Gamma Decay
Light Sound and Waves

The Goiânia incident

Stories from Physics for 11-14 14-16 IOP RESOURCES

In 1985, a private radiotherapy clinic in Goiânia, Brazil was being moved to new premises. During the course of the transfer, a caesium-137 teletherapy unit was stolen by two people who believed it might have scrap value. The individuals took the source assembly home and attempted to dismantle it, rupturing a capsule which contained caesium chloride, a source of gamma radiation. The men sold the remnants of the source assembly to a junkyard. The owner of the yard noticed that the material glowed blue in the dark.

Over the following days, friends and relatives of the owner came to observe the striking phenomenon and some of the visitors took small fragments of the material away with them. A six year-old girl handled pieces of the source bare-handed whilst eating a meal. After five days, some of those exposed to the radiation began to complain of gastrointestinal symptoms but their conditions were not initially linked to radiation exposure.

A concerned relative took some of the material to the health authorities. She travelled by bus, carrying the caesium in a bag, and placed it on the desk of a doctor, reporting that the material was: “killing her family”. The doctor happened to know a medical physicist who, by chance, was visiting the organisation. In order to determine the nature of the material, the physicist borrowed a scintillometer from a government nuclear agency. Even when he was some distance from the bag containing the fragments, the meter went to full-scale deflection. This unlikely reading led the physicist to assume that the meter was defective, so he returned to the nuclear agency to collect a different scintillometer.

Whilst the physicist was away, the health authority doctor became concerned and called the fire brigade. The physicist only just returned in time to stop the firemen from throwing the source into the river. He argued for the immediate evacuation of the health authority building and the junkyard premises and 22 people were identified as having had a high level of exposure to the source. In total, 249 people had detectable exposure to radiation as a result of the incident, four people died from irradiation and several others required hospital treatment.

In 1988, The International Atomic Energy Agency described the incident as: “one of the most serious radiological accidents to have occurred to date”.

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