Valve innovation helps with nuclear waste

Valves and actuators designed for handling radioactive waste must meet strict government requirements. This sometimes requires unconventional solutions. Such was the case at the Hanford Waste Treatment Project (WTP), Hanford, Wash.

By Roy Johnson, Flowserve

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“We worked very closely with Bechtel, and were focused entirely on designing and building a solution that would give Bechtel what they needed,” says Shaw. “At that time, that solution did not yet exist in our product line.”

Design meets opportunity

The Flowserve team would soon have a solution — the new Durco Mach 1 high-performance plug valve. Though the Mach 1 hadn’t yet been released, this new plug valve had been designed with flexibility that the G4 didn’t offer. This gave Flowserve the chance to pursue the Hanford project with a top-entry plug valve that could be modified for remote operation and repair.

Bechtel also needed the valve’s seat to be constructed of wear- and radiation-resistant Ultra-High Molecular Weight Polyethylene (UHMWPE), to stand up to the radioactive slurries at Hanford. Fortunately, Flowserve had already designed the Mach 1 to allow a variety of seat materials, including UHMWPE.

“The Mach 1 gave us the flexibility to build a solution for Bechtel,” says Fred Shanks, senior product engineer, Flowserve Flow Control, who worked on the Hanford project. “It was a remotely repairable valve that could have an UHMWPE seat that could be easily removed.”

Still, the Mach 1 would require modifications to enable its remote repair and make it fully radiation-resistant. A team of Flowserve engineers at the company’s Cookeville, Tenn., engineering and manufacturing site began working with the Flowserve sales team in Washington to modify the Mach 1 for Bechtel.

Proving the concept

The modification process was not without some hitches along the way. “While UHMWPE is highly wear- and radiation-resistant, it also requires higher torque levels,” adds Shanks. “Adjusting for the space constraints that Bechtel gave us to work with and the torque requirements of the Mach 1 with an UHMWPE seat was a delicate balancing act. It forced us to keep innovating with the valve’s design and what actuators we could use for it.”

In early September 2001, Larry Shields, senior sales engineer, Flowserve Flow Control, arranged for a presentation to the Bechtel WTP design team. Shaw and Shields presented a prototype Mach 1 valve with modifications for cartridge repair and a remotely operable stem extension to demonstrate the removal and replacement of the repair cartridge.

Bechtel engineers were very receptive to the modified design, and seemed to be convinced that it would work for the application. However, due to stringent DOE requirements, Bechtel required Flowserve to prove the Mach 1 valve design and materials capabilities with a working demonstration in a slurry service that would closely replicate the WTP site conditions (Figure 3).

Figure 3. The space constraints were an important factor in valve selection.

Figure 3. The space constraints were an important factor in valve selection.

Bechtel gave Flowserve worst-case specifications for the radioactive slurry and required a 20-year equivalent cycle test. Flowserve developed a recipe for the test media to match the size of the solids and their viscosity and weight per Bechtel’s specifications.

Unleashing creativity

Shaw drew from his previous work in pumps and well-drilling to come up with a combination of commercially available drilling fluids and bentonite clay additives that exactly matched the test media specifications. During a visit to Cookeville only two weeks before the scheduled demonstration, Shaw helped a team of Flowserve engineers and technicians, led by Shanks, to design and build a recirculating test rig to keep the media solids in suspension as required during valve testing. The test demonstration satisfied Bechtel’s requirements, and the modified Mach 1 plug valve was added to the list of acceptable valves for the Bechtel WTP bulge applications.

“A big part of the process was brainstorming ideas,” says Shields. “We would throw out ideas and try to figure out what would work. We were really trying to innovate to get Bechtel what they needed. Our engineering and manufacturing teams worked together to see how we could implement the ideas.”

“We didn’t just present a concept to Bechtel,” notes Shaw. “We took the time and the initiative to prove to Bechtel that our concept would work.”

“This has been a very challenging project in a lot of respects,” says Jerry Sutton, senior piping materials engineer with Bechtel and a responsible engineer on the WTP project. “One aspect was the way the project was scheduled, which made everything extremely urgent. Everything we did was trying to catch up, because the project started construction about the same time we started engineering.”
“Flowserve did quite well under the circumstances,” adds Sutton. “They were very cooperative and very sensitive to our requirements.”

Automating the valves

The next challenge in the process was to qualify Flowserve Automax valve automation systems with Bechtel, and to design and build adjustable stainless steel extensions with double universal joints to enable remote operation and repair of the valves from outside the bulge containment vessels. Bechtel required the valves to be welded into the bulge piping at a 5° angle to promote drainage. The universal joints at the top and at the bottom of the extension were required to eliminate any side-loading that the 5° operating angle would create.

Shaw and Shields worked with Vince Rohrig, automation product manager, and Stan Piela, special projects engineer, Flowserve Flow Control, to successfully design field-adjustable hardware for manual and automated operation of the bulge valves regardless of their orientation or distance from the top of the bulge vessels.

“Bechtel wanted stem extensions that could adjust to any length they needed, so we had to innovate again,” says Shaw. “We came up with a design for the extensions that could work for any valve in any position in the bulge. Vince’s design allowed the extensions to be manufactured as a standard unit that was adjustable to any length during final installation.”

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