What is Vitrification Tri-City Herald 10feb02

Vitri-what? Here's a primer 

Vitrification comes from the Latin word vitrum, meaning glass, which is what the government wants to make out of Hanford's worst radioactive liquids.

The idea is to melt the waste and silica, forming the molten mixture into glass logs that won't ooze into the environment.

Right now, some of Hanford's 53 million gallons of chemical and radioactive wastes are stored in sometimes leaky underground tanks, some of which date to World War II.

Of the 177 tanks at the site, about 67 are known or suspected to have leaked about 1 million gallons into the ground water, which is inching toward the Columbia River.

The $4 billion cleanup project calls for vitrifying about 10 percent of that tank waste by 2018. That's 10 percent by volume, but is 25 percent of the radioactivity in Hanford's tanks.

The glass logs then will be stored in steel tubes to wait a few thousand years for the radioactivity to dissipate.

Vitrification: How Nuclear Waste is Turned into Glass

Seattle Post-Intelligencer

In the glassmaking process that BNFL proposes to adapt to Hanford’s tank waste, Sellafield workers turn radioactive liquid into equally radioactive, but more stable, black glass. At the end, the waste is encased in a 4-foot-high stainless steel canister that resembles an old-fashioned milk can (photo with cutaway at right). At Sellafield, the boxy, windowless Vitrification Plant contains enough bewildering pipework to stretch from England to France. Humans cannot enter the "hot cell" where the transformation takes place, so workers must monitor the assembly line shielded by thick concrete and lead walls and watch through windows made of three-foot thick, solid lead glass.

• See a step-by-step illustration of how the process works at Sellafield:
• Steps 1-4  High-level waste is burned and the residue mixed with glass.
• Steps 5-7  The resulting compound is decontaminated.
• Step 8 Glass logs are put into storage.

1. High-level waste, currently in tank storage, is pumped into the vitrification plant's highly active liquor tank.
2. Then, it is fed into a rotating tube inside a heated furnace. Here, the liquid isn't aspirated and dried into a powder.
3. The dried powder is fed into a melting pot together with glass making material at a ratio of 25 percent waste to 75 percent glass. Over the course of about 8 hours, a powder in glass fuse together.
4. The molten mixture is poured into a 4-foot-high stainless steel canister that is waiting under the melter. The canister resembles an old-fashioned.
5. The lid is closed on the container by can automatic fusion welding technique.
6. It is then moved to a decontamination area where high-pressure water jets scrubbed off loose surface contamination.
7. The container is remotely inspected by TV cameras before it is transferred inside a shielded flask and take into the cavernous but brightly-lit Vitrified Product Store.
8. Inside the store, operators (and visitors) can walk on the floor above the compartment where 1,526 canister is containing glass logs are kept inside the flasks, whose location in sealed compartments underfoot is marked by the hundreds of black, disc-like lid is about 30 inches in diameter in the floor. Overhead, huge yellow cranes on permanent tracks slowly transport the container is inside the flasks and insert them into their places in the floor. They can be Kept there for 7 to 50 years.

source: http://seattlepi.nwsource.com/specials/eternity/vitri1.html 12jan03