JP3886629B2 - Cavity seal device for nuclear reactor vessels - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure around a nuclear reactor vessel in a nuclear reactor containment vessel, and more particularly, to a sealing device provided between a nuclear reactor vessel of a pressurized water nuclear reactor and a shielding structure surrounding and supporting the reactor vessel.
[0002]
[Prior art]
In the pressurized water reactor, as shown in FIGS. 4 and 5, the reactor vessel 1 is suspended and supported in a space at the bottom of the reactor cavity 3 defined by the concrete structure in the reactor containment vessel. Yes. That is, in the reactor vessel 1, the vessel body 1a and the upper lid 1b are constituted by a plurality of stud bolts 1c and nuts 1d, and a narrow annular space 5 is formed between the vessel body 1a and the shielding wall 3a. During the operation of the nuclear reactor, a predetermined amount of air is passed through the annular space 5 to cool the shielding wall 3a. On the other hand, when the fuel of the reactor is changed, the upper lid 1a is removed, and water is further filled in the reactor cavity 3, so that the water is prevented from entering the annular space 5. In order to achieve the function of the annular space 5 as described above, a seal structure called a cavity seal 10 as shown in FIG. 6 is provided.
[0003]
FIG. 6A shows the state of the cavity seal 10 during operation of the reactor. A plate-like support ring 3b is embedded in the upper surface of the shielding wall 3a, and the support metal 11 and the presser metal 13 are fixed to the upper surface higher than the cavity floor 3c by bolts 15. A seal ring 19 held on the support metal 11 by a presser bolt 17 screwed to the presser metal 13 projects over the seal ledge 1aa of the container main body 1a to form a gap c therebetween. In this way, the cooling air that has flowed in the annular space 5 along the metal heat insulating material 1e surrounding the body portion of the vessel body 1a flows through the gap c as shown by the arrows and flows out into the reactor cavity 3, while Then, the shielding wall 3a heated by heat radiation of the reactor vessel 1 is cooled. The upper lid 1b is also surrounded by the metal heat insulating material 1f.
[0004]
FIG. 6B shows the state of the cavity seal 10 when the fuel is changed. In this state, a bracket 23 is further attached to the fixed hardware 21 fixed to the support ring 3b. The leveling pad 25 attached to the bracket 23 presses the seal ring 19 against the upper surfaces of the support ring 3b and the seal ledge 1aa. On the upper surfaces of the support ring 3b and the seal ledge 1aa, an annular seal groove is formed by double cutting, and a gasket (not shown) filled therein is brought into close contact with the lower surface of the seal ring 19 for sealing. Is established. In such a state, even if shielding water is applied to the reactor cavity 3, the shielding water does not leak into the annular space 5 through the cavity seal 10.
[0005]
[Problems to be solved by the invention]
In the conventional cavity seal as described above, the structure in the operation state of the reactor and the structure at the time of fuel change are different. Therefore, when the state is changed, the operator approaches the reactor vessel and the structure of the cavity seal is changed. It was necessary to replace the member or part. However, since the radiation level around the reactor vessel is high, there are many operational restrictions and it took a reasonable time.
Among the components of the cavity seal, the seal ring and gasket are one-piece larger than the reactor vessel, so it is difficult to attach and remove, requiring a lot of time, and shortening the periodic inspection time of the reactor It was an obstruction factor.
Accordingly, it is an object of the present invention to provide a reactor cavity seal device that does not require a change in the structure of the cavity seal between the operation of the reactor and the time of fuel change, and that can be easily changed in state. .
[0006]
[Means for Solving the Problems]
In order to solve the above problems, according to the present invention, a nuclear reactor vessel, an NIS junction that surrounds the nuclear reactor vessel, defines an annular space around the nuclear reactor vessel, and is provided with an openable / closable watertight lid at the top. Cavity seal device for a reactor having a shielding wall defining a box , and an annular bellows interposed between a seal ledge formed on the periphery of the reactor vessel and the upper surface of the shielding wall to close the annular space in a watertight manner in a ring duct which opens into the annular space on its shield wall, by providing a ventilation duct to contact the ring tact and the NIS junction box, provided with the function of the NIS junction box junction box A cooling air flow path is formed, and the annular bellows has an asymmetric concave cross section protruding downward. Preferably, a horizontal annular cover plate is disposed on the annular bellows to ensure a flat walking surface around the reactor vessel.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
Referring to the sectional view of FIG. 1 and the perspective view of FIG. 2, in a reactor containment vessel (not shown), the reactor vessel 31 is mainly composed of a vessel body 31a and an upper lid 31b. The container main body 31a and the upper lid 31b are covered with metal heat insulating materials 31c and 31d, respectively. A shielding wall 35 that forms the bottom surface of the reactor cavity 33 is provided outside the vessel body 31a of the reactor vessel 31, and an annular space 37 is defined between the vessel body 31a. Cooling air flows through the annular space 37 during the operation of the reactor, and the reactor cavity 33 is filled with shielding water during fuel replacement. On the upper surface 35 a of the shielding wall 35 which is the bottom surface of the reactor cavity 33, junction boxes, that is, NIS (nuclear instrumentation system) junction boxes 39 and concrete plugs 41 are alternately arranged along the outer periphery of the reactor vessel 31. Yes. A ring duct 43 is provided on the upper portion of the shielding wall 35 so as to face the annular space 37. Further, a ventilation duct 45 is provided between the ring duct 43 and the NIS junction box 39, and both form a flow path through which cooling air flows.
