Evaluation of total-reflection X-ray fluorescence measurements for the prospective determination of uranium in the decommissioning of the Fukushima Daiichi Nuclear Power Plant reactor

Owing to the strong earthquake and subsequent tsunami in March 2011, the Fukushima Daiichi Nuclear Power Plant was exceedingly damaged and is currently under decommissioning. Herein, we propose a methodology to evaluate the uranium concentration in the drainage water from the decommissioning field. Model sample solutions were prepared by mixing multi-element standard solutions containing uranium with an immersion liquid containing demolition debris. A very small amount (10 mu L) of the sample solutions was dropped onto a quartz optical flat directory with or without a chromatography resin separation. The total-reflection X-ray fluorescence (TXRF) spectrometry measurement was performed using a portable device. These measurements showed an overlap of the Rb K alpha and U L alpha peaks in the TXRF spectrum of the sample solution prepared without chromatography resin separation. By contrast, no overlap was observed in the TXRF spectrum of the sample solution after the separation using a chromatography resin. When the drainage water is composed of 0.04% U-234, 5% U-235, and 94.96% U-238, the measurement times in both methods (i.e., with and without pretreatment) required to attain detection limits lower than the effluent standard value are 15 and 5 min, respectively. Additionally, the detection limits, analysis times, required sample volumes, and procedures of the two methods are compared.