More than a decade after the Fukushima nuclear accident, research on radioactive risk led by Tomoko Ohta of Nagaoka University of Technology has highlighted persistent chlorine-36 (^36Cl) contamination in the soil of Koriyama, 60km from the plant.
This radioactive isotope, detected at considerable distances from the accident epicenter, signals a long-lasting environmental challenge, despite the significant decline in tritium (^3H) levels.
Advanced study methodologies and in-depth results
In the study, published in Nature on November 11 (I link it here), researchers were able to detail the presence of ^36Cl in soil and groundwater through advanced techniques such as accelerator mass spectrometry.
The results show a slow process of environmental cleanup of ^36Cl, underscoring the need for continued decontamination and monitoring efforts in the long term.
A necessity that follows TEPCO's decision to release treated water from the Fukushima reactors into the sea (and which has generated global debates and concerns). Despite reassurances about safety standards and low levels of contamination detected in fish species, the issue remains a focal point in the international dialogue on nuclear energy and its environmental safety. And the authorities did well to establish controls, which seems to have given reassuring results.
Radioactive state of the soil 60km from Fukushima. The main findings of the latest study.
- Measurements and Estimates: Despite the lack of direct measurements of ^3H and ^36Cl concentrations immediately after the accident, the researchers were able to reconstruct deposition data for these isotopes through a drill hole drilled in 2014. They found very high concentrations of ^3H and ^36Cl in unsaturated soil at depths between 300 and 350 cm.
- Use of tritium as a tracer: Previous studies have used tritium released in nuclear tests as a hydrotracer in soil water and shallow groundwater. Tritium released from the damaged Fukushima reactors provided a similar opportunity to reconstruct the amount deposited around the accident epicenter..
- Release of ^36Cl: After the accident, the release of the long-lived radioactive isotope Chlorine-36 was also expected. The proportions of ^36Cl/Cl in the soil at distances of 3-22 km from the plant were much higher than natural proportions, indicating a significant release of ^36Cl into the environment..
- Total Inventory of ^3H and ^36Cl: Using sophisticated techniques, researchers quantified the total concentrations of ^3H and ^36Cl released by the accident. They found that most of the tritium had been removed from the unsaturated zone by 2016, although ^36Cl concentrations remained significantly elevated above natural levels.
- Environmental Restoration: Further investigation showed that most of the excess tritium and ^36Cl from the accident had been washed out of the soil column by 2016, but there were still elevated levels of ^36Cl in the environment even in 2021.
- Summary: In conclusion, the article reports accurate estimates of the total quantities of ^3H and ^36Cl deposited in Koriyama following the Fukushima accident. Although most tritium had disappeared from the unsaturated zone by 2016, Chlorine-36 concentrations (while not hazardous to humans) were still significantly higher than natural levels..
Nuclear power is this thing here. For better or for worse. Neither apocalypse nor panacea.
The Fukushima accident, the only one with Chernobyl to have obtained the classification of “level 7 accident” highlighted the importance of long-term management of radioactive risk. Nuclear technology is generally safe, but also brings with it non-negligible risks in the event of accidents.
The scientific community and local authorities are called to collaborate closely to ensure that the areas affected by Fukushima are made safe and livable for future generations. Because the lesson of Fukushima goes beyond the Japanese context. Without prejudice, or supporters for and against, the global community must carefully evaluate the long-term implications of the use of nuclear power, balancing the benefits with the potential risks.
We need to have a balanced perspective on the role of nuclear power in the global energy mix. Recognize both its security developments and the serious environmental consequences in the event of disasters. This really means doing a good service to the future.
