At the Savannah River site in Aiken, South Carolina, SSMRC millwrights were called upon to perform the unusual task of removal of the bolts in a contaminated storage tank in order to create unobstructed space for additional spent fuel storage racks. The problem working with radioactive contaminated storage tanks, and having to make modifications in such an environment, is that no matter how you propose to perform any modifications, you must accomplish the task remotely, without coming in contact with the contamination. Specialized procedures must be developed using specialized equipment, which may not be commercially available at the time.
For this job, bolts had to be cut below a 1/4" from the imbed, the tool had to be powered by plant air, and no air leaks could happen. This tool had to be operated in a pool 30-feet deep and in a trough just 3-feet wide.
To accomplish this, it was necessary for everyone involved to help solve this problem and to work as a team. They researched tools available, but did not find anything that could fit the application. So, SSMRC Local 1263 members Logan Brown and Craig Usher, and Construction Engineers Mike Brott and Joe Carroll, worked together to come up with an innovative concept for a tool that could do the job.
Fabrication took place in the central shop's fabrication facility. Mock-up and testing activities were performed to create a one-of-a-kind, highly customized saw capable of removing the exposed portion of bolts located beneath radioactive-contaminated water as deep as 30 feet. The fabrication included machining their own unique bearing housing, drive shaft, and modifying the wheels of a portaband saw for this tool.
"The team didn’t call in design engineers, consultants or specialized saw vendors,” said George Sewell, Savannah River Nuclear Solutions' Construction Manager. “Instead, keeping safety as the top priority, they carefully examined all sides of the challenge and quickly and creatively solved the problem using their combined experience, knowledge, and on-hand resources.”
At times, and in certain areas, this task was accomplished while working under difficult lighting conditions and little clearance from surrounding submerged objects. According to Sewell, the end result was a pneumatic (air driven) band saw suspended from a long, specially designed metal rod designed to ensure the blade would cut close to the surface of the basin floor. All eight 3/4" stainless anchor bolts were cut in just two hours.
“The ingenuity and work ethic of our employees continues to impress me,” said Sewell. "The project was a complete success."