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At least 451 records · Page 25

Cooperative spin coupling in PrFeO3

A transition from crystal-field to spin wave excitations has been experimentally observed in PrFeO3 using inelastic neutron scattering. Theoretical modeling with density functional theory and the mean field random phase approximation successfully reproduces the experimental observations and allows extraction of the values for the various exchange interactions. The study reveals that the strong coupling between the two magnetic sublattices of Pr and Fe is the fundamental mechanism underlying the low-temperature Pr magnetism. This coupling, analogous to the Dicke cooperative interaction between atoms and photons, polarizes the Pr moments, enhances the Pr-Pr interactions, and contributes to the formation of a quasidoublet, leading to the transition from single-particle to collective excitations within the Pr sublattice. Furthermore, this coupling induces spin reorientation on the Fe sublattice. The manipulation of magnetic moments via spin waves is achievable through the coupling between different magnetic sublattices in a bulk material containing multiple magnetic ions.

Garlea, Vasile [ORNL] (ORCID:0000000253227271)↗

A Method for Assessing Effectiveness and Technical Capabilities Required for Integrated Deterrence (NSLP-Final Report-Draft2022)

The United States faces an ever-increasingly multi-polar security environment dominated by great power competition with China and a lingering Russian threat as well as from would-be regional hegemons led by ambitions from Iran and North Korea. Our adversaries are pursuing and expanding the strategic means by-which they have an asymmetric offset (e.g., cyber, space, and other modes below the level of armed conflict). To combat and deter against the widening range of hostile actions, the U.S. must have additional capabilities with-which to deter. All of which drives us towards a more thoughtful integrated approach to deterrence, attempting to best align deterrent tools with the adversary actions in order to maximize the credibility of our deterrent. Such an approach complicates our deterrence strategy and demands a methodology to assess whether the U.S. has the deterrent tools necessary to deter the adversarial actions most costly to the U.S. To address this complexity, we create a framework to comprehensively and systematically assess our deterrent tools as qualitatively measured against the adversarial actions we wish to deter. Deterrence is ultimately an operation in the cognitive domain and at the heart of the framework presented here is the fundamental deterrence calculus which we use as the defining measure of whether a tool will credibly deter a given action. We describe the eight levers of the deterrence calculus and distill these levers to four products that are used to qualitatively assess the overall effectiveness of deterrence tools against adversarial actions. Credibility is determined by two principal variables: the technical credibility of the deterrent tool, and the principle of proportionality. Technical credibility of realized deterrence products is assessed through development of key mission requirements and hardware (e.g., components) that will impose costs, deny benefits, or encourage restraint. The principle of proportionality qualitatively asserts that for a deterrent tool to be cognitively credible, the costs imposed against, or benefits denied by, an action are commensurate to the magnitude of costs received from the adversarial action. By basing this framework on these two fundamentals, it is possible to compare deterrent tools in a systematic approach across the broad spectrum of hostile actions.

42 ENGINEERING↗

Effect of sucrose on the oxidation-reduction conditions and retention of rhenium during vitrification of low-activity waste

Technetium speciation and solubility during nuclear waste vitrification are affected by oxygen partial pressure in the melt. Thus, reducing agents such as sucrose, which are routinely added to nuclear waste feeds to repress foaming, can significantly affect the volatilization of Tc and increase its retention in glass. Using Re as a surrogate for Tc, we measured the effect of sucrose addition to two low-activity waste melter feeds on the Re retention, oxygen partial pressure, and iron redox as functions of temperature. As expected, Re retention in glass increased as the sucrose content increased. Furthermore, this is attributed to sucrose reaction with nitrates and nitrites in the feed. Destruction of nitrates and nitrites reduces the salt phase fraction and thus likely promotes Re diffusion into the glass-forming melt. In agreement with available literature, we discuss that a modest increase in the sucrose content (compared to current practice) can significantly improve the Tc retention without reducing Fe 2+ to metal.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

The Dynamics of Ions on Phased Radio-frequency Carpets in High Pressure Gases and Application for Barium Tagging in Xenon Gas Time Projection Chambers

