Source: ORNL | Katie Elyce Jones | May 15, 2015
Each year, hundreds of researchers use the High Flux Isotope Reactor (HFIR), a Department of Energy (DOE) Office of Science User Facility at Oak Ridge National Laboratory (ORNL), to study the fundamental properties of materials important to chemistry, engineering, biology, and physics. However, one recent user stands out from the usual queue of university academics, industry R&D staff, and DOE scientists.
Cameron Roberts, 16, is a junior at the Central Virginia Governor’s School, which brings together qualifying students for research-intensive science and technology classes. In a research class led by Michele Coghill, Cameron developed a materials science project that would eventually lead him to ORNL.
“The juniors in the research class are learning skills that I didn’t even learn until graduate school,” said Coghill. “We teach the students how to develop a research project, but the projects are self-driven. Cameron came up with the idea.”
Inspired by an interest in spacecraft, Cameron decided to take a targeted look at a big problem for extended spaceflight: radiation exposure. Spacecraft are built from materials meant to shield passengers and electronics from as much radiation as possible. One of these materials is the common plastic polyethylene.
The density of polyethylene affects its tensile strength, or the maximum stress a material can withstand before breaking or stretching. Because radiation can cause structural changes, or changes in the molecular bonds within polyethylene, and denser polyethylene contains more points potentially susceptible to change, Cameron wondered whether radiation also impacts tensile strength. In his final paper, he hypothesized that “lower density polyethylene would have less of a decrease in tensile strength, due to having less interactions with the radiation.”
But to test his theory, he needed to irradiate samples of polyethylene—not an easy experiment to conduct in the classroom. Through his research, he found ORNL and sent an email to Chris Bryan, HFIR irradiation services manager, who set up a conference call with Coghill and Cameron to discuss Cameron’s project.
“I contacted several facilities, and ORNL offered to help me out, so I was thankful,” said Cameron.
Bryan and HFIR team members recommended Cameron send his samples to HFIR’s Gamma Irradiation Facility (GIF). The GIF uses spent fuel elements from the HFIR reactor to irradiate samples with gamma rays. Once HFIR staff received Cameron’s samples and characterized them using a scanning electron microscope (in order to check them for quality assurance), they irradiated 24 samples—a combination of high density and low density polyethylene samples at two levels of gamma radiation, 65 and 100 kilograys—yielding six samples at each density and radiation level.
After the samples were cleared through radiological review and shown to be safe for shipment, they were returned to Cameron. He used an electromechanical testing machine to determine the tensile strength of the irradiated samples compared to a set of control samples.
“I thought I would see a greater decrease in tensile strength in the high density polyethylene and expected to see a lower decrease in lower density polyethylene,” Cameron said, “But the results were the opposite of what I was expecting all around.”
However, disproving one’s own hypothesis is an important part of the research process, and Cameron’s project paper and presentation won third in the physics and astronomy category at the Central Virginia Regional Science Fair. The paper was also accepted into the Virginia Junior Academy of Science Research Symposium to be held in May.
Impressed with the design of Cameron’s project and his initiative to contact the lab, the HFIR team has kept up with Cameron’s progress.
“There was a lot of positive response from the people who worked with Cameron,” said Geoffrey Deichert, HFIR experiment coordinator. “We asked to see his final paper, and he’s let us know what the feedback has been so far.”
Cameron is already working on another project as part of an internship he has in Virginia with Ceramic Tubular Products, a company that develops ceramic cladding products for light water reactors and other nuclear fuel elements, and he hopes to visit ORNL and HFIR sometime this summer to meet the team that irradiated his polyethylene samples and tour the lab.