bluuebunny/crossref_metadata_2025 huggingface dataset:
Gut microbiome‐targeted therapies as adjuvant treatments in inflammatory bowel diseases: a systematic review and network meta‐analysis
Authors: Zhang Tao , Li Xiaoang , Li Jun , Sun Feng , Duan Liping
Published: November 2024

Background and Aim

Gut microbiome‐targeted therapies (MTTs), including prebiotics, probiotics, synbiotics, and fecal microbiota transplantation (FMT), have been widely used in inflammatory bowel diseases (IBD), but the best MTTs has not yet been confirmed. We performed a network meta‐analysis (NMA) to examine this in ulcerative colitis (UC) and Crohn's disease (CD).

Methods

We searched for randomized controlled trials (RCTs) on the efficacy and safety of MTTs as adjuvant therapies for IBD until December 10, 2023. Data were pooled using a random effects model, with efficacy reported as pooled relative risks with 95% CIs, and interventions ranked according to means of surfaces under cumulative ranking values.

Results

Thirty‐eight RCTs met the inclusion criteria. Firstly, we compared the efficacy of MTTs in IBD patients. Only FMT and probiotics were superior to placebo in all outcomes, but FMT ranked best in improving clinical response rate and clinical and endoscopic remission rate, and probiotics ranked second in reducing clinical relapse rate showed significant efficacy, while prebiotics ranked first showed nonsignificant efficacy. Subsequently, we conducted NMA for specific MTT formulations in UC and CD separately, which revealed that FMT, especially combined FMT via colonoscopy and enema, showed significant efficacy and was superior in improving clinical response and remission rate of active UC patients. As for endoscopic remission and clinical relapse, multistrain probiotics based on specific genera of Lactobacillus and Bifidobacterium showed significant efficacy and ranked best in UC. In CD, we found that no MTTs were significantly better than placebo, but synbiotics comprising Bifidobacterium and fructo‐oligosaccharide/inulin mix and Saccharomyces ranked best in improving clinical remission and reducing clinical relapse, respectively. Moreover, FMT was safe in both UC and CD.

Conclusions

FMT and multistrain probiotics showed superior efficacy in UC. However, the efficacy of MTTs varies among different IBD subtypes and disease stages; thus, the personalized treatment strategies of MTTs are necessary.
Correlation of serum chloride concentrations with components of the renin‐angiotensin‐aldosterone system in a dog with congestive heart failure
Authors: Banken Cailey , Harris Autumn N. , Conway Rachel , Benjamin Eduardo J. , Shoemaker Robin , Adin Darcy
Published: November 2024

A 7‐year‐old male castrated Cavalier King Charles Spaniel was hospitalized for 12 days for treatment of severe congestive heart failure secondary to myxomatous mitral valve disease. During that time, 6 serum samples from different days were analyzed for serum biochemical and renin‐angiotensin‐aldosterone system components. Serum chloride concentrations (ranging from 71.6 to 103.1 mmol/L) were inversely related to angiotensin I concentrations, aldosterone concentrations, a surrogate marker of renin activity, and a surrogate marker of adrenal responsiveness to angiotensin II. In light of recent studies showing that hypochloremia is associated with advanced heart failure in dogs and is associated with poor outcomes in people, the information from the dog in this report supports exploration of RAAS dysregulation as an underlying mechanism.
Long‐run Effects of Austerity: An Analysis of Size Dependence and Persistence in Fiscal Multipliers
Authors: Klein Martins Guilherme
Published: November 2024

This paper provides evidence that austerity shocks have long‐run negative effects on GDP. Our baseline results show that contractionary fiscal shocks larger than 3% of GDP generate a negative effect of more than 5.5% on GDP even after 15 years. Evidence is also found linking austerity to smaller capital stock and total hours worked in the long‐run. The results are robust to different fiscal shock datasets, the exclusion of particular shocks, and the use of cleaner controls. The paper also engages with the emerging discussion regarding fiscal multipliers heterogeneity, presenting evidence that the effects of exogenous fiscal measures are nonlinear on the shock size. The results also contribute to the broader discussion on the long‐run effects of demand by suggesting that such shocks might permanently affect the economy.
Assessment of parental self‐efficacy in managing child food‐induced anaphylaxis and using adrenaline autoinjectors
Authors: Polloni Laura , Baldi Ileana , Bianconi Sara , Amadi Margherita , Tonazzo Valentina , Bonaguro Roberta , Lazzarotto Francesca , Toniolo Alice , Morandini Laura , Schiavo Rossana , Muraro Antonella
Published: November 2024

Background

Anaphylaxis is a life‐threatening allergic reaction, associated with mental health burden in patients and caregivers. Intramuscular adrenaline via autoinjector (AAI) is the recommended treatment for the management of anaphylaxis in non‐hospital settings; however, AAIs are underused. This study aimed to assess parental self‐efficacy in managing child's anaphylaxis and administering AAI to understand how to effectively support families.

