Investigation of chemical form effects on Zr isotopic ratios measured by atom probe tomography
EMSL Project ID
50177
Abstract
The goal of this work is to determine the effects of hydrides and oxides on isotopic measurements obtained using atom probe tomography (APT). Zirconium enriched to 72-97% 92Zr is proposed as the reference material for its ability to readily form oxides and hydrides and its relevance to the energy sector for use in nuclear reactors as zircalloy cladding. A set of twelve enriched atom probe tips, four per chemical form (metal, oxide, hydride), would be analyzed to gather compositional information and explore the spatial distribution of hydrogen. A set of natural zirconium tips in the hydride form will be used as a reference to determine the ratios of the hydride peaks to the monatomic Zr.In the ideal case APT produces monatomic ions that make up the mass spectrum. However, the presence of complex ions, when two or more ions evaporate as a compound, can lead to convolution of data. In the analysis of nanodiamonds (Heck et al., 2012) reported a conflation of 12C1H and 13C which resulted in a lower than expected 12C/13C ratio. While an analysis of enriched U3O8 (Fahey et al., 2016) noted that only compounds of the form of UOx were identified in the mass spectrum with no monatomic U present. This observation was in direct contrast with other mass spectroscopy techniques performed, such as SIMS, where monatomic U was measured with no detectable UOx. A systematic study using zirconium in separate chemical forms would enable the effects of complex ions on the mass spectrum to be clearly defined to improve calculations of isotopic and elemental abundances.
The EMSL facility at PNNL provides access to machines unavailable at UC Berkley which would serve as the lynchpins of the project. The first, a LEAP 4000 XHR will perform the atom probe analysis of the zirconium references. Additionally, the EMSL LEAP is equipped with a reaction chamber which can flow hydrogen and oxygen gas over the newly manufactured tips to produce the zirconium oxide and hydride.
Project Details
Project type
Exploratory Research
Start Date
2018-10-21
End Date
2019-09-30
Status
Closed
Released Data Link
Team
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