Cerium-141

Saturday, June 25th, 2016

In 1945, Eastman Kodak suddenly received a flood of complaints from business customers who had recently purchased sensitive X-ray film:

Black exposed spots on the film, or “fogging,” had rendered it unusable. This perplexed many Kodak scientists, who had gone to great lengths to prevent contaminations like this.

Julian H. Webb, a physicist in Kodak’s research department, took it upon himself to dig deeper and test the destroyed film.

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According to an article Webb would write in 1949 for the American Physical Society, the paper and cardboard used for packaging in the ’40s were often salvaged from wartime manufacturing plants where radium-based instruments were also produced. Radium is a naturally occurring radioactive element that can cause flecks of spots or fogging when “in intimate contact with (sensitive film) for a period several weeks.” During wartime, Kodak took precautions to avoid radium contamination. It moved packaging manufacturing to mills where Kodak had full control over the raw materials.

One of these mills was located along the Wabash River in Vincennes, Indiana; it specialized in producing strawboard, used as a stiffener board between sheets of film. When Webb investigated the mysterious fogging in 1945, he found that it originated not from the X-ray film itself but the packaging, which he tracked to this particular mill, and specifically, the production run of strawboard from August 6, 1945. After testing the radioactive material on the strawboard, he discovered — rather alarmingly — that the spots on the film were not caused by radium nor any other naturally occurring radioactive material, but “a new type radioactive containment not hitherto encountered.” What was this unknown radioactive material, he must have wondered, and what was it doing in southwest Indiana?

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While he was studying the Indiana samples, Webb got word that a particular production run of strawboard from a plant in Tama, Iowa was also contaminated and fogging the Kodak film it carried. While Tama was 450 miles from Vincennes, there were striking similarities. The two production runs of strawboard had been completed within a month of each other. Tama’s radioactive spots also failed the radium test, meaning the cause was something else. Most telling, however, was that both mills sat next to rivers, with Vincennes on the Wabash River and the Iowa River cutting through Tama.

Webb found that the strawboard from both mills had a significant concentration of beta-particle radiation activity but little to no alpha-activity. (Beta-particle radiation can penetrate paper, human skin and are sometimes considered dangerous. Alpha-particle radiation is stopped by paper, easily absorbed and generally considered safe if not ingested). Additionally, photographic evidence allowed Webb to estimate the half-life of the artificial radioactive material he was seeking at approximately 30 days. The results corresponded to the presence of an artificial radioactive material he would later identify as Cerium-141, which is “one of the more prolific fission products of the atom bomb.”

Furthermore, Webb concluded there was no possible way the straw could be the carrier of the containment, since it was stored in warehouses (and not outside) for a considerable amount of time prior to being used. Had the Cerium-141 gotten directly into the straw, it would have decayed by the time the straw was processed, rendering the radiation hardly detectable. This brought Webb to a frightening explanation: The contamination came from the river water. Additional evidence would fall in the rain. According to Webb, “stronger activity occurred in the strawboard” after periods of heavy precipitation, establishing that the radioactive material was being deposited via precipitation and came from a far-flung place.

While it is unclear whether Webb knew about the Trinity test when he was conducting his research in 1945, his report from 1949 is unabashedly clear: “The most likely explanation of the source of this radioactive contaminant appears to be that it consisted of wind-borne radioactive fission products derived from the atom-bomb detonation in New Mexico on July 16, 1945.”

The problem came up again later:

On January 27, 1951, the first atomic detonation at the new Nevada Proving Ground took place. Days later and 2,500 miles away, a Geiger counter at Kodak’s headquarters in New York state measured radioactive readings 25 times above normal after a snowstorm. Declassified 1952 documents obtained by Popular Mechanics reveals that Kodak alerted the Atomic Energy Commission about this out of concern this testing would wreck its film just as had happened in 1945. The AEC responded that it would look into it, but assured Kodak there was little reason to worry, even allowing the company to issue a press release to the Associated Press stating that snow “that fell in Rochester was measurably radioactive…” but “there is no possibility of harm to humans and animals.”

In March 1951, a frustrated Kodak threatened to sue the U.S. government for the “considerable amount of damage to our products resulting from the Nevada tests or from any further atomic energy tests…” Finally the company and the government came to an agreement. The AEC would provide Webb, by now the head of Kodak’s physics division, with schedules and maps of future tests so that Kodak could take the necessary precautions to protect its product. In return, the people of Kodak were to keep everything they knew about the government’s Nevada nuclear testing a secret.

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