bluuebunny/crossref_metadata_2025 huggingface dataset:
Dispersal patterns in black howler monkeys (Alouatta pigra): Integrating multiyear demographic and molecular data
Authors: Van Belle Sarie , Di Fiore Anthony
Published: October 2021

Dispersal is a fundamental process in the functioning of animal societies as it regulates the degree to which closely related individuals are spatially concentrated. A species’ dispersal pattern can be complex as it emerges from individuals’ decisions shaped by the cost–benefit tradeoffs associated with either remaining in the natal group or dispersing. Given the potential complexity, combining long‐term demographic information with molecular data can provide important insights into dispersal patterns of a species. Based on a 15‐year study that integrates multiyear demographic data on six groups with longitudinal and cross‐sectional genetic sampling of 20 groups (N = 169 individuals, N = 21 polymorphic microsatellite loci), we describe the various dispersal strategies of male and female black howler monkeys (Alouatta pigra) inhabiting Palenque National Park, Mexico. Genetically confirmed dispersal events (N = 21 of 59 males; N = 6 of 65 females) together with spatial autocorrelation analyses revealed that the dispersal pattern of black howlers is bisexual with strong sex‐biases in both dispersal rate (males disperse more often than females) and dispersal distance (females disperse farther than males). Observational and genetic data confirm that both males and females can successfully immigrate into established groups, as well as form new groups with other dispersing individuals. Additionally, both males and females may disperse singly, as well as in pairs, and both may also disperse secondarily. Overall, our findings suggest multiple dispersal trajectories for black howler males and females, and longer multiyear studies are needed to unravel which demographic, ecological and social factors underlie individuals’ decisions about whether to disperse and which dispersal options to take.
The shift from disbelieving underperformance to recognising failure: A tipping point model
Authors: Gingerich Andrea , Sebok‐Syer Stefanie S. , Lingard Lorelei , Watling Christopher J.
Published: October 2021

Context

Coming face to face with a trainee who needs to be failed is a stern test for many supervisors. In response, supervisors have been encouraged to report evidence of failure through numerous assessment redesigns. And yet, there are lingering signs that some remain reluctant to engage in assessment processes that could alter a trainee's progression in the programme. Failure is highly consequential for all involved and, although rare, requires explicit study. Recent work identified a phase of disbelief that preceded identification of underperformance. What remains unknown is how supervisors come to recognise that a trainee needs to be failed.

Methods

Following constructivist grounded theory methodology, 42 physicians and surgeons in British Columbia, Canada shared their experiences supervising trainees who profoundly underperformed, required extensive remediation or were dismissed from the programme. We identified recurring themes using an iterative, constant comparative process.

Results

The shift from disbelieving underperformance to recognising failure involves three patterns: accumulation of significant incidents, discovery of an egregious error after negligible deficits or illumination of an overlooked deficit when pointed out by someone else. Recognising failure was accompanied by anger, certainty and a sense of duty to prevent harm.

Conclusion

Coming to the point of recognising that a trainee needs to fail is akin to the psychological process of a tipping point where people first realise that noise is signal and cross a threshold where the pattern is no longer an anomaly. The co‐occurrence of anger raises the possibility for emotions to be a driver of, and not only a barrier to, recognising failure. This warrants caution because tipping points, and anger, can impede detection of improvement. Our findings point towards possibilities for supporting earlier identification of underperformance and overcoming reluctance to report failure along with countermeasures to compensate for difficulties in detecting improvement once failure has been verified.
Water stress and disruption of mycorrhizas induce parallel shifts in phyllosphere microbiome composition
Authors: Debray Reena , Socolar Yvonne , Kaulbach Griffin , Guzman Aidee , Hernandez Catherine A. , Curley Rose , Dhond Alexander , Bowles Timothy , Koskella Britt
Published: October 2021

Water and nutrient acquisition are key drivers of plant health and ecosystem function. These factors impact plant physiology directly as well as indirectly through soil‐ and root‐associated microbial responses, but how they in turn affect aboveground plant–microbe interactions are not known.

Through experimental manipulations in the field and growth chamber, we examine the interacting effects of water stress, soil fertility, and arbuscular mycorrhizal fungi on bacterial and fungal communities of the tomato (Solanum lycopersicum) phyllosphere.

Both water stress and mycorrhizal disruption reduced leaf bacterial richness, homogenized bacterial community composition among plants, and reduced the relative abundance of dominant fungal taxa. We observed striking parallelism in the individual microbial taxa in the phyllosphere affected by irrigation and mycorrhizal associations.

Our results show that soil conditions and belowground interactions can shape aboveground microbial communities, with important potential implications for plant health and sustainable agriculture.
Thromboembolic and bleeding risks in edoxaban patients with pacemaker and cardiac monitoring procedures: Outcomes of the Global EMIT program
Authors: Unverdorben Martin , von Heymann Christian , Santamaria Amparao , Saxena Manish , Vanassche Thomas , Wilkins Robert , Jin James , Chen Cathy , Colonna Paolo
Published: October 2021

Introduction

Limited data were published on the management of direct oral anticoagulants in the insertion of pacemaker and cardiac monitoring devices. This study describes the management and outcomes of edoxaban, a direct oral factor Xa inhibitor, in patients undergoing pacemaker or monitoring device implantation in routine clinical practice.

