bluuebunny/crossref_metadata_2025 huggingface dataset:
Endoscopic findings after CT proven acute diverticulitis: a systematic review and meta‐analysis
Authors: Cao Amy Millicent Yesheng , Lam Vincent Wai , Rickard Matthew John Francis Xavier
Published: December 2022

Background

Traditionally, international guidelines recommend patients with acute diverticulitis should be followed up with a colonoscopy 6–8 weeks after discharge. However, the need for an interval colonoscopy has been increasingly challenged in the setting of computed tomography (CT). Previous meta‐analyses have included studies which combined suspected rather than imaging confirmed diverticulitis and often without correlation with endoscopic findings. This meta‐analysis aims to investigate endoscopic findings of patients with CT confirmed diverticulitis.

Methods

An electronic search of Medline, PubMed, Cochrane Library, Embase, CINAHL, Web of Science, Scopus, Clinicaltrials.gov and WHO ICTRP was performed up to October 18, 2021. Studies which reported CT confirmed acute diverticulitis in adults and who underwent endoscopic follow‐up with either a colonoscopy or flexible sigmoidoscopy were included. Studies were excluded if diverticulitis was diagnosed by clinical grounds alone, ultrasound, barium enema, or other non‐CT forms of imaging.

Results

A total of 68 studies with 13 905 patients were included. Median age was 58 years and male to female ratio was 0.84. Cancer was detected in 2.0% and advanced adenoma in 3.8%. Complicated diverticulitis had 9.2 higher odds of cancer compared to uncomplicated diverticulitis (95% CI 4.42–19.08, P < 0.001). Adenomas were detected in 17%. Of those diagnosed with colorectal cancer, 85% were concordant with the site of the diverticulitis on CT while 15% were incidental findings.

Conclusion

Routine colonoscopic follow up should be recommended in medically fit patients who have CT proven acute diverticulitis due to the higher than population prevalence of colorectal cancer and advanced adenomas.
Apatite Reference Materials for SIMS Microanalysis of Isotopes and Trace Elements
Authors: Kennedy Allen K. , Wotzlaw Jörn‐Frederik , Crowley James L. , Schmitz Mark , Schaltegger Urs , Wade Benjamin , Martin Laure , Talavera Cristina , Ware Bryant , Bui Thi Hao
Published: December 2022

Twelve apatite samples have been tested as secondary ion mass spectrometry (SIMS) reference materials. Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) analysis shows that the SLAP, NUAN and GR40 apatite gems are internally homogeneous, with most trace element mass fractions having 2 standard deviations (2s) ≤ 2.0%. BR2, BR5, OL2, AFG2 and AFB1, which have U > 63 μg g‐1, 206Pb/204Pb > 283, and homogeneous SIMS U‐Pb data, have respective isotope dilution thermal ionisation mass spectrometry (ID‐TIMS) ages of 2053.83 ± 0.21 Ma, 2040.34 ± 0.09 Ma, 868.87 ± 0.25 Ma, 478.71 ± 0.22 Ma and 473.25 ± 0.09 Ma. Minor U‐Pb heterogeneity exists and accurate SIMS results require correction with the 3D Concordia‐constrained common Pb composition. Among the studied samples, AFG2 and BR5 are the most homogeneous U‐Pb reference materials. The SIMS sulfur isotopic compositions of eight of the apatites shows they are homogeneous, with 2s for both 103δ34S and 103δ33S < 0.55‰. One apatite, BR96, has Δ33S = ‐0.36 ± 0.2‰. The apatite samples have ID‐TIMS 87Sr/86Sr between 0.704214 ± 0.000030 and 0.723134 ± 0.000035.
Farnesyl/geranylgeranyl diphosphate synthases regulate the biosynthesis of alarm pheromone in a unique manner in the vetch aphid Megoura viciae
Authors: Song Xuan , Qin Yao‐Guo , Zhang Yi‐Han , Zhou Yu‐Bei , Li Zheng‐Xi
Published: December 2022

Farnesyl/geranylgeranyl diphosphate synthases (FPPS/GGPPS) as the short‐chain prenyltransferases catalyse the formation of the acyclic precursors (E)‐FPP and (E)‐GGPP for isoprenoid biosynthesis. Here, we first cloned the cDNAs encoding FPPS and GGPPS in the vetch aphid Megoura viciae (designated as MvFPPS and MvGGPPS). They had an open reading frame of 1185 and 930 bp in length, encoding 395 and 309 amino acids, with a theoretical isoelectric point of 6.52 and 6.21, respectively. Sequence alignment and phylogenetic analysis showed that MvFPPS and MvGGPPS shared the conserved aspartate‐rich motifs characterized by all prenyltransferases identified to date and were clustered with their homologues in two large clades. RNA interference (RNAi) combined with gas chromatography/mass spectrometry (GC–MS) analysis showed that both MvFPPS and MvGGPPS were involved in the biosynthesis of alarm pheromone. Spatiotemporal expression profiling showed that the expression of MvFPPS and MvGGPPS was significantly higher in embryos than in other tissues. RNAi and GC–MS performed specifically in embryos corroborated the function of MvFPPS and MvGGPPS. In vitro, enzymatic activity assay and product analysis demonstrated that MvFPPS could catalysed the formation of (E)‐FPP using DMAPP or (E)‐GPP as the allylic cosubstrates in the presence of IPP, while MvGGPPS could only use (E)‐GPP or (E)‐FPP as cosubstrates. Functional interaction analysis using RNAi revealed that MvGGPPS exerts unidirectional functional compensation for MvFPPS. Moreover, it can regulate the biosynthesis of alarm pheromone by imposing a negative feedback regulation on MvFPPS. Our study helps to understand the molecular regulatory mechanism of terpenoid biosynthesis in the aphid.
Using thePDCAcycle to uncover sources of mental health disparities for Hispanics
Authors: Moyce Sally , Claudio David , Velazquez Maria
Published: December 2022

