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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

INL Alpha Radiation Background Study

During a radiological emergency, swift determination of the extent and intensity of the radiological materials that have been released to the environment are important for decision makers to correctly assess the hazards and recommend protective actions. In a radiological emergency, natural background counts need to be subtracted from the total activity for the actual amount of activity present to be assessed. This study provides documented survey results of the soils in and around the INL using instrumentation utilized by field monitoring teams that support the INL. Over three hundred alpha background counts were taken. The average alpha background count rate on portable instruments in use by field monitoring teams is 5 counts per minute and the decision level for activity that should be considered as having activity greater than background is 10 counts per minute. It was also shown that rain or snow can increase the background and its effects are difficult to quantify.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2024

Demonstrating the β-Ga 2 O 3 Schottky diodes for alpha radiation detection

Schottky barrier diodes were fabricated on (001) monoclinic β-Ga 2 O 3 wafers with low doped epitaxial layers of 7.0 × 10 15 cm −3 . Circular Ni Schottky contacts with area 2 mm 2 were deposited by electron beam evaporation. Devices were characterized electrically by performing forward and reverse current-voltage sweeps with a range of −100 V–2 V, as well as capacitance-voltage sweeps to −30 V. The breakdown voltage was also determined to be −180 V for the devices. Experiments measuring the electrical response from incident X-ray radiation was performed. A response time to X-ray radiation of less than 1 s was recorded and a decay time of approximately 2 s after removing X-ray source, which primarily attribute to X-ray switching on and off time. Energy spectra of alpha particles from a 0.9 μCi 241 Am button source was collected at various voltage biases using devices with the lowest measured leakage current while reverse biased. The total count rate was observed to increase linearly with increasing device bias. In conclusion, the peak channel number was observed to increase with increasing bias with the best resolution of 9.5% at −100 V reverse bias.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Simulation of radiation damage via alpha decay in BFS:PC grouts using 4 He 2+ ion acceleration

The impact of alpha radiation on cements used to encapsulate intermediate-level waste (ILW) is not well understood. ILW wastes can contain high levels of alpha-emitting radionuclides, meaning that the grouts used to encapsulate them are exposed to significant ionising radiation. Thus, a damaged region could develop in the grout adjacent to the alpha-emitting species. This work attempted to recreate this behaviour through nonradioactive 4 He 2+ ion-accelerator experiments, which have not previously been applied to common encapsulation grouts. The influence of this irradiation on a slag-Portland cement was investigated at different ages via transmission electron microscopy energy-dispersive x-ray spectroscopy (TEM-EDX) and supporting techniques, to assess whether 4 He 2+ irradiation caused textural or chemical zonation. No significant changes in hydrate phases or textures were observed, other than minor variations associated with carbonation. This paper provides a proof of concept for using ion acceleration techniques on cements and furthers knowledge on their radiation response.

36 MATERIALS SCIENCE↗
DOE OSTI2024

INL Alpha Background Radiation Study

Radiological emergencies that result in the dispersion of radioactive materials to the environment require the deployment of field monitoring teams to determine the quantity and location of the dispersed radioactive material. This information is utilized by the emergency operations center to aid in determining the appropriate protective action recommendations. The background alpha emission rates from normal environmental surfaces of soil, concrete and asphalt as measured by portable instrumentation used by field monitoring teams are not well documented. Idaho National Laboratory conducted a study of the alpha radiation background levels of the environmental surfaces in eastern Idaho to determine the normal background rates. Results for normal dry surfaces and those wetted by precipitation were measured and reported.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2023

Composition for detecting alpha particle radiation and methods of use

A capsule composition comprising: (a) a polyester shell having a thickness of no more than 20 microns, and (b) a solution containing a visual and/or olfactory indicator, wherein the solution is encapsulated by the polyester shell. Also described herein is a method for detecting alpha particle radiation, in which: (i) the capsule composition is placed in contact with an esterase in a location where the presence of alpha particle radiation is being determined; (ii) waiting a period of time for the esterase to degrade the polyester shells, wherein the period of time is insufficient for the esterase to cause leakage of the solution in the absence of alpha particle radiation but is sufficient for alpha particle radiation, if present, to cause leakage from the capsule composition; and (iii) observing whether leakage has occurred at the end of the period of time to determine whether alpha particle radiation is present.