Methods and Results

EMIT‐AF/VTE collected data of patients from Europe, Korea, and Taiwan. Timing and duration of periprocedural interruption of edoxaban were at the treating physician's discretion. Pacemakers or monitoring devices were implanted into 136 patients who were evaluated from 5 days pre‐ until 30 days post‐procedure. The primary outcomes were the incidences of acute thromboembolic events (ATE), ischemic events, and International Society on Thrombosis and Haemostasis‐defined Major Bleeding; secondary outcomes included incidence of clinically relevant non‐major bleeding (CRNMB) and perioperative edoxaban interruption times. Conformance with European Heart Rhythm Association (EHRA) Guidance on interruption of direct oral anticoagulant therapy was variable: of the cardiac monitoring device patients, where no interruption of therapy would be expected, nonetheless, 62.5% had interruption of treatment, whereas in pacemaker procedures, where interruption would be expected, 23.4% had no interruption. No ATE or ischemic events occurred. One case of CRNMB and two of minor bleeding occurred. All bleedings occurred more than 3 days after the procedure.

Conclusion/Relevance

The periprocedural complication risk for edoxaban treated patients undergoing pacemaker or invasive cardiac monitoring implantation was low. This population of patients was well managed in routine practice.
Middle Ordovician mass‐transport deposits from western Inner Mongolia, China: Mechanisms and implications for basin evolution
Authors: Li Wenjie , Chen Jitao , Hakim Anne J. , Myrow Paul M.
Published: October 2021

Subaqueous mass‐transport processes are one of the mechanisms for transport of sediment into the deep sea. Internal structures and depositional processes of carbonate mass‐transport deposits are relatively poorly understood relative to siliciclastic facies due to their comparative paucity in the rock record. A variety of carbonate mass‐transport deposits, including slumps, debrites and deep‐channel‐confined density flow deposits, occur in Middle–Upper Ordovician slope deposits in western Inner Mongolia (Wuhai), China. These provide a rare opportunity to illustrate the emplacement history of carbonate mass‐transport deposits at the outcrop scale. The slumps and debrites host remarkable folds, chaotic beds and imbricated beds that reflect differences in both rheology and position on the slope. Individual slump sheets show gradations between undulating laminae, inclined and recumbent folds, highly deformed folds, and chaotic textures upslope from the toe region. Debrites are commonly interbedded with slump deposits, whereas imbricated beds are present in the middle and lower parts of the toes of slump sheets near the terminal wall. In the study area, thin‐bedded limestone with slump deposits of the Kelimoli Formation are overlain by fine‐grained, siliciclastic‐dominated, slope deposits of the Wulalike Formation. A thick breccia of the Wulalike Formation was deposited in a main feeder channel in south‐east Wuhai, but to the west‐north‐west the breccia was deposited in distributary channels possibly represented as a unique lower‐slope pattern of gullies. At the latter locality, the breccia was deposited solely within the channels on a steep west‐north‐west dipping slope under density‐driven flows. The mass‐transport deposits documented herein records passive to foreland basin tectonic transitions, and associated platform foundering and steepening of the slope. A slope facies model was constructed to demonstrate the spatial and temporal variations of mass‐transport deposits during basin evolution, and as such it provides a template for the interpretation of the deposits of ancient slopes that underwent passive to active tectonic transitions.
Adolescents’ experiences with group antenatal care: Insights from a mixed‐methods study in Senegal
Authors: Vandermorris Ashley , McKinnon Britt , Sall Mohamadou , Witol Adrian , Traoré Mahamadou , Lamesse‐Diedhiou Fatma , Bassani Diego G.
Published: October 2021

Objectives

Group antenatal care (G‐ANC) is an innovative model in which antenatal care is delivered to a group of 8–12 women of similar gestational age. Evidence from high‐income countries suggests G‐ANC is particularly effective for women from marginalised populations, including adolescents. The objective of this study was to examine the experiences of Senegalese adolescents engaged in group antenatal care.

Methods

This convergent parallel mixed‐methods study is derived from a larger effectiveness–implementation hybrid pilot study conducted in Kaolack district, Senegal. Quantitative data for adolescent participants were collected through baseline and postnatal surveys and descriptively analysed. One‐on‐one interviews and focus‐group discussions were conducted with adolescent participants, and qualitative data were analysed using qualitative descriptive analysis.

Results

Forty‐five adolescents aged 15–19 participated in G‐ANC, with a median age of 18 years. The majority (93.3%) were married, and 64.4% were nulliparous. Findings indicated similar levels of G‐ANC participation for adolescent and adult women. The majority (93.1%) of participants who had previously attended individual ANC indicated they would prefer G‐ANC to individual care for a future pregnancy. Qualitative findings indicated key facets of consideration relevant to G‐ANC for adolescents include social connectedness, the influence of social norms and the opportunity for engagement in healthcare.

