Simultaneous determination of trace amounts of borate, chloride and fluoride in nuclear fuels employing ion chromatography (IC) after their extraction by pyrohydrolysis

An accurate and sensitive method based on the combination of pyrohydrolysis-ion chromatography (PH-IC) is proposed for the simultaneous separation and determination of boron as borate, chloride and fluoride in nuclear fuels such as U3O8, (Pu,U)C and Pu-alloys. The determination is based on the initial pyrohydrolytic extraction of B, Cl and F from the samples as boric acid, HCl and HF, respectively, which are subsequently separated by ion chromatography (IC). The proposed method significantly improves the existing analytical methodology as it combines the determination of boron, a critical trace constituent in nuclear materials, along with F− and Cl− for chemical quality control measurements. Various experimental parameters were optimized to achieve maximum recoveries of the analytes during the pyrohydrolysis and to get better ion chromatographic (IC) separation of borate, F− and Cl− along with other anions such as CH3COO−, NO2−, NO3−, Br−, PO43− and SO42−. Recoveries of more than 93% could be obtained for all the analytes in the sample (0.5–1.5 g) at 1200 ± 25 K and distilled with pre-heated steam at the flow rate of 0.3 mL/min. An isocratic elution with a mobile phase of 0.56 M d-mannitol in 6.5 mM NaHCO3 was used for the IC separation. The detection limits for B (as borate), F− and Cl− were 24, 13 and 25 μg L−1, respectively. Precision of about 5% was achieved for determination of boron, Cl− and F− in the samples containing 1–5 ppmw of boron, and 10–25 ppmw of Cl and F. The method was validated with reference materials and successfully applied to the nuclear fuels. The methodology is easy to adapt on routine basis.