Normal Operation Scenarios Research Articles

Enhancing wind turbine load response tool through geometric non-linearities correction: Case study on DEFlex and design load comparison

This paper introduces a rapid correction technique applied in DEFlex, Ørsted’s in-house aero-servo-hydro-elastic solver for offshore wind turbines. The technique addresses geometric non-linearities from large wind turbine blade deflections, focusing specifically on correcting the angle of attack for torsional deflections. To assess the implementation, comparisons were made with the literature and HAWC2, using the IEA 15-MW wind turbine blade subjected to static and simplified dynamic loading. Additionally, simulations of normal operation scenarios, both with and without turbulence, were performed on a real wind turbine exceeding 10 MW rated power. The results were compared with Siemens Gamesa Renewable Energys tool BHawC, which utilizes a co-rotational formulation for capturing large blade deflections. The findings reveal that coupling DEFlex with the correction method accurately captures the angle of attack dynamics and significantly improves the agreement of fatigue loads.

Investigation of DG units influence on 66 kV sub-transmission system network considering region load growth: a case study

Abstract Voltage breakdown in sub-transmission networks resulting from an increase in load demand can be addressed by incorporating distributed generation (DG) units such as hydro, wind, photovoltaic, and geothermal in some buses. This approach can lower power losses and the price of the primary generated energy while increasing network dependability and efficiency. Feasibility of dispersed generation integration & its effect on sub-transmission system operation were investigated using Ben Walied 66 kV sub-transmission network in Libya as a state. This study presents modified particle swarm optimization (MOPSO) technique to select the best option with dispersed generation units under various operating conditions. The Ben Walied 66 kV sub-transmission network has been subject of effects research on both normal operation and load growth scenarios. The goal of this study was to find best way to adjust penetration level of the three DGs in response to changes in the network loading. Three DG units have been refitted to study the effects on test networks for sub-transmission, which consist of 30 and 51 buses. A comparison analysis shows that while the ideal locations of DG units remain constant with load expansion, the optimal solution for the penetration level percentage of three DG units was boosted by new optimal sizes. Research has been done on how the power factor of distributed generators (DGs) affects the practical performance of 66 kV networks in steady-state conditions. The integration of DG units in regulating these losses and voltage variations is demonstrated by the results, which indicate that the ideal solution for DG unit’s power factor was at a value of 0.87 lagging.

A New Modeling Approach and Comprehensive Monitoring of Electrical Faults Through Spectral Analysis in DSIM

The objective of this study is to evaluate the dependability of double-star induction machines by employing meticulous monitoring and intelligent handling of potential electrical malfunctions that may arise during their functioning. Specifically, the research delves into the examination of three distinct fault types: rotor bar breakage, stator phase opening, and inter-turn short circuit. Utilizing a mathematical model developed in the natural reference frame (abc), our aim is to comprehensively delineate both normal and faulty operational scenarios. To categorize and gauge the gravity of identified faults, we employ a methodology rooted in spectral analysis. In order to ensure continuous machine operation, especially in instances of stator phase opening, our proposed mitigation approach entails intentionally opening a secondary phase positioned at a 90-degree angle to the faulty phase. This strategic alteration transforms the machine into a dual two-phase configuration. Through rigorous simulation analyses, our findings underscore the efficacy and pragmatic viability of the devised fault detection technique, offering valuable insights into the domain of electrical machine reliability and fault management.

Design and early operation of a new-generation internal beam dump for CERN’s Super Proton Synchrotron

The Super Proton Synchrotron (SPS) is the last stage in the injector chain for CERN’s Large Hadron Collider, and it also provides proton and ion beams for several fixed-target experiments. The SPS has been in operation since 1976, and it has been upgraded over the years. For the SPS to operate safely, its internal beam dump must be able to repeatedly absorb the energy of the circulating beams without sustaining damage that would affect its function. The latest upgrades of the SPS led to the requirement for its beam dump to absorb proton beams with a momentum spectrum from 14 to 450 GeV/c and an average beam power of up to ∼270 kW. This paper presents the technical details of a new design of the SPS beam dump that was installed in one of the long straight sections of the SPS during the 2019–2020 shutdown of CERN’s accelerator complex within the framework of the Large Hadron Collider Injectors Upgrade Project. This new beam dump has been in the operation since May 2021, and it is foreseen that it will operate with a lifetime of 20 years. The key challenges in the design of the beam dump were linked to the high levels of thermal energy to be dissipated—to avoid overheating and damage to the beam dump itself—and high induced levels of radiation, which have implications for personnel access to monitor the beam dump and repair any problems occurring during operation. The design process, therefore, included extensive thermomechanical finite-element simulations of the beam-dump core and its cooling system’s response to normal operation and worst-case scenarios for beam dumping. To ensure high thermal conductivity between the beam-dump core and its water-cooling system, hot isostatic pressing techniques were used in its manufacturing process. A comprehensive set of instrumentation was installed in the beam dump to monitor it during operation and to cross-check the numerical models with operational feedback. The beam dump and its infrastructure design were also optimized to ensure it can be maintained, repaired, or replaced while minimizing the radiation doses received by personnel. Published by the American Physical Society 2024