Conclusions

This study suggests that G‐ANC has the potential to be an adolescent‐responsive and culturally appropriate method of delivering antenatal care in Senegal.
Resistance of SARS‐CoV‐2 beta and gamma variants to plasma collected from Canadian blood donors during the spring of 2020
Authors: Drews Steven J. , Abe Kento T. , Hu Queenie , Samson Reuben , Gingras Anne‐Claude , Colwill Karen , Rathod Bhavisha , Wang Jenny , Fazel‐Zarandi Mahya , Yi Qi‐Long , Robinson Alyssia , Wood Heidi , Tuite Ashleigh , Fisman David , Evans David H. , Lin Yi‐Chan J. , O'Brien Sheila F.
Published: October 2021

Background

This pilot study assesses the ability of plasma collected from Canadian blood donors in the first wave of the SARS‐CoV‐2 pandemic to neutralize later SARS‐CoV‐2 variants of concern (VOCs).

Study design and methods

A repeated cross‐sectional design was used, and a random cross‐sectional sample of all available Canadian Blood Services retention samples (n = 1500/month) was drawn monthly for April and May of 2020. Qualitative IgG analysis was performed on aliquots of specimens using anti‐spike, anti‐receptor binding domain, and anti‐nucleocapsid protein enzyme‐linked immunosorbent assays as well as the Abbott Architect SARS CoV‐2 IgG assay (Abbott Laboratories) against the anti‐nucleocapsid protein. Selected plasma specimens were then assessed for neutralization against VOCs using pseudotyped lentivirus inhibition assays as well as plaque reduction neutralization test 50% (PRNT50).

Results

Six specimens with a high neutralizing titer against wild‐type SARS‐CoV‐2 and three specimens with a low neutralizing titer against wild‐type SARS‐CoV‐2 were chosen for further analysis against VOCs. Four of six high neutralizing titer specimens had a reduced neutralizing capacity against beta VOCs by both neutralization methods. Three of six high neutralizing titer specimens had reduced neutralization capacity against gamma VOCs.

Conclusions

This preliminary data can be used as a justification for limiting the use of first wave plasma products in upcoming clinical trials but cannot be used to speculate on general trends in the immunity of Canadian blood donors to SARS‐CoV‐2.
The impact of free trade agreements on Middle East and North Africa exports of intermediate and final goods
Authors: Cardozo Adriana , Martínez‐Zarzoso Inmaculada , Vogler Paula L.
Published: October 2021

This paper is the first to analyse the impact of free trade agreements (FTAs) and the harmonisation of rules of origin (RoO) on Middle East and North African (MENA) countries’ exports differentiating between final and intermediate goods for a global sample of trade partners. Data on exports from four MENA countries (Egypt, Jordan, Morocco and Tunisia) to 61 destinations over the period 1995–2016 are used to estimate a structural gravity model applying a Poisson Pseudo Maximum Likelihood (PPML) estimator. Moreover, the paper estimates the effect of the progressive adoption of the Pan‐European‐Mediterranean RoO. Results show that FTAs have been overall successful in increasing MENA exports. This is particularly true for FTAs that eliminate protection on agricultural products. In contrast to the existing literature, we find that the agreements concluded with European countries raise MENA exports, whereas no significant impact is found for the application of the Pan‐European RoO.
Experimental and Numerical Study of the Effect of Surface Patterning on the Frictional Properties of Polymer Surfaces
Authors: Balestra Simone , Costagliola Gianluca , Pegoraro Amedeo , Picollo Federico , Molinari Jean-François , Pugno Nicola M. , Vittone Ettore , Bosia Federico , Sin Agusti
Published: October 2021

We describe benchmark experiments to evaluate the frictional properties of laser patterned low-density polyethylene as a function of sliding velocity, normal force, and humidity. The pattern is a square lattice of square cavities with sub-mm spacing. We find that dynamic friction decreases compared to nonpatterned surfaces, since stress concentrations lead to early detachment, and that stick-slip behavior is also affected. Friction increases with humidity, and the onset of stick-slip events occurs in the high humidity regime. Experimental results are compared with numerical simulations of a simplified 2D spring-block model. A good qualitative agreement can be obtained by introducing a deviation from the linear behavior of the Amontons-Coulomb law with the load due to a saturation in the effective contact area with pressure. This also leads to the improvement of the quantitative results of the spring-block model by reducing the discrepancy with the experimental results, indicating the robustness of the adopted simplified approach, which could be adopted to design patterned surfaces with controlled friction properties.
Droplets Impacting and Migrating on Structured Surfaces With Imposed Thermal Gradients
Authors: Chen Lei , Jin Guanghu , Dai Qingwen , Huang Wei , Wang Xiaolei
Published: October 2021

In this work, the dynamic process of oil droplets impacting and migrating on structured surfaces with imposed thermal gradients was investigated. It was observed that on an isothermal smooth surface, a lubricant droplet would impact, spread to a maximum diameter, and retract; while on a non-isothermal smooth surface, an asymmetric geometrical morphology of droplet was generated, accompanying with a migration process. Relevant dimensionless parameters were employed to evaluate the dynamic process, and the physical mechanism was revealed. Decorating surfaces with convergent microgrooves pattern could not only increase the maximum spreading diameter but also accelerate the migration process. These are beneficial for the heat exchange efficiency and lubrication performances.
Analysis of Dynamic Changes in Customer Sentiment on Product Features After the Outbreak of COVID-19 Based on Online Reviews
Authors: Kim Jinju , Park Seyoung , Kim Harrison M.
Published: October 2021

