JP4051349B2 - Control rod drive mechanism - Google Patents

Description

  The present invention relates to an electric improved control rod drive mechanism (FMCRD) provided in an improved boiling water reactor (ABWR), and more particularly to a cyclo reducer that is provided with a cyclo reducer as a reduction mechanism. The present invention relates to a control rod drive mechanism that prevents deformation and breakage of the oil seal.

  The improved boiling water reactor (ABWR) has improved safety and reliability as a development goal, and adopts an improved control rod drive mechanism (FMCRD) as one of the achievement means. Yes. This improved control rod drive mechanism is designed to have a backup function of the hydraulic mechanism and eliminate the need for a scram discharge system. Specifically, the operation at the time of normal control is performed by electric drive, and at the time of scram, it is of a hydraulic drive type.

  FIG. 6 shows the cross-sectional structure of the reactor building (RCCV) in the improved boiling water reactor and the arrangement of the reactor pressure vessel (RPV) and the improved control rod drive mechanism. As shown in FIG. 6, in the improved boiling water reactor, the reactor containment vessel 1 is made of reinforced concrete, the reactor pressure vessel 2 is installed therein, and the dry well 3 is disposed below the reactor pressure vessel 2. Is formed. A fuel assembly 4 is loaded into the reactor pressure vessel 2 to form a core, and a control rod 5 for controlling the core output is inserted into the reactor pressure vessel 2 from below to drive the control rod 4. The improved control rod drive mechanism 6 is disposed in the lower dry well 3 below the reactor pressure vessel 2.

  FIG. 7 shows the reactor pressure vessel 2 of the improved boiling water reactor in an enlarged manner, and FIG. 8 shows the improved control rod drive mechanism 6 in an enlarged manner. As shown in these drawings, the improved control rod drive mechanism 6 includes a motor unit 7, a spool piece 8, and a drive mechanism main body 9 disposed at the lower end of the reactor pressure vessel 2.

  The motor unit 7 includes an electric motor 10 and a speed reduction mechanism 11, and a vertical rotation shaft 11 c connected to the speed reduction shaft 11 a of the speed reduction mechanism 11 via a slip clutch 11 b is connected to the upper vertical drive shaft by a gear coupling 12. 13. A ball screw 14 is connected to the drive shaft 13 so as to be integrally rotatable, and a ball nut 15 is screwed to the ball screw 14 so that the ball screw 14 is moved up and down by the rotation of the ball screw 14.

  The outer periphery of the ball nut 15 is provided with a pair of rollers 16 in the vertical position, and these rollers 16 are attached so as to support an axial mounting plate 18 formed on the inner peripheral surface of the guide tube 17. It has been. A hollow piston 19 surrounding the ball screw 14 and extending upward is provided at the upper part of the ball nut 15, and the control rod 4 is connected to the upper end of the hollow piston 19 via a coupling 19 a.

  An electromagnetic brake 20 is attached to the electric motor 10, and the electric motor 10 can be stopped by operating the electromagnetic brake 20. In addition, a synchro position detector 21 is provided, and the synchro position detector 21 can detect the position of the control rod 4.

  The electric motor 10, the electromagnetic brake 20, and the synchro position detector 21 are connected to the spool piece 8 by a cylindrical motor bracket 22 disposed around the gear coupling 12. A gland packing is used as a seal member at a position where the drive shaft 13 penetrates at a position above the motor bracket 22. Other stationary seals use rubber O-rings.

  A control rod drive mechanism housing (CRD housing) 23 penetrating the furnace wall in an arrangement surrounding the ball screw 14, the hollow piston 19 and the guide tube 17, an outer tube 24 provided at the lower portion of the CRD housing 23, and the outer tube The spool piece 8 provided at the lower part of 24 is fixed with the same bolt 25 for all three members.

  During operation, the electric motor 10 is rotationally driven to rotate the ball screw 14 via the rotating shaft 11 c and the driving shaft 13, and the ball nut 15 is moved up and down by the rotation of the ball screw 14. At that time, the rotation of the ball nut 15 is restricted by the mounting plate 18 via the roller 16 and moves up and down. In conjunction with the vertical movement of the ball nut 15, the hollow piston 19 and the control rod 4 move up and down, and the vertical movement of the control rod 14 regulates the amount of insertion and withdrawal into the core and controls the furnace output.

