Blank: non-radioactive sample, Traditional method: ¹⁴C separated from ALPS-treated water using the traditional method (the counts on the low-energy side increased due to insufficient separation of ³H, and the peak exceeded the graph range), Developed method: ¹⁴C separated from ALPS-treated water using the developed method, in which traps for ³H and ¹²⁹I were added to the traditional method, ¹⁴C standard solution: sample prepared from a ¹⁴C standard solution.

The ocean release of ALPS-treated water from the Fukushima Daiichi Nuclear Power Station has attracted significant attention internationally as well as domestically regarding its safety. The Nuclear Regulation Authority (NRA) must conduct independent monitoring to ensure the objectivity and transparency of nuclide concentration analyses. The Nuclear Safety Research Center, a technical support organization for the NRA, analyzed the radioactive nuclides (13 nuclides) contained in the ALPS-treated water that was collected in March 2022 prior to the start of the water discharge. As a result, it was confirmed that the concentrations of the analyzed nuclides, excluding ³H, were lower than the safety criteria. In addition, analytical values reported by Tokyo Electric Power Company were validated using statistical methods. Independent monitoring has continued once a year.

The Fig. 1 shows liquid scintillation spectrum for ¹⁴C separated from ALPS-treated water. Because the separation of ³H and ¹²⁹I were insufficient, traps for them were added to the traditional method to analyze ¹⁴C contained in solid radioactive waste^*. As a result, ¹⁴C was selectively separated, yielding a high-quality analytical result.

 

^* Kameo, Y. et al., Simple and Rapid Determination Methods for Low-Level Radioactive Wastes Generated from Nuclear Research Facilities (Guidelines for Determination of Radioactive Waste Samples), JAEA-Technology 2009-051, 2009, 81p. (in Japanese).

This study is part of the results under contract research, supported by NRA Japan "Investigation Concerning Radionuclide Migration Within the TEPCO's Fukushima Daiichi Nuclear Power Station Plant (Fiscal Year 2022)."

Shimada, A. et al., Analysis and Quantification of Tritium and Other Low-Level Radionuclides Present in ALPS-Treated Water, Analytical Sciences, vol.41, issue 8, 2025, p.1383–1391.

Paper URL: https://doi.org/10.1007/s44211-025-00803-y

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