Methods

Seventy‐five parents of children with severe food allergy completed a questionnaire to measure parental self‐efficacy in managing child food‐induced anaphylaxis (PSEMA). We conducted an exploratory factor analysis with 12 items, using principal axis factoring as the extraction method. We used Cronbach's alpha to assess the internal consistency of the factors. We used the Anderson–Rubin approach to estimate the factors' scores and provide a kernel density estimate of their distributions. An assessment through linear regression between the total factors' score and total score was performed.

Results

A five‐factor model was identified. The factors that emerged were conceptually related to “F1. Manage Injection,” “F2. Manage AAI Device,” “F3. Manage Anaphylaxis,” “F4. Manage Emergency,” and “F5. Manage Emotions.” The questionnaire demonstrated high internal consistency, with a Cronbach's alpha of 0.91 (95% CI: 0.87–0.94) The variation in the total score explained 90% of the variation in the factor score.

Conclusions

The PSEMA questionnaire promises to be an easy and effective tool for measuring parents' self‐efficacy in managing anaphylaxis and AAI, allowing clinicians to identify gaps in education and provide effective training.
Age‐related differences of the time‐varying features in the brain functional connectivity and cognitive aging
Authors: Yao Furong , Zhao Ziyang , Wang Yin , Li Tongtong , Chen Miao , Yao Zhijun , Jiao Jin , Hu Bin
Published: November 2024

Brain functional modular organization changes with age. Considering the brain as a dynamic system, recent studies have suggested that time‐varying connectivity provides more information on brain functions. However, the spontaneous reconfiguration of modular brain structures over time during aging remains poorly understood. In this study, we investigated the age‐related dynamic modular reconfiguration using resting‐state functional MRI data (615 participants, aged 18–88 years) from Cam‐CAN. We employed a graph‐based modularity analysis to investigate modular variability and the transition of nodes from one module to another in modular brain networks across the adult lifespan. Results showed that modular structure exhibits both linear and nonlinear age‐related trends. The modular variability is higher in early and late adulthood, with higher modular variability in the association networks and lower modular variability in the primary networks. In addition, the whole‐brain transition matrix showed that the times of transition from other networks to the dorsal attention network were the largest. Furthermore, the modular structure was closely related to the number of cognitive components and memory‐related cognitive performance, suggesting a potential contribution to flexibility cognitive function. Our findings highlighted the notable dynamic characteristics in large‐scale brain networks across the adult lifespan, which enhanced our understanding of the neural substrate in various cognitions during aging. These findings also provided further evidence that dedifferentiation and compensation are the outcomes of functional brain interactions.
Presumed calcific band keratopathy in a 10‐month‐old domestic shorthair cat
Authors: Ferruz‐Fernandez Marta , Ripolles‐Garcia Ana , Caro‐Suarez Miriam , Latre‐Moreno Almudena , Jimenez‐Ramos Laura , Rodriguez‐Gavilan Maria Paloma , Naranjo Carolina , Laguna Fernando , Villagrasa Manuel
Published: November 2024

Objective

To describe a case of presumed band keratopathy in a young cat with no known history of corneal disease who was not receiving topical phosphate‐based steroids.

Animal Studied

A 10‐month‐old domestic shorthair cat was evaluated for severe ocular discomfort that did not improve despite the initiation of topical antibiotic treatment.

Methods

A complete ophthalmic examination and ancillary tests such as biomicroscopy and corneal cytology were performed at the time of presentation. A superficial lamellar keratectomy was excised, and the corneal button was sent for histopathology. In addition to routine hematoxylin–eosin staining, sections were stained with Gram, PAS, von Kossa, and trichrome stains.

Results

Biomicroscopic examination revealed an extensive corneal epithelial ulcer with a hard white plaque in the central area of the right cornea with associated superficial neovascularization. Ultrasound biomicroscopy showed a 0.63 mm, slightly hyperechoic band in the anterior corneal stroma. Corneal cytology evidenced numerous neutrophils with toxic changes and few macrophages. Histopathologic analysis excluded corneal sequestration as a differential diagnosis and confirmed superficial corneal mineralization. At the last follow‐up, 16 months after surgery, corneal transparency had returned, and visual acuity was good with some corneal conjunctivalization.

Conclusions

In this case report, the presumptive diagnosis is calcific band keratopathy. To the best of the author's knowledge, this is the first presumed case in a cat not receiving topical phosphate‐based steroids and without previous corneal damage. Lamellar keratectomy represents a curative approach that successfully resolved the clinical signs, with no reported recurrence.
The novel use of a sub‐palpebral lavage line as an indwelling stent to manage unilateral nasolacrimal duct obstruction in a cat
Authors: Bowden Anna Catherine , Allbaugh Rachel A.
Published: November 2024

Objective

To describe a novel surgical approach to conjunctivorhinostomy for feline nasolacrimal duct obstruction.

Animal Studied

A client‐owned 4‐year‐old female spayed domestic shorthair cat presented with chronic unilateral nasolacrimal duct obstruction of the right eye.

Methods

Following obstruction confirmation via complete ophthalmic examination and dacryocystorhinography, conjunctivorhinostomy was performed under general anesthesia, and an indwelling sub‐palpebral lavage (SPL) line was placed to facilitate the formation of a new pathway for tear drainage. Specifically, the SPL footplate was sutured to the ventral conjunctival fornix with 5‐0 nylon and 6‐0 vicryl while the tubing was passed through the new pathway and the distal end of the tubing trimmed and tucked into a perinasal subcutaneous pocket. Two skin sutures closed the perinasal pocket and were removed 2 weeks postoperatively.