  By the way, in the early improved boiling water reactor, a step motor is applied as the electric motor 10 of the motor unit 7 and a gear mechanism is applied as the speed reduction mechanism. On the other hand, in recent years, it has been proposed and implemented to employ an induction motor as the motor 10 and a cyclo reducer as the speed reduction mechanism (see, for example, Patent Document 1).

  FIG. 9 is a partially enlarged cross-sectional view of the conventional structure of the cyclo reducer. As shown in FIG. 9, the cyclo reducer 26 includes an eccentric 29 that engages a high speed shaft 27 connected to the output shaft 10a of the electric motor 10 and a low speed shaft 28 connected to the reduction shaft 11a. And a planetary gear type structure that is decelerated by the curved plate 30.

  That is, the high-speed shaft 27 and the low-speed shaft 28 are coaxially arranged and covered with the inner cover 31 and the outside cover 32, respectively, and the high-speed shaft 27 and the low-speed shaft 28 are ball bearings inside the covers 31 and 32, respectively. It is rotatably supported via bearings 33 and 34 such as. The covers 31 and 32 are connected by a bolt 35.

  The eccentric body 29 is a disc-like member fitted on the outer peripheral side of the high-speed shaft 27 and locked by the key 36, and rotates integrally with the high-speed shaft 29 to have a sun gear function. The curved plate 30 is a member having a planetary gear function disposed in a large-diameter cylindrical portion provided on the low-speed shaft 28, and is engaged with an outer peripheral edge of the knitted core body 29 via a roller bearing 37. The rotation of the high speed shaft 27 is decelerated by the pin 38 and the outer pin 39 and transmitted to the low speed shaft 28 side as a reverse rotation.

  Lubricants such as grease are filled in the internal space 40 of the cyclo reducer 26 provided with the speed reduction mechanism constituted by the knitted core plate 29 and the curved plate 30. In order to prevent leakage of the lubricant, an upper oil seal 41 and a lower oil seal 42 are provided between the upper portion of the outside cover 32 and the low speed shaft 28 and between the lower portion of the inner cover 31 and the high speed shaft 27, respectively. Thus, it is shielded from the vertical direction as a closed space from the surrounding external environment.

Lubricant filling ports 43 and 44 for filling grease or the like into the internal space 40 from the outside at the speed reduction mechanism upper side position on the side wall of the outer cover 32 and the speed reduction mechanism lower side position on the side wall of the inner cover 31. Are formed through each side wall. The lubricating oil filling ports 43 and 44 are fitted with lubricating oil filling plugs 45 and 46 such as hexagonal taper screw plugs, for example, and the internal space 40 is sealed after the lubricant filling.
Japanese Patent Laid-Open No. 10-274688 (specification and FIGS. 1 and 2)

  The reactor containment vessel 1 is subjected to a pressure resistance / leakage test (RCCV pressure resistance / leakage test) during periodic inspections and the like. In the RCCV withstand pressure / leakage test, the reactor containment vessel 1 is filled with nitrogen gas having a pressure higher than normal pressure. In the RCCV withstand pressure / leakage test, the lower dry well 3 provided with the improved control rod drive mechanism 31 is also subjected to a pressure history during the withstand pressure / leakage test.

  According to the investigation by the inventors, the pressure history in the lower dry well 3 causes the oil seals 41 and 42 in the cyclo reducer 26 of the improved control rod drive mechanism to be deformed, displaced, or damaged, thereby causing a drive failure. Has been found to be possible.

  This point will be described with reference to FIGS. FIG. 10 is an enlarged view of the lower oil seal 42 (“A” portion) shown in FIG. 9. The oil seal 42 has a structure in which an upward tongue piece 42b is integrally formed along the inner peripheral side lower edge of the ring-shaped base portion 42a, and the ring-shaped base portion 42a is formed on the inner cover 31 of the cyclo reducer 26. An upward tongue piece 42 b is fixedly supported on the inner surface side and is in contact with the outer peripheral surface of the high-speed shaft 27.

