bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the Kinetics of Molten Pool Stratification in Case of In-Vessel Melt Retention Strategy
Authors: Carénini L. , Fichot F. 
Published: October 2018

The In-Vessel Retention (IVR) strategy for Light Water Reactors (LWR) intends to stabilize and retain the core melt in the reactor pressure vessel. This type of Severe Accident Management (SAM) strategy has already been incorporated in the SAM guidance (SAMG) of several operating small size LWR (reactors below 500MWe, like VVER440) and is part of the SAMG strategies for some Gen III+ PWRs of higher power like the AP1000.
One of the main issues for the demonstration of the success of the IVR strategy lies in the evaluation of the transient heat fluxes applied by the corium pool along the vessel wall. Indeed, these transient heat fluxes, during the corium pool stratification evolution, are expected to be higher than the steady-state ones, in particular due to the concentration of the heat flux in the top metal layer when it is thin (so called focusing effect). Another issue appears when a heavy metal is initially formed and rises later to the top (inversion of stratification): in such a situation, the metal goes through the oxide phase and accumulates a significant superheat which is likely to produce a high transient heat flux. Thus, it is of primary importance to be able to evaluate the duration of these transient peaks in order to evaluate the minimal residual vessel thickness after such fast transient ablation and draw conclusions about the vessel integrity.
This paper first presents the phenomenology associated to the transient molten pool stratification and the model implemented in the severe accident integral code ASTEC (Accident Source Term Evaluation Code) to evaluate this kinetics. Then, evaluations are presented, based on a typical PWR reactor configuration. A sensitivity study is proposed to consider the impact of the main uncertainties on parameters which govern this kinetics. A particular focus is made on the physical phenomena driving the transient stratification of material layers in the corium pool and on the identification of critical situations with possible consequences in terms of vessel failure. The characteristic times of each individual process (chemistry, stratification, natural convection) are compared. In particular, the limiting cases of very fast chemistry or very slow chemistry are evaluated.
This work is performed in the frame of the European H2020 project IVMR (In-Vessel Melt Retention) coordinated by IRSN. This project has been launched in 2015 and gathers 27 organizations with, as main objective, the evaluation of feasibility of IVR strategy for LWR (PWR, VVER, BWR) of total power 1,000MWe or higher.
The Effect of Initial Condition of Melt Jet on the Jet Breakup Phenomenon in the Subcooled Water Pool
Authors: Jung Woo Hyun , Park Hyun Sun , Moriyama Kiyofumi , Kim Moo Hwan 
Published: October 2018

The melt jet breakup phenomenon in a pre-flooded reactor cavity during a severe accident is related to the debris bed coolability. It is important to predict the jet breakup length for the evaluation of the debris bed coolability.
A large volume of works on the jet breakup length have been performed. However, the consistency between experiments and correlations was difficult to achieve. Some data follow the Saito correlation (include Froude number in the correlation) and others follow the Epstein correlation (doesn’t include Froude number).
The separation of the jet breakup length correlation along the water subcooling was reported based on the experimental data using the low melting temperature materials in our previous works. Since the previous experiments show an unclear jet shape before entering the water pool which could be an uncertainty factor, a slide gate system for a clear jet shape was additionally installed. Experiments were conducted with the similar condition of previous work and different initial condition of melt jet. With a clear jet shape, the jet breakup length in the subcooled water show different tendency following the Saito correlation.
To figure out the effect of the entry condition of the melt jet, the jet diameter and the method of estimating the jet breakup length are revisited. Our previo0us experiments show large uncertainties on the jet diameter, leading to the large discrepancy of the dimensionless jet breakup length. Also, early broken jet core is reported in subcooled water cases.
Thus, the uncertain characteristics of the jet breakup length analysis is discussed in this paper including the jet diameter and the method to estimate the jet breakup length.
Development of a Standard for Fusion Needs: Example of Introduction of Eurofer in RCC-MRx
Authors: Muñoz Garcia J. E. , Pétesch C. , Lebarbé T. , Lamagnère P. , Lejeail Y. 
Published: October 2018

