Patent Publication Number: US-11031149-B1

Title: Nuclear abrasive slurry waste pump with backstop and macerator

Description:
This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 62/630,026 filed Feb. 13, 2018, which is incorporated by reference in its&#39; entirety. 
    
    
     FIELD OF INVENTION 
     This invention relates to the retrieving of chemical, radioactive, hazardous and/or other waste and/or material from storage tanks; and in particular, to nuclear waste slurry pump systems, devices, and methods for retrieving waste materials and/or other material from storage tanks with liquefied tank material, the systems, devices and methods can work with tanks having high temperature conditions up to approximately 212 degrees Fahrenheit or low temperature conditions down to approximately 32 degrees Fahrenheit. 
     BACKGROUND AND PRIOR ART 
     At nuclear waste storage facilities, radioactive material is stored in underground storage tanks. These tanks typically have small openings down to 12″ in diameter for access of equipment. Various cleaning methods have been used to break up and retrieve waste material located in these tanks. A high flow of water liquefies and motivates waste into a stream. Typically, a pump sits in the stream to capture and transfer the waste to a remote storage tank. Traditional abrasive slurry pumps are sized to keep fluid velocities at a minimum, thus reducing wear on the pump. 
     However, these pumps are too large to fit through a 12-inch diameter riser pipe. To fit, the pump can be reduced in size, but this also reduces the pump output and won&#39;t meet flow requirements to prevent solids from settling during transfer. To make up for the decreased flow rates, the pump can be sped up; however, this causes excessive wear on the pump. 
     Also, when a stream of waste is flowing towards the pump, a large portion of the liquid and particles can flow past the pump. Once the stream passes the pump, multiple steps must be implemented to properly capture the waste greatly increasing operation costs and the overall time to effectively clean a tank. 
     Furthermore, particles in the abrasive slurry can be too large to pass into the pump requiring additional methods or operational time to remove. 
     Thus, the need exists for solutions to the above problems with the prior art. 
     SUMMARY OF THE INVENTION 
     A primary objective of the invention is to provide nuclear abrasive slurry waste pump systems, devices, and methods for retrieving waste materials and/or other material from storage tanks with liquefied tank material. 
     A secondary objective of the invention is to provide pumping solution systems, devices and methods for the removal of liquid and solid waste from nuclear waste tanks through existing riser pipes approximately 12-inch in diameter. Keeping solids suspended in the waste stream as it is pumped out of a tank requires a high-power density, which this invention achieves via a 4-stage, hydraulically-driven pump. 
     A third objective of the invention is to provide hydraulically driven pump systems, devices, and methods which eliminate an ignition source and potential in-tank explosion that is associated with electrical power. 
     The pump hydraulic motor can be located on the pump within the tank, which allows for the mechanical seals separating the hydraulic fluid from the waste stream to also be located in the tank, eliminating the possibility of hazardous or nuclear waste leaking out and being transported above ground through the hydraulic system in the event of a seal failure. 
     In case of a leak at the mechanical seals, the seal housing has windows to allow for any waste to leak back into the tank and not leak across the bearing housing seal faces and into the hydraulic motor. 
     Mechanical seals are used to prevent radioactive fluid from leaking into the hydraulic fluid. Because the mechanical seals must remain operational for the life of the pump, barrier fluid is provided at the seal faces to cool and lubricate, and thus, reduce wear. Barrier fluid becomes hot as it is circulated around the seals, which limits its ability to reduce wear. A helical heat exchanger to cool the barrier fluid is integrated around the discharge piping. 
     In tanks with large amounts of liquid waste the pump must be fully submerged. This causes an increase in differential pressure between the waste and the seal barrier fluid. To keep a positive differential pressure between the waste and the barrier fluid, an accumulator has a piston which compensates pressure in the barrier fluid providing the positive pressure to prevent radioactive material from entering the system. 
