SYSTEMS AND METHODS FOR DISMANTLING A NUCLEAR REACTOR
Systems and methods for dismantling a nuclear reactor are described. In one aspect the system includes a remotely controlled heavy manipulator (“manipulator”) operatively coupled to a support structure, and a control station in a non-contaminated portion of a workspace. The support structure provides the manipulator with top down access into a bioshield of a nuclear reactor. At least one computing device in the control station provides remote control to perform operations including: (a) dismantling, using the manipulator, a graphite moderator, concrete walls, and a ceiling of the bioshield, the manipulator being provided with automated access to all internal portions of the bioshield; (b) loading, using the manipulator, contaminated graphite blocks from the graphite core and other components from the bioshield into one or more waste containers; and (c) dispersing, using the manipulator, dust suppression and contamination fixing spray to contaminated matter.
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This application claims the benefit of U.S. patent application Ser. No. 12/967,068 filed Dec. 14, 2010 and Provisional Application No. 61/318,288 filed Mar. 27, 2010, both titled “Systems and Methods for Dismantling a Nuclear Reactor,” the disclosures of which are herein incorporated by reference in their entirety.
GOVERNMENT LICENSE RIGHTSThis invention was made with government support under Contract No. 130529, awarded by the U.S. Department of Energy. The Government has assigned No. S-126,321 to this invention. The government has certain rights in the invention.
BACKGROUNDDuring the era when many nuclear reactor plants were constructed, techniques to decommission the nuclear reactors were generally not fully considered. Thus, many nuclear reactors were constructed without giving any consideration to dismantling the reactors at a future time.
One exemplary technique for decommissioning a nuclear reactor is via a “water platform” method, whereby the top of the reactor vessel is removed and the vessel is filled with water to provide a radioactive shield relative to the internal components of the reactor. A platform is placed on top of the water to provide access to reactor's internal components immediately underneath the platform. At this point, underwater cutting is performed on the portions of the reactor's internal components located immediately beneath the platform. The cut pieces are then loaded onto the platform and transferred to either a “wet cutting station” in which further underwater cutting is performed or a “dry cutting station” in which further cutting is performed in an air-controlled environment. The water level is then decreased, the platform lowered, and the cutting process is again initiated. This sequence of events is repeated until all of the reactor's internal components are removed. Thereafter, the cutting of the reactor vessel itself is initiated.
The water platform methodology is substantially limited in that it may result in human worker interaction with the sectioned reactor internal components, for example, during transfer of sectioned reactor components between the water platform and the wet/dry cutting stations. Additionally, the cutting process usually produces a significant amount of particles whereby respirators and HEPA ventilation are sometimes necessary to combat the effects of airborne contamination. Furthermore, the “shielding” water in the vessel will absorb particles produced during the cutting process whereby constant circulation and filtration of this fluid is necessary to remove liquid radioactive waste.
An alternate method of decommissioning a nuclear reactor was used on a retired nuclear reactor at the Shippingport Power Plant. The Shippingport nuclear reactor was an offspring of the Eisenhower presidency and thus its decommissioning was orchestrated by the United States Department of Energy. In decommissioning this unit, the reactor vessel was filled with concrete and then moved in one piece to a disposal site. The Shippingport reactor, which was rated at 72 megawatts, was significantly smaller than most of the commercial nuclear reactors in use or construction today. Nonetheless, the weight of the reactor when filled with concrete required the fabrication of special lifting equipment to lift the reactor from its underground housing. More particularly, the project required the erection of a gigantic frame, the construction of four huge hydraulic jacks, each having an approximately 6,000 ton lifting capacity, and the mounting of these jacks on the frame. In the transfer of the Shippingport reactor to the transport vehicle (a barge in this case), the jacks hoisted the reactor seventy-seven feet into the air, moved it approximately thirty-eight feet horizontally along a track and then lowered it onto a trailer.
The Energy Department's decision to decommission the Shippingport reactor in this manner, which avoided cutting apart the radioactive structure, saved an estimated seven million dollars and, perhaps more importantly, dramatically reduced worker exposure to radiation. However, such a procedure is probably not possible for most commercial reactors having an average rating of approximately 1000 megawatts, and would weigh over 2500 tons if filled with concrete. Moreover, even if larger reactors could be moved in one piece, the capital cost of fabricating the necessary lifting equipment would likely make such an approach economically unfeasible.
