JPH08189986A - Structure for fixing pressure vessel housing - Google Patents

Abstract

PURPOSE: To mitigate thermal stress generating in end plates and welding part of a vessel in starting operation by making a gap formed between the inner surface of end plate penetration hole of a housing and the outer surface of the housing larger than the gap formed between the inner surface of stub tube or builtup welding parts and the outer surface of the housing. CONSTITUTION: The gaps between a housing 3 and a stub tube 4, and between the housing and an end plate 2 are changed by the tube 4 part and the end plate 2 part. More in detail, the gap 7 formed between the housing 3 and the end plate 2 is made ten times or more the gap between the housing 3 and the tube 4. By providing the gap 7, the air layer formed in the gap 7 works as insulator, suppresses the thermal flow from the end plate 2 to the internal fluid 8 in the housing 3 and makes temperature rise of the end plate 2 at startup easy, and the temperature difference between the tube 4 and the end plate 2 decreases, which leads to mitigating the thermal stress generated in the welding part 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a housing mounting structure for a pressure vessel, which is attached to an end plate of a pressure vessel of a nuclear reactor or the like through a nozzle (stub tube) or the like.

[0002]

2. Description of the Related Art A conventional through-hole structure of a housing attached to an end plate of a pressure vessel is, for example, as shown in FIG.
FIG. 6 shows an enlarged cross-sectional structure of the relevant part. In the figure, the housing 3 is attached to the end plate 2 by a welded portion 6 via a stub tube 4 (or an overlay welded portion 5) attached to the inner surface side of the pressure vessel 1 by a welded portion 5. Then, the housing 3 penetrates the end plate 2, and the gap 7 formed between the housing 3 and the stub tube 4 and the end plate 2 is generally connected to the welded portion 6 for stopping the shake of the housing 3 due to an earthquake and an external load. It is set to be very small for the purpose of reducing the transmission of force. For example,
In the case of the through hole of the control rod drive mechanism housing of the pressure vessel of a boiling water reactor (BWR), the gap 7 is 0.4 mm or less. However, the outer peripheral surface of the housing 3 contacts the internal fluid 9 of the pressure vessel 1. This internal fluid 9 is
High temperatures are usually the case in pressure vessels. Therefore, inside the housing 3, the internal fluid 9 of the pressure vessel 1 is protected for the purpose of protecting the internal structure from the function stop due to the high temperature.
A lower temperature internal fluid 8 may flow into the housing 3. In this case, since the temperature of the internal fluid 9 rises and becomes high due to the operation of the pressure vessel, the end plate 2, the housing 3, the stub tube 4, the welded portion 5, and the welded portion 6 shown in FIG.
A temperature difference occurs between the two and thermal stress is generated. This thermal stress is
Although it fluctuates during the operation of the pressure vessel 1, generally, the thermal stress becomes particularly large during the startup operation of the pressure vessel 1, that is, when the temperature of the internal fluid 9 of the pressure vessel 1 rises. In the startup operation of the pressure vessel 1, the temperature of the internal fluid 9 of the pressure vessel 1 gradually rises, but the stub tube 4 and the end plate 2 have different heat capacities, so that a temperature difference occurs during the startup operation. Since the end plate 2 has a very large plate thickness as compared with the stub tube 4 and has a large heat capacity, even if the temperature of the internal fluid 9 of the pressure vessel 1 rises, it does not easily rise. On the other hand, since the stub tube 4 has a small heat capacity, it is easy to follow the temperature rise of the internal fluid 9 in the pressure vessel. Therefore, a temperature difference is generated between the stub tube 4 and the end plate 2, and thermal stress is generated in the welded portion 5. However, when the internal fluid 8 of the low-temperature housing 3 flows into the housing 3, the heat of the end plate 2 is changed to a gap (gap). ) 7 and the housing 3, the temperature rise during the start-up operation of the end plate 2 is further delayed, and the temperature difference between the stub tube 4 and the end plate 2 is further generated, and the thermal stress increases. As prior art, Japanese Patent Publication No. 5-64758 and Japanese Patent Laid-Open No.
For example, JP-A 1-270693 can be cited.

