Abstract:
The invention provides an apparatus for safely transporting various hazardous materials, including spent nuclear fuel. The invention includes a cask cradle that is configured to securely receive a cask for containment of hazardous materials, such as spent nuclear fuel. The cask cradle in accordance with the invention includes a front cradle section load bearing brace, a rear cradle section having a first non-loading bearing brace and a second non-loading brace, first and second horizontal support members connecting the front cradle section to the rear cradle section and trunnions that lock into and retain the cask. The invention also provides a railcar having a depressed flatbed region for receiving and securely retaining the cask cradle. The railcar also includes a variety of sensors that monitor various aspects of the railcar performance, including braking performance sensors, sensors for truck hunting, rocking and vertical, lateral and longitudinal acceleration, a Global Positioning Satellite (GPS) sensor and wheel bearing sensors corresponding to each of the wheel bearing assemblies.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an apparatus for safely transporting spent nuclear fuel and other hazardous materials and, more particularly, to a rail transportation system for safely transporting spent nuclear fuel and other hazardous waste materials to interim storage facilities, transfer points, or to a final federal disposal site, the rail transportation system including a railcar and cask cradle. 
   2. Description of the Related Art 
   Nuclear reactors and storage sites for radioactive materials have been in operation for many years. In a nuclear reactor, the fissionable material gradually becomes spent and must be removed along with other radioactive byproducts. Since the spent fuel contains fission by products which are highly radioactive and which generate large amounts of heat, the spent fuel is usually temporarily stored in the reactor&#39;s spent fuel pool. The spent fuel pool is a pool of water of sufficient volume to prevent the escape of harmful radiation and to absorb and dissipate the heat generated by the decaying fissionable material. Alternatively, the spent fuel may be temporarily stored in a hot cell. A hot cell refers to a heavily shielded structure having the capability to prevent the escape of harmful radiation, while absorbing and dissipating the heat generated by the spent fuel. 
   Generally, there is limited storage space in a nuclear reactor&#39;s spent fuel pool or in its hot cell. Thus, the spent fuel must be moved to a storage site to make room for additional spent fuel. In some cases, there is a desire to shut the nuclear reactor down and remove all fissionable material, in which case, all of the fissionable material must be removed to a storage site. Conventionally, spent nuclear fuel has been stored at various locations across the country. Spent nuclear fuel has been transported by storing it in small groups using multiple fuel storage drums. The spent fuel may be transported in the form of spent fuel rods or in the form of rubble. Conventionally, spent fuel rod assemblies have been transported in fuel transportation containers designed for undamaged fuel rod assemblies. The foregoing attempted solution, however, has required that substantially fewer failed fuel rod assemblies be transported per container, compared to the number of undamaged fuel rod assemblies that can be transported in the same container. By transporting fewer failed fuel rod assemblies, even if some fissionable material escapes from the failed fuel rods and accumulates near other fissionable material in the container, there is not enough fissionable material in the entire container to pose a significant risk of criticality. The problem with the foregoing solution, though, is it wasteful of resources, because significantly fewer failed fuel rod assemblies can be transported per container relative to the number of undamaged fuel rod assemblies that can be transported in the same container. 
   Another, attempted solution has been to transport failed fuel rod assemblies in fuel transportation containers designed for transporting fissionable material in the form of rubble. That is, the fissionable material is not in the form of rods, but is in the form of small particles. Thus, the failed fuel rods are broken up into rubble, and placed in the container. The problem with this solution, however, is that the method is inefficient for three principle reasons. First, the failed fuel rod assemblies be broken up. Second, such containers are capable only of transporting comparatively few failed fuel rod assemblies. Finally, the transportation container is only designed for transportation, not storage. Thus, once the fissionable material has been transported to another location, the container must be unloaded in a fuel pool or in a hot cell, and other arrangements made to store the fissionable material. 
   The other major problem with transporting spent nuclear fuel is that United States law imposes stringent safety requirements even on containers used to transport undamaged fuel rod assemblies. The relevant law imposes significantly more restrictive requirements with respect to the transportation of spent nuclear fuel across areas accessible to the public, as opposed to areas inaccessible to the public. 
   State of the art spent fuel transportation containers for areas accessible to the public are casks with individual compartments. The fuel rod assemblies are loaded into individual compartments in the casks in a spent fuel pool or a hot cell. The purpose of the individual compartments within each cask is to ensure sufficient spacing between adjacent fuel rod assemblies to avoid any danger of criticality. The fuel rod assemblies are loaded into the cask in a spent fuel pool or hot cell. Upon reaching the storage location, the fuel rod assemblies must be removed from the cask in a spent fuel pool or hot cell, and then stored. 