Radiological safety assessment for transportation of reactor pressure vessel during decommissioning of a nuclear power plant in Korea

In Korea, decommissioning of nuclear power plants and transportation of the decommissioning waste are expected to expand in the near future. It is necessary to confirm that radiological risks to the public and workers are not significant through radiological safety assessment. The objective of this study is to assess the radiological safety for transportation of RPV waste, which is a major decommissioning waste with relatively high level of radioactivity. It was assumed that the waste would be transported to the Gyeongju disposal facility by land transportation. First, the source term and transportation method of the RPV waste were determined, and the external dose rates from the waste were calculated using MCNP. Then, transportation scenarios were assumed under both normal and accident conditions. Under the scenarios, radiation doses were calculated using the RADTRAN. Under normal operation scenarios without a transportation accident, assuming 40 shipments per year, the average individual doses for the public ranged from 6.56 × 10−6 to 2.18 × 10−2 mSv yr−1. The maximum individual doses for only a single shipment ranged from 2.43 × 10−6 to 3.14 × 10−1 mSv. For cargo handlers and vehicle crew members, the average doses were 2.26 × 101 mSv yr−1 and 2.95 mSv yr−1, respectively. Under transportation accident scenarios, average individual radiological risks which are product of the radiation doses and the annual accident rates ranged from 1.14 × 10−11 to 1.61 × 10−10 mSv yr−1 by transportation route segment when considering the transportation accident rate. Average individual doses assuming transportation accident occurrence ranged from 2.62 × 10−4 to 1.42 × 10−3 mSv. The maximum individual dose under accident conditions was 7.99 × 10−2 mSv. The calculated doses were below the regulatory limits in Korea. However, relatively high doses were observed for cargo handlers and vehicle crew members because of conservative assumptions. This study results can be used as basic data for the radiological safety assessment for the decommissioning waste transportation in the future.

Radiological hazard assessment for human from nuclear power plant effluent released under normal operation scenario (hypothetical case study)

This paper presents an assessment of the radiological hazard for humans from nuclear power plant effluent released into a river under normal operation scenarios (NOS). A hypothetical case study was conducted to estimate the annual effective dose (AED) received by the general public due to the discharge of effluent from the nuclear power plant. The results indicate that the radiological hazard for humans from nuclear power plant effluent released under (NOS) is minimal. The estimated AED received by the general public was found to be below 0.1 mSv/year, which is well below the annual dose limit of 1 mSv/y set by the International Commission on Radiological Protection (ICRP). The excess lifetime cancer risk (ELCR) detected remained within acceptable limits. These results estimated that nuclear power can be a safe and reliable source of energy when operated in accordance with established safety protocols. The study revealed that the concentration of 137Cs in sediments was higher than that of other radionuclides studied, leading to increased potential hazards over time. Overall, this study provides valuable information on the radiological hazard associated with nuclear power plant effluent released into a river under (NOS), which can be useful in the development of radiation protection strategies for nuclear power plants and in the communication of the risks associated with nuclear power to the public.

Transient fuel behavior analysis of UN fuel with a two-layered SiC cladding based on multiphysics method

Recently, UN fuel has emerged as a promising alternative to UO2 fuel due to its exceptional thermophysical attributes, including heightened thermal conductivity, elevated melting point, and increased fissile density. Meanwhile, SiC is recognized as a member of the next generation of accident-tolerant cladding materials owing to its impressive strength at high temperatures, resistance to creep, minimal thermal expansion, and improved irradiation characteristics. In this study, utilizing our developed fuel performance analysis code CAMPUS, we integrate a multiphysics model featuring UO2 fuel paired with a two-layered SiC cladding into the CAMPUS framework. Subsequently, we conduct simulations and analyses of the fuel performance for combinations such as UO2-two-layered SiC, UN-two-layered SiC, UN-Zircaloy, and UO2-Zircaloy. These evaluations encompass both standard operation scenarios and potential accident conditions within a pressurized water reactor (PWR). Notably, the incorporation of UN fuel demonstrates a significant reduction in maximum fuel temperature during normal operation, as well as under Loss-of-Coolant Accident (LOCA) and Reactivity Initiated Accident (RIA) conditions. However, upon introducing the two-layered SiC cladding, it becomes apparent that its temperature performance is somewhat inferior to that of Zircaloy under normal operation and RIA scenarios. Conversely, when subjected to a LOCA scenario, the thermal and mechanical characteristics of the two-layered SiC cladding outperform those of the Zircaloy cladding.

