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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Time features of delayed neutrons and partial emissive-fission cross sections for the neutron-induced fission of {sup 232}Th nuclei in the energy range 3.2-17.9 MeV

The energy dependence of the relative abundances of delayed neutrons and the energy dependence of the half-lives of their precursors in the neutron-induced fission of {sup 232}Th nuclei in the energy range 3.2-17.9 MeV were measured for the first time. A systematics of the time features of delayed neutrons is developed. This systematics makes it possible to estimate the half-life of delayed-neutron precursors as a function of the nucleonic composition of fissile nuclei by using a single parameter set for all nuclides. The energy dependence of the partial cross sections for emissive fission in the reaction {sup 232}Th(n, f) was analyzed on the basis of data obtained for the relative abundances of delayed neutrons and the aforementioned half-lives and on the basis of the created systematics of the time features of delayed neutrons. It was shown experimentally for the first time that the decrease in the cross section after the reaction threshold in the fission of {sup 232}Th nuclei (it has a pronounced first-chance plateau) is not an exclusion among the already studied uranium, plutonium, and curium isotopes and complies with theoretical predictions obtained for the respective nuclei with allowance for shell, superfluid, and collective effects in the nuclear-level density and with allowance for preequilibrium neutron emission

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Systematics of the mean energy and the mean multiplicity of prompt neutrons originating from {sup 232}Th fission

The cross section for the neutron-induced fission of {sup 232}Th target nuclei, {sigma}{sub f} (E{sub n}), was described within statistical theory. The spectra of the mean multiplicity, v-bar (E{sub n}), and the mean energy, E-bar(E{sub n}), of secondary neutrons accompanying {sup 232}Th fission induced by neutrons of energy extending up to E{sub n} = 20 MeV were analyzed on the basis of the chance structure of the cross section.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Reduced probabilities for E2 transitions between excited collective states of triaxial even–even nuclei

Reduced probabilities for intra- and interband E2 transitions in excited collective states of even–even lanthanide and actinide nuclei are analyzed on the basis of a model that admits an arbitrary triaxiality. They are studied in detail in the energy spectra of {sup 154}Sm, {sup 156}Gd, {sup 158}Dy, {sup 162,164}Er, {sup 230,232}Th, and {sup 232,234,236,238}U even–even nuclei. Theoretical and experimental values of the reduced probabilities for the respective E2 transitions are compared. This comparison shows good agreement for all states, including high-spin ones. The ratios of the reduced probabilities for the E2 transitions in question are compared with results following from the Alaga rules. These comparisons make it possible to assess the sensitivity of the probabilities being considered to the presence of quadrupole deformations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Radiological Impact Associated to Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) from Coal-Fired Power Plants Emissions - 13436

Certain materials used and produced in a wide range of non-nuclear industries contain enhanced activity concentrations of natural radionuclides. In particular, electricity production from coal is one of the major sources of increased human exposure to naturally occurring radioactive materials. A methodology was developed to assess the radiological impact due to natural radiation background. The developed research was applied to a specific case study, the Sines coal-fired power plant, located in the southwest coastline of Portugal. Gamma radiation measurements were carried out with two different instruments: a sodium iodide scintillation detector counter (SPP2 NF, Saphymo) and a gamma ray spectrometer with energy discrimination (Falcon 5000, Canberra). Two circular survey areas were defined within 20 km of the power plant. Forty relevant measurements points were established within the sampling area: 15 urban and 25 suburban locations. Additionally, ten more measurements points were defined, mostly at the 20-km area. The registered gamma radiation varies from 20 to 98.33 counts per seconds (c.p.s.) corresponding to an external gamma exposure rate variable between 87.70 and 431.19 nGy/h. The highest values were measured at locations near the power plant and those located in an area within the 6 and 20 km from the stacks. In situ gamma radiation measurements with energy discrimination identified natural emitting nuclides as well as their decay products (Pb-212, Pb-2142, Ra-226, Th-232, Ac-228, Th-234, Pa-234, U- 235, etc.). According to the results, an influence from the stacks emissions has been identified both qualitatively and quantitatively. The developed methodology accomplished the lack of data in what concerns to radiation rate in the vicinity of Sines coal-fired power plant and consequently the resulting exposure to the nearby population. (authors)

