Application of Cavity Ring Down Spectroscopy in the monitoring of gases resulting from failures in nuclear fuels

Energy production is currently undergoing a period of reassessment due to the environmental and climate impacts arising from the use of fossil fuels. On the other hand, it is expected that the consumption of electricity will double every 30 years, demonstrating that just replacing the current sources will not solve the problem. In this scenario, nuclear energy emerges again as a solution for the generation of electric power, however, its feasibility depends on the implementation of adequate safety measures for the operation of the reactors. The integrity of fuel elements (FE) is crucial to ensure the safety and proper functioning of nuclear reactors. The release of gases that are fission products, such as Kr and Xe, is indicative of FE cracks. One of the techniques used to monitor gases resulting from failures in nuclear fuels is differential optical absorption spectroscopy, gas chromatography, and fluorescence spectroscopy. Cavity Ring Down Spectroscopy (CRDS) is also based on optical absorption by molecules/atoms in a gaseous or liquid sample, i.e., it measures extremely low concentrations of trace gases, and is useful for monitoring gases emitted by failures in nuclear fuels, such as parts per million (ppm) to parts per billion (ppb)5 . As shown in Figure 1 below, this technique is achieved by creating a high-precision optical cavity with length L, formed by highly reflective plano-concave mirrors (R1 and R2) that trap the incident light, thus enabling multiple reflections within the cavity. (author)