Abstract:
A system and method isolate a nuclear power plant from effects of seismic action. An artificial lake is formed as a depressed area in the ground surrounded by walls or banks to constrain a volume of water within the depressed area. The lake has a concrete reinforced bed. The lake is surrounded by a land-based support area. The lake is filled from a source of water in liquid communication with the lake. The source is controlled to release water into the lake to maintain the lake at a selected level. At least one vessel floats on the surface of the water. The vessel is connected to the walls or banks of the lake with a plurality of shock absorbers to dampen movement of the vessel. A nuclear power plant erected on the vessel includes at least one cooling tower that receives cooling water from the lake.

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of priority under 35 USC §119(e) to U.S. Provisional Application No. 61/528,102 filed on Aug. 26, 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is in the field of energy generation, and, more particularly, is in the field of protection of nuclear energy generation plants from the effects of seismic activity. 
     2. Description of the Related Art 
     Concerns are continually be expressed about the safety of nuclear power generating plants if and when an earthquake or other seismic activity occurs sufficiently close to one or more of the plants to cause substantial movement of the structures (housings, supports, interconnection pipes, etc.) within the stations. In particular, people are concerned about the release of radioactive materials in the event of a structural failure and are further concerned about the loss of cooling water to a reactor. 
     SUMMARY OF THE INVENTION 
     An aspect of embodiments in accordance with the present invention is a system and a method to isolate a nuclear power plant from effects of seismic action. An artificial lake is formed as a depressed area in the ground surrounded by walls or banks to constrain a volume of water within the depressed area. The lake has a concrete reinforced bed and is surrounded by a land-based support area. The lake is filled from a source of water in liquid communication with the lake. The source is controlled to release water into the lake to maintain the lake at a selected level. At least one vessel floats on the surface of the water. The vessel is connected to the walls or banks of the lake with a plurality of shock absorbers to dampen movement of the vessel. A nuclear power plant erected on the vessel includes at least one cooling tower that receives cooling water from the lake. 
     The system and method disclosed herein protect a nuclear power plant from a maximum seismic event through the use of water isolation, shock control and wave damping. The system and method include additional redundant systems to provide maximum protection during seismic activity. The nuclear power plant has full auto shut-down mode, with continuous safe reactor cooling maintained. Constructing a lake and securing a large steel power plant float in the lake creates an on-site cooling source and the controlled seismic protection for the reactor. Prior to the disclosed system and method, locations for nuclear power plants were selected by larger bodies of water for cooling. Such locations allow major damage to existing nuclear power plants by tsunamis. The disclosed system and method reduce or eliminate the danger from a tsunami and use liquid separation to isolate the ground seismic waves from direct contact to the reactor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments in accordance with aspects of the present invention are described below in connection with the attached drawings in which: 
         FIG. 1  illustrates a cross-sectional elevational view of the nuclear power plant erected on a floating vessel in a lake; 
         FIG. 2  illustrates a plan view of the nuclear power plant of  FIG. 1 ; 
         FIG. 3  illustrates an enlarged cross-sectional elevational view of the nuclear power plant of  FIG. 1  to show the bridge and shock absorber that connect the vessel to the wall or bank surrounding the lake; 
         FIG. 4  illustrates an enlarged plan view of a pair of shock absorbers connected the vessel to the wall or bank surrounding the lake; 
         FIG. 5  illustrates an enlarged cross-sectional view of the triple-ply liner that lines the lake; 
         FIG. 6  illustrates an enlarged partially broken away view of the shock absorber showing the ball and socket joint at the connection with the vessel; 
         FIG. 7  illustrates a cross-sectional elevational view of the roller assembly traveler attached to shock absorber and mounted to the lake side; 
         FIG. 8  illustrates a partially broken away elevational view of the roller assembly traveler of  FIG. 7  looking orthogonal to the view in  FIG. 7 ; 
         FIG. 9  illustrates an enlarged view of a portion of the bridge of  FIG. 3 ; and 
         FIG. 10  illustrates an enlarged cross-sectional view of a portion of the concrete bed showing the rebar matrix, the backfill material and the natural rock base. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The seismic safe nuclear power plant is disclosed herein with respect to exemplary embodiments of a system and a method. The embodiments are disclosed for illustration of the system and the method and are not limiting except as defined in the appended claims. 
       FIG. 1  illustrates a cross-sectional elevational view of the nuclear power plant  10  erected on a vessel  12  floating in a lake  14 .  FIG. 2  illustrates a top plan view of the nuclear power plant, the vessel and the lake. 
     The lake  14  is defined by a concrete reinforced lake containment wall (lake wall)  100  formed within a special soil compaction area  101 . The lake wall is lined with a triple flexible lake bed liner  104 . The containment structure of the lake supports and contains a body of water  103 . 
     The nuclear power plant  10  comprises a power plant building  106  proximate to a nuclear reactor dome  107 . The plant further includes a plurality of cooling towers  108 . 
     The nuclear power plant  10  is positioned on the vessel  12  and thus floats on the lake  14 . The hull  102  of the vessel is secured to the lake wall  100  via a plurality of shock absorbers  105 . Access to the vessel and thus to the nuclear power plant is provided by a main access bridge  110 , which accommodates vehicles. Additional access is provided by a foot bridge  109  (shown in  FIG. 2 ). 
