The Secret 1949 Radiation Experiment That Contaminated Washington State

By Sarah Zhang on at

The physicists who invented the nuclear bomb worked out of Los Alamos in California, but the people who did the dirty work of making the bombs were in Hanford, Washington. Throughout the Cold War, Hanford churned out plutonium for our nuclear arsenal. It was also, conveniently, a place to experiment with radiation.


The Secret 1949 Radiation Experiment That Contaminated Washington

Workers at Hanford (via)




Hanford, Factory and Farm

The Secret 1949 Radiation Experiment That Contaminated Washington

The B reactor at Hanford under construction.

When Hanford broke ground in 1943, residents nearby in eastern Washington knew it was a war construction project but not much else. Under the then-secret Manhattan Project, Hanford’s reactors produced the plutonium for the first nuclear bomb, dropped at the Trinity site in 1945, and Fat Man, dropped on Nagasaki. Only after the war was Hanford’s true purpose widely known.

As the U.S. entered the Cold War, Hanford grew. Its nine reactors together processed enough plutonium for 60,000 bombs. Rural eastern Washington became the Atomic Frontier.

Hanford was always more than a production facility; it was also a research complex. Up to 1,000 animals were housed on a farm near reactor F for experiments on the effects of radiation. The animals included fish, dogs, pigs, sheep, and even alligators. Sheep, especially, were given feed with iodine-131, the same radioactive material that the reactors were discharging into the air.

The Secret 1949 Radiation Experiment That Contaminated Washington

Hanford workers feeding radioactive food to sheep. DOE

The Secret 1949 Radiation Experiment That Contaminated Washington

Testing a sheep’s thyroid for radiation.

Spying on the Soviets

The “Green Run” sounds benign, even pleasant, but its name has more dangerous origins. Normally, irradiated uranium fuel is cooled for up to 101 days before it is processed, so that short-lived radioactive elements like iodine can decay. In the Green Run, the fuel was cooled just 16 days; it was still “green.”

Carl Gamertsfleder, then Hanford’s Health Instruments Deputy Chief, later told the Spokane Chronicle, that the “green” order came from the military, who assumed the Soviets were rushing to produce nuclear bombs. If the Soviets were short-cooling their fuels, the radioactive results might be spotted some distance away. So Air Force wanted to fly planes behind a radioactive test plume, to test out their own instruments.

The Secret 1949 Radiation Experiment That Contaminated Washington

Image: The first page of Hanford scientists’ once classified report on the Green Run, titled “Dissolving of Twenty Day Metal at Hanford.” (via)

That’s why, on the night of December 2, 1949, Hanford employees processed one ton of 16-day-old fuel without filtering the exhaust, releasing 7,000 to 12,000 curies of iodine-131 in the air. It was two to three times as much as they intended. The experiment also went forward despite, Gamertsfleder claimed, reservations about weather. “We knew what the weather was and we didn’t want the release to be done then,” he told the Chronicle, “On the Columbia River it probably got as many people as it could.”

The radioactive iodine-131 spread over a 200-by-40 mile plume, which was, actually, too small. That meant much of the iodine-131 made it onto the ground, in higher than desired concentrations. The vegetation in nearby communities had readings of 0.1 to 4.3 microcuries/kg, ten to hundreds of times higher than the “permissible permanent concentration.”


In the decades since, committees and researchers have revisited the question of whether the Green Run’s iodine-131 endangered the health of people living downwind. The answer, according to official sources, is no.

Iodine travels through tainted food and milk, and the Green Run happened in winter, when few people were harvesting vegetables from the ground and few cows were grazing. A Congressionally mandated study could not find a link between thyroid disease caused by iodine-131 and releases of the material by Hanford, during the Green Run or otherwise.

But, as secret government experiments do, the Green Run bred suspicion and mistrust. In 2005, a lawsuit filed on behalf of 2,300 downwinders finally had its had in court. Of the first six plaintiffs, two who had thyroid cancer were awarded $500,000/£325,234 in damages—too little for the rest of the cases to continue.

That’s pretty much where the story ends with the Green Run, a largely-forgotten episode of history in a largely-forgotten place. But Hanford still bears the scars of the Cold War, and the Green Run is an unsettling example of what the government has done in the name of keeping its citizens safe.