The main outcomes of the OECD Behaviour of Iodine (BIP) Project

• Moisture affects the rate of iodine adsorption on paint.
• Irradiation of iodine-loaded paint yields methyl iodide.
• The BIP project is complimentary to the EPICUR project.
• BIP results help with the interpretation of Phébus FP results.

An Organisation for Economic Co-operation and Development (OECD) status report on iodine behaviour published in February 2007 concluded that although the understanding of iodine behaviour in containment had advanced considerably over the past several decades, there were still areas where further investigation was warranted. The OECD initiated the Behaviour of Iodine Project (BIP) to investigate two of these areas:
• The interaction of iodine with painted surfaces: adsorption of iodine from the gas phase to several containment surfaces was investigated under a variety of conditions, with focus on the role of water on the adsorption of iodine onto epoxy paints. The results show that the relative humidity is very important to the deposition velocity of iodine on paint; higher humidity caused faster deposition. Adsorption parameters are a critical input for containment codes.
• The formation of organic iodide from painted surfaces: gas chromatography was used to monitor the evolution of CH3I during the irradiation of epoxy coupons pre-loaded with iodine. The results showed that organic iodide formation is greater, and has a different temporal behaviour, when the iodine is absorbed by the paint from the aqueous phase as opposed to from the gas phase. The results also highlighted the importance of destruction of organic iodides by gas phase radiolysis to the concentration of CH3I.The BIP organic iodide production experiments were different, but complementary, to the experiments performed in the EPICUR (Experimental Program for Iodine Chemistry Under Radiation) facility. However, both projects share an objective of supporting the explanation of iodine behaviour in the Phébus Fission Product (FP) tests. In this paper, the main outcomes of the BIP project will be outlined, and their relevance to the Phébus FP project will be examined.In addition to the new experiments performed on adsorption of iodine onto paint, and production of organic iodides from iodine adsorbed on paint, Atomic Energy of Canada Limited (AECL) provided the results from five Radioiodine Test Facility (RTF) experiments. The RTF was an intermediate-scale test facility that operated at AECL’s Whiteshell laboratories in the 1990s. It is expected that BIP members will use this data for code development and verification.