112
, the work of removing the guide tube 114 and the like is involved.

[Problems with background technology] According to the above configuration, there were the following problems.

That is, since the upper plate 102 is heavy and has a high radioactivity level, a cask is required for transportation after removal. Therefore, removing and replacing the upper plate 102 becomes an extremely difficult task. Furthermore, in addition to removing the upper plate 102, it is also necessary to remove the two-part housing 106, the guide tube 114, etc., and it is also necessary to replace them with new ones. For this reason, it was necessary to secure a large storage space, and it was not desirable in terms of cost, so a change of heart was required.

[Objective of the Invention] The present invention has been made based on the above-mentioned points, and its purpose is to prevent damage to the seal between the upper guide tube and the upper plate of the control rod drive mechanism. It is an object of the present invention to provide a core upper mechanism capable of reducing the number of parts to be replaced and the number of devices to be removed as much as possible.

[Summary of the Invention] That is, the core upper mechanism according to the present invention includes a joint shell installed in the reactor vessel through a shielding plug that closes the upper opening of the reactor vessel, and a joint shell installed at the upper end of the joint shell. A two-part reactor core comprising: a top plate that extends through the top plate, on-board equipment that extends through the top plate and is placed within the joint shell, and an upper housing that is installed to cover the top of the on-board equipment. The above-mentioned upper plate is divided into an upper plate and a lower upper plate, and a sealing portion for preventing leakage of the cover gas in the reactor vessel is installed at the penetration portion of the equipment on the upper upper plate. That is.

In other words, the upper plate is divided into an upper upper plate and a lower upper plate, and by installing a seal between the upper and upper plates, in the event that the seal is damaged, the upper plate can be removed. It is sufficient to replace only the upper plate of the improvement section.

[Embodiment of the Invention] A first embodiment of the invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a loop fast breeder reactor. Reference numeral 1 in the figure indicates a reactor vessel, and a coolant 2 and a reactor core 3 are accommodated within this reactor vessel 1. The reactor core 3 is composed of a plurality of fuel assemblies, control rods, etc. (not shown). The reactor core 3 is supported by the reactor vessel 1 via a core support machine (shaft 4).

The upper opening IA of the reactor vessel 1 is closed by a shielding plug 5. This shielding plug] is composed of a fixed plug 6 fixed to the reactor vessel 1 and a rotary plug 7 rotatably installed on the inner peripheral side of the fixed plug 6. Further, symbols 8 and 9 in the figure are coolant inflow pipes,
It is also a coolant outflow pipe. Further, a cover gas space 10 is formed between the liquid surface 2A of the coolant 2 and the shielding plug 5.
The cover gas space 10 is filled with an inert gas 11 such as argon gas.

Above the core 3, a core upper mechanism 12 is provided with the rotary plug 7.
It is placed through the. Below this core upper machine +M
The configuration of No. 12 will be explained. Reference numeral 21 in the figure is a joint shell, and the inside of this joint shell 21 is hollow. Above joint body 2
1, a control rod drive machine) 11122, a core exit instrumentation mechanism 23, etc. are installed. Further, a flow straightening mechanism 24 is installed between the lower end of the joint shell 21 and the reactor core 3.

An upper housing 25 is installed above the joint body 21. Further, an upper plate 26 is installed between the joint shell 21 and the upper 7X housing 25, and a heat shielding layer 27 is installed below this upper plate 26.

Next, the upper part of the upper core mechanism 12 will be explained in more detail with reference to FIG. The control rod drive mechanism 22 is composed of a drive section 31 and an upper guide tube 32, and these drive section 31 and the -L section guide tube 32 are connected via a connection section 33. A guide tube 34 is installed on the outer periphery of the drive section 31 .

The upper plate 26 is composed of an upper upper plate 26A and a lower upper plate 26B. The upper upper plate 26A is the lower upper plate 26
It is smaller and lighter than B. A seal portion 3 is provided between the upper plate 26A and the upper guide tube 32 to prevent leakage of the cover gas 11 in the cover gas space 10.
5 is installed. Through hole 36 in the upper upper plate 26A
The minimum diameter (dl) of the upper guide tube 32 is the maximum diameter (d2) of the upper guide tube 32.
It's bigger. That is, conventionally, when removing the upper plate, it was necessary to remove the upper guide pipe, but in the case of this embodiment, when only the upper plate 26A is removed,
There is no need to remove the upper guide tube 32. In the figure, reference numeral 41 is a sealing portion between the lower upper plate 26B and the joint body 21, and reference numeral 42 is a sealing portion between the upper upper plate 26A and the lower upper plate 26B. Further, reference numeral 43 is a sealing portion between the upper upper plate 26A and the guide tube 34.