  As a result, when the internal space 40 side (the upper side in FIG. 10) becomes high pressure, the tongue piece 42b comes into pressure contact with the high-speed shaft 27 side, thereby enhancing the sealing function. As shown by the arrow a, it is returned to the inner space 40 side and hardly leaks to the outer side (lower dry well 3 side).

  On the other hand, when the external side (lower dry well 3 side) is at a high pressure, the tongue piece 42b is easily deformed to the upper outer diameter side, so that it is easily separated from the high speed shaft 27 and the sealing function is lowered. As shown by the arrow b, the gas enters the inner space 40 side. The same applies to the case of the upper oil seal 41 shown in FIG.

  As a result, the oil seals 41 and 42 have a pressure holding ability to some extent with respect to the internal pressure, but do not have a holding ability with respect to the external pressure. Therefore, as shown in FIG. Under the external pressure environment, as shown by the arrow b, high pressure nitrogen gas enters the cyclo reducer 26 as the external pressure increases, and the internal pressure increases.

  Then, as shown in FIG. 11B, in the state where the internal pressure of the cyclo reducer 26 is increased to be equal to the external pressure, the internal / external gas movement is stopped and becomes a stable state.

  At the time of pressure reduction after the RCCV withstand pressure / leakage test, as shown by an arrow a in FIG. 11C, the internal pressure is held by an oil seal, and the residual pressure is reduced to the oil as the external pressure is reduced. Acts as a load corresponding to the differential pressure on the seal. If this load exceeds the holding force of the oil seal, the oil seal may be displaced, causing interference, which may result in inability to drive.

  As described above, when the cyclo reducer is applied as the motor unit speed reduction mechanism of the improved control rod drive mechanism, a drive failure due to deformation or displacement of the oil seal portion occurs during the pressure resistance and leakage test of the reactor containment vessel (RCCV). there is a possibility.

  The present invention has been made in view of such circumstances, and can control the internal pressure and the external environment of the cyclo reducer to be uniform, and can prevent drive failure due to deformation or misalignment of the oil seal portion. An object is to provide a rod drive mechanism.

  In order to achieve the above object, in the invention according to claim 1, the reactivity of the reactor is provided by raising and lowering the control rod provided at the lower part of the reactor pressure vessel of the improved boiling water reactor (ABWR). An improved control rod drive mechanism (FMCRD) for controlling the motor, wherein an induction motor is provided as a drive source and a cyclo reducer is provided as a reduction mechanism for the induction motor. Provided is a control rod drive mechanism characterized in that the speed reducer is provided with pressure equalizing means capable of equalizing internal pressure and external pressure.

  The invention according to claim 2 provides a control rod drive mechanism characterized in that the pressure equalizing means of the cyclo reducer is an opening that communicates the inside and outside of the cyclo reducer.

  According to a third aspect of the present invention, there is provided a control rod drive mechanism characterized in that the opening is provided in a lubricant filling plug of the cyclo reducer.

  According to a fourth aspect of the present invention, there is provided a control rod drive mechanism characterized in that the pressure equalizing means of the cyclo reducer is a relief valve provided in the cyclo reducer and capable of discharging the internal pressure to the outside.

  According to a fifth aspect of the present invention, there is provided a control rod drive mechanism, wherein the relief valve is provided in a pipe that communicates the inside and outside of the cyclo reducer.

  With the above configuration, the pressure in the cyclo reducer can avoid the influence of the use environment, that is, the external pressure, and good driving characteristics can be obtained. That is, according to the present invention, there is no residual pressure in the cyclo reducer at the time of pressure reduction after the RCCV pressure resistance / leakage test, and no load is generated on the oil seal. Therefore, the oil seal is not displaced due to the pressure difference between the inside and outside, and no interference occurs and the drive is not disabled. Thus, the pressure in the cyclo reducer can avoid the influence of the use environment, that is, the external pressure, and good driving characteristics can be obtained.