[0003]

As described above, in the prior art, especially during the startup operation of the pressure vessel 1,
The temperature of the fluid inside the pressure vessel gradually rises, but the stub tube and the end plate have different heat capacities, which causes a temperature difference. Since the end plate has an extremely large plate thickness and a large heat capacity as compared with the stub tube, the temperature does not rise easily even when the temperature of the internal fluid of the pressure vessel rises. On the other hand, since the stub tube has a small heat capacity, it easily follows the temperature rise of the internal fluid of the pressure vessel. Therefore, a temperature difference occurs between the stub tube and the end plate, and thermal stress is generated in the welded portion 5, but when a low-temperature internal fluid flows in the housing,
Since the heat of the end plate is taken away through the gap and the housing, the temperature rise during the start-up operation of the end plate is further delayed, and the temperature difference between the stub tube and the end plate becomes large, resulting in a significant increase in thermal stress. It was

An object of the present invention is to solve the above-mentioned problems in the prior art, and to alleviate the thermal stress generated in the penetration mounting welded portion between the end plate and the housing at the time of start-up operation of the pressure vessel, which is highly reliable. An object of the present invention is to provide a housing penetrating mounting structure for end plates of various pressure vessels such as nuclear power.

[0005]

In order to achieve the above-mentioned object of the present invention, the present invention has a structure as described in the claims. That is, according to the present invention, as described in claim 1, in a housing mounting structure for a pressure vessel, which is attached to the end plate of the pressure vessel via a stub tube by penetrating the housing by build-up welding,
The gap formed between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing is made larger than the gap formed between the inner surface of the stub tube or build-up weld and the outer peripheral surface of the housing. Thus, a housing mounting structure for a pressure vessel is formed in which a gap for heat insulation is formed between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing. Further, according to a second aspect of the present invention, in the housing mounting structure of the pressure vessel, which is attached to the end plate of the pressure vessel through the stub tube by overlay welding, the end plate through hole of the housing is provided. The gap formed between the inner surface of the housing and the outer peripheral surface of the housing to be larger than the gap formed between the inner surface of the stub tube or buildup weld and the outer peripheral surface of the housing. The structure is filled with a heat insulating material. Further, according to the present invention, as defined in claim 3, in claim 1 or 2, the gap formed between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing is provided with a stub tube or build-up welding. The gap is 10 times or more the gap formed between the inner surface of the portion and the outer peripheral surface of the housing.
Further, according to the present invention, as described in claim 4, in any one of claims 1 to 3, the shape of the gap formed between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing, A concave gap portion is formed on the inner surface side of the end plate or a concave gap portion is formed on the outer peripheral side of the housing, and the lateral deflection due to the external force of the housing is caused by the convex portion formed in the concave gap portion. It is a structure to suppress. Further, according to a fifth aspect of the present invention, in any one of the first to fourth aspects, the present invention is formed between the inner surface of the stub tube or the weld overlay and the outer peripheral surface of the housing. The gap is 0.4 mm or less, and the gap formed between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing is 4 mm or more.

[0006]