McKnight, Timothy E.↗
DOE OSTI2019

FGR 13 Dose Conversion Factor Files

The purpose of this document is to discuss the construction of two MELCOR Accident Consequence Code System (MACCS) dose conversion factor (DCF) files in some detail, an older file created in 2007 named FGR13DCF.inp and a newer file created in 2018 called FGR13GyEquiv_RevAinp. Very briefly, the difference between the two files is that the older file follows the standard conventions of assigning a radiation weighting factor of 20 for alpha radiation for all tissues and organs; whereas, the newer file complies with the Federal Guidance Report (FGR) 13 health effects modeling and uses modified radiation weighting factors (referred to as relative biological effectiveness (RBE) factors) for alpha radiation of 10 for breast and of 1 for red bone marrow. During an intermediate period, a file called FGR13GyEquiv.inp was created and used for the State-of-the-Art Reactor Consequence Analysis (SOARCA) calculations. This file was not released to the MACCS user community, but it is also discussed briefly in this document.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2019

FGR 13 Dose Conversion Factor Files

The purpose of this document is to discuss the construction of two MACCS dose conversion factor (DCF) files in some detail, an older file created in 2007 named FGR13DCF.inp and a newer file created in 2018 called FGR13GyEquiv_RevA.inp. Very briefly, the difference between the two files is that the older file follows the standard conventions of assigning a radiation weighting factor of 20 for alpha radiation for all tissues and organs; whereas, the newer file complies with the FGR 13 health effects modeling and uses modified radiation weighting factors (referred to as relative biological effectiveness (RBE) factors) for alpha radiation of 10 for breast and of 1 for red bone marrow. During an intermediate period the creation of these two DCF files, a file called FGR13GyEquiv was created and used for the SOARCA calculations. This file was not released to the MACCS user community, but it is also discussed briefly in this document. DCF files are used by MACCS to convert air and ground radionuclide concentrations to doses to an organ or to the whole body. The MACCS calculation considers duration and shielding factor for each exposure pathway including cloudshine, groundshine, inhalation, and ingestion. Dose coefficients for cloudshine and groundshine are expressed as dose rates; dose coefficients for inhalation and ingestion are expressed as committed doses. In this document, dose coefficients (newer ICRP terminology) is used to describe the values contained in dose conversion factor (older ICRP terminology) files.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2020

Engineering of Lead Selenide Quantum Dot Based Devices and Core/Shell Heterostructures

Near infrared (NIR) emitting colloidal quantum dots (QDs) such as PbSe are interesting materials for implementation in various optoelectronic devices such as solar cells, photodetectors, and radiation detectors. Material properties like size tunable emission wavelengths, facile solution processability, the possibility of carrier multiplication and Auger assisted up-conversion, and high Z number provide PbSe QDs with unique advantages over many currently available commercial materials used in these devices. In this dissertation, after an introduction to QDs in general, we first focus on synthesis of PbSe-based heterostructured QDs for study via optical spectroscopy. PbSe/CdSe QDs synthesized via cation exchange reaction were used as seeds to study the proper conditions for further CdSe or CdS shell growth. Optical spectroscopy studies show that growth of thicker CdSe shells leads to tunable visible emission, while growth of thick CdS shells can greatly increase the photoluminescence quantum yield (PLQY) observed from the intermediate CdSe shell. NIR PL lifetimes can be greatly enhanced by the growth of CdS shells, due to strong delocalization of the hole wavefunction within the PbSe core, while the electron is delocalized throughout the QD including in the CdS shell, resulting in radiative lifetimes in the tens of microseconds. Two pulse delay measurements show that Auger assisted up conversion is also taking place in these engineered QD dot heterostructures. In the sections that follow, we look at QD devices, first with a focus on novel devices fabricated from PbSe QDs, using an amine synthesis method that allows for facile in-solution ligand exchange. QD film mobilities are measured for PbSe QDs capped with various short ionic ligands. Carrier densities in PbSe QD films are calculated from C-V measurements, showing for the first time that carrier densities can be modulated by simply changing the capping ligand. vii Radiation detectors utilizing PbSe QDs capped with KI and NH4I ligands show tangible response to incident alpha radiation. Current output response to alpha radiation is dependent on strength of radiation source and amount of bias voltage applied. In the final section a critical review of hybrid layered 2D-QD photodetectors is presented. In a typical example, PbSe and PbS QDs act as the absorbing layer in phototransistor devices which utilize layered 2D materials such as graphene and transition metal dichalcogenides as transport layers. Resulting devices display high gains and improved directivities compared to QD only and 2D only devices.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Laser-Based Defect Reduction in Wide Bandgap Semiconductors Used in Radiation-Voltaics Devices: Radiation Hardening and Annealing

The primary goal of this study was to determine whether laser illumination at sub-bandgap wavelengths of semiconductors (especially those used for radiation voltaics) could anneal defects generated during radiation exposure (Beta and Alpha radiation). Defect annealing was probed on a set of Silicon Carbide (SiC) samples using in situ monitoring of the photoluminescence (PL) emissions from UV- to near infrared spectra under UV excitation (broadband or laser at λ L = 351 nm). No significant effect was found using 1064 nm wavelength light as the annealing source up to the laser damage threshold fluence of the nanosecond pulsed laser (10 Hz rep-rate). Additional research is needed to fully explore effects from laser annealing beyond the scope of this feasibility testing.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Nuclear Data Sheets for A=194