The Hispanic population is growing rapidly in U.S. rural states, yet limitations in Spanish‐speaking behavioural health providers are a barrier to accessing care. In Montana, a new immigrant destination, mental health disparities may not yet be fully understood. We describe an interprofessional approach of nurses and engineers using the Plan‐Do‐Check‐Act (PDCA) cycle to identify disparities in mental health access in a Hispanic community in a rural state. We recruited a community advisory board to inform researchers about potential disparities and to design interventions. The Plan phase consisted of naming the problem and its root causes. Researchers and a community advisory board created flowsheets and diagrams to uncover personal, environmental, political, and procedural contributors to poor mental health outcomes. The Do phase included implementation of a community screening for depression and anxiety. The Check phase revealed 43 mental health screenings where 21% screened positive for depression and 16% screened positive for anxiety. We made 16 referrals to a mental health intervention study. The Act phase led to plans for regular implementation of the health fairs and a study designed to provide Spanish‐language mental health services. The success of our interprofessional work provides an example of how the PDCA cycle can be used to uncover potential causes for poor health outcomes and design and evaluate interventions targeted to mitigate those outcomes.
Experiences of discrimination or violence and health outcomes among Black, Indigenous and People of Colour trans and/or nonbinary youth
Authors: Chan Ace , Pullen Sansfaçon Annie , Saewyc Elizabeth
Published: December 2022

Aims

Identify the relationship between experiences of discrimination or violence and health outcomes for transgender and nonbinary Black, Indigenous and People of Colour (BIPOC) compared to their white trans and nonbinary peers.

Design

A national online survey, the 2019 Canadian Trans and Nonbinary Youth Health Survey, was conducted among youth ages 14–25, in English and French.

Methods

Participants were recruited from November 2018 to May 2019 (N = 1519). BIPOC youth comprised 25.7% of the sample (n = 390). Questions about six types of discrimination (e.g. racism and sexism) and violence (physically threatened or injured), plus foregone health care, self‐harm and suicidality were drawn from existing validated measures. Analyses involved cross‐tabulations with chi‐square tests and logistic regressions.

Results

Trans and non‐binary BIPOC reported significantly higher prevalence of suicide attempts (24.9% vs. 19.5%) and violence victimization compared to white youth. They had significantly higher odds of self‐harm and foregone health care when experiencing discrimination by ethnicity or culture. All types of violence were significantly associated with higher odds of foregone physical health care, self‐harm, suicide ideation and suicide attempt.

Conclusion

In Canada, trans and nonbinary youth who are BIPOC face disparities in health outcomes and experiences of violence and discrimination compared to white trans and nonbinary youth.

Impact

Nurses should assess for violence exposure and discrimination among trans and/or nonbinary youth of colour, and promote health equity by advocating for policies to reduce violence and discrimination, including racism, for trans and nonbinary young people.
Catalytic Power Europe: Blended Finance in European External Action
Authors: Prontera Andrea , Quitzow Rainer
Published: December 2022

The global influence of the European Union (EU) has been debated in overlapping strands of literature as ‘normative’, ‘regulatory’ and ‘market power’. They identify the diffusion of its rules and standards as a vehicle of European power. We argue that European power extends beyond its regulatory capacities and includes new ‘catalytic’ capacities in the realm of financing and network building. We analyse blended finance as an instrument of ‘catalytic power’, defined as the mobilisation of partners and their resources to pursue external objectives. The analysis reveals that financial leverage, the original motivation behind the tool's creation, has declined in importance. Instead, blended finance is designed to facilitate and structure cooperation with other European and multilateral financial institutions, positioning the European Commission as a central node in international cooperation and increasing its influence in this sphere. The article closes with a discussion of blended finance as a tool of catalytic power and related trade‐offs.
The Model Strategy of Offering Microtakaful under Perlindungan Tenang Initiative/ Model Strategi Penawaran Takaful Mikro di bawah Inisiatif Perlindungan Tenang
Authors: Kamal Asiah , Sulaiman @ Mohamad Ahmad Azam , Mohamad Mohammad Taqiuddin
Published: December 2022

