Abstract:
An inertial fusion reactor device comprises an outer containment chamber and an inner containment chamber supported within the outer containment chamber to define a space between respective walls of the inner and outer containment chambers. Water is contained within the space for generating steam which feeds turbine generators. Fuel for a fusion reaction is suspended within the centre of the inner containment chamber by a suitable mechanism. The reaction is initiated by focussing a plurality of laser beams on the fuel. The structure permits the water to be used both for producing usable steam and for absorbing blast impact due to its incompressible nature.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an inertial fusion reactor device and more particularly relates to a containment system for capturing energy from an inertial fusion reaction.  
       BACKGROUND  
       [0002]     Two diverse technical approaches to fusion power are generally known, magnetic confinement fusion, also known as magnetic fusion energy (MFE) and inertial confinement fusion, also known as inertial fusion energy (IFE). These form the basis of a large number of fusion research programs. Magnetic confinement techniques, studied since the 1950s, are based on the principle that charged particles such as electrons and ions, ie, deuterons and tritons, tend to be bound to magnetic lines of force. Thus the essence of the magnetic confinement approach is to trap a hot plasma in a suitably chosen magnetic field configuration for a long enough time to achieve a net energy release, which typically requires an energy confinement time of about one second. In the alternative IFE approach, fusion conditions are achieved by heating and compressing small amounts of fuel ions, contained in capsules, to the ignition condition by means of tightly focused energetic beams of charged particles or photons. In this case the confinement time can be much shorter, typically less than a millionth of a second.  
         [0003]     Because the maximum plasma density that can be confined is determined by the field strength of available magnets, MFE plasmas at reactor conditions are very diffuse. Typical plasma densities are on the order of one hundred-thousandth that of air at STP. The Lawson criterion is met by confining the plasma energy for periods of about one second. A totally different approach to controlled fusion attempts to create a much denser reacting plasma which, therefore, needs to be confined for a correspondingly shorter time. This is the basis of inertial fusion energy (IFE).  
         [0004]     In the IFE approach, small capsules or pellets containing fusion fuel are compressed to extremely high densities by intense, focused beams of photons or energetic charged particles. Because of the substantially higher densities involved, the confinement times for IFE can be much shorter. In fact, no external means are required to effect the confinement; the inertia of the fuel mass is sufficient for net energy release to occur before the fuel flies apart. Typical burn times and fuel densities are 10 −10  s and 10 31 -10 32  ions/m 3 , respectively. These densities correspond to a few hundred to a few thousand times that of ordinary condensed solids. IFE fusion produces the equivalent of small thermonuclear explosions in the target chamber. An IFE power plant design, therefore, must deal with very different physics and technology issues than an MFE power plant, although some requirements, such as tritium breeding, are common to both. Some of the challenges facing IFE power plants include the highly pulsed nature of the burn, the high rate at which the targets must be made and transported to the beam focus, and the interface between the driver beams and the reactor chamber.  
         [0005]     In inertial fusion the fuel is compressed and heated using driver beams. Achieving ignition requires a large amount of energy to be precisely controlled and delivered to the fuel target in a very short time, and the target must be capable of absorbing this energy efficiently. To produce net energy, the IFE system must have gain, ie, more energy output than was used to make, compress, and heat the fuel. Driver efficiency and capsule design and fabrication are therefore important issues for an IFE reactor.  
         [0006]     The necessary energy can be delivered to the fuel by a variety of possible drivers. The four types of drivers receiving the most research attention are solid state lasers, KrF lasers, light-ion accelerators, and heavy ion accelerators. The leading driver for target physics experiments worldwide is the solid-state laser, and in particular the Nd:glass laser. The reason is that the irradiances required for IFE are, in the 10 18 -10 19  W/m 2  range. The Nd:glass laser was the first driver which could produce these large power densities on target and it has remained in the forefront because of its high performance, reliable technology, and relative ease of maintenance. Low efficiencies and pulse rates have traditionally eliminated Nd:glass lasers from serious consideration in IFE reactor designs. However, new Nd:glass technology, replacing flash lamp pumping with higher efficiency diode pumping and utilizing crystalline disks and gas cooling, could change this view. Higher driver efficiencies are achievable in KrF lasers and particle beam accelerators. Particle beams have thus far had difficulty in achieving the low divergences and small focal spots required for IFE experiments, a technical area where lasers have a natural advantage. In IFE reactors, however, focal spots as large as 1 cm are permitted, and it appears that both light and heavy ion drivers could meet this requirement.  
