Chlorination mechanism of typical metallic radionuclides by HCl on irradiated graphite surface from first principles

Radioactive activity of metallic radionuclides accounts for a considerable proportion in irradiated graphite from nuclear reactors. Chlorination roasting is a promising method to remove metallic radionuclides in decommissioned irradiated graphite. The decontamination effect and chlorination mechanism of 90Sr and 60Co by HCl over an irradiated graphite surface were estimated by density functional theory. 90Sr and 60Co could be chlorinated via X(metallic radionuclide)→XCl→XCl2 reaction pathway. The rate-determining step appeared where metallic radionuclides desorbed from irradiated graphite surface. The chlorination energy barriers of 90Sr and 60Co were 236 and 575 kJ/mol, respectively, implying that chlorination roasting method for decontaminate of 90Sr and 60Co in irradiated graphite was feasible. This work is beneficial to the application of chlorination roasting for removal of metallic radionuclides in irradiated graphite.