This article discusses the strategy of offering microtakaful under Bank Negara Malaysia (BNM) is an initiative named “Perlindungan Tenang", there are three takaful companies are participating in this initiative. Therefore, this study was conducted on BNM and three takaful companies to look at the micro takaful offering strategies. This study used qualitative methods that conducted interviews with Bank Negara Malaysia (BNM) and the three Takaful companies involved. Then, the data are analysed using thematic analysis, which discusses the theme of product design, participation response, distribution channel, participation method, physical product offering, contribution payment method, and product promotion method. Besides, the analysis in this study also used comparative analysis to compare the strategies of offering micro takaful with three takaful companies and documentation analysis involving analysis of journals, books, conference papers, and websites related to corroborate the findings of the analysis. The results of the analysis found that the takaful product coded as product C has the best strategy in terms of the first aspect, a simple product design. Second, the response to participation was so good that group offerings had to be discontinued. Third, the method of offering in collaboration with Agro Bank branches throughout the state. Fourth, participatory methods are offered individually and in groups. Fifth, the physical offer products in the form of cards when joining the scheme. Sixth, the method of payment of contributions at Agro Bank branch counters for individual participation and group participation can be paid to the head or representative. Lastly seventh, the method of promoting the product is offered in collaboration with Agro Bank to customers who deal directly or indirectly with the customers of this bank. Overall, this study can produce a micro takaful offering strategy model that has the characteristics and advantages of product design, supply channel strategy and product promotion method, supply method strategy, and payment method as well as product physical strategy after a comparative analysis of the three products. offering takaful products under this initiative.
The Ease of Use of Google Classroom Technology Among Secondary School Teachers in Malaysia/ Kemudahan Penggunaan Teknologi Google Bilik Darjah Dalam Kalangan Guru Sekolah Menengah Di Malay
Authors: Rodin Ahmad Rozeman , Hassan Zainudin , A Wahab Nor Hidayah
Published: December 2022

Implementation of the Movement Control Order (MCO) Policy in Malaysia requires the cooperation of all parties including teachers and parents to implement Home Teaching and Learning (PdPR) and one of the famous learning mediums today is that Google classroom an application makes it easier for teachers to create, distribute and review student assignments without using papers. This study aims to study the facilitation and harness of google classroom technology among teachers as well as the teacher's true attitude and behavior towards the use of google classroom. In the study, studiers used qualitative methods by semi-structured interviews to collect data and study information. Coding methods have been used to analyze the findings. The samples were intended to be used to select respondents according to the appropriate criteria set by the reviewer. The sample consisted of six teachers, including five female teachers and one male teacher of secondary school in Johor Bahru, Malaysia. The results showed that teachers gave a positive insight into google classroom as a simplifying, flexible and safe-to-use technology. They also acknowledge that google classrooms can improve the effectiveness of teacher's work performance, help them diversify learning materials and be able to actively interest in the learning process. Teachers express google classroom technology which is satisfactory and enjoyable as it can improve the productivity and performance of teachers while enhancing technological usage skills than ever before. It is suggested that teachers need to be creative and innovative in diversifying teaching and learning techniques to ensure that their teaching and learning is more attractive through the exploration of various interesting functions in this application.
Exogenous ketone supplementation: an emerging tool for physiologists with potential as a metabolic therapy
Authors: Falkenhain Kaja , Islam Hashim , Little Jonathan P.
Published: December 2022

Exogenous oral ketone supplements, primarily in form of ketone salts or esters, have emerged as a useful research tool for manipulating metabolism with potential therapeutic application targeting various aspects of several common chronic diseases. Recent literature has investigated the effects of exogenously induced ketosis on metabolic health, cardiovascular function, cognitive processing, and modulation of inflammatory pathways and immune function. This narrative review provides an overview of the integrative physiological effects of exogenous ketone supplementation and highlights current challenges and future research directions. Much of the existing research on therapeutic applications – particularly mechanistic studies – has involved pre‐clinical rodent and/or cellular models, requiring further validation in human clinical studies. Existing human studies report that exogenous ketones can lower blood glucose and improve some aspects of cognitive function, highlighting the potential therapeutic application of exogenous ketones for type 2 diabetes and neurological diseases. There is also support for the ability of exogenous ketosis to improve cardiac metabolism in rodent models of heart failure with supporting human studies emerging; long‐terms effects of exogenous ketone supplementation on the human cardiovascular system and lipid profiles are needed. An important avenue for future work is provided by research accelerating technologies that enable continuous ketone monitoring and/or the development of more palatable ketone mixtures that optimize plasma ketone kinetics to enable sustained ketosis. Lastly, research exploring the physiological interactions between exogenous ketones and varying metabolic states (e.g., exercise, fasting, metabolic disease) should yield important insights that can be used to maximize the health benefits of exogenous ketosis.
Power Performance and Response Analysis of a Semi-Submersible Wind Turbine Combined With Flap-Type and Torus Wave Energy Converters
Authors: Lee Chern Fong , Tryfonidis Christodoulos , Ong Muk Chen
Published: December 2022

