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Nuclear Fuel Canister Welding Solutions
AWS in Motion 2007 (Flash Video)
Automated Welding System (PDF)
AWS Spares (PDF)
The
Berkeley Automated Welding System (AWS) performs semi-automatic
Gas Tungsten Arc Welding (GTAW) to seal canisters containing
spent nuclear fuel. Operator specified and supervised welding
is performed in accordance with Nuclear Regulatory Commission
regulations including compliance with the ASME Boiler and Pressure
Vessel Code Sections lll and 1X as well as AWS D1.1. The AWS
also includes the capability to remove the canister's lid using
an interchangeable plasma torch.
Reduced
Worker Radiation Exposure
The crucial customer need addressed by the AWS is the reduction
of worker radiation exposure. This is realized by reducing
welding operator time near the spent fuel canister, reducing
the number of required operators, increasing operator distance
from the canister, minimizing rework, and eliminating tool
failures. Remotely supervised automated welding provides a
solution.
The
AWS need only to be approximately centered on the canister
lid. This is achieved by remotely operated crane.
High-levels
of welding process automation enable a team of two operators
to be as productive as teams of four with prior generation
automated welding systems.
Welding
set-up, and welding itself, is performed by operators located
at a machine control console up to 100 feet from the canister.
The
need for weld rework is minimized by the excellent process
control provided by operator supervised automated welding.
Robust
control system design supports remote recovery from faults
or stops, and reduces causes of system failure.
Precise
Semi-Automated Welding of Complex Geometries
Continuous, real-time, five-axis control of the torch head
position enables precision welding of canister lids, as well
as keyways or penetrations.
AWS
theta-axis rotation allows the weld-arm to travel around
the rim of the six feet in diameter canister lid.
The
radial arm adjusts the radial distance to the torch tip
from the AWS center axis.
The
height-axis raises and lowers the torch tip to follow the
workpiece and maintain a constant welding voltage.
The
twist-axis "twists" the torch tip to keep it perpendicular
to the seam.
The
torch tilt-axis enables the torch tip to reach points at
the proper angle along the seam to prevent interference
with canister wall.
A
sixth servo-controlled axis controls welding wirefeed.
All
six axes are precisely coordinated in real-time by the AWS
control system.
Operator
and Automation Work Together
The welding system guides the remote operator through a pre-programmed
canister welding process proven to produce good welds by prior
customer use. The operator supervises, and may fine-tune,
the process on-the-fly to achieve the desired weld.
With
remote operator assistance, an AWS control algorithm quickly
learns the precise location of the weld to be performed.
This accommodates the casual physical centering of the welder
on the canister—which substantially reduces worker
radiation exposure as it is done with a crane.
The
AWS provides pre-programmed welding operations including
inner cover, outer cover and qualification welds, tack welds,
root welds and circumference welds. Necessary weld geometry
and default welding recipes are sourced with the welder.
The end-user's welding experts program exact welding process
parameters based on their experience and preference.
Canister
welding is subsequently, and repeatedly, executed utilizing
pre-programmed weld geometry and process parameters—parameters
proven by prior customer use. Precise control and synchronization
of welder axes and weld process parameters are delivered
by the welder's integrated, real-time control system.
The
welding system provides remote, two camera, video monitoring
of the leading and trailing edge of the weld puddle, tungsten
tip, wire entering the puddle, and weld prep. The supervising
operator may fine-tune the welding process on-the-fly to
accommodate deviations and achieve the desired weld. Such
deviations might include canister or lid dimensional variations
and deformation due to heat input during welding.
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