Hanford Researchers Puzzle Over Preventing Sludge Tank 'Burps'
We all burp sometimes. It turns out, so do underground waste tanks at the Hanford Nuclear Reservation.
But it’s no laughing matter. This waste can burp up flammable hydrogen gas from its radioactive belly. Now, scientists are trying to figure out just how much sludge they can pile in a tank without risking a burp that could endanger workers and the public.
Tom Fletcher is a spiky red-haired top manager for the Department of Energy. He’s standing before a moonscape of gravel, vent stacks and machinery.
“Just to give you some perspective, we’re in the 2-East area, we’re at C-Farm right now,” explains Fletcher.
The C-Farm in central Hanford is where some of the 56 million gallons of radioactive sludge is stored in aging underground tanks. It’s the leftovers from plutonium production during World War II and the Cold War.
This toxic brew underfoot always produces flammable hydrogen gas. Most of the time is seeps out gradually, and is safely vented away.
But here’s the potential problem: If a tank were to burp up a large amount of that flammable gas all at once it could create a large burn. Or a boom complete with flying shrapnel and waste vaporizing into the air. Or even liquid waste shoved out through the tank’s air filtration systems.
The whole scenario could shut down cleanup work for a very long time.
“That issue can be solved long term, whether it be through mechanical means -- mixing, creating pathways that are there permanently," says Fletcher. "But from a perspective of being done with the 2014 milestone, and being done with the C-Farm, it’s critical to solve.”
Fletcher is quick to add that hydrogen gas doesn’t build up in tanks that often. But now one of the big cleanup strategies is to empty out unstable tanks and put that waste into more secure ones.
Sounds reasonable, right?
Here’s the big question: If you pile more sludge into those tanks, could the weight of the waste itself trap bubbles deep in the sludge? And could those bubbles accumulate – until they were released nearly all at once?
That would be bad. So top brass at Hanford brought in Phil Gauglitz -- an expert on bubbles.
Yes, he’s paid to study bubbles.
“When it comes to bubbles that’s one of the things that I’m particularly good at, or knowledgeable of,” Gauglitz says.
Behind several code-secure doors and locked gates is his warehouse-like lab in north Richland. Two of his scientists pull out what looks like a massive kitchen hand mixer. It’s the size of a chain saw and just as loud.
This powder-blue goo is a mixture of clay, ground up glass and water that acts a lot like radioactive sludge. And while we were talking, some of that sludge in a tank nearby suddenly began shifting and bubbling.
“Ohhhhh sweet, oh great!" Gauglitz exclaimed. "That is really a good experiment, I really like that.”
If the bubble retention theory proves true there won’t be as much space in stable underground tanks as Hanford managers thought. And they would have to work on new solutions.
“DOE is doing the prudent thing, making sure that we don’t go above some limit until we know that it’s safe,” says says Jim Alzheimer, a top engineer with Washington’s Department of Ecology.
The consequences are so great that a top federal watchdog the Defense Nuclear Facilities Safety Board is paying close attention. It’s technical director says there’s no room for doubt on this.
The federal research on deep sludge gas is scheduled to be published by next summer.