New study finds that depleted uranium particles are long-lived in environment
Campaigners have long argued that DU residues from conflict present a long-term risk to civilians. Not only is this due to the rate of radioactive decay from the isotopes in DU – and indeed DU gets more radioactive for thousands of years due to the in-growth of decay products – but also because of the rate at which DU dust particles and intact or fragmentary penetrators corrode.
Two new studies from the UK have now shed more light on the processes that impact on DU’s environmental persistence. The studies were undertaken at the UK’s two DU firing ranges, Kircudbright in Scotland, where DU rounds are fired into the sea, and Eskmeals in England, where DU was fired into hard targets to examine its effectiveness against different types of armour.
Entrance to the Eskmeals range, now operated by Qinetiq, Cumbria, UK.
The testing at Eskmeals produced considerable quantities of DU dust, some of which was found to have spread 6km from the site to the nearby village of Milom. Researchers took samples of DU particles from the site and subjected them to analysis to assess how they had changed over the 30 years since they were produced. Given the high rainfall and oxidising conditions at the site, surprisingly the researchers found that:
“The persistence of U oxide phases such as U3O7 and U3O8 reﬂects the low solubility and mobility of the primary species in surface soils at the Eskmeals site. However, the presence of primary impact particles results in the persistence of health risks associated with inhalation, should these particles be disturbed.”
In other words, the uranium oxides particles that had been produced by the testing were found to be highly resistant to corrosion and as a result, 30 years after firing the particles would still present an inhalational hazard if resuspended. This finding fits with the results of a study around a former speciality metals factory in Colonie north of New York. Researchers there showed that particles produced between the 1960s and 1980s were still intact and present in the environment. In that case the particles had been produced through the incineration of DU, not by its use in weapons. However this new study demonstrates that DU residues from munitions use are similar in composition and persistence.
That these particles can survive for so long in the comparatively wet conditions of the UK and northern US suggest that particles in the arid conditions of Iraq may be even more long-lived.
30mm DU penetrator exhibiting yellow oxide ‘rust’.
Meanwhile a second study, this time of fragments of DU, has again highlighted the significant gaps in our ability to predict the future behaviour of solid contamination. During test-firing at Kircudbright, intact or partially intact DU rounds have ended up in the sea but also on the range due to firing malfunctions. It was therefore felt necessary to study the behaviour of DU in soils and the marine environment. The results showed that DU corrosion is highly complex:
“The experiments highlight that the corrosion of DU is controlled in the environment by a number of factors that are not fully understood. It is therefore difﬁcult to undertake laboratory experiments to truly replicate the conditions in real corrosion environments.”
While the researchers were more confident about predicting the behaviour of DU in the marine environment, where chemical conditions are less variable, predicting the behaviour of DU in soils was shown to be far more difficult.
The findings support ICBUW’s view that attempts by the UK and US government to downplay concerns based on the findings from a limited number of contaminated site assessments in the Balkans are not supported by the available science. ICBUW has long argued that the variability of conditions at different sites requires that each is individually assessed and the risks they may pose to civilians and the environment calculated.
Following its assessments in the Balkans, the UN Environment Programme suggested that intact or fragmentary penetrators in soils may have completely corroded in 25 years. These new studies suggest that the actual picture may be far more complicated than originally assumed.
The corrosion of depleted uranium in terrestrial and marine environments: http://www.ncbi.nlm.nih.gov/pubmed/24315120