At 75 Years Old, H Canyon Continues to Adapt to Changing SRS Missions

AIKEN, S.C. — EM workers at the Savannah River Site (SRS) reconfigured equipment for changing mission needs at H Canyon, a testament to the flexibility of the chemical separations facility that is more than 75 years old and the only one of its kind in operation in the United States.

As a result of bringing an electrolytic dissolver online, EM team members at H Canyon needed to reconfigure other equipment to continue the existing mission. This reconfiguration was completed to maximize planned operations for this fiscal year, which ends Sept. 30.

“Mission needs dictated that we dissolve Material Test Reactor (MTR) fuel at the same time as we are dissolving Fast Critical Assembly (FCA) reactor fuel,” said James Therrell, manager of Environmental Management Mission Planning. “This flexibility will ultimately allow us to safely meet our long-term processing needs for spent nuclear fuel.”

The employees reconfigured one of H Canyon’s two chemical dissolvers for use with the MTR fuel. Dissolution involves lowering the fuel into the dissolver to dissolve the aluminum-clad fuel using a nitric acid solution.

“The chemical dissolvers have to be configured with the right sized insert to fit the fuel,” said H Canyon Facility Manager Matt Arnold, an employee of the site’s managing and operating contractor, Savannah River Nuclear Solutions. “The inserts are specifically designed for each type of fuel and help lower the fuel into the dissolver slowly, allowing it to be dissolved from the bottom, up.”

Those dissolvers were most recently used to dissolve two different kinds of aluminum-clad fuel from the MTR and the High Flux Isotope Reactor. Although these two types of fuel are both aluminum clad, they are shaped differently due to their unique bundle configurations.

Meanwhile, an electrolytic dissolver will be used for the FCA fuel. That dissolver adds electricity to the dissolution process for the stainless-steel-clad fuel.

H Canyon recently installed that dissolver as part of a new mission to process the FCA fuel, which came from the Japan Atomic Energy Agency. Japan and the U.S. removed plutonium and highly enriched uranium from the FCA reactor in 2016, fulfilling a commitment made at the 2014 Nuclear Security Summit.

The plutonium fuel from the FCA is currently stored onsite and will be transferred to H Canyon for processing once workers finish preparations for the dissolution work. H Canyon last ran an electrolytic dissolver from 1969 to 1980 as part of previous missions.

After the FCA campaign, the electrolytic dissolver can be used for dissolution for other non-aluminum based spent fuels, helping advance DOE’s nonproliferation mission. H Canyon’s current mission is to dissolve spent nuclear fuel currently stored in an underwater storage facility at L Basin.

Arnold said that changing the inserts on the dissolver is not an easy process. Since all work in the canyon must be done using remote cranes to protect workers from radiation, months of planning, preparation and coordination among departments are needed before the actual dissolution work can be performed.

Therrell said the reconfiguration was completed safely and successfully thanks to the hard work from current employees.

“But also thanks to the engineers who designed this canyon back in the early 1950s,” he said. “It continues to amaze me that their foresight allowed the canyon to be the flexible and adaptable facility it is to this day.”

Both the chemical and electrolytic dissolving processes produce a liquid that is sent through the site’s liquid waste facilities, where it is made into glass through a process called vitrification. It is then safely stored onsite until a federal repository is identified.

-Contributor: Lindsey MonBarren