The 2018 edition of the RCC-MRx Code [1] will be issued by the end of the 2018, in French and English versions by AFCEN (Association Française pour les règles de Conception et de Construction des Matériels des Chaudières Electro-nucléaires). This Code set up design and construction rules of research reactor components (coming from the RCC-MX 2008 code developed within the context of the Jules Horowitz Reactor project), and to components operating at high temperature and to the Vacuum Vessel of ITER (coming from the RCC-MR 2007).
The extension of the scope of the code to innovative systems such as fusion reactors leads to revisit the background of the code to define the requirements to introduce a new process or a new material.
The developed methodology has been applied to the introduction of the Fe–9%Cr–1%W–TaV steel (Eurofer), today in the Probationary Phase Rules of RCC-MRx. It was the first time to introduce a “new” material into the code, new in the sense of non-existing in any current standardization. This process, still in progress, highlights the need to have a minimum of information on the expectation of the code regarding the material data.
This paper describes the different steps of the introduction of the Eurofer in the RCC-MRx code as well as the tools developed to facilitate the process.
Thermal Stratification Modeling for Sodium-Cooled Fast Reactors: A Status Update
Authors: Morgan Sarah , Bilbao y Leon Sama , Bucknor Matthew , Anderson Mark , Baglietto Emilio , Schneider James , Weathered Matthew , Xu Liangyu 
Published: October 2018

Thermal hydraulic behavior in the upper plenum of pool-type sodium-cooled fast reactors (SFRs) is a major concern, as many design challenges are concentrated in this region. As SFR designs aim for licensing and commercialization, it is important to accurately analyze and predict the thermal-hydraulic behavior in this region during accident scenarios, specifically thermal stratification.
Thermal stratification models are currently a major source of uncertainty in most system codes for all types of power plants. Most system codes, including SAS4A/SASSYS-1, a system level code developed by Argonne National Laboratory (Argonne), use very coarse meshes that cannot capture the complexities of the stratification phenomena. While the commonly employed lumped-volume based models for thermal stratification are able to run in a matter of seconds, they result in approximate results and can only handle simple cases. Other 2-D and 3-D methods, such as computational fluid dynamics (CFD) models, can analyze simple configurations with higher fidelity, but come with a relatively large computational expense. Finding a modeling solution that is both accurate and computationally efficient has proven difficult.
This paper provides details of a review and gap analysis of the various modeling approaches proposed to date and explores a path forward for future thermal stratification modeling efforts, with a focus on developing new models for the SAS4A/SASSYS-1 system code.
Partially Averaged Navier-Stokes Turbulence Modeling of Flow in 5x5 PWR Fuel Assembly With Spacer Grid
Authors: Busco Giacomo , Hassan Yassin A. 
Published: October 2018

The highly turbulent flow inside a pressurized water reactor makes unpractical the use of scale resolving simulations, due to the large number of space and time turbulent structures. The high computational cost associated with typical large eddies simulations or direct numerical simulations techniques is unsuitable due to the large spatiotemporal resolution required. Partially averaged Navier-Stokes turbulence model is presented as bridging model between Reynolds averaged Navier-Stokes equations and direct numerical simulations. As filtered representation of the Navier-Stokes equations, the model is able to continuously shift its energy-based filter, inside the turbulence spectrum, being able to resolve the turbulent scales of interest. The choice of energy based cut-off filters gives the chance to directly impose the degree of needed resolution, where the most important large scales unsteadiness are resolved at minimal computational expenses.
The partially averaged Navier-Stokes modelling approach has been tested for a Reynolds number of 14,000, inside a 5 × 5 fuel bundle, with a single spacer grid and split-type mixing vanes. Four different filters have been tested, whose resolution ranged from Reynolds averaged Navier-Stokes and large eddy simulation. A comparison with large eddy simulation will be presented. The results show that the partially averaged Navier-Stokes modeling produces results comparable to those of large eddy simulation when the appropriate cut-off energy filter is chosen. The turbulence models results will be compared with the available particle image velocimetry experimental data.
Multi-Diversity for FPGA Platform Based NPP I&C Systems: New Possibilities and Assessment Technique
Authors: Kharchenko Vyacheslav , Kovalenko Andriy , Leontiiev Kostiantyn , Panarin Artem , Duzhy Vyacheslav 
Published: October 2018

