Quantifying the accurate content of 107Pd in a radioactive effluent using the isotope dilution technique and multi-collector ICP-MS

Abstract

The radionuclide ¹⁰⁷Pd is a long-lived fission product that decays to ¹⁰⁷Ag by β⁻ emission. The accurate quantification of the ¹⁰⁷Pd content in nuclear waste is essential in compliance with international regulations on the long-term storage of radioactive waste. Moreover, fission-produced Pd holds an economic interest through its recycling for industrial purposes. The accurate quantification of ¹⁰⁷Pd is presently problematic due to the absence of a commercial reference material certified for ¹⁰⁷Pd content, and because of the scarcity of ¹⁰⁷Pd-concentrated materials. In this study, we accurately characterize a purified radioactive effluent for its ¹⁰⁷Pd content using multicollector (MC)-ICP-MS and the isotope dilution technique. The developed isotope-dilution method is based on the preparation and calibration of a ¹⁰⁸Pd-enriched commercial spike solution. The repeatability of Pd isotope ratios in the radioactive effluent as obtained by MC-ICP-MS was on the order of 0.05 % (2*standard deviation of n = 15 measurements). The ¹⁰⁷Pd content in the radioactive effluent was accurately quantified with an expanded uncertainty of 0.7 % at k = 2. The results obtained from the radioactive effluent are metrologically traceable to the International System of Units (SI). Lastly, the sources of uncertainty and their relative contribution on the final expanded uncertainty were determined and evaluated.