[0008]
Further, the ring duct 43 will be described in detail. As shown in FIG. 2, an inflow port 43 a is formed in the circumferential direction, and a ventilation slot 43 b is formed at an intermediate portion corresponding to the ventilation duct 45. Further, a lid plate 47 is placed on the NIS junction box 39 via a spacer 49 as shown in FIG. Further, an annular bellows 53 is provided between the seal ledge 31aa integrally formed around the container body 31a and the upper surface of the shielding wall 35, and an annular cover plate 55 is placed thereon. . The cover plate 55 is not fixed, and, for example, a divided structure in which a plurality of arc-shaped plate members are arranged in the circumferential direction and the ends thereof are overlapped is preferable. An enlarged cross section of the bellows 53 is shown in FIG. As shown in the figure, the cross section of the bellows 53 has a quarter arc shape with a large curvature on the reactor vessel 31 side, while the shielding wall 35 side has a semicircular shape with a small curvature. Is connected in a semicircular shape at the bottom. Further, the inner edge of the annular bellows 53 is seal welded to the upper surface of the seal ledge 31aa, and the outer edge thereof is seal welded to the upper surface of the ring duct 43. In FIG. 2, the cover plate 55 is not shown, and the bellows 53 is mostly cut away to show a lower state, and an extremely short circumferential length portion is shown.
[0009]
The state of FIGS. 1 and 2 described above shows the state during operation of the reactor, but the shielding wall 35 is heated by receiving radiant heat from the reactor vessel 31. However, the cooling air flows through the annular space 37 as indicated by the arrow to cool it. Further, since the upper portion of the annular space 37 is closed by the bellows 53, it flows into the ring duct 43 through the inlet 43 a and the ventilation slot 43 b of the ring duct 43 as indicated by the arrow, and a portion of the ventilation duct 45. To gather. After that, it flows into the NIS junction box 39 through the ventilation duct 45 and flows out into the reactor cavity 33 through the gap below the cover plate 47. The NIS cooling air also flows into the NIS junction box 39 from below and flows out together. The air that has flowed into the reactor cavity 33 is driven by a circulation blower or the like together with the air in the containment vessel, and is appropriately cooled. In the structure as shown in the figure, the air flow rate can be adjusted as necessary by appropriately changing the height of the spacer 49. When the reactor is operated, when the temperature of the reactor vessel 31 rises relatively and a relative displacement occurs between the shielding wall 35 and the vessel body 31a, it is absorbed by the elastic deformation of the bellows 53.
[0010]
When the operation of the nuclear reactor is finished and the operation is changed to the fuel exchange, the spacer 49 is removed from the NIS junction box 39 and the cover plate 47 is fixed to the upper surface by the mounting bolt 51. At this time, an appropriate gasket is interposed between the cover plate 47 and the NIS junction box 39 to perform sealing. Note that the upper surface of the annular space 37 is watertightly closed by a bellows 53. Next, the reactor cavity 33 is filled with shielding water. At that time, the upper lid 31b of the reactor vessel 31 is removed together with the metal heat insulating material at an appropriate timing, and is moved to a predetermined place. When the upper lid 31b is removed, stud bolts and nuts are removed, but the cover plate 55 provides a scaffold for work and a place for parts.
[0011]
【The invention's effect】
As explained above, according to the present invention, an annular bellows that is elastic and can absorb relative displacement is fixedly provided between the reactor vessel and the shielding wall, and in transition between operation and fuel exchange, Since the attachment of the cover plate of the junction box (NIS junction box) may be changed, the work for transition can be performed easily and in a short time, and the periodic inspection work can be shortened. Furthermore, since there is little work around the reactor vessel, the exposure of workers can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a partial vertical sectional view showing an embodiment of the present invention.
FIG. 2 is a partly omitted partial perspective view showing the overall structure of the embodiment.
FIG. 3 is a schematic partial enlarged sectional view showing a main part of the embodiment.
FIG. 4 is a plan view showing a structure of a conventional one.
FIG. 5 is a vertical sectional view showing the structure of a conventional one.
FIGS. 6A and 6B are partial sectional views showing a detailed structure of a conventional one, in which FIG. 6A shows a state when a nuclear reactor is operated, and FIG. 6B shows a state when a fuel is changed.
[Explanation of symbols]
31 reactor vessel 31a vessel body 31b upper lid 31aa seal ledge 33 reactor cavity 35 shielding wall 37 annular space 39 NIS junction box (connection box)
43 Ring duct 43a Inlet 43b Ventilation slot 45 Ventilation duct 47 Cover plate 49 Spacer 51 Mounting bolt 53 Bellows 55 Cover plate

Claims (2)

A reactor vessel, a shielding wall that surrounds the reactor vessel, defines an annular space around the reactor vessel, and forms a NIS junction box having an openable / closable watertight lid at the top ; and the reactor vessel An annular bellows interposed between a seal ledge formed at a peripheral edge and an upper surface of the shielding wall to close the annular space in a watertight manner; a ring duct opening in the annular space on the shielding wall; and the ring by disposing a ventilating duct communicating the tact and the NIS junction box, the NIS junction box to have a function of junction box to form a cooling air channel,
The nuclear reactor cavity seal device according to claim 1, wherein the annular bellows has an asymmetric concave cross section projecting downward.   The reactor vessel cavity seal device according to claim 1, wherein a horizontal annular cover plate is disposed on the annular bellows.

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