SUMMARYSystems and methods for dismantling a nuclear reactor are described. In one aspect the system includes a remotely controlled heavy manipulator (“manipulator”) operatively coupled to a support structure and located in a contamination control enclosure, and a control station located in a non-contaminated portion of a workspace. The support structure provides the manipulator with top down access into a bioshield of a nuclear reactor. At least one computing device in the control station provides programmatic logic to perform operations including: (a) dismantling, using the manipulator, a graphite core (also referred to as a “graphite moderator”), concrete walls, and a ceiling of the bioshield, the manipulator being provided with automated access to all internal portions of the bioshield; (b) loading, using the manipulator, contaminated graphite blocks from the graphite moderator and rubblized concrete from the bioshield into one or more waste containers; and (c) dispersing, using the manipulator, dust suppression and contamination fixing spray to contaminated matter.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
In the Figures, the left-most digit of a component reference number identifies the particular Figure in which the component first appears.
The systems and methods described herein relate to dismantling a nuclear reactor. A remotely controlled heavy manipulator (also referred to as an “excavator arm”) is supported by a bridge and trolley system. A structural support system positions the bridge and trolley system at an appropriate elevation to allow dismantling of the associated nuclear reactor. The bridge moves on the structural support along a particular axis. The trolley moves on the bridge along an axis substantially perpendicular to the axis of movement of the bridge. The heavy manipulator is mounted on the trolley using a slewing bearing that permits the heavy manipulator to swing from side-to-side. The heavy manipulator can interface with various tools (a suite of tools), such as a hydraulic hammer, bucket and thumb, clamshell bucket, scrapper, hydraulic shear, dust suppression/contamination fixing spray equipment, and thermal cutting equipment. The described systems also include a gantry crane that moves a lifting fixture capable of supporting a waste sack into which waste materials and other demolition materials are loaded. Particular embodiments use waste containers deployed on rails to move waste sacks and other demolition materials.
The dismantling operations are performed inside a contamination control enclosure to prevent the spread of contaminated particles to the facility and the surrounding environment. The contamination control enclosure is supported by a structural frame that is part of the overall structural support system. The contamination control enclosure has a negative pressure provided by a filtered air mover system, which also maintains airflow in a particular direction to control dust and prevent the spread of contamination.
A control station located outside the contamination control enclosure allows an operator to control the dismantling equipment without being exposed to the contaminated materials. The control station includes one or more areas for monitoring the dismantling operation through cameras located near the reactor being dismantled. The control station also includes various control mechanisms, such as touch screen devices, joysticks and switches, to control the operation of equipment used in the dismantling operation.
Particular embodiments described herein perform a top down dismantling and removal of components from the top of the reactor bioshield. In alternate embodiments, the systems perform top down dismantling and removal of components from the side of the reactor bioshield.
An Exemplary SystemExcavator arm 208 performs various tasks, such as lifting, rubblizing concrete and graphite, and excavation tasks associated with removal of the reactor components. The support structure described herein allows excavator arm 208 to access the internal components and internal surfaces of the bioshield. Excavator arm 208 is also capable of accessing areas adjacent the bioshield to perform testing procedures, maintenance, and load material into one or more waste containers.
Bridge 202 is configured to slide, roll or otherwise move along rails 204 and 206 to adjust the position of excavator arm 208 relative to the bioshield. In a particular embodiment, bridge 202 includes one or more motors to move the bridge along rails 204 and 206. Bridge 202 includes a bridge trolley 212 that moves substantially perpendicular to the movement of the bridge. Excavator arm 208 is connected to bridge trolley 212, which also includes one or more motors that allow the trolley to move along bridge 202. The two axes of motion provided by bridge 202 and bridge trolley 212 allow excavator arm 208 to reach all areas of the bioshield necessary for dismantling the reactor.
In a particular implementation, excavator arm 208 removes the graphite core (also referred to as a “graphite moderator”) from the bioshield and loads it into one or more containers, such as waste sacks. After removing the graphite core, excavator arm 208 is used to rubblize the concrete in the walls and ceiling of the bioshield. Excavator arm 208 is further used to package the rubblized concrete into one or more containers.
In a particular implementation, waste carts are provided that move along tracks or rails. The waste carts are winched or driven in and out of the waste loading area on the tracks/rails. Movement of the waste carts is controlled from a remote location outside the contamination control enclosure.
