Tank Waste

Background

The Hanford Tank Farms house 53 million gallons of high-level radioactive and chemical waste that is the byproduct of “reprocessing” spent nuclear fuel.* The high-level waste is stored at Hanford’s 200 Area in massive underground tanks – 177 in total, most of them several decades past their design life and 1/3 of them confirmed leakers – a few miles from the Columbia River.

Tanks under construction

Tanks under construction

This waste is deadly stuff; toxic, highly radioactive and producing gases that must be vented to prevent catastrophic explosion**.

A clear picture of tank waste contamination in the soil and groundwater at Hanford has not really emerged – due to the complexity of the task and years of government denial and failure to fund adequate characterization.  One million gallons of this waste is officially acknowledged to have leaked from the tanks, but a 1998 study by Department of Energy scientists estimated the total leaks 6 times that amount.  Other sources put the amount closer to 10 million gallons with more evidence continuing to emerge***.  With tank waste contaminating the groundwater and the Columbia River, any amount is too much.

Given the weakening integrity of the tanks and serious threat of further contaminating the groundwater, minimizing tank leakage and stabilizing the waste are considered the highest priorities of Hanford cleanup work.

Babysitting radioactive waste

Work at the tank farms mainly involves monitoring conditions within tanks and, when necessary, transferring waste from older, unstable single-shell tanks shell to more modern, stable double-shell tanks.  Essentially, Hanford’s nuclear operators are babysitting the tank waste – an extremely important babysitting job that costs approximately $300 million a year.

Tank Farm Map

The Tank Farms in relation to the entire Hanford Site

Currently the only disposition path to stabilize this waste in a more secure form is vitrification, locking the waste in glass logs.  Unfortunately the Waste Treatment Plant, being built for this purpose will only be able to process a portion of the tank waste, at most.  There is currently no plan for stabilizing the remaining tank waste.

There is talk of constructing more double-shell tanks – a controversial measure which doesn’t solve the underlying problem: un-stabilized tank waste remains a threat to the Columbia River and nearby communities.  New tanks could also represent a weakening commitment by the Department of Energy to truly stabilize the waste and safeguard the river.  Criticism aside, new high-level waste tank construction may be least-bad option available.

Difficult, dangerous, and slow-going work

Tank waste is extremely dangerous due to its lethal mix of radioactivity, hazardous chemicals, and the toxic vapors that are generated by chemical reactions within the tanks. Because of these constant health threats, specially-designed robotic equipment is required and extra precautions for workers are advised, though not always implemented or available.  (Worker exposure to toxic chemical vapors is an ongoing problem that we address in more depth on the Helping Hanford Workers page.)

High-level waste tank

The inside of a high-level waste tank with a thick crust of salt on the surface

Tanks are generally focused on one at a time.  Tank waste from failing single-shell tanks is moved into the double-shelled tanks.  Room in the 28 double shell tanks is becoming increasingly scarce, maximizing the remaining space is an emerging challenge at Hanford.

The Department of Energy is responsible for closing the tank farms.  “Closing” individual tanks is a legal term from the Tri-Party Agreement (which determines Hanford cleanup goals) that means the retrieval of 99% of waste from a tank before it can be declared “closed.”  Since cleanup began, only 7 of the 177 tanks have been closed.  As closures move ahead slowly, often delayed by avoidable worker safety issues, the tanks are getting older and leakier.  We are in a race against the clock.

The tanks are failing

SX Tank

Computer diagram of a cesium-137 plume in the SX tank farm.

The tanks are leaking due to poor tank integrity – the waste is corroding the carbon steel lining. When the tanks were built during the World War II, a shortage of stainless steel necessitated the use of cheaper, less robust carbon steel – this practice continued long after stainless steel was again available.

Carbon steel corrodes in highly acidic environments like those in Hanford’s tanks, so large amounts of other chemicals were added to neutralize the pH in the tanks, minimizing the corrosion problem but making the waste very difficult to stabilize.

The tanks were built to last 20 years.  They were never designed to permanently store high-level radioactive waste. Most of these tanks, 149 of them, are single-shelled and built between 1943 and 1964.  These have far exceeded this 20-year projection.  It is no surprise that they are failing. The double-shell tanks, 28 of them, are double-shelled, built between 1977 and 1986.  The double shell tanks are more robust, but are also made of carbon steel.  To date, none of the double-shell tanks have leaked, but a more secure solution is needed to contain this waste and prevent even more waste from leaking into the groundwater.

SX Tank

Computer diagram of a cesium-137 plume in the SX tank farm.

Despite being completely inadequate for the task, Hanford’s tanks have become the de facto high-level waste storage medium.  With the Waste Treatment Plant looking less and less viable, new ideas for tank waste remediation must be explored now.

END NOTES


* By melting the spent nuclear fuel rods in acid and subjecting the mixture to multiple chemical processes, isotopes like plutonium and uranium can be recovered through reprocessing. However, it is an inefficient process and massive quantities of deadly high-level waste are produced for tiny amounts of recovered plutonium. At Hanford, plutonium and uranium were reprocessed on an industrial scale from the 1940s to the 1980s. High-level waste is a legal term that refers to any waste generated during the reprocessing of spent fuel.

**In 1957, reprocessing waste tank at Russia’s Mayak Facility exploded in the second worst nuclear accident after Chernobyl disaster.

***Hanford scientist-whistleblowers are indicating that tank BX-102 has leaked 20 tons of uranium into the groundwater.

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