Preliminary Uncertainty Analysis Research Articles

Techno-economic analysis of ammonia cracking for large scale power generation

The increasing interest in leveraging green ammonia to mitigate carbon emissions in fertilizer production is paralleled by an expanding acknowledgment of its potential as a fuel for decarbonizing the electricity sector, particularly in high-efficiency gas turbine power plants. Co-firing ammonia with hydrogen presents a promising method for integrating ammonia into existing infrastructures. Within this context, the development of efficient technology for ammonia cracking presents a potential avenue for deploying ammonia in gas turbines. The objective of this study is to conduct a preliminary techno-economic evaluation and uncertainty analysis of two cracking technologies namely a membrane reactor and a conventional FTR (Fired Tubular Reactor) for the co-firing of ammonia with hydrogen in a CCGT (Combined Cycle Gas Turbine) plant. The integration of a membrane reactor during the cracking stage demonstrates a remarkable improvement in the system's thermal efficiency, surpassing traditional approaches by over 25%. Additionally, it brings about an approximate 10% reduction in the levelized cost of hydrogen (LCOH), despite a higher initial capital expenditure (CAPEX). At the CCGT level, the discrepancy in levelized cost of electricity (LCOE) narrows, as it is strongly influenced by the cost of ammonia constituting 80% of the LCOE. Beyond LCOE, the widespread adoption of these systems also faces challenges due to material scarcity. Analysis reveals that revamping just 1 GWe of CCGT assets using membrane reactors would for example necessitate approximately 0.11% of the global palladium supply, and 10% of the global ruthenium production. Considering the limited availability of these resources, coupled with their high demand across multiple sectors and the possibility of external factors such as geopolitical tensions, this strategy seems unfeasible. To tap into this market, future research should prioritize the exploration of alternative membrane materials, such as carbon molecular sieves, and catalysts, like nickel.

Effect of Salt Solution Tracer Dosage on the Transport and Mixing of Tracer in a Water Model of Asymmetrical Gas-Stirred Ladle with a Moderate Gas Flowrate

In previous research simulating steelmaking ladles using cold water models, the dosage/volume of the salt tracer solution is one of the factors that has been overlooked by researchers to a certain extent. Previous studies have demonstrated that salt tracers may influence the flow and measured mixing time of fluids in water models. Based on a water model scaled down from an industrial 130-ton ladle by a ratio of 1:3, this study investigates the impact of salt tracer dosage on the transport and mixing of tracers in the water model of gas-stirred ladle with a moderate gas flow rate. A preliminary uncertainty analysis of the experimental mixing time is performed, and the standard deviations were found to be less than 15%. It was observed in the experiments that the transport paths of tracers in the ladle can be classified into two trends. A common trend is that the injected salt solution tracer is asymmetrically transported towards the left sidewall of the ladle by the main circulation. In another trend, the injected salt solution tracer is transported both by the main circulation to the left side wall and by downward flow towards the gas column. The downward flow may be accelerated and become a major flow pattern when the tracer volume increases. For the dimensionless concentration curve, the sinusoidal type, which represents a rapid mixing, is observed at the top surface monitoring points, while the parabolic type is observed at the bottom monitoring points. An exception is the monitoring point at the right-side bottom (close to the asymmetric gas nozzle area), where both sinusoidal-type and parabolic-type curves are observed. Regarding the effect of tracer volume on the curve and mixing time, the curves at the top surface monitoring points are less influenced but curves at the bottom monitoring points are noticeably influenced by the tracer volume. A trend of decreasing and then increasing as the tracer volume increases was found at the top surface monitoring points, while the mixing times at the bottom monitoring points decrease with the increase in the tracer volume.

