Analysis of Mo Isotopes Originating from the Reactor Core of the Fukushima Daiichi Nuclear Power Station Using Extraction Chromatographic Separation and ICP-MS/MS Measurement with an Oxygen Dynamic Reaction

Oxygen dynamic reactions with Zr, Mo, and Ru were elucidated to analyze Mo isotopes originating from the reactor core of the Fukushima Daiichi Nuclear Power Station. The main products were ZrO⁺, MoO₂ ⁺, and Ru⁺, respectively. The measured Mo isotope ratio in a mixed solution containing 1 ng/mL each of Zr, Mo, and Ru, using ICP-MS/MS with a 0.30 mL/min flow rate of the oxygen reaction cell, agreed within 4% with that of the Mo solution, indicating that MoO₂ ⁺ was successfully separated from ZrO⁺ and Ru⁺. The developed method was applied to the analysis of Mo isotopes in smear samples collected in reactor buildings at the Fukushima Daiichi Nuclear Power Station following dissolution and extraction chromatographic separation. A clearly elevated Mo/¹³⁷Cs ratio was observed in the smear sample collected on the second floor of the fuel handling machine room on the operating floor in Unit 2. In contrast, the ratios for smear samples collected from other floors of the Unit 2 reactor building were comparable to those for the composition in the reactor core.