Assessment of Dose Rates to Non-human Biota of Terrestrial Environment around Kaiga Generating Station, Kaiga

Abstract

In this study, the radiological impact of naturally occurring radionuclides (²³⁸U and ²³²Th) and fallout radionuclide (¹³⁷Cs) in the soil around the Kaiga Generating Station (KGS), Kaiga, on the terrestrial non-human biota was investigated. Through the analysis of 113 soil samples collected from 2015 to 2021, the study determined mean activity concentrations of 2.9 ± 1.4, 19.6 ± 5.2, and 24.1 ± 4.3 Bq kg⁻¹ d.w. for ¹³⁷Cs, ²³⁸U, and ²³²Th, respectively, in surface soil samples. Utilizing the ERICA assessment tool (v2.0) and employing the Tier-2 approach, the study estimated radiological doses to reference organisms in the terrestrial ecosystem around Kaiga. Lichens and bryophytes exhibited the highest activity concentrations for ¹³⁷Cs, ²³⁸U, and ²³²Th, while annelids showed the lowest activity for ¹³⁷Cs, and for ²³⁸U and ²³²Th, amphibians exhibited the minimum activity. The total dose rates (internal + external) ranged from 1.9E−03 to 6.7E−01 µGy h⁻¹. Despite the highest dose rate of 6.7E−01 µGy h⁻¹ observed in lichen and bryophytes, all assessed dose rates remained below the ERICA screening level of 10 µGy h⁻¹. Risk quotient values for all reference organisms were less than 1 (RQ < 1), indicating negligible risk to non-human biota.