Environmental Science & Engineering - www.esemag.com - November 2005
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AMEC’s tests prove successful for radioactive waste clean-up

By John Kageorge

These are artist renderings of the GeoMelt In-Container Vitrification™ (ICV) process.

Cutaway view of the ICV container prior to processing.

Cutaway view of the ICV container during the melting process.

Cutaway view of the ICV container following treatment, showing the resulting block of vitrified waste.
A group of Canadian engineers and scientists from AMEC have helped develop a promising solution for the world’s largest environmental clean-up project.

The Hanford Site in Washington State, perched on the bank of the Columbia River, has radioactive waste dating back to the Manhattan Project. AMEC, which is an international project management and technical services company, has just completed tests and received encouraging results that may impact this problem which began over half of a century ago.

The nuclear reservation is in the dry desert climate of central Washington State. There are two targets for the clean-up on the nearly 600 square mile site. The first one is obviously the waste; it is estimated that there are 53 million gallons of it. The waste is stored in tanks, some of which are over 50 years old and designed as a temporary measure until better technology became available. The second target is the soil. Some of the tanks have leaked, causing the ground to become contaminated by the radioactive material.

The US Department of Energy is in the midst of a USD $2 billion per year effort to remove all nuclear waste on the site by 2035.

A nuclear age solution
AMEC has developed a process called GeoMelt®. It uses electrodes to heat contaminated waste and soil at temperatures that can reach 2,000 degrees Celsius. When the material hardens, hazardous inorganic and radioactive contaminants are permanently trapped in a glassy, solid mass that is 10 times stronger than concrete.

In other words, GeoMelt melts radioactive soil into glass bricks, making it inert.

The process already has been used in projects on three continents to successfully treat a wide range of contaminants, including polychlorinated biphenyls (PCBs), dioxins, pesticides, herbicides, mixed radioactive wastes and a variety of heavy metals. All classes of contaminants can be treated and virtually all types of debris can be accommodated, including drums, scrap metal, concrete, boulders, asphalt, wood, tires and plastic.

About 50 specialists from AMEC’s Vancouver and Trail offices in British Columbia led the first phase of tests using their GeoMelt technology. The BC team did over half of the design work, including all of the critical 3D modeling. They have since teamed up with a team of equal size in Hanford to conduct a second phase of tests.

The demonstration project
One of AMEC’s tests focused on the future underground treatment of buried vertical shafts containing nuclear waste. The other test is part of an on-going demonstration program supporting the eventual retrieval and treatment of millions of gallons of radioactive waste stored in underground tanks. The test associated with the vertical shafts was performed under a contract with the US Department of Energy. The test supporting the tank waste program was performed under contract for the Department of Energy’s Office of River Protection and its prime contractor at the Hanford site, CH2M-HILL Hanford Group, Inc.

For the vertical shaft test, a mockup of the more than 140 underground waste-storage shafts at Hanford was developed. The mock-up – like the actual Hanford shafts – consisted of five bottomless and topless 55-gallon drums that were welded end-to-end and buried. The mock-up was filled with simulated waste including steel, wood, concrete and soil and chemical simulants. It is anticipated that the actual Hanford shafts contain plutonium, uranium, cesium and other highly active waste, making excavation before treatment unsafe due to high dose rates and the possibility of spontaneous chemical reactions.

The vertical shaft test successfully melted the entire shaft in just seven days, resulting in a monolith that matched its predicted size.

The second test also used simulated waste and concerned the above-ground treatment of low activity radioactive tank waste in special refractory-lined containers. GeoMelt is under consideration for the treatment of between 30 and 70 percent of Hanford’s estimated 42 million gallons of low-activity tank waste.

The GeoMelt melt surface when processing plutonium contaminated waste. The melt temperature is approximately 1,550 degrees C.
Photograph of a piece of GeoMelt vitrified product. This was made of soil from the Hanford site in South Eastern Washington State.
Environmental restoration
Working on challenging environmental problems is not new to AMEC. The Sydney Tar Ponds in New Scotia, which is Canada’s biggest environmental clean-up project, will require 2,700 person-years of work and a decade of time to complete. The plan is to dig up and destroy the worst contaminants, using methods that have proved to be safe and effective on similar sites. Remaining materials will be treated in place and then contained within an engineered containment system. The cleaned-up sites will be landscaped to fit their natural surroundings or future site use.

This is quite similar to the restoration work AMEC is doing in connection with NASA. The company is currently restoring the home of several endangered species and one of North America’s largest sea turtle nesting grounds, Cape Canaveral. Decades of satellite, rocket, and shuttle launches have loaded the soil with lead, PCBs and other nasty elements.

An eight day process
In the bulk vitrification, the container and its liner system performed to expectations and a 42-metric-ton glass brick was produced in eight days.

Basically, there are four steps:
  1. Radioactive waste is liquefied, then oxidizers are added.
  2. The mixture is poured into enormous containers that contain electrodes.
  3. Using 5,000 amp current, the mixture is heated to 2,000 degrees Celsius.
  4. The material is cooled, creating a glass brick.
The container is then sealed and stored, with a life span of thousands of years.

Nuclear familiarity
Surprisingly, AMEC’s environmental practice is not as well known as that of its project management and technical services.

The company is quite familiar with the nuclear sector, and this has proven quite helpful to the GeoMelt project. AMEC is a leader in the field of nuclear power in Europe. Earlier this year, AMEC acquired NNC Canada Limited, Nuclear Safety Solutions Limited and Monserco Limited. In October, AMEC was awarded the project management for the restoration of the Bruce Power nuclear facility, which will begin delivering power in 2009.

Next step, Los Alamos?
AMEC’s positive test results for both procedures, vertical shafts and bulk vitrification, are strong advances for this mammoth-size project. Both procedures will now move forward for further testing. The next test for the vertical shaft process will be on an actual shaft at either Hanford or the Los Alamos National Laboratory site in New Mexico. Further testing of the bulk vitrification process will include the treatment of up to 300,000 gallons of actual tank wastes at the Hanford site as part of a demonstration program.

John Kageorge is with AMEC
E-mail: john.kageorge@amec.com

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