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Nuclear Waste Program

Tank Storage, Operations & Closure (TSOC) Project

Hanford’s 177 underground tanks are in the central part of the site, in 18 groups known as “farms”. The tanks hold a total of about 56 million gallons of high-level radioactive and chemical waste. The waste was created when irradiated fuel rods were processed to produce plutonium for nuclear weapons. The waste is a mixture of liquids, solids, and sludge.

Project Mission

  • Regulating how tank waste is safely stored with the Hanford Dangerous Waste Permit.
  • Ensuring that the U.S. Department of Energy (USDOE) maintains single-shell tanks (SSTs) and double-shell tanks (DSTs), preventing releases to the environment and conducting safe operations.
  • Overseeing the retrieval of waste from SSTs, transfer of waste to DSTs, and the eventual closure of tanks.

In SST farms, Ecology oversees waste retrieval, interim stabilization, leak detection, waste characterization, system inspections, safety, and groundwater issues. In DST farms, Ecology oversees operations, system upgrades, permitting, safety, waste characterization, inspections, and waste volume projections.

Tank History

The 149 SSTs were built between 1943 and 1964, and are well beyond their designed life of 20 years. Dozens of these tanks are known to have leaked in the past.

There are 28 DSTs built between 1968 and 1986. The DSTs receive waste from SSTs as they are emptied. In 2012 a leak from the inner tank to the annulus of one DST, AY-102, was discovered. All DSTs are now being reviewed for soundness.

Diagram showing ways waste from Hanford tanks ended up in soil and groundwater. (Click image to enlarge.)
Diagram showing ways waste intended for Hanford tanks ended up in soil and groundwater. (Click image to enlarge.)

Impacts to the Environment

More than one million gallons of waste is believed to have spilled or leaked to the environment in the tank farms. Some releases were due to tank liner failures; many were due to pipeline breaks or overfilling.

Waste from past tank system leaks has reached groundwater and is moving toward the Columbia River. The distance to groundwater under the tanks farms is about 200 to 300 feet.

Tank Waste Retrieval

In 1999, Ecology negotiated an agreement with the USDOE to move pumpable liquid from the SSTs into DSTs, a process known as “interim stabilization.” The goal of interim stabilization was to reduce the risk of further leaks to the environment. More than three million gallons of liquid waste has been moved from the SSTs into the DSTs.

After completing interim stabilization, USDOE started retrieving sludge and solid waste from SSTs and moving it to the safer DSTs. To date, no waste from DSTs has leaked to the environment.

Waste retrieval has been completed in 15 tanks so far. To determine if waste retrieval is finished, Ecology reviews USDOE’s data to determine whether they have met the requirements of a Consent Decree. The agreement requires that no more than 360 cubic feet of waste, or less depending upon tank size, remains in a tank after retrieval. If they do not meet the retrieval goal using one technology, they must use a second technology and then a third if necessary and advantageous.

An evaporator supports the tank retrieval process by removing excess water and decreasing waste volume.

Closure of Tank Waste

Eventually, the waste will be transferred from DSTs to the Waste Treatment Plant for vitrification. Please visit our Tank Waste Disposal Project page for more info.


Double Shell Tanks Explained

AY-102 Pumping Order

Frequently Asked Questions: Leaking underground tanks at Hanford (web page)

Hanford Tanks (PDF newsletters)

Tank Closure Topics (PDF newsletters)

Tank Closure 101

Retrieving Tank Wastes at Hanford: The Basics

The Scoop on Hanford Tanks, Part 1, Tanks are Out There! (YouTube video)


Jeff Lyon, Project Manager

Ginger Wireman, Community Outreach & Environmental Education

Ecology: 509-372-7950