  Hereinafter, an embodiment of a control rod drive mechanism (an improved control rod drive mechanism (FMCRD)) according to the present invention will be described with reference to FIGS.

  FIG. 1 is a sectional view showing a configuration of a cyclo reducer of a control rod drive mechanism according to an embodiment of the present invention, and FIG. 2 is an overall configuration diagram of an electric unit including the cyclo reducer. 3 and 4 are explanatory diagrams of operation. In addition, these figures attach | subject the code | symbol common with FIGS. 6-11 demonstrated as a prior art example, and the description which overlaps with a prior art example is abbreviate | omitted. 6 to 8 are also referred to the description of the embodiment of the present invention.

  As shown in FIGS. 1, 2, and 6 to 8, the control rod drive mechanism 6 of the present embodiment is provided at the lower part of the reactor pressure vessel 2 of the improved boiling water reactor (ABWR) and controlled. This is an improved control rod drive mechanism that controls the reactivity of the nuclear reactor by moving the rod 4 up and down. The control rod drive mechanism 6 is an electric control rod drive mechanism provided with an induction motor 10 as a drive source and a cyclo reducer 26 as a speed reduction mechanism 11 of the induction motor 10.

  The cyclo reducer 26 is a planetary gear that decelerates a high-speed shaft 27 connected to the output shaft 10a of the electric motor 10 and a low-speed shaft 28 connected to the reduction shaft 11a by an eccentric body 29 and a curved plate 30 engaged with them. It has a gear type configuration.

  That is, the high-speed shaft 27 and the low-speed shaft 28 are coaxially arranged and covered with the inner cover 31 and the outside cover 32, respectively, and the high-speed shaft 27 and the low-speed shaft 28 are ball bearings inside the covers 31 and 32, respectively. It is rotatably supported via bearings 33 and 34 such as. The covers 31 and 32 are connected by a bolt 35.

  The eccentric body 29 is a disc-like member fitted on the outer peripheral side of the high-speed shaft 27 and locked by the key 36, and rotates integrally with the high-speed shaft 29 to have a sun gear function. The curved plate 30 is a member having a planetary gear function disposed in a large-diameter cylindrical portion provided on the low-speed shaft 28, and is engaged with an outer peripheral edge of the knitted core body 29 via a roller bearing 37. The rotation of the high speed shaft 27 is decelerated by the pin 38 and the outer pin 39 and transmitted to the low speed shaft 28 side as a reverse rotation.

  Lubricants such as grease are filled in the internal space 40 of the cyclo reducer 26 provided with the speed reduction mechanism constituted by the knitted core plate 29 and the curved plate 30. In order to prevent leakage of the lubricant, an upper oil seal 41 and a lower oil seal 42 are provided between the upper portion of the outside cover 32 and the low speed shaft 28 and between the lower portion of the inner cover 31 and the high speed shaft 27, respectively. It is shielded from above and below as a closed space from the surrounding external environment.

  Lubricant filling ports 43 and 44 for filling grease or the like into the internal space 40 from the outside at the speed reduction mechanism upper side position on the side wall of the outer cover 32 and the speed reduction mechanism lower side position on the side wall of the inner cover 31. Are formed through each side wall. The lubricating oil filling ports 43 and 44 are fitted with lubricating oil filling plugs 45 and 46 such as hexagonal taper screw plugs, for example, and the internal space 40 is sealed after the lubricant filling.

  In the present embodiment, the cyclo-speed reducer 26 having such a configuration is provided with a pressure equalizing means 50 capable of equalizing the internal pressure and the external pressure, that is, the pressure in the internal space 40 and the pressure in the lower dry well 3. . The pressure equalizing means 50 is formed as an opening 51 that communicates the inside and outside of the cyclo reducer 26. The opening 51 can be formed as a through hole at various locations in the inner cover 31 and the outer cover 32 that do not cause leakage of grease or the like to the cyclo reducer.

  In the present embodiment, the position where the opening 51 is formed is set as follows from the viewpoint of the pressure equalizing effect in the cyclo reducer 26 and the effect of preventing the outflow of grease and the like.

