Ph.D. candidate Emily Caffrey and NSE alumna Elizabeth Ruedig, Ph.D. attended the Modeling and Data for Radiological Impact Assessments (MODARIA) annual meeting at the International Atomic Energy Agency in Vienna, Austria.

MODARIA is a technical program of the IAEA comprised of scientists from around the globe who make up the program’s 10 working groups; Caffrey and Ruedig were the only members from the United States in working groups 4 and 8.  Once a year members of the entire program meet at IAEA headquarters to discuss their progress and challenges. Caffrey and Ruedig are both students of Dr. Kathryn Higley, school head for NSE and an internationally recognized expert in health physics and radioecology. The radioecology research group’s main thrust has been collecting data and building models of key organisms to further understanding radiation dose to wildlife.

Ruedig and Caffrey are contributors to a larger project that is aimed at better understanding the uncertainty in current standard dosimetric methodologies. These contributions are recognized as important by the international community, and their expertise has been requested on an on-going basis as a part of the MODARIA program.

“Members of the program, especially working group 8, which focuses on biota, are trying to alleviate confusion about our goals for the models,” Caffrey said. “The idea is to demonstrate that current regulations on radiation dose are effective.”

The paradigm of radiation dose regulation centers around the idea of protecting the organisms most sensitive to radiation. We assume humans are the most sensitive species by default so regulators and scientists surmise that if you’re protecting humans then you’re also protecting wildlife, Caffrey explained.

Yet gaps in the data exist where wildlife dose is concerned. Oregon State researchers have been working for years to build voxel phantom models of key species including trout, honey bees, and earthworms. These three dimensional models are made from computer tomography or CT scans and create dynamic representations of the organisms. Working with the International Commission on Radiological Protection, these models of Reference Plants and Animals are meant to be an example that can be applied for assessment of ecosystems around the globe.

Ruedig presented some of Oregon State’s research on organism modeling in Vienna, including a model of a trout and dosimetry estimates for the fish’s digestive tract based on the model. As a result the researchers secured more projects for their local group including digestive tract dosimetry for their earthworm model and a Ph.D. project for Caffrey.

“Researchers with The Australian Nuclear Science and Technology Organization (ANSTO) have been collecting data on rabbits and kangaroos in the Maralinga Region, where the British tested their nuclear weapons in the 1950s and early 1960s,” Caffrey said.

Caffrey’s work will focus on building voxel phantom models of the organisms and then calculating dose to the animals based on computer simulations.

“The data will be of particular interest to MODARIA because they really want to know if real life matches the regulatory paradigm,” she said. “Initial data from the ANSTO samples shows that Plutonium collects in the animal’s bones as opposed to their liver, which doesn’t match predictions.” (Church et al., 2003; Johansen et al., 2013)

In addition to presenting work on biota Ruedig took part in the Uranium mining working groups focusing on risk analysis and publications describing environmental impact, slated to be released in 2016.

“The IAEA is committed to helping train young people, and also believes that they bring a fresh approach to safety work,” Ruedig said, “particularly because they are not as entrenched in any one regulatory paradigm. Additionally, as a scientist my opinion is sometimes different from the others attending these meetings, as other are often tied somehow to a regulatory structure. People who can experimentally derive data, or experimentally validate a model, are in demand.”


Church, B. W., Costello, J. M., Davy, D. R., Lokan, K. H., Morris, L. J., & Vaeth, T. A. (2003). Reabilitation of Former Nuclear Test Sites at Emu and Maralinga. Canberra, Australia.

Johansen, M. P., Child, D. P., Davis, E., Doering, C., Harrison, J. J., Hotchkis, M. a C., … Wood, M. D. (2013). Plutonium in wildlife and soils at the Maralinga legacy site: persistence over decadal time scales. Journal of environmental radioactivity, 1–9. doi:10.1016/j.jenvrad.2013.10.014

Photos courtesy of Emily Caffrey