According to the housing mounting structure of the pressure vessel end plate of the present invention, as described in claim 1, the gap between the housing and the stub tube or the weld overlay is different between the stub tube and the end plate. The gap between the housing and the stub tube or the weld overlay is kept very narrow as before, and the gap between the housing and the end plate is made larger than that of the stub tube. . With this setting, the gap between the housing and the end plate is
Since it is an air layer, it is less likely to transfer heat as compared with contact with metal, and acts as a heat insulating material in the case of a thick gap, that is, an air layer. Therefore, by setting a large gap between the housing and the end plate, the two are insulated from each other, and the heat transfer from the end plate to the internal fluid of the low-temperature housing is suppressed, so that the end plate easily rises in temperature. Also, since the gap between the housing and the stub tube is very narrow as in the conventional case, the air layer in the gap portion does not act as a heat insulating material, and the heat of the stub tube is cooled by the internal fluid of the low temperature housing. As a result, the temperature rise of the stub tube is suppressed. For this reason, the temperature of the end plate tends to rise during the startup operation of the pressure vessel, the temperature difference between the housing and the end plate during the startup operation can be reduced, and the thermal stress can be relieved. Further, as described in claim 2, by filling the gap portion between the housing and the end plate with a heat-resistant heat insulating material which is usually used, the heat insulating effect can be enhanced more than that of the air layer, The heat transfer from the end plate to the internal fluid of the low temperature housing can be further suppressed, the temperature difference between the housing and the end plate at the time of start-up operation can be further reduced, and the thermal stress can be relieved. Further, as described in claim 3, specifically, the gap between the housing and the end plate is made 10 times or more larger than the gap of the stub tube portion. The heat insulation effect is improved, the temperature difference between the housing and the end plate at the time of start-up operation can be reduced, and the thermal stress can be relieved. Further, as described in claim 4, the shape of the gap formed between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing is such that a concave gap portion is formed on the inner surface side of the end plate, or A concave gap portion is formed on the outer peripheral side of the housing, and the convex portion formed in the concave gap portion can effectively suppress lateral shake due to an earthquake applied to the housing or other external force. . Further, as described in claim 5, the gap formed between the inner surface of the stub tube or the build-up weld and the outer peripheral surface of the housing is 0.4 mm or less, and the end plate through hole of the housing is practically used. By setting the gap formed between the inner surface of the housing and the outer peripheral surface of the housing to 4 mm or more, the temperature difference between the housing and the end plate during the startup operation of the pressure vessel can be kept small, and the thermal stress can be effectively reduced. Can be relaxed. As an example in the prior art, in the case of a housing through hole of a control rod drive mechanism of a boiling water reactor pressure vessel, the gap between the housing and the stub tube and the end plate is set to 0.4 mm or less. When this is set as a gap between the housing and the end plate of the present invention and is 10 times the gap between the housing and the stub tube, that is, 4 mm, the heat transfer coefficient indicating the transfer rate of heat passing through the gap is approximately It is given by the thermal conductivity of air divided by the gap width.
The thermal conductivity of air is about 0.04kcal / mh ° C at 350 ° C.
Therefore, the transfer rate is 0.04 kcal / mh ° C / 0.0.
04m = 10 kcal / m ² h ° C. Generally, the heat transfer coefficient between the inner fluid of the pressure vessel and the end plate is 10,000 kca.
Since it is as high as 1 / m ² h ° C., the above-mentioned gap width of 4 mm is sufficiently small as compared with the inflow amount of heat from the internal fluid of the pressure vessel of the present invention, so it can be said that the heat insulating effect is sufficient. Therefore, by setting the gap between the housing and the end plate to be 10 times or more the gap in the prior art, thermal stress is relieved and the object of the present invention can be achieved.

[0007]

Embodiments of the present invention will be described below in more detail with reference to the drawings. FIG. 1 is a schematic diagram showing a housing mounting structure of a pressure vessel end plate exemplified in this embodiment.
As shown in the figure, the feature of the present invention is the gap 7. That is, the gap formed between the housing 3 and the stub tube 4 and the end plate 2 is changed between the portion of the stub tube 4 and the end plate 2, and the gap of the gap 7 formed between the housing 3 and the end plate 2 is changed. Is a housing mounting structure in which the size of is greater than or equal to 10 times the gap (gap) between the housing 3 and the stub tube 4. By providing the gap 7 having the above size,
The air layer formed in the gap 7 acts as a heat insulating material, and suppresses the outflow of heat from the end plate 2 to the internal fluid 8 of the housing 3 during the start-up operation of the pressure vessel, and the end plate 2 during the start-up operation.
Temperature rises easily, so the stub tube 4 and end plate 2
The temperature difference between and is reduced, and the thermal stress generated in the welded portion 5 is relaxed. Another embodiment of the present invention is shown in FIGS. 2, 3, 4, 5 (a), 5 (b) and 6 (a), 6 (b).
Shown respectively. The embodiment shown in FIG. 2 has a structure in which a part of the outer surface of the housing 3 is shaved to form a step and a gap 7 is secured. In the embodiment shown in FIG. 3, the gap 7 is formed by cutting both the end plate 2 and the housing 3 to secure the gap. Moreover, the embodiment shown in FIG.
In order to facilitate the weldability and finish workability of the welded portion 5 with respect to the gap 7 in the housing mounting structure for the pressure vessel end plate shown in Fig. 4, the gap 7 is provided at a position slightly below the position of the welded portion 5. It is the structure provided. Also, FIG.
The embodiment shown in (a) has a recessed structure in which the projection 10 is left in the vicinity of the front opening of the housing through hole provided in the mirror plate 2 with respect to the gap 7 in the housing mounting structure of the pressure vessel mirror plate shown in FIG. Therefore, the effect of restraining the load from the outside by the protrusion 10 is obtained at the same time as the thermal stress is relaxed by the gap 7. The embodiment shown in FIG.
It has the same effect as that of FIG. 5A, and the outer surface of the housing 3 is shaved to provide a concave structure in order to secure the gap 7 and the projection 10. In addition, FIG.
In the embodiment shown in FIG. 1, by providing a heat insulating material in the gap 7, the housing 3 and the end plate 2 in the embodiment shown in FIG.
It has a structure that further improves the heat insulating effect between and. The embodiment shown in FIG. 6B has a structure in which a heat insulating material is applied to the gap 7 to further improve the heat insulating effect between the housing 3 and the end plate 2 in the embodiment shown in FIG. .