Diversity approach is used to decrease risk of common cause failure (CCF) of Nuclear Power Plant (NPP) Instrumentation and Control systems (I&Cs). Application of a multi-diversity, i.e. a few different types of version redundancy allows minimizing CCF risk. On the other side, implementation of diversity increases cost and complicates maintenance of multi-version I&Cs. Hence, it is important to find optimal solution according with criteria “required level of diversity (safety) / minimal cost and maintenance complexity. Modern FPGA technology creates additional possibilities to meet requirements of the standards (such as NUREG/CR-7007, IEEE Std 7-4.3.2-2016, IAEA SSR-2/1:2016, IAEA NP-T-3.17:2016 and others) by developing main and diverse subsystems on the basis of the same FPGA platform. Existing diversity normative base should be enhanced in three directions — scope, depth and rigor to provide more detailed description of possible applied techniques and tools for quantitative assessment.
The goals of the paper which overviews practical issues of diversity application are the following:
- present extended classification of diversity considering additional types of version redundancy for FPGA platform based I&Cs (logical processing equipment, life cycle, logic/algorithm etc.) in comparing to NUREG7007;
- describe the modified technique of diversity assessment taking into account three and more levels of diversity classification;
- illustrate and discuss variants of assurance of the required degree of diversity by use of the RadICS FPGA platform to develop main and diverse subsystems.
The classification is specified considering diversity of hardware and FPGA designs. In particular, diversity of hard logic and soft processors, interfaces and buses, self-diagnostics means and others are described and embedded into NUREG/CR-7007 classification.
The NUREG7007-based diversity assessment techniques supporting all stage of analyzing options are discussed, and algorithms for versions choice are described. This technique takes into account more detailed specification of diversity classification (for types, subtypes and sub-subtypes of diversity for logic diversity, logic processing equipment diversity and others) and options to evaluate weight coefficients.
Case study is based on description of two options of RadICS FPGA platform application to develop two-version NPP I&C, which meets standard requirements to diversity.
Quantitative changes in the ageing choriocapillaris as measured by swept source optical coherence tomography angiography
Authors: Sacconi Riccardo , Borrelli Enrico , Corbelli Eleonora , Capone Luigi , Rabiolo Alessandro , Carnevali Adriano , Casaluci Marco , Gelormini Francesco , Querques Lea , Bandello Francesco , Querques Giuseppe 
Published: October 2018

AimTo analyse quantitative optical coherence tomography angiography (OCTA) parameters of choriocapillaris (CC) at the foveal, perifoveal and parafoveal regions in healthy subjects of different age.MethodsIn this observational cross-sectional study, consecutive healthy subjects underwent swept source OCTA (PLEX Elite 9000, Carl Zeiss Meditec, USA). 3×3 mm and 6×6 mm scans centred on the fovea were acquired analysed and postprocessed with thresholding and binarisation processes. The main outcome measures included CC quantitative OCTA features (perfusion density (PD), vessel length density (VLD) and vessel diameter index (VDI)) at the foveal, perifoveal and parafoveal regions, and their relationship with age.ResultsSeventy-two eyes (72 patients, mean age 47.4±19.2 years, mean axial length 24.0±0.7 mm) were included. The mean PD was statistically lower in the foveal region compared with the parafoveal region in 3×3 mm scans (p=0.009). In subjects aged 70–80, PD of the foveal region was significantly reduced compared with the perifoveal region in 6×6 mm scans (p=0.008). A strong negative correlation was found between PD and ageing in the foveal, parafoveal and perifoveal regions (p<0.001 in all analyses). Furthermore, PD in the nasal-perifoveal region was significantly lower than the temporal-perifoveal region (p=0.005). No significant correlation was found between VLD and age in all regions, whereas VDI was strictly correlated with age (p<0.001).ConclusionsWe reported in vivo a strong negative correlation between PD and ageing in the CC of healthy subjects. This reduction seems related to a reduced diameter, and not to a reduced number, of capillaries. The age-related changes were higher in the central area compared with the perifoveal area.
Efficacy, effectiveness, and safety of herpes zoster vaccines in adults aged 50 and older: systematic review and network meta-analysis
Authors: Tricco Andrea C , Zarin Wasifa , Cardoso Roberta , Veroniki Areti-Angeliki , Khan Paul A , Nincic Vera , Ghassemi Marco , Warren Rachel , Sharpe Jane P , Page Andrea V , Straus Sharon E 
Published: October 2018