Research on the virtual coupling scenario of the CBTC system based on vehicle-to-vehicle communication

In order to simplify trackside equipment and realize shorter travel intervals, this paper proposes a virtual coupling CBTC system. The system structure, key technology, and train function module of the virtual coupling CBTC system scheme are analyzed. This paper also analyzes the system operation in the normal and fault operation scenarios and gives suggestions on the safety measures taken in the fault scenario, which provides reference for the engineering application of the system. It is found that the virtual coupling operation based on vehicle-to-vehicle communication can effectively reduce the operation cost and improve the operation efficiency.

Exploratory Thermo-Mechanical Assessment of the Bottom Cap Region of the EU DEMO Water-Cooled Lead Lithium Central Outboard Blanket Segment

The Water-Cooled Lead Lithium (WCLL) Breeding Blanket (BB) is one of the two BB concept candidates to be selected as the driver blanket for the EU DEMO fusion reactor. In this regard, the development of a sound architecture of the WCLL Central Outboard Blanket (COB) Segment, ensuring the fulfilment of the thermal and structural design requirements, is one of the main goals of the EUROfusion consortium. To this purpose, an exploratory research campaign has been launched to preliminarily investigate the thermo-mechanical performances of the Bottom Cap (BC) region of the WCLL COB segment because of its peculiarities making its design different from the other regions. The assessment has been carried out considering the nominal BB operating conditions, the Normal Operation (NO) scenario, as well as a steady-state scenario derived from the in-box LOCA accident, the Over-Pressurization (OP) scenario. Starting from the reference geometric layout of the WCLL COB BC region, a first set of analyses has been launched in order to evaluate its structural performances under a previously calculated thermal field and to select potential geometric improvements. Then, the analysis of a complete BC region was conducted from both the thermal and structural standpoints, evaluating its structural behaviour in compliance with the RCC-MRx code. Finally, after some iterations and geometric updates, a promising geometric layout of the BC region has been obtained even though some criticalities still persist in the internal Stiffening Plates and First Wall. However, the obtained results clearly showed that the proposed layout is worthy to be further assessed to achieve a robust enough configuration. The work has been performed following a theoretical-numerical approach based on the Finite Element Method (FEM) and adopting the quoted Ansys commercial FEM code.

Incorporating catastrophe insurance in power distribution systems investment and planning for resilience enhancement

Severe damage and high economic losses caused by frequent extreme disasters are becoming unbearable for distribution system operators (DSOs) under climate change. In order to cope with extreme disasters, this paper proposes an investment portfolio and planning framework of multi-resource for resilience enhancement. In the investment portfolio and planning framework, insurance is incorporated to mitigate high economic losses as a risk sharing and resilience enhancement supplementary strategy, and co-optimized with security investment from the perspective of DSOs. Firstly, the insurance investment is modelled based on Gordon-Loeb model according to insurance industry principles and formulated as constraints by piecewise linearization techniques. Secondly, the investment portfolio and planning framework proposed in this paper is modeled as a scenario-based two-stage stochastic mixed integer linear optimization program (MILP). In the first stage, DSO makes investment and planning decisions including energy storage (ESS) allocation, line hardening strategy and insurance investment. Both operation strategies of normal operation scenarios and extreme disaster scenarios under climate change are optimized in the second stage. Finally, progressive hedging (PH) algorithm is applied to solve the two-stage stochastic MILP model. The proposed model and algorithm are tested on the modified IEEE 33-bus test system. The results verify the validity of investment portfolio and planning framework, and the results show that portfolio investment considering insurance can realize resilience enhancement in both load shedding and economic losses.

