By Carley Willis, IAEA Office of Public Information and Communication

Diagnosing the age of modern groundwater (< 60 years old) using tritium is important in mapping aquifer reserves and their vulnerability to surface pollution, but only half of 78 international laboratories carrying out such work are currently meeting the required analytical testing criteria. This was the result of a recent paper, prepared by scientists at the IAEA, published last month.

The IAEA has been conducting proficiency testing in laboratories worldwide since the 1960s to provide a baseline on the state of tritium analyses. Every four years the IAEA conducts and evaluates proficiency tests for tritium. This testing is one way for laboratories worldwide to voluntarily validate their expertise in this complicated testing procedure. There are two types of testing for tritium; monitoring laboratories who work with high levels of tritium and laboratories that test very low levels for groundwater age dating purposes. The majority of laboratories working with tritium participate in these tests.

The testing of tritium for groundwater aging purposes requires precise ultra-low level measurements and has a complicated sample preparation procedure. “The analysis of low levels of tritium in environmental water is a painstaking and complicated laboratory process of concentration and decay counting that requires weeks of hard work,” said Head of the Isotope Hydrology Section at the IAEA, Leonard Wassenaar. By conducting regular proficiency testing, errors and solutions to common mistakes can be more easily identified and corrected.

The Findings

Each of the 78 participating laboratories were given seven months to complete a test provided by the IAEA. This included testing seven water samples to record the levels of tritium, including a sample without tritium. This sample was used to determine if there was contamination in the laboratory which could result in the false detection of the tritium isotope. The results were then compared to the baseline testing done by the IAEA.

Following the tests, the results were sent to the participating laboratories along with a survey of  user practices. From this survey, 19 of the laboratories reported that they found the reason for unsatisfactory performance. Of those who participated in the survey, 85 percent reported some unsatisfactory results due to incorrect instrument settings or from improperly calibrated laboratory equipment. The survey provided the participants with a framework of cause analysis, which will contribute to helping them adjust their processes for increased accuracy of measurements. It also provided the IAEA with important information regarding the laboratories that need training support.

Through laboratory proficiency testing, the IAEA assists laboratories in verifying their performance and ensuring that instruments are properly calibrated. Proficiency testing is a requirement for laboratory accreditation, as the measurement capacity of the laboratory must be proven to a certain standard. Therefore training and support is necessary for laboratories around the globe.

“I attended a two-week training held by the IAEA where lectures, in-lab exercises as well as training and practice using laboratory software took place,” said a noble gas, tritium and radiocarbon technician at the University of Ottawa in Canada, Anthony Lapp. “When you’re working with tritium, not all laboratories will process the same, so we look at how levels are monitored, how samples are being prepared and how data is analysed. Through this training we can be more confident that we all report and measure the same.”

For the first time, when the results from the proficiency testing were sent back to the laboratories, they included extensive feedback for laboratory improvements. The results included advice based on the data received, ideas to better manage and calculate the data and testing going forward as well as directions on how to improve testing in the next test in 2024.

The one who runs the Environmental Tritium Laboratory at the Nuclear Technology Development Centre in Brazil, Eliana Nonato Knupp, participated in the proficiency testing. “We are the only laboratory in the country that tests for low concentrations of tritium compatible for groundwater age dating purposes which is very important as there are a lot of companies that work with the extraction of minerals and these parameters need to be consistently and accurately measured,” she said. “Through participating in the IAEA inter-laboratory comparison, we were able to qualify our results, certify our laboratory and confirm that we can carry out this testing in accordance with global standards.”

The laboratories are encouraged to participate in the next round of tritium proficiency testing in 2024 to track improvements and further advance their testing methods. Alongside proficiency testing, the IAEA offers member states training courses in tritium testing and interpreting the data and free software for national laboratories to monitor tritium. The IAEA also builds IAEA Deputy Director General and Head of the Department of Nuclear Applications, Najat Mokhtar. “At a time when access to water is a growing concern in many parts of the world, having a full understanding of groundwater resources is of utmost importance.” 

The Science

What is tritium?

Tritium is a radiotracer of water, meaning that one of the hydrogen isotopes is radioactive and therefore able to be distinguished and tracked. Before the nuclear test ban treaty in the 1960s, tritium was released as a by-product through nuclear tests into the atmosphere and mixed into water sources around the world. It also exists naturally at low levels. By measuring the levels of tritium found in water, scientists can determine the age of the water, due to the amount of tritium- and the source of the water through comparison with locations having the same levels of the radiotracer.

By monitoring the radioactive decay the concentration of tritium and the age of the water and rate of replenishment can be determined.