Development of Chemical Procedures for Isotope Harvesting: Separation of Trace Hafnium from Tungsten

ABSTRACT

The separation of trace hafnium from bulk tungsten alloys is of interest for isotope harvesting at the National Superconducting Cyclotron Laboratory and the Facility for Rare Ion Beams because ¹⁷²Hf, the parent of ¹⁷²Lu, accumulates in tungsten alloy beam blockers at these facilities. In this work, a procedure for the separation of trace hafnium from a bulk tungsten alloy (454 g) was established using tracer isotopes (¹⁷⁵Hf, ⁸⁸Zr, ¹⁷³Lu, and ⁸⁸Y). The procedure employed dissolution in an HF–HNO₃ solution followed by a calcium fluoride precipitation, and then extraction chromatography was used for more selective separation steps. Two stages of column separations using LN resin (HDEHP based) and TRU resin (CMPO based) were performed. Gamma-ray spectroscopy and mass spectrometry were used to analyze the final hafnium sample and follow the steps in the chemical processing. The final recovery of hafnium was high (90 ± 8)%, and the mass of tungsten and other transition metals was reduced to near background levels (as determined by ICP-MS of the blank acid solutions). Zirconium follows hafnium quantitatively in this procedure; there was no detectable ¹⁷³Lu in the final hafnium sample.

KEYWORDS:

• FRIB
• isotope harvesting
• LN resin
• TRU resin
• hafnium

Acknowledgements

The authors thank Rachel Lindvall for performing the mass-spectrometry measurements as well as the CAMS facility staff at LLNL, particularly Scott Tumey, for providing beam time and expertise for the production of radionuclides used in this study. This study was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07366299.2022.2079502.