         [0007]     Two types of IFE targets have been investigated known as direct and indirect drive targets. Direct-drive targets absorb the energy of the driver directly into the fuel capsule, whereas indirect-drive targets use a cavity, called a hohlraum, to convert the driver energy to x-rays which are then absorbed by the fuel capsule. This latter method can tolerate greater inhomogeneities in driver illumination, albeit at the expense of the efficient delivery of energy to the capsule.  
         [0008]     The extremely high peak power densities available in particle beams and lasers can heat the small amounts of matter in the fuel capsules to the temperatures required for fusion. In order to attain such temperatures, however, the mass of the fuel capsules must be kept quite low. As a result, the capsules are quite small. Typical dimensions are less than 1 mm. Fuel capsules in reactors could be larger (up to 1 cm) because of the increased driver energies available. (Reference: Ellis, William R., 1993, “Fusion Energy” in Encyclopaedia of Chemical Technology, Volume 12, John Wiley &amp; Sons, Inc.)  
         [0009]     U.S. Pat. No. 4,690,793 to Hitachi Ltd. et al, U.S. Pat. No. 4,836,972 to Bussard et al, U.S. Pat. No. 5,410,574 to Masumoto et al. and U.S. Pat. No. 6,654,433 to Boscoli disclose various examples of fusion reactions however none describe a simple means of absorbing the force and heat from a fusion reaction to produce useful steam for driving a turbine.  
       SUMMARY OF THE INVENTION  
       [0010]     According to one aspect of the invention there is provided an inertial fusion reactor device comprising:  
         [0011]     an outer containment chamber;  
         [0012]     an inner containment chamber supported within the outer containment chamber to define a space between respective walls of the inner and outer containment chambers;  
         [0013]     a feed for selectively introducing a liquid into the space between the walls;  
         [0014]     a collector for collecting gas generated within the space between the walls;  
         [0015]     a target placer for placing a target fuel within the inner containment chamber; and  
         [0016]     a driver for compressing and heating the target fuel to initiate a fusion reaction.  
         [0017]     By providing a structure in which fluid, for example water, is received within a space between inner and outer chamber walls, the fluid acts both to absorb blast impact due to its incompressible nature, while also producing gas for driving turbine when absorbing heat from the fusion reaction.  
         [0018]     There may be provided a shock absorption system coupled in communication with an interior of the inner containment chamber.  
         [0019]     The shock absorption system may comprise a moveable column of fluid which is raised when pressure within the inner containment chamber elevates.  
         [0020]     There may be provided a valve in communication with the column of fluid for selectively preventing movement of fluid within the column.  
         [0021]     There may be provided an inlet chamber defining a volume external from the interior volume of the inner chamber in communication between the interior of the inner containment chamber and the column of fluid.  
         [0022]     Preferably both the inner and outer containment chambers are spherical and concentric with one another.  
         [0023]     The exterior of the outer containment chamber is preferably heat insulated.  
         [0024]     Preferably an interior surface of the inner containment chamber includes a liner of wear resistant material and is formed of a plurality of plates abutted with one another in an overlapping configuration. Each plate may be supported by a respective post spanning the space between the inner and outer containment chambers.  
         [0025]     There may be provided a plurality of channels spanning between the inner and outer chambers for receiving driver beams of the driver therethrough. Each channel of the driver preferably includes a cover member for selectively enclosing the channel.  
         [0026]     There may be provided a vacuum generator in communication with the interior of the inner containment chamber.  
         [0027]     The vacuum generator preferably comprises a fluid port for selectively adding and removing fluid from the interior of the inner containment chamber.  
         [0028]     There may be provided a target placer comprising a mechanism for suspending the target fuel at the center of the inner containment chamber.  
         [0029]     One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]      FIG. 1  is a partly sectional side elevational view of the fusion reactor device.  
