阅读说明：本技术 带有热管冷却的控制棒驱动机构 (Control rod drive mechanism with heat pipe cooling ) 是由 C·洛布沙伊德 D·诺艾尔 于 2018-12-21 设计创作，主要内容包括：用于核反应堆控制棒驱动机构(CRDM)的冷却系统包含位于该控制棒驱动机构内或附近的蒸发段以及流体地联接至所述蒸发段的冷凝段。所述冷却系统可以包含从所述控制棒驱动机构中的驱动线圈向上延伸的一组热翅片以及延伸穿过所述驱动线圈和热翅片的热管。流体在处于所述热管的蒸发段中时由于所述控制棒驱动机构所生成的热量而蒸发并且从所述蒸发段运动至所述热翅片中的冷凝段中。流体在处于所述冷凝段中时冷却并且冷凝,从而再循环返回至所述蒸发段中。该被动自然循环冷却系统减少或消除通常用于冷却控制棒驱动机构的水软管、管道以及其它水泵送设备的数量,或者减少或消除对空气冷却的需求,从而增加核反应堆的可靠性并且简化核反应堆的运行和维护。(A cooling system for a nuclear reactor Control Rod Drive Mechanism (CRDM) includes an evaporator section located within or proximate to the CRDM and a condenser section fluidly coupled to the evaporator section. The cooling system may include a set of heat fins extending upwardly from a drive coil in the control rod drive mechanism and heat pipes extending through the drive coil and heat fins. Fluid evaporates while in the evaporator section of the heat pipe due to heat generated by the control rod drive mechanism and moves from the evaporator section into the condenser section in the heat fin. The fluid cools and condenses while in the condenser section, thereby being recycled back into the evaporator section. The passive natural circulation cooling system reduces or eliminates the number of water hoses, pipes and other water pumping equipment typically used to cool control rod drive mechanisms, or the need for air cooling, thereby increasing the reliability of the nuclear reactor and simplifying the operation and maintenance of the nuclear reactor.)

1. A cooling system for a nuclear reactor Control Rod Drive Mechanism (CRDM), comprising:

an evaporator section located within or adjacent to the control rod drive mechanism;

a condenser section fluidly coupled to the evaporator section; and

a fluid configured to:

while in the evaporator section, due to heat generated by the control rod drive mechanism, evaporates and flows from the evaporator section into the condenser section, and

condense and recirculate back into the evaporator section while in the condenser section after moving away from the control rod drive mechanism.

2. The cooling system of claim 1, comprising: a set of heat fins extending upwardly from a drive coil in the control rod drive mechanism, the evaporator section extending through inner portions of the drive coil and heat fins and the condenser section extending through outer portions of the drive coil and heat fins.

3. The cooling system of claim 2, wherein the heat fins extend around a break coil configured to electromagnetically retain a break magnet in the control rod drive mechanism.

4. The cooling system, as set forth in claim 2, wherein the drive coil and the heat fin form an elongated annular shape around an annular drive shaft housing.

5. The cooling system of claim 2, comprising a heat pipe looped to extend through the drive coil and the heat fin.

6. The cooling system of claim 5, comprising insulation formed around an interior portion of the heat pipe located in the heat fin.

7. The cooling system of claim 6, comprising a condensation channel formed around an exterior of the heat pipe located in the heat fin.

8. The cooling system of claim 5, wherein the heat pipe extends from the control rod drive mechanism to an interior surface of a vessel housing the nuclear reactor or to a structure that conducts heat to an environment external to the vessel housing the nuclear reactor.

9. The cooling system of claim 1, wherein the crdm comprises:

a drive coil positioned about an outer surface of the drive shaft housing;

a drive magnet located around an inner surface of the drive shaft housing;

a drive shaft connected to the drive magnet at a top end and to a core control rod assembly at a bottom end,

wherein activating the drive coils lifts the drive magnets thereby raising the drive shaft and nuclear control rod assembly, and the cooling system removes heat generated by the drive coils as the drive shaft and nuclear control rod assembly are lifted.

10. A cooling system for a nuclear reactor Control Rod Drive Mechanism (CRDM); the method comprises the following steps:

a drive shaft housing extending upwardly from a top end of a nuclear reactor pressure vessel;

a drive shaft having a top end extending into the drive shaft housing and a bottom end coupled to a control rod assembly located at a bottom end of the nuclear reactor pressure vessel;

a drive mechanism coupled to the drive shaft housing, the drive mechanism configured to linearly move the drive shaft and raise and lower the control rod assembly;

a heat pipe located in or near the drive mechanism; and

a fluid located in the heat pipe, the fluid configured to circulate through the heat pipe via evaporation and condensation to remove heat from the drive mechanism.

11. The cooling system of claim 10, comprising a heat fin extending upwardly from the drive mechanism, wherein the heat pipe extends through the drive mechanism and the heat fin.

12. The cooling system of claim 11, comprising insulation at least partially surrounding an interior portion of the heat pipe extending through the heat fin.

13. The cooling system of claim 12, comprising a condensation channel at least partially surrounding an exterior of the heat pipe extending through the heat fin.

14. The cooling system, as set forth in claim 11, wherein the heat pipe extends upwardly through the drive mechanism and the heat fin and extends downwardly back through the heat fin and drive mechanism, forming a loop.

15. The cooling system of claim 11, wherein the heat fins extend vertically upward from the drive mechanism and radially outward from the drive shaft housing.

16. The cooling system of claim 10, comprising: a containment vessel at least partially enclosing the nuclear reactor pressure vessel, wherein the heat pipe extends outwardly from the drive mechanism to an inner surface of the containment vessel.

17. A system for cooling a Control Rod Drive Mechanism (CRDM) in a nuclear reactor, comprising:

a tube for containing a fluid, the tube comprising:

an evaporator section in or near the crdm, the fluid in the evaporator section configured to evaporate due to heat generated by the crdm; and

a condenser section fluidly coupled to the evaporator section, the condenser section configured to condense the evaporated fluid and circulate the condensed fluid back to the evaporator section by gravity or capillary action.

18. The system of claim 17, further comprising thermal fins extending outwardly from drive coils in the crdm, the tubes forming rings extending through the drive coils and the thermal fins.

19. The system of claim 18, wherein the evaporation section of the tube extends along an inner portion of the drive coils and an inner portion of the heat fins, and the condensation section of the tube extends along an outer portion of the drive coils and an outer portion of the heat fins.

20. The system of claim 19, comprising:

an insulation surrounding at least a portion of a tube extending along an interior portion of the heat fin; and

a condensing channel surrounding at least a portion of a tube extending along an outer portion of the heat fin.

Technical Field

The present disclosure generally relates to a cooling system for a nuclear reactor control rod drive mechanism.

Background

During fast control rod insertion (SCRAM), the Control Rod Drive Mechanism (CRDM) on top of the nuclear Reactor Pressure Vessel (RPV) may manipulate or release the drive shaft by gravity. The control rod drive mechanism may be located within an upper containment vessel (CNV) that houses the reactor pressure vessel, and an electric motor may be used to control the movement of the drive shaft. The electric motor may be driven remotely across the pressure vessel boundary by electromagnetic force.