An integrated offshore wind and wave energy system is an attractive concept in areas with abundant wind and wave energy resources. The sharing of supporting platform and facilities, e.g., mooring systems, offers significant cost savings. This will effectively lower the levelized cost of energy (LCOE). In the present study, a conceptual design consisting of a braceless semi-submersible floating horizontal axis wind turbine (FHAWT), three flap-type wave energy converters (WECs), as well as a torus (donut-shaped) point absorber-type WEC is proposed. The flap-type WECs harvest wave energy through the flap motion caused by oscillating wave surge, while the torus WEC absorbs wave energy generated from its heaving motion. The absorbed mechanical power of the power take-off (PTO) systems is calculated based on linear damping forces and the motions of the WECs relative to the supporting platform. Hydrodynamic interaction between the WECs and the supporting platform is considered by including the coupling terms in the added mass and potential damping coefficient matrices. A fully coupled aero-servo-hydro-elastic numerical model of the concept is constructed. The feasibility study of the concept is carried out using time-domain simulations. Only operational environmental conditions are simulated based on simultaneous wind and wave hindcast data of a selected offshore site. The effects of the WECs on the wind turbine, platform motions, and WEC power take-off are examined. Based on the power performance of WECs, recommendations are also provided for optimum power absorption.
A Finite Element Approach to Solve Incompressible Navier-Stokes Equations and Its Convergence Rate Analysis
Authors: Lu Qiyue , Bao Shiyi
Published: December 2022

Finite element methods for fluid flow problems are gaining more interests in nuclear engineering fields in recent years. Based on linear triangle elements, this work implements the algebraic subgrid scale (ASGS) stabilized finite element model for solving advection dominated incompressible fluid flows. The non-linearity is handled by the fixed point iteration. Verification is carried out using the method of manufactured solutions (MMS) for convergence rate analysis and the unit square lid-driven cavity benchmark problem.
Development of a Numerical Simulation Method for Air Cooling of Fuel Debris by JUPITER
Authors: Yamashita Susumu , Uesawa Shinichiro , Yoshida Hiroyuki
Published: December 2022

It is known that fuel debris is widely spread inside the primary containment vessel (PCV) at the Fukushima Daiichi Nuclear Power Plant (1F) by on-site observations. To retrieve fuel debris reliably and safely, it will be required that an accurate understanding of where and how much fuel debris locates in the PCV and how high the temperature of fuel debris rises. However, the details of the circumstances are not yet fully understood, and due to the high radiation dose, on-site investigation of it still has a lot of difficulties. Instead of on-site investigations, numerical simulations may provide essential information for the accurate understanding of thermal behaviors, including melt relocation behaviors, effects of unsteady natural convection around fuel debris, and the detailed temperature distribution inside fuel debris.

We focus on the development of a detailed numerical simulation method for unsteady natural convection around fuel debris. JAEA has developed the detailed three-dimensional thermal-hydraulics code, JUPITER, which was originally developed for the melt relocation behavior of core internals in severe accidents. JUPITER has governing equations for incompressible fluids, i.e., equations of the Navier-Stokes, heat conduction, the advection of free interfaces, and solute transport. Because fuel debris may exist as a porous medium, in this study, we newly implemented the equation of porous medium model in JUPITER to calculate natural convection induced by a decay heat of fuel debris. We confirmed that JUPITER gives a reasonable result for the temperature of fuel debris as a porous medium.
Study on Evaluation Method of Radial Power Reference Distribution of PWR
Authors: Wei Ting , Huang Yu , Yue Zhidong , Zhang Ying
Published: December 2022

The selection of radial power reference distribution is an important prerequisite and basic component of reactor safety analysis. In this paper, the reference radial power of a large PWR is calculated and evaluated in detail from 1/4 core and 1/4 hot assembly based on large data, and the following conclusions are drawn: (1) Based on the batch programming calculation of simple random reconfiguration, the influence of 1/4 core power distribution on the minimum DNBR value is negligible. (2) Based on the power capability analysis bank and the three-dimensional core physical accidents banks of rod drop, uncontrolled RCCA withdrawal at subcritical condition, uncontrolled single control rod withdrawal, RCCA ejection, steam line break, the power distributions of 1/4 hot assembly reconstructed by extracting the rod power distributions are evaluated, and it is concluded that the reference radial power distribution has enveloping property. Based on a large amount of data, the reference distribution is studied and evaluated, and it is verified that it can envelop possible distributions to meet the needs of core safety evaluation. Through the above evaluation research, a method to determine the radial power reference distribution of PWR is obtained, which can be used by engineers when designing the reference radial power distribution.
A CFD Method for Thermal-Hydraulic Calculation of Pebble Bed HTGRs
Authors: Zhu Junbing , Chen Fubing
Published: December 2022

