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Technology Factsheet

Chicago Pile 5 DAWP

Category: Robotics > Dismantling and Retrieval > Bespoke System
Reference # : Model No :

Bespoke design. Uses Schilling manipulators. The DAWP system was used to perform mechanical dismantlement of the radioactive reactor and bio-shield structures. The DAWP manipulated standard, commercially available tools (i.e., circular saws, jackhammers, etc.) using two Schilling Titan III hydraulic, teleoperated manipulator arms controlled from a remote location into the reactor assembly using the facility’s polar crane.

The DAWP consists of a platform base, two Schilling Titan III six degrees of freedom (DOF) hydraulically driven manipulators, a remote viewing system, a lighting system, a tool control system, and a tether that supplies the hydraulics, power, and control signals to drive the DAWP functions.

Site:US Other
Industry:Nuclear
Size:Very Large (>100kg/200lb, >120cm/48in)
TRL:Operational (9)
TRL2:Operational (9)
Tether: *
Waterproof: *
Payload: *
Reach: *
Manipulator: *

Benefits

Limitations

Comments

The CP-5 reactor was a heterogeneous, heavy water cooled and moderated, enriched uranium fuelled, thermal neutron reactor designed to provide neutrons for research. CP-5 first achieved criticality in February 1954 and operated for twenty-five years until its final shutdown in 1979, when the fuel rods were removed from the reactor and the heavy water was drained from the system. After eighteen years of cool down, CP-5 contained significant activation and contamination problems representative of a nuclear facility.

The DAWP demonstration focused on the use of the DAWP to segment and dismantle the CP-5 reactor tank and surrounding bio-shield components (including the graphite block reflector, lead and boral sheeting) and to perform some minor tasks best suited for the use of teleoperated robotics. The DAWP was provided by a consortium of national laboratories and industry manufacturers. Individual components and subassemblies were purchased from or provided by Schilling Robotics Systems, RedZone Robotics, ORNL (Oak Ridge National Laboratory) and INEEL (Idaho National Engineering and Environmental Laboratory).

The demonstration was performed at the Argonne National Laboratory (ANL) CP-5 Research Reactor from June through September 1997. The DAWP’s ability to remotely cut and dismantle the aluminium reactor tank, disassemble the graphite, boral, and lead subassemblies, and transfer these materials to a staging area was tested. The system could be operated by someone approximately 250 feet away without direct line-of-sight.

Several remote operation technologies were deployed at the Argonne National Laboratory (ANL) Chicago Pile 5 (CP-5) reactor for use in the dismantlement of this reactor. A major remote system was implemented at CP-5: the Dual Arm Work Platform (DAWP).

At the CP-5 reactor facility, the two arms were mounted to a steel work platform (DAWP) designed to hold the associated tooling, utilities, and cameras supporting the operation of the manipulator arms and providing a sturdy base for lifting the assembly into the reactor assembly using the facility’s polar crane.

ORNL provided an initial set of tools: impact wrenches, a powered right-angle drive, side grinders with cut-off wheels, reciprocating saws, circular saws, a router-based milling head, and drills. As time went on, ANL became more involved in tool selection and modification for remote use, including hand-held band saws, heavy-duty circular saws, and impact chisels. Cutting tools used vegetable oil-based lubrication systems to extend blade life. No flame based cutting was allowed, and the use of pneumatics was discouraged because of concerns over the spread of contamination.

The key results of the demonstration are as follows:
- Removed 5300lbs. of graphite blocks, 1400lbs. of lead sheeting, 620 lbs. of boral, 2 000 lbs. of carbon steel;
- Untorqued and removed 26 of the 36 carbon steel studs in the reactor tank’s top flange;
- Size reduced and dismantled a significant portion of the aluminium reactor tank (following approximately 200 linear feet of cuts through 3/8 - 3/4” aluminium plating), and removed the resultant 600 lbs. of aluminium plate from the reactor tank assembly.
- Was controlled by two operators working in an adjacent control room. This way, personnel could maintain a safe distance from the radiation in the CP-5 reactor. The DAWP was operating in a radiation field averaging 0.75 to 2.0 R/hr for the duration of this work. By using this remote system, conservatively speaking, approximately 15 person-rem of exposure was saved.
- Obtained data concerning the training of previously untrained technicians into competent DAWP operators. This demonstration showed that technicians were considered trained after an average of approximately 8 hours formal training and approximately 40 hours of mock-up training.
- Can be moved to a low dose or protected area for maintenance operations, reducing personnel exposure during these procedures. The DAWP is capable of disengaging and re-engaging tools remotely, so that a variety of tasks can be performed without down time or removing the robot from the hazardous environment.
- The DAWP did experience numerous troubles on start-up. The primary problem arose with the hydraulic fluid. Each arm had to be decontaminated and sent back to the manufacturer to be rebuilt. It is believed the Houghto- SafeTM either disintegrated o-rings in the arm or otherwise caused damage within the arms. The result was often heavy leaks which required the cession of work. The DAWP was able to function with only one arm. However, for future operations the purchase of a spare arm, to be attached if an arm in use breaks down, is highly recommended.
- Other problems occurred with the overheating of the system (a second heat exchanger was added, solving the problems), some software glitches, and minor troubles with manipulating the tools. As operational knowledge of the robots and the proficiency of the operators increased, most of these problems were solved.
- Having an on-site technician capable of performing routine and preventative maintenance is essential in avoiding costly decontamination of parts.

Operational Experience:

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