The CRDM electric motors are typically cooled by Reactor Component Cooling Water Systems (RCCWS) or forced air Cooling. The water cooling system may contain a complex arrangement of water hoses to circulate water that removes heat from the electric motor coils. When the reactor pressure vessel is removed from the containment vessel to replenish the fuel, it is difficult to remove the hose. A control rod drive mechanism failure caused by a leak or blockage in the cooling System hoses may trigger a Containment Evacuation System (CES) to shut down the nuclear reactor. For some nuclear reactors, alternative air cooling systems may be inadequate. For example, the evacuated containment vessel creates a vacuum environment around the outside of the reactor pressure vessel, thereby eliminating convective heat transfer as a cooling option.

Drawings

The included drawings are for illustrative purposes and serve to provide examples of possible structures and operations of the disclosed inventive systems, apparatus, methods and computer-readable storage media. These drawings in no way limit any changes in form and detail that may be made by one skilled in the art without departing from the spirit and scope of the disclosed embodiments.

FIG. 1 illustrates a schematic diagram of an example nuclear reactor module.

FIG. 2 is a side perspective cut-away view of an upper head of a reactor pressure vessel having a Control Rod Drive Mechanism (CRDM) within the containment vessel.

FIG. 3 is a perspective view of a control rod assembly partially inserted into a nuclear fuel assembly.

Fig. 4A and 4B are schematic diagrams illustrating disassembly of a reactor pressure vessel.

FIG. 5 is a side view of a single hinge type control rod drive mechanism.

FIG. 6 is a plan view of a single hinge type control rod drive mechanism.

FIG. 7 is a side cross-sectional view of the control rod drive mechanism of FIG. 5.

FIG. 8 is a further enlarged detailed side cross-sectional view of the single hinge latch assembly within the control rod drive mechanism.

Fig. 9 is a cross-sectional plan view of the drive assembly.

Fig. 10 is a cross-sectional plan view of the single hinge latch assembly of fig. 8.

11A-11E illustrate cross-sectional side views of the single hinge type control rod drive mechanism of FIG. 5 in different operating states.

FIG. 12 is a side view of a dual-hinge type control rod drive mechanism.

Fig. 13A and 13B show cross-sectional side views of the dual-hinge type control rod drive mechanism of fig. 12 in different operating states.

FIG. 14 is an enlarged cross-sectional side view of the dual hinge latch assembly within the control rod drive mechanism of FIG. 12.

Fig. 15 is a cross-sectional plan view of the dual-hinge latch assembly of fig. 14.

Fig. 16A-16G are schematic diagrams illustrating the operating states of different control rod drive mechanisms (fig. 5 or 12), wherein,

fig. 16A-16B illustrate an exemplary process for engaging and linearly moving a drive shaft using a drive mechanism.

16C-16G illustrate an exemplary process for disengaging a drive shaft from a control rod assembly using a remote disconnect system.

FIG. 17 is a side perspective cross-sectional view of an upper head of a reactor pressure vessel within an upper receiving vessel, the upper head utilizing a control rod drive mechanism cooling system.

FIG. 18 is an isolated perspective view of the control rod drive mechanism cooling system.

FIG. 19 is a cross-sectional plan view of a lower section of the control rod drive mechanism cooling system.

FIG. 20 is a cross-sectional plan view of an upper section of the control rod drive mechanism cooling system.

FIG. 21 is an enlarged cross-sectional plan view of an upper section of the control rod drive mechanism cooling system.

FIG. 22 is an isometric side cross-sectional view of the control rod drive mechanism cooling system.

FIG. 23 is an enlarged isometric side cross-sectional view of the control rod drive mechanism cooling system.

Detailed Description

A simplified cooling system uses heat pipes to cool an electric motor in a Control Rod Drive Mechanism (CRDM) when operating in an evacuated containment vessel (CNV). The Cooling System does not rely on active Water Cooling by the Reactor Component Cooling Water System (RCCWS), and greatly simplifies the design of the control rod drive mechanism, containment vessel, and Reactor Component Cooling Water System, thereby avoiding potential Containment Evacuation System (CES) triggering and control rod drive mechanism failure due to accidental Cooling leaks or blockages.

The cooling system overcomes the cooling limitations of control rod drive mechanisms operating in a vacuum environment that prevents efficient convective heat transfer. The heat pipe may transfer heat from the control rod drive mechanism electrical coil to a finned heat exchanger located above the control rod drive mechanism electrical coil, thereby improving the ability to transfer heat by radiation through a vacuum to the surrounding vessel wall containing the vessel. The cooling system may comprise a housing of the same or larger diameter than the electrical coil and no external power or external fluid transfer is required. In an alternative option, the cold ends of the heat pipes may be mounted directly to the vessel wall of the containment vessel above the control rod drive mechanism to further facilitate conductive heat transfer.

Fig. 1 shows a cross-sectional view of an exemplary integrated reactor module 5 including a reactor pressure vessel 52. The reactor core 6 is shown positioned adjacent to the lower head 55 of the reactor pressure vessel 52. The reactor core 6 may be located in a shroud 22 that surrounds the reactor core 6 around the sides of the reactor core 6. The riser section 24 surrounded by the steam generator 30 is located above the reactor core 6.

As the primary coolant 28 is heated by the reactor core 6 due to a fission event, the primary coolant 28 may be directed upward from the shroud 22 into the annular space 23 above the reactor core 6 and out of the risers 24. This may cause additional primary coolant 28 to be drawn into the shroud 22, which in turn is heated by the reactor core 6, which draws more primary coolant 28 into the shroud 22. The primary coolant 28 emerging from the riser 24 may be cooled by the steam generator 30 and directed toward the outside of the reactor pressure vessel 52 and then returned to the bottom of the reactor pressure vessel 52 by natural circulation.

The primary coolant 28 circulates through the reactor core 6 to become the high temperature coolant TH and then continues upwardly through the riser section 24 where it is directed back down the annulus and cooled by the steam generator 30 to become the low temperature coolant TC. One or more Control Rod Drive Mechanisms (CRDMs) 10 are operably coupled to a plurality of drive shafts 20, which may be configured to engage a plurality of control rod assemblies 80 located above the reactor core 6.

The reactor pressure vessel baffle 45 may be configured to direct the primary coolant 28 toward a lower head 55 of the reactor pressure vessel 52. The surface of the reactor pressure vessel baffle 45 may directly contact and deflect the primary coolant 28 exiting the riser section 24. In certain examples, the reactor pressure vessel baffle 45 may be made of stainless steel or other materials.

The lower head 55 of the reactor pressure vessel 52 may include an elliptical, domed, concave, or hemispherical portion 55A, wherein the elliptical portion 55A directs the primary coolant 28 toward the reactor core 6. The elliptical portion 55A may increase the flow rate and promote the natural circulation of the primary coolant through the reactor core 6. Further optimization of the primary coolant 28 flow may be achieved by modifying the radius of curvature of the reactor pressure vessel baffles 45 to eliminate/minimize boundary layer separation and stagnation areas.