   In contrast, state of the art spent fuel transportation containers for areas inaccessible to the public are typically a sealed canister placed within a cask. The fuel rod assemblies are loaded into individual compartments in a canister in a spent fuel pool or a hot cell. The canister is then sealed and placed in a cask. When the cask/canister assembly reaches the storage site, the canister is removed from the cask, stored, and the cask may be reused, which is a much more efficient process. 
   Nonetheless, the cask/canister method cannot be used for transportation in areas accessible to the public because they fail to meet the requirements imposed by U.S. law. Whether the spent fuel is transported by cask or a sealed canister within a cask, there is a significant need for the casks to be transported in a safe and efficient manner so as to eliminated the possibility of hazardous materials leaking into the environment. Accordingly, there is a need for an invention that provides for the transportation and storage of spent fuel rod assemblies, and for a cask/canister device for the transportation and storage of spent fuel across areas accessible to the public. The present invention provides a solution, wherein a existing casks can be used and can be safely transported resulting in much greater efficiency in the transportation over public thoroughfares and storage of spent nuclear fuel. 
   SUMMARY OF THE INVENTION 
   The invention provides an apparatus for safely transporting spent nuclear fuel and other hazardous materials via rail transport. The system in accordance with the invention includes a transportation cradle that is mountable onto a railcar. The cradle in accordance with the invention is configured so as to securely receive and hold a cask containing spent nuclear fuel or other hazardous materials. The railcar is specifically designed and tested to meet AAR requirements for the transportation of spent nuclear fuel. 
   The cradle in accordance with the invention includes the main structure of the cradle which supports the dead weight and dynamic loads from the transportation cask, restraining members which restrain the transportation cask from an upward movement as well as horizontal movements, and a rotational support member which allows the transportation cask to be placed in the vertical position onto the cradle and rotated to the horizontal position for final transportation. The main structure of the cradle supports both the weight of the cask as well as the dynamic loads that will be experienced during transportation of the cask. The restraining members are designed to provide adequate support to protect the cask including protection to the cask from the cradle allowing the cask to be exposed to loads in excess of the maximum cask design load (i.e., The restraining members will fail at a lower force than the maximum design force for the cask which will allow the impact absorbers located on the ends of the cask to prevent the cask from receiving a force greater than the design of the cask itself.). Thus, the cradle design provides support to protect the spent fuel transportation cask and also to protect the cask should it be exposed to loads that would exceed the design load for the cask. In accordance with the invention, the cradle will be secured to the railcar in four locations to accommodate the camber in the railcar flatbed. This will reduce potential failure of the cradle to railbed connection. 
   The railcar in accordance with the invention is designed with high structural safety margins in the railcar body and railcar trucks, high precision railcar trucks and brakes to assure performance safety and reliability, and a performance monitoring system to allow for early warning of potential structural or performance problems. The monitoring system in accordance with the invention provides early warning to the train crew of component or performance degradation to assure pro-active actions prior to failure. The railcar monitoring system in accordance with the invention includes the monitoring and recording of the following factors: railcar speed, truck movement, rocking, wheel flats, bearing conditions, braking performance, as well as vertical, lateral and longitudinal acceleration. By monitoring and recording each of these factors, the pro-active actions can be taken to prevent railcar and/or cradle failures that could increase the risk of damage to the spent nuclear fuel cask. 
   The cradle and railcar in accordance with the invention are designed together so as to provide a high level of assurance against structural failure of the railcar and cradle combination. 
   Thus, the invention provides transportation cask cradle that includes a front cradle section load bearing brace, the load bearing brace including a first and second opposing end portions, a rear cradle section having a first non-loading bearing brace and a second non-loading brace, the first non-load bearing brace having a first top section and the second non-load bearing brace having a second top section, the first and second top sections opposing each other, first and second horizontal support members connecting the front cradle section to the rear cradle section and a first trunnion disposed on the first top section of the first non-load bearing brace and a second trunnion disposed on the second top section of the second non-load bearing brace. 
   The invention also provides a nylon bearing surface affixed to load bearing brace as well as a stop bar affixed to the load bearing brace to prevent longitudinal movement of the cask. 
   The invention further includes a plurality of base members disposed on a bottom surface of the cradle, the base members allowing the transport cradle to be affixed to a vehicle surface. 
   The invention also provides an uplift prevention device affixed to the first top section of the first non-load bearing brace and the second top section of the second non-load bearing brace which prevents upward (vertical) movement of the cask. 