Experimental nuclear structure and decay data are evaluated for all of 14 known nuclides of mass 194 (Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, At, Rn). Detailed evaluated spectroscopic information is presented for each reaction and decay experiment, and by combining all the available data, recommended values are provided for energies, spins and parities and half-lives of levels, together with energies, branching ratios and multipolarities of gamma radiations from the levels, and characteristics of beta and alpha radiations in radioactive decays. No excited states have yet been identified in 194 Ta, 194 W, and 194 Rn. Only limited spectroscopic data are available for 194 Re, with a 45–μs isomer identified, but its absolute energy yet to be determined. Only two levels at unknown absolute energies are reported for 194 At, both of which are isomeric but neither can be unambiguously identified as the ground state. Data are scarce for 194 Os, 194 Bi and 194 Po, while 194 Pt, 194 Au, 194 Hg, 194 Tl and 194 Pb are well studied through decays and reactions. For 194 Ir, although a major (n, γ), E=thermal study and two particle-transfer studies provide large amounts of spectral data, still several problematic issues are found in the assignment of multipolarities for the secondary gamma transitions in the (n, γ) study by 2008Ba25, 1998Ba85 and 1998Ba42, all from the same group. Some issues have been resolved by the evaluators, but we suggest that further experimental work is needed on 194 Ir structure to resolve standing issues, and verify the conclusions made by 2008Ba25. Furthermore, our attempt to contact the prime authors of the 2008Ba25 paper was not successful. The present work supersedes all the earlier evaluations of A=194 nuclides by 2006Si17, 1996Br26, 1989Si01 and 1972Au11.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Direct metal contacts printing on 4H-SiC for alpha detectors and inhomogeneous Schottky barriers

Electrical characterization of several 4H-SiC Schottky diodes with Aerosol-Jet printed gold (Au), silver (Ag), and platinum (Pt) contacts was performed using forward and reverse current–voltage (IV) measurements. From these measurements, device parameters such as Schottky barrier height and ideality factor were determined; however, many of the devices exhibited nonideal behavior and inferior performance characterized by ideality factors significantly greater than one, disproportionate low voltage leakage current and low barrier heights. Forward current–voltage (FIV) characteristics were fitted to an inhomogeneous barrier height theory to explain the abnormal behavior exhibited by the printed devices. Here, transmission electron microscopy (TEM) of the device cross-sections was performed to investigate the printed metal and semiconductor epitaxial layer interface, which revealed the imperfections in the metal–semiconductor contact. Despite these irregularities, alpha radiation detection capability of these devices was still achieved with an energy resolution of 1.89% at 5.486 MeV, and the best achievable resolution at 0.51% with no energy degradation of 5.486 MeV.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Curium(iii) radiation-induced reaction kinetics in aqueous media

Insight into the effects of radiolytic processes on the actinides is critical for advancing our understanding of their solution chemistry because the behaviour of these elements cannot be easily separated from the influence of their inherent radiation field. However, minimal information exists on the radiation-induced redox behaviour of curium (Cm), a key trivalent transuranic element present in used nuclear fuel and frequently used as an alpha radiation source. Here we present a kinetic study on the aqueous redox reactions of Cm(III) with radicals generated through the radiolysis of aqueous media. In particular, we probe reaction kinetics in nitric acid solutions that are used as the aqueous phase component of used nuclear fuel reprocessing solvent systems. Second-order rate coefficients (k) were measured for the reaction of Cm(III) with the hydrated electron (e aq - , k = (1.25 ± 0.03) × 10 10 M -1 s -1 ), hydrogen atom (H˙, k = (5.16 ± 0.37) × 10 8 M -1 s -1 ), hydroxyl radical (˙OH, k = (1.69 ± 0.24) × 10 9 M -1 s -1 ), and nitrate radical (NO 3 ˙, k = (4.83 ± 0.09) × 10 7 M -1 s -1 ). Furthermore, the first-ever Cm(II) absorption spectrum (300–700 nm) is also reported. These kinetic data dispel the status quo notion of Cm(III) possessing little to no redox chemistry in aqueous solution, and suggest that the resulting Cm(II) and Cm(IV) transients could exist in irradiated aqueous solutions and be available to undergo subsequent redox chemistry with other solutes.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Scintillation light detection in polycrystalline diamond using single photon detectors

Here, this study investigates the scintillation properties of polycrystalline diamond for particle detection applications, particularly in neutron and alpha radiation environments. Polycrystalline diamonds provide a cost-effective alternative to monocrystalline diamonds while retaining essential detection properties. Photoluminescence measurements were performed to analyze emission spectra, revealing distinct characteristics based on impurity content and crystallinity. Scintillation responses were assessed using Silicon Photomultipliers (SiPMs), demonstrating the capability of polycrystalline diamond powders to respond to alpha irradiation, albeit with reduced resolution compared to traditional scintillators. A prototype neutron detector was developed by combining diamond powder with neutron-sensitive 6 LiF, and its performance was evaluated through experimental testing and Geant4 simulations. The findings indicate that polycrystalline diamond-based detectors can achieve significant detection efficiency while remaining insensitive to gamma radiation, offering potential for portable neutron detection applications.

47 OTHER INSTRUMENTATION↗