Proficiency test for gamma-emitting radionuclides in seawater: A case study from South Korea

Following the release of Advanced Liquid Processing System (ALPS) treated water - radioactive contaminated water purified to regulatory safety limits for all radionuclides except ³H - from the Fukushima Daiichi Nuclear Power Plant, the need for reliable marine radioactivity monitoring has become critical. This study describes a proficiency test (PT) program organized by the Korea Research Institute of Standards and Science (KRISS) to assess the analytical capabilities of six domestic laboratories in determining radiocesium (¹³⁷Cs and ¹³⁴Cs) levels in seawater. A homogeneously spiked seawater sample was prepared and its reference values were established with metrological traceability. Coincidence summing correction factors were applied, and uncertainty budgets were carefully evaluated. All six laboratories reported results within ±7 % of the reference values, and their z'-scores remained within the acceptable range (|z'| ≤ 2). These outcomes confirm the competence and consistency of domestic laboratories in low-level radiocesium analysis. The findings highlight the robustness of Korea's marine radioactivity monitoring system and provide assurance of its preparedness in responding to potential environmental impacts associated with the discharge of treated radioactive water.