JP2011117907A - Fast reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fast reactor that facilitates the operation thereof and improves performances at installation and maintenance by reducing the size of a reflector and drive mechanism. <P>SOLUTION: In the fast reactor, the annular reflector 4 is provided around a reactor core 2 on which nuclear fuel is mounted and a nuclear reaction output is controlled by moving the reflector 4. The reflector 4 is formed to be plurally divided in circumferential direction. In each of the reflectors 4 plurally divided, a reflector drive mechanism 6 that axially moves the reflectors 4 is provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fast reactor in which a reflector is disposed on the outer periphery of a core, and more particularly to a fast reactor in which the combustion of core fuel is controlled by the reflector instead of a control rod.

  Conventionally, this type of fast reactor includes, for example, one described in Patent Document 1. As shown in FIG. 4, the fast reactor 101 includes a core 103 loaded with a plurality of nuclear fuels in a bottomed cylindrical reactor vessel 102, and an annular reflector disposed concentrically on the outer periphery of the core 103. 104 and the intermediate heat exchanger 105 installed in the upper part etc. are incorporated with the coolant.

  A reflector driving mechanism 107 is installed on the upper slab 106 placed above the upper end of the reactor vessel 102, and the reflector driving mechanism 107 is driven by a hydraulic device 108. In addition, a long and large-diameter reflector driving shaft 109 is provided between the reflector 104 and the reflector driving mechanism 107. By driving the reflector drive mechanism 107, the reflector 104 is moved up and down (lifted and lowered) via the reflector drive shaft 109 to control the combustion of the core fuel.

JP-A-6-59069

  However, the conventional reflector 104 described in Patent Document 1 described above is formed in an annular shape, and the reflector 104 and the reflector drive shaft 109 are integrally large in diameter and have a long structure. , Transportation from the factory and local assembly was difficult. Moreover, the reflector drive mechanism 107 that moves the reflector 104 to control the nuclear reaction is a single system, and it cannot be said that it sufficiently satisfies the requirements for a reactor control system that requires extremely high safety. It was.

  Further, as a drive source for the reflector drive mechanism 107, a hydraulic device 108 that outputs the reflector at a high speed so as to be movable up and down is used, and the reflector drive mechanism 107 needs to hold a fixed position for a long period during a steady operation. However, a minute leak cannot be avoided in the hydraulic system including the valve, and therefore, a complicated configuration of the hydraulic system control system is required, and the maintenance frequency and inspection items are large.

  The present invention has been made to solve the above-described problems, and provides a fast reactor in which a reflector and its drive mechanism are miniaturized to facilitate handling, and have improved installation and assembling properties and maintainability. Objective.

  In order to achieve the above object, a fast reactor according to the present invention is a fast reactor in which an annular reflector is disposed around a core in which nuclear fuel is loaded and the nuclear reaction output is controlled by moving the reflector. The reflector is divided into a plurality of parts in the circumferential direction, and a reflector driving mechanism for moving the reflectors in the axial direction is provided for each of the plurality of reflectors.

  According to the present invention, the reflector and the drive mechanism thereof can be downsized to facilitate handling, and the installation and assembling property and the maintenance property can be improved.

It is a longitudinal section lineblock diagram showing one embodiment of a fast reactor concerning the present invention. It is a longitudinal cross-sectional block diagram which shows the reflector drive mechanism at the time of an emergency stop. It is a longitudinal cross-section block diagram which shows the reflector drive mechanism at the time of nuclear reactor normal operation. It is a longitudinal cross-sectional block diagram which shows the conventional fast reactor.

  Hereinafter, an embodiment of a fast reactor according to the present invention will be described with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing an embodiment of a fast reactor according to the present invention. FIG. 2 is a longitudinal sectional configuration diagram showing the reflector driving mechanism at the time of emergency stop. FIG. 3 is a longitudinal sectional view showing a reflector driving mechanism during normal operation of the reactor.

  As shown in FIG. 1, a fast reactor 1 includes a core 2 loaded with nuclear fuel, a core tank 3 arranged in an annulus around the core 2, and a reflector arranged concentrically around the core 2. 4, a reflector drive shaft 5 connected to the reflector 4, and a reflector drive mechanism 6 connected to the reflector drive shaft 5 to move the reflector 4 up and down in the core tank 3 in the axial direction. The reactor vessel 7 for holding the coolant sodium, and the upper plug 11 installed above the reactor vessel 7 are provided.

