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At least 739 records · Page 41

A high-temperature Rutherford Backscattering Spectrometry apparatus for in situ material characterization

A new methodology for high-temperature Rutherford Backscattering Spectrometry (HT-RBS) has been developed to enable in situ material characterization at elevated temperatures. A 3.5 MeV proton beam penetrates a 10-µm-thick 316L stainless steel foil mounted on a graphite substrate, with backscattered signals detected using an HT-RBS system. Conventional semiconductor detectors, primarily based on silicon, suffer significant performance degradation at temperatures higher than ~ 60 °C due to increased leakage current and noise, leading to signal distortion and failure. Here, to preserve spectral quality, a 5 µm aluminum foil shields the detector from thermal radiation, allowing reliable operation up to 900 °C at the target. A rotatable shutter provides additional thermal isolation during data collection pauses. In situ measurements of areal density changes of 316L stainless steel were conducted to validate the technique, revealing consistency with the known thermal expansion coefficient. The method facilitates seamless switching between irradiation and analysis, enabling continuous studies. This approach supports in situ investigations of diffusion, void swelling, creep, and corrosion, offering a versatile tool for advanced materials research.

36 MATERIALS SCIENCE↗

H⁰ Stark Stripping and Component Irradiation in Fermilab Booster

In foil stripping of H⁻ some fraction of the emerging neutral H⁰ will be in excited states, which can then strip through the Stark effect in the magnetic field of the downstream orbit bump magnet. The resultant H⁺ will experience a depleted net kick compared to protons emerging from the foil and will track on trajectories different from the nominal circulating beam. This will lead to irradiation of downstream machine components. An analysis of these processes is of particular importance looking forward to the much higher beam power of the Fermilab PIP-II era. This study investigates where these errant protons will be lost, how much power is deposited, and whether this will be a shielding concern.

43 PARTICLE ACCELERATORS↗

Dense Pair and Gamma-Ray Creation Using Ultra-Intense Lasers (Final Technical Report)

Lasers with intensity >1.4x10 18 W.cm -2 irradiating solid targets couple 10-50% of its energy to “hot electrons” near the critical surface, with temperature kT > mc 2 . When these hot electrons impact high-Z target ions (e.g. Au, Pt), they emit copious bremsstrahlung gamma-rays and create e + e - pairs via the Trident process. For targets thicker than ~0.1mm, the gamma-rays create secondary pairs via the Bethe-Heitler processes. The concept of using lasers to create pairs was first studied by Shearer et al (1973). Motivated by the rapid advance of short-pulse ultra-intense lasers based on chirped-pulse amplification, Liang (1994) first proposed irradiating solid Au targets with laser intensity ≥10 20 W.cm -2 to create dense e + e - pairs. Using particle-in-cell (PIC, Birdsall and Langdon, 1991) simulations, Liang et al (1998, 2002) estimated that high-energy PW lasers can in principle achieve ultra-high in-situ pair densities. Subsequent studies supported this idea and found that for gold foils thicker than ~50 μm, the pair yield is dominated by the Bethe-Heitler (BH, Heitler 1954) process. Cowan et al (1999, 2000) using the LLNL Nova PW-laser to irradiate 125μm gold foils first observed pair creation, followed by Chen et al (2009) who demonstrated copious BH pair creation using the Titan, Omega-EP and Orion lasers. However, the emerging e + /e - ratio of these experiments was ≤ few %, and the pair density was only 10 13 /cc so that the pair jet transverse size R(~mm) was < pair skin depth c/ω + (=8πn+e 2 /m) 1/2 ). This was insufficient to qualify as a bona fide ”pair plasma”.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Recovery and Recycle of Irradiated Low-Enriched Uranium from the Production of 99 Mo

Technetium-99m ( 99m Tc), the daughter (decay product) of molybdenum-99 ( 99 Mo), is the most commonly used medical radioisotope in the world. 99 Mo is produced primarily from the fissioning of 235 U. A potential future producer, Eden Radioisotopes, is planning to irradiate low-enriched-uranium metal-foil targets for production of 99 Mo. Their plan is to recover, purify, and recycle the irradiated LEU in a new set of targets inside their facility. This study assesses processes to (1) purify and recycle uranium following 99 Mo recovery and (2) convert the uranium to metal for subsequent foil production and target fabrication. A UREX (uranium recovery by extraction) liquid–liquid extraction flowsheet that utilizes centrifugal contactors was developed using the Argonne model for universal solvent extraction (AMUSE) to recover and purify the uranium. The calculated flowsheet predicted high decontamination from Pu and most fission products and >99.99% recovery of uranium. Suggestions for conversion of the UREX U-product (uranyl nitrate in dilute nitric acid) to U metal were provided based on literature studies and earlier laboratory studies performed at Argonne National Laboratory.