A Method for Optimal Allocation of Distributed PV and Energy Storage Based on High Reliability of Distribution Network

In the context of the current widespread application of distributed PV, the energy storage system has bi-directional power characteristics and flexible regulation capability, and the reasonable joint planning of the two can enhance the safe and reliable operation of the system. In order to maximize long-term economic benefits, this paper proposes an optimal allocation method of distributed PV and energy storage based on high reliability of distribution network. Considering both normal operation and disaster scenarios for distributed photovoltaic storage planning, firstly, the investment and operation cost of distributed energy storage system is the target, and the storage planning model under normal operation scenario is established by considering the storage access location, configuration capacity, load state and grid operation state as constraints; then, the distributed photovoltaic storage optimal configuration model under disaster scenario is established by taking grid economy as the objective function. In summary, a two-layer planning model is established, with the upper layer using genetic algorithm to optimize the location, power and capacity of energy storage configuration, and the lower layer using particle swarm algorithm combined with tide calculation tool to optimize the intra-day operation strategy of energy storage; finally, the feasibility and effectiveness of the optimal configuration method are verified.

Optimising Airport Ground Resource Allocation for Multiple Aircraft Using Machine Learning-Based Arrival Time Prediction

Managing aircraft turnaround is a complex process due to various factors, including passenger handling. Airport ground handling, resource planning, optimal manpower, and equipment utilisation are some cost-cutting strategies, particularly for airlines and ground handling service teams. Scheduled aircraft arrival and departure times are critical aspects of the entire ground management and passenger handling process. This research aimed to optimise airport ground resource allocation for multiple aircraft using machine learning-based prediction methodologies to enhance the prediction of aircraft arrival time, an uncontrollable variable. Our proposed models include a multiple linear regression (MLR) model and a multilayer perceptron (MLP)-based model, both of which are used for predicting round-trip arrival times. Additionally, we developed a MLP-based model for multiclass classification of arrival delays based on departure time and delay from the same airport. Under normal weather conditions and operational scenarios, the models were able to predict round-trip arrival times with a root mean squared error of 8 min for each origin–destination pair and classify arrival delays with an average accuracy of 93.5%. Our findings suggest that machine learning-based approaches can be used to predict round-trip arrival times based on the departure time from the same airport, and thereby accurately estimate the number of actual flight movements per hour well in advance. This predictability enables optimised ground resource planning for multiple aircraft based on constrained airport resource deployment and utilisation.

Estimation of the power dissipation on the casing of DTT toroidal field coil during a fast plasma disruption

The aim of this paper is the computation of the power dissipated on the Toroidal Field Coil (TFC) casing of the Divertor Tokamak Test facility (DTT). The DTT Tokamak will be installed in Fascati (Italy), and is in an advanced design stage. The magnetic system will be realized with superconducting coils so that the correct dimensioning of the cooling system is mandatory. As a consequence, a detailed knowledge of the main sources of dissipation is required. Our attention will here be focused on the TFC casing and, in particular, on the dissipations due to the eddy currents induced on the casing by time-varying magnetic field during a Fast Plasma Disruption (FPD). A finite element model whose geometry has partly been imported into Ansys 2021/R2 SpaceClaim (TFC casing), and partly made in Ansys 2021/R2 DesignModeler (plasma, Vacuum Vessel (VV) and Stabilizing Plates (SP)), has been implemented in Ansys 2021/R2 Maxwell 3D to perform a transient analysis of the FPD event. The current induced on the TFC casing, as well as the total power losses, are the output of our computation to be used for the cooling system dimensioning. In order to estimate the heat rate to be removed during normal operation, the breakdown and Single Null (SN) scenarios have also been studied.

COMPASS-U Global Heat Balance Calculations

COMPASS-U is a medium size, high magnetic field experimental tokamak ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R =0.9$ </tex-math></inline-formula> m, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{t} = 5$ </tex-math></inline-formula> T, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{p} = 2$ </tex-math></inline-formula> MA), built at the Institute of Plasma Physics, Czech Academy of Sciences (IPP-CAS). This global heat balance calculation for COMPASS-U was done at Princeton Plasma Physics Laboratory (PPPL). Based on our previous experience of building global thermal model for National Spherical Torus Experiment-Upgrade (NSTX-U) at PPPL, this 2-D global thermal model geometry represents a typical cross section of COMPASS-U machine. The model includes thermal radiation, conduction, and convection among components and also between the machine and outer environment. Helium gas heating/cooling was modeled with fluid element and surface element. This model was used to calculate component temperatures and heat distribution during heat up, cryogenic cool down, normal operation, and fault operation scenarios. Definition of 14 main thermal scenarios was provided by IPP-CAS. First nine are normal operation scenarios. Scenarios #10–#14 are fault scenarios. Some results of thermal scenario #5 will be given and discussed in this article, including peak temperatures, temperature ratcheting, energy distribution, and required cooling power.