Sudden changes in life and work patterns due to COVID-19 have affected customer requirements for the products. Under these circumstances, companies can achieve high profitability and customer satisfaction when they can efficiently identify and respond quickly to changing customer preferences caused by COVID-19. This article presents empirical research on dynamic changes in customer responses for product features caused by the spread of COVID-19 through sentiment analysis based on online reviews. A case study is conducted using new and refurbished smartphone reviews to investigate the dynamic changes in customer sentiment before/during COVID-19. The importance of the result is shown by comparing it to the actual market data.
Study on Eutectic Melting Behavior of Control Rod Materials in Core Disruptive Accidents of Sodium-Cooled Fast Reactors: (2) Kinetic Study on Eutectic Reaction Process Between Stainless Steel With Low Boron Carbide Concentration and Stainless Steel
Authors: Kikuchi Shin , Takai Toshihide , Yamano Hidemasa , Sakamoto Kan
Published: October 2021

The eutectic reaction between boron carbide (B4C) and stainless steel (SS) is one of the most important phenomena when considering the core disruptive accident (CDA) in a sodium-cooled fast reactor (SFR). Thus, in order to perform the safety assessment of SFR under postulated severe accidental condition reasonably, the kinetic information on B4C-SS eutectic reaction is required.

In this study, the reaction experiments using SS crucibles and the pellets of SS with low B4C concentration, i.e., 2.5–10 mass% B4C as samples were performed to simulate the state of the reaction interface in which the eutectic reaction and interdiffusion of B4C-SS have progressed to a certain extent. Each sample was placed into an alumina core tube and heated up to 1473–1673 K at different duration time by using an electric furnace. For recording the thermal behavior of B4C-SS and SS-SS with low B4C concentration, in-situ observation for the appearance of each sample around eutectic temperature was performed using high sensitivity camera.

The rate constant as kinetic information was estimated on the basis of the thickness of the eutectic layer and duration time after the reaction experiments. It was revealed that the rate constants of eutectic reaction between SS and SS with 2.5–10 mass% B4C are smaller than that of B4C-SS eutectic reaction at high temperatures. Besides, the rate constant of the eutectic reaction between SS and SS with certain B4C concentration became small when the B4C concentration against SS decreased. Moreover, it was confirmed that the liquid phase reaction feature of SS-SS with certain B4C concentration is still dominant in comparison with that of B4C-SS at low temperatures.
Study on Safety Class 2 Piping Fatigue Evaluation for 60 Years of Design Life
Authors: Lee Dae-Geon , Kim Kyoung-Su , Heo Young-Hun , Cho Seong-Ho , Kim Hyeong-Wook
Published: October 2021

In the past, most of nuclear power plants in the world were constructed with 30 or 40 years of design-life. But some nuclear power plants are still operating beyond their design lives through regulatory permission to extend its operation. To extend designlife of nuclear power plant, it needs additional design and replacement for equipment and piping. It has also to meet the regulatory requirements under the approval of the regulatory body. Therefore, the original design life of 60 years has been applied to safety class 1 equipment and piping of some nuclear power plants. One of the methods to confirm whether safety class 2&3 equipment and piping can also operate up to 60 years is to perform the fatigue evaluation based on ASME B&PV Code. In consideration of the effects of load increase by extending their lifespan from 40 to 60 years, the equipment and piping should be evaluated the structural integrity by performing the heat transfer analysis and structural analysis. In this paper, the fatigue evaluation for the Safety Class 2 FW piping with 40-year design life was performed based on Subsection NB/NC of ASME B&PV Section III and Reg. Guide 1.207 to show that its fatigue integrity can be secured under 60-year operation even in the PWR environmental conditions.
Application of EEMD-Multiscale Entropy Algorithm in the Signal Analysis of Narrow Channel Two-Phase Flow Under Rolling Motion
Authors: Chu Wenjun , Liu Yang , Zhu Hongye , Yang Xingtuan , Pan Liqiang
Published: October 2021

The narrow rectangular channel has the advantages of compact structure and high heat transfer coefficient, and has been widely used in nuclear systems. However, the internal flow of the narrow channel will be affected by the non-inertial force when it is used in undulating conditions. Aiming at the visualized parallel narrow channel boiling experiment system, this study applies the EEMD method to the analysis of signals such as outlet pressure of the test section under rolling conditions. We utilize the features that the variance and energy of the empirical mode decomposition component will suddenly change in the low frequency band, and effectively realize the adaptive removal of signal noise and signal reconstruction under different rolling parameters. This paper also introduces the theory of multi-scale entropy to extract features of different time-scale signals obtained by EEMD method. The obtained signal energy moment and multi-scale entropy changes obviously with the gas-liquid distribution of the experimental section, which can be used as the basis for narrow channel flow pattern identification.
Study on the Structural Evaluation and Optimization of Spent Nuclear Fuel Cask
Authors: Hao Yuchen , Wang Jinhua , Li Yue , Wu Bin , Wang Haitao , Ma Tao
Published: October 2021

Nowadays, nuclear power plays an important role in world electrical energy. Nuclear power plants have inevitably produced radioactive spent nuclear fuel (SNF) during operation. Generally, intermediate storage facilities and at-reactor pools store fresh SNF and remove its residual heat at about five years. However, as time goes by, all of these temporary facilities are near capacity. We are supposed to pay attention to transportation safety, to avoid radioactive material leakage, especially in public domain. Indeed, 9 m drop test is one of the most crucial tests derived on safety regulation which may cause serious structural damage.

