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Zirakparvar, N. Alex

Publications and source records attributed to Zirakparvar, N. Alex.

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A preliminary investigation into the feasibility of laser ablation U–Pb isotope ratio measurement via all‐faraday cup detection with 10 11 ‐ and 10 13 ‐Ω amplifiers on the Neoma multicollector‐inductively coupled plasma‐mass spectrometer

Rationale Signal detection for uranium–lead (U–Pb) dating of zircon is typically performed via ion counters. Here, we develop a preliminary understanding of the strengths and limitations of faraday‐cup‐based detection. Methods A suite of zircon reference materials and the NIST‐610 glass were sampled using laser ablation followed by U–Pb isotope ratio measurement on a Neoma multicollector‐inductively coupled plasma‐mass spectrometer. Results We were able to produce geologically accurate 207 Pb/ 206 Pb, 206 Pb/ 238 U, and 207 Pb/ 235 U ratios for the NIST‐610 glass and the zircon standards, with ages ranging from ~2.5 Ga to ~337 Ma (TanBrown A, Oracle, 91550, Mud Tank, Temora, and Plešovice). Two of the younger zircon standards examined (94‐35, ~55.6 Ma, and Fish Canyon, 28.6 Ma) yielded accurate 206 Pb/ 238 U but not 207 Pb/ 235 U or 207 Pb/ 206 Pb ratios, whereas the youngest zircon standard (Penglai, ~4.4 Ma) failed for all three ratios of interest. The accuracy and precision of the all‐faraday method are directly tied to signal intensity, with reliable data capable of being produced even when both isotopes in a ratio have signals below ~0.001 V (equivalent to ~62 500 cps on an ion counter). Conclusion The all‐faraday cup multicollection method provides sufficient sensitivity to obtain geologically meaningful U–Pb data, with possible advantages being that laser pit depth‐dependent changes in the observed interelemental fractionation behavior may be easier to correct using a static collector configuration compared to when the ion beam is swept across a single detector while also removing the need for an interdetector‐type calibration. Further work is needed to refine the all‐faraday cup method (e.g., application of background subtraction and common Pb corrections, outlier removal, and interelement as well as down‐hole fractionation corrections), but our initial results demonstrate that the faraday detector method has sufficient sensitivity to warrant further study.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Uranium Single Particle Analysis for Simultaneous Fluorine and Uranium Isotopic Determinations via Laser-Induced Breakdown Spectroscopy/Laser Ablation–Multicollector–Inductively Coupled Plasma–Mass Spectrometry

Uranyl fluoride (UO 2 F 2 ) particles (<20 μm) were subjected to first-of-its-kind analysis via simultaneous laser-induced breakdown spectroscopy (LIBS) and laser ablation multi-collector inductively coupled plasma–mass spectrometry (LA–MC–ICP–MS). Briefly, a nanosecond pulsed high-energy laser was focused onto the sample (particle) surface. In a single laser pulse, the UO 2 F 2 particle was excited/ionized within the microplasma volume, and the emission of light was collected via fiber optics such that emission spectroscopy could be employed for the detection of uranium (U) and fluorine (F). The ablated particle was simultaneously transported into the MC–ICP–MS for high precision isotopic (i.e., 234 U, 235 U, and 238 U) analysis. This method, LIBS/LA–MC–ICP–MS was optimized and employed to rapidly measure 80+ UO 2 F 2 particles, which were subjected to different calcination processes, which results in varying degrees of F loss from the individual particles. In measuring the particles, the average F/U ratios for the populations treated at 100 and 500 °C were 2.78 ± 1.28 and 1.01 ± 0.50, respectively, confirming loss of F through the calcination process. The average 235 U/ 238 U on the particle populations for the 100 and 500 °C were 0.007262 (22) and 0.007231 (23), which was determined to be <0.2% from the expected value. The 234 U/ 238 U ratios on the same particles were 0.000053 (11) and 0.000050 (10) for the 100 and 500 °C, respectively, <10% from the expected value. Notably, each population was analyzed in under 5 min, demonstrating the truly rapid analysis technique presented here in this paper.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Microextraction–TQ–ICP–MS for the Direct Analysis of U and Pu from Cotton Swipes

Here, the microextraction sampling technique was integrated with triple quadrupole–inductively coupled plasma–mass spectrometry (TQ–ICP–MS) to directly sample and measure the isotopic compositions of uranium (U) and plutonium (Pu) from cotton swipes. Once extracted, the U/Pu were directed into the TQ–ICP–MS instrument for isotopic determination. Carbon dioxide (CO 2 ) and helium (He) gases were delivered to a collision reaction cell within the ICP–MS system for ion separation. The CO 2 reacts with the U + forming UO + which is ultimately separated from the Pu + ions of interest in the third quadrupole. This study demonstrates direct liquid extraction of U/Pu from a solid surface and subsequent measurement by TQ–ICP–MS in <60 s. Flow rates were optimized (0.3 mL min –1 CO 2 and 5 mL min –1 He) in the reaction cell of the ICP–MS system to maximize the Pu signal while minimizing U interferences (i.e., 238 U + tail and 238 UH + ) at m/z 239. Low levels of Pu (~2 pg) were deposited on a cotton swipe along with U at concentrations ranging from 20 to 200 ng. The 240 Pu/ 239 Pu ratio was measured with <7% relative difference from the certified value at all U concentrations. Major and minor U isotope ratios were also measured with <4% relative difference. This highlights that the microextraction–TQ–ICP–MS method can extract a mixed U/Pu sample directly from a cotton swipe and measure both isotopic systems without chemical separation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Exploration of LIBS as a novel and rapid elemental mapping technique of nuclear fuels in the form of surrogate TRISO particles