The high temperature gas-cooled reactor (HTGR) is an advanced reactor type with safety characteristics of Generation IV nuclear energy systems. In the design process of an HTGR, thermal-hydraulic analysis is of great significance. This paper reviews existing methods for thermal-hydraulic calculation of pebble bed HTGRs and proposes a method for the two-dimensional (2-D) simulation using the commercial computational fluid dynamics (CFD) software ANSYS FLUENT. The pebble bed reactor core, fluid flow zones and control rod channels in the reflector are modeled with a porous media approach, while user-defined scalar (UDS) is employed for solving the governing equations of solid temperature in these regions. To incorporate radiation heat transfer among outer surfaces of the porous media region as well as their viewable walls into the calculation, some heat sources in thin layers adjacent to the walls are innovatively added. The method is applied to the steady-state simulation of the 10 MW high temperature gas-cooled reactor-test module (HTR-10). The fuel temperature is far below the safety limit, and the temperature values of the reactor internals agree well with the experimental results, showing that the CFD method adopted in this study predicts the temperature distribution well. Since the effect of radiation heat transfer on the temperature distribution is fully considered, the method can be directly applied to the simulations and studies of some accident conditions.
Numerical Simulation of Annular Dispersed Flow in Simplified Subchannel of Light Water Cooled Fast Reactor RBWR
Authors: Yoshida Hiroyuki , Naoki Horiguchi , Ono Ayako , Furuichi Hajime , Katono Kenichi
Published: December 2022

About the boiling transition (BT) that determines the maximum thermal output of the BWR, it is considered that the spacers have significant effects on the occurrence of BT. In the light water cooled fast reactor: RBWR, thermal-hydraulics conditions are more severe than the current BWR. Then, the effect of the spacer on BT should be sufficiently utilized in the RBWR. The RBWR is still in the design stage, therefore is not reasonable to determine the shape of the spacer by evaluation only for large-scale tests. In the occurrence of BT, it is considered that the two-phase flow pattern is the annular dispersed flow, and we want to evaluate the effects of spacer shape on annular dispersed flow in RBWR subchannels. This research uses the detailed two-phase flow simulation code TPFIT to simulate annular dispersed flow in RBWR subchannels.

As the first step of this research, we performed numerical simulations of annular dispersed flow in the simplified subchannel of RBWR. We used a circular tube with the same hydraulic diameter as the RBWR subchannel to consider the basic effects of spacer on the annular dispersed flow. In this paper, we describe the result of numerical simulation. In addition, we evaluated droplets’ size and velocity based on simulation results for the spacer’s existence and non-existence cases.
Assessment of Multiphase CFD Method for PWR Fuel Rod Bundle
Authors: Ren Bing , Gan Fujun , Yang Ping , Zhang Jie
Published: December 2022

This paper presents the assessment of the computational fluid dynamics (CFD) methodology for simulating the boiling flow in the Pressurized Water Reactor (PWR) rod bundle. The method includes the Eulerian-Eulerian two-fluid model coupled with the improved wall heat partitioning model. The effects of key phenomenological models are investigated based on the experimental data of vertical pipes. Then the integral validation of the method is carried out based on the NUPEC PWR Subchannel and Bundle Test (PSBT) International Benchmark, including the single sub-channel experimental data, and the full length of a PWR fuel assembly with multiple 5 × 5 spacers grid experimental data. The results agree well with the experimental results, which indicate the promising application of the present method for modeling the boiling flow under high pressure. Based on the validated method, the three-dimensional boiling flow in the fuel rod bundle is investigated, including the rod surface temperature, the bulk fluid temperature and the void fraction.
CFD Analysis on the Small Module Reactor (ACP100) PRS Return Line Thermal Stratification Phenomenon
Authors: Peiying Li , Cai Zhiyun , Zhang Yulong , Liu Hang , Liu Minghao , Ye Zhu , Tao Shuchang , Liu Xianghong
Published: December 2022

The return line of the passive residual system (PRS) of ACP100 is connected to the direct injection nozzle of the pressure vessel. It is a non-isolated dead pipe containing coolant, and there is no insulation layer. The temperature difference between the two sides of the pipe is large, which is prone to thermal stratification. This paper uses FloEFD software to carry out CFD simulation analysis and research on the thermal stratification phenomenon of the pipeline in normal operation and accident conditions. The scope of the return line analysis in this paper begins with the isolation valve at the outlet and ends with the direct injection nozzle on the pressure vessel. The finite volume method is used to solve the model, and the standard k-ε two-equation model is used for turbulence simulation. The pipeline system adopts a mesh refinement strategy according to the flow channel and wall thickness in the pipeline to obtain a reasonable mesh distribution. The results show that during normal operation, there is obvious thermal stratification at the exit of the PRS isolation valves, and there is a certain vortex in the tube, which can promote the heat exchange between the reactor pressure vessel and the PRS return pipeline; When PRS put into operation, a large temperature gradient is generated at the interface of the annular cavity of the pressure vessel, and the influence of thermal stress and cyclic thermal shock needs to be considered, and an obvious vortex will be formed nearby to promote the rapid heat exchange of cold and hot water in the nearby area. The result of this paper can provide input for PRS return line thermal stress and thermal cycling impact analysis.
Study on the Applicability of a Machine-Learning Framework to Improve Modeling for the Stratification Phenomenon
Authors: Oda Takuo , Okayasu Shimpei , Hara Nobuhide , Tanimoto Koichi , Haghiri Ali , Xu Xiaowei , Sandberg Richard
Published: December 2022

