Treating liquid radioactive waste at the Idaho National Engineering and Environmental Laboratory sends up a signature orange plume.
There is no requirement to remove the nitrogen oxides coloring the plume emitted from the main stack at the Idaho Chemical Processing Plant.
But proposed regulations would require the removal of other harmful chemicals in the fog, engineer Jim Law said. In the process, the oxides of nitrogen, and the colorful cloud, would be removed.
Under a 1995 agreement with Gov. Phil Batt, the federal government has started treating some of the remaining liquid, high-level waste stored in underground tanks by turning it into a dry, granular form.
The process releases oxides of nitrogen and the plume.
Oxides of nitrogen also cause the brown color of smog and contribute a small percentage to acid rain.
The oxide emissions have been a concern of the National Park Service because of the effect they have on long-distance views at the Craters of the Moon National Monument.