Non-contact ultra-precision metrology of superfine cylinders with a developed two-dimensional coordinate measuring device

To address the issue of measuring force of a stylus that can move and/or hook up the measured workpiece with a small dimension in the contact measurement, a spectral confocal displacement sensor and an ultra-precision linear stage are employed to develop a two-dimensional coordinate measuring machine instead of the conventional stylus contact measurement to avoid the measuring force problem, by which the non-contact ultra-precision metrology can be achieved. A coordinate modeling-dividing method is proposed for the diameter and roundness measurement of the small cylindrical workpieces with a diameter of 0.5 mm and length of 50 mm, whose cross-sectional circle is divided into several equal arcs to be scanned by the developed two-dimensional coordinate measuring machine. Thus, a set of arcs, each of which consists of large numbers of coordinate points, can be obtained. The radius of each arc can be fitted by the least square method, and the arc profile can be characterized by a series of data processing. The diameter and roundness of the measured workpiece can be obtained by averaging these fitted arcs’ radii and stitching these arc profiles together, respectively. A preliminary measurement uncertainty analysis is carried out to verify the developed device and proposed method.

Preliminary techno-economic assessment and uncertainty analysis of scaled-up integrated process for bioactive extracts production from Senna alata (L.) leaves

This work reported the effects of heat-assisted extraction (HAE) temperature (35–55 °C), solid: liquid (1:20–1:50 g/mL) and time (100–200 min) on the total phenolic content (TPC, GAE/g), bioactive extracts yield (EYs, %) and antioxidant activity (AA, AAE/g) of Senna alata leaves (SALs) using the Box-Behnken experimental design. Multi-objective HAE process optimization was also carried out. The large scale (1000 L extractor capacity) HAE integrated process was thereafter designed using the global optimum data and techno-economically analyzed. Profitability sensitivity and uncertainty analyzes were conducted on the large scale integrated process to determine the associated risk. The extraction temperature, solid: liquid and time had significant effects on TPC, EYs and AA. The extraction conditions at 54.97 °C, 41.59 g/mL and 100 min gave an optimum TPC, EYs and AA of 84.3897 mg GAE/g, 21.3607% and 6.61696 µM AAE/g, respectively. The phenolic profiling showed that SALs extracts were rich in betulinic, gallic, chlorogenic, caffeic and ferulic acids. The large scale integrated plant possessed net present value (NPV), internal rate of return (IIR), return on investment (ROI) and payback time (PBT) of 193.511 US$, 7.11%, 13.97%, and 7.16 y, respectively. The certainty of obtaining base case NPV and ROI were 55.88 and 60.96%. Out of technical and cost variables selected for sensitivity analysis, extracts recovery contributed the most (26.6 and 27.9% in NPV and ROI, respectively) while the extraction temperature and SALs purchase cost did not contribute significantly to the variance in NPV and ROI.

Uncertainty and Sensitivity Analysis of a Dry Cask for Spent Nuclear Fuel

Nuclear safety relies to a good extent on thoroughly validated codes. However, code predictions are affected by uncertainties that need to be quantified for a more accurate evaluation of safety margins. In this regard, the present paper proposes a preliminary uncertainty and sensitivity analysis of the thermal behavior of a concrete-based dry cask for spent nuclear fuel storage, employing the MELCOR code and a series of MATLAB scripts. As thermal behavior is of utmost importance for the fulfillment of United States Nuclear Regulatory Commission (USNRC) safety requirements, the Peak Cladding Temperature (PCT) has been addressed as the key Figure of Merit (FOM). Variables related to the main heat transfer mechanisms have been selected as input parameters for the uncertainty quantification, whereas heat source and heat sink, namely decay power and external air temperature, have been dealt with in a separate sensitivity analysis. The results show that the selected parameters have a weak influence on the PCT, whereas it is strongly related to the decay power and external air temperature values. In any case, PCT stays below the regulatory threshold even under the considered off-normal conditions.

