JPH01121794A - Sealing mechanism of internal pump - Google Patents

Abstract

PURPOSE:To prevent leakage of reactor water and to prevent operators from being exposed by providing a piston ring on a stretching tube side so as to seal the spacing between the stretching tube and a diffuser mounting nozzle. CONSTITUTION:The piston ring 24 is provided between the inside surface of the diffuser mounting nozzle 15 and the outside surface of the stretching tube 13. The piston ring 24 is mounted in the groove provided on the stretching tube side for ease of handling. Sufficient sealing is thereby attained, since the pressure of the reactor water at the time of mounting and dismounting the internal pump is 2kg/cm<2> at the highest. The piston rings 24 are used by increasing the number thereof to a several pieces at need. Not the conventional sealing mechanism by the diffuser's and stretching tube's own weight but the piston ring mechanism is adopted in this case and the sealing is made on the face perpendicular from the horizontal face and, therefore, the engagement of foreign matter with the sealing face is obviated and the ambient contamination with radioactivity is obviated as well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a sealing mechanism for leakage from a diffuser attachment nozzle of an internal pump used for circulating coolant in a boiling water nuclear reactor.

(Prior Art) FIG. 2 is a sectional view of the inside of a pressure vessel of a boiling water nuclear reactor equipped with an internal pump. Namely.

In the figure, 1 is a reactor pressure vessel, and a shroud 2 is provided within this reactor pressure vessel 1, and a reactor core 3 is accommodated within this shroud 2.

A plurality of internal pumps 4, for example, ten internal pumps, are provided around the bottom of the reactor pressure vessel 1. Then, the reactor water in the reactor pressure vessel 1 descends in the downcomer 5 formed between the outer circumferential surface of the shroud 2 and the inner circumferential surface of the reactor pressure vessel 1, and the above-mentioned internal pump ±... * is sent to the lower part of the reactor core 3, and flows into this reactor core 3 from below. The reactor water that has flowed into the reactor core 3 is boiled by the heat generated by the nuclear reaction, and flows upward as a two-phase flow of water and steam. This two-phase flow of water and steam is separated into water and steam by a steam separator 6, and after moisture is removed from the separated steam by a steam dryer 7, it is sent to a turbine (not shown), etc. . Also.

The separated water is sent to the core 3 again by the internal pumps along with the water supplied from the water supply sparger 8. In addition, a plurality of (approximately 200) control rod drive mechanisms 9 are provided at the bottom of the reactor pressure vessel 1, and these control rod drive mechanisms 9 drive control rods (not shown). It is inserted into or pulled out of the reactor core 3 and is configured to control the reactivity of the reactor core 3 and the like.

The internal pump 4 is constructed as shown in FIG. 3. That is, 1o is a pump section, which is composed of a diffuser 11 and an impeller 12. The diffuser 11 is fixed by a stretch tube 13 and a stretch tube nut 14 to the tip of a diffuser attachment nozzle 15 protruding from the bottom of the reactor pressure vessel 1. Further, 16 is a motor case, which is welded to the reactor pressure vessel 1 and is provided to protrude from the bottom surface. A water immersion type motor 17 is housed within this motor case 16.

A monitor cover 17a is attached to the lower end of this motor 17, and this motor cover 17a covers the motor case 1.
6 and are tightened and fixed by nuts 19 threaded onto stud bolts 18 . . . to maintain liquid tightness and fix the motor 17 to the motor case 16 .

Further, this motor 17 and the impeller 12 are connected by a shaft 2o, and the impeller 12 is driven via this shaft 20.

(Problems to be solved by the invention) ゛The above-mentioned internal pump 4 is periodically disassembled and removed, and the removed parts are inspected and repaired at another location (outside the reactor containment vessel). It is carried out. To disassemble and remove this internal pump 4, first disconnect the motor 17 and shaft 20, then tighten the nut 1.
9 and pull out the motor 17 downward from the motor case 16, then pull out the impeller 12 and shaft 20 from above, then remove the stretch tube nut and remove the deep user 11 upward. When assembling the internal pump 4, follow the steps above. Follow the steps in reverse.

By the way, how to install and remove the internal pump 4,
Since the reactor pressure vessel is filled with water, installation and removal can be performed while preventing water leakage.

4 and 5 show the procedure for installing the diffuser 11.

