In 1985, Aboriginal families returned to live on their lands at Maralinga in South Australia. Yet the major cleanup of the British nuclear tests did not begin until a decade later. A 2021 study clarifies what the soil still retains, while restrictions persist.
Seven atomic explosions at Maralinga in 1956 and 1957, but the minor trials pollute the site far more
Between September 27, 1956 and October 9, 1957, Great Britain detonated seven nuclear devices at Maralinga. The Buffalo operation included four detonations, followed by three more in the Antler operation. Their yields ranged from 1 to 27 kilotons, but they are not responsible for the bulk of the contamination.
The minor trials, conducted up to 1963, are the main cause. These tests involved no nuclear explosions, only conventional explosive charges. They indeed dispersed plutonium over smaller areas, but at higher concentrations.
On the sole site at Taranaki, the Vixen B trials dispersed about 22 kilograms of plutonium-239. This isotope has a half-life of roughly 24,100 years. Thus, its radioactivity would diminish by half only after this very long period.
Anangu families relocate to Oak Valley in 1985, ten years before the grand cleanup of the test site
In January 1985, a full ownership title returns to the Aboriginal people of Maralinga Tjarutja. The Maralinga Tjarutja Land Rights Act of 1984 governs this transfer. Then, in March, Anangu families move to , located 128 kilometers from the village of Maralinga.
But the McClelland Royal Commission found in 1985 that significant radiological risks remained, especially at Taranaki. The grand nettoyage does not begin until 1995 and lasts until 2000. The teams then bury the most contaminated soil and debris in trenches.
In 2021, a Monash team analyzes six radioactive particles that could slowly release plutonium
In 2021, however, a team from Monash University revisits the matter in Scientific Reports. Megan Cook leads this work on six radioactive grains of a few hundred micrometers. They analyze these grains with a British synchrotron and an ion beam.
These grains, called hot particles, form from the cooling of droplets of molten metal in the explosion plume. Their structure turns out to be more complex than expected. According to co-author Vanessa Wong, these results profoundly alter the understanding of grains among the best-studied in the world.
The authors deem a possible slow release of plutonium, via several chemical and physical processes. This phenomenon probably contributes to the uptake of this metal by the fauna of Maralinga. However, in the six grains studied, plutonium remains largely trapped, while uranium moves more readily.
Around Taranaki, permanent occupation remains limited, as no cleanup removes all contamination
ARPANSA, Australia’s radioprotection agency, estimates that most of the contaminated zones meet the open-use standards. Hunting, mining, and construction remain possible, according to the agency. Yet precautionary restrictions limit permanent occupancy around Taranaki and deter any intrusion into the trenches.
In November 2009, an agreement returns the site and the village of Maralinga to the traditional owners. Megan Cook regards Maralinga as among the best-monitored sites of its kind. She concedes, however, that one never recovers all the contamination, because “it simply isn’t possible.”
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