  The reflector 4 is divided into a plurality of pieces (for example, six, and the number is not particularly limited) in the circumferential direction, and each of the divided reflectors 4 is a single reflector driving mechanism 6. Are coupled via a single reflector drive shaft 5.

  As shown in FIG. 2, the coupling portion between the lower end of the reflector driving shaft 5 and the top of the reflector 4 is formed in a T-bar portion 12 that is a coupling mechanism having a T-shaped cross section. The reflector 4 is connected to the reflector 4 by the axial rotation direction of the reflector drive shaft 5 and can be easily attached to and detached from the reflector 4 when rotated 90 degrees. Note that the coupling mechanism is not limited to the T-bar portion 12, and a gripper system that opens and closes the claw and attaches and detaches may be used.

  The reflector 4 is disposed in the region of the neutron reflector 4a for reflecting neutrons radiated from the core 2 and the upper portion of the region of the neutron reflector 4a, and encloses a gas (for example, nitrogen gas) therein. It is formed in a thin cylindrical shape and has a region of a cavity portion 4b for transmitting neutrons emitted from the core 2.

  Further, the reflector 4 is configured to adjust the nuclear reaction output by moving up and down, and is lowered during the reactor scram so that the cavity portion 4b is located on the side of the core 2. Therefore, when the cavity 4b for transmitting neutrons is located on the side of the core 2, the nuclear reaction is suppressed and combustion of the core 2 can be suppressed.

  As shown in FIG. 1, the reflector 4 and the reflector driving mechanism 6 are arranged around the reactor core 2, so that the value reaction determined by the reactor core design, the redundancy in the reactor shutdown function, and the requirement for system separation are obtained. In order to satisfy the above conditions, a furnace stop system device composed of a furnace stop rod 30 and a furnace stop rod drive mechanism 31 can be easily arranged at the center of the furnace.

  FIG. 2 shows the fully inserted state (scrum state) of the reflector 4.

  As shown in FIG. 2, an upper plug 11 is installed above the reactor vessel 7, and a reflector driving mechanism 6 is provided on the upper plug 11.

  The reflector drive mechanism 6 includes a three-system drive mechanism including a high-speed drive mechanism 13, a medium-speed drive mechanism 14, and an ultra-low speed drive mechanism 15. The high-speed drive mechanism 13 is mounted in parallel with the electric cylinder 16, the high-speed moving movable plate 17 connected to the reflector drive shaft 5, and the electric cylinder 16, and a shock absorber that limits the speed when the reflector 4 is lowered in an emergency. 18. The medium speed drive mechanism 14 includes an electric cylinder 19 and a medium speed moving movable plate 20 connected to the reflector drive shaft 5, and is connected in series with the high speed drive mechanism 13.

  The ultra-low speed drive mechanism 15 is supported by a high-speed drive mechanism 13 and a medium-speed drive mechanism 14 so as to freely move up and down (up and down). The ultra-low speed drive mechanism 15 is attached to a drive motor 21, an output shaft of the drive motor 21, a speed reducer 22 for decelerating the rotational speed of the drive motor 21, and a rotational motion of the drive motor 21 to a linear motion. A ball screw 24a for conversion, and the reflector 4 is moved up and down at a super-low speed.

  In the system of the high speed drive mechanism 13 and the medium speed drive mechanism 14, a position detector 23a is attached to the medium speed moving movable plate 20 via a ball screw 24b. A vessel 23b is attached.

  Further, an outer housing 25 is installed on the upper plug 11, and a stopper 26 is attached to the outer housing 25 for preventing an unnecessary lifting operation (pulling operation) by the electric cylinders 16 and 19. .

  Next, a basic operation procedure and operation of the reflector drive mechanism 6 will be described. The main operations are start-up operation, critical proximity / power compensation operation, combustion compensation operation, stop operation, and emergency rapid descent.

  The starting operation is performed by using the high-speed drive mechanism 13 of the three systems of the high-speed drive mechanism 13, the medium-speed drive mechanism 14, and the ultra-low-speed drive mechanism 15, and the medium-speed movable plate of the medium-speed drive mechanism 14. The reflector 4 is lifted from the lower limit stop position to the start start position (about 500 mm from the lower limit stop position) by lifting the reflector drive shaft 5 via the 20 and the super slow speed drive mechanism 15. At this time, the moving speed of the reflector 4 is about 4 mm / sec.