A reactor pressure vessel baffle 45 is shown between the top of the riser section 24 and the booster zone 40. The booster zone 40 is shown to include one or more heaters and spray nozzles configured to control pressure or maintain a steam dome within the upper end 56 or head of the reactor pressure vessel 52. Located in the reactor pressure vesselThe primary coolant 28 below the baffle 45 may include a relatively sub-cooled coolant T_SUBWhile the primary coolant 28 in the pressurizer zone 40 in the upper end 56 of the reactor pressure vessel 52 may include a substantially saturated coolant T_SAT。

The level of primary coolant 28 is shown above the reactor pressure vessel baffle 45 and within the booster zone 40 so that the entire volume between the reactor pressure vessel baffle 45 and the lower head 55 of the reactor pressure vessel 52 may be filled with primary coolant 28 during normal operation of the reactor module 5.

The shroud 22 may support one or more control rod guide tubes 94 for guiding control rod assemblies 80 that are inserted into or removed from the reactor core 6. In certain examples, the drive shaft 20 may pass through the reactor pressure vessel baffle 45 and the riser section 24 in order to control the position of the control rod assembly 80 relative to the reactor core 6.

The reactor pressure vessel 52 may include a flange by which the lower head 55 may be removably attached to an upper reactor vessel body 60 of the reactor pressure vessel 52. In certain examples, when the lower head 55 is separated from the upper reactor vessel body 60, such as during refueling operations, the riser sections 24, reactor pressure vessel baffles 45, and other internal portions may be retained within the upper reactor vessel body 60, while the reactor core 6 may be retained within the lower head 55.

In addition, the upper reactor vessel body 60 may be accommodated in the accommodating vessel 70. Any air or other gas present in the containment region 74 between the containment vessel 70 and the reactor pressure vessel 52 may be removed or evacuated prior to or during reactor startup. The gas evacuated or evacuated from the containment region 74 may include non-condensable gases and/or condensable gases. During emergency operation, vapor and/or steam may be vented from reactor pressure vessel 52 into containment region 74, or only a negligible amount of non-condensable gas (such as hydrogen) may be vented or released into containment region 74.

FIG. 2 illustrates an upper cross-sectional view of the reactor module 5 and an exemplary Control Rod Drive Mechanism (CRDM)10 assembly. The reactor module 5 may include an upper containment vessel 76 that contains at least a portion of the control rod drive mechanisms 10. A plurality of drive shaft housings 77 may be located within the upper receiving container 76. A plurality of drive shafts 20 associated with the control rod drive mechanisms 10 may be located in the reactor pressure vessel 52 housed in the main containment vessel 70. The drive shaft housing 77 may be configured to house at least a portion of the drive shaft 20 during operation of the reactor module 5. In some examples, substantially all of the crdm 10 may be housed within the main containment vessel 70.

The upper receiving container 76 is removably attached to the main receiving container 70. By removing the upper containment vessel 76, the overall size and/or volume of the reactor module 5 may be reduced, which may affect the peak containment pressure and/or water level. In addition to reducing the overall height of the reactor module 5, removing the upper containment vessel 76 from the main containment vessel 70 may further reduce the weight and transport height of the reactor module 5. In certain exemplary reactor modules, a weight of several tons may be removed for each foot of reduction in the overall height of the reactor module 5.

The reactor pressure vessel 52 and/or the main containment vessel 70 may include one or more steel vessels. Additionally, the primary containment vessel 70 may include one or more flanges by which a top head or a bottom head of the primary containment vessel 70 may be removed from the containment vessel body, such as during refueling operations.

During refueling, the reactor module 5 may be repositioned from the operator's compartment into the refueling compartment and a series of disassembly steps may be performed on the reactor module 5. The operator pod may be connected to the refueling pod by water so that the reactor module 5 is transported in the water. The main containment vessel 70 may be removed, for example, the top head or the bottom head may be separated from the containment vessel body to gain access to the control rod drive mechanisms 10 and/or the reactor pressure vessel 52. During this refueling phase, the reactor pressure vessel 52 may remain completely submerged in the surrounding water in the refueling compartment. In some examples, an upper portion of the crdm 10 (such as the plurality of drive shaft housings 77) may be located above the water to facilitate access to the crdm 10 in a dry environment. In other examples, the entire crdm 10 may be submerged in a pool of water in a refueling bay.

The control rod drive mechanism 10 may be mounted to the upper head of the reactor pressure vessel 52 through a nozzle 78. The nozzle 78 may be configured to support the control rod drive mechanism 10 when the main containment vessel 70 is partially or fully disassembled during refueling operations. Additionally, the control rod drive mechanism 10 may be configured to support and/or control the position of the drive shaft 20 within the reactor pressure vessel 52.

The reactor pressure vessel 52 may include a generally capsule-shaped stack shell. In certain examples, the height of the reactor pressure vessel 52 may be about 20 meters. The drive shafts 20 may extend from the control rod drive mechanisms 10 at the upper head of the reactor pressure vessel 52 into the lower head of the reactor pressure vessel 52 so that they may be connected to a control rod assembly 80 (FIG. 1) inserted into the reactor core 6. The distance from the upper head of the reactor pressure vessel 52 to the reactor core 6, while less than the overall height of the reactor pressure vessel 52, may therefore be such that the length of the drive shaft 20 is also about 20 meters long, or in some examples slightly less than the height of the reactor pressure vessel 52.

FIG. 3 is a perspective view of a control rod assembly 80 that is partially retained above and partially inserted into a nuclear fuel assembly 90 in the reactor core 6. As described above, the plurality of drive shafts 20 extend downward from the control rod drive mechanisms 10 to the top of the reactor core 6. The control rod assembly 80 may include a cylindrical hub 82 attached to the bottom end of the drive shaft 20. An arm 84 extends radially outward from the cylindrical hub 82 and is attached at a distal end to a tip of a control rod 86.

The control rods 86 extend into a nuclear fuel assembly 90, which is alternatively referred to as a fuel bundle forming part of the reactor core 6. The nuclear fuel assembly 90 may include a top nozzle 92 supporting a plurality of pilot tubes 94. Guide tubes 94 extend downwardly from the top nozzle 92 and between the nuclear fuel rods (not shown). The control rods 86 control the rate of fission of uranium and plutonium in the nuclear fuel rods.

The control rods 86 are typically held above the nuclear fuel assembly 90 or held slightly inserted into the nuclear fuel assembly 90 by the drive shaft 20. The reactor core 6 may overheat. A nuclear fast control rod insertion operation is initiated in which the control rod drive mechanism 10 of figure 1 releases the drive shaft 20 causing the control rods 86 to drop down into the guide tubes 94 and between the nuclear fuel rods.

Fig. 4A illustrates a cross-sectional view of an exemplary reactor pressure vessel 52. The control rod drive mechanisms 10 may be mounted to an upper head 96 of the reactor pressure vessel 52 and configured to support a plurality of drive shafts 20 extending through the length of the upper reactor vessel body 60 of the reactor pressure vessel 52 toward the reactor core 6 located in a lower head 98 of the reactor pressure vessel 52. In certain examples, the lower head 98 may be removably attached to the upper reactor vessel body 60 at a flange 100, such as by a plurality of bolts.

In addition to housing a plurality of nuclear fuel rods, the reactor core 6 may be configured to receive a plurality of control rod assemblies 80 that are movably inserted between the fuel rods to control the power output of the reactor core 6. The lower end 102 of the drive shaft 20 may be connected to the control rod assembly 80 when the reactor core 6 is generating power. Additionally, the control rod drive mechanism 10 may be configured to control the position of the control rod assembly 80 within the reactor core 6 by moving the drive shaft 20 up or down within the reactor pressure vessel 52.