Radio-frequency (RF) carpets with ultra-fine pitches are examined for ion transport in gases at atmospheric pressures and above. We develop new analytic and computational methods for modeling RF ion transport at densities where dynamics are strongly influenced by buffer gas collisions. An analytic description of levitating and sweeping forces from phased arrays is obtained, then thermodynamic and kinetic principles are used to calculate ion loss rates in the presence of collisions. This methodology is validated against detailed microscopic SIMION simulations. We then explore a parameter space of special interest for neutrinoless double beta decay experiments: transport of barium ions in xenon at pressures from 1 to 10 bar. Our computations account for molecular ion formation and pressure dependent mobility as well as finite temperature effects. We discuss the challenges associated with achieving suitable operating conditions, which lie beyond the capabilities of existing devices, using presently available or near-future manufacturing techniques.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Soft-hard framework with exact four-momentum conservation for small systems

A new framework, called x-scape, for the combined study of both hard and soft transverse momentum sectors in high-energy proton-proton (𝑝−𝑝) and proton-nucleus (𝑝−𝐴) collisions is set up. A dynamical initial state is set up using the 3d-Glauber model with transverse locations of hotspots within each incoming nucleon. A hard scattering that emanates from two colliding hotspots is carried out using the Pythia generator. Initial state radiation from the incoming hard partons is carried out in a new module called I-matter, which includes the longitudinal location of initial splits. The energy-momentum of both the initial hard partons and their associated beam remnants is removed from the hot spots, depleting the energy-momentum available for the formation of the bulk medium. Outgoing showers are simulated using the matter generator, and results are presented for both cases, allowing for and not allowing for energy loss. First comparisons between this hard-soft model and single inclusive hadron and jet data from 𝑝−𝑝 and minimum bias 𝑝−Pb collisions are presented. Single hadron spectra in 𝑝−𝑝 are used to carry out a limited (in number of parameters) Bayesian calibration of the model. Fair comparisons with data are indicative of the utility of this new framework. Theoretical studies of the correlation between jet 𝑝 𝑇 and event activity at mid and forward rapidity are carried out.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Background subtraction in inelastic scattering measurements using machine learning

Identifying, isolating, and subtracting background from the signal of interest is vital for nuclear physics experiments. These backgrounds introduce unwanted uncertainties that must be accounted for properly to extract accurate results from the signals. In nuclear reaction measurements, the typical contaminants are carbon and oxygen, contributing to background signals, and complicating the measurement of the light ejectiles. For instance, in the inelastic scattering measurement of a 20.9-MeV proton beam on 96 Mo, the 96 Mo target was contaminated with carbon and oxygen. Here, we used random forest, a machine learning algorithm commonly used for classification and regression tasks, to separate the inelastic scattering on the carbon and oxygen contaminants from the data of interest resulting from 96 Mo(p, p').

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

High-Density Implosions on OMEGA and the National Ignition Facility (NIF) (Final FY23 report for the subcontract B656484 (formerly B640112))

This final FY23 report for the subcontract B656484 (formerly B640112) “High-Density Implosions on Omega and the National Ignition Facility (NIF)” summarizes MIT’s support of LLNL experiments at OMEGA and the NIF with nuclear diagnostics, platforms and analysis, and of training PhD students. Overall, the tasks identified as Statement-Of-Work (SOW) items for FY23 were accomplished.

42 ENGINEERING↗

Using personal monitoring data to derive organ doses for medical radiation workers in the Million Person Study—considerations regarding NCRP Commentary no. 30

The study of low dose and low-dose rate exposure is of central importance in understanding the possible range of health effects from prolonged exposures to radiation. The One Million Person Study of Radiation Workers and Veterans (MPS) of low-dose health effects was designed to evaluate radiation risks among healthy American workers and veterans. The MPS is evaluating low-dose and dose-rate effects, intakes of radioactive elements, cancer and non-cancer outcomes, as well as differences in risks between women and men. Medical radiation workers make up a large group of individuals occupationally exposed to low doses of radiation from external x-ray/gamma exposures. For the MPS, about 100 000 United States medical radiation workers have been selected for study. The approach to the complex dosimetry circumstances for such workers over three to four decades of occupation were initially and broadly described in National Council on Radiation Protection and Measurements (NCRP) Report No. 178. NCRP Commentary No. 30 provides more detail and describes an optimum approach for using personal monitoring data to estimate lung and other organ doses applicable to the cohort and provides specific precautions/considerations applicable to the dosimetry of medical radiation worker organ doses for use in epidemiologic studies. The use of protective aprons creates dosimetric complexity. It is recommended that dose values from dosimeters worn over a protective apron be reduced by a factor of 20 for estimating mean organ doses to tissues located in the torso and that 15% of the marrow should be assumed to remain unshielded for exposure scenarios when aprons are worn. Conversion coefficients relating personal dose equivalent, H p (10) in mSv, to mean absorbed doses to organs and tissues, D T in mGy, for females and males for six exposure scenarios have been determined and presented for use in the MPS. This Memorandum summarises several key points in NCRP Commentary No. 30.

