Research at Dounreay could result in savings in decommissioning costs
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Dounreay was involved in ground-breaking research which could lead to savings in decommissioning of nuclear sites. The research was carried out by a team from Lancaster University – led by Professor Malcolm Joyce – and involved recording previously unmeasurable minute traces of plutonium in the soil to determine if it came from local or global sources.
Soil samples from Dounreay, as well as an area near to the site and two areas at a distance from it, were used as part of the work undertaken by the team which also included Dr Jeremy Andrew from Dounreay and others from ETH Zurich, a public research university in Switzerland.
Using accelerator mass spectrometry – one of the most sensitive ways to measure plutonium – the researchers showed it is possible to identify whether or not traces of the radioactive element come from plutonium ‘bred’ in a reactor or from global fallout.
By identifying the isotopic ‘fingerprint’ of trace-level quantities of plutonium in the soil which matched the isotopic fingerprint of the plutonium created by a nuclear reactor, the research team was able to estimate levels of plutonium in the soil which were attributable to reactor pollution and distinguish them from plutonium from global sources.
The results, it was stated, could help future ‘clean up’ operations at Dounreay and other Nuclear Decommissioning Authority sites, as well as on contaminated land around nuclear power plants, saving time and money. Areas of local pollution could be "specifically identified, targeted and then assessed for clean-up if required."
Dr Andrew said there were samples which showed global source and some that showed local source but all were at trace level and consistent with levels at sites far away from Dounreay. "This research demonstrates the benefits of close collaboration between nuclear decommissioning sites and academia," he added.
Dounreay managing director Mark Rouse described the research as "great work" when he gave a report at the most recent virtual meeting of the Dounreay Stakeholder Group.
Tor Justad, the chairman of Highlands Against Nuclear Transport, asked if the study was undertaken due to concern about the plutonium and where it was coming from.
Mr Rouse replied: "We are not worried about it but it was an opportunity to see if the origin of the minute traces could be discovered."
Minuscule quantities of plutonium can be found in the environment as a result of reactions in naturally occurring uranium in the ground, and due to human activity. The latter can be the result of nuclear plant effluents, reactor accidents, accidents involving nuclear weapons and plutonium-powered space probes. They also occur globally from fallout from atmospheric nuclear weapon tests which took place between the 1950s and 1980.
Professor Malcolm Joyce said: "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.
"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."
