JPH0275790A - Internal pump - Google Patents

Abstract

PURPOSE:To prevent accumulation of radiated clad in a pump casing 3 and to reduce a dose of exposure of a worker to radiation during periodic inspection by a method wherein an auxiliary blade is formed to the lower end of a pump impeller and reactor water is prevented from flowing in the inner cylinder of a diffuser. CONSTITUTION:A pump impeller 8 adapted to circulate a coolant is mounted to the upper and of a pumps shaft 7 inserted through a pump casing, and an auxiliary blade 16 is formed to the lower and of the pump impeller 8. Reactor water is introduced from a position above the pump impeller 8 and drained to below through rotation of the pump shaft 7, and simultaneously the auxiliary blade 16 generates a flow in a circumferential direction. The flow enables suppression of the generation of a vortex when purge water coming out through a gap between the pump impeller 8 and an inner cylinder 11 of a diffuser 9 is joined with reactor water. Radiated clad in reactor water flows in the inner cylinder of the diffuser and is suppressed from accumulation in the pump casing, and a radiation exposure dose of a motor part can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an internal pump for circulating coolant within a nuclear reactor pressure vessel.

(Prior Art) A conventional internal pump will be explained with reference to FIGS. 3 and 4.

The internal pump for circulating the coolant in the reactor pressure vessel has a plurality of pump nozzles 2 extending in the vertical direction formed in the lower head plate of the reactor pressure vessel 1 in the circumferential direction. The upper end of the pump casing 3 is attached to the inner peripheral surface. This pump casing 3 extends downward within the pump nozzle 2, and its lower end 4 faces the outside of the reactor pressure vessel 1. A stator 5 is fixedly disposed within the lower end portion 4 of the pump casing 3, and a row 6 is disposed opposite to the center of the stator 5.
The motor section of the internal pump is formed.

A pump shaft 7 passes through the pump casing 3 and reaches the inside of the reactor pressure vessel 1 at the upper end of the rotor 6.
is provided. A pump impeller 8 is attached to the upper end of the pump shaft 7, and the pump impeller 8 is accommodated in an outer cylinder 10 of a diffuser 9, forming a pump section of an internal pump. An inner cylinder 11 of a diffuser 9 connected to the outer cylinder 10 is seated on the upper end of the pump nozzle 2, and the diffuser 9 is fixed by a stretch dupe 12. That is,
Flanges 13.14 are provided around the upper and lower ends of the stretch tube 12 provided between the pump nozzle 2 and the pump shaft 7, respectively.
14 is engaged with and held by the inner cylinder 11 and the pump casing 3.

Inner cylinder 11 of the pump impeller 8 and diffuser 9
In order to prevent reactor water, which is primary cooling water, from entering between the pump shaft 7 and the inner cylinder 11, in other words, the activated cladding in the reactor is prevented from entering the inside of the pump casing 3. For this purpose, a purge water introduction pipe 15 is connected, and purge water is introduced between the pump casing 3 and the stretch tube 12 through this purge water introduction pipe 15.

(Problems to be Solved by the Invention) In the conventional internal pump, the pump impeller 8 rotates as the pump shaft 7 rotates. Reactor water is introduced from above the pump impeller 8, discharged downward, and flows into the reactor core along the lower head plate of the reactor pressure vessel 1. On the other hand, purge water with a water pressure slightly higher than that of reactor water is quantitatively supplied into the pump casing 3 from the purge water introduction pipe 15 and rises between the pump casing 3 and the stretch tube 12.
It flows out from the gap between the pump impeller 8 and the inner cylinder 11 of the diffuser and merges with the reactor water. At this time, the flow in the gap between the pump impeller 8 and the inner cylinder 11 of the diffuser is disturbed, a vortex is generated, and reactor water containing activated crud flows into the inner cylinder 11 of the diffuser. At this time, the activated cladding with a large specific gravity is placed in the stretch tube 12.
Mv4 is passed between the pump casing 3 and the radiation exposure line of the motor section is raised. For this reason, when the motor section is removed and disassembled for regular inspection, workers are exposed to a large amount of radiation.