07 ISOTOPE AND RADIATION SOURCES↗

(U) Updated Godiva-IV Benchmark Preview

A note of errata prepended to the Godiva-IV delayed-critical benchmark (HEU-METFAST-086) identifies two corrections that need to be made to the model: The glory hole in the spindle should be made larger, and the height of the safety block should be made smaller (and therefore its density made larger). In addition, the safety block at its full-in position is closer to the inner subassembly plate than was modeled in the benchmark. These changes have been made to HEU-METFAST-086 Case 4 in order to estimate the effect on k eff and on the neutron flux spectrum. Using smaller separation, a smaller safety block, and a larger glory hole caused k eff to increase by 453 ± 1 pcm from the benchmark. The latest nuclear data, ENDF-B/VIII.0, have also been used; this caused k eff to increase another 37 ± 1 pcm. Flux spectra were compared in a modeled fission foil and at three external point detectors. Within the fission foil, using ENDF/B-VIII.0 for Godiva-IV induced changes in the flux spectrum similar in size to the changes due to using smaller separation, a smaller safety block, and a larger glory hole. At the point detectors, using ENDF/B-VIII.0 induced changes in the flux spectrum much larger than those due to changing the model. In other words, the corrections to the benchmark model cause a large increase in k eff , but the changes to the neutron flux spectrum are small compared to those caused by using the latest nuclear data. This study presents a preview of results expected during the reevaluation of the Godiva IV benchmark, but it is not a substitute for the full reevaluation

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Development of Multi-Filament Textured-Powder Bi-2212/Ag Wire with Enhanced Local Area Ratio (Final Technical Report)

ATC has successfully developed a new method for making high-performance Bi-2212/Ag su-perconducting wire with a favorable local area ratio (LAR)=Ag:Bi-2212. The method begins by texturing a fine powder of Bi-2212: the powder is loaded uniformly into an open-sided silver foil channel, the flaps of foil are folded over the powder filling, and the package is hydraulically com-pressed in a die set to form a textured-powder (TP) bar. XRD analysis of the interior powder in a compressed bar shows a texture of 80% after 200 MPa compression.

36 MATERIALS SCIENCE↗

Dissolution Flowsheet for Skull Oxide Generated during U-Mo Alloy Casting for High Performance Research Reactor Fuel

The Savannah River National Laboratory was requested to develop dissolution flowsheets for high assay low enriched U scrap generated during the fabrication of high performance research reactor fuel. The scrap streams include U-10Mo and U-10Mo-Zr foils, rejected Al-clad fuel plates, and skull oxide from casting molds. Flowsheets for the dissolution of the U-10Mo-Zr foils and Al-clad U-10Mo-Zr mini-plates received from BWX Technologies, Inc were developed and demonstrated in the first phase of this project. In the second phase (this work), the skull oxide from a U-10Mo casting mold was obtained from the Y-12 National Security Complex (Y-12) and small-scale experiments were performed to demonstrate dissolution flowsheets.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

CRADA Number NFE-18-07342 with Lux Semiconductors, LLC (CRADA Final Report)

Lux Semiconductors is a flexible microelectronics startup developing a new class of Systemon-Foil electronics for rapidly emerging Internet-of-Things (IoT) markets. By leveraging its patent pending breakthrough in thin-film recrystallization, Lux is able to produce highly crystalline and flexible silicon substrates on a thin metal backing. This novel platform allows for high-speed silicon circuitry to be patterned directly into the substrate alongside low-cost printed electronics. The System-on-Foil approach has potential to enable the fabrication and integration of all core IoT functionality, including microprocessors, sensors, antennas, interconnects, and power supplies, required to enable highly durable, low profile, flexible electronics.

