PNNL

The Science

Volatile radioisotopes, such as iodine-131, pose a substantial health risk if released into the environment in high concentrations. However, there are large uncertainties about the environmental fate of these radioisotopes because of the ways reactive radioisotopes can react with organisms and the environment as both gases and particles. In addition, it is difficult to track and study these changes in a laboratory because typical atmospheric chambers are too large and not robust enough to meet radiological safety standards.

A team of researchers at Pacific Northwest National Laboratory designed and constructed an atmospheric chamber that meets radiological safety regulations and an accompanying method that accounts for a smaller, less robust chamber to simulate the fate of volatile and semivolatile radioisotopes.

The Impact

This environmental chamber and its attendant methods create a safe, reliable way to characterize radioisotope reactions in the atmosphere. The studies enabled by the chamber can provide vital understanding to inform health and environmental risk mitigation in the event of a radioisotope release.

Summary

The chamber contains ports for gas injection, gas sampling, pressure and temperate monitoring, and an axis-aligned light pipe to introduce light from a 2.5-kW xenon bulb into the chamber. The lamp optics were designed to homogenize the direct light intensity out as much as possible while maintaining a sealed environment. The chamber relies on reflections of the chamber walls to further distribute the light and irradiance throughout the chamber. To overcome the smaller volume of the metal chamber, the researchers developed an optical modeling technique that can understand the distribution of the light intensity that drives much of the iodine reactions. Optical modeling provides the data necessary to evaluate the total optical radiation incident on chamber gases using models of the optical intensity inside an optical chamber at any given point. Direct measurements of optical intensity are well corroborated by optical modeling, providing validation of the optical model.

PNNL Contact

Lance Hubbard, Pacific Northwest National Laboratory, lance.hubbard@pnnl.gov

Funding

Funding for this project came from the Chemical Dynamics initiative, a laboratory directed research and development investment.