The work of informing guidelines for nuclear workforce safety has come a long way since the national labs first began research into radiation exposure in the aftermath of World War II. Today, that legacy of health physics research at the Department of Energy's Oak Ridge National Laboratory is informing Caleigh Samuels' work as she leverages AI to modernize computational models that provide decision-makers with high-quality technical data for nuclear safety.
Samuels is radiation dosimetry lead at ORNL's Center for Radiation Protection Knowledge (CRPK) in the Environmental Sciences Division. The center was founded 15 years ago to consolidate and disseminate technical information. Today, the center provides seven federal agencies with findings regarding radiation dosimetry - the study of how radiation enters, moves through, is retained by, and exits the body.
The CRPK is a source of unified technical background information to support decision-making by U.S. agencies including DOE, the Nuclear Regulatory Commission and the Federal Drug Administration (FDA). The research is relevant to anyone working around radiation sources, ranging from scientists developing new nuclear fuels, to nuclear power plant workers, to medical technicians delivering life-saving radiotherapies and the patients who receive them.
Samuels specializes in the development of biokinetic models - intricate mathematical representations of the movement of radioactive substances through the body over time. She uses Monte Carlo algorithms to resolve complex physical processes, such as dose assessments, to better understand exposure risk. Such algorithms calculate a multitude of "what-if" scenarios in complex problems to arrive at the most probable outcome.
"Our biokinetic models quantify how substances move from one compartment in the body to another," Samuels said. "The compartments can be a complete organ system or specific parts of organs."
Improved safety standards for nuclear energy progress
As part of its mission, the CRPK assesses impacts of the latest data and models to advance radiation safety values and standards. For instance, earlier this year Samuels and ORNL colleague Rich Leggett issued a report reflecting new methodologies in regards to external exposure to radionuclides in air, water and soil . Samuels and colleagues also published a landmark age- and sex-specific biokinetic model for radon exposure in 2023, and their work is improving dose estimates for brain tissue that can improve radiation worker safety and support medical research to better understand Alzheimer's, Parkinson's and similar disorders.
"The CRPK's efforts ensure that workers are safe in all their activities," Samuels said. "Our research at ORNL provides quality data to enable reasonable exposure limits that can guide decision-making. The work can help regulators avoid wasted time and funding on measures or sources relatively inconsequential to health and safety. Our statistical analysis can fuel progress in the development of innovations such as new nuclear fuels, advanced reactors and radiopharmaceuticals."
ORNL's data inform both U.S. and international recommendations for radiation protection, including at the International Atomic Energy Agency. Samuels is a member of task groups for both the U.S. National Council on Radiation Protection and Measurements and the International Commission on Radiological Protection.
Her work also spans the Million Person Study (MPS), a multi-institutional project backed by government, academia and industry to better analyze and understand the health effects of low-level radiation exposure across a broad group of workers. The project focuses on occupations ranging from DOE Manhattan Project Site workers to nuclear power plant staff to nuclear submariners, X-ray technicians, radium dial workers and astronauts exposed to cosmic radiation. For MPS, Samuels has helped refine historical data and apply machine learning to better understand dose response relationships.
On the path to an interdisciplinary, impactful career
Samuels grew up in a family of scientists. Her father was a seafood expert at the FDA, and her mother studied chemistry with a concentration on food safety. Samuels' brother is an aerospace engineer for NASA, and her sister works in science outreach in Oregon. "There wasn't a chance I wouldn't be a scientist," Samuels said.
She attended college at Radford University, earning a bachelor's degree in physics. While there, her interest in research was piqued by participating in the Arctic Geophysics program where students designed, executed, processed and analyzed data from experiments. She led a team conducting measurements for the City of Utqiaġvik, Alaska, and briefed city officials.
When it was time to decide on graduate school, Samuels had a choice to make: What would be her focus? "The thing I kept returning to is that I wanted to do something that hopefully makes the world better. I also felt the pull of several science areas - biology, chemistry and nuclear physics. So, what I settled on is a field in which I get to explore all these different areas in the pursuit of science that is both helpful and personally fulfilling," Samuels said.
She enrolled at Georgia Institute of Technology, earned a master's in medical physics and then a doctorate in nuclear engineering. As part of her doctoral program, Samuels worked in Georgia Tech's Office of Radiological Safety. "I like that my science can help keep everyone a little bit safer," she said.
'No one way to be a scientist': Mentoring the next generation
Samuels was hired as ORNL staff in 2019. "I came to ORNL because of the work of Rich Leggett and Keith Eckerman - two pioneers in the field of radiation dosimetry," Samuels said. "When we were discussing the move, I emphasized to my husband that it was the opportunity of a lifetime."
What's ahead for Samuels and the remaining challenges in her field?
"I'm very interested in expanding biokinetic models to include sex-specificity and evaluating associated impacts on radiological risk for females," she said. "Estimated health impacts from exposures are typically greater for females; however, these estimates often apply doses calculated with biokinetic models based primarily on male data."
Accumulation in female organs can differ from male organs due to anatomical factors (such as the volume of organs), she noted. There's also the consideration that elements are processed differently in females than in males.
"Iron uptake and needs are higher in female bodies, for instance," Samuels said. "Bone remodeling processes change rapidly once females hit menopause, meaning their dose limits for bone-accumulating radionuclides like strontium or radium likely need to change as well. We're working on this now, modeling how bones and other internal structures can be affected as females age. We can then take that information and make progress in our models for older males as well."
Her advice for young scientists?
"I'm always hesitant to give out pat statements. I find the advice you give to one person is not necessarily the advice you'd give another," Samuels said. In mentoring, "you need to consider each person for who they are and what they bring. There is no one way to be a scientist."
UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, visit energy.gov/science . - Stephanie Seay