Laser-induced breakdown spectroscopy (LIBS) was employed to characterize coatings on surrogate fuel particles. Tri-structural isotropic (TRISO) particles are a proposed nuclear fuel alternative for high temperature reactors. These particles are constructed of a ZrO 2 kernel (as a surrogate to uranium), surrounded by an inner pyrolytic carbon layer and are surrounded by an outer carbide layer (ZrC, presented here) to act as a barrier to fission products generated during nuclear reactions. These particles are embedded within a graphite compact and housed within the reactor core. Simply put, due to their robust nature, performing elemental analysis of these particles poses a challenge. Presented here, LIBS is explored as a method for characterizing elemental constituents of these particles, with the focus being on rapid elemental mapping and depth profiling. Different from traditional elemental analysis techniques (e.g., inductively coupled plasma – based methods), LIBS is advantageous because it can directly analyze the sample surface and can detect light elements such as C and O, making it a viable technique for the analysis of small, multilayered particles as spatial elemental information is warranted in the production of these particles. In the work presented here, LIBS was successfully used for discerning small layers (30–50 μm), detecting the location of carbon and oxygen layers, providing fast 2-D mapping (<5 min per particle) and rapid depth profiling (10 s per particle).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

The need for speed – Burnup determination of spent nuclear fuel

Here we present the application of a novel analytical approach for high-speed evaluation of burn-up in spent nuclear fuel. This automated online separation–direct analysis method, which simultaneously measures the isotopic compositions and concentrations of Nd, Pu, and U using isotope dilution-inductively coupled plasma mass spectrometry, enables the determination of burnup in as little as 4.5 h per sample with expanded uncertainties as low as 1.2% using as little as 1µg of fuel. We compare the determined burn-up values, sample requirements, and analysis times with an ultra-high precision, in-house developed, methodology which employs multiple analytical techniques to measure the isotopic compositions and concentrations of Nd, Pu, and U yielding burn-up values with expanded uncertainties as low as 0.49% at the 95% confidence level, the lowest reported to date.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Determination of fluorine distribution in shark teeth by laser-induced breakdown spectroscopy

Quantifying the chemical composition of fast-growing hard tissues in the environment can shed valuable information in terms of understanding ecosystems both prehistoric and current. Changes in chemical composition can be correlated with environmental conditions and can provide information about the organism's life. Sharks can lose 0.1 to 1.1 teeth/day, depending on species, which offers a unique opportunity to record environmental changes over a short duration of time. Shark teeth contain a biomineral phase that is made up of fluorapatite [Ca 5 (PO 4 ) 3 F], and the F distribution within the tooth can be correlated to tooth hardness. Typically, this is determined by bulk acid digestion, energy-dispersive X-ray spectroscopy (EDS), or wavelength-dispersive spectroscopy. Here we present laser-induced breakdown spectroscopy (LIBS) as an alternative and faster approach for determining F distribution within shark teeth. Using a two-volume laser ablation chamber (TwoVol3) with innovative embedded collection optics for LIBS, shark teeth were investigated from sand tiger (Carcharias Taurus), tiger (Galeocerdo Cuvier), and hammerhead sharks (Sphyrnidae). Fluorine distribution was mapped using the CaF 603 nm band (CaF, Β 2 Σ + → X 2 Σ + ) and quantified using apatite reference materials. In addition, F measurements were cross referenced with EDS analyses to validate the findings. Distributions of F (603 nm), Na (589 nm), and H (656 nm) within the tooth correlate well with the expected biomineral composition and expected tooth hardness. This rapid methodology could transform the current means of determining F distribution, particularly when large sample specimens (350 mm 2 , presented here) and large quantities of specimens are of interest.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Direct analysis of cotton swipes for plutonium isotope determination by microextraction-ICP-MS

