Water research plays critical role in Hanford cleanup

                                            
Washington Water Research Center – showing several different flumes used for water and sediment studies. Mike Barber and graduate students Thomas Leake (left) and Travis Lopes (rt) are using them to help build pulsating jet mixers for storage tanks at Hanford.    
 
 
PULLMAN – What do you do when hundreds of corroded tanks are leaking nuclear waste into the groundwater – with no permanent disposal site in the nation willing to store it for you?
 
One idea is to convert that waste into glass logs.
 
Such is the goal of a $16 billion Department of Energy (DOE) project to build a vitrification plant at the Hanford nuclear site in the Tri-Cities. A critical part of that plan lies with a team of WSU scientists, students and staff in the water research laboratory at Pullman who are developing equipment to help contain liquid waste from the dilapidated reactors.
Mike Barber, director of the State of Washington Water Research Center – together with five faculty members, four graduate students, four undergraduate students and three technical staff – is working around the clock to build and test prototypes of pulsating jet mixers that will be used to keep radioactive fluids in suspension in pretreatment vessels.
 
The project began April 1 and is under a tight six-month deadline to be completed by October. Although not directly funded by the American Recovery and Reinvestment Act, the research ties in closely with a $2 billion stimulus project to accelerate clean-up of the Hanford site.
 
Plutonium problems
Hanford was originally established in 1943 with the intent to manufacture plutonium for atomic bombs. Over its 65-year history, Hanford produced more than 20 million pieces of uranium fuel – a left a legacy of contamination behind.
 
“During the Manhattan Project in the 1930s and 40s, they just threw (nuclear waste) into tanks and buried it,” said Barber. “Now they are starting to leak and contaminating the ground water.”
 
According to DOE, there are 177  tanks, each with a million-gallon capacity, at the Hanford site that have already leaked at least one million gallons of nuclear waste.
 
Before those tanks can be torn down, the waste must be safely removed and stored. The proposal is to pump the nuclear material out of the leaky tanks and then convert it into a solid, glassy substance – by mixing it with silica and subjecting it to intense heat in a process called vitrification.
 
The first step in that process requires transferring the waste material into pretreatment vessels, where it is important that it does not settle out of solution. 
 
“We want to stop the heavy metals from sinking to the bottom of the tanks,” said Mike McKinney, an employee of Energy Solutions out of Richland, who is working with WSU on the project.
 
“The materials need to be in suspension – with the same consistency throughout – for successful vitrification,” he said.
 
To that end, the water research team is building full-scale test pretreatment tanks with pulsating jet mixers (PJM) sealed inside them. Using a vacuum system, the jets will periodically draw in liquid and then discharge — dispersing the particles.
 
“The tanks and mixers must be able to work for 40 years without maintenance and have no moving parts,” said Barber. “No one wants to go inside to work on them, as they’re full of radioactive waste.”
 
Particles and flumes
The WSU water research lab was chosen for the PJM project because of the department’s expertise in water flow and particle entrainment systems. The laboratory is equipped with several flumes (enclosed water chutes) of various sizes which are used to measure how much force and velocity are required to move different types of particles. They also record how long it takes for particles to settle out of solution.
 
“We use similants such as sand, glass beads and clay in place of nuclear waste,” said McKinney. “We are trying to determine how much force it takes to move particles – in order to design nozzles and other elements that will allow the pulse jet mixers to keep the materials in suspension.”
 
“This is a unique application of the PJM,” said Barber. “It has never been used like this before. If it works, it will be used in the vitrification plant in a number of different vessels.”
 
Storage quandary
Once the liquid is removed from nuclear waste during vitrification, the resulting glass logs are still radioactive, but will no longer present a leak hazard.
 
McKinney said that the logs would be stored at Hanford until a permanent disposal site for high-activity nuclear waste can be identified.
 
Earlier this year, President Barack Obama cut funding levels for the controversial Yucca Mountain nuclear-waste repository in Nevada. His administration now plans to “devise a new strategy toward nuclear waste disposal.” At this point, it is undetermined what that strategy will entail.
 
For more information see online @ http://www.swwrc.wsu.edu/  or
http://www.hanfordvitplant.com/

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