JPH05248490A - Vibration control device for internal pump - Google Patents

Abstract

PURPOSE:To suppress vibration, generated owing to operation of an internal pump and an earthquake, to a low value by arranging an additional inertial weight in a container through a bearing and connecting conduction plates, nipped between electromagnets, to the two ends of the additional inertia weight. CONSTITUTION:An internal pump 5 used as an in-pile re-circulating pump in an advanced boiling water type reactor is mounted in a through-hole 1a formed in the lower edge 1c of a reactor pressure vessel 1. A damping device 8 mounted on the lower edge of the pump 5 is formed such that bearings 13 are located to the inner upper and lower parts of a flat container 16 and an additional inertia weight 11 is arranged. and a pair of conduction plates 12 are connected to both sides of the additional inertial weight 11. The conduction plates 12 are supported in a manner to be nipped between electromagnets 9 arranged to the inner upper and lower parts on both sides of the container 16. The additional inertia 11 and the electromagnets 9 are interconnected through support springs 10 and the additional inertial weight 11 is supported in the container 16 through upper and lower bearings 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping device for an internal pump which is incorporated in a reactor pressure vessel of a boiling water nuclear power plant and forcibly circulates cooling water.

[0002]

2. Description of the Related Art An improved boiling water reactor uses an internal pump as a reactor recirculation pump, which requires a propeller and its shaft, a diffuser, a stretch tube, a motor and a motor case. There is. That is, as shown in FIG. 5, the internal pump 5 is attached to the through hole 1a provided in the lower mirror 1c of the reactor pressure vessel 1. In FIG. 5, reference numeral 2
Is a core, 3 is a separator, and 4 is a control rod.

As described above, the internal pump 5 is a main device of the primary system directly incorporated in the reactor pressure vessel 1, and further has a rotating part built therein. Therefore, it is indispensable to reduce the vibration caused by the operation or the deformation caused by the external force such as earthquake in order to improve the reliability and safety of the nuclear reactor.

As a conventional vibration isolator for the internal pump 5, as shown in FIG. 6, a lower mirror 1 of a reactor pressure vessel 1 is used.
It is generally known that the lower end of the motor case 5a of the internal pump 5 is connected to the pressure wall 7 via the shock absorber 6 such as a snubber in the nozzle 1b mounted in the through hole 1a provided in c. ..

[0005]

In the vibration isolator of this type, the reactor pressure vessel 1 becomes hot between the motor case 5a attached to the reactor pressure vessel lower mirror 1c and the reaction wall 7. Along with this, relative mutations due to heat and internal pressure occur, so it is necessary to have a structure that allows this to be eliminated. Since the shock absorber 6 needs a function of restraining the motor case 5a against both minute vibrations caused by the operation of the internal pump 5 and large displacements during an earthquake, the structure becomes extremely complicated and large. There are challenges.

Further, in order to cope with the arbitrariness of the direction of vibration or seismic motion, it is necessary to support the motor case 5a from at least two directions in the horizontal section. However, if the lower mirror 1c of the reactor pressure vessel 1 is provided with bidirectional support for each of the internal pumps that are normally installed in 8 to 10 units, the occupied space becomes enormous and the reactor pressure vessel 1 Not only does this result in an increase in the space underneath 1, but there is also a problem that it affects the accessibility to heat exchangers and the like installed near the support.

The present invention has been made to solve the above problems, and suppresses the vibration of the internal pump during normal operation, and reduces the seismic response so that the internal pump can operate without loss of its function during an earthquake. In addition, it is possible to improve safety, reliability, and economic efficiency, and to provide a vibration damping device for an internal pump that can improve accessibility and workability to the lower part of the reactor pressure vessel. It is in.

[0008]

According to the present invention, an additional inertia weight is arranged in a container through a bearing, and conductive plates are connected to both ends of the additional inertia weight, and the conductive plate is sandwiched by an electromagnet. A supporting spring is interposed and connected between the additional inertia weight and the electromagnet.

[0009]

Function: An inertia weight of about several% of the weight of the internal pump is added to the lower part of the motor case. This weight is vibrated with a relatively large damping at a frequency close to the natural frequency of the internal pump and the frequency related to the rotation of the pump rotor, thereby suppressing the vibration of the corresponding frequency component of the internal pump. To do. The magnetic force of the magnet is used as the vibration damping force of the additional inertia weight.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vibration damping device for an internal pump according to the present invention will be described with reference to FIGS. 1 shows an internal pump having a vibration damping device according to the present invention, FIG. 2 is a plan view showing the vibration damping device 8 in FIG. 1, and FIG. 3 is a sectional view taken along the line AA of FIG. FIG. 4 is a longitudinal sectional view and FIG. 4 is a characteristic curve diagram for explaining the effect of the present invention. In the figure, the same parts as those in FIGS. 5 and 6 are designated by the same reference numerals and the description of the overlapping parts will be omitted.