Uncertainty and sensitivity analysis of the QUENCH-08 experiment using the FSTC tool

This paper presents results of a preliminary uncertainty and sensitivity (U&S) analysis of the QUENCH-08 experiment using the Fast Source Term Calculation (FSTC) tool, which currently is under development at KIT/INR as a part of WAME project. WAME is devoted to the development of a methodology and a tool for fast and accurate source term (ST) calculation in case of severe accident at nuclear power plant (NPP). The FSTC tool is divided into 2 parts: the U&S analysis and ST prediction (using the MOCABA approach), respectively. The description of the MOCABA approach, which is implemented in FSTC tool, will be presented – together with the results of ST evaluation – in a subsequent paper. In this paper, the FSTC tool is applied in conjunction with the Accident Source Term Evaluation Code (ASTEC) (version 2.2_b) severe accident (SA) code to the U&S analysis of the QUENCH-08 experiment to demonstrate the functionality of the tool and to check the methodology’s suitability for the application to a nuclear power plant.

AUTOMATED AND PERMANENT LONG-RANGE TERRESTRIAL LASER SCANNING IN A HIGH MOUNTAIN ENVIRONMENT: SETUP AND FIRST RESULTS

Abstract. A terrestrial laser scanner (TLS) of the type RIEGL VZ-6000 has been permanently installed and automated at Hintereisferner glacier located in the Ötztal Alps, Austria, to identify snow (re)distribution from surface height changes. A first case study is presented that shows and discusses detected snow distribution at the glacier after a snowfall event, together with concurrent snow erosion and deposition caused by avalanches. The paper shows the potential of a TLS system in a high mountain environment, which is also applicable to other environmental mapping applications. It introduces the setup of the TLS system, its automation procedure, and a first and preliminary uncertainty analysis. TLS data are generally influenced by four uncertainty sources: atmospheric conditions, scanning geometry, mechanical properties, and surface reflectance properties. The first three sources have significant influence on the TLS data at Hintereisferner, whereby the total accuracy of the TLS system is estimated to be in a range of a few decimetres, subject to ongoing more detailed data analysis.

Preliminary uncertainty and sensitivity analysis of the Molten Salt Fast Reactor steady-state using a Polynomial Chaos Expansion method

In this work, we present the results of a preliminary uncertainty quantification and sensitivity analysis study of the Molten Salt Fast Reactor (MSFR) behavior at steady-state performed by applying a non-intrusive Polynomial Chaos Expansion (PCE) approach. An in-house high-fidelity multi-physics simulation tool is used as reactor reference model. Considering several thermal-hydraulics and neutronics parameters as stochastic inputs, with a limited number of samples we build a PCE meta-model able to reproduce he reactor response in terms of effective multiplication factor, maximum, minimum, and average salt temperatures, and complete salt temperature distribution. The probability density functions of the responses are constructed and analyzed, highlighting strengths and issues of the current MSFR design. The sensitivity study highlights the relative importance of each input parameter, thus providing useful indications for future research efforts. The analysis on the whole temperature field shows that the heat exchanger can be a critical component, so its design requires particular care.

EVALUATION OF CRITICAL EXPERIMENTS IN THE UNIVERSITY OF WISCONSIN NUCLEAR REACTOR (UWNR) WITH UNCERTAINTY QUANTIFICATION

An improved computational model of the University of Wisconsin Nuclear Reactor (UWNR) was developed to support the benchmark evaluation of recent data acquired during an experimental campaign conducted at UWNR. Previous efforts led to a scripted UWNR model for automated generation of MCNP6 and Serpent inputs. This capability was extended to SCALE/KENO. All three tools were used to evaluate a variety of zero-power, fresh-critical configurations, and the results agreed well. The MCNP6 model was extended to support shuffling the core configuration, which allows the modeling of burnup for evaluation of depleted critical configurations. The MCNP6 model successfully predicts core reactivity over time, after accounting for the initial reactivity bias. The inclusion of SCALE/KENO input generation enables sensitivity and uncertainty analyses using the TSUNAMI and Sampler modules of SCALE. A preliminary uncertainty analysis was performed with TSUNAMI for nuclear data uncertainties while direct perturbation calculations were performed using MCNP6 for geometry and material uncertainties, which helped to identify model parameters with the largest effect on the eigenvalue. A transient UWNR transport Model in Mammoth/Rattlesnake is under development to simulate the transient experiments. The existing MCNP6 and Serpent models are used to provide the CAD file for meshing and homogenized cross-sections. In conclusion, the evaluation of UWNR benchmark data provides increased confidence in various states of the UWNR computational model and will provide a unique model for use by other analysts.