In chemical plants, heat storage systems, nuclear power plants, etc., when hot water is injected into a tank containing cold water, mixing of hot and cold fluid is suppressed by buoyancy effects and thermal stratification can occur. This leads to the deterioration of heat storage capability and the effect of thermal stratification can adversely affect the structure. Therefore, a measure for eliminating thermal stratification was constructed and its effectiveness was examined by CFD analysis. Since the fluctuations in the gravity direction are suppressed by buoyancy in the thermal stratification field, the prediction accuracy becomes low when RANS based on the isotropic eddy viscosity hypothesis like the conventional k-ε model is used. Although the above phenomena can be predicted by performing a high-precision analysis such as LES analysis, the analysis cost becomes enormous and it is unsuitable for design evaluation. In this study, turbulent heat flux and anisotropic Reynolds stress were modeled using a Gene Expression Programming (GEP) framework. In the GEP framework of this study, a non-linear Reynolds stress relationship is constructed by adding non-linear terms to the linear Boussinesq approximation and the turbulent Prandtl number is expressed as a function of velocity and temperature gradients. This modeling is based on an LES dataset. RANS analysis was carried out using these two models on a test case different from the training case, and calculation results are compared with experimental test results. As a result, the decay of the thermal stratification phenomenon was reproduced with high accuracy. This paper introduces this new turbulence modeling process.
Virtual Design of Integrated Bottom Head Quenching Scheme
Authors: Wang Jing , Wang Xiaofang , Gu Jianfeng
Published: December 2022

CAP1000 reactor pressure vessel integrated bottom head was the integrated stamping molding of transition section and spherical bottom head forgings. The integrated bottom head forging was too deep, so it was difficult to control the quenching uniformity of head forgings opening and dome. In addition, the wall thickness of the integrated bottom head forgings was almost to 300mm. In order to make the forgings qualified performance, the overall quenching cooling effect of the forgings was need to be improved. In this paper, computational fluid dynamics (CFD) method was used to carry out the numerical simulation of mixing flow field of the integration bottom head in a quenching tank with screw. In order to improve the uniformity and speed of the flow in the vicinity of the head, different quenching schemes of the integrated bottom head were designed virtually and simulated. The placement of the head, the diversion device and the pumping device are all design factors. Eventually, the quenching scheme with bottom three-stage diversion and internal pumping with extended tapered guide was adopted for the deep and thick integration bottom head. The integrated bottom head with this quenching scheme was successfully trial-produced. And the tensile properties, impact properties and drop hammer results of each sampling position meet the product performance requirements with more margin.
A Numerical Investigation of the Mixing in the VCT During the Dilution Process
Authors: Zhang Shengshuai , Wang Naihua , Chi Xiangyu
Published: December 2022

The Volume Control Tank (VCT) is an indispensable device ofChemical and Volume Control System in the primary loop. The incoming water cannot be quickly mixed with the original boric acid solution in the VCT during the dilution process. The poor mixing would delay the reactive control of the core, which increases the time consumption of nuclear power plant operations and brings adverse impacts on core stability. A numerical investigation of the mixing in the VCT during the dilution process is carried out. The numerical methods were validated by experimental data. It is found that there are two different mixing modes in the tank, and the mixing and flow characteristics under different mixing modes are analyzed. It is found that the concentration stratification increases the flow resistance, which has a negative impact on the mixing. Increasing the inlet velocity can effectively avoid stratification and improve mixing efficiency. Increasing the jet density difference will aggravate the stratification in the tank, and even cause the phenomenon of double stratification. The work in this paper has certain guidance for understanding the internal fields in the VCT during the dilution process and improving the mixing efficiency in the VCT.
A Sensitivity Analysis of Condensation Phenomena for a Passive Containment Cooling System by Using Code_Saturne Coupled With OpenTURNS
Authors: Chen Ru , Liang Ronghao , Zhou Lu , Min Jiesheng
Published: December 2022

Computation-expensive problems have become more common in nuclear industry, originating from expensive analysis with the aim of reaching high accuracy. To overcome this challenge, surrogate modelling techniques are often proposed.

Passive containment cooling system (PCCS) is an essential pattern to ensure the containment integrity in the case of accidental conditions for AP600 reactor, so determination of the most influential parameter as regards the heat transfer rate is of great significance to the optimization design and security analysis of nuclear power plants.

