JPS6122291A - Pump mounting section of pressure vessel for nuclear reactor - 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 the Invention] The present invention relates to a reactor pressure vessel of a water-cooled nuclear reactor, and in particular increases the rigidity of a mounting part of a built-in reactor recirculation pump, improves vibration characteristics and Mid-service inspection of reactor pressure vessel (181)
This invention relates to a pump mounting section for a nuclear reactor pressure vessel that aims to reduce work.

[Technical background of the invention and its problems] At present, the external loop of the reactor recirculation system has been eliminated and an internal pump type recirculation system has been adopted instead, making the nuclear containment vessel more compact and reducing the reactor pressure. Interim inspection during service period (13
Progress is being made in the development of water-cooled nuclear reactors that reduce the number of welding lines that are subject to ＋), thereby reducing the amount of work and pump drive power required.

In this internal pump system, the in-reactor cross-shaped recirculation pump using a wet motor has a sleeve attached to a protruding part 2 protruding inside the lower head part 1a of the reactor pressure vessel 1, as shown in FIG. Motor casing 3 with welded 3a
a pump motor 4 having an H! A stretch tube 6 provided in the sleeve portion 3a of the motor casing 3 to do this, stretch tube collars 1 to 7 that fix the stretch tube 6 to the sleeve 3a, and a pump (not shown) connected to the rotating shaft of the pump motor 4 and rotated integrally with the pump motor 4. A shaft, an impeller (not shown) disposed inside the diffuser 5 and attached to the end of the pump shaft, a secondary seal 8 of the sealing reservoir inside the motor casing 3 from the reactor pressure vessel 1 side during maintenance of the pump motor 4, and the reactor. A purge water injection system that injects clean water from the top of the pump motor 4 into the reactor pressure vessel 1 side in order to prevent water from entering the motor casing 3 (however, only the purge water inlet 9 is shown in the figure) , a secondary seal that fills pressurized water into the secondary seal 8 (however, only the secondary seal inlet 10 is shown in the figure), a pump motor cooling water system that cools the pump motor 4 (however, the pump motor cooling water outlet is not shown in the figure). (only 11 are shown), etc.

However, the pump motor 4 is connected from the reactor pressure vessel 1 side.
In order to reduce heat input to the motor casing 3, a gap (not shown) is provided between the sleeve portion 3a of the motor casing 3 and the protruding portion 2, and the structure utilizes the heat insulating effect of air, so the rigidity of the protruding portion 2 is not necessarily large. This required the installation of a vibration isolator, complicating the equipment layout. Furthermore, since the welded joint between the motor casing 3 and the protrusion 2 is close to each other as shown by reference numeral 12 in FIG. 6, welding work and inspection thereof are not easy.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and improves the vibration characteristics by increasing the rigidity of the pump mounting part, and
It is an object of the present invention to provide a pump mounting part for a nuclear reactor pressure vessel in which the welding position can be easily accessed to facilitate welding work and inspection thereof.

[Summary of the Invention] The present invention provides a pump-driving motor that is mounted on the outside of the lower head of the reactor pressure vessel in a pump mounting portion of a reactor pressure vessel that is integrally equipped with a pump that supplies coolant to the reactor core. By integrally forming the mounting protrusion by forging, the rigidity of the pump mounting part is increased and vibration characteristics are improved.
The welding position is easily accessible to facilitate welding work and inspection.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, in which the same parts as in FIGS. 5 and 6 are given the same reference numerals, a protrusion 22 is integrally formed on the lower mirror portion 21a of the reactor pressure vessel 21 by, for example, forging. This protrusion 22
has a cylindrical shape and has an outer shape approximately equal to the outer shape of a motor casing 23 of a pump motor (not shown), and the end of the motor casing 23 (however, no sleeve is provided) is welded to the lower end of the motor casing 23. Reference numeral 24 indicates this welded joint, which maintains a predetermined pressure resistance. Furthermore, a protrusion 25 is welded to the inside of the lower mirror portion 21a, concentrically with the protrusion 22. Reference numeral 26 indicates this welded joint. Stretch tubes (not shown) are inserted into the protrusions 22 and 25 through the holes 27. Further, a rear part 27a is provided at the bottom of this hole 27, and a heat insulating material 28 is provided at the bottom of the hole 27 to reduce heat input from the reactor pressure vessel 21 side to the pump motor.
Insert and secure.

This heat insulating material 28 prevents heat transfer due to convection of cooling water in the motor casing 23 at the lower part of the protrusion 22 where the temperature difference is large, and functionally corresponds to the conventional gap described above. As shown in FIGS. 2 and 3, the structure consists of an annular housing 29 and thin metal plates 30 laminated inside the housing, reducing heat transfer due to thermal resistance between the contact surfaces of each metal plate 30. It is fixed to the rear part 27a of the hole 27 with a screw 31.

With the structure described above, the rigidity of the protrusion 22 to which the pump motor is mounted is greatly increased, which is different from the conventional protrusion 2.
In this case, the lower end of the pump motor vibrates as shown by A in Fig. 4, and its natural frequency (indicated by X) is within the operating range of the pump. As shown by B in the figure, the amplitude is small, and its natural frequency (indicated by Y6) can be set outside the pump's motion range, making it possible to eliminate resonance with the system during pump operation.

[Effects of the Invention] Since the present invention is configured as described above, the rigidity of the pump mounting portion is increased, vibration during pump operation and vibration response at the time of earthquake occurrence are reduced, and vibration characteristics are improved. Furthermore, it is not necessary to install a vibration isolator, and space can be used effectively. Furthermore, by setting the welded joint at an easily accessible position, it is possible to improve the ease and reliability of welding work, improve the workability of inspecting the welded joint, and reduce radiation exposure during work.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the pump mounting part of the reactor pressure vessel of the present invention, and FIG. 2 is a sectional view of the heat insulating material of the pump mounting part of the reactor pressure vessel of the present invention. Fig. 3 is a plan view of Fig. 2, Fig. 4 is a diagram showing the relationship between the amplitude and natural frequency of the motor casing of the embodiment of the present invention and a conventional pump motor, and Fig. 5 is a diagram showing the relationship between the amplitude and natural frequency of the motor casing of the embodiment of the present invention and the conventional pump motor. FIG. 6 is a sectional view showing a pump mounting structure of a conventional nuclear reactor pressure vessel. 5... Diffuser 6... Stretch cove 21... Reactor pressure vessel 21a... Lower mirror portion 22.25... Projection portion 23... Motor casing 24.26... Welded joint portion Agent: Patent Attorney Noriyuki Chika (and 1 other person) No. 1
Figure 2 Figure 3 Figure 5 Figure I 651!

Claims (4)

[Claims] (1) In a pump mounting portion of a reactor pressure vessel in which a pump for supplying coolant to the reactor core is integrally mounted, a protruding portion on the outside of a lower mirror portion of the reactor pressure vessel is mounted with a motor for driving the pump. A pump attachment part for a nuclear reactor pressure vessel, characterized in that it is integrally formed by forging. (2) A pump mounting portion for a reactor pressure vessel according to claim 1, characterized in that a motor casing is welded to the protruding portion. (3) The pump mounting portion for a reactor pressure vessel according to claim 1, wherein a protruding portion is provided on the inside of the lower mirror portion by welding. (4) A pump mounting portion for a reactor pressure vessel according to claim 1, characterized in that a heat insulating material is mounted inside the protruding portion.