AbstractObjectiveTo compare the efficacy, effectiveness, and safety of the herpes zoster live attenuated vaccine with the herpes zoster adjuvant recombinant subunit vaccine or placebo for adults aged 50 and older.DesignSystematic review with bayesian meta-analysis and network meta-analysis.Data sourcesMedline, Embase, and Cochrane Library (inception to January 2017), grey literature, and reference lists of included studies.Eligibility criteria for study selectionExperimental, quasi-experimental, and observational studies that compared the live attenuated vaccine with the adjuvant recombinant subunit vaccine, placebo, or no vaccine in adults aged 50 and older. Relevant outcomes were incidence of herpes zoster (primary outcome), herpes zoster ophthalmicus, post-herpetic neuralgia, quality of life, adverse events, and death.Results27 studies (22 randomised controlled trials) including 2 044 504 patients, along with 18 companion reports, were included after screening 2037 titles and abstracts, followed by 175 full text articles. Network meta-analysis of five randomised controlled trials found no statistically significant differences between the live attenuated vaccine and placebo for incidence of laboratory confirmed herpes zoster. The adjuvant recombinant subunit vaccine, however, was statistically superior to both the live attenuated vaccine (vaccine efficacy 85%, 95% credible interval 31% to 98%) and placebo (94%, 79% to 98%). Network meta-analysis of 11 randomised controlled trials showed the adjuvant recombinant subunit vaccine to be associated with statistically more adverse events at injection sites than the live attenuated vaccine (relative risk 1.79, 95% credible interval 1.05 to 2.34; risk difference 30%, 95% credible interval 2% to 51%) and placebo (5.63, 3.57 to 7.29 and 53%, 30% to 73%, respectively). Network meta-analysis of nine randomised controlled trials showed the adjuvant recombinant subunit vaccine to be associated with statistically more systemic adverse events than placebo (2.28, 1.45 to 3.65 and 20%, 6% to 40%, respectively).ConclusionsUsing the adjuvant recombinant subunit vaccine might prevent more cases of herpes zoster than using the live attenuated vaccine, but the adjuvant recombinant subunit vaccine also carries a greater risk of adverse events at injection sites.Protocol registrationProspero CRD42017056389.
Strategic purchasing for universal health coverage: examining the purchaser–provider relationship within a social health insurance scheme in Nigeria
Authors: Etiaba Enyi , Onwujekwe Obinna , Honda Ayako , Ibe Ogochukwu , Uzochukwu Benjamin , Hanson Kara 
Published: October 2018

BackgroundIn an attempt to achieve universal health coverage, Nigeria introduced a number of health insurance schemes. One of them, the Formal Sector Social Health Insurance Programme (FSSHIP), was launched in 2005 to provide health cover to federal government and formal private sector employees. It operates with two levels of purchasers, the National Health Insurance Scheme (NHIS) and health maintenance organisations (HMOs). This study critically assesses purchasing arrangements between NHIS, HMOs and healthcare providers and determines how the arrangements function from a strategic purchasing perspective within the FSSHIP.MethodsA qualitative study undertaken in Enugu state, Nigeria, data were gathered through reviews of documents, 17 in-depth interviews (IDIs) with NHIS, HMOs and healthcare providers and two focus group discussions (FGDs) with FSSHIP enrolees. A strategic purchasing lens was used to guide data analysis.ResultsThe purchasing function was not being used strategically to influence provider behaviour and improve efficiency and quality in healthcare service delivery. For the purchaser–provider relationship, these actions are: accreditation of healthcare providers; monitoring of HMOs and healthcare providers and use of appropriate provider payment mechanisms for healthcare services at every level. The government lacks resources and political will to perform their stewardship role while provider dissatisfaction with payments and reimbursements adversely affected service provision to enrolled members. Underlying this inability to purchase, health services strategically is the two-tiered purchasing mechanism wherein NHIS is not adequately exercising its stewardship role to monitor and guide HMOs to fulfil their roles and responsibilities as purchasing administrators.ConclusionsPurchasing under the FSSHIP is more passive than strategic. Governance framework requires strengthening and clarity for optimal implementation so as to ensure that both levels of purchasers undertake strategic purchasing actions. Additional strengthening of NHIS is needed for it to have capacity to play its stewardship role in the FSSHIP.
Equity and determinants of routine child immunisation programme among tribal and non-tribal populations in rural Tangail subdistrict, Bangladesh: a cohort study
Authors: Rahman Aminur , Reza Ashek Ahmed Shahid , Bhuiyan Badrul Alam , Alam Nurul , Dasgupta Shushil K , Mostari Shabnam , Anwar Iqbal 
Published: October 2018