The upper end 104 of the drive shaft 20 may be received in the control rod drive mechanism pressure housing 77 above the upper head 96 of the reactor pressure vessel 52, such as when the control rod assembly 80 is removed from the reactor core 6. In certain examples, the crdm pressure housing 77 may include a single pressure vessel configured to receive the upper end 104 of the drive shaft 20. In other examples, the crdm pressure housing 77 may include a separate housing for each of the drive shafts 20.

The lower end 102 of the drive shaft 20 is shown disconnected from the control rod assembly 80, such as may be associated with refueling operation of the reactor core 6. During the initial phase of refueling operation, the lower head 98 may remain attached to the upper reactor vessel body 60 while the drive shaft 20 is disconnected from the control rod assembly 80. The reactor pressure vessel 52 may remain completely sealed from the ambient environment, which may include, in some examples, a water pool at least partially surrounding the reactor pressure vessel 52 during an initial phase of refueling operations.

The control rod drive mechanism 10 may include a remote disconnect mechanism by which the drive shaft 20 may be disconnected from the control rod assembly 80 without the need to open or otherwise disassemble the reactor pressure vessel 52. In certain examples, the reactor pressure vessel 52 may form a sealed region 106 surrounding the reactor core 6, the control rod assemblies 80, and the lower end 102 of the drive shaft 20. By remotely disconnecting the drive shaft 20, the control rod assembly 80 may be retained within the reactor core 6 when the drive shaft 20 is at least partially withdrawn into the control rod drive mechanism pressure housing 77.

Fig. 4B illustrates the example reactor pressure vessel 52 of fig. 4A partially exploded. The lower head 98 may be separated from the upper reactor vessel body 60 of the reactor pressure vessel 52 during refueling operations. In certain examples, the lower head 98 may remain stationary in the refueling station while the upper reactor vessel body 60 is lifted by a crane and moved away from the lower head 98 to facilitate access to the reactor core 6.

The drive shaft 20 is shown in a retracted or withdrawn position so that the lower end 102 may be fully retained within the upper reactor vessel body 60 and/or the crdm pressure housing 77. For example, the control rod drive mechanism 10 may be configured to raise the lower end 102 of the drive shaft 20 above a lower flange 108 used to mount the upper reactor vessel body 60 with an upper flange 110 of the lower head 98. Withdrawing the lower end 102 of the drive shaft 20 into the upper reactor vessel body 60 may provide additional clearance between the lower flange 108 and the upper flange 110 during refueling operations and further may prevent the drive shaft 20 from contacting foreign objects or being damaged during transport and/or storage of the upper reactor vessel body 60. Additionally, the upper end 104 of the drive shaft 20 may be similarly received and/or protected by the control rod drive mechanism pressure housing 77 when the drive shaft 20 is in the retracted or withdrawn position.

As noted above, the control rod assembly 80 may remain fully inserted in the reactor core 6 during some or all of the refueling operations. In certain examples, the insertion of the maintenance control rod assembly 80 within the reactor core 6 may be dictated by nuclear regulatory and/or safety considerations.

Single hinge type control rod drive mechanism

FIG. 5 is a side view and FIG. 6 is a plan view of a single hinge type CRDM 88 incorporating a remote disconnect mechanism. Referring to fig. 5 and 6, the driveshaft housing 77 covers the top end of the driveshaft 20 and extends around the latch mechanism 138. The drive shaft housing 77 is alternatively referred to as an upper pressure boundary.

As described above, the drive shaft 20 enters the Reactor Pressure Vessel (RPV)52 in fig. 2 through the nozzle 78 connected at the top to the bottom end of the drive shaft housing 77. The bottom end of the drive shaft 20 is removably connected to a control rod assembly 80, as shown in more detail below.

The control rod drive mechanism 88 includes a drive assembly 122 that raises and lowers the drive shaft 20 and attached control rod assembly 80. The control rod drive mechanism 88 also includes a disconnect assembly 120 that disconnects the drive shaft 20 from the control rod assembly 80. Both the drive assembly 122 and the disconnect assembly 120 may be remotely enabled and controlled from outside of the reactor pressure vessel 52 via electrical control signals.

FIG. 7 is a side cross-sectional view of the control rod drive mechanism 88 and FIG. 8 is a more detailed cross-sectional view of the single hinge latch assembly 138 used in the control rod drive mechanism 88. Referring to fig. 7 and 8, through-holes 158 are provided in the drive shaft housing 77 and the nozzle 78. Bolts (not shown) may be inserted into the holes 158 to connect the driveshaft housing 77 to the nozzle 78 extending upwardly from the upper head of the reactor pressure vessel 52, as shown above in fig. 2.

The trip bar 132 extends through the entire length of the drive shaft 20, and a cylindrical trip magnet 134 is attached to the top end of the trip bar 132. The break magnet 134 extends up into the drive shaft housing 77 and an annular break coil 136 extends around the drive shaft housing 77 and the break magnet 134. When activated, the disconnect coil 136 may hold the disconnect magnet 134 in the raised position, allowing the disconnect rod 132 to retract vertically upward within the drive shaft 20.

The upper end of the drive shaft 20 includes an outer surface with threads 140. In one example, the threads 140 may include threads for linearly moving the drive shaft 20And (4) forming threads. Of course, any other type of threads or gears may be used. The drive shaft 20 extends from below the disconnect magnet 134 through the drive shaft housing 77 and nozzle 78 into the upper head of the reactor pressure vessel 52 (fig. 1). The drive shaft 20 further extends through the length of the reactor pressure vessel 52 and includes a catch hook 126 at the bottom end that is connected to the control rod assembly 80. The trip magnet 134 and trip coil 136 complete the trip assembly 120.

An annular arrangement of drive coils 128 may extend around the exterior of the drive shaft housing 77, and an annular arrangement of drive magnets 130 inside the drive shaft housing 77 may extend around the drive shaft 20. Continuously activating the drive coil 128 may cause the drive magnet 130 to rise. The alternating activation of the alternating drive coils 128 in fig. 8 may also rotate the drive magnet 130 about the central axis 156 of the drive shaft 20. The drive coil 128, the drive magnet 130, and the latch assembly 138 form the drive assembly 122.

The single hinge latch assembly 138 is coupled to the drive shaft housing 77 on the bottom end and to the drive magnet 130 on the top. The latch assembly 138 includes an annular base 142 that includes a central opening extending around the drive shaft 20. A lip 143 extends outwardly from the outer bottom end of the annular base 142 and seats into a groove formed between the bottom end of the drive shaft housing 77 and the top end of the nozzle 78. The lip 143 acts as a compression retention seat 142 down against the top surface of the nozzle 78.

An annular collar 148 is rotatably attached to the annular base 142 and contains a step 144 attached on top of a bearing 154 that extends around the top of the annular base 142. The collar 146 also includes a central opening that receives the drive shaft 20 and extends around the drive shaft 20. The collar 146 is held vertically/elevationally down onto the base 142 but rotates about a central axis 156 of the drive shaft 20 on top of the bearing 154 and the base 142.

