(488al) Tritium Effects On Electrically Conducting Polymers for Sensor Applications

The objective of this research is to design and fabricate a sensing and surveillance device for use in the tritium facility at Savannah River National Laboratory. This will be accomplished by characterizing the changes in conductivity of electrically conducting polymeric materials with exposure to tritium gas for varying lengths of time to asses the feasibility of using such materials for remote sensing. It is also desired to know the behavior of these materials when exposed to other types of radiation, such as gamma, and how the mechanism of conductivity degradation compares to that of conductive polymers in tritium. Two types of commercial grade conductive polymer, including emeraldine base polyaniline (PANi) and poly(3,4-ethylenedioxythiophene) (PEDOT), were chosen for initial proof-of-principle tests, and were drawn-down as a thin film onto a polyester substrate. The change of surface resistance (conductivity) of PANi and PEDOT films when exposed to gamma radiation in both air and deuterium environments was evaluated and tritium exposures in 1 atm and 0.1 atm gas have also been completed. Raman spectra of gamma irradiated samples were obtained to determine the exact mechanism of degradation in both polymer systems. Post-irradiation gas analysis of the samples contained in deuterium revealed very little (<20 ppm) hydrogen in the containment vessel, indicating that hydrogen-deuterium exchange was not responsible for the decrease in surface conductivity due to gamma exposure. Through this work, it is hypothesized that chain scission through free radical formation and chain cross-linking are the two dominant mechanisms for conductivity change. It has also been concluded that these test materials are sensitive to even small time periods of tritium exposure, which make them good candidates for sensor development.