The present report summarises the main results and learnings from the third phase of the NEA Behaviour of Iodine Project (BIP-3), which was conducted between 2016 and 2019 by the Canadian Nuclear Laboratories (CNL).
An NEA state-of-the-art report on iodine chemistry published in February 2007 concluded that there were still several aspects of iodine behaviour in containment during severe accidents that warranted further investigation. Over the past 25 years, there have been several NEA initiatives and other programmes to enhance the understanding of iodine chemistry, including the Phébus FP and International Source Term Project, the NEA Thermal-hydraulics Hydrogen Aerosol Iodine (THAI) Projects, the NEA Source Term Evaluation and Mitigation (STEM) Projects and the NEA Behaviour of Iodine Projects (BIP).
BIP was created to investigate the interactions between iodine and paint. The adsorption of iodine onto epoxy paint and the subsequent radiolytic production and release of organic iodides from painted containment surfaces were topics of particular interest. A database of iodine deposition data was accumulated in BIP-1 and expanded in BIP-2, with experiments focused on improving mechanistic understanding of the nature of the iodine-paint interactions.
A third phase of BIP was initiated by the NEA in 2016, with Canadian Nuclear Laboratories (CNL)1 as the operating agent. Topics for BIP-3 were chosen to leverage the CNL’s existing facilities and expertise. The BIP-3 experimental programme was structured to address important and unresolved topics from the BIP-1 and BIP-2 programmes as well as knowledge gaps that arise when attempting to extrapolate results to postulated nuclear accident conditions. Additionally, collaborative analytical activities, co-ordinated through the BIP-3 Analytical Working Group (AWG), were completed as part of the NEA BIP-3 scope of work.