The outer end of the gripper 150 is pivotally attached to the upper end of the collar 148 by a first pin 152A. The inner end of the gripper 150 is pivotally attached to the bottom end of the latch 146 by a second pin 152B. The top end of the latch 146 is attached to the drive magnet 130. When the drive magnet 130 is lowered, the bottom end of the latch 146 may be located on top of the step 144 of the collar 148.

When activated, the drive coil 128 lifts the drive magnet 130 vertically upward, thereby also lifting the latch 146. Lifting latch 146 rotates the inner end of gripper 150 upward to engage threads 140 on drive shaft 20. The outer end of the gripper 150 rotates about a first pin 152A that is held in place vertically by the collar 148.

After raising the inner end of the gripper 150, the drive coil 128 may begin to rotate the drive magnet 130 about the central axis 156 of the drive shaft 20. The bottom end of the drive magnet 130 begins to rotate the raised latch 146 and attached gripper 150 around the outer circumference of the drive shaft 20. Rotating the holder 150 also rotates the collar 148 over the top of the base 142 and about the central axis 156 while remaining pressed in place in height by the base 142.

The inner end of the holder 150 rotates within the threads 140, moving the drive shaft 20 axially and linearly upward within the drive shaft housing 77 and the nozzle 78. The drive coil 128 may rotate the drive magnet 130 in the opposite direction, thereby also rotating the attached gripper 150 in the opposite direction within the threads 140. Thus, the gripper 150 moves the drive shaft 20 axially and linearly in an upward or downward direction as directed by the electrical control system.

Deactivating the drive coil 128 causes the drive magnet 130 to fall vertically downward. The inner end of the holder 150 is also rotated downward about the second pin 152B to disengage the threads 140. Now released from the gripper 150, the drive shaft 20 is free to fall vertically downwards via gravity.

Fig. 9 is a cross-sectional plan view of the drive assembly 122. An annular drive coil 128 extends around the exterior of the drive shaft housing 77 and an annular drive magnet 130 extends around the interior of the drive shaft housing 77. The drive shaft 20 extends through a central opening formed in the drive magnet 130, and the trip rod 132 extends through a bore formed along the central axis of the drive shaft 20. The threads 140 extend around the outer surface of the drive shaft 20.

When continuously activated, the drive coil 128 generates an electromagnetic field that elevates the drive magnet 130 vertically. When the drive coil 128 is activated in an alternating pattern, the electromagnetic field also rotates the drive magnet 130 about the central axis, thereby rotating the drive assembly 122 to operate as effectively as an electric motor. For example, the electrical control system may activate drive coil a during a first time period and activate drive coil B during an alternating second time period. The alternating activation of drive coils a and B causes the drive magnet M to rotate about a vertical axis extending through the drive shaft 20.

Fig. 10 is a cross-sectional plan view of the single hinge latch assembly 138. The break-off rod 132 extends through the center of the drive shaft 20. The threads 140 extend around the outer surface of the drive shaft 20. The latch 146 has an annular cross-sectional shape and is attached to an inner end of the holder 150 via a second pin 152B. The collar 148 also includes an annular cross-sectional shape and is attached to the outer end of the holder 150 via a first pin 152A. As described above, the latch 146 is attached to the driving magnet 130 and can move vertically upward and downward. The drive shaft housing 77 also has an annular cross-sectional shape that is concentrically aligned with the drive shaft 20. It should also be noted that any number of holders 150 may be placed around the drive shaft 20. For example, four grippers 150 may be placed at 90 degree intervals around the drive shaft 120.

11A-11E are side cross-sectional views illustrating different operating positions of the control rod drive mechanism 88. Referring to fig. 11A, the drive assembly 122 is shown in a lowered state. With the control rod assemblies 80 fully inserted into the reactor core 6 (fig. 1), the drive coils 128 are deactivated and the drive magnets 130 are in the lowered position. The lowered drive magnet 130 and attached latch 146 release the clamp 150 from the threads 140 of the drive shaft 20.

During a loss of power or forced rapid control rod insertion, the drive coil 128 may be deactivated, thereby allowing gravity to drop the drive shaft 20, disconnected from the latch assembly 138, downward. The attached control rod assembly 80 correspondingly drops into the fuel assembly 90, thereby deactivating the reactor core 6 (see fig. 1 and 3). Thus, the control rod drive mechanism 88 has the advantage of automatically and quickly stopping the reactor core 6 whenever it is deactivated during a power failure.

The disconnect assembly 120 is also shown in a lowered state. The de-energizing coil 136 is deactivated and the de-energizing magnet 134 is in a lowered position at the top of the drive shaft 20. In the lowered position, the bottom end of the trip bar 132 extends between the reciprocating arms 127A and 127B of the grapple 126. The diverging grapple arms 127A and 127B press against and lock into the slots in the cylindrical hub 82 of the control rod assembly 80.

Fig. 11B shows the drive assembly 122 in a raised state. The drive coil 128 is activated and the drive magnet 130 is in the raised position. The raised drive magnet 130 raises the attached latch 146, moving the inner end of the gripper 150 upward, interlocking with the threads 140 of the drive shaft 20. The locked gripper 150 may raise or lower the drive shaft 20 based on the direction of rotation of the drive magnet 130.

The disconnect assembly 120 is still shown in the lowered state, with the bottom end of the disconnect bar 132 remaining inserted between the grapple arms 127A and 127B. The diverging grapple arms 127A and 127B remain locked to the interior of the cylindrical hub 82, thereby locking the lower end of the drive shaft 20 to the control rod assembly 80.

Fig. 11C shows the drive assembly 122 in a raised state. The drive coil 128 is activated and the drive magnet 130 is raised, moving the attached latch 146 upward, engaging the inner end of the gripper 150 with the threads 140. The drive coil 128 may also begin to rotate the drive magnet 130, thereby rotating the gripper 150 about the engaged threads 140 of the drive shaft 20. Rotating the grippers 150 pushes the drive shaft 20 axially and linearly up into the drive shaft housing 77 and lifts the connected control rod assemblies 80 a short distance, which does not cause reactivity induction (within so-called dead zones) in the reactor core.

Raising the drive shaft 20 also raises the trip magnet 134, maintaining the bottom end of the attached trip bar 132 between the grapple arms 127A and 127B. In other words, lifting the drive shaft 20 and the disconnect rod 132 together maintains the bottom end of the drive shaft 20 attached to the control rod drive mechanism 80 prior to disconnection as discussed below.

Fig. 11D shows the drive assembly 122 in a lowered state and the disconnect assembly 120 in a raised state. The disconnect coil 136 is activated when the drive shaft 20 and disconnect magnet 134 are in the raised position shown in fig. 11C. The drive coil 128 may then rotate the drive magnet 130 in the opposite direction, thereby lowering the drive shaft 20 vertically downward. At the same time, the disconnect coil 136 holds the disconnect magnet 134 in the raised position. As the gripper 150 continues to move the drive shaft 20 linearly downward, the bottom end of the trip bar 132 slides upward out from between the grapples 126. The grapple arms 127A and 127B correspondingly reciprocate inward to disengage the control rod assembly 80, which drops a short distance. Instead, the drive coil 128 is deactivated, causing the drive shaft 20 to drop and the control rod assembly 80 to trip, wherein the trip magnet 134 is held in the raised position by means of the trip coil 136.

