Radioactivity from Fukushima Dai-ichi in air over Europe; part 2: what can it tell us about the accident?

It is shown which information can be extracted from the monitoring of radionuclides emitted from the Fukushima Dai-ichi nuclear power plant and transported to Europe. In this part the focus will be on the analysis of the concentration ratios. While 131I, 134Cs and 137Cs were reported by most stations, other detected radionuclides, reported by some, are 95Nb, 129mTe, 132Te, 132I, 136Cs and 140La. From their activity ratios a mean burn-up of 26.7 GWd/t of the fuel from which they originated is estimated. Based on these data, inventories of radionuclides present at the time of the accident are calculated. The caesium activity ratios indicate emissions from the core of unit 4 which had been unloaded into the fuel storage pool prior to the accident.

► Activity ratios of Fukushima radionuclides in air are estimated. ► A mean burn-up of 26.7 GWd/t is derived from the caesium ratios. ► Fuel inventories at the time of the accident are calculated. ► Fuel in storage pool of unit 4 contributed to emissions.