Following the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster in 2011, the continued release of damaged nuclear fuel into the cooling water has resulted in the accumulation of long-lived radionuclides in the contaminated water (Song, 2018). This cooling water is a mixture of groundwater, seawater, and is recirculated in tanks to remove decay heat before being filtered and stored away in tanks (Tsoi, 2023), thereby increasing the concentration of radionuclides over time. As of 2021, more than 1.25 million tonnes of seawater has been pumped through the damaged units (Nogrady, 2021).

However, with groundwater leaking into these tanks has resulted in increasing volumes of wastewater to be stored on site, along with higher incidences of contaminated wastewater leaking into the environment (Uchida et al., 2017) (Figure 2).

Fig. 1: Introduction and accumulation of radionuclides into cooling water used to cool down FDNPP reactors (Source: Song, 2018)

Figure 2: Recirculation system of cooling water at its present stage along with a demonstration of groundwater infiltration and leakage of contaminated water into the environment (Source: Uchida et al., 2017)

In particular, radioactive caesium isotopes 134Cs and 137Cs—with half-lives of 30 years and 2.1 years respectively—make up the greatest proportion of radioactivity in this cooling water (Lehto et al., 2018). To mitigate the release of these radionuclides, the contaminated water is processed through caesium absorbing equipment to remove caesium and strontium (Agency for Natural Resources and Energy, 2020). Thereafter, the wastewater is further purified through the Advanced Liquid Processing System (ALPS) to remove the remaining radioisotopes, with the exception of tritium (Yamanishi et al., 2019). As tritium cannot be removed from the wastewater via ‘conventional’ chemical methods (Shozugawa et al., 2016, as cited in Querfeld et al., 2019), this has raised concerns about tritium leakages into the environment. 

As briefly mentioned in a previous blog post, the Japanese government has announced the decision to release more than a million tonnes of treated wastewater from the FDNPP starting this year. While the bulk of radionuclides have been treated and removed, the wastewater still contains radioactive tritium (Querfeld et al., 2019).  Simulation model results created by Zhao et al (2021) have shown that regardless of the discharge amount into open sea, the radioactive tritium plume is expected to be dispersed across the entire North Pacific Ocean in any case. Similar to the caesium, tritium can become bound to animal and plant tissue, accumulating in marine organisms and across food chains, resulting in human exposure to tritium (Normile, 2023).

As expected, the decision to release this wastewater has been met with significant opposition and backlash. Notably, Japan’s geographical neighbours such as China, Taiwan, and South Korea have openly protested against it, drawing voices of opposition from politicians, fishermen, and environmental activists (Shin, 2021).

References

Fukushima Daiichi Nuclear Power Station Contaminated water management What is “slurry”? Why is it generated? How is it stored? (2020, June 19). Agency for Natural Resources and Energy,METI. https://www.enecho.meti.go.jp/en/category/special/article/detail_157.html

Lehto, J., Koivula, R., Leinonen, H., Tusa, E., & Harjula, R. (2019). Removal of Radionuclides from Fukushima Daiichi Waste Effluents. Separation & Purification Reviews, 48(2), 122–142. https://doi.org/10.1080/15422119.2018.1549567

Nogrady, B. (2021). Scientists OK plan to release one million tonnes of waste water from Fukushima. Nature. https://doi.org/10.1038/d41586-021-01225-2

Normile, D. (2023). Fukushima wastewater release set to start soon. Science, 379(6630), 321–321. https://doi.org/10.1126/science.adg8346

Querfeld, R., Pasi, A.-E., Shozugawa, K., Vockenhuber, C., Synal, H.-A., Steier, P., & Steinhauser, G. (2019). Radionuclides in surface waters around the damaged Fukushima Daiichi NPP one month after the accident: Evidence of significant tritium release into the environment. Science of The Total Environment, 689, 451–456. https://doi.org/10.1016/j.scitotenv.2019.06.362

Reuters, & Shin, H. (2021, April 14). S.Korea aims to fight Japan’s Fukushima decision at world tribunal. Reuters. https://www.reuters.com/world/asia-pacific/skoreas-moon-seeks-international-litigation-over-japans-fukushima-water-decision-2021-04-14/

Song, J. H. (2018). An assessment on the environmental contamination caused by the Fukushima accident. Journal of Environmental Management, 206, 846–852. https://doi.org/10.1016/j.jenvman.2017.11.068