[0008]

As described above in detail, in the housing mounting structure of the pressure vessel end plate of the present invention, a gap or a heat insulating layer is provided between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing. Since it is possible to mitigate the thermal stress generated in the welded joint of the pressure vessel end plate and the through-hole of the housing, especially in the temperature rising stage at the time of start-up operation of the pressure vessel, the reliability of various pressure vessel end plates such as nuclear power can be reduced. A housing penetrating attachment structure can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a housing penetrating mounting structure of a pressure vessel end plate illustrated in an embodiment of the present invention.

FIG. 2 is a schematic view showing a housing penetrating mounting structure of another pressure vessel end plate illustrated in the embodiment of the invention.

FIG. 3 is a schematic view showing another housing mounting structure for a pressure vessel end plate illustrated in the embodiment of the present invention.

FIG. 4 is a schematic view showing a housing penetrating mounting structure of another pressure vessel end plate illustrated in the embodiment of the present invention.

FIG. 5 is a schematic view showing another housing mounting structure for a pressure vessel end plate illustrated in the embodiment of the present invention.

FIG. 6 is a schematic view showing a housing penetrating mounting structure of another pressure vessel end plate illustrated in the embodiment of the present invention.

FIG. 7 is a schematic diagram showing the overall configuration of a conventional pressure vessel.

FIG. 8 is a schematic diagram showing a conventional housing penetrating mounting structure of a pressure vessel end plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pressure container 2 ... End plate 3 ... Housing 4 ... Stub tube 5 ... Welding part 6 ... Welding part 7 ... Gap 8 ... Internal fluid of housing 9 ... Internal fluid of pressure container 10 ... Protrusion 11 ... Insulating material

Claims (5)

[Claims] 1. A housing mounting structure for a pressure vessel, which is attached to an end plate of a pressure vessel through build-up welding through a stub tube, wherein a housing is mounted between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing. A gap formed between the inner surface of the stub tube or the build-up weld portion and the outer peripheral surface of the housing, and the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing. A housing mounting structure for a pressure vessel, characterized in that a gap for heat insulation is formed between them. 2. A housing mounting structure for a pressure container, which is mounted on a mirror plate of a pressure container through build-up welding through a stub tube, wherein the housing is mounted between the inner surface of the mirror plate through hole and the outer peripheral surface of the housing. The gap formed between the stub tube or the buildup weld portion and the outer peripheral surface of the housing is made larger, and the gap portion is filled with a heat insulating material. Characteristic pressure vessel housing mounting structure. 3. The gap formed between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing according to claim 1 or 2, wherein the inner surface of the stub tube or the build-up welding portion and the outer peripheral surface of the housing are formed. A housing mounting structure for a pressure vessel, characterized in that it is formed 10 times or more than a gap formed between the pressure vessel and the pressure vessel. 4. The shape of the gap formed between the inner surface of the end plate through hole of the housing and the outer peripheral surface of the housing according to any one of claims 1 to 3, wherein a concave gap is formed on the inner surface side of the end plate. Or a concave gap portion is formed on the outer peripheral side of the housing, and a convex portion formed in the concave gap portion suppresses lateral shake due to an external force of the housing. A pressure vessel housing mounting structure. 5. The gap according to any one of claims 1 to 4, wherein the gap formed between the inner surface of the stub tube or the build-up welded portion and the outer peripheral surface of the housing is 0. A housing mounting structure for a pressure vessel, wherein the housing is 4 mm or less, and the gap formed between the inner surface of the housing end plate through hole and the outer peripheral surface of the housing is 4 mm or more.