A Hanford vault weighing about 1,100 tons is expected to be rolled out of the ground just north of Richland Friday, weather permitting.
The 340 Vault is one of just two complex radioactive facilities that still need to be demolished or removed at the Hanford 300 Area by Department of Energy contractor Washington Closure Hanford.
The list of complex facilities there dropped from three to two in January when the massive Plutonium Recycle Test Reactor, weighing 1,082 tons with its shielding, was lifted out of the ground.
Like the test reactor, the 340 Vault will be loaded onto a heavy-haul trailer with hundreds of wheels to distribute its weight, then slowly driven to a lined landfill for low-level radioactive waste in central Hanford.
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Route 4 South from just north of Richland to the Hanford Wye Barricade is expected to be closed during the transport, likely sometime this weekend when traffic near Hanford is light.
The work had been planned for last weekend, but postponed because of the snow.
"This will be another big piece of work accomplished on the river corridor and it has been done successfully so far," said Larry Gadbois, an Environmental Protection Agency scientist.
The removal of the test reactor and the 340 Vault will clear the way to advance work on other contaminated infrastructure below ground, including a piping system that is expected to have some high radioactivity, Gadbois said.
The underground vault, just north of Richland, was once used to hold two 15,000-gallon stainless steel tanks that collected highly radioactive liquids through a system of underground piping from laboratories, fuel fabrication facilities and test reactors in the 300 Area. The tanks have been filled with grout.
The 340 Building, also called the Waste Neutralization Facility, next to the vault was torn down in 2011 and in 2012 and about 54,000 tons of soil were dug up, leaving the underground vault in a hole on a pedestal of soil.
Preparations to lift the vault have been complicated not only because of its weight and radioactive contamination, but because it sits on soil.
Workers drove four steel pipes horizontally through the soil platform underneath it. As the 3-foot diameter pipes were pushed through, an auger mined the soil out of the pipe. The pipes were then filled with concrete to help sustain the weight of the vault.
The vault is made of steel-reinforced, high-density concrete. It measures about 40 feet long, 29 feet wide and 25 feet high.
As the fourth pipe, or casing, was driven into the soil, radioactive contamination was found beneath the vault in the area of the vault's sump. Sampling with radioactive probes showed cesium-, strontium- and americium-contaminated soil in a four- to six-foot diameter area.
That slowed work, but much of the contaminated soil was augered out by the installation of the fourth casing and then taken to the central Hanford landfill, called the Environmental Restoration Disposal Facility. A remote-controlled excavator typically used for mining was deployed under the vault to remove additional soil.
With soil removed, steel beams were inserted underneath the vault to attach to a lift frame and allow a crane to lift it up 11 feet so the concrete pipes could be pulled out.
Workers then were able to slide a huge steel pan under the vault. It was jacked up and then grouted in place to prepare it for shipment to the landfill, Gadbois said.
As the soil was excavated to reveal the underground vault, a dirt road was built sloping into the hole to drive the transport trailer down to the vault and then under it. A concrete pad was poured under the vault to prevent the trailer from sinking into the soil once the vault was loaded.
The transport weight of the trailer is expected to be about 1,500 tons.
Once the vault is taken away, the only complex facility left to be removed by Washington Closure in the 300 Area is the 324 Building. It sits over a spill of highly radioactive material.
Initial radiation readings in the contaminated soil beneath the vault found radiation exposure rates up to 17 rad per hour. But radiation exposure rates for cesium and strontium under the 324 Building are as high as 8,900 rad per hour. Some engineering work on a system to remove that soil with the building standing is expected to be done this year.
The 300 Area is expected to continue to be an active environmental cleanup site for more than a year. The remaining work includes removing the underground concrete structure where the Plutonium Recycle Test Reactor was housed until a few weeks ago, plus piping and waste sites associated with it.
The former badge house, which is not a contaminated or complex facility, also must come down. Conventional demolition techniques will be used.
DOE plans to complete most environmental cleanup in the 300 Area by fall 2015, with the exception of the 324 Building.
-- Annette Cary: 582-1533; email@example.com; Twitter: @HanfordNews