Uranium isotope dilution mass spectrometry using NBL certified reference materials as spikes A. Hasozbek • K. J. Mathew • G. Orlowicz • N. Hui • B. Srinivasan • M. Soriano • U. Narayanan Received: 18 July 2012 / Published online: 8 August 2012 Ó Akade ´miai Kiado ´, Budapest, Hungary 2012 Abstract The isotope dilution mass spectrometry method of analysis is used to determine the elemental uranium contents in a wide variety of uranium bearing materials. The method is based on the mass spectrometric analysis of a mixture prepared by diluting the sample to be analyzed with a spike of distinctly different isotopic composition to that of the sample. In this work, a beginning is made to identify suitable candidates among the multitude of certi- fied reference materials (CRMs) available at the New Brunswick Laboratory to supplant the use of 233 U which remains now as the preferred spike nuclide. The results of the study presented here identify CRM 112-A (of normal isotopic composition) and CRM 115 (depleted uranium composition) as suitable candidates to replace 233 U as spike material for determining uranium in high enriched uranium materials, and CRM 116 ( 235 U mass fraction of [ 90 %) for determining uranium in materials of low enrichment. Keywords Isotope dilution mass spectrometry  Spike  Uranium concentration  Certified reference material  CRM 112-A  CRM 115 Introduction The Davies and Gray (D&G) titration, isotope dilution mass spectrometry (IDMS), and gravimetry are preferred methods of analyses to quantify the uranium contents in fissile material accountability measurements; these are the methods of choice in characterizing the elemental uranium contents in the preparation and issue of reference material and test material standards. In common, these methods yield results with traceability either directly to the funda- mental SI units or indirectly through higher level standards; in particular, the IDMS method is characterized as a pri- mary method with traceability to the SI unit of mole. In the IDMS method, the elemental uranium content of a sample is determined by diluting an aliquant of the sample solution with a spike solution, the latter derived from a standard material of known isotopic composition and ele- mental content, and determining the isotopic composition of the sample/spike mixture by the mass spectrometric method of analysis. At the New Brunswick Laboratory (NBL), IDMS measurements are usually done using spike solutions prepared from CRM 111-A—a certified reference material with high 233 U abundance. The present study was initiated to find other source materials to serve as spikes— the permitting ease of handling and storage in ‘‘radiologi- cal’’ laboratories. The primary goal is to identify a few among the many readily available certified uranium materials (CRMs) to serve as spikes in IDMS analyses. IDMS methodology and IDMS equation Principle The principle behind the IDMS method is to prepare a mixture of the sample and spike in known proportion fol- lowed by mass spectrometric measurements to determine the uranium isotopic composition. The uranium content is calculated using Eq. (1) by combining this measurement result with values for other known parameters—sample and spike sizes, uranium content and uranium isotopic A. Hasozbek (&)  K. J. Mathew  G. Orlowicz  N. Hui  B. Srinivasan  M. Soriano  U. Narayanan New Brunswick Laboratory, U.S. Department of Energy, 9800 South Cass Avenue, Building 350, Argonne, IL 60439, USA e-mail: altug.hasozbek@ch.doe.gov 123 J Radioanal Nucl Chem (2013) 296:447–451 DOI 10.1007/s10967-012-2050-1