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Development of an Assessment Method for Radiation Exposure from NORM in Construction Materials - 19032

Once radiological impact is usually considered to be related to nuclear energy accidents and atomic bombs, most of the research on radiation protection has been focused on artificial radionuclides and radioactive waste. Less attention had been given to radiation exposure due to the presence of naturally occurring radioactive materials in raw materials usually considered as not radioactive and used in manufacturing of many building materials. At national level, radiological data from building materials is not available as the control of building materials regarding the content of naturally occurring radionuclides is addressed for the first time in the EU Directive 2013/59/EURATOM. At international level the research developed is largely incomplete: data on the activity concentration measurements of Ra-226, Th-232 and K-40 in building materials used in the construction industry in the EU is non-statistically representative. The data collected are not enough to have an idea of the European situation, but they confirm high concentration of Ra-226, Th-232 and K-40, in some cases. Moreover, most of the research studies carried out in the EU are based on the assessment of the activity concentration index, which was derived for practical monitoring purposes to identify whether a dose criterion is met; to be used only as a screening tool for identifying materials which might be of concern. The dose criterion considers only effective dose due to γ-radiation, but population at home is also exposed to Rn-222 (and Rn-220) from soil, water and building material itself, sometimes to β radiation from superficial materials, and even to Cs-137 from some types of wood. The indoors exposure can be actually much higher than the value assessed with the dose criterion method. Also, in most cases toxic and radioactive components are inseparably. Therefore, all technical questions related to the toxic part of these materials should be addressed: an integrated approach is needed to assess the impacts of using these materials (new materials, recyclates and by-products). Until recently, radiation from natural sources seemed both unremarkable and unalterable - a background phenomenon. It is now known that doses from natural sources and in particular, decay products of radon can be remarkably high within houses in some areas. Therefore, concerning exposure to natural radiation sources, special provisions have been laid down in the EU Directive 1996/28 EURATOM. Still, the radiological evaluation of building materials was not mandatory in this Directive. The most recent EU Directive 2013/59/EURATOM brings some changes concerning the exposure to natural occurring radioactive materials but the previous screening method was kept. An effective dose of 1 mSv/year was set, as a basis for the exposure to radionuclides of natural origin (except for radon). This work seeks to develop an integrated radiological and chemical-mineralogical assessment methodology for realistic exposure scenarios concerning different types of raw materials, by-products and recyclates and used as building materials. The methodology includes the characterization of selected materials accounting for radiological exposure - calculation of effective dose; toxicity assessment - determination of chemical composition and leaching tests, study of changes in the microstructure and consequently in the radon emanation coefficient. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Port Hope Area Initiative: Information Management for A Very Large Radiation Survey - 19567

The Port Hope Area Initiative (PHAI) represents the Government of Canada's commitment to the cleanup and safe, local, long-term management of historic low-level radioactive waste (LLRW) in two Southern Ontario municipalities - Port Hope. The PHAI is based on community-recommended solutions for the cleanup and safe long-term management of approximately 1.7 million cubic meters of LLRW. It is currently one of Canada's largest environmental remediation projects at a cost of over one billion dollars. The PHAI is being implemented by Canadian Nuclear Laboratories (CNL) on behalf of Atomic Energy of Canada Limited, a federal Crown corporation. The waste is the result of radium and uranium processing in Port Hope by the former federal crown corporation Eldorado Nuclear Limited between 1933 and 1988. The waste has been distributed in the Municipality of Port Hope through placement of contaminated materials (e.g. fill), reuse of contaminated objects (e.g. tailings use in concrete, steel posts, structural wood) and air-borne deposition. Signature contaminants of potential concern (COPCs) are Ra-226, Th-230, uranium and arsenic; however, there are an additional 17 COPCs that also need to be considered. A very large amount of information has been collected during the survey and effectively managing and analyzing this information is critical to the success for the property owners, CNL's implementation of the PHAI, and Arcadis. Data collected during the survey includes information pertaining to long-term interior radon gas measurements, interior gamma radiation surveys, contaminated objects and surfaces, exterior gamma radiation and subsurface investigations. exterior gamma radiation surveys. The information management (IM) is structured with SharePoint as a focal point supported by an EQuIS database, mobile data collection and GIS support. The IM process for this project is being advanced using recent software developments to assist with internal activities (e.g. QA) and interactions with CNL including notifications and scheduling and status of property completion. Different applications have been developed to help automate, visualize, actively track, and QA different processes using recent software developments by Microsoft. We have used SharePoint to organize and track our data. Power BI has been used to actively track and visualize our data from Interior gamma surveying to exterior drilling. The creation of dynamic/advanced visualizations in Power BI gathers data daily from our multiple sources and analyzes it for anomalous data and trends. Microsoft Flow syncs with Power BI and has been implemented to automate many processes including the QA of surveys and soil results for identification of LLRW. To tie everything together, our GIS and EQuIS systems are our primary data compilation source that makes our advanced analytics/visualization and automation/tracking our data possible. Specific examples will be discussed, as will challenges encountered during the continuing development of the IM system. The incorporation of software advancements to the existing IM system for Port Hope characterization has improved the quality of the surveys, the tracking of completion, meeting schedule requirements and providing the required data for tracking, report preparation and supporting remediation of contamination on the properties. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