     The shock absorbers  105  are movable secured to the lake wall  100  by respective shock absorber vertical guide tracks  111 . The engagement of the shock absorbers with the vertical guide tracks allow the shock absorbers to move up and down with respect to the lake wall while maintaining the lateral position of the vessel  12  with respect to the lake wall. Accordingly, the shock absorbers accommodate changes in the water level of the lake  14  or other causes of vertical movement of the vessel with respect to the lake wall. 
     As further illustrated in  FIG. 1 , the vessel  12  includes a plurality of water intakes  112  that are coupled by pipes (not shown) and pumps (not shown) to the cooling towers  108  to provide cooling water. In the illustrated embodiment, four separate water intakes are provided for safety. Any or all of the intakes can be automatically or manually enabled to provide cooling during maximum power generation. 
     The nuclear power plant  10  is constructed with a safety factor that will withstand a major seismic event. The complete nuclear power plant  10  is isolated from direct soil activity during any seismic event by the water  103 . Additional safety includes redundancy in safety controls and on site replacement components in case a component fails during seismic conditions. In addition, the nuclear power plant includes at least three redundant on-site power generating systems to provide electrical power for the control systems within the plant. Preferably, the nuclear power plant includes a fuel reserve sufficient to enable the on-side power generating systems to operate for at least three weeks. 
     Maximum safety factor is produced by constructing the lake  14  shown in  FIGS. 1 and 2  and floating the complete nuclear power plant  10  on the vessel  14 . As illustrated in  FIGS. 1 ,  4  and  6 , stability is added to the floating nuclear power station on three sides with the giant shock absorbers  105  to the vertical guide track  111  fastened to the lake edge. 
     As shown in  FIG. 2 , the vessel  12  is positioned generally at one end of the elongated lake  14 . Excessive movement of the water  103  in the extended open portion of the lake is suppressed with a surface wave damping system comprising a large matrix of floating hollow concrete wave dampeners  114  of various sizes, which are arranged in a staggered pattern for maximum wave control. The pattern of dampeners is formed by cross connecting the corners of the dampeners with cables or chains  113  to interconnect the floating dampeners. A plurality of winches  115  are coupled to the cables or chains and are positioned at the lake edge to control tension on the wave damping matrix automatically as the lake  103  reacts to seismic event stabilizing lake surface. The automatic tensioning action of the winches with respect to the dampener matrix operates to control wave action on the surface of the lake during a seismic event. 
     As further shown in  FIG. 2 , pumps (not shown) return the water to the lake  14  from the nuclear power plant  10  via a plurality of return cooling lines  116 , which are connected to respective spray units  117 . The spray units advantageously comprise a plurality of spray heads to disburse the water over a large surface area and to provide additional cooling of the water before returning the water to the lake to mix with the lake water  103 . 
     As shown in  FIG. 1 , preparing the lake site requires oversized excavation to allow the back fill  101  of several different compacted layers of soil compounds, which are shown in  FIG. 10 . This reduces direct seismic activity to the reinforced concrete lake liner  100 . This method insures minimum seismic wave shock to concrete reinforced lake containment  100 . 
     For additional protection, the concrete reinforced lake containment  100  includes the flexible triple-membrane liner  104  inside that maintains lake integrity in the event the concrete reinforced lake containment  100  should fracture during a seismic activity. As illustrated in  FIG. 5 , the triple liner  104  is laid on the lake wall  100  with each layer laid individually with the bonded seams  129  diagonally placed in respect to each layer. This laying procedure provides maximum protection if the reinforced concrete lake wall  100  fractures. 
     The large body of water  103  in the lake  14  creates a natural heat sink to cool the reactor. In the event the lake loses all the water  103 , the floating steel nuclear power plant  10  can continue full operation with the vessel  12  resting on the concrete reinforced lake containment wall  100 . 
     As shown in  FIGS. 2 ,  3  and  9 , full accessibility remains due to design of both bridges  109  and  110 . Should the bridges  109 ,  110  have damage during seismic activity, two back-up bridges and the necessary equipment are stored on site for immediate easy replacement. 
     Although not shown in the drawings, the concrete reinforced lake containment wall  100  includes a plurality of areas that are further reinforced with heavy steel plates. The heavy steel plates are placed on the lake bed at precise locations to be determined by size and shape of floating power plant  10 . The steel reinforcing plates at the selected locations are used to support construction equipment and provide bearing support points for work on the floating nuclear power plant during construction and maintenance. After construction of the nuclear power plant  10  is completed and before the lake is filled, the triple-membrane  104  liner is laid in place. After all construction equipment is removed, the remaining steel support areas are covered with triple-membrane liners  104  by divers and are bonded to the existing liner with underwater adhesive. 
     As shown in  FIGS. 1 and 2 , the floating nuclear power plant is held on three sides by the large shock absorbers  105 , which are attached to respective three sides of the lake wall  100 . The shock absorbers are attached as shown in  FIG. 4 . The vertical tracks guide the shock absorbers  105  during the raising and lowering of the level of the water  103 . 