     The portions of the pump that will become wetted when the pump is submerged are constructed out of stainless steel to prevent rust, corrosion, and allow for decontamination. Fasteners used have a 12-point socket head to limit the pockets on the machine to prevent waste from accumulating, to further help with decontamination when removing equipment for disposal. 
     Operation of the pump can be controlled by a hydraulic power unit located outside of the tank. The onsite radioactive transport piping attached to the discharge of the pump system has pressure requirements that must not be exceeded. The hydraulic power unit oil pump is displacement limited to prevent the pump from creating enough pressure to exceed the discharge piping requirements. 
     When the pump is stopped, the abrasive waste in the line drains back into the pump. This can cause abrasive particles to become wedged in the small spaces between impellers and housings. Hardened impellers are used to prevent the particles from jamming the pump. 
     Being designed for a radioactive environment requires the pump to be installed for the duration of a tank campaign. Because no maintenance may be performed during that time, greased bearings are used to ensure proper function for the full campaign. 
     Many of the tanks have flat bottoms; therefore, reducing the waste level to an acceptable volume requires the drawdown capability of the pump to be less than approximately ½-inch of liquid. This invention incorporates a flat shaped inlet at the suction end, mounted very close to the base of the pump, that allows a pump drawdown of approximately ⅜″. 
     For pumping thicker liquids, dilution ports are provided at the pump suction to add water to the waste stream to meet the criticality required for the waste. 
     The system includes an integrated, retractable backstop that captures and directs the flow of the waste liquid into the pump suction for flat bottom tanks. The backstop also reduces the number of particles that bypass the pump suction and therefore increases the overall efficiency of the pumping system. The backstop can also be rotated to align with the flow stream and so the suction of the pump can be de-fouled with the cleaning nozzle. 
     A suction strainer with ⅜-inch openings is typically provided with the pump to classify particles and meet the disposal processing requirements to prevent larger particles from entering the pump suction. 
     The system can also include an integrated macerator beneath the pump suction to breakdown and classify particles prior to the waste liquid entering the suction strainer. The macerator works in concert with the rotatable pump backstop to improve the volume of waste material that can be captured by the pump. The macerator can swing out of the way when not needed or it becomes fouled to increase pumping performance. 
     Further objects and advantages of this invention will be apparent from the following detailed description of the presently preferred embodiments which are illustrated schematically in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The drawing figures depict one or more implementations in accord with the present concepts, by way of example only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements. 
         FIG. 1  is a perspective/isometric view of the nuclear abrasive slurry waste pump assembly and hydraulic power unit. 
         FIG. 2  is an enlarged view of the nuclear abrasive slurry waste pump assembly shown in  FIG. 1  along with the macerator rotation. 
         FIG. 3A  is a perspective view of the pump backstop portion of the nuclear pump assembly of  FIG. 2  in a closed position. 
         FIG. 3B  is another view of the pump backstop portion of the nuclear pump assembly of  FIGS. 2 and 3A  with the pump backstop in an open position, and which illustrates the range of motion of the pump backstop. 
         FIG. 4  is a cross-sectional view of the accumulator portion of the nuclear abrasive slurry waste pump assembly of  FIG. 2 . 
         FIG. 5  is an enlarged partial cross-section view of the first stage pump of  FIG. 2 . 
         FIG. 6  is a schematic of the barrier fluid recirculation, cooling circuit that can be used with pump assembly  1  of  FIGS. 1 and 2 . 
         FIG. 7  illustrates a cross section view of a waste tank and the nuclear abrasive slurry waste pump of  FIG. 2  installed in a typical riser. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before explaining the disclosed embodiments of the present invention in detail it is to be understood that the invention is not limited in its applications to the details of the particular arrangements shown since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation. 
     In the Summary above and in the Detailed Description of Preferred Embodiments and in the accompanying drawings, reference is made to particular features (including method steps) of the invention. It is to be understood that the disclosure of the invention in this specification does not include all possible combinations of such particular features. For example, where a particular feature is disclosed in the context of a particular aspect or embodiment of the invention, that feature can also be used, to the extent possible, in combination with and/or in the context of other particular aspects and embodiments of the invention, and in the invention generally. 
