SEARCH · Search NASA

Results for “pool”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41

All sources NASA NTRS DOE OSTI

DOE OSTI2019

Impact of Radical Hysterectomy Versus Simple Hysterectomy on Survival of Patients with Stage 2 Endometrial Cancer: A Meta-analysis

Background: The strategy of radical surgery for stage 2 endometrial cancer (EC) remains controversial. This meta-analysis aimed to investigate the impact of radical hysterectomy (RH) versus simple hysterectomy (SH) on survival of patients with stage 2 EC. Methods: A systematic review was conducted to identify studies comparing survival between RH and SH in International Federation of Gynecology and Obstetrics (FIGO) stage 2 EC patients by searching several databases to July 2018. Hazard ratios (HRs) with 95% confidence intervals (CIs) for overall survival and progression-free survival were pooled using Stata V.12.0. Results: The study included 10 retrospective cohort studies enrolling 2866 patients. Patients who received RH did not show a significant survival benefit for either overall survival (pooled HR 0.92; 95% CI 0.72–1.16; P = 0.484) or progression-free survival (pooled HR 0.75; 95% CI 0.39–1.42; P = 0.378). The result remained consistent after it was balanced with possible impact from adjuvant radiotherapy (pooled HR 0.85; 95% CI 0.62–1.16; P = 0.300). In earlier studies that staged patients according to FIGO 1988, RH showed a 27% survival benefit (pooled HR 0.73; 95% CI 0.53–1.00; P = 0.050), whereas in newly published studies based on FIGO 2009 staging, it reversely showed increased risk of death (pooled HR 1.24; 95% CI 0.86–1.77; P = 0.245). However, no statistical significance was reached under either staging criterion. Conclusions: Based on the results of this meta-analysis, RH does not significantly improve survival in stage 2 EC. The choice of RH remains controversial and should be considered carefully in clinical practice. More qualified studies are needed to determine the best treatment strategy for stage 2 EC.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2014

Feasibility Study For Use Of Commercial Cask Vendor Dry Transfer Systems To Unload Used Fuel Assemblies In L-Area

The purpose of this study is to determine whether a commercial dry transfer system (DTS) could be used for loading or unloading used nuclear fuel (UNF) in L-Basin and to determine if a DTS pool adapter could be made for L-Basin Transfer Pit #2 that could accommodate a variety of DTS casks and fuel baskets or canisters up to 24” diameter.[1, 2] This study outlines the technical feasibility of accommodating different vendor dry transfer systems in the L-Basin Transfer Bay with a general work scope. It identifies equipment needing development, facility modifications, and describes the needed analyses and calculations. After reviewing the L-Basin Transfer Bay area layout and information on the only DTS system currently in use for the Nuclear Assurance Corporation Legal Weight Truck cask (NAC LWT), the authors conclude that use of a dry transfer cask is feasible. AREVA was contacted and acknowledged that they currently do not have a design for a dry transfer cask for their new Transnuclear Long Cask (TN-LC) cask. Nonetheless, this study accounted for a potential future DTS from AREVA to handle fuel baskets up to 18” in diameter. Due to the layout of the Transfer Bay, it was determined that a DTS cask pool adapter designed specifically for spanning Pit #2 and placed just north of the 70 Ton Cask lid lifting superstructure would be needed. The proposed pool adapter could be used to transition a fuel basket up to 24” in diameter and ~11 feet long from a dry transfer cask to the basin. The 18” and 24” applications of the pool adapter are pending vendor development of dry transfer casks that accommodate these diameters. Once a fuel basket has been lowered into Pit #2 through a pool adapter, a basket cart could be used to move the basket out from under the pool adapter for access by the 5 Ton Crane. The cost to install a dry transfer cask handling system in L-Area capable of handling multiple vendor provided transport and dry transfer casks and baskets with different diameters and lengths would likely be on the same order of magnitude as the Basin Modifications project. The cost of a DTS capability is affected by the number of design variations of different vendor transport and dry transfer casks to be considered for design input. Some costs would be incurred for each vendor DTS to be handled. For example, separate analyses would be needed for each dry transfer cask type such as criticality, shielding, dropping a dry transfer cask and basket, handling and auxiliary equipment, procedures, operator training, readiness assessments, and operational readiness reviews. A DTS handling capability in L-Area could serve as a backup to the Shielded Transfer System (STS) for unloading long casks and could support potential future missions such as the Idaho National Laboratory (INL) Exchange or transferring UNF from wet to dry storage.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2023

Real-Time and Rapid Respiratory Response of the Soil Microbiome to Moisture Shifts

Microbial response to changing environmental factors influences the fate of soil organic carbon, and drought has been shown to affect microbial metabolism and respiration. We hypothesized that the access of microbes to different carbon pools in response to dry–rewet events occurs sequentially at different rates. We amended desiccated soils with 13 C-labeled glucose and measured the rates of 12 CO 2 and 13 CO 2 respiration in real time after rewetting. Using these differentiated 12 CO 2 and 13 CO 2 respiration rate soils after rewetting, we were able to deduce when microbes are accessing different pools of carbon. Immediately upon rewetting, respiration of 12 CO 2 occurred first, with negligible 13 CO 2 respiration. Appreciable metabolism and respiration of the added 13 C glucose did not occur until 15 min after rewetting. We conclude that, while all carbon pools are being accessed in the first 9 h after rewetting, the rate and timing at which new and existing carbon pools are being accessed varies. Within this study, using stable isotope-labeled substrates to discern which carbon pools are metabolized first uniquely illustrates how microorganisms access different carbon pools which has implications into understanding how carbon metabolism can further affect climate, carbon sequestration, and soil health.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2017

Transient dynamics of terrestrial carbon storage: Mathematical foundation and its applications

Terrestrial ecosystems have absorbed roughly 30% of anthropogenic CO 2 emissions over the past decades, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling and experimental and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under global change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g., net primary production, NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, which is the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Moreover, this and our other studies have demonstrated that one matrix equation can replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3-D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. In addition, the physical emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. Altogether, this new mathematical framework offers new approaches to understanding, evaluating, diagnosing, and improving land C cycle models.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1991

Determination and impact of surface radiative processes for TOGA COARE

Experiments using atmospheric general circulation models have shown that the atmospheric circulation is very sensitive to small changes in sea surface temperature in the tropical western Pacific Ocean warm pool region. The mutual sensitivity of the ocean and the atmosphere in the warm pool region places stringent requirements on models of the coupled ocean atmosphere system. At present, the situation is such that diagnostic studies using available data sets have been unable to balance the surface energy budget in the warm pool region to better than 50 to 80 W/sq m. The Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean Atmosphere Response Experiment (COARE) is an observation and modelling program that aims specifically at the elucidation of the physical process which determine the mean and transient state of the warm pool region and the manner in which the warm pool interacts with the global ocean and atmosphere. This project focuses on one very important aspect of the ocean atmosphere interface component of TOGA COARE, namely the temporal and spatial variability of surface radiative fluxes in the warm pool region.

Curry, Judith A.↗

NASA NTRS2004

Variability of collagen crosslinks: impact of sample collection period

Because of the variability of collagen crosslinks, their use as markers for bone resorption is often criticized. We hypothesized that the variability could be reduced by collecting urine for 24 hours (or longer) instead of using single voids, and by not normalizing to creatinine. Urine samples were collected from 22 healthy subjects during two or more 24-hour periods. Each 24-hour pool and each 2nd void of the day were analyzed for N-telopeptide (NTX), pyridinium (PYD), and deoxypyridinoline (DPD) crosslinks. Data were analyzed by using linear regression. For NTX, R2 for the two, 2nd-void samples (n = 38) was 0.55, whereas R2 for the two 24-hour pools was 0.51 or 0.52, expressed per day or per creatinine. For PYD and DPD, R2 for the 2nd-void samples was 0.26 and 0.18, R2 for the 24-hour pools expressed per day was 0.58 and 0.74, and R2 for the 24-hour pools expressed per creatinine was 0.65 and 0.76, respectively. Regression of the 2nd void and the corresponding 24-hour pool, expressed per day, yielded R2 = 0.19, 0.19, and 0.08, for NTX, PYD, and DPD, respectively (n = 76 each). For the 2nd-void sample and its corresponding 24-hour pool, expressed per creatinine, R2 = 0.24, 0.33, and 0.08, respectively. In a separate study, the coefficient of variation for NTX was reduced (P < 0.05) when data from more than one 24-hour collection were combined. Thus, the variability inherent in crosslink determinations can be reduced by collecting urine for longer periods. In research studies, the high variability of single-void collections, compounded by creatinine normalization, may alter or obscure findings.

Specimen Handling/methods↗

NASA NTRS2005

An Improved Analysis of Forest Carbon Dynamics using Data Assimilation

There are two broad approaches to quantifying landscape C dynamics - by measuring changes in C stocks over time, or by measuring fluxes of C directly. However, these data may be patchy, and have gaps or biases. An alternative approach to generating C budgets has been to use process-based models, constructed to simulate the key processes involved in C exchange. However, the process of model building is arguably subjective, and parameters may be poorly defined. This paper demonstrates why data assimilation (DA) techniques - which combine stock and flux observations with a dynamic model - improve estimates of, and provide insights into, ecosystem carbon (C) exchanges. We use an ensemble Kalman filter (EnKF) to link a series of measurements with a simple box model of C transformations. Measurements were collected at a young ponderosa pine stand in central Oregon over a 3-year period, and include eddy flux and soil C02 efflux data, litterfall collections, stem surveys, root and soil cores, and leaf area index data. The simple C model is a mass balance model with nine unknown parameters, tracking changes in C storage among five pools; foliar, wood and fine root pools in vegetation, and also fresh litter and soil organic matter (SOM) plus coarse woody debris pools. We nested the EnKF within an optimization routine to generate estimates from the data of the unknown parameters and the five initial conditions for the pools. The efficacy of the DA process can be judged by comparing the probability distributions of estimates produced with the EnKF analysis vs. those produced with reduced data or model alone. Using the model alone, estimated net ecosystem exchange of C (NEE)= -251 f 197g Cm-2 over the 3 years, compared with an estimate of -419 f 29gCm-2 when all observations were assimilated into the model. The uncertainty on daily measurements of NEE via eddy fluxes was estimated at 0.5gCm-2 day-1, but the uncertainty on assimilated estimates averaged 0.47 g Cm-2 day-1, and only exceeded 0.5gC m-2 day-1 on days where neither eddy flux nor soil efflux data were available. In generating C budgets, the assimilation process reduced the uncertainties associated with using data or model alone and the forecasts of NEE were statistically unbiased estimates. The results of the analysis emphasize the importance of time series as constraints. Occasional, rare measurements of stocks have limited use in constraining the estimates of other components of the C cycle. Long time series are particularly crucial for improving the analysis of pools with long time constants, such as SOM, woody biomass, and woody debris. Long-running forest stem surveys, and tree ring data, offer a rich resource that could be assimilated to provide an important constraint on C cycling of slow pools. For extending estimates of NEE across regions, DA can play a further important role, by assimilating remote-sensing data into the analysis of C cycles. We show, via sensitivity analysis, how assimilating an estimate of photosynthesis - which might be provided indirectly by remotely sensed data - improves the analysis of NEE.

Williams, Mathew↗

NASA NTRS2019

Operation of a Heat Pipe with Multiple Heat Loads Under Reflux Mode

"Heat pipes are being used on many spacecraft to acquire heat dissipated by the payload and transport the heat to a remote radiator. In instrument-level or spacecraft-level ground testing, many heat pipes are placed in a gravity-driven reflux mode where the condenser is well above the evaporator, resulting in the formation of a liquid pool at the bottom of the heat pipe. If a head load is applied to a site that is in contact with the liquid pool, the generated vapor will flow upward to the condenser and the condensate will fall back to the evaporator due the influence of gravity. Hence, the heat pipe can operate steadily under reflux mode because the heated site always has sufficient liquid supply to sustain the fluid flow. In contrast, when a heat load is applied to a site remote from the liquid pool, the heat pipe will be unable to transfer heat through liquid evaporation unless the heated site has a chance to be in contact with liquid. This can be accomplished by applying an additional heat load to the liquid pool to establish a reflux flow so that the remote site can capture the falling condensate. An experimental investigation was conducted to study the effect of gravity on the thermal performance of a heat pipe under reflux mode with multiple heat loads. An aluminum ammonia heat pipe with internal axial grooves was placed in a vertical position. Cooling was provided to the top of the heat pipe, and heat was applied to three sites below the condenser with various heat distributions. One of the heated sites was above the liquid pool, and two were in direct contact with the liquid pool. Test results showed that when a heat load was applied to either one or both of the lower sites, the heat pipe could run steadily under reflux mode. After a reflux flow had been established, a heat load could be applied to the upper site. If the upper site could capture sufficient liquid falling from the condenser to handle its heat load solely by liquid evaporation, the heat pipe could reach steady operation. Otherwise, the temperature of the upper site would oscillate due to its intermittent contact with the falling liquid. For a given heat load to the upper site, the amplitude of temperature oscillation decreased with an increasing heat load to the lower sites because there was more falling condensate available for the upper site to capture. Moreover, the temperature oscillation disappeared completely when the total heat loads to lower sites exceeded a threshold power, and the threshold power increased with an increasing heat load to the upper site."

Ku, Jentung↗

NASA NTRSDate not supplied

Critical Heat Flux of Liquid Hydrogen, Liquid Methane, and Liquid Oxygen: A Review of Available Data and Predictive Tools

Available experimental data dealing with critical heat flux (CHF) of liquid hydrogen (LH 2 ), liquid methane (LCH 4 ), and liquid oxygen (LO 2 ) in pool and flow boiling are compiled. The compiled data are compared with widely used correlations. Experimental pool boiling CHF data for the aforementioned cryogens are scarce. Based on only 25 data points found in five independent sources, the correlation of Sun and Lienhard (1970) is recommended for predicting the pool CHF of LH 2 . Only two experiments with useful CHF data for the pool boiling of LCH 4 could be found. Four different correlations including the correlation of Lurie and Noyes (1964) can predict the pool boiling CHF of LCH 4 within a factor of two for more than 70% of the data. Furthermore, based on the 19 data points taken from only two available sources, the correlation of Sun and Lienhard (1970) is recommended for the prediction of pool CHF of LO 2 . Flow boiling CHF data for LH 2 could be found in seven experimental studies, five of them from the same source. Based on the 91 data points, it is suggested that the correlation of Katto and Ohno (1984) be used to predict the flow CHF of LH 2 . No useful data could be found for flow boiling CHF of LCH 4 or LO 2 . The available databases for flow boiling of LCH 4 and LO 2 are generally deficient in all boiling regimes. This deficiency is particularly serious with respect to flow boiling.

Multi-Phase Flow↗

NASA NTRS2023

Critical Heat Flux of Liquid Hydrogen, Liquid Methane, and Liquid Oxygen: A Review of Available Data and Predictive Tools

Available experimental data dealing with critical heat flux (CHF) of liquid hydrogen (LH2), liquid methane (LCH4), and liquid oxygen (LO2) in pool and flow boiling are compiled. The compiled data are compared with widely used correlations. Experimental pool boiling CHF data for the aforementioned cryogens are scarce. Based on only 25 data points found in five independent sources, the correlation of Sun and Lienhard (1970) is recommended for predicting the pool CHF of LH2. Only two experiments with useful CHF data for the pool boiling of LCH4 could be found. Four different correlations including the correlation of Lurie and Noyes (1964) can predict the pool boiling CHF of LCH4 within a factor of two for more than 70% of the data. Furthermore, based on the 19 data points taken from only two available sources, the correlation of Sun and Lienhard (1970) is recommended for the prediction of pool CHF of LO2. Flow boiling CHF data for LH2 could be found in seven experimental studies, five of them from the same source. Based on the 91 data points, it is suggested that the correlation of Katto and Ohno (1984) be used to predict the flow CHF of LH2. No useful data could be found for flow boiling CHF of LCH4 or LO2. The available databases for flow boiling of LCH4 and LO2 are generally deficient in all boiling regimes. This deficiency is particularly serious with respect to flow boiling.

Multi-Phase Flow↗

DOE OSTI2017

Document Set Differentiability Analyzer v. 0.1

Software is a JMP Scripting Language (JSL) script designed to evaluate the differentiability of a set of documents that exhibit some conceptual commonalities but are expected to describe substantially different – thus differentiable – categories. The script imports the document set, a subset of which may be partitioned into an additions pool. The bulk of the documents form a basis pool. Text analysis is applied to the basis pool to extract a mathematical representation of its conceptual content, referred to as the document concept space. A bootstrapping approach is applied to that mathematical representation in order to generate a representation of a large population of randomly designed documents that could be written within the concept space, notably without actually writing the text of those documents.The Kolmogorov-Smirnov test is applied to determine whether the basis pool document set exhibits superior differentiation relative to the randomly designed virtual documents produced by bootstrapping. If an additions pool exists, the documents are incrementally added to the basis pool, choosing the best differentiated remaining document at each step. In this manner the impact of additional categories to overall document set differentiability may be assessed.The software was developed to assess the differentiability of job description document sets. Differentiability is key to meaningful categorization. Poor job differentiation may have economic, ethical, and/or legal implications for an organization. Job categories are used in the assignment of market-based salaries; consequently, poor differentiation of job duties may set the stage for legal challenges if very similar jobs pay differently depending on title, a circumstance that also invites economic waste.The software can be applied to ensure job description set differentiability, reducing legal, economic, and ethical risks to an organization and its people. The extraction of the conceptual space to a mathematical representation enables identification of exceedingly similar documents. In the event of redundancy, two jobs may be collapsed into one. If in the judgment of the subject matter experts the jobs are truly different, the conceptual similarities are highlighted, inviting inclusion of appropriate descriptive content to explicitly characterize those differences. When additional job categories may be needed as the organization changes, the software enables evaluation of proposed additions to ensure that the resulting document set remains adequately differentiated.

Osborn, Thor D.↗

DOE OSTI2018

Thermal Stratification Analysis for Sodium Fast Reactors

The sodium fast reactor (SFR) is the most mature reactor concept of all the generation-IV nuclear systems and is a promising reactor design that is currently under development by several organizations. The majority of sodium fast reactor designs utilize a pool type arrangement which incorporates the primary coolant pumps and intermediate heat exchangers within the sodium pool. These components typically protrude into the pool thus reducing the risk and severity of a loss of coolant accidents. To further ensure safe operation under even the most severe transients a more comprehensive understanding of key thermal hydraulic phenomena in this pool is desired. One of the key technology gaps identified for SFR safety is determining the extent and the effects of thermal stratification developing in the pool during postulated accident scenarios such as a protected or unprotected loss of flow incident. In an effort to address these issues, detailed flow models of transient stratification in the pool during an accident can be developed. However, to develop the calculation models, and ensure they can reproduce the underlying physics, highly spatially resolved data is needed. This data can be used in conjunction with advanced computational fluid dynamic calculations to aid in the development of simple reduced dimensional models for systems codes such as SAM and SAS4A/SASSYS-1.

Schneider, James↗

DOE OSTI2018

Thermal Stratification Analysis for Sodium Fast Reactors

Schneider, James↗

DOE OSTI2019

System Thermal-Hydraulic Modeling of the Phénix Dissymmetric Test Benchmark

Phénix is a French pool-type sodium-cooled prototype reactor; before the definitive shutdown, occurred in 2009, a final set of experimental tests are carried out in order to increase the knowledge on the operation and the safety aspect of the pool-type liquid metal-cooled reactors. One of the experiments was the Dissymmetric End-of-Life Test which was selected for the validation benchmark activity in the frame of SESAME project. The computer code validation plays a key role in the safety assessment of the innovative nuclear reactors and the Phénix dissymmetric test provides useful experimental data to verify the computer codes capability in the asymmetric thermal-hydraulic behaviour into a pool-type liquid metal-cooled reactor. This paper shows the comparison of the outcomes obtained with six different System Thermal-Hydraulic (STH) codes: RELAP5-3D©, SPECTRA, ATHLET, SAS4A/SASSYS-1, ASTEC-Na and CATHARE. The nodalization scheme of the reactor was individually achieved by the participants; during the development of the thermal-hydraulic model, the pool nodalization methodology had a special attention in order to investigate the capability of the STH codes to reproduce the dissymmetric effects which occurs in each loop and into pools, caused by the azimuthal asymmetry of the boundary conditions. The modelling methodology of the participants is discussed and the main results are compared in this paper to obtain useful guide lines for the future modelling of innovative liquid metal pool-type reactors.

Narcisi, V.↗

DOE OSTI2015

Intelligent uranium fission converter for neutron production on the periphery of the nuclear reactor core (MARIA reactor in Swierk - Poland)

The multipurpose, high flux research reactor MARIA in Otwock - Swierk is an open-pool type, water and beryllium moderated and graphite reflected. There are two not occupied experimental H1 and H2 horizontal channels with complex of empty rooms beside them. Making use of these two channels is not in conflict with other research or commercial employing channels. They can work simultaneously, moreover commercial channels covers the cost of reactor working. Such conditions give beneficial possibility of creating epithermal neutron stand for researches in various field at the horizontal channel H2 of MARIA reactor (co-organization of research at H1 channel is additionally planned). At the front of experimental channels the neutron flux is strongly thermalized - neutrons with energies above 0.625 eV constitute only ∼2% of the total flux. This thermalized neutron flux will be used to achieve high flux of epithermal neutrons at the level of 2x10{sup 9} n cm{sup -2}s{sup -1} by uranium neutron converter (fast neutron production - conversion of reactor core thermal neutrons to fast neutrons - and then filtering, moderating and finally cutting of unwanted gamma radiation). The intelligent converter will be placed in the reactor pool, near the front of the H2 channel. It will replace one graphite block at the periphery of MARIA graphite reflector. The converter will consist of 20 fuel elements - low enriched uranium plates. A fuel plate will be a part which will measure 110 mm wide by 380 mm long and will consist of a thin layer of uranium sealed between two aluminium plates. These plates, once assembled, form the fuel element used in converter. The plates will be positioned vertically. There are several important requirements which should be taken into account at the converter design stage: -maximum efficiency of the converter for neutrons conversion, -cooling of the converter need to be integrated with the cooling circuit of the reactor pool and if needed equipped with self-cooling system (enhanced comparing to the cooling properties inherent with regular rector pool water flows), -proper cooling conditions can be ensured by an appropriate water flow, so the resistance to flow has to be optimised, -the requirement of the minimum resistance to water flow leads to the openwork design of the fuel element separator, which, on the other hand, has to be strong enough to ensure the needed strength for mechanical load due to the fuel weight and forces associated with the water flow, -the possibility of changing beam and flux qualities by rotating the converter or repositioning the converter plates by moving or replacing with another materials. In order to minimize the neutron activation of the fuel in the converter, the possibility was predicted to remove the converter and to replace it with an aluminium dummy for the time when the beam at the channel H2 is not used. This means that both, the converter and the dummy, have to be easily removable from the converter socket. There has to be also the place in the water pool, near the research stand or in technological pool, where the converter can be safely stored (this place have to be proper for operation with plates i.e. changing amount of plates). Thermal and neutron load of the fuel plates in the converter will be inhomogeneous. In order to equalize these loads, the converter should be designed in such way that it would be possible to change the order of fuel plates. Moreover replacing the amount of the plates gives the opportunity to obtain different fluxes of neutrons (quantitatively and qualitatively i.e. energetically). The project of the converter is based on Monte Carlo calculation concerning neutron production and on Computational Fluid Dynamics (CFD) i.e. modelling of converter for thermodynamical aspects. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2025

Controlling mechanical properties of laser powder bed fused AlSi10Mg through manipulation of laser scan rotation

The microstructure and mechanical properties of laser powder bed fused (LPBF) AlSi10Mg alloys can be controlled by many processing parameters. This study focuses on the scan rotation angle, α, between adjacent layers, and establishes the relationship between α and tensile behavior of the as-built LPBF-processed AlSi10Mg alloy. Near-full density cubic coupons were manufactured using the same processing parameters but with systematic variation of α from 0° to 90°. Microscopic observations and X-ray diffraction analysis showed that differences among various coupons mainly include orientations of the melt pools with respect to the build direction and development of the crystallographic texture. The α=0° coupon and α=30° coupon showed the highest and lowest texture index, although the overall crystallographic texture was mild. Tensile specimens were manufactured horizontally and vertically using either α=0° or α=30°, but with various first layer laser direction with respect to the build plate. Notably, the α=0° specimen that was tested along the laser scan direction showed the largest yield strength (283 MPa) and highest tensile ductility (10.1 %). Quantitative image analysis and fractography were performed on all specimens. Results showed that the melt pool orientation with respect to the tensile direction affected the tensile behavior across the different specimens. This was closely related to the localized strain distribution within the melt pool and along the melt pool boundary for the different melt pool orientations observed. Further, these results demonstrate that the laser scan rotation angle between layers can be used to fine tune the mechanical properties of LPBF AlSi10Mg alloy.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Non-circular electron beam spot welds in stainless steel alloys

Circularly symmetric-shaped spot welds are desirable for welding applications as they relate to heat and fluid flow conditions in the melt pool with predictable weld penetrations and repeatable results. Non-circular spot welds on the other hand result in undesirable and unpredictable weld penetrations or non-bridging of the liquid melt pool across the joint. Two known causes for non-circular melt pools occur when welding dissimilar metals, or when welding with skewed electron or laser beams that are not perpendicular to the surface. A largely unexplored additional factor, shown here, is an asymmetric power density distribution within the beam that can create non-circular melt pools even though the beam dimensions are much smaller than the melt pool itself.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Cloud-resolving model intercomparison of an MC3E squall line case: Part I-Convective updrafts: CRM Intercomparison of a Squall Line

A constrained model intercomparison study of a mid-latitude mesoscale squall line is performed using the Weather Research & Forecasting (WRF) model at 1-km horizontal grid spacing with eight cloud microphysics schemes, to understand specific processes that lead to the large spread of simulated cloud and precipitation at cloud-resolving scales, with a focus of this paper on convective cores. Various observational data are employed to evaluate the baseline simulations. All simulations tend to produce a wider convective area than observed, but a much narrower stratiform area, with most bulk schemes overpredicting radar reflectivity. The magnitudes of the virtual potential temperature drop, pressure rise, and the peak wind speed associated with the passage of the gust front are significantly smaller compared with the observations, suggesting simulated cool pools are weaker. Simulations also overestimate the vertical velocity and Ze in convective cores as compared with observational retrievals. The modeled updraft velocity and precipitation have a significant spread across the eight schemes even in this strongly dynamically-driven system. The spread of updraft velocity is attributed to the combined effects of the low-level perturbation pressure gradient determined by cold pool intensity and buoyancy that is not necessarily well correlated to differences in latent heating among the simulations. Variability of updraft velocity between schemes is also related to differences in ice-related parameterizations, whereas precipitation variability increases in no-ice simulations because of scheme differences in collision-coalescence parameterizations.

Fan, Jiwen↗