       FIGS. 4 ,  6 ,  7  and  8  illustrate the attachment of the shock absorbers  105 . As shown in  FIG. 4 , the vertical guide track  111  is mounted to the side of the lake wall  100 . 
       FIG. 6  illustrates an enlarged partially broken away view of the shock absorber  105  and further showing the ball and socket joint at the connection with the hull  102  of the vessel  12 . The ball and socket joint comprises a ball  124  at the end of the shock absorber, which is secured within a cavity formed by two plates  125  that form a ball joint mount. The ball joint mount is secured to a linear I-beam  126  on the inside of the hull  126  of the vessel. The I-beam is provided as a reinforcement between bulkheads inside the vessel. The I-beam provides a secure mounting base for the ball and socket joint. The I-beam also dissipates energy from the shock absorber mount during movement caused by a seismic event or other force. 
     As shown in  FIGS. 7 and 8 , a roller assembly traveler  130  is pivotally attached to respective ends of a pair of shock absorbers  105  via respective shock absorber mounting posts  123 . The shock absorbers are secured to the mounting posts by removable safety lock pins  133 . The roller assembly traveler includes a pair of horizontally opposed guide rollers  127  that engage the vertical guide track so that the lateral position of the roller assembly traveler is maintained as the traveler moves vertically within the guide track. As further shown in  FIG. 7 , the vertical guide track is secured to the containment wall  100  via a plurality of mounting bolts  132  screwed into a plurality of threaded inserts  131  that are embedded in the containment wall. 
     As briefly discussed above, vehicle access to the floating power plant on the vessel  12  is provided by the main bridge  110 . The second bridge  109  supports foot traffic. As shown in  FIGS. 3 and 9 , the flexible pre-tensioned bridges are supported and held in place by bridge rollers  122  ( FIG. 3 ) and bidirectional rotary pivots  121  that allow the bridges to accommodate changes in the level of the water  103  and other motion (e.g., seismic motion). As illustrated in  FIG. 9  for the main bridge, the bridge comprises a generally horizontal structure  134  that is coupled at each end to a respective hinged sliding plate  119  by a respective hinge  120 . The hinged sliding plate accommodates changes in the angular position of the bridge in response to relative vertical movement of the vessel with respect to the lake wall  100 . As shown in  FIG. 9 , the bridges include quick removal safety lock pins  133  for change-out in an emergency. 
     All power lines, water, sewer and any other necessary connections to the floating nuclear power plant  10  are constructed above ground with flexure and slack to accommodate seismic motion and lake level change. 
     The complete floating nuclear power plant  10  is equipped with every safety system required to operate the most modern nuclear plant; including an emergency auto start generating system and 30 days of fuel supply with full control during emergencies or shut down mode. 
     If the lake wall  100  breaches, a plurality of water-filled interconnected bladder tanks  135 , positioned on shore proximate to the vessel  12 , are able to supply water to replace the loss of the lake water  103 . When an emergency occurs, the bladder tanks are automatically switched to provide water to the cooling towers  108  in order to maintain cooling to reactor. 
     The bladder tanks  135  are readily filled by trucks or by a quick-lay land water line to maintain continuous operation when necessary in an emergency. Each of the bladder tanks includes internal air-filled baffles to provide internal motion wave damping during a seismic event. 
     As further shown in  FIG. 2 , the lake level is controlled by two separate automatic filling units that are supplied from respective independent water supply sources. The filling units maintain an ample water supply at all times by automatically adding water to the lake  14  as the water level decreases because of evaporation. 
       FIG. 10  illustrates an enlarged cross-sectional view of the concrete reinforced lake containment wall  100 , which includes a dual rebar matrix  135  in the preferred embodiment. The dual rebar matrix is surrounded by a concrete layer  136 . In the illustrated embodiment, the concrete layer comprises hi-tensile concrete having a thickness of 4 feet. As discussed above, the concrete and rebar lake containment wall is surrounded by and supported by compacted back fill  101 . The back fill advantageously comprises a substrate having a layer  137  of 2-inch crushed rock that is compacted to a thickness of approximately 2 feet. The crushed rock layer  137  is sandwiched between two layers  138  of sand and crushed rock that are each compacted to a thickness of approximately 6 feet. The lowermost layer  138  of sand and crushed rock lies on a layer  139  of sand, gravel and 2-inch crushed rock with cement mix. The layer  139  is wet-sprayed in 6-inch layers and is compacted to form an overall layer having a thickness of approximately 4 feet. The various layers are formed on an existing natural base  140 . 
     The embodiment illustrated herein protects the nuclear power plant  10  from a seismic event. The actual size and specific physical details of the nuclear power plant vary with power requirements and the geographical location of the power plant. For example, in an exemplary embodiment, a basic size for the vessel  12  that supports the floating nuclear plant is 300 feet by 600 feet. For example, a 300-foot by 600-foot vessel having a draft of 15 feet will support an 85,000-ton nuclear power plant. The surface area and the depth of the lake  14  are determined according to the specific requirements of the power generation necessary for each plant. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all the matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.