   The invention also provides a railcar for transporting hazardous materials that includes a depressed flatbed disposed on a planar surface of the railcar, at least one retaining bracket disposed on the depressed flat bed, the at least one retaining bracket configured so as to facilitate coupling with a transportation cradle, as described above. In accordance with the invention, the railcar may also include braking performance sensors dispose at each end of the railcar which gather data related braking of the railcar. In accordance with the invention, the railcar may also include sensors for truck hunting, rocking and vertical, lateral and longitudinal acceleration, whereby the sensors are disposed at a middle section of the railcar. In accordance with the invention, the railcar may also include a Global Positioning Satellite (GPS) sensor disposed at a front section of the railcar. In accordance with the invention, the railcar may also include a plurality of wheel bearing sensors corresponding to each of the wheel bearing assemblies. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention. Together with the written description, these drawings serve to explain the principles of the invention. In the drawings: 
       FIG. 1  illustrates a perspective view of a cradle for transporting spent nuclear fuel in accordance with an embodiment of the invention; 
       FIG. 2  illustrates a perspective view of the cradle in accordance with an embodiment of the invention; 
       FIG. 3  illustrates a cask including pocket trunnions; 
       FIG. 4  illustrates a flatbed rail car for receiving the cradle in accordance with the invention; and 
       FIG. 5A  illustrates a top view of a flatbed rail car with various monitoring components in accordance with an embodiment of the invention; and 
       FIG. 5B  illustrates a side view of a flatbed rail car with various monitoring components in accordance with an embodiment of the invention 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a perspective view of a cradle  100  for transporting spent nuclear fuel or other hazardous materials in accordance with an embodiment of the invention. As will be described in greater detail below, the cradle  100  is configured to securely receive a spent fuel transportation cask (not shown in  FIG. 1 ).  FIG. 1  shows a front cradle section  105  and a rear cradle section  110 . The front cradle section  105  is connected to the rear cradle section  110  via a first horizontal support  130  and a second horizontal support  125 . The first horizontal support  130  and the second horizontal support  125  provide support and stability to the cradle  100 . The front cradle section  105  includes a front load bearing brace  115 . The front load bearing brace  115  has a semicircular shape to accommodate the shape of the transportation cask. The front load bearing brace  115  has a nylon bearing surface (not visible in  FIG. 1 ) on its top surface that provides bearing surface for the cask. Thus, the nylon bearing surface is affixed or coated onto the surface of the front load bearing brace  115  that comes into contact with the transportation cask. The nylon coated front load bearing brace  115  provides a durable surface onto which the transportation cask can be placed. The rear cradle section  110  includes a first rear brace  120  and a second rear brace  126 . The rear braces  120  and  126  are not load bearing and do not come into contact with the transportation cask, however, they do provide structural support for the cradle  100 . As shown in  FIG. 1 , a second planar base  135  is disposed between the first and second rear braces  120  and  126 . The second planer brace  135  provides additional structural support for the cradle but does not contact the transportation cask. 
   As shown in  FIG. 1 , a first planer base  150  is disposed adjacent the front load bearing brace  115 . The first planar base also does not contact the transportation cask. 
   As shown in  FIG. 1 , the rear cradle section  110  also has a first trunnion  160  and a second trunnion  165  which face each other and project toward each other. The first trunnion  160  is located at a top end of the first rear brace  120  and the second trunnion  165  is located at a top end of the second rear brace  126 . The trunnions  160  and  165  project inward with reference to the cradle  100  so that they can connect and lock into the transportation cask when it is mounted onto the cradle  100 . The trunnions  160  and  165  are, thus, in contact with transportation cask and provide support for the rear of the transportation cask. The trunnions  160  and  165  provide openings which can ‘catch’ pocket trunnions which are located on the surface of the transportation cask and thus, hold the transportation cask in place. The trunnions  160  and  165  support the weight of the transportation cask and prevent upward movement of the rear portion of the transportation cask. When the transportation cask is first lowered onto the cradle  100 , the trunnions  160  and  165  first receive the transportation cask and the cask when then rotated downward and 90° so that the front of the transportation cask rests on the nylon coated front load bearing brace  115  of the front section of the cradle  105 . 
     FIG. 1  also shows base members  190 ,  195  and  198  located at the base of the cradle  100 . The base members  190 ,  195  and  198  are located near the corners of the base of the cradle  100 . A fourth base member is also present, but not clearly visible in  FIG. 1 . Each base member  190 ,  195  and  198  has corresponding lug  192 ,  197  and  199 . The fourth base member that is not shown also has a lug. The lugs  192 ,  197  and  199 , which are shaped like a dowel or pin, allow the cradle  100  to be mounted and affixed to the top surface of a railcar or other transport vehicle. 