This paper contributes to uncertainty quantification in condensation phenomena for PCCS. The purpose is to create a surrogate model instead of a deterministic model for sensitivity analysis on the account of saving computational time. The case used is an experiment carried out in 1998 for which the data is publicly available and was selected here as a showcase of the meta-model construction. In this paper, the database conducted by Anderson in 1998 is used to validate the computational fluid dynamics (CFD) model. By coupling Open-source CFD code code_saturne and uncertainty analysis code OpenTURNS from the SALOME Platform, a representative sample of input and output parameters is obtained using the design of experiments (DoE) technique. Thus, a surrogate model, including kriging and polynomial chaos metamodel, is constructed. In this way, sensitivity analysis of condensing efficiency is performed, which demonstrates the propagation of modeling uncertainty of condensation phenomena.
Numerical Model Development for the Transient Heat and Mass Transfer Performance of a Water-Copper Wicked Heat Pipe
Authors: Liu Jian , Jiang Xingchi , Shah Syed Waqar Ali , Li Yuanjie , Hu Chongju , Yu Dali , Li Taosheng , Pan Chin
Published: December 2022

The application of heat pipes in space nuclear reactors, radiators, and thermal management has gained an enormous amount of attention nowadays. A 3D transient model is needed to study the flow and heat transfer characteristics when considering the complex processes and conditions such as the start-up process, power variation process, non-uniform heating condition, microgravity condition, and so on. In this study, a 3D CFD model for water-copper wicked heat pipe was developed to predict the transient characteristic of heat pipes. A novel source terms method was used through user-defined functions (UDFs) to calculate the evaporation and condensation rates on the water-vapor interface. The laminar flow hypothesis was applied to the flow region. The compressibility of liquid and vapor was considered and the ideal gas equation was adopted for the vapor flow. The Darcy flow characteristic of liquid wick flow was considered in the porous wick region. The simulated outer wall temperature, velocity, pressure, and temperature variation of the wick and vapor during the startup process were obtained and compared with the experimental data. Good prediction results were obtained under the same conditions. The heat flux on the condenser wall will increase quickly due to the quick response-ability of heat pipes. The max vapor velocity shows a minor decrease trend due to the vapor pressure recovery. The distribution of vapor temperature has a significant non-uniformity due to the compression work at the initial time. The beginning of the condensation point will migrate to the condenser section in the start-up process. This study can provide both knowledge and tool for the design of space thermal radiators.
Study on the Radiation Heat Transfer Effect of the Covered Gas Space of the Pool Reactor
Authors: Luo Xinyue , Lu Daogang , Feng Jiaqi , Zhang Yuhao
Published: December 2022

The construction of fast reactor main vessel’s roof slab consists of large argon cavity, plug cock, part of biological shielding column, main pump and heat-exchangers as well as a large number of small-size air gap between plug cock and argon cavity. Therefore, it has an important significant to carry out a thermal hydraulic behavior research on blanket gas top of the main vessel for getting detailed temperature distribution. The temperature field in the headspace of the main vessel of the sodium-cooled fast reactor is of great significance to the analysis of the structural integrity of the reactor. The construction of fast reactor main vessel’s roof consists of large argon cavity, plug cock, Because of the enormous structure of argon cavity. Due to the large space structure of argon gas at the top of the main container, large space and micro-slit space exist at the same time, two orders of magnitude different, which brings difficulties to the theoretical analysis of temperature field. In order to study the distribution of temperature field in the top space of the main vessel, ANSYS series of computational fluid dynamics (CFD) software used to model and simulate the top space of the main vessel of the sodium cold fast reactor. Therefore, based on the existing data, this paper conducts a more detailed simulation study on the thermo-hydraulic behavior of the covering gas in the complex space on the top of the main container of fast reactor. The calculation shows that the symmetry of calculation is good and the flow process is in line with the natural circulation caused by temperature difference. The simulation results are good and can used as the basis and reference for further analysis, which is of positive significance to reactor operation safety.
Research on Characteristics of Condensation Heat Transfer for Marine Nuclear Power Platform PRHR HX Under Tilting Condition
Authors: Li Pengzheng , Li Yongquan , Liu Shaoyou , Zhu Dongbao , Zhu Zhiqiang , Kong Xiaming
Published: December 2022

Passive residual heat removal heat exchanger (PRHR HX) is one of the important equipment in passive residual heat removal system (PRHRs) of marine nuclear power platform. The research on the condensation heat transfer characteristics of saturated steam in PRHR HX tube under tilting condition can provide support and optimization for passive safety system design of marine nuclear power platform. The work in this paper is of great significance to safe operation of marine nuclear power platform. The heat transfer characteristics of saturated steam condensation in the PRHR HX tube under tilting condition are analyzed by building an experimental device with a power ratio of 1:50. The experimental results show that within the range of experimental parameters in this paper, compared with the static state of the experimental device, the condensation heat transfer coefficient of saturated steam in PRHR HX tube under tilting condition is increased. When the heat flux is 190kW/m2, the heat transfer coefficient of saturated steam condensation in PRHR HX tube under tilting condition increases by about 40% compared with static condition. In this paper the formula for calculating the condensation heat transfer coefficient of saturated steam in PRHR HX tube is revised by introducing the tilt angle. The relative error between the modified formula and the experimental value is within ±10%. The research results of this paper can provide reference for the design and optimization of passive safety systems for marine nuclear power platform and similar applications.
One Dimensional Thermal Steady State Code of Sodium Heated Large Straight Tube Steam Generator
Authors: Yang Dingbang , Zhu Lina , Yu Huajin , Yan Xiangyu
Published: December 2022