Results

No immediate postoperative complications occurred. At 6 weeks and 6 months postoperatively, the distal SPL tubing was dislodged and visible out of the right nostril. This was uneventfully trimmed shorter, and no further complications occurred. The SPL component was easily removed 11 months postoperatively without complication. The patient's clinical signs dramatically improved; she was comfortable over 2 years after surgery.

Conclusion

To the authors' knowledge, this is the first report of using an SPL as an indwelling catheter for nasolacrimal duct surgery via conjunctivorhinostomy in a cat. This technique eliminated external stent sites for the patient, which was associated with a short use of an e‐collar, and utilized materials readily available in a specialty hospital.
Atomistic and Theoretical Insights on Nanoprecipitates-Controlled Strengthening Behavior for Optimum Mechanical Performance in Nanotwinned NiCoCr Alloys
Authors: Yu Zihao , Zhang Yujie , Wang Hongyu , Sun Ligang , Guo Xiang , Zhu Linli
Published: November 2024

The nanoprecipitates and nanotwins enable to improve the mechanical performance of NiCo-based alloys. In this work, the molecular dynamics (MD) simulations are performed to investigate the strengthening mechanisms of nanotwinned medium-entropy NiCoCr alloys with various distributions and volume fractions of nanoprecipitates. MD simulations reveal that mechanical performance for the precipitates located in twin boundaries is better than that located in the twin lamellae. The precipitate-induced strengthening makes the nanotwinned NiCoCr alloys to achieve the maximum flow stress during increasing the precipitate volume fraction. The influences of volume fraction and distribution of the precipitate on winding and cutting mechanisms are analyzed comprehensively. The dislocation winding behavior, hindered twin boundaries deformation, and the adjacent precipitates connection control the precipitate strengthening mechanisms. A dislocation-based theoretical model is developed to forecast the size-dependent flow stress of nanotwinned metals with nanoprecipitates, in which the Orowan bypass mechanism and the dislocation pile-up behaviors are involved. The relationship between the microstructural size and the flow stress of nanotwinned metallic materials with nanoprecipitates is explored. The predictions for the flow stresses varied with the precipitate volume fraction are agreeable well with the results of MD simulation. The predicted maximum flow stresses and the corresponding critical volume fractions of nanoprecipitates are sensitive to the microstructural sizes.
Design and Development of Scissorbot: A Novel Mid-Flight-Span-Reducing Quadcopter
Authors: Kulkarni Eeshan , Sundaram Suresh
Published: November 2024

This article presents the design and development of Scissorbot, a novel mid-flight reconfigurable geometry quadcopter that reduces its lateral-span using a single servomotor coupled with a compact bevel differential gearbox. Scissorbot possesses unique practical features, including geometrical symmetricity, fault tolerance to the servomotor, and the gearbox’s weight-scalability. Scissorbot achieves significant lateral-span reduction without the risk of propeller tip collision by positioning adjacent propellers in different planes. To the best of author’s knowledge, the maximum lateral-span reduction surpasses any controllable morphing quadcopter reported in the literature. This work derives a detailed attitude dynamics model and conducts a theoretical analysis of the gearbox. The attitude control is accomplished through the implementation of a robust controller, which exhibits exponential tracking, even in the presence of parametric uncertainties, and propeller aerodynamics disturbances. A velocity controller augments the attitude controller. The control allocation loop is parametrized to adapt to the reconfiguration process. Various evaluations, encompassing multibody simulations and hardware flight experiments, assess Scissorbot’s performance. The results unequivocally demonstrate controller’s excellent tracking in simulations and on the hardware prototype across all scenarios. Moreover, the experiments validate the fault tolerance feature of Scissorbot. In addition, a comprehensive study is performed to analyze the scalability of the current gearbox for higher-weight Scissorbot prototypes.
Comparison of Theoretical Methods Describing the Heat Transfer in Vertical Tube Condensers Under Conditions Corresponding to the Condensation of Flue Gas From a Biomass Boiler
Authors: Krempaský Jakub , Havlík Jan , Dlouhý Tomáš
Published: November 2024

A theoretical and experimental study was conducted on the condensation of water vapor in a vertical tube condenser under conditions corresponding to the condensation of flue gas from a biomass boiler, where flue gas is considered a mixture of water vapor and a high content of noncondensable gas (NCG). Four fundamental theoretical methods were identified for determining the heat transfer coefficient and condenser heat output—empirical correlations, heat and mass transfer analogy, diffusion layer theory, and boundary layer theory. These methods were compared in terms of their usability in the design of flue gas condensers in energy systems and experimentally verified. Experiments were carried out in a 1.5 m long vertical double-pipe condenser with a condensing gas flowing in a downward direction through an inner tube with a diameter of 25 mm. The mass concentration of NCG in a mixture with water vapor ranged from 11 vol% to 86 vol% and the inlet Reynolds number of the condensing gas ranged from 1936 to 14,408, which corresponds with the conditions of condensing flue gas from biomass boilers. The boundary layer theory is highly complex and impractical for the calculation of heat exchangers. Empirical correlations have a wide dispersion of the result, because they consider only the fundamental parameters of the process. Nevertheless, heat and mass transfer analogy and diffusion layer theory seem to be the most suitable for flue gas condensers since they capture the physical essence of the phenomena.
Analyzing Flow Rate Impact on CHF Front Behavior During Boiling Crisis in Downward Flow Boiling
Authors: Wang Shixian , Wang Kai , Miwa Shuichiro , Okamoto Koji
Published: November 2024

