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At least 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Increasing the content of long chain fatty acids in seed oil

Provided are plants that express, or overexpress, a pPLAIIIδ protein. Constitutive or seed-specific expression of pPLAIIIδ protein in Arabidopsis increases seed oil content, the amount of C20 and C22 fatty acids, and the amount of C56, C58, and C60 triacylglycerols, effectively resulting in significantly higher oil yield per plant. Use of pPLAIIIδ is therefore an effective biotechnological tool to significantly increase plant yield, including oil, and the amount of high value long chain fatty acids in agricultural and horticultural crops, especially oilseed crops.

Wang, Xuemin↗
DOE OSTI2012

Fuel cycle cost, reactor physics and fuel manufacturing considerations for Erbia-bearing PWR fuel with > 5 wt% U-235 content

The efforts to reduce fuel cycle cost have driven LWR fuel close to the licensed limit in fuel fissile content, 5.0 wt% U-235 enrichment, and the acceptable duty on current Zr-based cladding. An increase in the fuel enrichment beyond the 5 wt% limit, while certainly possible, entails costly investment in infrastructure and licensing. As a possible way to offset some of these costs, the addition of small amounts of Erbia to the UO{sub 2} powder with >5 wt% U-235 has been proposed, so that its initial reactivity is reduced to that of licensed fuel and most modifications to the existing facilities and equipment could be avoided. This paper discusses the potentialities of such a fuel on the US market from a vendor's perspective. An analysis of the in-core behavior and fuel cycle performance of a typical 4-loop PWR with 18 and 24-month operating cycles has been conducted, with the aim of quantifying the potential economic advantage and other operational benefits of this concept. Subsequently, the implications on fuel manufacturing and storage are discussed. While this concept has certainly good potential, a compelling case for its short-term introduction as PWR fuel for the US market could not be determined. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Demonstrating compliance with moderator content limits in uranium dioxide powder upon leaving a furnace environment

A challenge was posed to the criticality safety consultant to consider whether instrumentation identified by Plant Management in an existing facility could be claimed as appropriate safety measures to ensure compliance with moderator content limits in uranium dioxide (UO{sub 2}) powder. During processing of low enriched UO{sub 2}, trays of powder are heated in a steam and hydrogen environment in order to reduce fluoride levels. Whilst in the furnace environment criticality safety is ensured by the geometry of the furnace trays used to convey the powder; however, upon leaving the furnace the UO{sub 2} is bulked to a 210 litre drum subject to limited moderation control. Under fault conditions there is a potential that the powder may become wetted due to an imbalance in furnace gas flows resulting in steam condensing in the cooling section of the furnace. Therefore, the safety case methodology followed suggests that two independent and diverse safety measures are provided to terminate the progression of the fault(s) to criticality. The existing criticality safety case credits an infra-red moisture meter as one of two safety measures; however, the calibration procedure required to ensure this device remains suitable is a considerable challenge from a plant operability perspective. As an initial review failed to identify any suitable like-for-like replacement, the National Nuclear Laboratory (NNL) Nuclear Safety Section were requested by the customer to consider the existing criticality safety case and investigate whether any existing instrumentation could be used as an alternative method of detecting conditions in which excess moisture could be present within the furnace trays. A number of solutions were proposed and the benefits and challenges around each are discussed in this paper, concluding with the approach adopted by the project. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

How to Replace Co-60 Tracer when Faced with Unknown Variability of Initial Cobalt Content - 18059

