Probe of Radiolysis Behavior Reveals New Perspective
This model simulation shows the formation of H2O2 (hydrogen peroxide) under conditions relevant to the geologic disposal of spent fuel. At high H2 and low O2, little H2O2 is produced, but with only a slight change in one of these, a sudden jump in the H2O2 concentration occurs.
Recently published PNNL research into radiolysis—or radiation's ability to cause molecular decomposition in substances—demonstrated a tendency for the radiolysis system to jump unpredictably from one condition to another, and may have implications for research in other fields, including atmospheric systems.
"Our findings predict that alpha radiolysis may have some unusual properties under certain conditions," says Rick Wittman, Energy and Environment Directorate, who led an EED research team that included Edgar Buck, Edward Mausolf, Bruce McNamara, Frances Smith and Chuck Soderquist. "We found this by developing a numerical code to simulate radiolysis, and running the simulation under multiple conditions, which has not been done before."
The team found there are critical points where the system will tip to one of two completely stable states depending on miniscule changes that might not be predictable. The findings may help explain some of the anomalies that have turned up in similar experiments in this research field. Such behavior also might be present in other chemical systems, such as atmospheric processes, where comparable radical reactions occur and where there are many complex processes and interactions in play.
The results are documented in the paper, "Conditions for Critical Effects in the Mass Action Kinetics Equations for Water Radiolysis." The paper was published in late November in The Journal of Physical Chemistry, and the results also were presented at a recent Materials Research Society meeting in Boston.
The DOE Office of Nuclear Energy’s Used Fuel Disposition Program funded the work.