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Nuclear Canister Welders
More than fifty-five years from the genesis of the nuclear age, the world's energy producers and governments are still grappling with the storage of spent nuclear fuel. Today's solutions require that spent fuel cells, which are still very much active in terms of heat and radiation emissions, be sealed in stainless steel canisters for storage. To minimize the chance of leakage these canisters are sealed via a welding process that requires both an inner and outer lid be welded to the canister. Because the industry has strict limits with regard to the amount of exposure to radiation that workers may receive, it is necessary to minimize the amount of time that workers spend sealing the canisters. On the other hand, sufficient care must be taken to ensure that the canisters are adequately sealed. These conflicting requirements make traditional pipe welding unsuitable for this process.
In 1995, working closely with nuclear welding experts, Berkeley Process Control revolutionized automated welding for the nuclear energy industry with the introduction of its Automated Welding System (AWS). In contrast to competitive systems, the Berkeley AWS was specifically designed so that workers could perform all welding remotely — up to 100 feet from the canister. Locating the weld-head onto the canister requires the user to remotely place the welder within a few inches of the canister center. Berkeley's semi-automated remote teach process then locates the weld-head precisely to the canister. On some canister designs, non-circumference geometries may exist, such as the vent and siphon port keyway. Welding the complex geometry of the keyway is also performed remotely using the AWS. Other systems are incapable of welding non-circumference welds and therefore require workers to manually weld the keyway.
Features and Advantages
- Field proven
- Utilities
that have switched to the AWS have recorded exposure reductions
of more than 50%.
- Chris Dobry,
the dry fuel storage engineer at Calvert Cliffs Nuclear Power
Plant, calls the AWS a "very robust" and "beefy"
system, and states; Use of the AWS has "knocked 10 hours
off of our welding process per canister…and we've never had
a problem with any of the welds."
- Only requires
two operators using an intuitive, easy to use operator interface
- Improved
and consistent weld quality through fully programmable weld recipes.
- Calculates
and welds the complex geometries around primary welds and keyways
- Provides
the operator with all of the weld parameters in real-time
- Coordinated
control of the welding power supply, wire feed, and all motion
axes simultaneously
- Accommodates
a plasma torch option for the reopening of canisters
- Cable lengths
up to 100 feet allow for remote operation
- Pre-programmed
operations (inner cover, outer cover and qualification welds),
welding steps (tack, root and circumferential welds, and robust
design, combine to facilitate reliable operation.
- Weld start
sequence contains parameters for pre-purge time, current ramp-up,
ramp-down and post-purge-time.
- Standard
oscillating torch features adjustable parameters for excursion
time, dwell, and width, synchronized with weld current, voltage,
and weld path.
- Wire feed
schedule contains adjustable parameters for start feed delay,
stop feed delay, primary and secondary speeds, and duty cycle.
- Allows for
on-the-fly operator control and monitoring of weld quality.
- The AWS uses
a gas tungsten arc welding process but can accommodate a hot-wire
TIG option
Related Links
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BX-300 Wafer Handling (PDF)
Registration Updates
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