In FIG. 1, a vibration damping device 8 is attached to the lower end of a motor case 5a of the internal pump 5. The vibration damping device 8 has the structure shown in FIGS. That is, the bearing 13 is placed in the flat container 16.
An additional inertial weight 11 is arranged with the above and below interposed therebetween, and a pair of conductive plates 12 are connected to both sides of this additional inertial weight 11. The pair of electrically conductive plates 12 are sandwiched between the electromagnets 9
Are arranged in the upper and lower parts of the container 16 over the left and right, and the additional inertia weight 11 and the electromagnet 9 are connected via the support spring 10.

A mounting member 15 is connected to the upper end of the container 16, and a fastening bolt 14 is passed through the mounting member 15 to the lower end portion of the motor case 5a to suppress the vibration.
Attach. The additional inertia weight 11 has a weight of about several percent of the internal pump 5.

As is apparent from FIGS. 2 and 3, the additional inertia weight 11 is housed in the container 16 of the vibration isolator 8 via the upper and lower bearings 13. A conductive plate 12 made of, for example, a copper plate is attached to the additional inertia weight 11 at every 90 degrees. The conductive plate 12 is supported by a support spring 10 from the upper and lower portions of each of the four electromagnets 9. Further, the conductive plate 12 is sandwiched between the electromagnets 9 from above and below, and in accordance with the movement of the additional inertia weight 11 during an earthquake or the operation of the internal pump 5,
The electromagnet 9 generates an electromotive force when moving in a magnetic field, absorbs vibration energy, and attenuates vibration. Therefore, if the spring constant of the support spring 10 is adjusted to approach the primary natural frequency of the internal pump (for example, 8 Hz), the primary resonance vibration generated by the operation of the internal pump or an earthquake can be suppressed to a low level. ..

FIG. 4 is a diagram showing the effect of this embodiment, showing the vibration characteristics when only the internal pump is used and the vibration characteristics when the additional system is attached. As is clear from FIG. 4, in the case of only the internal pump shown in the curve A, the response magnification with respect to the frequency increases, but the curves B and C
As shown in (4), by selecting the damping constant of the additional system to be small or appropriate, it is possible to reduce the response magnification and stabilize, and to relax the stress generated in the internal pump 5.

In the above embodiment, instead of the electromagnet 9 and the support spring 10, a magnetic bearing having these functions is used to control the spring constant, thereby suppressing any frequency component of the internal pump. be able to.

Although FIG. 2 shows an example in which a four-pole electromagnet is provided, the directivity of vibration can be flattened by increasing the number to eight times or more. Further, when the electromotive force generated in the conductive plate 12 is applied to the status display or the like, the damping effect is improved.

Therefore, according to the above-mentioned embodiment, it is possible to suppress the vibration generated by the operation of the internal pump, the earthquake, etc., and reduce the generated stress. Moreover, since there is no support such as a snubber as in the conventional case, the lower part of the internal pump can be widened, the accessibility is good, and the workability is improved.

[0018]

According to the present invention, the vibration generated by the operation of the internal pump, the earthquake, etc. can be suppressed to a low level, and the generated stress can be relieved. At times, it is possible to suppress the internal pump to a low level vibration. Further, it is possible to improve accessibility and workability near the lower portion of the reactor pressure vessel.

[Brief description of drawings]

FIG. 1 is a schematic view of an internal pump equipped with a vibration damping device according to the present invention.

FIG. 2 is a plan view showing the vibration damping device in FIG.

FIG. 3 is a longitudinal sectional view schematically showing a section taken along the line AA in FIG.

FIG. 4 is a characteristic curve diagram for explaining the effect of the present invention.

FIG. 5 is a vertical sectional view schematically showing the inside of a reactor pressure vessel of a boiling water reactor.

FIG. 6 is a schematic view showing an internal pump equipped with a conventional vibration damping device.

[Explanation of symbols]

1 ... Reactor pressure vessel, 1a ... Through hole, 1b ... Nozzle, 1
c ... lower mirror, 2 ... core, 3 ... separator, 4 ... control rod, 5
... internal pump, 5a ... motor case, 6 ... shock absorber, 7 ... reaction wall, 8 ... vibration damping device, 9 ... electromagnet, 10 ...
Support spring, 11 ... Additional inertia weight, 12 ... Conductive plate, 13 ... Bearing, 14 ... Tightening bolt, 15 ... Mounting member, 16 ... Container.

Claims (1)

[Claims] 1. An additional inertia weight is arranged in a container via a bearing, and conductive plates are connected to both ends of the additional inertia weight. The conductive plates are sandwiched by electromagnets, and the additional inertia weight and the electromagnet. A vibration damping device for an internal pump, characterized in that a support spring is interposed between and connected to.