An Allyl Uranium(IV) Sandwich Complex: Are ϕ Bonding Interactions Possible?

Abstract A method to explore head‐to‐head ϕ back‐bonding from uranium f‐orbitals into allyl π* orbitals has been pursued. Anionic allyl groups were coordinated to uranium with tethered anilide ligands, then the products were investigated by using NMR spectroscopy, single‐crystal XRD, and theoretical methods. The (allyl)silylanilide ligand, N ‐((dimethyl)prop‐2‐enylsilyl)‐2,6‐diisopropylaniline (LH), was used as either the fully protonated, singly deprotonated, or doubly deprotonated form, thereby highlighting the stability and versatility of the silylanilide motif. A free, neutral allyl group was observed in UI 2 (L1) 2 ( 1 ), which was synthesized by using the mono‐deprotonated ligand [K][ N ‐((dimethyl)prop‐2‐enyl)silyl)‐2,6‐diisopropylanilide] (L1). The desired homoleptic sandwich complex U[L2] 2 ( 2 ) was prepared from all three ligand precursors, but the most consistent results came from using the dipotassium salt of the doubly deprotonated ligand [K] 2 [ N ‐((dimethyl)propenidesilyl)‐2,6‐diisopropylanilide] (L2). This allyl‐based sandwich complex was studied by using theoretical techniques with supporting experimental spectroscopy to investigate the potential for phi (ϕ) back‐bonding. The bonding between U IV and the allyl fragments is best described as ligand‐to‐metal electron donation from a two carbon fragment‐localized electron density into empty f‐orbitals.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2021

Periodic trends in gas–phase oxidation and hydrogenation reactions of lanthanides and 5d transition metal cations

Of the many publications coming from the laboratory of Diethard K. Bohme, among the most valuable were the surveys of reactivity throughout the periodic table as studied using selected ion flow tube (SIFT) mass spectrometry. In all cases, quantitative rate constants at 295 K and 0.35 Torr of He were obtained for metal cations generated by an inductively coupled plasma (ICP). This source creates ions at a temperature characterized as 5500 K. Here, it was believed that radiative relaxation and interactions with the flow gases would rapidly deplete most excited electronic states of the metal cations, although this is unknown

transition metals↗
DOE OSTI2025

Preliminary Insights Into the Feasibility of Determining the Purification Date of Enriched Uranium by Direct Measurement of the 230 Th/ 234 U Ratio Using an All-Faraday Detector Configuration on the Neoma MC-ICP-MS