Environmental Sciences & Ecology↗

Reconstructed lung doses for the million person study cohort of 26,650 Tennessee Eastman corporation workers employed between 1942 and 1947

Abstract Tennessee Eastman Corporation workers were exposed to uranium dust resulting in high-linear energy transfer (LET) irradiation to lung tissue. In this work, radiation lung doses were reconstructed for 26 650 men and women working at the plant between 1942 and 1947. Site air monitoring data of uranium concentrations and payroll records were used to determine the daily inhaled activities and annualized lung doses. Variations in the activity median aerodynamic diameter of the uranium dust, the solubility of particulate matter in the lungs and the sex-specific breathing rate were investigated as part of a sensitivity analysis. Male and female mean lung doses of 18.9 and 32.7 mGy, respectively, from high-LET alpha irradiation, and there was general agreement with evaluations from previously published epidemiological studies. Annual lung dose estimates and sensitivity analysis for the 26 650 workers in the TEC cohort have been archived on the United States Department of Energy Comprehensive Epidemiologic Data Resource.

61 RADIATION PROTECTION AND DOSIMETRY↗

DUAL-PARTICLE DOSEMETER BASED ON ORGANIC SCINTILLATOR

Abstract Traditionally available handheld dosemeters are generally sensitive to only one type of radiation: neutrons or photons. Some dosemeters also rely on very specific attenuation correlations between response and dose, are not scalable in size and multiple dosemeters are required to characterise mixed-particle fields. The research presented here serves as a proof-of-concept for a method to simultaneously measure dose rates from neutrons and photons using a particle discriminating organic scintillation detector without the need for spectral deconvolution. The method was compared with traditional instruments and to simulation. Isotopic photon dose rates measured with this method were within 4% of simulated truth, whereas fission spectrum neutron dose rates were measured within 21%. Measurements of dose rates from both particles agree with simulated truth better than traditional instruments. This new method allows for measurement of dose equivalent from both neutrons and photons with a single instrument and no reliance on spectral deconvolution.

Miller, C. A.↗

URINARY EXCRETION OF PLUTONIUM IN MAYAK WORKERS DURING AND AFTER CA-DTPA ADMINISTRATION

Chelation therapy is sometimes used after potential exposures to plutonium to increase urinary excretion of the radionuclide to improve the accuracy of bioassay measurements. The purpose of this report is to describe the enhancement of urinary excretion of plutonium during and after the administration of the trisodium salt of calcium diethylenetriaminepentaacetate (Ca-DTPA) daily for 3 d to a group of male and female plutonium workers from the Mayak Production Association in Ozyorsk, Russia. One-hundred and two cases (18 females and 84 males) were selected where urinary contents of plutonium, prior to chelation, exceeded the detection threshold. Daily urine collections were obtained during the 3 d of Ca-DTPA treatments. In addition, 58 of these cases had urine bioassays at 1–45 d after chelation. The daily enhancement over baseline values excretion of plutonium was found to be 50.4×/1.4 (geometric mean and geometric standard deviation); 58.9×/1.2; 72.9×/1.4 in the first, second and third days of Ca-DTPA administration. The mean enhancement for the 3-d period was 60.1×/1.7. The rate of plutonium excretion from 1 to 45 d after chelation decreased with a half-period of 3.9 d and the chelation enhancement factor (Кenh-i) is described by the function Кenh-i = (0.79 ± 0.24) + (42.9 ± 1.2) × e-(0.18 ± 0.01) × day.

Environmental Sciences & Ecology↗

Electron paramagnetic resonance dose measurements in teeth of tissue donors to the United States Transuranium and Uranium Registries

Abstract The United States Transuranium and Uranium Registries (USTUR) is a research program that studies actinide biokinetics in occupationally exposed individuals with known intakes of these elements. Electron paramagnetic resonance (EPR) in tooth enamel was applied to reconstruct external doses of nine USTUR registrants. Only in two cases there is a reasonable agreement between the EPR-measured dose and the worksite external dose record. For two registrants, high EPR doses can be explained by possible cancer radiotherapy. For the remaining five cases, EPR doses significantly exceed official occupational doses with no plausible explanation for the observed discrepancy. More EPR dose measurements need to be done to explain this anomaly.

Environmental Sciences & Ecology↗