Developing PCC and DCC integral effects test experiments at the High Temperature Test Facility

Among the Next-Generation Nuclear Plant (NGNP) designs, the High-Temperature Gas-Cooled Reactors (HTGRs) are very attractive, due to their inherent safety features, high power conversion efficiency, and potential of providing high-temperature process heat. To perform a thorough safety study and to license these types of reactors, sufficient information needs to be provided about the phenomena that occur during accident scenarios. While several experimental research efforts have been dedicated in the past to investigate accident scenarios, knowledge gaps still exist in the phenomena characteristic of pressurized and depressurized conduction cooldown (PCC/DCC) transients as well as for normal operation scenarios. This paper summarizes the Oregon State University High Temperature Test Facility (HTTF) test matrix, experimental campaign, and selected tests results. High Temperature Test Facility is a scaled Integral Test Facility (IET) that is capable of mimicking scaled dimensions and operational conditions of the Modular High-Temperature Gas Cooled Reactor (MHTGR). The goal of the High Temperature Test Facility is to provide experimental data on the DCC, PCC and normal operating scenarios of the reference Modular High-Temperature Gas Cooled Reactor design. The DCC, PCC, mixing, heat up and cooldown tests described in this paper were performed at prototypical Modular High-Temperature Gas Cooled Reactor temperatures, scaled initial pressure conditions (∼200 kPa), and thermal power input of less than 70 kW. Presented test data show temperature distributions in the High Temperature Test Facility core, upper plenum, cross duct, or lower plenum. Based on these temperature profiles attempts to investigate stratified flow, natural convection flow, heat up, cooldown and mixing phenomena are made. Furthermore, this paper evaluates the performed test campaign in the light of the Very High Temperature Gas-cooled Reactor Phenomena Identification and Ranking Table (PIRT) and proposes experiments to complement the existing PCC/DCC testing database for the validation of the thermal-hydraulic codes.

Radiological safety analysis of a newly designed spent resin mixture treatment facility during normal and abnormal operational scenarios for the safety of radiation workers

The radiological safety of workers in a newly developed microwave-based spent resin treatment facility was assessed based on work location and operational scenarios. The results show that the remote-operation room worker was exposed to maximum annual dose of 3.19E+00 mSv, which is 15.9% of the dose limit, thereby confirming radiological safety. Inside the pathway, annual doses in the range of 7.87E-02–2.07E-01 mSv were measured initially at the mock-up tank and later at the point between the spent resin separation and treatment parts. The dose of emergency maintenance workers was below the dose limit (4.08E-03–4.99E+00 mSv); however, before treatment (separation and microwave), the dose of maintenance and repair workers exceeded the dose limit. The doses of the effluent removal workers at the zeolite and activated carbon storage tank and spent resin storage tank were the lowest at 2.79E-01–2.87E-01 mSv and 9.27E-01 mSv in “1 h” and “4–5 h of operation”, respectively. The immediately lower and upper layers of the facility room exhibited the highest annual doses of 1.84E+00 and 3.22E+00 mSv, respectively. Through this study, a scenario that can minimize the dose considering the movement of spent resin through the facility can be developed.

Short-Circuit Analysis of AC Distribution Systems Dominated by Voltage Source Converters Considering Converter Limitations

This paper deals with the short-circuit analysis of distribution systems dominated by Voltage Source Converters (VSCs). A novel methodology has been proposed in this paper for short-circuit calculation of power systems populated with VSCs where the control modes and potential current-saturated operation of power converters are considered. The studied distribution system has been modeled using an element-based steady-state formulation that includes the converter equations in both normal operation and fault scenarios. Then, equilibrium points of the studied distribution system are identified by solving the established systems of equations for different potential current-saturation states of the VSCs. The methodology identifies possible solutions involving different saturation states of different converters. The proposed methodology is applied to a specific case study of a distribution system penetrated with VSCs in both grid-forming and grid-following control. The short-circuit analysis results indicate that VSCs operation shows a significant impact on the short-circuit equilibrium points of the studied system. In addition, multiple equilibrium points may exist depending on whether the grid-forming converter is saturated or not. The existence of multiple equilibrium points is validated through dynamic simulations.

