Quantitative Analysis of Zirconium Alloys Using Borate Fusion and Wavelength Dispersive X-ray Fluorescence Spectrometry

The National Institute of Standards and Technology uses borate fusion, wavelength dispersive X-ray fluorescence (WDXRF) spectrometry and synthetic calibration standards for high performance, quantitative analyses of alloys reacted and partially dissolved for fusion into borate beads. Conversion from metal matrix to low Z glass preserves measurement sensitivity. Synthetic calibration standards closely match fused samples, yielding very low uncertainties in results. This approach was applied to zirconium alloys of >= 90% Zr and 17 elements: Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, P, Pb, Sn, Ta, Ti, V, and W. To demonstrate capabilities, it was applied to Standard Reference Material (SRM) 360b Zirconium (Sn-Fe-Cr) Alloy, renewal SRM 360c, plus discontinued Zr alloy SRMs: 360, 360a, 1210 through 1215, and 1234 through 1239. Eleven elements exhibit biases <= 5% for these SRMs. Additional validation used comparative test methods of inductively coupled plasma (ICP) mass spectrometry, ICP optical emission spectrometry and prompt gamma-ray activation analysis. This WDXRF method gives results of high enough quality to certify the valid elements in conjunction with results from one or more independent methods. Several phenomena complicate the approach. Normal Zr dissolution using HNO3 + HF, forms Zr(NO3)(4) in solution and concentrates it on drying. Zr(NO3)(4) sublimes at low temperatures, causing uncontrolled loss of Zr as the temperature exceeds 100 degrees C. Rapidly heated Zr(NO3)(4) may explode. Digestion with HF alone works well. High-purity ZrO2 and LiF were used for matrix matching of calibration standards, requiring determinations of trace elements in the high-purity ZrO2.