         [0031]      FIG. 2  is a schematic top plan view of the device.  
         [0032]      FIG. 3 ,  FIG. 4  and  FIG. 5  are respective top plan, rear elevational and front elevational views of one of the plates forming the walls of the inner containment chamber of the reactor device.  
         [0033]      FIG. 6  and  FIG. 7  are partly sectional elevational views of a cover member for the driver in open and closed positions respectively.  
         [0034]      FIG. 8  is a front elevational view of the cover.  
         [0035]     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     
    
     DETAILED DESCRIPTION  
       [0036]     Referring to the accompanying figures there is illustrated a fusion reactor device generally indicated by reference numeral 10. The device  10  is particularly suited for producing useful work from an inertial fusion reaction by capturing steam released when a surrounding fluid is heated.  
         [0037]     The device  10  has an outer containment chamber  12  having spherical walls defining a spherical interior. The walls of the chamber are formed of a material having a high heat resistance so as to resist damage from the high heat generated by the reaction. Suitable materials for forming the walls may include various types of metal, ceramic or composite materials which also have sufficient strength to withstand the forces generated by the reaction. The walls are also insulated on an outer side to contain heat in the chamber. A rigid backing, for example concrete, is provided at the exterior of the outer chamber  12  for added structural support. In a typical installation, the device is constructed below ground.  
         [0038]     An inner containment chamber  14  also has walls which are spherical in shape and which are positioned concentrically within the outer chamber  12 . The inner chamber  14  is smaller in diameter than the outer chamber  12  to define an annular space  16  between the chamber walls of the inner and outer containment chambers. The inner chamber walls are also formed of a material having a high heat resistance and sufficient strength to withstand the heat and force generated by the reaction.  
         [0039]     The inner chamber  14  is formed of a plurality of overlapping plates  18  each supported on the outer chamber  12  by a respective post  20  spanning across the space  16  between the walls of the inner and outer chambers. Each plate  18  includes a center post mount on a rear face thereof for connection to the post  20  which mounts on the outer chamber  12 . Mounting of the plate to the post  20  is accomplished using threaded fasteners to permit selective separation thereof when the plates become worn and require replacement. The overlapping plates permit some relative movement therebetween to accommodate some expansion of the inner chamber without distortion of the inner chamber walls.  
         [0040]     Each plate has a generally rectangular front face  22  which is concave and forms a portion of the inner surface of the inner chamber  14 . A top flange  24  extends along the top edge of the front face  22  and a side flange  26  spans one side of the front face  22 . Each of the flanges is recessed from the front face  22  by a thickness of the plate for being overlapped by adjacent plates when the front faces  22  thereof are positioned adjacent one another. The top flange  24  is shorter than the overall plate by the width of the side flange  26  so that the flanges do not overlap one another when the front faces of adjacent plates are abutted with one another. Similarly, the side flange  26  is shorter than the plate by the height of the top flange  24 . The plates are provided with a close tolerance so that simply abutting the plates in the overlapped configuration described herein is sufficient for providing a seal between the plates for containing water within the annular space  16  between the inner and outer chamber walls.  
         [0041]     A shock absorption system is provided in communication with the interior of the inner chamber  14  for reducing the blast impact on the plates  18 . The system  30  comprises a plurality of inlet chambers  32  in open communication with the interior of the inner chamber  14  at circumferentially spaced positions about a lower portion of the inner chamber  14 . The inlet chambers  32  are much larger than the space between the inner and outer chambers and accordingly each defines a volume which projects externally beyond the inner and outer chamber with the outer chamber being sealed thereabout.  
         [0042]     A fluid conduit  34  is coupled to the inlet chamber  32  and extends upwardly therefrom for containing a column of fluid above the inlet chamber. A plug  34  is slidably mounted within the fluid conduit  33  and acts as a seal for containing liquid above the plug and preventing leakage into the inlet chambers. The plug  34  urges the fluid in the conduit upward when pressure in the inlet chambers causes the plugs to rise. At its lowermost position, each plug  34  is substantially flush with or below the communication of the inlet chamber  32  with the interior of the inner chamber  14 . A choke valve  36  is coupled to the fluid conduit  34  at a position spaced above the inlet chamber. The choke valve  36  comprises a flap valve which is rotated by a respective actuator  38  between open and closed positions. When closed the choke valve  36  seals the conduit spaced above the plug  34  to prevent further pressure relief of the plug moving upwardly to instead build gas pressure within the interior of the inner chamber  14  and the inlet chambers  32 .  