Development and application of a surrogate model for quick estimation of ex-vessel debris bed coolability

During a hypothetical severe accident of a Nordic boiling water reactor (BWR), an ex-vessel particulate debris bed is expected to form in the flooded lower drywell due to melt-coolant interactions after vessel failure. The key parameter to evaluate debris bed coolability is the dryout heat flux (DHF) or dryout power density, representing the limit of heat removal capacity by the coolant. Several numerical codes such as COCOMO have been developed to simulate thermal hydraulics in multi-dimensional debris beds and predict the cooling limit, but they are computationally expensive and not suitable for probabilistic risk analysis. This paper aims to develop a surrogate model which can serve as a quick-estimate tool for the dryout power density of a heap-like debris bed in a saturated water pool. The dryout power density predicted from the COCOMO code is treated as the full model. A characteristic factor is introduced as the dryout power density ratio between the multi-dimensional debris bed (predicted by COCOMO code) and the corresponding one-dimensional debris bed (predicted by Lipinski 0-D model). The characteristic factor is correlated by the Kriging method with six parameters: bed porosity, particle diameter, debris mass, bed slope, cavity radius and containment pressure. After the surrogate model is trained and validated, it is employed to analyze the coolability of prototypical debris beds of a reference Nordic BWR, given the bed mass and containment pressure from MELCOR simulation. Coolability maps are produced as quick look-up diagrams for identification of coolable domain with the variation of porosity, particle diameter and slope angle. A preliminary uncertainty analysis is performed to demonstrate the effect of uncertain input parameters on non-coolable domain.

Preliminary uncertainty analysis in fisheries – the case of two fisheries in Indonesia

Fisheries is a complex system which comprises two coupled and irreversible systems namely ecological system and social system. Moreover, these two systems have structural and functional integrity in which social or human system is part of ecological systems. Consequently, dynamics of these systems in the context of structural and functional interactions are high. In fisheries, this dynamics of interactions between intra and extra systems create uncertainty. This paper was aimed to explore the use of preliminary uncertainty analysis (PUA) in fisheries management in Indonesia using the comparison between two fisheries i.e. blue swimming crab fisheries and hairtail fisheries. From this paper we can reveal that magnitude of uncertainty in ecological system are lower than social/human system. In this regards a systematic ecosystem approach to fisheries management should be functionally adopted.

Towards codification of thunderstorm/downburst using gust front factor: Model-based and data-driven perspectives

Winds associated with gust fronts originating from a thunderstorm/downburst exhibit rapid changes during a short time period which may be accompanied by changes in direction. For several decades, a number of studies have been focused on identifying the characteristics of such nonstationary gust front winds in a variety of manners such as experimental/numerical methods and full-scale measurements. Yet, beginning the dialogue on any guidelines for design practice has thus far not evolved, in part due to a limited consensus on such characteristics among studies in conjunction with paucity of available data needed for vetting and corroborating, which is further impacted by the presence of nonstationarity. In an effort to establishing a new design procedure for this type of wind load effect on structures, the gust front factor (GFF) framework has been proposed by authors that encapsulates both the kinematic and dynamic features of gust front induced wind effects on structures, which distinguish themselves from those experienced in conventional boundary layer flows. This study revisits the gust front factor framework seeking to take the next step toward a possible initial framework for codification of gust front winds from model-based and data-driven perspectives. A modular and extensible web-enabled framework to estimate gust front related wind load effects is envisaged to rationally and holistically quantify design loads. This would promote design practice to enhance disaster resilience of the built environment. In this context, a closed-form expression concerning nonstationary fluctuations for a case of a long pulse duration is derived to facilitate rapid evaluation of nonstationary turbulence effects. A preliminary uncertainty analysis is also carried out to assess the influence of uncertainties associated with the load effects of gust front winds and the reliability of GFF. In addition, a comparison of the model-based gust front factor with a recently introduced thunderstorm response spectrum technique to assess their relative performance is carried out. In view of the lessons learned from the history of the gust loading factor on codes and standards, a possible living codification concept through a learning and updating invoking the emerging “Design Thinking” approach is discussed.