Electricite de France (EDF), radioactive waste producer, is responsible for managing waste from dismantling of its permanently shut-down nuclear power plants. The process has been opened for more than 10 years for some plants of the first generation and is under preparation for the first pressurized water reactor (PWR) plants to be dismantled. Nowadays it is generally admitted that waste disposal is the main constraint of dismantling. In France, waste producer is required by safety rules to obtain an agreement from French governmental agency (ANDRA) before any waste production and for each type of waste under project. Such an agreement which is a technical file, is the proof that the container, the way of waste conditioning, waste composition itself and especially the activity of each radionuclide (RN), comply with all the requirements of the disposal safety studies. We should also notice in French regulation that the declaration process of activities i.e. the way the radiological content of each container is computed and declared is a prerequisite to its disposal shipment. Taking into account that EDF has already prepared numerous files describing the means to fill the container itself, the main problem to cope with now is the declaration of each RN which is present in each container ready to be shipped to the disposal. The paper points out the general case of Difficult- To-Measure (DTM) radionuclide management and specially the high difference between waste from plants in operation and waste from dismantling plants. Starting from a '3D' neutron flux cartography computation at 100% power, a specific global strategy of DTM activation RN evaluation for each type of waste has been developed. As the only tracer is Co- 60, which is almost always the case in EDF dismantling, the way to compute the global scaling factors of mix of different waste initial composition is easy when the cobalt initial composition (before irradiation by neutrons) is known. But, in some cases, cobalt is not included in the steel composition required for conception purposes but only considered as an impurity which maximum quantity is known. The result is that, even for a given family of waste corresponding to the same object for dismantling, the tracer value variability is not any more correlated with the irradiation level of the activated waste, which is completely spoiling any of its tracer property. The more the cobalt level variability is high, the more the necessary conservative choice of minimum cobalt level to compute the activation scaling factor will lead to an important overestimation of DTM RN using these scaling factor with respect to Co-60. The paper describes a method using residual thermal power measurement and removing computed Co-60 residual thermal power with the help of gamma measurement to give a new tracer without any chaotic behavior. The possible application is studied on interim storage of irradiated graphite sleeves mixed with stainless steel wires. This method avoids overestimation of graphite inventories coming from activation by neutron flux and using scaling factors with respect to any failing gamma tracer. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Origins and Contents of the Waste Specifications: the Example of the French LLW-SL Disposal Facility - 20016

The waste specifications published by Andra for its surface disposal facilities for Low and Intermediate, Short-Lived waste (CSA) are primarily defined to ensure the safe disposal of waste, both in the short and long term, spanning from disposal operations to hundreds of years after closure, when the man-made safety barriers have long disappeared into dust. The paper presents the methodology used at Andra to derive the CSA waste specifications, also known as Waste Acceptance Criteria, their contents, and the process in place to verify compliance of the waste with the specifications. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Minimum critical values for various fissile media with very low content of plutonium mixed in different kinds of matrix - 14340

For materials slightly contaminated by fissile nuclides (such as radioactive sludge), it could be useful to take into account the low fissile density in order to define the nuclear criticality safety limits (mass, volume,...) when this density is lower than the one of the optimally moderated fissile-water mixture (e.g. 30 g/dm{sup 3} for {sup 239}Pu). In such a case, if the material is modelled by the usual fissile-water mixture only, the fissile medium still contains a void fraction when the optimal moderation ratio is reached. Then, the question is to know whether modeling the other elements of the material can impact the nuclear criticality safety limits, in particular when they are good scattering elements. This paper aims at studying the impact of replacing the void fraction in plutonium fissile media, with various apparent densities, by different kinds of matrix containing scattering elements. Minimum critical values (mass, volume, diameter and thickness) have been determined for plutonium media, composed of 100 % {sup 239}Pu, with densities of 2, 5.8 and 7.3 g/dm{sup 3} in different kinds of matrix containing scattering elements (graphite, carbon, alumina, silica, magnesia, fluorite and calcium oxide). Different contents of the aforementioned scattering elements in the fissile media were studied and additional moderation was ensured by water. The results highlight that minimum critical values are lower when considering a fissile medium containing graphite, carbon, silica, alumina and magnesia with additional water moderation, compared to plutonium-water mixture only with the same low fissile apparent density. However, there is still a benefit of crediting density (critical values for a low fissile density are still higher than critical values without a density control). (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Microstructure and Mechanical Properties of Ni-Based Superalloy Nimonic 105 with Varying Carbon Content

High carbon levels have been found to improve the fabricability of high-strength cast and wrought Ni-based superalloys, enabling the development of superior cast/wrought materials. However, carbon also strongly influences the microstructure and mechanical properties of the alloys. Nimonic 105 variants with three different carbon concentrations were manufactured. A bimodal grain size was found in the intermediate carbon content variant, while the high (low) carbon resulted in fine (coarse) grains thereby significantly affecting creep performance. The variations in grain structure were attributed to the primary carbides. An intermediate carbon level showed the best combination of strength and ductility in tension at high-temperature but little improvement in, or even inferior, creep performance. Discussion of the results will establish an understanding of the influence of carbon on the microstructure and mechanical properties of high strength cast and wrought superalloys, providing insights into obtaining high-quality alloys for future high-temperature applications.

Fang, Xiaotian↗
DOE OSTI2024

Effect of Si Content in Electrode and SiO2 Additions to the Slag during Electroslag Remelting

Evolution of Si concentration in 316 stainless steel electrodes was observed during a melting campaign consisting of recycling electroslag remelted (ESR) ingots to make new electrodes using vacuum induction melting (VIM). This campaign consisted of iterations of VIM + ESR operations to optimize melting parameters. The effect of Si content on the melt parameters and ingot quality was further evaluated and additions of SiO2 to the slag chemistry were studied using research-scale experiments, x-ray diffraction (XRF), combustion analysis, visual inspections, and computational tools. The Si concentration was found to decrease by approximately 600 ppm following ESR of 150 lb. research-scale electrodes. Eventually, this led to failure of the slag skin and direct ingot/crucible contact. Additions of SiO2 to the slag at levels matching the original calculated Si concentration in the electrode did not eliminate the slag skin failure and the current during steady state increased to maintain a constant melt rate. In this investigation, we propose a mechanism of slag skin failure consisting of local concentration of current density due to absence, or breakage, of the SiO2 layer around the molten metal drop during ESR. This theory was reinforced by additional experiments in which Nb was added to the electrode to change the structure of the oxide layer around the drops.

Jablonski, Paul↗
DOE OSTI2024

Zero-power wireless system for crop water content monitoring

Zero power wireless sensors, devices, and systems are used for crop water content monitoring. The sensors consume no power while monitoring for the presence of dry crop conditions. Infrared reflectance from plants is measured and when selected spectral conditions are met, a circuit is closed, activating an alarm, an RFID tag, or a radio transmitter. The deployed sensors consume no power while monitoring, reducing or eliminating the need to change batteries.

Rinaldi, Matteo↗
DOE OSTI2015

Geologic Reservoir Content Model from Low-Temperature Geothermal Play Fairway Analysis for the Appalachian Basin

This dataset contains the known hydrocarbon reservoirs within the study area of the Geothermal Play Fairway Analysis for the Appalachian Basin (GPFA-AB) as part of Phase 1, Natural Reservoirs Quality Analysis. The final values for Reservoir Productivity Index (RPI) and uncertainty (in terms of coefficient of variation, CV) are included. RPI is in units of liters per MegaPascal-second (L/MPa-s), quantified using permeability, thickness of formation, and depth. A higher RPI is more optimal. Coefficient of Variation (CV) is the ratio of the standard deviation to the mean RPI for each reservoir. A lower CV is more optimal. Details on these metrics can be found in the Reservoirs_Methodology_Memo.pdf uploaded in the associated "Natural Reservoir Analysis" dataset linked below.

15 GEOTHERMAL ENERGY↗
DOE OSTI2017

Leaf Mass Area, Leaf Carbon and Nitrogen Content, Barrow, Alaska, 2012-2016

Carbon, Nitrogen and Leaf Mass Area of leaves sampled from the Barrow Environmental Observatory, Barrow, Alaska. Species measured; Arctophila fulva, Arctagrostis latifolia, Carex aquatilis, Dupontia fisheri, Eriophorum angustifolium, Petasites frigidus, Salix pulchra, Vaccinium vitis-idaea, Salix rotundifolia, Luzula arctica, Saxifraga punctata and Potentilla hyparctica. Samples collected in vegetation plots and outside vegetation plots over an area of approximate 1 km2 centered at 71.275 degrees N, 156.641 degrees W. This dataset contains 3 files in csv, xlsx, and pdf formats.The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research.The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska.Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1994

(abstract) A Comparison Between Measurements of the F-layer Critical Frequency and Values Derived from the PRISM Adjustment Algorithm Applied to Total Electron Content Data in the Equatorial Region

The Parametrized Real-Time Ionosphere Specification Model (PRISM) is a global ionospheric specification model that can incorporate real-time data to compute accurate electron density profiles. Time series of computed and measured data are compared in this paper. This comparison can be used to suggest methods of optimizing the PRISM adjustment algorithm for TEC data obtained at low altitudes.

total electron content TEC PRISM electron content ↗
DOE OSTI2025

Changes in soil water content and lateral flow exert large effects on soil thermal dynamics across Alaskan landscapes

Both lateral surface and subsurface water flow affect soil moisture dynamics, yet most land surface models only solve subsurface water movement vertically. Here, we use a 3D ecosystem model that considers both land surface and subsurface hydrologic processes to simulate soil moisture, which is then used to drive a 1-D vertical soil thermal model to simulate the soil moisture effects on soil thermal dynamics in central Alaska. Our coupled model improves soil temperature (ST) estimates by 43.5% in comparison with observational data. Soil moisture has little effect on ST during the wet season (-1.5%) and a substantial influence during the dry season (60%). Spatially, water lateral flow has significant impacts on both soil moisture and ST, causing model estimates for thawed areas in the transition season to increase by ~10% in the study area. Our results highlight the importance of considering dynamical soil moisture, as well as lateral flow effects, on soil thermal dynamics in permafrost regions.

54 ENVIRONMENTAL SCIENCES↗