The issue of Cs-137 in firewood and biomass combustion: a review.

In large parts of Europe, the Chernobyl accident of 1986 caused fallout of Cs-137. This led to the uptake of Cs-137 in trees or other materials used for bioenergy production or as firewood for domestic purposes. This Cs-137 may concentrate in the ashes of the combustion process in such a way that the clearance level of 100 Bq per kg, defined in Directive 2013/59/Euratom (EU BSS), may consequently be exceeded.