In this paper, safety performance of a base spent nuclear fuel cask is evaluated. At the same time, the rotation of cask during the drop is considered, because drop inclination which may influence the cushioning effect is random when contacting the ground. Subsequently, the result of safety performance can be utilized to establish comprehensive damage curves. This work is also set up to determine the most dangerous condition. And then optimization is carried out to investigate the effects of some material and design parameters under this condition. Finally, a design approach combining evaluation and optimization is summarized, which can be applied in other nuclear cask systems.
Transport Behavior of Silver in High-Temperature Gas-Cooled Reactors
Authors: Wang Yu , Cao Jianzhu , Xie Feng , Yang Xiaobao , Li Peng , Ma Jie , Duan Xianbao
Published: October 2021

High-temperature gas-cooled reactor (HTGR) is characterized by inherent safety, superior proliferation resistance, and high efficiency, with a promising prospect on electric power product and high-temperature heat and hydrogen production. The enhanced safety mostly relies on the good retention of tristructural-isotropic (TRISO) coated fuel particles for fission products. Most radioactive nuclides are retained in the fuel element dispersed with a large amount of TRISO coated fuel particles during normal and off-normal transients. However, silver can pass through the intact TRISO coated fuel particle and this has been reported by researchers worldwide. Numerous studies have focused on the migration of silver and tried to interpret its unique behavior. Additionally, several theories have been proposed and abnormal occurrences have been ascribed to excess silicon, chemical degradation of SiC, grain boundaries, long columnar grains, nano-pores, nano-cracks, re-wetting process, lattice diffusions, and so on. However, this problem has not been completely solved so far. This paper introduces the general diffusion theory for fission products in the spherical particle, reviews recent theoretical models and mechanisms on silver migration and discusses the diffusion features of silver under different mechanisms. Based on the current investigations, several suggestions have been posed to end debate on silver migration in SiC. These suggestions can lay a good foundation for further studies on migration behavior of silver.
Subchannel Analysis of Radial Uniform and Non-Uniform Heating Assembly Under Low Mass Flow Rate Conditions
Authors: Zhu Gan , Xu Wei , Xie Heng
Published: October 2021

The nuclear heating reactor (NHR), which is independently developed and designed by Tsinghua University, adopts full power natural circulation and has the characteristic of low mass flow rate. Due to the different operating conditions between NHR and PWR, it is necessary to analyze the thermal hydraulic performance of the fuel assembly in NHR core. The thermal hydraulic performance of the fuel assembly is mainly analyzed by the subchannel analysis code which can accurately calculate the two-phase parameters. Therefore, this research employs subchannel analysis code COBRA-TF to simulate radial uniform and non-uniform heating assembly under the operating conditions of low mass flow rate from 300kg/m2s to 700kg/m2s. The simulations are validated on the thermal hydraulics experiments of GE and Studsvik. The result shows that the calculated mass flow rate and void fraction are in good agreement with the experimental results. Under radial nonuniform heating condition, high outlet mass velocity appears in low heating power region, while the high outlet void fraction appears in high heating power region. Compared with the uniform heating condition, the distribution of the mass flow rate and the void fraction in subchannels under non-uniform heating conditions varies greatly. In addition, the transverse flow and the counterflow also can be observed in non-uniform heating conditions under low mass flow rate conditions. The appearance of such transverse flow mainly results from the radial pressure difference, rather than the turbulent mixing and void drift. Therefore, it is essential to predicate the distribution of the mass flow rate and the void fraction under non-uniform heating and low mass flow rate conditions.
Preliminary Version of Improved Particle-Flow Model in SIMMER-V for an Alternative Severe Accident Modeling Approach in SFRs
Authors: Csengeri Eszter , Bachrata Andrea , Trotignon Laurent , Merle Elsa
Published: October 2021

The purpose of the present study is to evaluate and improve the capability of the SIMMER code to demonstrate severe accident mitigation in Sodium-cooled Fast Reactors (SFR). Here the numerical representation of the mitigation strategy with controlled material transfer is carried out with SIMMER. By using the advanced multi-phase modelling option of the code, the particle-size solid debris are treated with an independent momentum field. This modelling choice is encouraged for the simulation of Unprotected Loss Of Flow (ULOF) type transients in French SFR core design where low enthalpy degraded fuel is expected to manifest in solid fragments. Applying this new particulate approach in SIMMER code requires the reevaluation of current SIMMER fluid dynamics modelling. In this context, this paper assesses the applicability of SIMMER momentum models to account for the peculiar behaviour of a purely particulate phase. We present the first improved model of interphase momentum transfer and a sensitivity study on solid particles-wall stress models. The assessment is performed through the investigation of simplified test cases that can be associated to reactor scenarios during severe accident mitigation. The test cases show that the new modifications in the SIMMER code bring significant improvements in predicting the discharge behaviour of degraded core mixture.
A Finnish District Heating Reactor: Thermal-Hydraulic Design and Transient Analyses
Authors: Komu Rebekka , Hillberg Seppo , Hovi Ville , Leppänen Jaakko , Leskinen Joona
Published: October 2021

