New IAEA Publication on Tritium in the Environment

Tritium’s role in energy systems has made understanding how it interacts with water, air, ecosystems and living things more relevant than ever. 

As the world transitions toward cleaner energy solutions, both nuclear fission and fusion energy technologies are expected to play an increasingly important role in power generation. Tritium is not only a byproduct of nuclear fission but also a critical fuel for future fusion energy systems, such as the International Thermonuclear Experimental Reactor (ITER). 

In the field of hydrology, scientists actively study tritium’s behaviour in oceans, rivers, lakes and glaciers to learn about global circulation patterns of both air and water. Being bound in water molecules, tritium moves easily through the atmosphere and aquatic and terrestrial ecosystems. In contrast, other radioactive isotopes may stick to soils or sediments, creating a contamination build-up that can cause prolonged radiation exposure to both humans and wildlife. 

“One of the main scientific interests in tritium is that it integrates with other biological molecules naturally,” said Frédérique Eyrolle, a senior researcher from the French Authority for Nuclear Safety and Radiation Protection and contributor to the IAEA publication. “This means that tritium may be transferred from organism to organism through aquatic food chains more than other radioactive isotopes.”

Because tritium is already integrated with water molecules, measuring its concentration can be a reliable way to assess water replenishment rates and groundwater age. Each year, the IAEA Isotope Hydrology Laboratory processes about 1000 water samples from around the world to determine tritium concentrations, which are often at low to ultra-low levels. 

Another distinctive trait of tritium is that it emits low-energy beta radiation, which cannot reach sensitive cells in the body, so does not pose a radiological hazard to humans or other live organisms as an external radiation source. As a result, tritium presents lower health risks than most other radioactive isotopes. This is reflected in the IAEA’s international radiation safety regulations that countries use as a guide to establishing safe industrial practices at scientific research sites.

The new IAEA publication compiles the latest knowledge on tritium, including its relevance in nuclear fission and fusion, its movement in the environment and its application in industries such as manufacturing and medicine. 

“The IAEA helps countries understand tritium in the environment by supporting research, providing data and offering guidance,” said Tzanka Kokalova Wheldon, Director of the IAEA Division of Physical and Chemical Sciences. “As tritium becomes an increasingly important tool, including as a fusion fuel, this publication brings together the latest scientific knowledge about its behaviour in the environment to help experts address research challenges as well as societal needs.”

The publication serves as a vital reference for policy makers, scientists and researchers, offering a scientific perspective on tritium’s properties, environmental significance and exploring regulatory considerations.

The IAEA Terrestrial Environmental Radiochemistry Laboratory develops validated analytical techniques and certified reference materials to ensure accurate measurements of radioactive and stable isotopes, including tritium. 

The IAEA has launched a series of technical meetings on tritium, starting with one on tritium breeding blankets and associated neutronics held in September 2025. These meetings will provide a forum for member countries to exchange information, discuss challenges and present scientific progress.