Investigations on the source term of the detection of radionuclides in North of Europe in June 2020

Abstract

During the second half of June 2020, small quantities of artificial radionuclides (60Co, 134Cs, 137Cs, 103Ru, 106Ru, 141Ce, 95Nb, 95Zr) have been detected in northern Europe (Finland, Sweden, Estonia), the source of the release being unknown. The measured values were close to detection limits and didn’t represent any health issue. This paper presents the investigations carried out at IRSN in order to identify the release origin. The most probable source location and the release magnitude estimation are briefly presented. This recent set of detection is also compared to previous similar ones. This paper mainly focuses on the investigations which have been performed in order to answer two main questions. First “from which type and part of a nuclear installation the release could come from?”. Although no certainty is achievable, the most probable source is found to be a spent primary ion exchange resin. The second question addressed was “how this radiological inventory could have been released into the atmosphere?”. But, mainly due to the lack of information, no satisfying answer has been found to that question and what really happened remains unknown.