         [0043]     In use, the space  16  between the walls of the inner and outer chambers is filled with water received through a feed inlet  40  coupled through the outer chamber walls adjacent the bottom end of the device  10 . A feed valve  42  is coupled in series with the feed inlet  40  to seal off the supply of fluid into the space  16  and prevent the back pressure from escaping through the bottom of the device.  
         [0044]     A collector in the form of a plurality of steam outlets  44  are coupled through the outer chamber walls in communication with the space  16  at circumferentially spaced positions about the top end of the device. The steam outlets  44  are joined with one another at a common outlet  46  spaced above the inner and outer chambers for collecting any steam produced by the heating of the fluid within the space  16 . The common outlet  46  feeds to an electrical generating steam driven turbine.  
         [0045]     A target placer in the form of a fuel feeding mechanism  48  is coupled above the inner and outer chambers for depositing target fuel pellets  50  within the interior of the inner chamber  14 . The feed mechanism communicates through the walls of the inner and outer chambers by a feed tube  52  extending therethrough. The mechanism  48  selectively feeds pellets  50  into the sphere by suspending the pellet at the center of the sphere prior to the fusion reaction being initiated. The feed tube is sealed closed prior to the reaction being initiated.  
         [0046]     A driver mechanism  54  is provided for initiating the reaction. The mechanism includes a plurality of lasers  56  located at circumferentially spaced positions in one or more drive planes. As shown schematically in  FIG. 2 a  set of nine lasers are shown in a single driver plane in which each laser is directed at a space between two opposing lasers so that none of the lasers within a single driver plane are directed at one another yet each is directed to cross a single center point within the interior of the inner chamber  14  where the target fuel pellet is suspended. Eight lasers can be provided within a single plane without being directed at one another by positioning the lasers at 40 degrees, 80 degrees, 120 degrees, 160 degrees, 200 degrees, 240 degrees, 280 degrees, 320 degrees and 360 degrees respectively. Each of the lasers communicates through the walls of the inner and outer chambers by a respective driver tube  58  sealed across the space  16  between the chamber walls. Additional lasers may be provided in different planes, but still intersecting the centre of the sphere.  
         [0047]     Covers  60  are provided for the driver tubes  58  at the interior of the inner chambers  14  to prevent damage to the driver mechanism during the fusion reaction. Each cover  60  comprises a circular plate supported on a respective axle  62  which is parallel and spaced beside the respective tube  58  in sufficient proximity that the cover plate  60  overlaps the opening of the tube  58 . The axle  62  includes suitable flighting  64  thereabout which is engaged within a guide in the inner chamber wall such that the plate is automatically rotated about its axle  62  as the plate is displaced towards and away from the wall of the inner chamber. An aperture  66  is provided in the plate forming the cover  60  for alignment with the respective driver tube  58  when the plate is spaced inwardly from the wall of the inner chamber. When the plate is displaced towards the chamber wall, the flighting  64  causes the plate to rotate until the aperture  66  is no longer aligned with the feed tube when the plate is abutted against the wall of the inner chamber. The feed tube is thus protected when the cover  60  is in this closed position. A suitable biasing mechanism is provided to bias the covers  60  into the respective closed positions.  
