210Po production in the European DEMO fusion reactor

The radionuclide inventory plays a central role in the safety of nuclear installations both during operation and their decommissioning. In nuclear fusion reactors using Pb-Li tritium breeding blankets, the undesired production of radiotoxic ²¹⁰Po is still an unresolved safety issue. In this work, neutron transport calculations and inventory calculations are combined to predict the ²¹⁰Po inventory in a DEMO fusion reactor using either a Helium Cooled Lithium Lead or a Water Cooled Lithium Lead breeding blanket. In order to guarantee that the environmental ²¹⁰Po release associated with an ex-vessel leak-of-PbLi accident remains below the no-evacuation limit, the ²¹⁰Po concentration in the Pb-Li should be kept below 1500 appt. It was found that no Pb-Li purification is required to keep the ²¹⁰Po concentration in DEMO below this limit. However, in case the Pb-Li makes direct contact with water, more volatile Po-containing (oxy-)hydroxides could form. If these species increase the ²¹⁰Po release rate by more than a factor two, safety measures will be required. Therefore, ²¹⁰Po generation in DEMO does not pose a hazard in case of a regular ex-vessel leak-of-PbLi accident, unless possibly in case the Pb-Li makes contact with water.