In Figure 4, the motor case 16 is installed to prevent reactor water from flowing out.
A closing lid 21 is provided at the lower end of the lid. There, the assembled head diffuser 11 and stretch tube 13 is lowered from above.

After installing the diffuser 11 on the diffuser mounting nozzle 15 in FIG. 5, drain the water in the motor case 16, remove the closing lid 21, and attach the stretch tube 13 to completely fix the diffuser 11 and the diffuser mounting nozzle 15. Attach a stretch tube nut 14 for applying tensile force.

Closed! ! After removing 21, sealing of reactor water is done in section A. A detailed view of part A is shown in FIG. Diffuser 11
A seal ring 22 is provided between the diffuser mounting nozzle 15 and the diffuser mounting nozzle 15 . Before the stretch tube nut 14 is installed, several hundred pounds of dead weight of the diffuser 11 and stretch tube 13 is acting on the seal ring 22, but it will not function unless a load of several tons is applied, so a complete seal cannot be achieved with this weight. It is impossible, and the reactor water is 23.

In particular, if foreign matter enters the sealing surface or if the diffuser 11 is placed at an angle with respect to the diffuser attachment nozzle 15, the sealing function will be completely lost and leakage will occur.

A leak of reactor water increases the radiation exposure of each worker and contaminates the surrounding area with radioactivity.

The present invention has been made based on the above circumstances, and its object is to provide an internal pump diffuser that can completely seal between the diffuser and the diffuser attachment nozzle.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a seal mechanism between an internal pump and a pressure vessel installed at the bottom of a nuclear reactor pressure vessel, in which a piston is attached to the stretch tube side to seal between the stretch tube and a diffuser attachment nozzle. It is characterized by the provision of a ring.

(Function) In the sealing mechanism configured in this way, it becomes possible to completely seal between the internal pump and the pressure vessel by the piston ring, regardless of the weight of the stretch tube.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the invention. FIG. 1 is a sectional view of the position where the diffuser 11 and the diffuser attachment nozzle 15 come into contact. A piston ring 24 is provided between the inner surface of the diffuser attachment nozzle 15 and the outer surface of the stretch tube 13. For handling purposes, the piston ring 24 is installed in a groove provided on the stretch tube side. Installing the internal pump.

Since the pressure of the reactor water at the time of removal is at most 2 kg/j, a sufficient seal can be achieved. Also, if necessary, piston ring 2
Increase number 4 to several pieces and use.

〔Effect of the invention〕

As mentioned above, in the internal pump diffuser of the present invention, instead of the conventional sealing mechanism based on the weight of the diffuser and stretch tube, the piston ring structure ##銹滲楲杆会#◆ was used, and the sealing surface was changed from a horizontal surface to a vertical surface. There is no foreign matter getting into the sealing surface, sealing can be performed reliably, and there is no leakage of reactor water.
There will be no radiation exposure for workers, and there will be no radioactive contamination in the surrounding area.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a sealing mechanism using a piston ring of the present invention, FIG. 2 is a longitudinal sectional view of the inside of a nuclear reactor pressure vessel, and FIG. 3 is a longitudinal sectional view of an internal pump. FIG. 4 is a conceptual diagram when installing a diffuser, FIG. 5 is a conceptual diagram when installing a stretch tube, and FIG. 6 is a detailed diagram of a conventional seal portion. 1... Reactor pressure vessel 2... Shroud 3...
Core 4...Internal pump 5...Downcomer 6...Steam water separator 7...Steam dryer 8...Water supply sparger 9...Control rod drive mechanism 10...Pump section 11. ... Diffuser 12
... Impeller 13 ... Stretch tube 14 ... Stretch tube nut 15 ... Diffuser mounting nozzle 16 ... Motor case -17 ... Motor cover 18 ... Stud bolt 19 ... Nut 20.・
・Shaft 21...Closing lid 22...Seal ring 23...Reactor water leak 24...Piston ring representative Patent attorney Noriyuki Chika Ken Yudo Daishimaru Ken Figure 1 Figure 2 Figure 3 Figure 4 5121

Claims (1)

[Claims] In the sealing mechanism between the internal pump installed at the bottom of the reactor pressure vessel and the pressure vessel, an internal pump is characterized in that a piston ring is provided on the stretch tube side to seal between the stretch tube and the diffuser attachment nozzle. Seal mechanism.