Extraction of plutonium-containing microcrystals from Hanford soil using a focused ion beam for single-crystal X-ray diffraction analysis

Abstract

Herein, the successful use of a focused ion beam/scanning electron microscope to prepare microsamples of radioactive single crystals for X‐ray diffraction analysis is reported. This technique was used to extract and analyze crystalline Pu‐containing particles as small as 28 µm3 from Hanford soil taken from the 216‐Z‐9 waste crib, which were then crystallographically characterized using single‐crystal X‐ray diffraction to confirm the cubic structure of PuO2. As a systematic proof of concept, the technique was first tested using UO2 crystals milled into cubic shapes with approximate volumes of 4620, 1331, 125, 8 and 1 µm3, in order to empirically determine the crystal size limits for characterization by a laboratory‐based diffractometer with a sealed tube Mo or Ag anode X‐ray source and a charge‐coupled device detector.

X-ray diffraction using focused-ion-beam-prepared single crystals

“…Crystals with a reproducible and defined shape and size were obtained. Corbey et al (2019) reported a similar study for the FIB preparation of radioactive materials intended for a crystal structure analysis. In comparison to Corbey et al (2019), we performed smaller cuts with the ion beam to reduce beam damage on the sample.…”

“…Note that all refinements were based on F, except that by Abrahams & Marsh (1986) the sample could be reduced to a minimum, which is important especially for hazardous samples (Corbey et al, 2019). Corbey et al (2019) presented an additional procedure for transferring the samples from the FIB tip to a MiTeGen MicroMount and fixing that sample with a carbon patch. Although this is an extra preparation step, the influence of additionally absorbing materials can be minimized.…”

“…This method of sample preparation is known from the field of electron microscopy (Reyntjens & Puers, 2001;Jarmar et al, 2008;Heaney et al, 2001;Wirth, 2004;Meng et al, 2011;Orloff et al, 2003;Zhou & Wang, 2007;Yao, 2007). Okamoto et al (2014) and Corbey et al (2019) have already shown that using a FIB to prepare samples has advantages in the field of SC-XRD. Besides the preparation of small and well defined samples (Okamoto et al, 2014), this preparation method can be used for especially challenging samples (Corbey et al, 2019), such as (1) inclusions, (2) samples which are mixed with or embedded in undesirable materials, (3) materials which are difficult to grow as single crystals, and (4) hazardous materials that are, for example, radioactive or toxic.…”

“…Okamoto et al (2014) and Corbey et al (2019) have already shown that using a FIB to prepare samples has advantages in the field of SC-XRD. Besides the preparation of small and well defined samples (Okamoto et al, 2014), this preparation method can be used for especially challenging samples (Corbey et al, 2019), such as (1) inclusions, (2) samples which are mixed with or embedded in undesirable materials, (3) materials which are difficult to grow as single crystals, and (4) hazardous materials that are, for example, radioactive or toxic. Corbey et al (2019) compared results of the structure determination of well defined radioactive samples with different volumes.…”

“…Besides the preparation of small and well defined samples (Okamoto et al, 2014), this preparation method can be used for especially challenging samples (Corbey et al, 2019), such as (1) inclusions, (2) samples which are mixed with or embedded in undesirable materials, (3) materials which are difficult to grow as single crystals, and (4) hazardous materials that are, for example, radioactive or toxic. Corbey et al (2019) compared results of the structure determination of well defined radioactive samples with different volumes. However, they neither discussed the influence of ionbeam radiation damage on the structure analysis nor compared different preparation techniques.…”