Fig. 11E shows the disconnect assembly 120 and drive assembly 122 in a lowered state. Deactivating the trip coil 136 releases the trip magnet 134, causing the bottom end of the trip bar 132 to slide between the grapple arms 127A and 127B. The drive coil 128 can then be deactivated, thereby disconnecting the gripper 150 from the drive shaft 20. The forked grapple 126 is then positioned on top of the control rod assembly 80.

Thus, during reactor core refueling operations, the drive coil 128 and disconnect coil 136 may be remotely activated and deactivated to linearly move the drive shaft 20 and also disconnect the drive shaft 20 from the control rod assembly 80. The reconnection of the control rod assemblies 80 after completion of refueling and reassembly of the reactor vessel 52 (fig. 4A and 4B) may be performed in the reverse order of the steps shown in fig. 11A through 11D.

Double-hinge type control rod driving mechanism

Fig. 12 is a side view of a double-hinge type crdm 159. Fig. 13A and 13B are side cross-sectional views of the control rod drive mechanism 159. Fig. 14 is a more detailed view of the dual-hinge latch assembly 160.

Referring to fig. 12, 13A, 13B and 14, the drive assembly 122 and disconnect assembly 120 in the crdm 159 contain drive and disconnect coils and magnets substantially the same as described above. The drive shaft housing 77 and the nozzle 78 are also all substantially the same as those described above. The outer surfaces of the break-off bar 132, the drive shaft 20, and the threaded 140 are also similar to those described above.

Similar to the above, continuously activating the drive coil 128 may raise and align the drive magnet 130 with the annular drive coil 128. The alternating activation of adjacent drive coils 128 may also rotate the drive magnet 130 about the central axis 156 of the drive shaft 20 to force the drive shaft 20 and attached control rod assembly 80 to move linearly.

The dual hinge latch assembly 160 is coupled to the drive shaft housing 77 at a bottom end and to the drive magnet 130 at a top end. The latch assembly 160 includes a similar base 142 as described above, the base 142 including a central opening extending around the drive shaft 20. A similar lip 143 extends outwardly from the outer bottom end of the base 142 and seats into a groove formed between the bottom end of the drive shaft housing 77 and the top end of the nozzle 78. The lip 143 acts as a compression retention seat 142 down against the top surface of the nozzle 78.

Referring to fig. 13A, the drive assembly 122 is shown in a raised state. Activation of the drive coil 128 raises the drive magnet 130 and the attached latch 162. The lower end of the retainer 164 moves upwardly and inwardly into engagement with the threads 140 of the drive shaft 20. The locked gripper 164 may then raise or lower the drive shaft 20 depending on the direction of rotation of the drive magnet 130.

The disconnect assembly 120 is shown in a lowered position, in which the bottom end of the disconnect bar 132 is inserted between the arms 127A and 127B of the grapple 126. The diverging arms 127A and 127B lock into the interior of the cylindrical hub 82, thereby locking the bottom end of the drive shaft 20 to the control rod assembly 80.

Referring to fig. 13B, the drive assembly 122 and disconnect assembly 120 are shown in a lowered state. Deactivating the drive coil 128 lowers the drive magnet 130 and the attached latch 162. The retainer 164 moves downward and outward to disengage from the threads 140 of the drive shaft 20.

With the bottom end of the trip bar 132 remaining inserted between the arms 127A and 127B of the grapple 126, the trip assembly 120 is still shown deactivated. The diverging arms 127A and 127B remain locked to the interior of the cylindrical hub 82, thereby locking the bottom end of the drive shaft 20 to the control rod assembly 80.

In fig. 14, an annular collar 148 similar in design to fig. 8 is attached to the base 142 but rotationally disengaged with respect to the base 142 and contains a similar step 144 attached on top of a bearing 154 extending around the top of the base 142. The collar 146 also includes a central opening that receives and extends around the drive shaft 20. The collar 146 is held vertically/elevationally down onto the base 142, but is rotatable about a central axis 156 of the drive shaft 20 at the top of the bearing 154 and the base 142.

The outer end of the hinge 168 is pivotally attached to the top end of the collar 148 by a first pin 166A. The inner end of hinge 168 is pivotally attached to the lower end of holder 164 by a second pin 166B. The top end of the latch 162 is attached to the drive magnet 130, and the bottom end of the latch 162 is pivotably attached to the top end of the gripper 164 by a third pin 166C.

When activated, the drive coil 128 lifts the drive magnet 130 vertically upward, thereby also raising the latch 162. The inner ends of the holder 164 and hinge 168 also move upwardly, thereby moving the bottom end of the holder 164 inwardly into engagement with the threads 140 of the drive shaft 20.

After engaging the lower end of the gripper 164, the drive coil 128 may begin to rotate the drive magnet 130 about the central axis 156 of the drive shaft 20. The bottom end of the drive magnet 130 also begins to rotate the raised latch 146 and engaged catch 164 about the drive shaft 20. Rotating the gripper 164 also rotates the collar 148 about the central axis 156 while being held vertically downward by the base 142.

The inner end of the retainer 164 rotates within the engaged threads 140, thereby linearly moving the drive shaft 20 upwardly within the interior of the drive shaft housing 77 and nozzle 78. The drive coil 128 may rotate the drive magnet 130 in the opposite direction, causing the gripper 164 to rotate in the opposite direction within the threads 140, causing the drive shaft 20 to move axially downward.

Deactivating the drive coil 128 causes the drive magnet 130 and the inner end of the gripper 164 to drop downward. The hinge 168 also rotates downward and outward, thereby disengaging the lower end of the holder 164 from the threads 140. The drive shaft 20 is now released from the gripper 150 and free to fall vertically downwards via gravity.

Fig. 15 is a cross-sectional plan view of the dual-hinge latch assembly 160. The trip bar 132 extends through the centerline of the drive shaft 20. The threads 140 extend around the outer surface of the drive shaft 20. The latch 162 has an annular cross-sectional shape and is attached at a bottom end to a top end of the holder 164. The collar 148 also includes an annular cross-sectional shape and is attached to the outer end of the hinge 168 via a first pin 166A. As described above, the collar 146 is attached to the drive magnet 130 and can move vertically upward and downward. The drive shaft housing 77 also has an annular cross-sectional shape that is concentrically aligned with the drive shaft 20.

16A-16G are simplified schematic diagrams illustrating different operations of the single-hinge or dual-hinge type CRDM 88, 159 described above, with emphasis on the primary elements performing the CRDM functions described herein. For purposes of explanation, the following abbreviations are used below.

Drive coil 128 ═ a

Drive magnet 130 ═ B

Latch 146, 162 ═ C

Drive shaft 20 ═ D

Holders 150, 164 ═ E

Break coil 136 ═ F

Break magnet 134G

Grapple 126H

Drive shaft housing 77 ═ I

Base 142J

Trip bar 132 ═ K

Control rod assembly 80 CRA

Concentric solenoids a and F extend outside of the drive shaft housing I (alternatively referred to as the pressure boundary). The external coils a and F interact to move the cylindrical magnets B and G, respectively, within the pressure boundary I.

Referring to fig. 16A, the driving coil a is initially powered off. The latch C is fixed to the annular drive magnet B and rests on a seat J inside the drive shaft housing I.