Excavator arm 208 is powered by one of two hydraulic skid systems. A primary skid system provides power to allow full operation of all functions and features of excavator arm 208 at full speed. The secondary skid system provides flow and pressure to recover the equipment from the work area in the event of a failure of the primary skid system. The hydraulic skid systems include pumps, motors, oil reservoirs, and valves needed to power the equipment. In a particular embodiment, the hydraulic skid systems are located near the control station. The hydraulic skid systems are located outside the contamination control enclosure to facilitate repair and maintenance. In other embodiments, the hydraulic skid systems are located on excavator arm 208. Flow meters are used to monitor and limit the flow of hydraulic fluid into the contaminated area. The signals from these flow meters are also monitored to detect leaks in the hydraulic system. The hydraulic system automatically shuts down if the ratio of the flows to and from a hydraulic valve bank is outside a predetermined operating range.
As discussed herein, particular embodiments also include a gantry crane 210 to assist with the removal of plugs from the roof of the bioshield to expose the graphite core. Gantry crane 210 is also used to move equipment and other objects, such as sacks of graphite material from inside the bioshield to one or more waste containers located outside the bioshield. A load cell associated with a crane trolley 214 determines a weight associated with waste containers to prevent overloading of the waste containers.
The ventilation system works with the contamination control enclosure 2102 to define a desired air flow path through the system. Generally, air flows from areas of no contamination (e.g., the areas outside of contamination control enclosure 2102) to areas of high contamination (e.g., the areas with the waste containers and openings in the top of the bioshield). This air flow prevents contaminants from entering non-contaminated areas. In a particular implementation, contamination control enclosure 2102 has a volume of approximately 242,000 cubic feet. In this implementation, four HEPA filter units (802, 804, 1302, and 1304) provide a total air volume movement of 24,000 cubic feet per minute.
An Exemplary Procedure-
- movement as the bridge moves on the runway girders,
- movement on the trolley,
- rotating on an axis centered on the bridge (swing),
- tipping down into the bioshield (hoist),
- rotating the excavator arm along its long axis (tilt),
- telescoping in and out to reach material (extend/retract),
- vertical movement of tools at the end of the arm (open/close), and
- lateral movement of the tool at the end of the arm (powertilt).
Excavator arm 2902 includes several tools and controls that perform various tasks during core and bioshield removal. These tools include:
-
- a bucket with powered thumb for digging and grabbing graphite and bioshield materials,
- a shear used to size reduce in-core components such as graphite, control rods, invar bars and experiments,
- a hydraulic breaker hammer that can rubblize concrete and graphite, and separate welded steel members,
- a grapple for rapid removal of graphite blocks,
- a vacuum to collect loose debris that remains at the completion of core and bioshield removal,
- an arm extension that provides additional reach for the excavator arm,
- spray equipment for the application of dust suppressant and fixative coatings, and
- various thermal and mechanical cutting tools for size reduction of the bioshield steel and other components.
During a reactor removal/dismantling project, a primary goal is removal of the core in a manner that avoids release of any contaminated material into the surrounding environment. Another goal of a reactor removal/dismantling project is the removal of the bioshield itself. When reactors were originally designed and constructed, they were intended to protect the operators. These reactors were not designed with provisions for future removal. As discussed above, bioshield walls and ceilings are typically five feet thick. Excavator arm 2902, through the use of one or more tools, is capable of reduce the size of the bioshield components and remove those components.
Operation of excavator arm 2902 and other components and systems may generate airborne contamination during the removal/dismantling process.
In one implementation, a release mechanism is operated on the lift fixture and the lift fixture is removed from the waste container leaving the waste sack in the waste container. Operators then install the waste container lid, decontaminate the waste container, survey the exterior of the waste container, and remove the waste container from the contamination control enclosure.
The above procedures are repeated until all of the graphite is removed from the bioshield. During removal of the graphite, if other in-core materials are encountered that need size reduction, the excavator arm is reconfigured to include a shear attachment or similar tool. For example, a hydraulic shear is capable of shearing 2″×2″ square steel bars (e.g., bars similar to control rods) and reducing the size of control rods, tie rods, structural members and other components. The in-core materials are then reduced in size and the excavator arm is reconfigured with the bucket attachment and the size-reduced in-core materials are removed with the graphite blocks.
After all graphite is removed from the bioshield, the excavator arm is reconfigured to include a HEPA (high efficiency particulate air) vacuum attachment, which removes additional debris from the floor and walls of the bioshield. The HEPA vacuum attachment includes three components, the vacuum unit with HEPA filtration, the collection container, and the vacuum tool. The collection container is located on the trolley. When the collection container is full, it can be removed from the trolley and emptied into a waste container for disposal with the other reactor debris. The vacuum tool is attached to the excavator arm and is positioned by movement of the arm.