42 ENGINEERING↗

Adapting LEU-Modified Cintichem Process for Processing Up to 750 Grams of Uranium Targets

Argonne National Laboratory (Argonne) developed a low-enriched uranium (LEU)-modified Cintichem (LMC) process to enable production and purification of fission-produced molybdenum-99 (Mo-99) from LEU foil targets. This separation scheme starts with nitric acid (HNO 3 ) dissolution of irradiated LEU foil targets that yields an approximate final volume of 2 L. The dissolved uranium solution containing fission products, including Mo-99, is then treated by loading the solution on a titania-based recovery column to separate Mo-99 from bulk uranium. After several washing steps, Mo and other fission products are stripped from the titania column using sodium hydroxide (NaOH). The eluate is then acidified using nitric acid and subsequently processed for final purification using the LMC process. Uranium and most fission products are not adsorbed on the titania column but are eluted (i.e., removed using a solvent) during the wash steps; they can be purified and recycled into new uranium targets.

07 ISOTOPE AND RADIATION SOURCES↗

Requirements Description of EvaluateFlux

This report presents the modeling and simulation capabilities of Argonne National Laboratory’s EvaluateFlux code [1] that is used in present reactor analysis activities. These capabilities will then be used to establish the set of EvaluateFlux verification tasks necessary to verify EvaluateFlux for usage on commercial projects. A similar approach was taken for the PERSENT, REBUS and DIF3D software packages. The EvaluateFlux program is a post-processing utility program for DIF3D, specifically DIF3D-VARIANT. As covered in [1], the EvaluateFlux program was built to allow users to obtain flux and power traverses through the domain. Its primary purpose was to facilitate foil analysis by evaluating the flux solution from DIF3D-VARIANT and combining it with foil cross section data. The outputs from EvaluateFlux are contained in four possible output files: FluxAndRegionRR.out, IsotopeMicroRR.out, LabeledRegionRR.out, and IsotopeMacroRR.out. Each file is focused on using the flux evaluate and cross section data in a different manner and all are covered in this verification process.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Hot Forging Options for Thick Castings

Uranium alloyed with 10 wt% molybdenum (U-10Mo) is a monolithic nuclear fuel relevant to the National Nuclear Security Administration’s nonproliferation efforts. Research has been underway to optimize processing techniques for the U-10Mo fuel. This study investigated the use of hot compression or “hot forging” on a thick (~1") cast and homogenized U-10Mo plate before standard hot and cold rolling procedures. After plates were cast and homogenized, six samples were cut and forged at 700°C at a strain rate of either 0.10 s –1 or 0.01 s –1 at six levels of reduction. After forging, all samples underwent hot and cold rolling followed by annealing to achieve a final foil thickness of about 0.0085". Samples were taken at each stage of the casting and thermomechanical processing to assess the microstructural evolution. Chemical composition, microstructure, and uranium carbide morphology are presented and assessed in this study. Upon hot forging, dislocations accumulate along the grain boundaries, which serve as nucleation sites for randomly oriented, strain-free grains during subsequent annealing steps. Hot forging and subsequent annealing produced very heterogeneous grain sizes. However, no molybdenum segregation was observed after forging. No obvious trend was observed between forging conditions (strain rate and reduction percentage) and the microstructure after final thermomechanical processing. Upon hot rolling to 0.04" and annealing (700°C for 45 min), the average grain diameters from OM was 17 ± 2 µm across the six different forged samples. The subsequent cold rolling to 0.0085" and then annealing (700°C for 45 min) resulted in an average of 13 ± 2 µm between the six samples. Thus, the starting, as-forged microstructure did not appear to significantly influence the final microstructure of the cold-rolled foil. These results will help with understanding and expanding hot working capabilities for thicker U-10Mo castings. They also provide useful information on the effects of hot forging and its potential use to minimize defects that can arise during subsequent hot and cold rolling procedures.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Verification of EvaluateFLux Utility Program

The EvaluateFlux program is a post-processing utility program for DIF3D, specifically DIF3D-VARIANT which handles Cartesian and hexagonal geometries. The EvaluateFlux program was developed to allow users to obtain flux and power traverses through the geometry domain, and its initial purpose was to facilitate foil analysis by evaluating the flux solution from DIF3D-VARIANT and combining it with foil cross section data. The EvaluateFlux program can calculate the neutron flux, as well as the reaction rates, at any user provided evaluation point. It does this by identifying the spatial mesh associated with the evaluation point and then evaluates the polynomial based neutron flux moments stored in the NHFLUX file at that point. The output of EvaluateFlux varies depending on the input setup. The maximum output includes the neutron flux and microscopic and macroscopic reaction rates at each evaluation point. The purpose of this work is to verify the outputs of EvaluateFlux. Simple models that have hand calculatable results are first defined and used to verify the EvaluateFlux outputs. More complex cases are then added where a duplicate program of EvaluateFlux that uses PrintTables outputs of the binary files is used to verify the EvaluateFlux outputs. In those complex cases, hand calculations of selected evaluation points were also displayed to confirm the software verification. For all the tests done, the hand calculations agreed well with those calculated by EvaluateFlux. For the larger complex problems, the duplicate program that can process hundreds of evaluation points was able to identify that zero points within some meshes have large errors. This aspect was attributed to the truncation error on the input provided to the duplicate program and is not a concern for the accuracy of the EvaluateFlux software.