     In this section, some embodiments of the invention will be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in alternative embodiments. 
     A list of components will now be described.
       1  Hydraulic pump/pump assembly     2  hydraulic power unit     3  accumulator     4  hydraulic motor     5  dilution line     6  seal housing     7  pump backstop     8  suction strainer     9  macerator     10  bladder     11  expansion cavity     12  piston     13  spring     14  pump shaft     15  pump bowl     16  carbide wear ring     17  impeller     18  discharge piping     19  barrier fluid heat exchanger     20  mechanical seal     21  riser pipe     22  waste tank     23  12 point bolt     24  Hex head cap screw     25  Hydraulic supply hose     26  Hydraulic return hose   

       FIG. 1  is a perspective/isometric view of the nuclear abrasive slurry waste pump assembly  1  connected to hydraulic power unit  2  via a hydraulic supply hose  25  and a hydraulic return hose  26 .  FIG. 2  is an enlarged view of the nuclear abrasive slurry waste pump assembly shown  1  in  FIG. 1  along with the macerator rotation. 
     Referring to  FIG. 1  and  FIG. 2 , the nuclear abrasive slurry waste pump system can be comprised of a pump  1  with backstop  7  and macerator  9  with control from a hydraulic power unit  2 . The wetted components of the pump  1  can be constructed from metal such, as but not limited to stainless steel to prevent corrosion and allow for decontamination. Where feasible, bolts, such as 12 point bolts  23  or hex head cap screws  24 , that do not have an internal feature in the head can be used to prevent the buildup of hazardous waste. The use of hydraulic power can remove any potential ignition sources from electrical components that can occur with prior art systems and allows operation in tanks with explosive vapors. 
     Referring to  FIG. 2 , the nuclear abrasive slurry waste pump assembly  1  can be comprised of a multistage pump driven by a hydraulic motor  4  that can be stacked vertically to fit through an approximately 12-inch riser pipe. At the suction end of the pump can be a strainer  8  that prevents particles larger than approximately ⅜-inch in diameter from entering the pump. The face of the suction inlet can allow for a low draw down of the liquid level to an approximately ½-inch or less in the tank. For difficult liquids with high solid content, a dilution liquid can be introduced through dilution lines  5  and feed ports incorporated into the face of the suction inlet. 
       FIG. 5  is an enlarged partial cross-section view of the first stage pump of  FIG. 2 .  FIG. 5  illustrates a single pump stage that can be comprised of an impeller  17  rotating in a bowl  15  where the suction inlet of the first stage draws liquid into the pump and directs flow into the suction of the adjacent stages until the final stage which pumps the liquid into the discharge piping  18 . The pump impellers  17  can have hardened faces that rotate in wear rings  16 , such as hardened carbide wear rings which can prevent particles from becoming wedged in between the two and seizing the pump. The impellers can be coupled through a common shaft  14  that is driven by the hydraulic motor  4 . The drive shaft can be supported by bearings and connected to the motor through a flexible coupling. The bearings can be greased such that there is no need for additional maintenance or lubrication during the life of the pump. 
     Referring to  FIGS. 1 and 2 , the pump hydraulic motor  4  can be located above the pump, mounted to the seal housing  6  such that it is separated from the waste stream through mechanical seals, thereby eliminating the possibility of nuclear waste contaminating the hydraulic system and reaching outside of the tank. In case of a leak at the mechanical seals, the seal housing  6  can have ports or windows  6 PW to allow any waste to drain back into the tank. 
       FIG. 6  is a schematic of the barrier fluid recirculation, cooling circuit that can be used with pump assembly  1  of  FIGS. 1 and 2 . Referring to  FIGS. 1, 2 and 6 , the mechanical seals  20  can contain a barrier fluid at the seal faces to reduce heat from friction and reduce wear on the seals. The barrier fluid can be circulated around the seals  20  and cooled through a barrier fluid heat exchanger  19  to improve the performance and increase the life of the seals. The heat exchanger  19  can be comprised of a helical path traversing the outside diameter of the discharge piping  18 . 