Our research thoroughly examines the Critical Heat Flux (CHF) in downward-facing flow boiling, essential for comprehending the intricacy of the CHF phenomenon. Conducted on a downward-facing copper surface within a flow loop, our research uncovered significant differences in CHF between upstream and downstream regions, with CHF predominantly occurring downstream first. High-speed camera analysis during boiling crisis led to the identification of the ‘CHF front,’ marking the transition from nucleate to film boiling phases. This CHF front typically originates downstream and progresses upstream, significantly influencing final CHF thresholds. This movement, linked to dry spot formation on the heated surface as per dry-out theories, is a key focus of our analysis. Furthermore, our experiments on smooth copper surfaces under varied flow rates revealed that increased flow rates decrease the CHF front velocity, delaying CHF onset and resulting in higher final CHF values. This observed effect is attributed to the enhanced supply of liquid to the micro-layer beneath the bubble, which increases its thickness and thereby prevents the formation of dry spots. While our study offers deep insights, we recognize uncertainties in our data. Future research will focus on various factors for a more comprehensive understanding of CHF front velocity. These findings are crucial for predicting CHF levels in various systems, marking a significant contribution to the field.
Dynamic Matrix Control for Cold Helium Temperature of Multi-Modular High Temperature Gas-Cooled Reactor Plant
Authors: Zhendong Wu , Zhe Dong
Published: November 2024

The coordination control strategy for operational multi-modular high temperature gas-cooled reactors primarily considers process variables such as neutron flux, main steam temperature, and hot helium temperature, yet it does not address the control of cold helium temperature. Inappropriate cold helium temperatures can lead to structural material fatigue, impact the lifespan of instrumentation at the core’s top, and consequently degrade the operational reliability of nuclear power plants. Additionally, cold helium temperature reflects the thermal balance between the primary and secondary loops, underscoring the necessity of controlling cold helium temperature.

In response, a method using dynamic matrix control (DMC) is proposed to control cold helium temperature by adjusting the hot helium temperature setpoint. A step response model with cold helium temperature data is used to design DMC. Utilizing the stability of the existing proportional-integral-derivative (PID) controller and the optimization capabilities of DMC, a cascaded control structure is established. PID acts as the inner loop for stability, and DMC as the outer loop corrects the hot helium temperature setpoint, achieving cascaded control for cold helium temperature in multi-modular high temperature gas-cooled reactors.

Numerical simulations based on a 1000MW ten-module high temperature gas-cooled reactor program validated the effectiveness of the proposed control method. The results demonstrate that the controller can effectively regulate the cold helium temperature without compromising the control of other key variables.
Simulation Calculation of the Utilization Rate of Uranium Resources on the ADANES Fuel Cycle
Authors: Yan Xuesong , Gao Yucui , Zhang Yaling , Yang Lei
Published: November 2024

Accelerator Driven Advanced Nuclear Energy System (ADANES) is composed of Accelerator Driven subcritical System (ADS) burner and regeneration system of spent fuel, which can solve the challenging problems of low utilization efficiency of uranium resources and difficult safe disposal of spent fuel. The proportion of U-238 in spent fuel of pressurized water reactors is ∼95%, fission products are 3∼4%, and other actinide nuclides are 1∼2%. The regeneration system of spent fuel is mainly to eliminate part of fission products, including volatile, semi-volatile and rare earth nuclides, remaining nuclides to form regenerated spent fuel (mainly including actinides and other fission products). It does not perform fine separation. ADS burner can burn the regenerated spent fuel, so that ADANES can realize power generation, transmutation and proliferation for multiple fuel cycles. ADANES aims to increase the utilization rate of uranium resources to 95% and generate very little radioactive waste with a short radioactive life. At present, the preliminary principle verification device of the burner Chinese Initial ADS has been successfully applied and will be constructed in 2027. In this work, the neutron physics effects of these nuclides (volatile, semi-volatile and rare earth nuclides) on the ADS reactor core will be studied. The ADS burner can directly utilize regenerated spent fuel because of its powerful external neutron source. After removing 100% of volatile, semi-volatile and more than 50% of rare earth nuclides from the spent fuel of PWR, 3GWth ADS burner can burn the remaining spent fuel for 10∼20 years. The Keff of the reactor core will first increase to its peak and then continuously decrease, this is due to the production of plutonium-239, the consumption of uranium-235 and production and accumulation of neutron toxins. Under subcritical operating conditions of the reactor, the mass of U-235 will consume > 99% and U-238 will consume > 70% during 100 years. Meanwhile, a large amount of Pu-239 has also proliferated. The generated Pu-239 is equivalent to the consumed U-235. We attempt to calculate the number of cycles and fuel utilization on a feasible basis. Specific analysis was conducted on the requirements for initial Keff of ADS reactor core and accelerator beam intensity. More the 5 regeneration system and nuclear fuel cycle will be simulated. As the number of cycles increases, the utilization of U-238 will continue to increase. After all, there will be more and more fission products accumulated in spent fuel, which will affect the burnup level.
A Method Using Strong Tracking Filter for Compensating the Response Delay of Self-Powered Neutron Detectors
Authors: Liu Shiyu , Zhang Qingmin , Liu Jinliang , Sang Yaodong , Shao Zhuang , Zhu Kangfu
Published: November 2024

