[2I06-09] Waste Management 2

[2I07] Particulate plutonium released from the Fukushima Daiichi meltdowns

*Satoshi Utsunomiya¹, Shinya Yamsaki², Kenji Horie³, Mami Takehara³, Toshihiko Ohnuki⁴, Gareth Law⁵, Bernd Grambow⁶, Rodney C. Ewing⁷ (1. Kyushu University, 2. University of Tsukuba, 3. National Institute of Polar Research, 4. Tokyo Institute of Technology, 5. University of Helsinki, 6. University of Nantes, 7. Stanford University)

Keywords:Fukushima Daiichi Nuclear Power Plant, Cesium-rich microparticles (CsMPs), Plutonium, Fuel debris, Synchrotron-radiation X-ray analysis, Isotope analysis

We report, for the first time, the discovery of particulate Pu associated with cesium-rich microparticles (CsMPs) that formed in and were released from the reactors during the FDNPP meltdowns. The Cs-pollucite-based CsMP contained discrete U(IV)O₂ nanoparticles, < ~10 nm, one of which is enriched in Pu adjacent to fragments of Zr-cladding. The isotope ratios, ²³⁵U/²³⁸U, ²⁴⁰Pu/²³⁹Pu, and ²⁴²Pu/²³⁹Pu, of the CsMPs were determined to be ~0.0193, ~0.347, and ~0.065, respectively, which are consistent with the calculated isotopic ratios of irradiated-fuel fragments. Thus, considering the regional distribution of CsMPs, the long-distance dispersion of Pu from FNDPP is attributed to the transport by CsMPs that have incorporated nanoscale fuel fragments.