Referring to fig. 16B, the driving coil a is energized, thereby lifting the driving magnet B upward until aligned with the driving coil a. This lifts the latch C and engages the gripper E, which pivots about a pin that is fixed vertically with respect to the inside of the pressure boundary I, but allows rotation of the latch C. The holder E is fitted into the threaded groove of the drive shaft D.

Referring to fig. 16C, by operating the drive coil a in a particular sequence, the drive magnet B and latch C are caused to undergo rotational movement while still maintaining the same height as the drive coil a. This prevents the separation of the holder E. The rotational motion of the gripper E is translated into a linear drive shaft motion that raises the drive rod D and attached CRA.

Referring back to fig. 16A, upon receipt of a fast control rod insertion signal or loss of power, drive coil a releases drive magnet B, causing grippers E to pivot downward and outward due to the drop of latches C. This provides a safety feature in which gravity-driven dropping of the drive shaft D drops the attached CRA into the reactor core.

Fig. 16D-16G illustrate how the drive shaft D is remotely disconnected from the CRA prior to disassembly of the reactor pressure vessel 52 of fig. 4A and 4B. Drive coil a is initially de-energized and latch C rests on base J. This may be similar to the initial drive shaft engagement configuration shown in fig. 6A.

Referring to fig. 16D, drive coil a is activated, raising drive magnet B and latch C, engaging gripper E with drive shaft D. As shown in fig. 11C, the drive coil a then causes the drive magnet B and latch C to undergo rotational movement while maintaining the same height as the drive coil a. Rotating the gripper E moves the drive shaft D and the break magnet G linearly up into a raised position, lifting the attached CRA a short distance, which does not cause reactivity induction in the reactor core (within the so-called dead zone).

Referring to fig. 16E, drive coil a is still energized, thereby holding drive magnet B, drive shaft D, disconnect magnet G, and disconnect rod K in the raised position. The opening coil F is energized, thereby holding the opening magnet G and the attached opening rod K in position vertically. Then, driving coil a may rotate driving magnet B, latch C, and gripper E in the opposite direction, thereby linearly lowering driving shaft D. The grapple H on the bottom end of the drive shaft D is now holding the CRA and the bottom end of the trip bar K begins to move upward out of the grapple arm. The arms of the grapple H retract, thereby allowing the CRA to fall a short distance until it is again placed on top of the nuclear fuel assembly top nozzle 92 in fig. 3.

Referring to fig. 16F, drive coil a remains energized and thus holds drive magnet B in place. The opening coil F is then de-energized. This releases the break magnet G, thereby inserting the bottom end of the break rod K into the catch H on the bottom of the drive shaft D and expanding the catch on the bottom of the drive shaft.

Referring to fig. 16G, the drive coil a is de-energized, thereby releasing the ring-shaped drive magnet B and the latch C. The drive shaft D drops a short distance until the grapple H rests on top of the CRA cylindrical hub without engagement. This enables the upper and lower sections of the reactor pressure vessel to be separated for refueling without removing the CRA.

The re-connection of the grapple H with the CRA is performed in the reverse order. The drive coil a may move the drive shaft D and the disconnect magnet G vertically upward into the raised position. The trip coil F may be activated, thereby holding the trip magnet G and trip bar K in the raised position. Drive coil a may then lower drive shaft D, thereby retracting grapple H and inserting the grapple into CRA. The opening coil F can then be deactivated, causing the opening magnet G and the bottom of the opening bar K to fall between the grapples H. The grapple H expands to lock into the CRA.

Instead, the grapple H is reengaged with the CRA by pulling the break magnet G upward using the electromagnetic force of the break coil F. The opening magnet G is moved into the raised position without simultaneously energizing the drive coil a. The weight of the drive shaft D may be large enough so that only the breaking rod K moves upwards inside the drive shaft D. The grapple H is retracted and inserted into the CRA cylindrical hub. Then, the opening coil F is deactivated, so the bottom of the opening bar K falls down back into the grapple H. The grapple H expands to lock into the CRA.

Control rod drive mechanism cooling system

FIG. 17 shows an upper cross-sectional view of the reactor module 5 with an exemplary Control Rod Drive Mechanism (CRDM)88 having an integrated cooling system 180. FIG. 18 is an isometric view showing the control rod drive mechanism 88 and the cooling system 180 in greater detail. The reactor module 5 comprises the same upper containment vessel 76 housing as described above. A plurality of drive shaft housings 77 are located within the upper receiving container 76. As also described above, a plurality of drive shafts 20 extend downwardly into the reactor pressure vessel 52 through nozzles 78 that are connected at the top to the bottom end of the drive shaft housing 77.

The drive shaft housing 77 may hold any of the above-described control rod drive mechanisms 88, disconnect assemblies 120, drive assemblies 122, single hinge latch assemblies 138, or dual hinge type control rod drive mechanisms 159. As described above, the drive assembly 122 may raise and lower the drive shaft 20, and the disconnect assembly 120 may disconnect the drive shaft 20 from the control rod assembly 80 (FIG. 3). Both the drive assembly 122 and the disconnect assembly 120 may be remotely enabled and controlled from outside of the reactor pressure vessel 52 via electrical control signals.

As also mentioned above, any air or other gas present in the containment region 74 between the containment vessel 70 and the reactor pressure vessel 52 may be removed or evacuated prior to or during reactor startup. The gas evacuated or evacuated from the containment region 74 may include non-condensable gases and/or condensable gases.

The cooling system 180 includes a set of heat fins 184 that extend upward from the top of the drive coil 128 and around the disconnect assembly 120. The heat fins 184 may have a flat plate shape and may be formed of any heat sink material, such as aluminum, copper, stainless steel, or any other thermally conductive metal. The thermal fins 184 have improved paths for radiative heat transfer to containment vessel surfaces having lower temperatures formed within the containment region 74 between the reactor pressure vessel 52 and the containment vessel 70. The heat fins 184 can remove the heat generated by the drive coil 128 without significantly increasing the footprint of the control rod drive mechanism 88.

In one example, the heat fins 184 may be attached to or formed with an outer metal housing 185 that holds the drive coil 128. For example, the drive coil 128 and the thermal fins 184 may be formed as the same modular annular housing that can slide over the drive shaft housing 77.

FIG. 19 is a cross-sectional plan view of a lower portion of the control rod drive mechanism cooling system 180. As described above in fig. 9, the annular drive coil 128 extends around the outer circumference of the drive shaft housing 77, and the annular drive magnet 130 extends around the interior of the drive shaft housing 77. The drive shaft 20 extends through a central opening formed in the drive magnet 130, and the trip rod 132 extends through a bore formed along the central axis of the drive shaft 20. The threads 140 extend around the outer surface of the drive shaft 20.

The cooling channels 186 extend vertically through and/or between the drive coils 128 and form or retain the heat pipes 190. For example, the channel 186 may hold a metal tube that holds a fluid that together function as a heat pipe 190. In this example, four pairs of external heat pipes 190A and four pairs of internal heat pipes 190B extend through each drive coil 128 in a half-loop manner. The external heat pipe 190A and the internal heat pipe 190B are alternatively referred to as heat pipes 190.