Self-Powered Neutron Detector (SPND) has been widely used for monitoring neutron flux in reactors. There are two typical types of SPNDs, including prompt type and delayed type. The prompt type SPNDs’ output current are mainly contributed by gammas generated from the neutron capture process.

Rhodium SPND is a typical delayed type SPND and has been widely used for neutron flux monitoring in reactors. Compared with other prompt SPNDs such as Cobalt SPND, Rh-SPND contains a higher neutron sensitivity.

However, long response time and high noise gain are the main problems that restrict the application of SPNDs with delayed current components. In order to solve the above two problems, a method using the Strong Tracking Filter has been proposed in this paper. Compared to the traditional Kalman Filter, Strong Tracking Filter will offer robustness to the modeling errors and ensure the whiteness property of the filter innovation sequence. This gives Strong Tracking Filtering a high adaptivity to sudden changes (e.g. reactor load rejection) in the useful signal, even in the presence of noise. Following the derivation of the ideal iterative inversion relation from current to neutron flux, a filtering matrix containing noise filtering and neutron flux inversion was established using Strong Tracking Filter. Then it’s shown that this method can give a shorter response time than the Kalman Filter method for the same noise gain, and its strong robustness to initial values and sampling frequency was also demonstrated by the test. Finally, this method was used to obtain the real-time neutron flux from the SPND current in the other reference, demonstrating its effectiveness and excellence.
Transient Analysis of the Loss of Heat Sink Accident in a New Type of Megawatt Heat Pipe Reactor
Authors: ZhenLan Wang , JunLi Gou , LeQi Yuan , JianQiang Shan
Published: November 2024

Heat pipe reactors are one of the ideal reactor types for Unmanned Underwater Vehicles (UUVs) due to high energy density, long lifecycle, modularity, and compact structure. In the reactor concept design stage, simulation and analysis of typical accidents on heat pipe reactors are key to assessing their inherent safety. The loss of heat sink accident, as one of the typical accidents in heat pipe reactors, is of great significance to the safety performance evaluation. In this study, the transient models of the passive residual heat removal system (PRHRS), including the one-dimensional flow model, the constitutive model of heat transfer, and the constitutive model of pressure drop, are developed based on the completed design of the PRHRS. Based on the models, a transient coupling analysis code for the loss of heat sink accidents is developed, which combines with the transient analysis code for heat transfer in a new type of megawatt heat pipe reactor (HTR) and the transient analysis code for the natural circulation of cooling water (SCTRAN). The results of the coupling analysis code are validated against the results of the STAR-CCM+ during the steady-state operation, with the maximum error not exceeding 8.13%. The coupling analysis code is also used to analyze the transient characteristic of the PRHRS during the loss of heat sink accident with different delayed emergency reactor shutdown times. After the loss of heat sink accident, the cooling water in the emergency cooling component (ECC) is natural flow driven by density differences without external power. Before the reactor is shut down, the heat generated in the core can only be removed through the PRHRS, and the temperature of the core remains to rise. As the heat removal capacity of the PRHRS increases and the reactor shuts down, the fuel and heat pipes gradually cool down after reaching the peak temperature, and the waste heat of the core is gradually removed. The results show that with the delayed emergency reactor shutdown time within 23s after the loss of heat sink accident, the PRHRS can remove the residual heat of the core in a timely manner, no boiling occurs in the ECC, and the temperatures of the core are lower than the temperature limit, which reflects the good safety of the new type of megawatt heat pipe reactor in the accident of the loss of heat sink.
Capability for Volume Reduction of Concrete Contaminated by Radioactive Carbon Dioxide Using Rubbing
Authors: Kinoshita Norikazu , Nakashima Hitoshi , Saito Akira , Hanzawa Mamoru , Sasaki Yuki , Torii Kazuyuki
Published: November 2024

