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New Study Helps Differentiate Local from Global Sources of Plutonium Pollution in Soil

Scientists analyzed extremely low levels of plutonium pollution present in the soils and made a discovery that could power future 'clean up' operations on land near nuclear power plants, which would be time- and cost-efficient.

Professor Malcolm Joyce. Image Credit: Lancaster University.

The researchers demonstrate how they have quantified the earlier 'unmeasurable' and took a step ahead in distinguishing between local and worldwide sources of plutonium pollution present in the soil. The findings have been published in the Nature Communications journal.

The researchers determined the isotopic 'fingerprint' of trace-level amounts of plutonium present in the soil, which corresponded with the isotopic fingerprint of the plutonium made by an adjacent nuclear reactor.

Thus, they could evaluate levels of plutonium in the soil attributable to reactor pollution and differentiate this from plutonium from usual pollution across the world.

This is essential to offer crucial data to those accountable for environmental evaluation and clean-up.

Long ago, plutonium formed in the big bang that decayed away. However, minuscule amounts can still be found in the surroundings because of reactions in naturally occurring uranium in the ground, and as a result of human activity.

The latter take place local to their source of production, for instance, from reactor accidents, nuclear plant effluents, and accidents that involve plutonium-powered space probes and nuclear weapons. They happen worldwide from the fallout from atmospheric nuclear weapon tests that occurred between the 1950s and 1980.

When there is a lack of human intervention, the quantity of plutonium in the Earth changes very gradually with time as a result of the long half-lives of a majority of the plutonium isotopes and comparatively slow natural transport mechanisms.

The potential to distinguish between universal fallout and local sources of plutonium is essential to make decisions regarding nuclear legacies, specifically the clean-up of contaminated land.

In this context, the study intended to find out whether the local contribution to determine plutonium levels on the site of a fast breeder nuclear reactor might be distinguished from the universal contribution.

Accelerator mass spectrometry (one of the most sensitive methods to quantify plutonium) helped scientists from Lancaster University, ETH Zürich, and Dounreay Site Restoration Ltd to show that this was viable. The researchers added that the results of the study could help determine the extent to which clean-up of the local plutonium may be essential.

Plutonium is primordially extinct but that does not mean we don’t find it in the earth. Up until 1980 many nuclear weapons were tested in the atmosphere—this coupled with other forms of pollution, has resulted in trace levels of pollution.

Malcolm Joyce, Professor and Principal Investigator, Lancaster University

Our study showed we’ve measured what one might have assumed was ‘unmeasureable’, differentiating between two very different sources of trace amounts of plutonium, hence demonstrating that it is possible to measure this extraordinarily low-level indicator of human activity if we need to do so,” added Joyce.

The study authors are Chris Tighe, Claude Degueldre, Kirk Semple, and Malcolm Joyce from Lancaster University; Maxi Castrillejo and Marcus Christl from ETH Zürich; and Jeremy Andrew from Dounreay Site Restoration Ltd.

Journal Reference:

Tighe, C., et al. (2021) Local and global trace plutonium contributions in fast breeder legacy soils. Nature Communications. doi.org/10.1038/s41467-021-21575-9.

Source: https://www.lancaster.ac.uk/

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