SEDL / STP / STP1344-EB / STP15721S

Uranium Isotope Measurements by Quadrupole ICP-MS for Process Monitoring of Enrichment

Policke, TA
Principal Technical Specialist, BWX Technologies, Inc., Lynchburg, VA

Bolin, RN
Technical Specialist III, E&QAD, BWX Technologies, Inc., Lynchburg, VA

Harris, TL
Chemistry Laboratory Manager, E&QAD, BWX Technologies, Inc., Lynchburg, VA

Pages: 13    Published: Jan 1998

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Abstract

Historically, uranium isotopic ratio measurements in the nuclear industry have been performed using Thermal Ionization Mass Spectrometry (TIMS); primarily due to the high level of precision that can be achieved. TIMS analysis, however, requires sample purification and intricate sample loading. Quadrupole (low resolution, single detector) inductively coupled plasma — mass spectrometry, Q-ICP-MS, overcomes these disadvantages and is a cost-effective alternative, i.e., in terms of initial capital, maintenance, and operating costs. This paper presents a simple, single standard approach for measuring uranium isotope content in various solid and liquid nuclear materials along with some comparison data of Q-ICP-MS and TIMS. Intensity ratios of ²³⁴U, ²³⁵U, ²³⁶U, and ²³⁸U to total U intensity are produced, providing the enrichment level or percent ²³⁵U. A detailed description of the instrument and data collection parameters is also provided. Optimal precision and accuracy are achieved through the use of a single standard which is closely matched to the enrichment and concentration of the samples. Depending upon the standard chosen, enrichments between depleted and 97% can be quantified. Standard deviations for the major uranium isotopes are typically within 0.02 absolute and at least an order of magnitude lower for the minor U isotope abundances.