  In the critical proximity / output compensation operation, by using the medium speed drive mechanism 14 of the three systems described above, the reflector drive shaft 5 is lifted via the medium speed movable plate 20 and the super slow speed drive mechanism 15. The reflector 4 is moved upward from the starting start position to the critical proximity / output compensation position (about 50 mm from the starting start position). At this time, in order to raise the reactor to a state just before the criticality, it is gradually raised while monitoring the neutron monitor. At this time, the moving speed of the reflector 4 is about 0.2 mm / sec.

  The combustion compensation operation is performed by driving the drive motor 21 constituting the ultra-low speed drive mechanism 15 of the three systems described above to rotate the ball screw 24 and operating the reflector 4 at an ultra-low speed. After entering the critical state, the normal operation mode is entered. The moving speed of the reflector 4 at this time is about 1 mm / day.

  Here, by gradually operating the reflector 4 at a super-low speed, the fuel during the operation of the reactor becomes a reaction according to the moving speed of the reflector 4, and the fuel is exchanged during the lifetime of about 30 years. The output can be kept constant without any problem.

  The stop operation is performed by using the medium-speed drive mechanism 14 and the high-speed drive mechanism 13 of the three systems described above to move the medium-speed moving movable plate 20 and the high-speed moving movable plate 17 connected to the reflector drive shaft 5 to the start start position. By lowering, the reflector 4 is lowered to the start position, and the fast reactor 1 is stopped.

  In the emergency descent, the reflector 4 and the reflector drive shaft 5 are combined and lowered by their own weight by the reactor trip signal, and an electromagnetic clutch (not shown) provided in the high-speed drive mechanism 13 is used. ) Is automatically released at the time of the reactor trip signal and power loss, etc., and is naturally lowered by the gravity of the reflector 4, which is fail-safe.

  The shock absorber 18 of the high-speed drive mechanism 13 limits the speed of the natural lowering of the reflector 4 at the time of emergency lowering to prevent damage to the equipment due to excessive speed. At this time, the reflector 4 is dropped at a speed of about 120 mm / sec or less so that a stroke of about 1 m can be dropped within 8 sec.

  Although the electric cylinders 16 and 19 have a stroke (about 1200 mm) necessary for starting and stopping the reactor, the stopper 26 is provided on the outer housing so as not to perform a lifting operation (pulling operation) more than necessary. 25 to prevent reactor runaway and improve safety.

  Further, a position detector 23a is attached to the medium speed movable plate 20 via a ball screw 24b in the system of the high speed drive mechanism 13 and the medium speed drive mechanism 14, and a position detection is provided in the system of the super slow speed drive mechanism 15. A vessel 23b is attached to detect the respective vertical movement positions, thereby improving the safety of the core 2.

  FIG. 3 shows that the reflector 4 is pulled up and the reactor is in operation.

  In the full insertion position shown in FIG. 2, the high-speed moving movable plate 17 is in the start-up position with the rod of the electric cylinder 16 of the high-speed drive mechanism 13 contracted. In this state, the neutron reflector 4a of the reflector 4 is in the core. The neutrons in the core 2 are dissipatively diluted, the nuclear reaction is suppressed, and the reactor is stopped.

  In FIG. 3, the electric cylinder 16 of the high-speed drive mechanism 13 is in the start start position, the electric cylinder 19 of the medium-speed drive mechanism 14 is in the critical / output compensation position, and the slow speed drive mechanism 15 is in the combustion compensation position. Yes. When the reflector 4 is pulled up, the neutron reflecting portion 4a is opposed to the core 2 and the amount of neutrons in the core 2 is increased to promote the nuclear reaction.

  As described above, in this embodiment, since the reflector 4 and the reflector driving mechanism 6 are divided in the circumferential direction, the load per unit can be reduced. The range of selection of the structure and mechanism is widened.

  In addition, by configuring the reflector 4 and the reflector driving mechanism 6 independently, the safety of the core 2 can be sufficiently ensured even if a single device malfunctions. In addition, the reflector 4 can be divided and reduced in weight so that the high-speed drive mechanism 13 of the drive mechanism can be replaced with a hydraulic cylinder system having a simple configuration from a hydraulic cylinder for heavy loads.

  In other words, according to the present embodiment, by using the reflector 4 divided in the circumferential direction, the size of the reflector 4 is reduced and the handling becomes easy, and the installation work at the site becomes extremely easy and the maintainability is greatly improved. Can be made.