Rationale: Mass spectrometric measurement of the 230 Th/ 234 U ratio to calculate the purification age of enriched uranium is typically conducted via a combination of ion counters and faraday detectors, thus requiring an inter-detector calibration scheme. Here, our aim is to understand whether the pursuit of a simplified measurement scheme involving only faraday detectors is feasible. Methods: We investigate the possibility of determining U-Th model ages for two enriched uranium standards (NBL U630 and U850) by direct measurement of the 230 Th/ 234 U ratio (without chromatographic separation or isotope dilution) on a ThermoFisher Scientific Neoma MC-ICP-MS utilizing both solution and laser ablation (LA)-based sampling techniques and an all-faraday detector configuration. Results: For the solution mode analyses conducted on aliquots containing sub μg/mL total U, we produce composite average 230 Th/ 234 U model dates of May 19, 1988 (± 351 days), and March 26, 1961 (± 2.5 years) using the directly measured 230 Th/ 234 U ratios for the NBL U630 and U850 uranium standards, which have certified purification dates of June 6, 1988 (± 190 days), and December 31, 1957 (± 36.5 days), respectively. The ages produced by LA-based sampling of dried residues of the same standards deposited onto cotton TexWipes are less accurate and of poorer precision (June 23, 2004 ± 8.7 years for U630 and December 21, 1965 ± 7.9 years for U850) but still yield meaningful information in regards to the purification date. Conclusions: We believe that further refinement of the all faraday detector measurement approach to include development of a more robust Th/U relative sensitivity factor determination, signal cutoff selection, and data processing protocols will allow for this approach to be confidently applied to enriched uranium materials with unknown purification histories. Potential advantages of the method include the reduced sample handling and infrastructure requirements as well as the ability to simultaneously generate a broad picture of the uranium isotopic composition in tandem with the U-Th age determination.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Corrosion Resistance and Mechanical Stability of Nickel Alloys in Molten-Salt Nuclear Reactors

Choosing structural materials for molten-salt nuclear reactors is a high-priority problem. The results making it possible to choose the basic structural material for a molten-salt nuclear reactor are colligated in the present article. Forced and natural circulation setups operating under reactor and laboratory conditions with molten metal-fluoride salts with different compositions have been developed at the National Research Center Kurchatov Institute: LiF–NaF–BeF{sub 2}–PuF{sub 3}, LiF–BeF{sub 2}–UF{sub 4}, and LiF–BeF{sub 2}–ThF{sub 4}–UF{sub 4}. Corrosion tests were conducted with domestically produced corrosion-resistant steel (12Kh18N10T, EP-164) and specially developed nickel-based alloys (KhN80M-VI, KhN80MTYu, KhN80MTV, et al.) as well as the alloy Hastelloy (USA), MONICR (Czechoslovakia) and EM-721 (France) in the working temperature range 600–800°C and mechanical loads up to 80 MPa on the samples.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2018

Detection of Delayed Neutrons from Fissionable Samples: Monte Carlo Modelling and Physical Assumptions for a Design of the DET-12 Device

An activation of fissionable materials with neutrons has been considered as a possible neutron diagnostic of D–D and D–T fusion plasma. Fission reaction caused by fusion neutrons leads up to emission of secondary neutrons: prompt and delayed. Physical assumptions have been outlined to design a new device (DET-12) for measurements of delayed neutrons emitted from samples of fissionable materials activated with neutrons at big fusion-plasma devices. The aim is to support a classic neutron activation method used as one of plasma diagnostics at tokamaks or stellarators. An interpretation of the time decay of delayed neutrons enables an assessment of the primary neutron flux which induced fission reaction. Monte Carlo calculations have been carried out in order to elaborate the method considered. Nuclides like: pure {sup 235}U, {sup 238}U and {sup 232}Th, have been selected as possible materials to be irradiated. Physical fundamentals of generation of the delayed neutrons are mentioned and a resulting concept of the DET-12 device, built in the Institute of Nuclear Physics, Poland, is presented. A general size and dimensions of particular constituent material layers, and a number and placement of neutron detectors are optimized by means of Monte Carlo modelling. Recommendations for a technical design of the measuring chamber were formulated. Detection efficiency of DET-12 has been also estimated.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Radiochronological Age of a Uranium Metal Sample from an Abandoned Facility

A piece of scrap uranium metal bar buried in the dirt floor of an old, abandoned metal rolling mill was analyzed using multi-collector inductively coupled plasma mass spectroscopy (MC-ICP-MS). The mill rolled uranium rods in the 1940s and 1950s. Samples of the contaminated dirt in which the bar was buried were also analyzed. The isotopic composition of uranium in the bar and dirt samples were both the same as natural uranium, though a few samples of dirt also contained recycled uranium; likely a result of contamination with other material rolled at the mill. The time elapsed since the uranium metal bar was last purified can be determined by the in-growth of the isotope {sup 230}Th from the decay of {sup 234}U, assuming that only uranium isotopes were present in the bar after purification. The age of the metal bar was determined to be 61 years at the time of this analysis and corresponds to a purification date of July 1950 {+-} 1.5 years.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2018

