Baseline tritium measurements in Thailand's water bodies: Supporting sustainable nuclear energy development

Tritium, a radioactive isotope produced naturally through cosmic radiation interactions and anthropogenically through nuclear weapons testing, poses potential environmental risks, particularly within the water cycle. This study measured tritium concentrations in surface water across Thailand to establish a baseline dataset for monitoring potential contamination from nuclear activities and accidents. Surface water samples were collected from 14 large reservoirs during the wet season in October 2023 and the dry season in February 2024, providing a total of 28 samples. Tritium concentrations were analyzed using electrolytic enrichment and liquid scintillation counting techniques. The results, presented with combined uncertainty, revealed tritium levels ranging from 1.21 ± 0.19 to 2.74 ± 0.23 TU (0.14 ± 0.02 to 0.32 ± 0.03 Bq·L^-1), with an average of 1.94 ± 0.01 TU (0.23 ± 0.00 Bq·L^-1). The highest concentrations were observed in the north (2.26 ± 0.02 TU), followed by the northeast (2.13 ± 0.04 TU), central (1.91 ± 0.05 TU), east (1.72 ± 0.03 TU), and south (1.55 ± 0.04 TU). All measured tritium levels were below the natural background threshold of 10 TU and complied with the surface water quality standards set by the Thailand's Pollution Control Department. Tritium concentrations were positively correlated with latitude, distance from the coast, and elevation, while showing an inverse relationship with pH. No significant seasonal variations or correlations were observed with ion concentrations, water temperature, electrical conductivity, salinity, dissolved oxygen, or total dissolved solids. These baseline measurements are essential for supporting sustainable nuclear energy development and ensuring effective monitoring of environmental radioactivity. The dataset provides a critical reference for Thailand's regulatory agencies, such as the Office of Atoms for Peace, to safeguard public and environmental safety under both normal operations and potential radiological emergency scenarios.