Cavity Ring-Down Spectroscopy Analysis of Radiocarbon from Nuclear Waste Materials

Radiocarbon analysis of nuclear waste produced in nuclear facilities lacks fast, in situ detection methods. Moreover, the amount of radiocarbon desorbing from graphitic waste is not well known. In this study, we demonstrate the use of mid-infrared cavity ring-down spectroscopy combined with an automatic sample processing unit as a method to examine radiocarbon concentration in three types of nuclear waste: spent ion-exchange resin, graphite, and graphite outgassing in sealed storage crates. The solid samples were gasified, which allowed analyzing the effect of heating on the radiocarbon outgassing from the samples. The presented method also enabled examination of molecular speciation of the radiocarbon in the samples. The method performed well with the graphite and gaseous samples, but the analysis of the spent ion-exchange resin did not produce repeatable results due to high N₂O concentrations. In the future, the presented method can be used in situ at nuclear facilities and expanded to a wider variety of sample materials than those presented here.