Development of a small district heating reactor was started at VTT Technical Research Centre of Finland. The concept features a 50 MW reactor that operates at low temperature and pressure. Traditional LWR technology, passive safety functions and natural circulation are combined in the integrated design. This paper presents the thermal-hydraulic design and transient analyses done with Apros simulation software. The studied cases include station blackout with reactor trip and as an ATWS scenario, and small break LOCA in the lower downcomer. During the station blackout transients, both temperature and pressure remained at safe levels. The innovative containment design functioned as planned and was capable of efficient decay heat removal. The small break LOCA ceased the natural circulation, but the core was not uncovered at any point and the core temperatures remained low. The results from the thermal-hydraulic analyses are promising and show that the reactor design is capable of producing low temperature heat to the district heating network. The analyzed transients posed no risk to reactor safety, and the passive containment function was capable of removing decay heat efficiently. These preliminary analyses give valuable insight to the design work in the future.
Design Analysis of Radiation Shielding Door in High-Level Waste Treatment Plant
Authors: Shen Jingyi , Chen Zonghuan , Wang Bingheng , Gao Guiling
Published: October 2021

In high-level waste treatment plants, rooms where the highly radioactive sources (such as the vitrification containers) are operated have high radiation protection risk. On the purpose of ensuring the safety of operators, it is necessary to design corresponding shielding walls, windows and shielding doors to guarantee that the dose rate at the personal operating location outside the room meets corresponding control requirements. Compared with walls, the radiation safety designs of the doors and windows are more complicated. In this article, a shielding door of a hot room inside a high-level waste treatment plant is selected. By means of combing the source characteristics and the source location, the gap between the door and door frame as well as the lap joints of the door and the wall are analyzed in order to characterize the influence factor of the dose rate outside the shielding door. The results illustrate that, under the premise that the shielding design requirements are satisfied, the lap joint between shielding wall and door has a significant impact on the outdoor dose field due to the oblique incidence of the radiation ray. Therefore, in the follow-up design of the radiation shielding door, A certain overlap form of the lap joints between the door and the wall need to be satisfied, furthermore, special attention need to be paid to the shielding of radioactive sources with weak self-shielding effect and strong penetration ability, for ensuring the shielding door to the greatest extent radiation protection ability.
Estimation of Vibration Characteristics of Nuclear Facilities Based on Seismic Observation Records
Authors: Yamakawa Kouki , Saruta Masaaki , Moritani Hiroshi , Yamazaki Hiroaki , Nishida Akemi , Kawata Manabu , Iigaki Kazuhiko
Published: October 2021

After the 2011 off-the-Pacific coast of Tohoku Earthquake, regulatory standards for nuclear power plants were tightened. Therefore, a three-dimensional (3D) finite element model to evaluate the local response of the reactor building is currently being developed for seismic response analysis.

In order to refine the 3D finite element model, it is important to verify the correspondence to the seismic observation behaviors. In this study, the authors analyze the basic response characteristics, such as the natural frequencies and modes of the reactor building, and evaluate the effects of the amplitude of the seismic excitation on the response characteristics based on seismic observation records. This is done to clarify the behavior of a reactor building during earthquakes. These analyses will assist in quantitatively evaluating the correlation between the natural frequency of the building and the amplitude of the seismic excitation. Furthermore, the ratios of rotational displacement and displacement caused by building deformation for natural modes are discussed.
Power Control System Design for a Heat Pipe Cooled Reactor
Authors: Sun Haowei , Sun Peiwei
Published: October 2021

Due to the small size, the high-power density and the strong environmental adaptability, the heat pipe cooled reactor has a broad application prospect in the fields of space exploration, underwater vehicle power system and other fields[1]. It will be one of the subversive technologies which will change the future nuclear power development. The safe operation of the heat pipe cooled reactor requires an effective power control system.

3KeyMaster is a comprehensive real-time simulation analysis platform and the control system can be built by using its logic module. The interface program can be developed in its task program, and other program can be integrated in this platform[2]. The system program of the heat pipe cooled reactor has compiled as a dynamic linking library. Through the task program of the 3KeyMaster simulation platform to call the dynamic linking library by using C++ program, the system program is coupled with the 3KeyMaster simulation platform. The modules of 3KeyMaster platform exchange data with the system program by shared memory.

Through the responses of the temperature due to step change in the reactor power obtained by 3KeyMaster, the transfer functions are obtained by using the system identification module in MATLAB & Simulink. The power disturbance is introduced, and simulation is carried out on the 3KeyMaster. The changes of the important parameters are analyzed to obtain its dynamic characteristics. Based on the dynamic analysis on the system responses, the control strategy for the power control system is proposed.

