The first of six massive doors to shield against radiation has been installed by Bechtel National workers within the Hanford Waste Treatment Plant's building to treat high-level radioactive waste.
The 50-ton shield door at the vitrification plant's High Level Waste Facility had to be precisely placed down to five-thousands of an inch, or less than the diameter of a human hair, to ensure a tight fit.
"Keeping workers and the environment safe requires extremely exacting tolerances," said Erik Olds, Department of Energy spokesman.
Precision optics were used to install the door, and its placement was verified with a laser tracker, said Scott Neubauer, Bechtel's superintendent for the High Level Waste Facility. The laser technology was developed for the aerospace industry.
"This technology is one of the few that provides accurate measurements to the precision this project requires," he said in a statement.
The $12.2 billion vit plant is being built to turn much of the 53 million gallons of radioactive waste held in Hanford's underground tanks into a stable glass form for disposal. The waste is left from the past production of plutonium for the nation's nuclear weapons program.
After the tank waste is separated into low-activity and high-level waste streams at the plant's Pretreatment Facility, the high-level waste will be sent to the High Level Waste Facility, where the first steel door has been installed in the melter area at the heart of the building. The door is 8 inches thick and stands 15 feet tall and 18 feet wide.
The building will have two 90-ton melters that will heat radioactive waste mixed with glass former to 2,100 degrees. The mixture then will be poured into log-shaped stainless steel canisters, sealed and prepared for storage and then planned disposal at a national repository.
The melters are expected to be used for five years before being removed and replaced, a process that requires the series of shield doors and a remotely operated rail-and-airlock system to protect workers from radiation.
Each melter will have a series of three shield doors that will be opened and closed in sequence as the contaminated melters are removed. Each melter will be encased in a 250-ton container.
The first shield door installed was one of the two that will be closest to the melters.
The plant, which covers 65 acres, is a little more than 50 percent complete and is scheduled to start treating waste in 2019.