  That is, the opening 51 of the present embodiment has a hexagonal shape at the center of the lubricant filling plug 45 provided on the upper side of the outside cover 32 of the cyclo reducer 26, as shown in an enlarged view in FIG. It is provided as a small-diameter through hole drilled in communication with the hole. Thereby, the hexagonal taper screw plug for normal lubricant filling is configured as a pressure equalizing plug having the opening 51. The opening 51 formed in the center of the lubricant filling plug 45 can communicate with the inside and outside without causing leakage of grease or the like to the cyclo reducer and function as an opening for equalizing pressure.

  In addition, it was confirmed by the drive test, the environmental simulation test (pressure simulation test, temperature simulation test), etc. that the opening 51 satisfies the pressure equalizing function at φ2 mm. It was also confirmed that no leakage of grease or the like occurred.

  This test will be described with reference to FIG. FIG. 4 is a characteristic diagram showing the pressure history in the lower dry well 3 and the influence on the pressure in the internal space 40 of the cyclo reducer 26 according to the present embodiment in the RCCV withstand pressure / leakage test. Pressure and time are shown on the horizontal axis. As indicated by a solid line “A” as a characteristic line in FIG. 4, the test pressure was gradually increased with the passage of time, and after reaching a constant high pressure through a constant pressure portion every predetermined time, the test pressure was gradually decreased.

  In this case, as described with reference to FIGS. 10 and 11 as a conventional example, when the internal space 40 of the cyclo reducer 26 is a sealed space, the internal space 40 is affected by the pressure history in the lower dry well 3. As shown in the phantom line “B” in FIG. 4, even if the pressure in the lower dry well 3 is lowered after that, the internal space increases as the pressure increases along the characteristic line (solid line “A”) in FIG. There was almost no discharge of pressurized gas from 40, and the high pressure state was maintained.

  On the other hand, in the present embodiment, the opening 51 is formed as a small-diameter through hole drilled in the center of the lubricant filling plug 45 in communication with the hexagonal hole. As shown, gas can flow between the internal space 40 of the cyclo reducer 26 and the dry well 3, and the pressure in the internal space 40 decreases with a decrease in pressure in the lower dry well 3. That is, along the characteristic line “A” in FIG. 4, the pressure in the internal space 40 and the pressure in the lower dry well 3 that is outside thereof are equalized, and the soundness of the oil seals 41 and 42 is maintained. Was confirmed.

  That is, according to the present embodiment, there is no residual pressure in the cyclo reducer 26 during pressure reduction after the RCCV pressure resistance / leakage test, and no load is generated on the oil seals 41 and 42. Therefore, the oil seal is not displaced due to the pressure difference between the inside and outside, and no interference occurs and the drive is not disabled. Thus, according to this embodiment, the influence of the use environment on the pressure in the cyclo reducer, that is, the influence of the external pressure can be avoided, and good drive characteristics can be obtained.

  Moreover, in the present embodiment, it has been confirmed that the internal and external pressures can be equalized without leaking the internal lubricant. Even if the lubricant leaks, the pressure equalizing plug 45 installed in the cyclo reducer 26 is in the gear unit, and the leakage remains in the gear unit, so that other components are not affected. Absent.

  FIG. 5 shows another embodiment of the present invention. As shown in FIG. 5, in another embodiment, the pressure equalizing means 50 of the cyclo reducer 26 is configured as a relief valve 52 that is provided in the cyclo reducer 26 and can discharge the internal pressure of the internal space 40 to the outside. Has been.

  The relief valve 52 is provided in a pipe 53 that communicates the inside and outside of the cyclo reducer 26. That is, the pipe 53 is attached in place of the plug 46 provided on the inner cover 31 side of the cyclo reducer 26. The tube 53 rises, for example, in an L shape, and its upper end is disposed at a predetermined height position corresponding to the internal space 40. A relief valve 52 is provided at the upper end of the pipe 53.