97 MATHEMATICS AND COMPUTING↗

Reaction Rate Ratios for Recent Fast Metal Experiments with Large Plutonium Masses

Reaction rate ratios are integral responses that are used within the criticality experiments field because they contain spectral information. While these types of measurements have been utilized for nuclear data validation with historic experiments, few experiments of this type have been utilized for recent experiments, as few exist. This work focuses on measured reaction rate ratios for two nearly bare plutonium critical assemblies with different geometries: one that is cube like (with a Pu mass of 40 kg) and one that is slab like (with a Pu mass of 109 kg). Irradiations were performed with both configurations in which foils were placed near the center of the assembly. Plutonium, highly enriched uranium, depleted uranium, and Au foils were included in the irradiation and counted via high-purity germanium detectors. From these measurements, reaction rate ratios were calculated. Measured and simulated values and uncertainties are presented for the reaction rate ratios. Ratios utilizing the following reactions are given in this work: 197 Au(n, γ), 197 Au(n,2n), 235 U(n,fission), 238 U(n, fission), 238 U(n,2n), 238 U(n,γ), and 239 Pu(n,fission). Uncertainties for the measured reaction rate ratios ranged from 4% to 7%, and the contribution of various parameters to this uncertainty was investigated. The results are compared to historical experiments and should be used for nuclear data validation for future nuclear data library releases. These measurements are part of the EUCLID (Experiments Underpinned by Computational Learning for Improvements in Nuclear Data) project, which utilizes measurement responses in addition to k eff (such as these reaction rate ratios) to help reduce uncertainties in 239 Pu nuclear data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Photon Doppler Velocimetry to Spatially Resolve Plasma Density in a Power Flow Gap

The understanding of power flow plasmas is important as we look towards next generation pulsed power (NGPP) as current losses could prohibit the goals of that facility. Therefore, it is important to have accurate diagnostics of the plasma parameters on the current machines, which can be used to help inform and improve simulations. Having these plasma parameters will help validate models and simulations to provide confidence when they are expanded to conditions relevant to NGPP. One important plasma parameter that can be measured is the electron density, which can be measured by photonic Doppler velocimetry (PDV). A PDV system has several key advantages over other interferometers by measuring relatively low densities (> 1 × 10 15 cm -2 ) with both spatial and temporal resolution. Experiments were performed on the Mykonos pulsed power machine, which is a 1 MA sub scale machine in which recent platforms have been developed to explore current densities relevant to the inner magnetically insulated transmission line (MITL) on the Z machine. Experiments were performed on two different platforms, the thin foil platform and the Mykonos parallel plate platform (MP3). In addition, a combination of both single-point and multi-point measurements were used. The single-point measurements proved to be very promising, providing a clear increase in density at about 70 ns into the current rise on thin foil experiments up to about 5 × 10 17 cm -3 before the probe stopped providing signal. While we did also see returns from multi-point measurements on both platforms, the signals were not as easy to interpret due to strong background effects. However, they do show initial promise for this diagnostic to measure density at several points across a 1 mm gap. These measurements provide insights in how to improve the diagnostic so that it can provide useful information on power flow relevant experiments.