       FIG. 4  is a cross-sectional view of the accumulator portion  3  of the nuclear abrasive slurry waste pump assembly  1  of  FIG. 2 .  FIG. 4  references an accumulator  3  that can be comprised of a chamber with expansion cavity  11  housing a rolling bladder  10 , piston  12 , and spring  13  that self-compensates for changes in the barrier fluid due to temperature and/or pressure. 
     To further improve the efficiency of the pumping system, a macerator  9  of  FIG. 2  can be mounted at the suction inlet to draw in large particles, break them down to approximately ⅜-inch diameter or less, and deposit them at the suction of the pump. This can reduce the need for further processing by a cleaning nozzle and eliminates the possibility of a clogged suction. 
     The bottom of the macerator  9  can be actuated to evacuate any debris that has collected. Additionally, the macerator can be rotated out of the way in the event it becomes inoperable, for cleaning, or if not being employed at all. When the macerator  9  is rotated away, the nuclear abrasive slurry waste pump assembly  1  is still operable with the suction strainer to classify the particle size to approximately ⅜″ or smaller. 
     Referring to  FIGS. 1 and 2 , a retractable backstop  2  can be incorporated at the suction inlet to increase the pump&#39;s efficiency by collecting matter that would otherwise bypass the pump assembly  1 . 
       FIG. 3A  is a perspective view of the pump backstop portion  7  of the nuclear pump assembly  1  of  FIG. 2  in a closed position.  FIG. 3B  is another view of the pump backstop portion  7  of the nuclear pump assembly  1  of  FIGS. 2 and 3A  with the pump backstop  7  in an open position, and which illustrates the range of motion of the pump backstop  7 . 
     Referring to  FIGS. 3A-3B , the backstop  7  can be comprised of wings that closely wrap around the circumference of a strainer for deployment through an approximately 12-inch diameter riser.  FIG. 3B  also shows the wings deployed after the nuclear abrasive slurry waste pump assembly  1  is installed into the riser pipe. 
     In one embodiment, the backstop  7  can be rotated independently about the pumps longitudinal axis to allow alignment with the flow of liquid. In another embodiment, the backstop  7  can be rotated with the pump as whole. 
     The backstop  7  can be raised and lowered to accommodate the strainer or the macerator  9  ( FIG. 2 ). Also, the backstop  7  can be fully raised to allow for complete 360 degree access to the suction or to be cleaned by spray water. 
     Referring to  FIGS. 1-2 , the hydraulic power unit  1  can be comprised of a skid mounted pumping system that delivers hydraulic fluid to the hydraulic motor  4 . The hydraulic supply pump assembly  1  can be hydraulically displacement limited to specific piping runs by a mechanical stop so that the nuclear abrasive slurry waste pump hydraulic motor  4  cannot over pressurize the discharge piping, thus keeping the system discharge pressure between approximately 0 psi and approximately 500 psi, and thus, within safe operating conditions for specific piping being used to transport the waste, and preventing protecting the piping from failures. 
       FIG. 7  illustrates a cross section view of a waste tank and the nuclear abrasive slurry waste pump of  FIG. 2  installed in a typical riser. 
     Referring to  FIGS. 1, 2 and 7 , the nuclear abrasive slurry waste pump assembly  1  with backstop  7  and macerator  9  is shown installed through an approximately 12-inch riser pipe  21  in a generic waste tank  22 . 
     The term “approximately” can be +/−10% of the amount referenced. Additionally, preferred amounts and ranges can include the amounts and ranges referenced without the prefix of being approximately. 
     While the invention has been described, disclosed, illustrated and shown in various terms of certain embodiments or modifications which it has presumed in practice, the scope of the invention is not intended to be, nor should it be deemed to be, limited thereby and such other modifications or embodiments as may be suggested by the teachings herein are particularly reserved especially as they fall within the breadth and scope of the claims here appended.