  Even in such other embodiments, since the internal pressure of the cyclo reducer 26 is released via the relief valve 52 at the time of pressure reduction after the RCCV pressure resistance / leakage test, the influence of the residual pressure can be prevented, and the oil seal 41 , 42 does not generate a load. As a result, as in the first embodiment, the oil seal is not displaced due to the pressure difference between the inside and outside, interference is not caused, and driving is not disabled. Therefore, according to other embodiments, the influence of the use environment, that is, the external pressure can be avoided with respect to the pressure in the cyclo reducer, and good driving characteristics can be obtained.

  Moreover, in another embodiment, the relief valve 52 is provided at the upper end portion of the pipe 53 that rises to a predetermined height as the pressure equalizing means 50, so that it is possible to reliably prevent the lubricant from leaking from the internal space 40.

  In addition, about the structure of the relief valve 52, an installation position, etc., it is not limited to what was shown in FIG. 5, It is possible to set to another location.

The expanded sectional view which shows the cyclo reducer of one Embodiment of the control-rod drive mechanism concerning this invention. The fragmentary sectional view which shows the motor unit provided with the cyclo reducer shown in FIG. The partial expanded sectional view for demonstrating the structure and effect | action of one Embodiment of this invention. The characteristic diagram for demonstrating the effect | action of one Embodiment of this invention. The expanded sectional view which shows the cyclo reducer of other embodiment of the control-rod drive mechanism which concerns on this invention. Overall view showing the vertical and structure of the improved boiling water reactor. Sectional drawing which shows the reactor pressure vessel structure of an improved boiling water reactor. The expanded sectional view which shows the structure of an improved control rod drive mechanism. The expanded sectional view which shows the structure of the cyclo reducer in the conventional control rod drive mechanism. The expanded sectional view for demonstrating the effect | action by the conventional example of a cyclo reducer. (A), (B), (C) is explanatory drawing about the internal pressurization by the conventional example of a cyclo reducer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor containment vessel 2 Reactor pressure vessel 3 Dry well 4 Fuel assembly 5 Control rod 6 Improved control rod drive mechanism 7 Motor unit 8 Spool piece 9 Drive mechanism body 10 Electric motor 10a Output shaft 11 Deceleration mechanism 11a Deceleration shaft 11b Slip Clutch 11c Rotating shaft 12 Gear coupling 13 Drive shaft 14 Ball screw 15 Ball nut 16 Roller 17 Guide tube 18 Mounting plate 19 Hollow piston 19a Coupling 20 Electromagnetic brake 21 Synchro position detector 22 Motor bracket 23 Control rod drive mechanism housing 24 Outer Tube 25 Bolt 26 Cyclo reducer 27 High speed shaft 28 Low speed shaft 29 Eccentric body 30 Curved plate 31 Inner cover 32 Outside cover 33, 34 Bearing 35 Bolt 36 Key 37 Roller bearing 38 Inner pin 39 Outer pin 40 Inner space 41 Upper oil seal Le 42 lower oil seal 42b tongues 43,44 lubricant filling ports 45 and 46 lubricating oil filler plug 50 pressure equalizing means 51 opening 52 a relief valve 53 tube

Claims (5)

A control rod drive mechanism that is provided at the bottom of the reactor pressure vessel of a boiling water reactor and controls the reactivity of the reactor by raising and lowering the control rod, and includes an induction motor as a drive source, and this induction An electric control rod drive mechanism provided with a cyclo reducer as a reduction mechanism for an electric motor, wherein the cyclo reducer is provided with pressure equalizing means capable of equalizing internal pressure and external pressure. Drive mechanism. 2. The control rod drive mechanism according to claim 1, wherein the pressure equalizing means of the cyclo reducer is an opening that communicates the inside and outside of the cyclo reducer. 3. The control rod drive mechanism according to claim 2, wherein the opening is provided in a lubricant filling plug of the cyclo reducer. 2. The control rod drive mechanism according to claim 1, wherein the pressure equalizing means of the cyclo reducer is a relief valve provided in the cyclo reducer and capable of discharging internal pressure to the outside. 5. The control rod drive mechanism according to claim 4, wherein the relief valve is provided in a pipe that communicates the inside and outside of the cyclo reducer.

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