Finally, a fixative coating is applied to all interior surfaces of the bioshield. The excavator arm has two integrated spray systems. One spray system is for dust suppressant applied to materials during the excavation process. The other spray system is for application of fixative material, which is typically sprayed onto all surfaces to lock any loose contaminated particles to the interior surface of the bioshield. Use of the fixative material prevents contaminated particles from being suspended in air or transferred to another surface during future handling. In one implementation, the pumps associated with the spray systems are located outside the contamination control enclosure to permit easy maintenance, repair, and replenishment of spray materials. The spray equipment is also configured to permit flushing of the spray lines remotely.
In a particular embodiment, hydraulic breaker hammer 4402 can be fitted with several different tool bits. One tool bit is a standard moil point used to rubblize concrete. A chisel tool is useful in rubblizing concrete as well as severing and/or reducing the size of other reactor components. Another tool bit is a modified chisel, which includes a v-shaped groove to allow positioning of the chisel on pipes, sheets, and tubing material that requires severing. The v-shaped groove also maintains the chisel in the appropriate location during operation, such as severing a component.
After the roof structure of the bioshield is removed, various tools and equipment are used to remove and reduce the size of the remaining bioshield components. For example, milling machines, thermal cutting equipment, and saws are useful in separating steel lining components from the concrete wall and reducing the size of the steel lining components. In particular implementations, the remotely operated crane places equipment and tools into the bioshield for use in removing the remaining bioshield components. After reducing the size of the bioshield components, the pieces are moved to one or more storage containers located near the bioshield using the crane.
A thermal cutting smoke removal system minimizes the impact of smoke on the ventilation HEPA filters during thermal cutting operations. Flexible and rigid ducting connect the filtration equipment to a portable hood that mounts on a wall of the bioshield. The portable hood includes fireproof curtains to account for irregularities in the cutting surface.
Computing device 5500 includes one or more processor(s) 5502, one or more memory device(s) 5504, one or more interface(s) 5506, one or more mass storage device(s) 5508, one or more Input/output (I/O) device(s) 5510, and a display device 5528 all of which are coupled to a bus 5512. Processor(s) 5502 include one or more processors or controllers that execute instructions stored in memory device(s) 5504 and/or mass storage device(s) 5508. Processor(s) 5502 may also include various types of computer-readable media, such as cache memory.
Memory device(s) 5504 include various computer-readable media, such as volatile memory (e.g., random access memory (RAM)) 5514 and/or nonvolatile memory (e.g., read-only memory (ROM) 5516). Memory device(s) 5504 may also include rewritable ROM, such as Flash memory.
Mass storage device(s) 5508 include various computer readable media, such as magnetic tapes, magnetic disks, optical disks, solid state memory (e.g., Flash memory), and so forth. As shown in
I/O device(s) 5510 include various devices that allow data and/or other information to be input to or retrieved from computing device 5500. Example I/O device(s) 5510 include cursor control devices, keyboards, keypads, microphones, monitors or other display devices, speakers, printers, network interface cards, modems, lenses, CCDs or other image capture devices, and the like.
Display device 5528 includes any type of device capable of displaying information to one or more users of computing device 5500. Examples of display device 5528 include a monitor, display terminal, video projection device, and the like.
Interface(s) 5506 include various interfaces that allow computing device 5500 to interact with other systems, devices, or computing environments. Example interface(s) 5506 include any number of different network interfaces 5520, such as interfaces to local area networks (LANs), wide area networks (WANs), wireless networks, and the Internet. Other interfaces include user interface 5518 and peripheral device interface 5522.
Bus 5512 allows processor(s) 5502, memory device(s) 5504, interface(s) 5506, mass storage device(s) 5508, and I/O device(s) 5510 to communicate with one another, as well as other devices or components coupled to bus 5512. Bus 5512 represents one or more of several types of bus structures, such as a system bus, PCI bus, IEEE 1394 bus, USB bus, and so forth.
For purposes of illustration, programs and other executable program components are shown herein as discrete blocks, although it is understood that such programs and components may reside at various times in different storage components of computing device 5500, and are executed by processor(s) 5502. Alternatively, the systems and procedures described herein can be implemented in hardware, or a combination of hardware, software, and/or firmware. For example, one or more application specific integrated circuits (ASICs) can be programmed to carry out one or more of the systems and procedures described herein.
CONCLUSIONAlthough the systems and methods for dismantling a nuclear reactor have been described in language specific to structural features and/or methodological operations or actions, it is understood that the implementations defined in the appended claims are not necessarily limited to the specific features or actions described. Rather, the specific features and operations of dismantling a nuclear reactor are disclosed as exemplary forms of implementing the claimed subject matter.
