PNNL

Abstract

In the case of nuclear power plant accidents, several radionuclides are being dispersed into the environment. In particular, the release of radioiodine 131I represents a major health concern because of its absorption by the thyroid gland. To reduce the release of 131I into the environment, capture materials, such as activated carbon, provide a mean to efficiently retain radioiodine-bound molecular species. In this study we use ab initio molecular dynamic calculations to investigate the effects of 131I radioactive decay on the molecular stability of I2, acid iodine (HI, HIO, HIO2, and HIO3), and methyl-iodine species in both gas phase and adsorbed on graphite. In gas phase, we found that I2 is the least resistant to 131I transmutation, followed by the HIOx family of molecules, then HI and CH3I which are the most resistant. However, the graphite surface is found to greatly favorize the fragmentation of adsorbed molecular species. While the identification of gas phase fragments can offer new chemical route to consider in chemical kinetics models, the formation reactive fragment products at the graphite surface can favorize their reaction with surface carbon atoms which overtime could reduce the number of adsorption sites of capture materials available, and hence, impacting their capture capability.