47 OTHER INSTRUMENTATION↗

A Data-driven approach to Core Power distribution reconstruction in a Nuclear Reactor

This report presents the initial development of a data-driven approach for reconstructing the core power distribution in a nuclear reactor (power shape synthesis) using ex-core sensors. Traditional techniques rely on deploying a large number of detectors throughout the reactor core. However, this approach is not feasible for innovative reactor concepts like Advanced Reactors and Microreactors. First, the tight lattice pitch, designed to maximize power density, limits the space available for sensors. Secondly, the harsh operating conditions are not compatible with commercially available detectors. The method proposed in this work integrates high-fidelity modeling with data-driven techniques to accurately reconstruct power distribution across various reactor types, thereby reducing the reliance on in-core sensors. Purdue University Reactor One (PUR-1) was selected as the test case. The CAD model representing the latest configuration of the PUR-1 core was imported into the OpenMC simulation framework, and the model was built. Additionally, the previously developed MCNP6 model was updated. The two models were assessed against the data collected during an experimental campaign conducted in July 2024. Thirty gold foils were placed in three Irradiation Assemblies in PUR-1 core. Using the measured activity of the irradiated foils, the neutron flux at different core locations was estimated.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Verification of the EvaluateFlux Utility Program

The EvaluateFlux program is a post-processing utility program for DIF3D, specifically DIF3D-VARIANT which handles Cartesian and hexagonal geometries. The EvaluateFlux program was developed to allow users to obtain flux and power traverses through the geometry domain, and its initial purpose was to facilitate foil analysis by evaluating the flux solution from DIF3D-VARIANT and combining it with foil cross section data. The EvaluateFlux program can calculate the neutron flux, as well as the reaction rates, at any user provided evaluation point. It does this by identifying the spatial mesh associated with the evaluation point and then evaluates the polynomial based neutron flux moments stored in the NHFLUX file at that point. The output of EvaluateFlux varies depending on the input setup. The maximum output includes the neutron flux and microscopic and macroscopic reaction rates at each evaluation point. The purpose of this work is to verify the outputs of EvaluateFlux. Simple models that have hand calculatable results are first defined and used to verify the EvaluateFlux outputs. More complex cases are then added where a duplicate program of EvaluateFlux that uses PrintTables outputs of the binary files is used to verify the EvaluateFlux outputs. In those complex cases, hand calculations of selected evaluation points were also displayed to confirm the software verification. For all the tests done, the hand calculations agreed well with those calculated by EvaluateFlux. For the larger complex problems, the duplicate program that can process hundreds of evaluation points was able to identify that zero points within some meshes have large errors. This aspect was attributed to the truncation error on the input provided to the duplicate program and is not a concern for the accuracy of the EvaluateFlux software.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Resonant Slow Extraction Simulation using Bmad

Simulations of slow extraction and transport of charged particle beams from synchrotrons requires careful modeling and experimentation. In this paper, we outline how the Bmad modeling software was adapted and developed to run third-integer resonant extraction simulations of beams at Brookhaven National Laboratory’s Booster synchrotron. Further, we show experimental comparisons of the slowly extracted beams transferred to the NASA Space Radiation Laboratory (NSRL) transport line. In this process, beam passes through a stripping foil element at the extraction point, which, along with stripping remaining electrons from the beam ions, acts as a scatterer to modify the phase space, moving to a more Gaussian-like distribution. This modification to the beam helps generate a uniform beam at the beam line’s target location; which is necessary for the variety of experiments performed at the facility. During this work, beam energy loss and multiple scattering by foil routines were built in conjunction with the Bmad code developers and are now integrated into the software.

43 PARTICLE ACCELERATORS↗

Preliminary Look at the LBEG & MPEG Beam Transmissions between HPSim and Operation Data

This report summarizes recent work on estimating the transmission of LANSCE H- beams from the end of the present DTL to both the PSR stripper foil (LBEG) and WNR target 4 (MPEG). The LBEG beam might be considered a more typical LINAC beam and lends itself to continuous monitoring of transmission through the various stages of the accelerator. For the MPEG, however, the widely-spaced micropulses and lack of the requisite sensitivity current monitors throughout the accelerator make these measurements extremely difficult and more uncertain. Therefore, to assist in estimating the MPEG beam transmission, beam-dynamics simulations using HPSim were employed. These beam transmission estimates from the end of the Drift Tube Linac (DTL) to Target 4 (MPEG) and the PSR stripper foil (LBEG) are vital to determine the charge requirements for LAMP’s front end. In this technote, we demonstrate three major efforts in determining the transmission: (1) Convert the WNR beamline lattice from TRANSPORT to HPSim for use in the simulation; (2) Simulate the optimization process in the Central Control Room (CCR) that brings down the losses by up to a factor of 4000 between the end of the initial physics-based tuneup phase and production beam operation; (3) Analyze operational data to deduce measured transmissions. Table 1 shows the estimated losses with HPSim and operational analysis. Finally, a better measurement and other improvements to refine the results are also proposed.

43 PARTICLE ACCELERATORS↗