FIG. 20 is a sectional plan view of an upper portion of the control rod drive mechanism cooling system 180 and FIG. 21 is an enlarged plan sectional view of the upper portion of the control rod drive mechanism cooling system 180. The cooling channels 188 extend vertically through the heat fins 184 and again form or retain tubes that function as heat pipes 190. The cooling channels 188 are connected to or formed continuously with the channels 186 in the drive coil 128 to form a heat pipe loop 190.

As described above in fig. 5-7, a cylindrical break magnet 134 is attached to the top end of the break rod 132 (fig. 7). The break magnet 134 extends up into the drive shaft housing 77 and an annular break coil 136 extends around the drive shaft housing 77 and the break magnet 134. The heat fins 184 extend radially outward from the break-off coil 136 and, in one example, comprise an upper section of the heat pipe 190. The heat pipes 190A and 190B extend upwardly through each heat fin 184 in a half-ring fashion.

The evaporator sections of the heat pipes 190A and 190B extend along the inside of the heat fins 184 and are covered by an insulating material 196 in the heat fins 184. In one example, the insulation material 196 may be any type of mineral wool, calcium silicate, fiberglass, microporous refractory material, fiberglass mat, Reflective Metal Insulation (RMI), or any other material commonly used to insulate pipes in nuclear power plants.

The condenser sections of the heat pipes 190A and 190B are fluidly coupled to the insulated sections of the heat pipes 190A and 190B, extend along the outside of the heat fins 184, and are surrounded by the condensing channels 198. In one example, the condensation channels 198 are a set of highly thermally conductive metal strips or slots extending radially outward from the outer surface of the heat pipe 190. The condensation channels 198 expose more of the outer surface area of the condensation section of the heat pipe 190 to the cooler receiving area 74 formed by the receiving receptacle 70 (fig. 17). Any other type of thermal fins or fins may be formed within the thermal fins 184 around the condensing portion of the heat pipe 190 to further increase the heat transfer rate.

Fig. 22 is an isometric side view of cooling system 180 and fig. 23 is a more detailed isometric side view of cooling system 180. In this example, a plurality of pairs of outer and inner circular heat pipe loops 190A and 190B extend through each drive coil 128 and heat fin 184, respectively. The external heat pipes 190A extend along the inside and outside of the drive coil 128 and the heat fins 184. The inner heat pipe 190B extends through the drive coil 128 and the heat fins 184 inside the outer heat pipe 190A.

The heat pipe 190 extends upwardly from the bottom end through the top end of the drive coil 128 and then further upwardly through the bottom end to the top end of the heat fins 184. The top end of the heat pipe 190 extends radially outward from the break-off coil 136 and the bottom end of the heat pipe 190 extends radially inward toward the drive shaft housing 77, forming a continuous loop.

An alternative option is to mount the cooler upper section 194 of the heat pipe 190 directly to the inner wall of the containment vessel 70 above the control rod drive mechanisms 88 where heat is transferred to the containment vessel surface by conduction. For example, the heat pipe 190 may comprise a ring: the rings extend further upward and away from the top of the heat fins 184 or drive coils 128 and contact the inner wall of the containment vessel 70. In both alternatives, once the heat is transferred to the containment vessel, it is dissipated to the environment outside the containment vessel.

The inner portions of the heat pipes 190A and 190B that are closer to the inside of the drive coils 128 and the heat fins 184 are referred to as an evaporator section 208, and the outer portions of the heat pipes 190A and 190B that extend closer to the outside of the heat fins 184 are referred to as a condenser section 210. The evaporator end 208 and the condenser end 210 are fluidly coupled together.

The heat pipe 190 may comprise any circular, oval, or flat tube or orifice formed of any material, such as copper, aluminum, stainless steel, or any other thermally conductive metal. The heat pipe 190 may contain any fluid 200 capable of transferring heat, such as water, ammonia, methanol, liquid sodium, or the like. When heated, the fluid 200 may transition to the evaporation state 200A, and when cooled, the fluid 200 may transition back to the condensation state 200B.

The evaporation and condensation of the fluid 200 creates a fluid flow through the heat pipe 190 that removes heat from the drive coil 128. For example, the drive coil 128, when operated, generates heat that vaporizes the fluid 200A. The vaporized fluid 200A rises upward through the evaporator end 208 of the heat pipe 190, thereby transferring heat from the drive coil 128.

As described above, the insulation material 196 in the upper condenser section 210 of the heat pipe 190 transfers the vaporized fluid 200A. The condensing channels 198 in the upper condensing section 210 of the heat pipe 190 condense the vaporized fluid 200A into droplets of condensed fluid 200B. Other types of porous media may be used in heat pipe 190 to help condense vaporized fluid 200A into condensed fluid 200B.

The condensed fluid 200B falls vertically downward through the condenser section 210 of the heat pipe 190 via gravity or capillary action. The drive coil 128 then reheats the condensed fluid 200B back into the vaporized fluid 200A, thereby circulating the fluid 200 back through the heat pipe 190 and further removing heat from the drive coil 128. A flow restrictor (not shown) may be located in the heat pipe 190 upstream of the drive coil 128 to control the direction and rate of flow of the fluid 200.

The passive cooling system 180 reduces or eliminates the number of water hoses, pipes and water pumping equipment typically used in active reactor component cooling water systems. The simplified cooling system 180 also embeds heat pipes 190 in the integrated drive coils 128 and heat fins 184 to provide a modular control rod drive mechanism 88 design in which the electric drive coils 128 can be more easily swapped out during maintenance operations. The cooling system 180 also overcomes the limitations of convective heat cooling in a Pressurized Water Reactor (PWR) control rod drive mechanism design in which the control rod drive mechanism electrical coils 128 are located outside of the control rod drive mechanism pressure boundary in a vacuum environment.

Having described and illustrated the principles of the preferred embodiments, it should be apparent that the embodiments may be modified in arrangement and detail without departing from such principles. All changes and modifications that come within the spirit and scope of the following claims are desired to be embraced therein.

Some of the operations described above may be implemented in software and other operations may be implemented in hardware. One or more of the operations, processes, or methods described herein may be performed by an apparatus, device, or system similar to those described herein with reference to the illustrated figures.

It will be apparent to one skilled in the art that the disclosed embodiments may be practiced without some or all of the specific details. In other instances, certain processes or methods have not been described in detail so as not to unnecessarily obscure the disclosed embodiments. Other embodiments and applications are possible, and thus, the following examples should not be viewed as limitations or restrictions on scope or setting.

Reference has been made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments. Although these disclosed embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, it is to be understood that these examples are not limiting, such that other embodiments may be utilized and that changes may be made to the disclosed embodiments without departing from their spirit and scope.

Although the examples provided herein have primarily described a pressurized water reactor and/or a light water reactor, it will be apparent to those skilled in the art that the examples may be applied to other types of power systems. For example, examples or variations thereof may also be made operable with boiling water reactors, sodium liquid metal reactors, gas cooled reactors, pebble bed reactors, and/or other types of reactor designs.

It should be noted that the examples are not limited to any particular type of reactor cooling mechanism, nor to any particular type of fuel used to generate heat within or in association with a nuclear reaction. Any ratios and values described herein are provided as examples only. Other ratios and values may be determined experimentally, such as by constructing a full-scale or proportional model of the nuclear reactor system.