What’s Inside The Suspect Nuclear Waste Tank At Hanford?

Rendering of Hanford’s Double-Shell Tanks (DOE image)

What’s Inside The Suspect Nuclear Waste Tank At Hanford? (Forbes, Aug 27, 2012):

When news broke last week that radioactive material had been found outside of the inner containment wall of a double-hulled tank at the nuclear waste cleanup site in Hanford, Wa, most reports characterized the contents of the tank as “radioactive waste.”But that’s more a category than a description.

The Energy Department has been eager to find out exactly what’s in the tank, which received wastes from leaky single-walled tanks and from more than a half dozen facilities at the Hanford site, including nuclear reactors, plutonium processing plants, a PUREX plant, and laboratories.

DOE funded many studies to analyze the chemical compounds in the tank, determine whether they could corrode the stainless-steel walls, and to anticipate the effects of a spill. Here’s some of what those studies found:

Hanford tank AY-102 contains 857,000 gallons of waste in the form of a brown sludge stewing from the heat of its own decay in a translucent yellow liquid at 110 to 135 degrees.

(The two deposits of highly radioactive material found this month between the walls of the tank are dry, according to DOE, and one of them is described as white. Officials plan to sample the material again in mid-September in the hope that its composition will reveal its source.)

The sludge inside the tank contains chunks of solids, many common metals—including aluminum, nickel, lead, silver, copper, titanium, and zinc—and other common elements. In 2001, DOE added sodium hydroxide and sodium nitrate to discourage the toxic sludge from corroding the tank. In a 2002 study, researchers found the sludge to be within standards that should not corrode the tank.

The most prominent radionuclides found within Tank AY-102, and their associated health risks, are:

URANIUM 235 and 238 are the natural isotopes of uranium commonly used in nuclear weapons and reactors. They are hazardous, according to the EPA because, “about 99 percent of the uranium ingested in food or water will leave a person’s body in the feces, and the remainder will enter the blood. Most of this absorbed uranium will be removed by the kidneys and excreted in the urine within a few days. A small amount of the uranium in the bloodstream will deposit in a person’s bones, where it will remain for years.”

PLUTONIUM 238, 239, 240 and 241. Plutonium is not easily ingested, according to EPA, but if inhaled it can remain in the lungs or travel to the bones and liver.

STRONTIUM 90, a “bone-seeker” that the body mistakes for calcium and deposits in bones. A tiny amount of strontium 90 from the Fukushima disaster was found last year in milk in Hawaii.

• CESIUM 137, a more familiar radionuclide from Fukushima fallout, is distributed throughout the body’s soft tissues.

• THORIUM is a widely available radioactive element championed by some as a safer nuclear-energy source. According to EPA, “studies have shown that inhaling thorium dust causes an increased risk of developing lung cancer, and cancer of the pancreas. Bone cancer risk is also increased because thorium may be stored in bone.”

OTHER RADIONUCLIDES detected in one or more studies of Tank AY-102 include carbon 14, cobalt 60, selenium 79, technetium, antinomy, neptunium 237, americium 241 and curium 243/244.

The Hanford facility opened in 1943 to supply atomic materials to the Manhattan Project and produced plutonium for weapons through the Cold War. A very gradual shut down began in the 1960s. in 1989, the government began its cleanup of the site, which includes a controversial vitrification plant that has cost more than $12 billion so far. There are 53 million gallons of radioactive and chemical waste stored on the campus.

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