New measurement of the 238 U decay constant with inductively coupled plasma mass spectrometry [New Measurement of the U-238 Decay Constant with Inductively Coupled Plasma Mass Spectrometry]

The 238 U decay constant (λ U-238 ) is fundamental to radioisotope-based chronometry in the Earth and planetary sciences, yet only a single published λ U-238 value (Jaffey et al. in Phys Rev C 4(5):1889–1906, 1971) is widely applied. We have determined λ U-238 via the novel approach of measuring of 234 Th ingrowth in high-purity 238U solutions, using isotope dilution mass spectrometry (ID-MS). The 234 Th decay constant (λ Th-234 ) was measured via decay counting with high-purity Ge (HPGe) $\gamma$ detectors. Preliminary results for λ U-238 agree with the value determined by $a$-counting [1] within the elevated uncertainty of 0.462% (k = 2). Ongoing efforts to reproduce λ U-238 with reduced experimental uncertainties will inform future conclusions.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Results from a controlled depleted uranium metal casting experiment designed to investigate nuclear Forensic Radiochronometry Signatures

The accurate interpretation of uranium metal 230 Th/ 234 U and 231 Pa/ 235 U radiochronometry model ages requires an understanding of how uranium parent nuclides and decay progeny ( 230 Th and 231 Pa) behave during uranium metal casting. In order to directly measure the spatial distribution of 230 Th and 231 Pa in uranium metal before and after vacuum induction melting (VIM), Los Alamos National Laboratory identified uranium metal feedstock, characterized the metal feedstock, conducted a controlled casting experiment of an approximately 120 kg uranium metal rod, and characterized the cast metal. Herein this study presents radiochronometry results and quantified 230 Th and 231 Pa VIM separation factors from bulk uranium.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Model ages of three uranium metal CRMs and implications for radiochronometry data interpretation

In this study, we report 230 Th/ 234 U and 231 Pa/ 235 U model ages in three uranium metal certified reference materials with distinct production histories and isotopic compositions ranging from depleted to highly enriched (CRMs 112-A, 115, and 116-A). Here, our results provide the first model age values for these materials using multiple radiochronometers, which can be used as reference values for quality control of radiochronometry measurements performed during nuclear forensic investigations. Furthermore, we evaluate the model ages in the context of available production records for the materials, which provides insight into the processes that may impact radiochronometry systems during uranium metal production.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2015

Unconventional Energy Resources: 2015 Review

This paper includes 10 summaries for energy resource commodities including coal and unconventional resources, and an analysis of energy economics and technology prepared by committees of the Energy Minerals Division of the American Association of Petroleum Geologists. Unconventional energy resources, as used in this report, are those energy resources that do not occur in discrete oil or gas reservoirs held in structural or stratigraphic traps in sedimentary basins. Such resources include coalbed methane, oil shale, U and Th deposits and associated rare earth elements of industrial interest, geothermal, gas shale and liquids, tight gas sands, gas hydrates, and bitumen and heavy oil. Current U.S. and global research and development activities are summarized for each unconventional energy resource commodity in the topical sections of this report, followed by analysis of unconventional energy economics and technology.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2018

Radiation-chemical processes leading to origination and accumulation of oxygen in the Earth’s atmosphere

The role of natural radioactivity in the formation of the oxygen atmosphere of the Earth is discussed. The origination of oxygen in the free state in the hydrosphere and atmosphere is associated with the radiolysis of the water of the World ocean under the irradiation of radio active isotopes {sup 40}K, {sup 235}U, {sup 238}U, and {sup 232}Th. The calculations showed that within the last 3.8 billion years the total weight of oxygen, which could be formed due to this process, is about 7.4•10{sup 17} kg, i.е., the value of the same order as the oxygen content in the modern atmosphere of the Earth. The Ocean was an intermediate collector and provided the nucleation of new forms of biological life with oxygen respiration. The consecutive transformation of the Earth’s atmosphere with a gradual increase in the oxygen content became the result of photosynthesis in algae and green plants and thus opened a way to the origination of complicated forms of the life.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