The present invention was made in view of the above circumstances, and prevents activated crud from accumulating in the pump casing 3 by preventing reactor water from flowing into the inner cylinder 11 of the diffuser. can. The aim is also to reduce the radiation exposure of workers during periodic inspections.

[Structure of the Invention] (Means for Solving the Problems) A pump nozzle is formed in the lower end plate of the reactor pressure vessel, and a coolant is supplied to the upper end of the pump shaft that is inserted into the pump casing attached to the pump nozzle. The above problem can be solved by attaching a pump impeller for circulation, housing this pump impeller in a diffuser made of an outer cylinder and an inner cylinder, and forming auxiliary vanes at the lower end of the pump impeller.

(Function) In the internal pump configured as above,
By forming auxiliary vanes on the lower end of the impeller that protrudes from the pump shaft, a flow is generated in the outer circumferential direction from the gap between the lower end of the impeller and the diffuser, which prevents the generation of vortices when the purge water joins the reactor water. This makes it possible to suppress the activated cladding from entering into the pump casing.

(Example) An example of an internal pump according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 2 is a sectional view taken along the line AA in FIG. 1. In FIG. 1, the same parts as in FIGS. 3 and 4 are indicated by the same reference numerals, and the explanation of the overlapping parts will be omitted.

A pump nozzle 2 is formed on the lower end plate of the reactor pressure vessel,
Pump casing 3 attached to this pump nozzle 2
A pump impeller 8 is attached to the upper end of the pump shaft 7 passing therethrough for circulating coolant, and auxiliary vanes 16 are formed at the lower end of the pump impeller 8.

In the internal pump in which the auxiliary vanes 16 are formed in this manner, the pump impeller 8 rotates as the pump shaft 7 rotates, and reactor water is introduced from above the pump impeller 8 and discharged downward. The auxiliary vanes 1 formed on the pump impeller 8 are caused by the rotation of the pump impeller 8 at the same time.
6 generates a flow toward the outer circumference. This flow can suppress the vortex that is generated when the purge water flowing out from the gap between the pump impeller 8 and the inner cylinder 11 of the diffuser 9 and the reactor water merge. Note that the auxiliary blades 16 are not limited to the above-mentioned embodiments, and may have a slit at the spinner end of the impeller, for example, and various shapes can be applied.

[Effects of the Invention] According to the present invention, it is possible to suppress the vortex that occurs when purge water and reactor water join together, and the activated crud in the reactor water flows into the inner cylinder of the diffuser and the pump casing. It is possible to suppress the accumulation of radiation within the motor section, and it is possible to reduce the radiation exposure dose of the motor section.

[Brief explanation of the drawing]

FIG. 1 is an internal pump according to the present invention; FIG. 3 is a vertical cross-sectional view of a conventional internal pump; and FIG. 4 is a vertical cross-sectional view showing the vicinity of the pump impeller of the conventional internal pump. 1...Reactor pressure vessel 2...Pump nozzle 3...Pump casing 4...Pump casing lower end 5...Stator 6...Rotor 7...Pump shaft 8...Pump impeller 9... Diffuser 10... Outer tube 11... Inner tube 12... Stretch dupe 13... 7 Lange 14... Flange 15... Purge water introduction pipe 16... Auxiliary blade (8733) Agent Patent Attorney Yoshiaki Inomata (Baka
1 person) Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] (1) A pump nozzle is formed in the reactor pressure vessel, a pump impeller for coolant circulation is attached to the upper end of the pump shaft that is inserted into the pump casing attached to this pump nozzle, and this pump impeller is connected to the outer cylinder and inner cylinder. 1. An internal pump housed in a cylindrical diffuser to allow purge water to flow between a pump casing and a pump shaft, characterized in that an auxiliary vane is formed at the lower end of the pump impeller.