Claims
1-20. (canceled)
21. A system for dismantling a nuclear reactor, comprising:
- a support structure located within a workspace that at least partially surrounds a bioshield of the nuclear reactor;
- a control station located in a non-contaminated portion of the workspace; and
- a manipulator operatively coupled to the support structure and controlled from the control station, wherein the support structure is configured to provide the manipulator with substantially complete access to a radioactive contaminated core housed within the bioshield, and wherein the manipulator is configured to: dismantle the contaminated core to form removable contaminated blocks; and load the contaminated blocks into one or more waste containers for transport out of the workspace.
22. The system of claim 21, wherein the manipulator comprises a spray system configured to disperse a dust suppression spray onto contaminated matter located in the workspace.
23. The system of claim 22, wherein the spray system comprises an integrated spray system configured both to suppress dust and to fix any loose contaminated particles.
24. The system of claim 21, wherein the support structure comprises:
- a set of rails positioned above the bioshield; and
- a bridge mounted on the rails, wherein the manipulator is moveably mounted to the bridge.
25. The system of claim 24, wherein the bridge is configured to move along the set of rails, wherein the manipulator is mounted to the bridge via a bridge trolley, and wherein the bridge trolley is configured to move in a direction that is substantially perpendicularly to the movement of the bridge to provide the manipulator with top-down access into the bioshield.
26. The system of claim 21, wherein the support structure comprises a free-standing structure that is supported by a plurality of support columns independent of the bioshield.
27. The system of claim 21, further comprising a contamination control enclosure that encompasses at least a portion of both the bioshield and the support structure.
28. The system of claim 27, wherein the contamination control enclosure comprises a plastic walled containment that completely encompasses both the bioshield and the support structure.
29. The system of claim 27, wherein the manipulator is configured to load the one or more waste containers within the contamination control enclosure, and wherein the one or more waste containers are configured to transport the contaminated blocks out of the contamination control enclosure.
30. The system of claim 29, wherein the support structure comprises a barrier floor having at least one aperture sized to receive a top portion of the one or more waste containers, and wherein the top portion is substantially coplanar with a top of the bioshield while the contaminated blocks are being loaded into the one or more waste containers by the manipulator.
31. A system for dismantling a nuclear reactor, comprising:
- support means located within a contamination control enclosure that at least partially surrounds a bioshield of the nuclear reactor;
- dismantling means moveably mounted to the support means for dismantling a radioactive contaminated core housed within the bioshield to create removable contaminated blocks, wherein the dismantling means is remotely controlled to gain access to substantially all internal portions of the bioshield; and
- loading means to load contaminated material, including the contaminated blocks, into one or more waste containers for transport out of the contamination control enclosure.
32. The system of claim 31, further comprising dispersing means to suppress dust and fix loose contaminated material within the contamination control enclosure.
33. The system of claim 31, wherein the bioshield comprises a ceiling and a plurality of walls that surround the contaminated core, and wherein the dismantling means is further configured to remove at least a portion of the ceiling to expose the contaminated core.
34. The system of claim 33, wherein the portion of the ceiling that is removed comprises a protective cover of the of the bioshield and a plurality of ceiling plugs.
35. The system of claim 33, wherein the dismantling means is further configured to reduce the ceiling and the plurality of walls into rubblized material after the contaminated core has been removed from the bioshield.
36. The system of claim 35, wherein the loading means is further configured to load the rubblized material into the one or more waste containers for transport out of the contamination control enclosure.
37. The system of claim 35, wherein the dismantling means is disassembled and loaded into the one or more waste containers for transport out of the contamination control enclosure after the ceiling and the plurality of walls have been reduced into the rubblized material.
38. The system of claim 31, wherein the contaminated core comprises a graphite moderator.
39. The system of claim 31, wherein the dismantling means is configured to move on the support means above a top surface of the bioshield in both a first direction of travel and a second direction of travel perpendicular to the first direction of travel to provide the dismantling means with top-down access to the contaminated core.
40. The system of claim 31, wherein the dismantling means is remotely controlled from a control station located outside of the contamination control enclosure.
Type: Application
Filed: Sep 5, 2014
Publication Date: Aug 13, 2015
Applicant: Kurion, Inc. (Richland, WA)
Inventors: Robert R. Heim (Brighton, CO), Scott Ryan Adams (Longmont, CO), Matthew Denver Cole (Fort Collins, CO), William E. Kirby (Superior, CO), Paul Damon Linnebur (Milliken, CO)
Application Number: 14/478,500