On this day September 13, 1987

A radioactive item was scavenged from an abandoned hospital in Goiânia, Brazil, resulting in four deaths and serious contamination in 249 others.

Cherenkov radiation

Cherenkov radiation

On 13 September 1987, an old radiation source was scavenged from an abandoned hospital in Goiânia, the capital of the central Brazilian state of Goiás.

It was subsequently handled by many people, resulting in four deaths and serious radioactive contamination in 249 others. Time magazine has identified the accident as one of the world’s “worst nuclear disasters”.

The object was a small, highly radioactive thimble of caesium chloride (a caesium salt made with a radioisotope of caesium) encased in a shielding canister made of lead and steel with an iridium window. The source was positioned in a container of the wheel type, where the wheel turns inside the casing to move the source between the storage and irradiation positions.

The source contained 74 terabecquerels (TBq) in 1971. The International Atomic Energy Agency (IAEA) describes the container—51 millimeters (2 inches) in diameter and 48 millimeters (1.8 inches) long—as an “international standard capsule.” The specific activity of the active solid was about 814 TBq·kg-1 of caesium 137 (half life of 30 years).

The dose rate at one meter from the source was 4.56 gray per hour (456 rad·hr−1). While the serial number of the device was unknown, thus hindering definitive identification, the device was thought to be made in the United States at Oak Ridge National Laboratory and was used as a radiation source for radiation therapy at the Goiânia hospital.

Afterwards, about 112,000 people were examined for radioactive contamination; 244 were found to have significant levels of radioactive material in or on their body. Of this group 129 persons had internal contamination. The majority of the internally contaminated persons only suffered small doses (< 50 mSv, less than a 1 in 400 risk of getting cancer as a result).

1000 persons were identified as having suffered a dose which was greater than one year of background radiation; it is thought that 97% of these people had a dose of between 10 and 200 mSv (between a 1 in 2000 and a 1 in 100 risk of developing cancer as a result).

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