This study demonstrates a method for determining the isotopic composition of low-level (sub-pg) plutonium (Pu) directly from a cotton swipe. Environmental sample (ES) swipes are routinely employed as a tool for monitoring activities in nuclear facilities. Traditional ES swipe analysis, as employed in nuclear safeguards, utilizes laborious ashing, digestion, and chemical separation procedures prior to mass spectrometric (MS) analysis. Here, an innovative sample introduction technique employing a microextraction probe to extract Pu directly from the swipe surface is described. The microextraction probe lowers onto the swipe surface, seals on a small area (8 mm 2 ), and delivers solvent (2% HNO 3 ) to extract actinide material that may be present. The extracted analyte is subsequently directed into a sector field inductively coupled plasma (ICP)-MS for isotope ratio determination. This microextraction-ICP-MS method successfully determined the isotopic composition ( 240 Pu/ 239 Pu and 242 Pu/ 239 Pu) of three Pu certified reference materials (CRM 136, 137, and 138) that were deposited (1 pg) onto ES swipes. The percent relative difference from the certified value, uncorrected for instrumental fractionation, was <2% for the 240 Pu/ 239 Pu ratio on all three CRMs and <10% for the 242 Pu/ 239 Pu ratio on CRM 136 and 138. Here, the percent relative standard deviation, an estimate of the sample-to-sample isotopic precision, was <4% for the 240 Pu/ 239 Pu and <15% for the 242 Pu/ 239 Pu. Method limits of detection were determined, based on measurements of an enriched 244 Pu material, to be ~7 fg. Additionally, a mixed uranium (U) and Pu deposition was made to determine the method's ability to simultaneously extract U and Pu and determine the isotopic composition of both analytes.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Rapid and automated separation of uranium ore concentrates for trace element analysis by inductively coupled plasma – optical emission spectroscopy/triple quadrupole mass spectrometry

The present study documents an automated approach to performing elemental analysis on a large group uranium ore concentrate (UOC) samples. In this work, 17 UOC samples, 2 quality control samples, and 26 process blanks were purified sequentially through a single 500 μL Uranium and TEtra Valent Actinides (UTEVA®) column. For each sample, the trace elemental impurities were separated from its dissolved uranium matrix on the UTEVA column and collected for analysis by inductively coupled plasma – optical emission spectroscopy / triple quadrupole mass spectrometry (ICP-OES/TQMS). The UTEVA column was subsequently regenerated prior to separation of the following sample. The column was efficiently regenerated, for each UOC, even after processing ~50 mg of uranium, cumulatively. The validity of the method was established by determining the trace impurities of two quality control uranium reference samples (CRM 124–1 and CUP-2). The current trace element measurements from the 17 UOC samples were compared to previously reported values from an interlaboratory comparison exercise, when available. The methodology employed here produces trace elemental analysis with excellent correlation to the previously reported data for many of the elements / samples, particularly when viewed through the context of existing geochemical comparisons tools (e.g. chondrite normalized variation plots).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Trace Elemental Analysis of Bulk Thorium Using an Automated Separation–Inductively Coupled Plasma Optical Emission Spectroscopy Methodology

Presented here is a novel automated method for determining the trace element composition of bulk thorium by inductively coupled plasma–optical emission spectroscopy (ICP-OES). ICP-OES is a universal approach for measuring the trace elemental impurities present in actinide-rich materials; however, due to the emission rich spectrum of the actinide, a separation from the trace elements is warranted for spectrochemical analysis. Here, AG MP-1 ion exchange resin was utilized for retention of the Th matrix, while allowing the trace element impurities to be separated prior to subsequent analysis using ICP-OES. After demonstrating the separation on traditional gravity-driven columns, the methodology was transitioned to an automated platform for comparison. This automated platform utilizes syringe-driven sample and solvent flow and can collect the trace element and thorium fractions in separate locations. Finally, while reducing the sample size (500 µL, 1.5 mg of Th), maintaining the overall separation efficiency (recoveries >95%), and illustrating the sample throughput ability (n = 10+), this automated methodology could be readily adopted to nuclear facilities in which the determination of trace elemental impurities in Th samples is warranted.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

A preliminary investigation into the use of molecular oxide and hydride secondary ion relationships for improvement of the 236U/238U determination on a NanoSIMS 50L

Abstract A NanoSIMS 50L is used to investigate uranium molecular ( 235 U 16 O, 236 U 16 O, 238 U 16 O, 235 U 1 H, 238 U 1 H, 236 U 16 O 1 H, and 238 U 16 O 1 H) and elemental ( 235 U, 236 U, and 238 U) secondary ion production during sputtering of synthetic UO 2 and the NIST-610 standard to determine if: (1) the 236 U 16 O/ 238 U 16 O molecular oxide ratio performs better than the 236 U/ 238 U elemental ratio, and (2) there is co-variance between the molecular hydrides and oxides. Despite an order of magnitude greater abundance of 236 U 16 O secondary ions (compared to 236 U), the 236 U 16 O/ 238 U 16 O ratios are less accurate than the 236 U/ 238 U ratios. Further work is needed before the higher count rate of the 236 U 16 O secondary ion can be used to obtain a better 236 U/ 238 U ratio. The second objective was undertaken because correction for the interference of 235 U 1 H on the 236 U secondary ion species typically utilizes the 238 U 1 H/ 238 U ratio. This becomes problematic in samples containing 239 Pu, so our aim was to understand if the hydride formation rate can be constrained independently of having to measure the 238 U 1 H. We document correlations between the hydride ( 238 U 1 H and 238 U 16 O 1 H) and oxide ( 236 U 16 O) secondary ions, suggesting that pursuing an alternative correction regime is worthwhile.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