The power control system is implemented in MATLAB & Simulink. The control system parameters are tuned to determine a group of suitable control parameters[3]. Finally, the control performance of power control system is evaluated by simulations.
Using Monte Carlo Method and Adaptive Sampling to Estimate the Limit Surface
Authors: Zhang Lixuan , Zhang Zhijian , Wang He , Zhang Yuhang , Sun Dabin
Published: October 2021

In the research on the risk-informed safety margin characterization (RISMC) methodology, how to estimate the limit surface is important. Using the reduced Order Models (ROMs) to simulate calculations can obtain results more quickly and estimate the limit surface. For example, we use ROMs instead of Complex simulation model, Parameters that are critical to the safety of nuclear power plants, such as the peak temperature of the fuel cladding, can be calculated relatively quickly. Using Monte Carlo method to analyze nuclear accident is low efficiency and poor accuracy. To get relatively accurate results, a large amount of simulation experiments is needed. Based on adaptive sampling, the samples which will cause failure will be acquired more easily. Adaptive sampling uses the calculation results of the previous step to guide the next step of sampling, which can quickly obtain the samples points near the failure edge.

This article will introduce the definition of the limit surface and use the Monte Carlo method and the adaptive sampling to estimate the limit surface through ROMs. And compare the calculation results of the two methods and the number of samples required. The two methods are verified by a case.
Study on Deteriorated Heat Transfer in Upward Flow of Supercritical Water in a 1-M Vertical Bare Tube
Authors: Dort-Goltz N. , Pioro I. , McKellar J.
Published: October 2021

SuperCritical Water-cooled Reactors (SCWRs) represent potential improvements over traditional water-cooled reactors in many respects, including thermal efficiency. These reactors are still under development, however, thermalhydraulics data needed for their design are lacking. Experimentation is complex and costly. In spite of a large number of experiments in long bare tubes (pipes) cooled with SCW, developing SCWR concepts requires experimental data in bundle geometries cooled with SCW, which are usually shorter and will have smaller hydraulic-equivalent diameters.

As a first step, tests have been conducted by others on heat transfer in short, vertical bare tubes cooled with the upward flow of SCW. The objective of this work is to analyze that collected data with particular attention to the Deteriorated Heat Transfer (DHT) regime. The DHT regime is characterized by reduced Heat Transfer Coefficients (HTCs) and consequently increased wall temperatures. As such, it represents a hazard to the safe operation of a Nuclear Power Plant (NPP).

The results of this analysis indicate that DHT did occur in each of the tests analyzed, often seen as a gradual decrease in HTC along the heated length, but occasionally as a sharp “dip”. The DHT can occur along the heated length, when the bulk-fluid temperature is close to or within the pseudocritical region. The results also confirmed that the Dittus-Boelter correlation does not adequately predict HTCs within the pseudocritical region. Two other applied correlations (Gupta et al. and Mokry et al.) performed better, but neither was able to predict the occurrence of the DHT.

The results of this analysis will be of use to designers and developers of SCWRs, and can help to plan future experiments.
Experimental Study on Edge Blockage Accidents in a Narrow Rectangular Channel
Authors: Yuan Dongdong , Du Weian , He Yuhao , Zhu Jiahong , Zhang Yonghao , Li Chengwei , Tan Sichao , Li Dongyang
Published: October 2021

The blocked accident of plate fuel assembly is one of the serious accidents in the reactor. It will worsen the heat transfer capacity of the coolant and even affect the safe operation of the reactor. Therefore, Particle Image Velocimetry (PIV) technology and the Laser Induced Fluorescence (LIF) technology are used in current paper to investigate the edge blockage accidents in a narrow rectangular channel with a continuous-wave laser and two high-speed cameras. During the experiments, the obstacle has great effect on the flow field and temperature field. It is found that large-scale vortex structure will be generated in the wake downstream of the obstacle. And where the vortices exist, the fluid temperature is also higher, which means that the vortices prevent the heat from escaping in time. Besides, the temperature distribution at different Re numbers is also analyzed. It can provide a validation for numerical simulations.
An Optimized Dynamic Algorithm With Photon Attenuation Coefficient for Path-Planning in Radioactive Environments
Authors: Miyombo Miyombo Ernest , Liu Yongkuo , Ayodeji Abiodun
Published: October 2021

Radiation protection is central to ensure nuclear safety, proper operating conditions, and the prevention of accidents in nuclear facilities. Increasingly, path planning is being used to keep radiation risks as low as reasonably achievable (ALARA). However, most of the approach is sub-optimal, because they rely on exposure and roentgen definition only when considering different types of radiation and materials. Moreover, additional concepts are needed to determine the energy deposited in different body parts. In this study, we present an Optimized Dynamic Algorithm (ODA) for minimum dose path-planning in a radioactive environment based on photon interaction with matter and shortest path algorithm. The proposed ODA can estimate the energy flux per unit area reaching a standard adult from a radiation source using the probability of photon absorption in the air. The approach also utilizes the Compton effect of the energy flux to determine the fraction of energy transferred to electrons in the body. Two radioactive scenarios are investigated to evaluate the performance of the proposed ODA. The significant improvement obtained from the ODA is presented in this paper.
Atomic Insights on Interaction Mechanism of Dislocation With Void/Impurity/Precipitates in BCC Iron
Authors: Azeem M. Mustafa , Yun Di , Zubair Muhammad
Published: October 2021