The effect will be explained based on the +1llff configuration in Section 2 below. For example, suppose that a (H) scratch occurs on the seal portion 35 during the replacement work of the control rod drive mechanism 22.
This refers to a situation where a scratch occurs on the sealing surface of 6A. In this case, the drive section 31 is first removed.

Next, the guide tube 34 and upper housing 25 are removed. After this removal work, the upper L plate 26A is removed. Then, work such as replacing the upper plate with a new upper plate 26A is performed.

At this time, it is necessary to prevent leakage from the force filter 11, so a temporary seal is applied, for example, with a plastic pack.

According to this embodiment, the following effects can be achieved.

(1) First, in the case of this embodiment, it is not necessary to remove the entire top plate as in the conventional case, but only the relatively small and lightweight upper top plate 26A needs to be removed.

Further, there is no need to remove the upper guide pipe 32. Therefore, the replacement work is extremely easy and the work time is short. In addition, the level of activation in the upper upper plate is extremely low, so
A conventional cask is not required. As a result, the radiation exposure of workers can be reduced. Further, only the upper upper plate 26A is replaced, and therefore only the upper upper plate 26A is waste, which is advantageous in terms of cost and easy to dispose of waste. In particular, the upper guide tube 32 has an extremely high degree of radioactivity and is a precision machine that is expensive, so not having to remove it is extremely important in terms of not only improving workability and safety but also reducing costs. It's effective.

Next, with reference to FIG. 3, a second embodiment will be described with reference to FIG.

In this second embodiment, a seal portion 51 made of an O-ring is installed between the lower upper plate 26B and the upper guide tube 32, and the other configurations are the same as those of the first embodiment. According to this second embodiment, there is no need to apply a temporary seal as in the first embodiment when removing the upper upper plate 26A;
The seal portion 51 can prevent the cover gas from leaking.

Therefore, it is possible to achieve the same effect as in the first embodiment, and it is possible to prevent the leakage of the cover gas by installing a seal part in particular when replacing the temporary part 26A on d-1-. This makes the work extremely easy.

FIG. 4 is a diagram showing a third embodiment, and FIG. 5 is a diagram showing a fourth embodiment. This shows the deformation of . That is, in the case of FIG. 4, the seal portion 61 is made of a packing, and in the case of FIG. 5, the seal portion 71 is made of an inflatable seal. The inflatable seal 71 is a seal formed by supplying air or argon gas from the outside into an annular tube to inflate the tube.

Therefore, in the case of these third and fourth embodiments, the same effects as those of the second embodiment can be achieved.

``Effects of the Invention'' As detailed above, the core upper mechanism according to the present invention can prevent damage to the seal between the upper plate and the upper guide tube due to replacement of the control rod drive mechanism, for example. ,
It is sufficient to replace only the upper upper plate, which makes the work easier, minimizes the amount of radioactive waste, and facilitates subsequent disposal, which has great effects.

[Brief explanation of drawings]

1 and 2 are diagrams showing a first embodiment of the present invention, in which FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a loop fast breeder reactor, and FIG. 2 is a section H in FIG. 1. Enlarged cross-sectional view, 3rd
The figure is a partial sectional view of the upper core mechanism showing the second embodiment, and FIG. 4 is the third embodiment 1... reactor vessel, IA... upper opening of the reactor vessel, 5... shielding. Plug, 21... Joint shell, 22... Control rod drive mechanism, 23... Core outlet instrumentation mechanism, 25... Upper housing, 26... Upper plate,
26A... Upper upper plate, 26B... Lower upper plate, 31.
... Drive section, 32...'' Two-part guide tube, 35... Seal section. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (2)

[Claims] (1) A joint shell installed in the reactor vessel by penetrating the shielding plug that closes the upper opening of the reactor vessel, an upper plate installed at the upper end of this joint shell, and a penetrating through this upper plate. In a core upper mechanism comprising onboard equipment arranged in the joint shell and an upper housing installed to cover the upper part of the onboard equipment, the upper plate is separated into an upper upper plate and a lower upper plate. 1. A reactor core upper mechanism, characterized in that the reactor core upper mechanism is divided into parts, and a seal part for preventing leakage of the cover gas in the reactor vessel is installed in a penetration part of the above-mentioned equipment of the upper upper plate. (2) The core upper mechanism according to claim 1, wherein the lower upper plate is provided with a seal portion between it and the mounted equipment.