A large amount of concrete contaminated by 14CO2 will be discharged from decommissioning of aged nuclear power plants. Rubbing, which separates cements from concrete debris, would be one of manners which allows to reduce volume of the waste if most of the 14C presents in the cement inside the concrete. We confirmed that the 14CO2 adsorbs on the cements more than aggregates by a factor of approximately 2 orders. Rubbing was carried out to obtain the mass balance and decontamination factor using simulated concrete debris which was not contaminated by the 14CO2. The cements and fine aggregates were separated from the debris as fines by rubbing using a Los Angeles testing machine. Steel balls with different size and different amount were used to proceed rubbing more. In addition, production rates of the fines were investigated in the debris that the heat treatment was carried out or not. Residues in a mill of the Los Angeles testing machine were washed to remove deposits remained on the surface. We concluded that the volume reduction can be effectively achieved by rubbing the debris that applied the heat treatment using more steel balls with larger size. DF was not improved by washing the surface residues. However, washing can resolve the concerns regarding radiation protection due to scattering of fines contaminated with the 14CO2 in treatment of the residues after rubbing.
Study on the Improvement of RELAP5 Post-Critical Boiling Heat Transfer Model for the Submerged Cooling Process of Rectangular Channel
Authors: Zhong Lei , Yu Hongxing , Ling Chen , Chen Deqi , Deng Jian , Liu Haidong , Xu Jun
Published: November 2024

RELAP5 has some shortcomings in calculating the submerged cooling process of rectangular channels, especially in the post critical heat transfer model. Based on the experimental data of submerged cooling in rectangular channel, the droplet flow precursor cooling heat transfer model, transition boiling model and minimum film boiling temperature model suitable for the submerged cooling process in rectangular channel are obtained in this paper. The secondary development is carried out on the basis of RELAP5 program, and the droplet flow precursor cooling heat transfer model, transition boiling model and minimum film boiling temperature model obtained in this paper are implanted. Through the comparative analysis of program calculation results and experimental data, the results show that the calculated values of this model are in good agreement with the experimental data, and compared with the existing calculation models, this model has good applicability to calculate the submerged cooling process of rectangular channel.
Climate Change: Overview of the Process and Methodologies Used by EDF for Taking Into Account the Effects of Climate Change in the Design of Nuclear Power Plants
Authors: Cordier Hervé , Joly Amélie
Published: November 2024

Climate Change is one of the greatest environmental challenges facing the world. Its effects are systemic and evolutive because of its dependance with human activities. The Intergovernmental Panel on Climate Change (IPCC) highlights that the world efforts to reduce greenhouse gases emissions are not on track to limit global warming to 1.5°C by 2100 in comparison to pre-industrial era.

As several countries, France signed a legal duty to reach Net Zero by 2050. Generation of low carbon electricity is part of solutions required to meet the Net Zero target. EDF operating nuclear fleet in France updated its life cycle analysis leading to a carbon footprint of 4 grams of CO2 equivalent per kWh [1]. On one hand, this result highlights that alongside renewables, nuclear facilities are part of the solutions to reduce greenhouse gases emissions. On the other hand, those facilities require to be adapted and resilient to the effects of Climate Change for their entire lifetime.

For Nuclear Facilities, Climate Change can impact safety, electricity generation and environmental impacts during the different steps of the facility development (design, building) and for its entire lifetime (operation and decommissioning).

Considering the possible effects of climate change, EDF has developed a systemic and evolutive approach to design and manage the adaptation process of its nuclear facilities with climate change. This approach called “ADAPT program” is structured around 4 pillars (understand, characterize, mobilize and act) and 4 work packages: (i) natural and water resources, (ii) industrial facility, (iii) supply chain local logistics work conditions and (iv) local environment of the Nuclear Power Plant (NPP).

In this article, we focus on the industrial facility work package. The whole process is described, and the goals of the different steps are explained as well as the principles applied to integrate the effects of climate change in the process. The risk assessment step is detailed. An example for the design against heatwaves is given for new and existing Nuclear Power Plant.
Preliminary Study on Endoscopic Ultrasound System for In-Service Inspection of Helical Tube Once-Through Steam Generator
Authors: Xi Ze , Wang Xiangang , Luo Xiaowei , Zhou Junjie , Song Lei
Published: November 2024

The Helical-tube Once-through Steam Generator (H-OTSG) is a crucial component of the gas-cooled reactor, with the helical heat exchanger tube in the H-OTSG forming an integral part of the reactor’s primary pressure boundary. The volumetric in-service inspection of this helical heat exchanger tube presents a significant challenge due to constraints of accessibility, material, and weld inspection. To address this problem, an Endoscopic Ultrasound (EUS) inspection system is proposed. The structure and working mode of the EUS inspection system are described in detail. Then, the key sensor of the inspection system, EUS transducer, is presented and highlighted. Three array EUS transducers are designed. After outlining the geometric model and inspection modality of the EUS transducers, a preliminary EUS inspection experiment is conducted to demonstrate the inspection performance of the transducers. Two types of reflectors are fabricated on an actual H-OTSG’s heat exchanger tube in the High-Temperature Reactor Pebble-bed Module (HTR-PM) according to ASME code methods to simulate the volumetric and planar defects in different positions. The experimental results show that the proposed array EUS transducers offer high detection robustness and excellent sizing ability on account of the 3-D focused acoustic beam.
Geometric Uncertainty Analysis of Fuel Assembly Based on Sub-Channel Model
Authors: Kong Deyan , Gao Zhibo , Wu Di , Cheng Jie , Wang Jianjun
Published: November 2024

