MEASUREMENT OF HAFNIUM AND ZIRCONIUM IN ZIRCONIUM ORES: OUTCOME OF A NATIONAL INTERCOMPARISON EXERCISE, ZH-A
Abstract
A case study is presented in this paper in which a Zirconium pilot plant was set up for the production of zirconium for the cladding of fuel rods. Hafnium occurs in combination with zirconium and is a neutron absorber. Therefore, its concentration has to be kept within tolerance limits and monitored throughout the production process. Five Pakistan Atomic Energy Commission (PAEC) laboratories using different techniques measured the concentrations of Zr and Hf with a wide range of results, i.e. more than three times the standard deviation. Therefore, a national intercomparison exercise, ZH-A was conducted to remove discrepancies and improve analytical procedures in the measurement of hafnium and zirconium in zirconium ores. The ZH-A series of reference samples, prepared at the Pakistan Institute of Nuclear Science and Technology (PINSTECH), were used for this purpose. It was observed that the measurement errors decrease with an increase in Hf concentration (~298 ppm to 1.75%) for all techniques used in this exercise. This was especially significant for Atomic Absorption Spectrometry (AAS). Measurement errors for Hf using AAS are also the highest. Neutron activation analysis (NAA) was found to be the most reliable of all the tested techniques for the measurement of both Hf and Zr in zirconium ores due to its high sensitivity and accuracy.References
Eurachem/ Co-operation on Traceability in Analytical Chemistry (CITAC) Guide, Guide to Quality in Analytical Chemistry, An Aid to Accreditation, CITAC/08B/01, (2001).
Eurachem/ Co-operation on Traceability in Analytical Chemistry (CITAC) Guide, Quantifying Uncertainty in Analytical Measurement, Second Edition, Editors, S.L.R. Ellison, M. Rosslein and A. Williams, (2000).
IAEA/RL/64, Report on the Intercomparison Run SL-1, Trace Elements in Lake Sediments (1992).
S. Waheed, A. Rahman, M. Daud, J.H.Zaidi and S. Ahmad, Radiochim. Acta, 92, (2004) 939.
A. Mannan, S. Waheed, I. Fatima and I.H. Qureshi, J. Radioanal. Nucl. Chem., Lett. 104, No. 5 (1986) 263.
International Organization for Standard-ization/ International Electro-technical Commission (ISO/ IEC) Guide 43-1:1997(E).
International Organization for Standard- ization/ International Electrotechnical Commission (ISO/ IEC) Guide 43-2:1997(E).
IAEA/AL/144 IAEA/MEL/72, Report on the Worldwide Intercomparison, Exercise for the Determination of Trace Elements and Methylmercury in Fish Homogenate IAEA-407, (2003).
J.C. Miller and J.N. Miller, Statistics for Analytical Chemistry, Ellis Horwood Ltd., Chicester, (1988).
T.J. Farrant, Practical Statistics for the Analytical Scientist – a Bench Guide. Royal Society of Chemistry for the Laboratory of the Government Chemists (LGC), Teddington (1997).
J.S. Fedorowich, J.P. Richards, J.C. Jain and R. Kerrich, J. Fan, Chem. Geol., 106, (1993) 229.