   Thus, the cradle  100  is configured to receive a spent fuel transportation cask that can be lowered into the cradle  100 . When placed into the cradle  100 , the transportation cask is in contact with the cradle  100  at the bearing surfaces that coat the front load bearing brace  115  located at the front cradle section  110 . The transportation cask is also in contact with the trunnions  160  and  165  on the rear section  110  of the cradle  100 .  FIG. 1  also shows a curved stop bar  187  which is formed as a lip adjacent the outer surface of the front load bearing brace  115 . The curved stop bar  187  prevents the transportation cask from moving in the forward longitudinal direction. In addition, the trunnions  160  and  165  located at the rear of the cradle prevent the transportation cask from moving in the reverse longitudinal direction. 
     FIG. 2  shows the cradle apparatus in accordance with the invention.  FIG. 2  includes the elements of shown in  FIG. 1 , but also includes an uplift prevention device  280 . The uplift prevention device  280  is mounted onto the cradle  100  via lugs  270  and  275 . The lug  270  is located near an upper section at one end of the front load bearing brace  115  and the lug  275  is located near an upper surface at the opposite end of the front load bearing brace  115 . The uplift prevention device  280  is put into place after the transportation cask is placed into the cradle  100 . The uplift prevention device  280  acts as a retaining element to restrain the transportation cask. Thus, it assists with maintaining the placement of the transportation cask and also prevents upward movement of the transportation cask. The uplift prevention device  280  may be made of any durable material that will effectively restrain the movement of the transportation cask. The material may be rigid or alternatively may be flexible. 
     FIG. 3  shows an exemplary transportation cask  300  that may be lowered into the cradle  100 . The transportation cask  300  includes two pocket trunnions. A first pocket trunnion  310  is disposed at an end of the transportation cask  300 . The second pocket trunnion is not visible in  FIG. 3 , but is located at the opposite side of the first pocket trunnion  310  so that the first and second pocket trunnions are opposing. The pocket trunnions include notch-like openings that can receive the trunnions  160  and  165  (shown in  FIG. 1 ). In this manner, the transportation cask  300  will be locked into place in the cradle  100 . The transportation cask  300  may also include impact absorbers which reduce the transference of shocks to the transportation cask  100  during movement. These impact absorbers may be located at any point on the outer surface of the transportation cask  300 . For example, in the embodiment of  FIG. 3 , impact absorbers  320  and  325  are disposed at the ends of the transportation cask  300 . 
   In accordance with the invention, the cradle  100  is configured so as to be placed on the railcar for transport.  FIG. 4  shows a depressed center  410  of a flatbed rail car  400 . The cradle  100  (shown in  FIGS. 1 and 2 ) is placed and fitted onto the depressed center  410 . The depressed center  410  also has four retaining brackets which couple with the cradle  100  so as to secure the cradle  100  to the flatbed rail car  400 .  FIG. 4  shows two of the retaining brackets  420  and  430 . Two additional retaining brackets (not shown in  FIG. 4 ) are positioned opposing the retaining brackets  420  and  430 . The retaining brackets are configured so as to mate with the base members of the cradle  100  via lugs. Thus, the retaining bracket  420  is secured to the base member  195  via lug  197  (shown in  FIG. 1 ) and retaining bracket  430  is secured to base member  190  via lug  192  (shown in  FIG. 1 ). 
   Thus, the connection between the cradle  100  and depressed center flatbed railcar  420  utilizes round lug pins. The lug pins at the front and rear of the cradle  100  are fixed in the base members located on the bottom surface of the cradle and the retaining bracket. The retaining brackets, when mated to the base members, allows only rotational movement of the cradle  100  at this connection (i.e. no horizontal or vertical movement). The retaining brackets on the railcar at front section of the cradle  100  also only allow rotational movement with no vertical or horizontal movement. However, the retaining brackets on the rear (trunnion end) of the railcar  400  are slotted allowing both rotational and horizontal movement and no vertical movement. This design allows for deflection in the railcar bed camber without applying additional load or stress onto the cradle. 
   The cradle  100  shown in  FIGS. 1 and 2  may be constructed of durable metals such as carbon and alloy steels which provide strength with some flexibility, along with applicable paints and coatings for corrosion resistance. All structural steel plates will be ASTM A514 Grade 100 and the trunnions and trunnion housing plates will be constructed of Inconel 718. The weld electrodes will be AWS 5.5 E11018-X for A514 Grade 100 steel. 