There are inevitably geometric uncertainties during the machining and installation of fuel rods, such as the pitch and diameter of each fuel rod, which can lead to changes in the thermal and hydraulic characteristics of the reactor. In this study, a method is proposed to simulate geometric uncertainties as realistically as possible for subchannel models. In this method, each rod is disturbed individually, including the diameter of the fuel rod, the offset distance and the offset Angle. At the same time, a 3 × 3 rod bundle channel model of pressurized water reactor (PWR) is established based on the subchannel model, which contains 8 fuel rods and 1 guide tube. Latin hypercube sampling (LHS) method was used to extract samples, and different perturbations were made to 9 rods at the same time, and then the influence of geometric uncertainty was refined. Coolant temperature, and fuel rod center temperature were selected as figures of merit (FOMs) because these parameters are the most concerned in the thermal hydraulic analysis of the reactor. The LHS method was used to generate 5000 groups of parameters, their relative uncertainties were measured, and the upper and lower limits of tolerance interval and the range of tolerance interval were measured by Wilks’ method. The results show that the uncertainty of output parameters is different at different locations. In general, the tolerance range of maximum coolant temperature and maximum fuel rod center temperature is about 0.7 K and 2.2 K.
Performance Analysis and Optimization Scheme Evaluation of Control Rod Drop Collision in Gas-Cooled Microreactor
Authors: Dong Hao , Qi Anzhou , Jiang Xiaochuan
Published: November 2024

In the case of rod drop accident in high temperature gas-cooled reactor, the control rod is completely inserted into the core in a state of approximate free fall by its own gravity, thus realizing reactor shutdown. In this process, the control rod will generate great kinetic energy with the falling process, and it will impact with the lower reflector of the reactor, resulting in the destruction of graphite and control rod structure in the reflector, and it is impossible for graphite components to be repaired within the service life, and the control rod is not easy to be replaced, so it is urgent to study and optimize the collision between the lower end of the control rod and the graphite reflector in the rod falling accident.

At present, there are many kinds of cushioning devices in engineering to alleviate the impact. It is common to fill foam-like materials or honeycomb-like materials between the two interfaces where the impact occurs, so as to absorb the impact load and realize the protection of components. However, due to the particularity of high temperature and long life of nuclear reactors, the above-mentioned solution using filling materials cannot be adopted. In addition, there is a scheme of using crush elements. At present, some scholars have studied the theoretical model and numerical simulation of crush shell. In the field of reactors, the scheme of buffering together with fluid resistance in pressurized water reactors and arranging crush elements on the bottom reflection layer of the core in high temperature gas-cooled reactors is widely used. However, the two schemes are not suitable for the core design of high-temperature gas-cooled reactor with high temperature, and are not easy to take out and replace, so their adaptability is limited.

In this paper, ANSYS/LS-DYNA finite element simulation program is used. Firstly, the optimization effects of the innovative spring-type and cylindrical thin-wall crushing buffer structures are compared, and then the influence of wall thickness on collision and thin-wall deformation is studied with emphasis on the scheme of cylindrical thin-wall crushing buffer mechanism. It is found that both the cylindrical thin-walled tube and the spring have obvious optimization effects on the collision, but the rebound of the cylindrical thin-walled tube scheme is smaller after the collision. The wall thickness of cylindrical thin-walled cylinder has a great influence on the maximum stress and graphite layer stress of the rod, but has a relatively small influence on the rebound of the rod, and there is an optimal optimization scheme.
Further Investigation of Neutron Noise Under the Condition of Fuel Failure Based on Frequency Domain Finite Element Method
Authors: Yuan Baoxin , Lv Huiyi , Zeng Herong , Zheng Jie , Chen Zihan , Huang Huan , Zhang Songbao , Qian Dazhi
Published: November 2024

Usually, some fuel elements are allowed to be damaged under normal operating conditions of the reactor. At present, the design index of fuel element damage rate of pressurized water reactor at home and abroad is 0.25%. In view of fuel element damage accidents, there are two measurement methods for operating units: fuel accident monitoring and primary loop dose monitoring. Fuel accident monitoring depends on the measurement of delayed neutron activity flowing out of the core to determine whether there is fuel damage, and primary loop dose monitoring depends on measuring the activity of fission products and the concentration of inert gas flowing into the primary coolant to determine whether there is fuel damage. It takes a long time for the two measurement methods to discharge the measured fluid from the core outlet to the measuring device, and the limited damage event is also perplexed by the lower limit of dosimeter measurement after being widely diluted by the total flow of the first loop. For the plate fuel core, the axial flow of the delayed neutron precursor after the fuel element is damaged will break the inherent balance of the normal core and cause the transient change of neutron noise. Based on this idea, on the basis of the work of the author’s team reported by ICONE30, this work assumes three different degrees of plate fuel assembly damage to the assembly position of the core, corresponding to three axial flow scenarios of delayed neutron precursor. Based on the frequency domain finite element method, the neutron dynamics calculations are carried out for the above scenarios, and the fast group and thermal group neutron noise responses of neutron detectors at four different positions in the core are obtained.
Safety Function Based HPR1000 Accident Mitigation Strategy Development for SGTR
Authors: Yang Benlin , Wang Jiansheng , Zhang Yating , Xiong Zhenpeng , Zhao Guanghui , Zheng Junming , Gong Yihong
Published: November 2024

