Spatial variations of tritium concentrations in groundwater collected in the southern coastal region of Fukushima, Japan, after the nuclear accident

Abstract

Spatial variations in tritium concentrations in groundwater were identified in the southern part of the coastal region in Fukushima Prefecture, Japan. Higher tritium concentrations were measured at wells near the Fukushima Daiichi Nuclear Power Station (F1NPS). Mean tritium concentrations in precipitation in the 5 weeks after the F1NPS accident were estimated to be 433 and 139 TU at a distance of 25 and 50 km, respectively, from the F1NPS. The elevations of tritium concentrations in groundwater were calculated using a simple mixing model of the precipitation and groundwater. By assuming that these precipitation was mixed into groundwater with a background tritium concentration in a hypothetical well, concentrations of 13 and 7 TU at distances of 25 and 50 km from the F1NPS, respectively, were obtained. The calculated concentrations are consistent with those measured at the studied wells. Therefore, the spatial variation in tritium concentrations in groundwater was probably caused by precipitation with high tritium concentrations as a result of the F1NPS accident. However, the highest estimated tritium concentrations in precipitation for the study site were much lower than the WHO limits for drinking water, and the concentrations decreased to almost background level at the wells by mixing with groundwater.

Radionuclides in surface waters around the damaged Fukushima Daiichi NPP one month after the accident: Evidence of significant tritium release into the environment

“…Environmental presence of tritium is often quantified in "tritium units" (TU), which is defined as 1 tritium atom per 10 18 hydrogen atoms ( 3 H/ 1 H = 10 -18 ) or an 3 H activity concentration of 0.118 Bq•L -1 . Reports on tritium in the environment after the Fukushima accident are relatively scarce (Kaizer et al, 2018;Kakiuchi et al, 2012;Kanda et al, 2015;Kashiwaya et al, 2017;Kumamoto et al, 2015;Maruoka et al, 2017;Matsumoto et al, 2013;Povinec et al, 2017;Tanaka et al, 2014). Precipitation samples collected in Tsukuba, Japan, in 2010 (before the accident) exhibited a tritium level of 2 TU (Matsumoto et al, 2013).…”

“…However, Matsumoto et al (2013) take into consideration fluctuations and seasonal variations and thus consider 6 TU as a conservative pre-accident background value for tritium. So far, the highest estimated environmental concentration of tritium after the Fukushima accident were 1342 TU and 433 TU (in rainwater collected 25 km from FDNPP 10 days and 5 weeks after the accident) (Kashiwaya et al, 2017) and 160 TU (in rainwater collected 170 km from FDNPP 10 days after the accident) (Matsumoto et al, 2013), respectively.…”

“…The tritium level in this puddle water is the highest ever reported in scientific literature after the Fukushima nuclear accident. Kashiwaya et al (2017) estimated a tritium concentration in precipitation of 1342 TU at a distance of 25 km 10 days after the accident. Our sample #5Pud comes from a much closer location (1.5 km from FDNPP) but was taken 30 days after the accident.…”

Evidence for tritium persistence as organically bound forms in river sediments since the past nuclear weapon tests

“…In addition to nuclear testing that affected natural contents of tritium at the global scale, human activities are also responsible for tritium emission in the atmosphere and in rivers at regional and/or local scales all around the world. In the southern part of the coastal region of Fukushima prefecture (Japan), HTO concentrations measured in wells near the damaged Fukushima-Daiichi nuclear power plant (FDNPP) and in rainwater were significantly increased during several weeks after the accident 19–22 and huge volumes of tritiated water produced by the damaged FDNPP are still stored in containers close to the power plant. Tritium is also the main artificial radionuclide currently released in waters by nuclear power plants around the world and the expected evolution of nuclear civil technology (e.g.…”

Landside tritium leakage over through years from Fukushima Dai-ichi nuclear plant and relationship between countermeasures and contaminated water

“…Investigation of 3 H in precipitation may be one of the easiest ways to confirm the release of 3 H into the atmosphere. The highest tritium concentration in precipitation was estimated 10 days after the accident at 1342 TU (equivalent to 158 Bq/L) 13 . A surface water concentration of 3 H at 184 (± 2) Bq/L was detected in rice paddy fields at 1.5 km from the FDNPP plant 12 .…”