   The railcar  400  also provides certain features beyond conventional railcars that enhance its safety which is a significant issue when transporting spent nuclear fuel. These features include electronic braking, superior suspension and sway control systems, and a performance monitoring system to allows early detect of degradation in the railcar performance which will identify railcar component degradation prior to component failure. Electronic braking allows for more even braking of the railcars which reduces dynamic loading that can occur with conventional railcar braking. The superior suspension and sway control provides a smoother and less rocking type ride which will limit the total overall swaying movement of the railcar. 
   The performance monitoring system incorporated into the railcar will provide real time monitoring when operating in the dedicated-train mode. The performance monitoring system collects and stores various data relating to the operation of the railcar. The data will be retrievable both in the passenger car and remotely. The system will produce exception reports when parameters exceed established setpoints. The exception reports will alarm in the passenger car and then be transmitted to the train crew in the engine. 
   The monitoring system will store time-history data for the parameters monitored. The storage media will be capable of storing the data for continuous operation of the train for 14 days. The media will be retrievable for review and archiving. 
   The monitoring system in accordance with the invention will include the following:
         1. Location Detection—A GPS will be included to identify the location of each of the railcars. The system will be capable of providing real-time, continuous location capabilities and be capable of being monitored locally in the train passenger car and at remote locations. A power supply will be provided that will allow a minimum of thirty (30) days operation without power from the locomotive or other power supply external to the railcar.   2. Speed—The train speed will be monitored both real-time and time-history. The system will allow for train speed monitoring both in the train passenger railcar and at remote locations. This will be accomplished utilizing the GPS and the wheel bearing speed monitor.   3. Odometer—An odometer will be provided on each railcar to log the total distance traveled by the railcar. This will be accomplished utilizing the wheel bearing monitor.   4. Truck Hunting—Lateral movement of the railcar body will be monitored to determine lateral instability. The data will be taken in real-time and recorded as time-history. An alarm will be initiated when the lateral movement has a sustained real-time RMS lateral railcar body acceleration of 0.26 g sustained for 10 seconds. The signal will be transmitted to the train crew. This will be accomplished utilizing accelerometers.   5. Rocking—Side-to-side movement of the railcar body will be monitored to determine the side-to-side roll angles. The data will be taken in real-time and recorded as time-history. An alarm will be initiated when the monitor has a real-time peak-to-peak roll angle of five (5) degrees for three (3) cycles.   6. Wheel Flats—Vertical movement of the wheels will be monitored to determine flat spots on the wheels. The data will be taken in real-time and recorded as time-history. This will be accomplished utilizing accelerometers in the wheel bearings.   7. Bearing Condition—Wheel bearing temperatures will be monitored along with bearing vibrations to determine bearing condition. The data will be taken in real-time and recorded as time-history.   8. Braking Performance—Brake line pressure will be monitored at the auxiliary and emergency reservoirs, and in the air piping to the brake cylinder. The brake cylinder position will also be monitored. The data will be taken in real-time and recorded as time-history.   9. Vertical Acceleration—Vertical movement of the railcar body will be monitored. The data will be taken in real-time and recorded as time-history. An alarm will be initiated for a peak vertical acceleration of the railcar body of 1.0 g. This will be accomplished utilizing accelerometers.   10. Lateral Acceleration—Lateral movement of the railcar body will be monitored. The data will be taken in real-time and recorded as time-history. An alarm will be initiated for a peak lateral acceleration of the railcar body of 0.75 g. This will be accomplished utilizing accelerometers.   11. Longitudinal Acceleration—Longitudinal movement of the railcar body will be monitored. The data will be taken in real-time and recorded as time-history. An alarm will be initiated for a peak lateral acceleration of the railcar body of 1.5 g. This will be accomplished utilizing accelerometers.       

     FIGS. 5A and 5B  shows the location of the various data gathering components described above.  FIG. 5A  is a top view of a railcar  500 , the railcar having monitoring system in accordance with the invention.  FIG. 5A  shows that the braking performance sensors  505  are located on a both ends of side of the railcar, while the sensors for truck hunting, rocking and vertical, lateral and longitudinal acceleration  510  are located in the middle section of the railcar, i.e., the depressed center of the railcar.  FIG. 5A  also shows that a GPS  515  is located near the front section of the railcar.  FIG. 5B  provides a side view of the railcar which also illustrates the locations of the braking performance sensors  505 , the sensors for truck hunting, rocking and vertical, lateral and longitudinal acceleration  510  and the GPS  515 . In addition,  FIG. 5B  also shows a plurality of wheel bearing sensors  520  located at the wheel bearings of each wheel on the railcar. In this manner, multiple parameters impacting the safety of the railcars is monitored. 
   The foregoing description of the preferred embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching.