Engineering topics

Despotopulos, John D.

Publications and source records attributed to Despotopulos, John D..

At least 19 records

DOE OSTI2025

Using radiochemistry to diagnose fuel-ablator mix in inertial confinement fusion studies at the National Ignition Facility: measurement of Tc/Mo isotopic ratios for the Pushered Single Shell campaign

The development of radiochemical measurement techniques as a diagnostic for fusion experiments at the National Ignition Facility enables a new method for assessing fuel-ablator mix and the impact of this mix on capsule performance. Diagnosing capsule mix in internal confinement fusion studies is difficult due to the small spatial scales (10s of µm) and short-time frames (100s of ps) over which the mix typically evolves in these experiments. For the Pushered Single Shell campaign, radiochemical measurements on debris collected from fusion experiments can be used to determine isotopic ratios of activation products, particularly 96g Tc/ 99 Mo and 95g Tc/ 99 Mo, to provide vital information on nuclear reactions in the burning plasma that can inform simulations that seek to understand the degree of capsule-fuel mix and the impact on the capsule performance. These radiochemical measurements have been conducted regularly since November 2023 providing data on a range of capsule designs and neutron yields. Data from eight NIF experiments is presented, the measured 96g Tc/ 99 Mo and 95g Tc/ 99 Mo range from (0.5–5) × 10 –4 to (0.3–3) × 10 –4 , respectively. The development of radiochemical diagnostics aids in understanding and optimizing the design of fusion experiments, providing unique and valuable insights into capsule behavior and directly measuring fuel-ablator mix.

and nuclear chemistry↗

DOE OSTI2024

Extraction of americium, curium, and californium with LN resin from HCl and HNO 3

The uptake of 241 Am, 244 Cm and 249 Cf with LN resin was studied in HCl and HNO3 solutions with concentrations ranging from 0.02 to 2.5 M. There is high uptake at concentrations < 0.1 M in both acids for all three isotopes with decreasing uptake at higher concentrations and negligible extraction at ≥ 0.6 M. Californium has a higher extraction than americium and curium, which are extremely similar. Kinetics studies showed rapid uptake of all three isotopes. Here, column studies were performed to demonstrate the separation of 241 Am and 249 Cf, and a bulk separation including nine stable lanthanides along with 241 Am, 249 Cf, and 88 Y.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2024

Extraction and separation of rare earth elements using LN resins in hydrochloric acid

The separation of the rare earth elements is essential for numerous scientific applications but remains a significant challenge due to the nearly identical chemical properties of the adjacent lanthanide elements. Eichrom’s LN series of extraction chromatographic resins feature organophosphorus extractants and are widely used to achieve adjacent lanthanide separations. While extensive characterization of these resins has been completed for nitric acid matrices, the use of hydrochloric acid is preferred for a variety of applications. Further, the extraction of the rare earth elements, La–Lu and Y, has been characterized on LN and LN2 resins in hydrochloric acid via batch uptake and column chromatographic studies.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2024

Group hexavalent actinide separation from lanthanides using sodium bismuthate chromatography

Advanced used nuclear fuel (UNF) reprocessing strategies are limited by the complex radiochemical separations and engineering required to achieve the separation of actinides (An) from neutron scavenging lanthanides (Ln). The accessibility of the hexavalent oxidation state for the actinides (U – Am) provides a pathway to achieving a group hexavalent actinide separation from the trivalent lanthanides and Cm. The solid oxidant and ion exchanger, sodium bismuthate (NaBiO 3 ), has been demonstrated to quantitatively oxidize and separate Am from trivalent Cm in a column chromatographic system. This work expands on the use of NaBiO 3 chromatography to characterize the adsorption, kinetic, and elution behavior of U, Pu, and Eu. Separation factors over 200 with rapid kinetics were observed at dilute nitric acid concentrations with a complete An/Ln separation achieved in under an hour. In conclusion, the adsorption and chromatographic behavior of key fission products present in various reprocessing raffinates was characterized which demonstrated potential application of a NaBiO 3 -based separation following a TRUEX process.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2024

Absolute decay counting of 146 Sm with 4π cryogenic microcalorimetry

We present a methodology for absolute activity counting of long-lived isotopes based on cryogenic Decay Energy Spectroscopy. A 146 Sm source was produced at the TRIUMF Laboratory and then processed and purified at Lawrence Livermore National Laboratory, yielding a pure sample. The source was embedded within a 4π thermal absorber coupled to a magnetic microcalorimeter achieving nearly 100% counting efficiency. Experimental uncertainties were studied and modeled, including thermal coupling of the source to the absorber, pulse pile-up, trigger, and event selection efficiencies. Here, the absolute activity of the pure 146 Sm source was measured to better than 1% uncertainty.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

Simple separation of technetium from molybdenum for tracer isotope production

A procedure for the separation of technetium isotopes from bulk molybdenum was developed in nitric acid media. After irradiation of nat Mo foils, and dissolution in H 2 O 2 , the solution is acidified to 2 M HNO 3 , and anion exchange resin is used to separate technetium from molybdenum. The procedure is simple, requiring only basic laboratory equipment and, with a two-column separation, the technetium yield is high (~ 85%) with extremely high purity (< 0.1 ppm nat Mo). In conclusion, this is ideally suited for laboratory production of technetium tracer isotopes, particularly 95m Tc.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2024

Uptake behavior of 73 As, 75 Se, 197m Hg, 212 Pb and 210 Po on Eichrom pre-filter resin from HCl and HNO 3

We report the extraction of 73 As, 75 Se, 197 mHg, 212 Pb and 210 Po on Eichrom pre-filter resin was studied in HCl and HNO 3 with batch uptake, kinetic and column experiments. There was significant extraction of mercury in HNO 3 and HCl, and polonium and selenium in HCl. The kinetics are sufficient to allow for retention on pre-filter columns, and separations of 73 As from 75 Se and 197 mHg, and 212 Pb from 210 Po are demonstrated. This retention is important for the development of chemical separations as pre-filter resin is commonly used alongside extraction chromatography resins but its potential for uptake of metal ions is not well characterized.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2024

Extraction of 88 Y, 152 Eu, 228 Ac, 241 Am, and 244 Cm with 2-thenoyltrifluoroacetone (TTA) resin

In this report the behavior of 88 Y, 152 Eu, 228 Ac, 241 Am, and 244 Cm was studied with 2-thenoyltrifluoroacetone resin with batch uptake, kinetics and column studies. Studies were performed in acetate buffer solutions (pH ~ 2 to ~ 6) and there was high uptake of all isotopes, except 228 Ac, at pH > 4.5. The kinetics of uptake were reasonable, although slower for the actinides, and sufficient for column studies. The retention of 88 Y, 152 Eu, and 241 Am on the resin in column studies was demonstrated as well as a reasonable separation of these isotopes from 228 Ac.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2024

Radiochemical diagnostics at the National Ignition Facility

Since the National Ignition Facility (NIF) was commissioned in 2009, radiochemical techniques have been viewed as a potential method for diagnosing the performance of an NIF fusion shot. Radiochemical methods can also be used in conjunction with NIF shots to measure nuclear reaction cross sections in regimes that are inaccessible at accelerator facilities and can provide a route to produce radioactive tracer materials that can be used for other applications. Here, this review presents the current status of radiochemical diagnostics at the NIF. Experimental results and the status of both solid and gaseous debris collection radiochemistry are presented.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2024

Uptake of arsenic and selenium on iron-doped Pb resin

We report the uptake of the radioisotopes 73 As and 75 Se was characterized on Fe 3+ -doped Pb resin (Eichrom Technologies) from pH 1 to 12. There is good uptake of arsenic and selenium over a wide pH range (~ 1 to 10) with a decrease only at high pH (~ 12). Column experiments were performed to demonstrate the separations of these elements from solutions with near neutral pH values (~ 6 to 8) with high yields and high radiopurity. These separations may be relevant for a wide variety of applications especially isotope harvesting research.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2023

Uptake behavior of arsenic and selenium with sulfur-based extraction chromatography resins in HCl and HNO 3 media

Here, the uptake behavior of 73 As and 75 Se was studied in HCl and HNO3 media with CL resin, ethanethiol resin and dimethyl sulfide resin. In HCl solutions, there was high extraction of selenium on CL resin and ethanethiol resin but lower uptake on dimethyl sulfide resin; arsenic was only extracted by CL resin. From HNO 3 , selenium was extracted only by ethanethiol resin and CL resin and there was no uptake of arsenic on any resin. While the sulfur-based resins have high selenium uptake and selectivity, column separations are challenging due to the chemical instability of these resins.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2023

Synergistic extraction of rare earth elements, actinium, americium, and barium with TTA and Pb resin from acetate buffer solutions

The uptake behavior of 88 Y, 140 Ba, 140 La, 141 Ce, 152 Eu, 228 Ac, and 241 Am was studied with batch uptake, kinetics and column studies in a synergistic extraction system with Pb resin and 2-thenoyltrifuoroacetone in acetate-ethanol solutions. The k' values are very high (>10,000) at near neutral pH (~5 to 6) for all of the radioisotopes studied. The kinetics are reasonably fast for column separations, though the uptake rate is dependent on the concentration of 2-thenoyltrifuoroacetone. Column studies were performed to demonstrate the separation of the trivalent actinides and lanthanides from barium and common fssion products ( 99 Mo, 103 Ru).

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2023

Behavior of selenium and arsenic in $\mathrm{HCl}$ and $\mathrm{HNO}$ 3 on $\mathrm{TRU, TEVA, DGA,}$ and $\mathrm{Pb}$ extraction chromatography resins

The uptake behavior of 73 As and 75 Se was studied in HCl and HNO 3 -H 2 O 2 solutions on commercial extraction chromatography resins (TEVA, TRU, DGA, and Pb resin). There was no uptake of 73 As or 75 Se from HNO 3 media. From HCl, there was 75 Se uptake at high concentrations on all the resins and no uptake of 73 As. Separations of 75 Se and 73 As on these resins have high yields and high radiopurity for 73 As, but limited recovery of 75 Se. TRU and TEVA resin may have potential for use in isotope generators as 75 Se can be retained for at least 26 days with repeated elutions.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2023

Harvesting 88 Zr from heavy-ion beam irradiated tungsten at the National Superconducting Cyclotron Laboratory

Tungsten is a commonly used material at many heavy-ion beam facilities, and it often becomes activated due to interactions with a beam. Many of the activation products are useful in basic and applied sciences if they can be recovered efficiently. In order to develop the radiochemistry for harvesting group (IV) elements from irradiated tungsten, a heavy-ion beam containing 88 Zr was embedded into a stack of tungsten foils at the National Superconducting Cyclotron Laboratory and a separation methodology was devised to recover the 88 Zr. The foils were dissolved in 30% hydrogen peroxide, and the 88 Zr was chemically purified from the tungsten matrix and from other co-implanted radionuclides (such as 85 Sr and 88 Y) using strong cation-exchange (AG MP-50) chromatographic resin in sulfuric acid media. The procedure provided 88 Zr in approximately 60 mL 0.5 M sulfuric acid with no detectable radio-impurities. The overall recovery yield for 88 Zr was (92.3 ± 1.2)%. In conclusion, this proof-of-concept experiment has facilitated the development of methodologies to harvest from tungsten and tungsten-alloy parts that are regularly irradiated at heavy-ion beam facilities.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2023

Extraction of selenium and arsenic with TOA-impregnated XAD-2 resin from HCl

Here the uptake of 75 Se and 73 As on trioctylamine-impregnated resin from HCl solutions was studied with batch uptake, kinetics, and column studies. Selenium-75 extracts well (D w ~ 900) at high HCl concentrations (≥ 10 M) with and no extraction of 73 As at any HCl concentration. The uptake kinetics were slow with low extraction (D w < 100) for time periods ≤ 15 min and no clear equilibrium achieved even after 24 h. Column studies were performed to characterize the separation of 75 Se and 73 As; 75Se is retained from conc. HCl while arsenic is eluted with high yields and high radiopurity.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2022

Chemical separation of 146 Sm for half-life determination

Here, although methods for the chemical separation of samarium from a rock matrix are well established, chemical separation of samarium from non-natural isotopic impurities for the purpose of 146 Sm half-life measurement requires modifications to these procedures, as well as additional checks for effective separation. This work describes the chemical purification procedures associated with the 146 Sm source and the results from gamma spectroscopy. The purification procedure allowed for the quantitative determination of the number of 146Sm atoms using a modified isotope dilution technique. Alpha-decay counting of the sample will be applied in the future to determine the half-life of 146 Sm.

146Sm↗

DOE OSTI2022

Radiochemical capabilities for astrophysics experiments at the national ignition facility

The Nuclear and Radiochemistry Group at Lawrence Livermore National Laboratory (LLNL) has developed a suite of diagnostics and techniques that can be used for astrophysics experiments at the National Ignition Facility (NIF). Capabilities have been developed to add material to the outside of NIF hohlraum assemblies as well as to the interior of NIF target capsules or the fill gas. The ability to place very small amounts of material close to the NIF target enables activation with very large, short-pulse neutron fluxes. The Solid Radiochemistry Diagnostic can be used to collect solid debris from a NIF shot within 2 h of the execution of a shot, and this can be analyzed for radioactive signatures with or without post-shot chemical processing. The Radiochemical Analysis of Gaseous Samples diagnostic system can be used to collect gaseous products produced during a NIF shot. Capsule doping and radiochemical analysis capabilities at NIF will be discussed. The application of these techniques to astrophysical measurements will be discussed as well as some preliminary results.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2022

Solid-phase isotope harvesting of 88 Zr from a radioactive ion beam facility

During routine operation of the Facility for Rare Isotope Beams (FRIB), radionuclides will accumulate in both the aqueous beam dump and along the beamline in the process of beam purification. These byproduct radionuclides, many of which are far from stability, can be collected and purified for use in other scientific applications in a process called isotope harvesting. In this work, the viability of 88 Zr harvesting from solid components was investigated at the National Superconducting Cyclotron Laboratory. A secondary 88 Zr beam was stopped in a series of collectors comprised of Al, Cu, W, and Au foils. Here, this work details irradiation of the collector foils and the subsequent radiochemical processing to isolate the deposited 88 Zr (and its daughter 88 Y) from them. Total average recovery from the Al, Cu, and Au collector foils was (91.3 ± 8.9) % for 88 Zr and (95.0 ± 5.8) % for 88 Y, respectively, which is over three times higher recovery than in a previous aqueous-phase harvesting experiment. The utility of solid-phase isotope harvesting to access elements such as Zr that readily hydrolyze in near-neutral pH aqueous conditions has been demonstrated for application to harvesting from solid components at FRIB.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