Uncertainty Analysis of Rainfall Scenarios for the Prediction of Flood Disasters in Urban Areas

As data analysis becomes increasingly important in the field of flood disasters, a data-based analytical model that considers hydraulic factors has emerged as an alternative to flood analysis. Data-driven modeling requires complex and extensive data that depend on actual and diverse hypothetical scenarios. Thus, preliminary data processing is required to utilize extensive input data efficiently and obtain accurate results. In this study, a gamma test was applied as a preliminary data processing technique to the efficient prediction of flood disasters in urban areas. Specifically, probability rainfall was calculated for the Daejeo and Dadae districts in Busan, and manhole overflow was estimated by inputting relevant data into a storm water management model (SWMM) with a Huff distribution. A preliminary uncertainty and sensitivity analysis was performed with the gamma test using combined time-series data for probability rainfall and manhole overflow, and then an optimal combination of data was selected for a simulation using correlativity analysis (Gamma, Gradient, Standard error, and V-ratio). The proposed method employs quantitative criteria for efficient selection of optimal input data, thus saving a greater amount of time and effort than when using the traditional method that derives results from repeated execution of models. Keywords: Data Analysis, Rainfall Scenario, Urban Flood, Gamma Test

Modelling water flow in a complex watershed in humid a tropical area using SWAT: a case study of Taabo watershed in Ivory Coast

ABSTRACTUnderstanding the water balance of a basin is the most important aspect in water resources development and management programmes. The objective of this study was to implement an agro-hydrological model (SWAT) to model water flow transport within the river network with a perspective to reduce the sedimentation and eutrophication of lakes in Ivory Coast. The daily simulation of SWAT model carried out in the period from 1979 to 1990 has been divided into warm-up (1979–1981), calibration (1982–1986) and validation (1987–1990). For calibrating the model, a preliminary sensitivity and uncertainty analysis in the SUFI-2 algorithm was performed based on 19 hydrologic parameters. The model has given good results of performance and robustness. All statistical parameters (Nash-Sutcliffe coefficient (NS) and the coefficient of determination (R2)) used to achieve the model performance of above 0.7 for the calibration period and around 0.6 for the validation period. As for the uncertainty criteria (P-factor and R-factor), the observation data are very good in general because more than 80% are bracketed by the 95PPU both for calibration and validation periods. Graphically, the streamflow predictions match well with actual measurements. Water transfers between the soil, surface water, groundwater and atmosphere are largely conditioned by the uneven spatial distribution of pedology, land use and climate.

Uncertainty evaluation of indentation modulus in the nano-range: Contact stiffness contribution

Evaluation of indentation modulus by instrumented indentation in the nano-range can use one of two methods for contact stiffness evaluation, according to current ISO standards. The relevance of contact stiffness, suggested by a preliminary uncertainty analysis, prompted development of improved evaluation procedures. Data on a series of indentation tests, performed in an international comparison on tungsten and fused silica with forces in the millinewton range, were analysed with standard methods, and two alternative ones. Uncertainty evaluation revealed some shortcomings in the standard methods concerning the estimation of contact stiffness and indentation modulus; some definite advantages are shown with improved procedures.

A Calibration System for Reference Radiosondes that Meets GRUAN Uncertainty Requirements

A new International System (SI) traceable calibration set-up for reference radiosondes is presented here with a preliminary uncertainty analysis. By meeting the GRUAN requirements, this development...

Design features and thermal margin assessment of core protection and monitoring systems of an integral reactor, SMART

The Korea Atomic Energy Research Institute has developed the SMART integral reactor, and SCOPS and SCOMS were also newly developed as advanced real-time core protection and monitoring systems for SMART. SCOPS calculates the minimum DNBR and maximum LPD based on several on-line measured core state parameters, and SCOMS calculates the limiting conditions for operation variables and assists the operator in implementing the technical specification requirements for monitoring. The design features and characteristics of SCOPS and SCOMS were described. The performance of the SCOMS power distribution synthesis method was evaluated and shows negligible power distribution synthesis errors. A technically reliable uncertainty analysis method was developed, and a preliminary uncertainty analysis was evaluated. The overall analysis results are similar or more improved compared to those of cycle 1 for Younggwang units 3&4 of Korea. In particular, uncertainty factors of SCOMS are much improved because of an improvement in the power distribution synthesis and DNBR calculation algorithm. Finally, thermal margins were estimated, and the DNB overpower margin of SCOMS is large enough to accommodate a 40% required overpower margin and 15% top-tier requirement thermal margin.

Measurements of liquid-phase turbulence in gas–liquid two-phase flows using particle image velocimetry

Liquid-phase turbulence measurements were performed in an air–water two-phase flow loop with a circular test section of 50 mm inner diameter using a particle image velocimetry (PIV) system. An optical phase separation method-–planar laser-induced fluorescence (PLIF) technique—which uses fluorescent particles and an optical filtration technique, was employed to separate the signals of the fluorescent seeding particles from those due to bubbles and other noises. An image pre-processing scheme was applied to the raw PIV images to remove the noise residuals that are not removed by the PLIF technique. In addition, four-sensor conductivity probes were adopted to measure the radial distribution of the void fraction. Two benchmark tests were performed: the first was a comparison of the PIV measurement results with those of similar flow conditions using thermal anemometry from previous studies; the second quantitatively compared the superficial liquid velocities calculated from the local liquid velocity and void fraction measurements with the global liquid flow rate measurements. The differences of the superficial liquid velocity obtained from the two measurements were bounded within ±7% for single-phase flows and two-phase bubbly flows with the area-average void fraction up to 18%. Furthermore, a preliminary uncertainty analysis was conducted to investigate the accuracy of the two-phase PIV measurements. The systematic uncertainties due to the circular pipe curvature effects, bubble surface reflection effects and other potential uncertainty sources of the PIV measurements were discussed. The purpose of this work is to facilitate the development of a measurement technique (PIV-PLIF) combined with image pre-processing for the liquid-phase turbulence in gas–liquid two-phase flows of relatively high void fractions. The high-resolution data set can be used to more thoroughly understand two-phase flow behavior, develop liquid-phase turbulence models, and assess high-fidelity codes for multi-phase flows.

Model Comparison and Uncertainty Quantification for Geologic Carbon Storage: The Sim-SEQ Initiative

Sim-SEQ is a model comparison initiative for geologic carbon storage (GCS). Within this initiative, 15 different modeling teams are developing conceptual models for flow and transport of an injected CO2 plume at the Sim-SEQ study site (the S-3 site) located near Cranfield, Mississippi. The objective of the project is to understand the sources of model uncertainty in GCS, and if possible, to quantify these uncertainties through comparison of the different conceptual models and also through comparison with observed data from the S-3 site. In this paper, we compare six different conceptual models of the S-3 site, and present a preliminary uncertainty analysis of these six models using a generalized linear model approach. We show that differences in model conceptualization and interpretation of site characterization data cause a significant range in predictions.

Technique for the calibration of thermal voltage converters using a Josephson waveform synthesizer and a transconductance amplifier

This paper describes a simple and effective technique for calibrating thermal converters for an ac–dc voltage transfer difference using a Josephson waveform synthesizer and a transconductance amplifier. Preliminary measurements and uncertainty analysis confirm the possibility of achieving systematic uncertainties below 0.1 µV V−1 at frequencies up to 1 kHz.