Sodium heated once through steam generator (SG) is an important part of sodium cooled fast reactor. It converts the heat of hot sodium into water and water into superheated steam. Steam can turn a turbine to generate electricity. Compared with modular steam generator, large steam generator has great advantages in the application of large commercial sodium cooled fast reactor. Large steam generator can reduce its manufacturing cost and improve the economy of sodium cooled fast reactor. At the same time, the design of double-wall tube structure reduces the probability of sodium-water reaction and improves the safety and reliability of steam generator. In this paper, the heat transfer regions of the fluid in the heat transfer tube were reasonably divided, the heat transfer relations suitable for the double-wall tube steam generator were compared and analyzed, the contact thermal resistance of the double-wall tube was studied, and a set of physical models suitable for One-dimensional Steady-state calculation of large double-wall straight tube steam generator were established. In order to test the established physical model, the calculation results of the program were compared with the design data of some double-wall straight tube steam generators. It was found that the two agree well, which verified the correctness of the program. The 1-D steady-state thermal analysis of double-wall straight tube steam generator (DWTSG) was carried out by using the calculated results of the code.
Numerical Study on Fluctuation Characteristics of Free Liquid Surface Under External Force
Authors: Wei Xiaojing , Xia Genglei
Published: December 2022

Ocean conditions can cause the steam generator in nuclear-powered ship to heave, sway and tilt with the ship, causing the free liquid surface in the steam generator to fluctuate and causing additional fluctuations of pressure and water level. In this paper, the CFD method is used to numerically study the fluctuation characteristics of the free liquid surface during the sloshing process of the secondary side liquid in the steam generator under the action of external force. The free liquid surface is tracked by using the VOF (Volume of Fluid Method) method, and additional inertial force is added through the UDF (User Define Function) to simulate rolling conditions. First, the simulation results of the numerical model in this study are compared with the experimental results, and the results are in good agreement, which verifies the reliability of the numerical model to analyze the liquid sloshing problem. Then, through numerical simulation, the fluctuation characteristics of the free liquid surface and the change of the water level and the pressure in the steam generator under different excitation periods are obtained. The results show that the liquid sloshing process in the steam generator exhibits periodic changes, and due to the complexity of the structure of the steam generator, the instability and nonlinearity of the liquid sloshing are enhanced.
Adaptability Analysis of Resistance and Heat Transfer Characteristics of Different Turbulence Models in Narrow Rectangular Channel
Authors: Yu Shengzhi , Gong Zili , Jia Zhen , Kuang Zhengfei , Yuan Anming , Zhou Ping , Yang Xu
Published: December 2022

Under ocean conditions, the flow of natural circulation system will fluctuate periodically, and the flow state of single-phase fluid flowing through the heating channel will change in real time, which may be one or more states of laminar flow, transition flow and turbulence. At present, the main CFD calculation programs, in order to be able to solve quickly, the solution of laminar flow process and turbulent process are basically separated. It is difficult to solve the fluid motion process with multiple flow states with the same set of models, which makes it difficult to study the characteristics of flow and heat transfer in this state. Firstly, the pressure drop experimental results in the channel are used to verify and analyze the flow and heat transfer capacity of eight turbulence models in the narrow rectangular channel, and a turbulence model suitable for analyzing the flow and heat transfer characteristics when multiple flow states coexist or change periodically in the narrow rectangular channel is found. At the same time, the model results are verified by multiple groups of experimental results of resistance and heat transfer characteristics, It provides an idea for the prediction and analysis of flow field and heat transfer characteristics under ocean conditions.
Development and Validation of Simulation Method for a Two-Phase Flow Ejector
Authors: Nakanishi Hiroaki , Komuro Yoshiteru , Kondo Yoshiyuki , Tanimoto Koichi
Published: December 2022

A two-phase ejector is a device to induce a suction flow without pump or electricity. The flow in the two-phase ejector consists of a drive flow and a suction flow. As the driving flow expands blowing out of a drive flow nozzle, the thermal energy potential is converted into momentum, and by giving it to the suction flow, it is possible to induce the flow without using external power. In a nuclear power plant, a two-phase ejector can be utilized as a device to drive coolant flow in the cases of power failure.

Mixing of the drive flow and the suction flow accompanied with evaporation or condensation at the gas-liquid interface depends on thermal hydraulic parameters and flow rate, and it is necessary to control them to maintain the driving force, but it can easily come out of operation range with a slight change in balance. There is little knowledge about heat and mass transfer to find and design operating conditions and ejector configurations.

In this study, a heat and mass transfer model of the gas-liquid interface in a critical two-phase flow was developed. To handle thermally non-equilibrium two-phase flow with phase changes occurring simultaneously at the interface, we implemented constitutive equations into CFD tool, such as a correlation for interfacial area concentrations, and we evaluated evaporation coefficient, which is an important parameter to determine the phase change rate, based on the physical property of the working fluid. The CFD simulation method was validated using the experimental data in the literature of a two-phase ejector. In the validation, the flow rates of the drive flow and the suction flow, and pressure distribution inside the ejector were compared. Then, the validity of the developed CFD simulation method have confirmed.