  Further, according to the present embodiment, the reflector drive mechanism 6 includes a high-speed drive mechanism 13 that moves the reflector 4 at a high speed when starting and stopping, and a medium-speed drive mechanism 14 that moves the reflector 4 at a medium speed during output control. And the ultra-low speed drive mechanism 15 that moves the reflector 4 at an ultra-low speed for combustion compensation, it is possible to move at an optimum speed for an extremely wide range of speed conditions. It becomes possible to improve the core safety.

  Furthermore, according to the present embodiment, the high-speed drive mechanism 13 and the medium-speed drive mechanism 14 use the electric cylinders 16 and 19 that are excellent in position holding, respectively. A complicated system is not required. As a result, maintenance items can be greatly reduced, and the operating rate can be greatly improved.

  According to the present embodiment, by providing the stopper 26 for restricting the moving operation of the reflector 4 by a predetermined amount or more by the electric cylinders 16 and 19 of the high-speed drive mechanism 13 and the medium-speed drive mechanism 14, the reflector at the time of abnormal control is provided. Since the excessive movement of 4 is prevented, structural soundness and safety can be improved.

  In addition, according to the present embodiment, the position detector 23 a for detecting the position of the reflector 4 is provided in the system of the high speed drive mechanism 13 and the medium speed drive mechanism 14, and the reflector 4 is provided in the system of the super slow speed drive mechanism 15. By providing the position detector 23b for detecting the position of the fast reactor 1, an interlock is assembled based on the position signals obtained from the position detectors 23a and 23b, and the malfunction of the reflector 4 is detected at an early stage. By stopping the operation, the safety of the core 2 can be greatly improved.

  Furthermore, according to this embodiment, since the coupling | bond part with respect to the reflector 4 of the lower end of the reflector drive shaft 5 was formed in the T-bar part 12 which is a coupling mechanism, operation from the upper end of the reflector drive shaft 5 is carried out. Since it is easily detachable, the reflector 4 and the reflector driving mechanism 6 can be easily coupled and separated. As a result, the workability can be significantly improved because the work can be performed separately by handling such as transportation, installation work, and maintenance of the drive unit.

DESCRIPTION OF SYMBOLS 1 ... Fast reactor 2 ... Core 3 ... Core tank 4 ... Reflector 4a ... Neutron reflection part 4b ... Cavity part 5 ... Reflector drive shaft 6 ... Reflector drive mechanism 7 ... Reactor vessel 11 ... Upper plug 12 ... T-bar part (Coupling mechanism)
DESCRIPTION OF SYMBOLS 13 ... High-speed drive mechanism 14 ... Medium speed drive mechanism 15 ... Super-low speed drive mechanism 16 ... Electric cylinder 17 ... High-speed movement movable plate 18 ... Shock absorber 19 ... Electric cylinder 20 ... Medium-speed movement movable plate 21 ... Drive motor 22 ... Deceleration Machine 23 ... Position detectors 24a and 24b ... Ball screw 25 ... Outer housing 26 ... Stopper 30 ... Furnace stop rod 31 ... Furnace stop rod drive mechanism

Claims (5)

A fast reactor in which an annular reflector is arranged around a core in which nuclear fuel is loaded, and the nuclear reaction power is controlled by moving the reflector.
A fast reactor in which the reflector is divided into a plurality in the circumferential direction, and a reflector driving mechanism for moving the reflectors in the axial direction is provided for each of the divided reflectors. The reflector drive mechanism includes a high-speed drive mechanism that moves the reflector at a high speed when starting and stopping, a medium-speed drive mechanism that moves the reflector at a medium speed during output control, and a super-high-speed reflector for combustion compensation. Having an ultra-low speed drive mechanism that moves at a low speed,
The fast reactor according to claim 1. The high-speed drive mechanism and the medium-speed drive mechanism each use an electric cylinder,
The fast reactor according to claim 2. Provided with a stopper for restricting a predetermined or more movement operation of the reflector by the high-speed drive mechanism and the medium-speed drive mechanism;
The fast reactor according to claim 2 or 3. A position detector for detecting the position of the reflector is provided in each of the high-speed drive mechanism, the medium-speed drive mechanism, and the ultra-low speed drive mechanism;
The fast reactor according to any one of claims 2 to 4.

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