SOURCE: The Guardian

DATE: December 20, 2019

SNIP: A new form of uranium has been discovered which is likely to have implications for current nuclear waste disposal plans, say scientists.

Many governments are planning to dispose of radioactive waste by burying it deep underground. However, new research has found that in such storage conditions a new chemical form of uranium can temporarily occur, while small amounts of uranium are released into solution. If uranium is in solution, it could make its way into groundwater.

The nuclear industry currently provides 20% of the UK’s power, and radioactive waste in the UK is estimated to amount to 750,000 cubic metres – enough to fill about 300 Olympic-sized swimming pools. It is currently stored in surface sites, but it could be hundreds of thousands of years before this waste ceases to be hazardous.

Governments are searching for a way to safely dispose of the waste, and an international consensus is moving towards geological nuclear waste disposal – burying it several hundred metres underground. Many countries are already building such disposal units.

“You can’t sterilise the Earth,” says Prof Samuel Shaw, a mineralogist at the University of Manchester and one of the authors of the study, led by University of Manchester’s Prof Katherine Morris and published in the journal Environmental Science and Technology.

Shaw explains that wherever you bury these disposal units, there will be a wide variety of microbes living under the ground as well. Since no man-made barrier can be expected to withstand degradation for hundreds of thousands of years, radioactive waste will be in contact with groundwater containing these microbes and the chemicals they produce.

As well as different radioactive isotopes – which describe how many neutrons the nucleus holds – uranium can have different oxidation states, which describe the number of electrons the element has when it forms a compound. Some oxidation states are more environmentally mobile than others. In the presence of sulphides, which are created by microbes underground, uranium should not be mobile, but reports have suggested small amounts of uranium are released into surrounding water – results no one has yet been able to explain.