Methods of Preventing the Spread of Zinc Contamination During Vacuum Processing

Abstract

Radioactive zinc, ⁶⁵Zn, was detected after a thermal vacuum process that extracted a desired product from articles out of a commercial light water reactor. While the facility is designed to handle radioactive materials, the location of the ⁶⁵Zn was in an area that is not designed for gamma-emitting contaminants. A series of experiments were conducted to entrain the contaminant in an easily replaceable trap within the process piping. The experiments were conducted with increasing levels of complexity. Initially, a simple apparatus was developed to determine the effect of substrate temperature on the vapor capture, which was followed by experiments to determine the effect of filter pore size on pumping and trapping, and finally the interactive effects of both pore size and temperature were evaluated. The testing was conducted on a system that used a roughing vacuum pump using model and prototypic materials. It was determined that heating the substrate to nominally 200 °C resulted in effective trapping on the model as well as prototypic material.