“Hurry up and wait” is a phrase most people pick up in the military or at the DMV. The crew that runs one of the Hanford Site’s waste treatment systems in southeastern Washington just spent about six months living it.<\/p>\n
The system’s called Tank-Side Cesium Removal, or TSCR, and the Department of Energy said on September 15<\/a> that it’s running again. TSCR finished its last batch of radioactive waste on February 25. Normally, according to DOE, crews need about two weeks to turn it around for the next one. This time it sat for about six months, because the tank it empties into was too full to take any more.<\/p>\n That tank’s called AP-106, and it’s now holding about a million gallons of waste that’s already been through TSCR. DOE describes AP-106 as a 1.1-million-gallon tank<\/a>.<\/p>\n So yeah, it’s pretty full.<\/p>\n Hanford’s underground tanks hold sludge, salt cake and liquid left over from decades of plutonium production, and TSCR only deals with the liquid. It runs that liquid through a filter to catch any solids still in it, then through three steel columns packed with tiny beads that latch onto cesium. Hanford’s own fact sheet on the system<\/a> actually calls those columns filters, too. It says the solids and cesium the system pulls out make up 99.9% of that waste stream’s radioactivity.<\/p>\n If you’ve got a water filter pitcher in your fridge, you already understand the basic idea. You get about as much water out the bottom as you poured in the top. The filter just keeps some of what was in it.<\/p>\n Keep that in mind when you see the 99.9% figure, because it measures radioactivity. What comes out of TSCR is a lot less radioactive, which lets the low-activity side of Hanford’s glass plant accept it, but there’s still pretty much as much liquid as there was going in. All of it has to go somewhere.<\/p>\n The cesium stays behind in the columns. Once the beads can’t hold any more, crews pull a column out and put a fresh one in, and DOE treats that swap as the end of a batch. New columns weigh about 24,000 pounds apiece, according to DOE, and the used ones go onto a concrete storage pad next to the system until they can be moved for permanent disposal. DOE’s September release even includes a photo of one being pulled out in March, after the last batch wrapped up.<\/p>\n The tank’s there to feed the Waste Treatment and Immobilization Plant, which most people at Hanford call the Vit Plant. That’s where pretreated waste gets mixed with glass-forming material, brought up to 2,100 degrees Fahrenheit and poured into stainless steel containers, and we’ve covered that furnace before<\/a>. The plant started hot commissioning last October. That’s basically its first stretch running on real radioactive waste before it counts as fully operational.<\/p>\n Since then, AP-106 has sent the plant a little over 242,000 gallons of TSCR’s output. DOE itself points out that’s about the size of a single TSCR batch.<\/p>\n So how long would it take to work through a million gallons at that pace?<\/p>\n Close to four years, if you do the napkin math on the last 11 months. That’s probably unfair to the plant, which is still in hot commissioning and which DOE’s been waiting on to ramp up. But it does explain why the filters upstream spent most of this year sitting still.<\/p>\n TSCR, meanwhile, was designed to move waste at about five gallons a minute, according to DOE. That’s what two showerheads put out at the federal limit of 2.5 gallons a minute each, and it doesn’t sound like much. It adds up if the system runs around the clock, though, and at that rate a batch like the current one takes about a month.<\/p>\n Ken Langdon, president of Hanford Tank Waste Operations & Closure, the contractor that runs the site’s tanks, said as much in DOE’s release. The site is “retrieving and pretreating waste faster than it can be immobilized” by vitrification alone, he said. Admittedly, a pretreatment system that outpaces the plant it feeds is a pretty good problem to have, as nuclear waste problems go.<\/p>\n What I can’t tell you is exactly how much room AP-106 has right now. DOE hasn’t given a figure more precise than about a million gallons, and TSCR’s current batch is adding to it as we speak. I’d assume the Vit Plant keeps drawing from the tank while TSCR fills it, but that’s me guessing rather than something DOE’s spelled out.<\/p>\nSo what’s a cesium filter doing next to a nuclear waste tank?<\/h2>\n
Hanford’s glass plant is still warming up<\/h2>\n
So when did the pause actually start?<\/h2>\n