         [0048]     In use, the plugs  34  are initially positioned at the bottoms of the respective fluid conduits. The space  16  is filled with water and the feed inlet  40  is sealed shut. The interior of the chamber  14  is prepared by first filling the chamber with water and then subsequently draining the water. while partially filing the remaining volume with an inert gas so that. once all of the water is drained from the inner chamber a partial vacuum of only inert gas is all that remains within the inner chamber  14 . A target fuel pellet  50  is then suspended within the interior of the inner chamber at the center thereof and the feed tube is sealed shut prior to the driver mechanism being activated to initiate the reaction. Once the lasers  56  are activated, the driver tubes are immediately closed as the fusion reaction begins. The build up of heat and pressure within the interior of the inner chamber  14  exerts pressure on the plugs  34  through the inlet chamber  32  to raise the fluid in the conduit  33  thereabove and thereby absorb some of the initial blast pressure of the fusion reaction. Once the initial blast is absorbed, the choke valves  36  are closed to contain as much heat and pressure within the inner chamber as possible. Subsequently opening the choke valves  36  again causes the fluid in the conduits  33  to urge the plugs  34  back down to the starting position to maintain pressure during the cooling phase of the interior of the inner chamber  14 . Cooling of the interior of the inner chamber occurs by transferring heat to the water in the space  16  which produces steam to drive a turbine as noted above.  
         [0049]     Typically, plural devices  10  would be operated and commonly feed their steam together to suitable turbine equipment. The reaction sequence of the devices would be arranged so that the resulting blasts would be evenly spaced at regular intervals so as to produce as constant a pressure of steam as possible. Accordingly, the reaction within each device takes place while adjacent devices are at different stages of preparation for another reaction.  
         [0050]     As described above, scientific research has demonstrated that certain types of lasers and particle beams are capable of producing the necessary temperatures to induce fusion from small capsules of isotopes of hydrogen, such as deuterium and tritium, when targeted by beams from a number of directions, typically as many as eight. The original beam might be mirrored to produce beams in these directions, and would probably require amplification by accelerators.  
         [0051]     As further described herein, the fusion reactor device generally comprises of a circular sphere consisting of an inner and outer shell with an appropriate space between them, and appropriately spaced structural plugs separating the shells. The inner shell is coated with an appropriate liner material, such as silicon carbide, and could consist of layered sheets. The outer shell might require to be reinforced with a layer of concrete, and would require an outer blanket of insulation to impede the escape, of heat.  
         [0052]     The inner shell is fastened to the outer shell and concrete with long bolts through appropriate channels to enable the inner shell to be removed and replaced. The whole sphere has channels for the driver beams.  
         [0053]     The space between the two shells is filled with water to absorb the heat produced the fusion and let off to a suitable chamber as steam, from which it is utilized to drive a steam turbine. A flow of water into the space is maintained until there is no longer sufficient heat to create steam. Since water is not compressible, the water would serve to strengthen the shell at the time of the initial fusion impulse.  
         [0054]     The sphere has mechanisms to absorb and cushion the initial pressure in the form of appropriately sized water channels located just above openings in the bottom half of the sphere and leading upward to an appropriate water source such as a lake or river. The length of the channels makes it ideal for the sphere to be located underground. The channels would be plugged at the bottom, but with a plug capable of lifting the water channel when required to absorb the pressure produced by the fusion. The channels could be combined into one at an appropriate height. The pressure is confined at some point by choking off the upward flow and allowing the plugs to maintain pressure by sinking under the pressure of the water above back to its original position as pressure in the sphere reduces.  
         [0055]     A further channel provides water to the space between the two shells from the bottom of the sphere, with a suitable valve to prevent back pressure from the steam, and with sufficient pressure to provide a flow of water to replace the water converted into steam.  
         [0056]     The fuel capsule is presented by dropping it from the top of the sphere by an appropriate mechanism through a hole which could be immediately closed. The fuel feeding mechanism suspends the capsule in the middle of the sphere where the beams intercept one another to initiate the reaction on contact of the beams with the fuel. Mechanisms close the beam channels immediately after the beams were sent to the fuel capsule to prevent the escape of pressure through those channels. Circular rotating disks with one or more holes to uncover the channels serve this purpose. The disks would have a central axle, with a raised curved disk operating within a clasp to rotate when pushed to open, with spring loading to retract the disk when it is desired to close the channels.  
         [0057]     It may be desirable to create a partial vacuum within the sphere prior to firing. This could be created by filling the inner sphere with water and then drawing it off from the bottom. To the extent that some gaseous material was desirable within the sphere during firing, this could be provided by an inert gas, preferably helium, which can be introduced during the draining process.  
         [0058]     Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.