ObjectivesThe study estimated valid vaccination coverage of under 5 children in a rural area under Tangail subdistrict and examined their sociodemographic correlates including ethnicity.SettingThe study sites are three primary areas where tribal and non-tribal population resides together in a rural subdistrict of Bangladesh.ParticipantsRoutine vaccination information of a cohort of 2802 children, born between 1 January 2011 and 31 December 2012, were retrieved from the Expanded Program on Immunization (EPI) registers maintained by the health assistants. Collected data were entered in an Oracle-based computer program. Univariate, bivariate and multivariate analyses were performed in SPSS V.20 to explore coverage and differentials for full valid vaccination coverage in the study area.ResultsValid vaccination coverage was 90.6% among tribal population and 87.3% among non-tribal population(p=0.25). Compared with females, males had higher valid vaccination coverage (89.2% vs 85.9%) and lower invalid (5.4% vs 6.9%) and no-coverage (5.3% vs 7.3%) (p=0.03). Households with mobile phones had higher valid coverage (90.9% vs 86.5%) and lower invalid (4.5% vs 6.7%) and no coverage (4.5% vs 6.9%) compared with those without mobile phones (p=0.01). Coverage of valid vaccination was higher among children of Oronkhola union than in children of the other two unions.ConclusionThe study documented that valid vaccination coverage was high in this rural area, and there was no significant ethnic variation which was one of the strengths of the national EPI. However, there is significant variation by gender of the child, household ownership of mobile phones and geographical location of households.
Self-rated health among migrants from the former Soviet Union in Germany: a cross-sectional study
Authors: Stolpe Susanne , Ouma Mary , Winkler Volker , Meisinger Christa , Becher Heiko , Deckert Andreas 
Published: October 2018

ObjectivesTo assess the status and change in self-rated health among Aussiedler, ethnic German immigrants from the former Soviet Union, as a predictor for premature death 10 years after first assessment. Moreover, to identify subgroups which are particular at risk of anticipated severe health impairment.DesignCross-sectional questionnaire.SettingThe study was conducted in the catchment area of Augsburg, a city in southern Bavaria, Germany, in 2011/2012 that has a large community of Aussiedler.Participants595 Aussiedler (231 male, 364 female, mean age 55 years) who in majority migrated to Germany between 1990 and 1999.OutcomePrimary outcome: self-rated health (very good/good/not so good/bad) and its association with demographic, social and morbidity related variables.MethodsSelf-rated health was dichotomised as ‘very good’ and ‘good’ versus ‘not so good’ and ‘bad’. Multivariable logistic models were created. Missing values with regard to pain were addressed by a second analysis.ResultsAlthough low response suggests a healthier sample, the findings are alarming. Altogether47% of the Aussiedler perceived their health as less than good, which is worse compared with the first assessment in 2000 (25% compared with 20% of the general public). Prevalence of high blood pressure was present in 52% of Aussiedler, 34.5% were obese, 40.7% suffered from frequent pain and 13.1% had diabetes mellitus. According to the multivariable models, individuals suffering from pain, limited mobility, diabetes mellitus and high blood pressure are particularly in jeopardy.Conclusions10 years after the first assessment of self-rated health among Aussiedler their situation deteriorated. Tailored risk factor counselling of general practitioners is highly recommended.