Based on the safety function design of HPR1000, a systematic and structurized process has been provided to show how SGTR accident mitigation strategies are developed. The evolution of SGTR accident progress and variation of main physical parameters are used for the analysis of HPR1000 safety functions which are needed to be performed in the accident, and all safety features performing the corresponding safety functions are then identified for accident mitigation to reach a controlled state or safe sate. All safety features represent the system configuration of HPR1000 safety design, and are the key elements for the development of HPR1000 accident mitigation strategy. According to the operation mode of HPR1000, considering accident progression and logic of the actuation of safety features, the SGTR accident mitigation strategy can be made comprehensively and systematically.
Evaluation of Expansion Reactivity Based on Reactivity Coefficient for Sodium-Cooled Fast Reactor
Authors: Takeda Satoshi , Kitada Takanori , Hoashi Eiji , Okita Takafumi
Published: November 2024

In this paper, formulas for evaluating expansion reactivity based on reactivity coefficients in sodium-cooled fast reactors are derived, and the approximation errors used in the derivation are also evaluated. This research provides formulas for both Z-axis expansion reactivity and radial expansion reactivity. These reactivities are separated into the effect of change in geometric shape and that of change in the cross-section. Since the major approximation in the present derivation is the separation of effects due to geometric shape changes and cross-sectional area changes, the approximation error due to this separation was evaluated using results of neutron transport calculations for fast reactor. This evaluation was performed for two geometries with different ratios of the reactor core’s height to diameter. The results show that the approximation error is less than 20 pcm. Therefore, it can be expected that expansion reactivity can be accurately evaluated using reactivity coefficients.
Hydrogen Absorption Behavior of the R-SUS304ULC/Ta/Zr Dissimilar Metal Joint Under NaOH Immersion
Authors: Ishijima Yasuhiro , Ueno Fumiyoshi , Abe Hitoshi , Igarashi Takahiro
Published: November 2024

In reprocessing plants of Japan, Zr and ultra-low carbon 304 stainless steel (R-SUS304ULC) piping are connected by a joint formed by explosive bonding with Ta sandwiched between R-SUS304ULC and Zr. The joint exhibits excellent corrosion resistance during normal operation. However, Ta causes corrosion and generates hydrogen in NaOH solutions, which are used to decontaminate the equipment in reprocessing plants. This has led to concerns about hydrogen embrittlement of the joints via hydrogen absorption. The authors examined the hydrogen absorption behavior of pure Ta immersed in various NaOH solutions. However, there is a lack of studies on the hydrogen absorption behavior of such joints, and it is difficult to evaluate the amount of hydrogen absorbed by the joints under various decontamination conditions. In this study, we conducted immersion tests of the R-SUS304ULC/Ta/Zr joint in NaOH solution to investigate the effect of immersion environment on hydrogen absorption behavior. Electrochemical measurements were conducted to examine the hydrogen absorption environment. The results showed that the amount of hydrogen absorbed into Ta in the joints decreased compared with that in pure Ta, regardless of the immersion time. The galvanic current measurements of Ta connected R-SUS304ULC or Zr in an NaOH solution indicated that the hydrogen evolution reaction was separated to the R-SUS304ULC and Zr surfaces and that the hydrogen absorption of Ta was suppressed.
Research on the Re-Entrainment Mechanism in Corrugated Plate Driers in the Nuclear Field
Authors: Wang Bo , Li Ru , Li Jiangkuan , Tan Sichao , Tian Ruifeng
Published: November 2024

The corrugated plate dryer is an important steam-water separation equipment in the secondary loop of the mainstream third-generation nuclear power plant in the field of nuclear engineering. The important parameter indicator of the corrugated plate dryer is its separation efficiency. The Re-entrainment phenomenon is a key issue that prevents further improvement of the separation efficiency of the corrugated plate. Its connotation is the phenomenon of secondary liquid droplets being carried by the airflow, leading to a decrease in the efficiency of steam water separation. Starting from the mechanism of Re-entrainment, this article analyzes the fluctuation of the liquid film inside the corrugated plate, the occurrence process of liquid film rupture, and the location and size of secondary liquid droplets generated by liquid film rupture. Based on the establishment of a two-dimensional curve coordinate system at the corner position of the corrugated plate, the force analysis of a thin liquid film with a width of dr and a curvature radius of r in the radial and axial directions is also conducted. Define dimensionless parameters to obtain the order of each item in the liquid film control equation, and then ignore the higher order, ultimately obtaining the liquid film rupture model. Based on the above liquid film rupture model, high-precision three-dimensional calculation of the waveform plate was achieved, thereby achieving accurate calculation of the position of secondary droplet generation. The results indicate that there are obvious nonlinear characteristics in the location and size of the liquid film rupture inside the corrugated plate. The size of secondary droplets is mostly in the millimeter range. The above model provides important technical support for the elimination of Re-entrainment phenomenon and provides important reference for the design of corrugated plate dryers in nuclear power plants and nuclear power plants.