Evaluation of Metro Station Design in Terms of Normal Operation and Emergency Evacuation Scenarios with 3D Simulation Software

Yaya simülasyonu teknolojilerinin mimarlık ve şehir planlama disiplinlerinde kullanımı yeni bir kavram olmamakla birlikte; makine öğrenmesi tabanlı, insan davranışlarına benzer sonuçlar veren, ajan bazlı, gerçekçiliği ve geçerliliği bilimsel olarak ispatlanmış üç boyutlu simülasyon yazılımları son yıllarda ortaya çıkmışlardır. Bu yazılımlar, özellikle kalabalık ve karmaşık mekanlarda ortaya çıkabilecek sirkülasyon ve acil durum tahliye problemlerinin henüz tasarım aşamasındayken görülmesine olanak sağlamakta; bu sayede yapı inşa edilmeden önce projede gerekli revizyonların gerçekleştirilmesine imkan vermektedir. Ulusal ve uluslararası standartlar doğrultusunda gerçekleştirilen bu çalışmanın amacı, güncel simülasyon teknolojilerinin yapılara ilişkin normal işletme ve acil durum tahliye senaryolarının değerlendirilmesinde kullanımını örnek olarak seçilen gerçek bir metro istasyonu projesi üzerinden incelemektir. Seçilen raylı sistem hattındaki istasyona özgü yolcu yüklerinin bulunması amacıyla klasik elle hesaplama yöntemleri kullanılmış, ortaya çıkan değerler Massmotion yazılımına aktarılarak mekânsal kapasite analizleri gerçekleştirilmiş ve istasyonun tüm katlarına ilişkin hizmet seviyeleri bulunmuştur. Sonuç olarak metro istasyonunun normal işletme ve acil durum tahliye senaryolarının gereksinimlerini karşılayıp karşılamayacağı test edilmiş, ortaya çıkan sonuçlar çalışma kapsamında verilmiştir.

Gray Wolf Optimization for Scheduling Irrigation Water

Although various optimization algorithms have been developed for operational purposes, the development of new optimization algorithms is still an open problem due to the complex system of irrigation canals that must be addressed. Recently, a new algorithm named gray wolf optimization (GWO) has been introduced and applied in different contexts. It mimics the social hierarchy and hunting behavior of gray wolves in nature. In this research, GWO was formulated, developed, and linked to irrigation canal system simulation (ICSS) to schedule water delivery. A fitness (optimization) function was defined according to the standard water delivery performance indicators. Normal and water shortage operational scenarios in the E1R1 Dez canal in Iran were tested and evaluated. The results revealed that GWO is a powerful optimization method and avoids local optimal points when normal conditions exist. However, it has relatively poor performance in water shortage conditions in which there is not enough water. Water depth variations remain inside acceptable margins. Its results were comparable to fuzzy state, action, reward, state, action (SARSA) learning (FSL) in the same canal, showing a value of maximum absolute error (MAE) and integral absolute error (IAE) of 10.7% and 9.2%, respectively, and it can distribute water between turnouts adequately, efficiently, equitably, and dependably in normal conditions.

Coupled simulations for prismatic gas-cooled reactor

The development and deployment of gas-cooled reactors (GCRs) require flexible modelling and simulation tools for a detailed understanding of the system behavior in normal operation and accidental scenarios. Amongst the identified safety-relevant scenarios for the gas-cooled reactors, outlet plenum flow distribution during normal operations was ranked to be of high importance with a low knowledge level in the phenomenon identification and ranking table (PIRT). The present paper contributes to the development of accurate simulation models using stand-alone and coupled codes for the GCR lower plenum region, which are needed to address nuclear reactor safety issues early enough so that delays in licensing and facility construction can be minimized. For the first time in this paper, an assessment of the predictive capabilities of coupled system-thermalhydraulics and CFD codes against heat transfer measurements in the lower plenum of a prismatic block GCR is reported. The lower plenum mixing experiments of the integral high temperature test facility at the Oregon State University (OSU HTTF) were simulated in the stand-alone and coupled mode to predict the lower plenum mixing. The coupled-code analysis used a 3D CFD code STAR-CCM + and a 1D thermalhydraulics code RELAP5-3D to account for system-level feedback on the flow and heat transfer for lower plenum mixing occurring during the normal operation at the reduced power and/or mass flow rate. For one of the simulated OSU test conditions, the existing models in STAR-CCM + and RELAP5-3D predicted the measured core temperatures reasonably well at two different elevations, suggesting that the available models are adequate for such an analysis. Through this study, a better understanding of the suitability of the models in the CFD and system thermalhydraulics (TH) codes is gained for more accurate prediction of flow and heat transfer in GCRs in anticipation of the eventual need to perform safety and licensing analyses.