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Waterjet contractor AK Services has cut a large access hole in the US Department of Energy’s active radioactive waste storage tank in Hanford, Washington, using pump equipment from Jet Edge.

The contractor cut a 55in-diameter hole in the top of the underground tank to allow for the installation of a robotic system that will remove 247,000 gallons of radioactive and chemical waste stored in the tank during the Manhattan Project and Cold War so it can be vitrified for safer storage.

Battling freezing temperatures and the challenges of running remote-controlled ultra-high-pressure waterjet equipment from a 300ft (91m) distance, AK Services used a specially engineered abrasive waterjet cutting machine to make the huge cut through 15in (38cm) of concrete and steel rebar in just 22 hours.

The company performed the cut at 8in per hour using an abrasive jet of garnet grit mixed with three gallons per minute of water pressurised to 48,000psi with a Jet Edge waterjet intensifier pump.

The finished cut is the result of more than a year of planning and preparation by AK Services and Hanford Site Tank Farms prime contractor Washington River Protection Solutions (WRPS) to ensure worker safety and protection of the environment, according to Kent Smith, WRPS’s deputy manager of retrieval and closure operations.

AK Services spent a year developing the waterjet cutting system for the project and testing different abrasives to get consistent data for rate of advance and garnet usage, added Carl Franson, AK Services’ vice-president of operations.

He said: ‘The motion device had to be specially developed to secure itself inside a 75in steel riser and cut a 55in hole.

‘We also needed to be able to level the motion device to make sure it did not drag the abrasive-jet focusing tubes on the concrete surface,’ added Franson.

AK Services engineered a three-piece stainless steel motion system with two circles separated by guide bushings with a ring gear in the middle.

The ring gear features four redundant Jet Edge high-flow abrasive-jet cutting heads in case of failure and is driven by a set of reduction gears and a drive motor to achieve the proper cutting rate.

Pneumatically actuated rams are placed on the sides and bottom to level and secure the system.

Franson continued: ‘We were able to do the entire cut with the one lead cutting head.

‘We used a Jet Edge high-flow abrasive-jet cutting head with a Roctec 100 focusing tube rather than the standard tungsten carbide and we ordered diamond orifices from Jet Edge to ensure the longest life possible,’ he said.

Once the system was in place, the cut itself was easy, according to Franson, although not without challenges.

‘The biggest challenge was running the equipment from 300ft away,’ he said.

‘The tank top is in a radiation area and entry to the area is regulated to the extent that anything that enters the tank farm must be scanned and cleared prior to being released out of the fenced-in restricted area.

‘The pumps and control systems had to be outside of the restricted area to ensure they did not become contaminated with radiation and then become the property of the Department of Energy.

‘We also had the added challenge of winter weather, so we installed air dryers and used airline antifreeze to keep the system from freezing up.

‘The ultra-high-pressure lines were kept running, but as the temperatures dropped we blew them out with air,’ added Franson.

After the concrete plug was lifted from the tank, it was immediately wrapped in a plastic sleeve to prevent any spread of contamination and was then placed in an isolated area where it is being staged for disposal at the Hanford site.

A large riser was placed in the hole to support the robotic retrieval system.

According to the Department of Energy, the riser has a shield plug bolted to its opening and thick gasket material around its outside to seal the hole.

The department plans to begin retrieving waste from the tank this summer.

The tank is one of more than 100 similar underground tanks that the Department of Energy is cleaning out as part of its environmental cleanup effort at the Hanford site, which was once home to nine nuclear reactors that produced plutonium for the Manhattan Project and the US nuclear arsenal.

Hanford is considered the most contaminated nuclear site in the US.

Established in 1984, Jet Edge is a global designer and manufacturer of waterjet systems for precision waterjet cutting, surface preparation and coating removal.

Jet Edge manufactures precision waterjet cutting tables, waterjet pumps, and waterjet parts and accessories.Jet Edge also manufactures mobile waterjet systems for portable water jet cutting, ultra-high pressure water blasting, cleaning and surface preparation.This vertical integration provides customers with the convenience of only having to call one company for sales, service and parts.

Jet Edge service is available 24/7/365 days a year.

Jet Edge waterjet systems are used around the world in a broad range of industries, from the world's leading airlines to automotive, aerospace, industrial manufacturers, machine and job shops. Jet Edge waterjets are capable of cutting virtually any material, including metals, stone, plastics, composites, rubber, foam, food and paper. Jet Edge waterjets are built in St.Michael, MN, USA.The company has distributors in Asia, Europe, the Middle East, and North and South America.

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