Ferritic steels are important cladding and structural material for current and advanced reactors containing Fe as a primary compositional matrix element. Three proposed models containing voids, impurity P, and nano oxides embedded in Fe were simulated using molecular dynamics code LAMMPS. The interaction mechanism of dislocation for each model was observed and compared by analyzing its strengthening effect through the stress-strain curve. In considering the interaction of dislocation with voids, it was observed that for all void sizes, dislocation bypass voids following orowan unpinning mechanism without any loop irrespective of any radii, while for P clusters, dislocation is trapped at the interface and leaves it after making a screw dipole shape following orowan mechanism. Moreover, the oxide dislocation interaction in oxide dispersed in iron follow the orowan unpinning mechanism accompanied by loops around oxide. The values of critical unpinning stress for all models were analyzed and compared. Atomic insights on the interaction mechanism indicate that the interaction mechanism is essentially the same for void and a P cluster in Fe i.e. orowan unpinning mechanism. The presence of oxide in Fe matrix during its interaction follows the orowan unpinning mechanism along with a dislocation loop around the oxide and its area is proportional to the size of the oxide. The critical unpinning stress was compared and analyzed for each model.

This work will provide a unique and valuable insight into the strengthening mechanism due to dispersed oxides by providing new parameters for the multi-scale simulation. Our results demonstrate that oxide impedes dislocations and offers hindrance for edge dislocations to saturate further. Furthermore, our simulation results provide atomic insight into the onset of plasticity in iron alloys.
Study on Buckling Strength and Post Buckling Behaviors of Reactor Vessel Lower Heads
Authors: Murohara Masato , Yamazaki Akira , Sato Takuya , Kasahara Naoto
Published: October 2021

As the lessons learned from the Fukushima Daiichi Nuclear Power Plant accident, the importance of controlling the behavior after a failure and mitigating consequences of a failure was recognized. Conventional reactor structural design has been aimed at preventing the occurrence of failure due to Design Basis Events (DBE). This study aims to improve the resilience of the reactor structure under Beyond Design Basis Events (BDBE), such as very high temperatures and excessive earthquakes during severe accidents, by mitigating the consequences after failure.
Optimization of Maintenance Strategy for Sea Water Pumps in Nuclear Plants
Authors: Zhao Ling , Liu Deyi , Zhao Ming
Published: October 2021

Probabilistic Safety Analysis (PSA) methodology is a significant supplement to the deterministic safety analysis in the nuclear power plant. PSA can be used to evaluate the NPP device change, equipment maintenance, in service inspection. The practicability of modifying sea water pump maintenance programme is evaluated in this paper by determining the initial event probability in fault-tree and modifying the PSA calculation model. Based on the evaluation results, the preventive maintenance of sea water pump and 6kv switch can be changed from executed in the plant overhaul to executed in the routine maintenance. This could make a great contribution in optimizing the NPP sea water pump maintenance program.
Pipe Performance in Long Term Operation Framework: Ageing Issues
Authors: Cancemi S. A. , Lo Frano R.
Published: October 2021

The Long-Term Operation (LTO) process involves a full screening of structures, systems, and components (SSCs), for ageing assessment in order to verify their residual safety margin is still acceptable. At today, 46% of the operating Nuclear Power Plant (NPP) has lifetime between 31 and 40 years, while 19% is in operation since more than 40 years. LTO currently represents the highest priority for all the nuclear industry. To propose and plan suitable management strategies, first step is to intensify the efforts for studying phenomena that influence the performance of SSCs and, in turn, may threat the plant safe operation.

This study deals with the investigation of the performance of a primary piping (Class 1 component of a 2nd Generation PWR) subjected to the effects of alteration of material properties as caused by ageing. In this study it is proposed a numerical investigation of a piping characterized by a complex geometry. Numerical analyses were performed by means of MSC©MARC FE code. The (quantitative) influence of ageing and corrosion processes onto bent pipe are so studied. Particularly, corrosion effects generated from an operation of beyond 35 years are considered. The methodology and results may have an influence on future issues about LTO of NPPs.
Development of Ex-Vessel Debris Bed in a Flooded Cavity With Inclined Bottom Structure Under Two-Phase Condition
Authors: Modak Mayank , Park Hyun Sun , Choi Yu Jung , Seo Mi Ro
Published: October 2021

Severe accidents (SA) in Light Water Reactors (LWRs) consist of a sequence of thermal-hydraulic events which leads to situations that progress beyond design-based accidents (DBAs), and involve significant core degradation which threatens the integrity of the containment boundary. As part of the coolability assessment under accident conditions, the geometrical configuration of the debris bed is important. Here, experimental study was performed to investigate the formation of debris beds under the influence of a two-phase flow induced by steam generation due to the decay heat of the debris bed on an inclined bottom surface. Current study is an extension to the previous work of Kim et al. (2016) in which the previous model for development of an ex-vessel corium debris bed will be modified by incorporating the effect of bottom surface inclinations. This paper reports the experimental part of the study describing the spreading of the debris bed in terms of two-phase flow, debris injection parameters, and bottom inclined surface geometrical parameters is discussed.