Computer Code Research Articles

Thermal Hydraulic Analysis of Turbulent Flow of Superheated Steam Through Multiple Configurations of 3D Angular Piping Bend in Power Plant Installations

Abstract One of the most vulnerable parts in high-pressure and temperature pipeline networks in steam turbine power plant installations is pipe bends, due to intense fluctuation of velocity and pressure of the superheated steam flowing through the piping bend. On the other hand, because of unique chemical and physical properties, the transportation of superheated steam can adversely effect on the integrity of the pipe bends in the piping network. Therefore, the potential risk of pipeline failure becomes more probable at bends. Therefore, to ensure the survivability of the piping network, thorough investigations of the superheated steam flowing through pipe bends are of great significance in better understanding its flow behavior. However, to predict flow behavior at piping bend, intensive research by direct experiment at high temperature and pressure might not be possible to some extent. In that case, computer codes and models can help us analyze flow behavior of superheated steam at pipe bends. The current work is a computational fluid dynamics investigation, where numerical examination is carried out by commercial code ansys fluent for thermal hydraulic analysis of flow behavior of superheated steam through multiple configurations of 3D angular piping bend: 90 deg, 120 deg, and 135 deg. Validation of credibility of the computational approach is done against Sudo et al.'s experiment. With relatively good agreement between the experiment and numerical result using air flowing through 90 deg elbow, single-phase turbulent flow of superheated steam is examined by the application of realizable turbulence model (k–ɛ). The final assessment of the computed results has been done using qualitative and quantitative analyses. The study reveals that unlike the pressure profiles, the radial velocity profiles at the bend exit are noticeably different from those at the bend inlet, since they exhibit more rounded peaks and gentler velocity gradients. The study also shows that the radial pressure and velocity profiles do not display any sign of the existence of a pair of vortices.

Supersymmetry with scalar sequestering

Supersymmetric models with a strongly interacting superconformal hidden sector (HS) may drive soft supersymmetry (SUSY) breaking scalar masses, bilinear soft term Bμ and Higgs combinations mHu,d2+μ2 to small values at some intermediate scale, leading to unique sparticle mass spectra along with possibly diminished fine-tuning in spite of a large superpotential μ parameter. We set up a computer code to calculate such spectra, which are then susceptible to a variety of constraints: (1) possible charge-or-color breaking (CCB) minima in the scalar potential, (2) unbounded from below (UFB) scalar potential, (3) improper electroweak symmetry breaking, (4) a charged or sneutrino lightest SUSY particle (LSP), (5) generating mh∼125 GeV, (6) consistency with LHC sparticle mass limits, and (7) naturalness. We find this bevy of constraints leaves little or no viable parameter space for the case where hidden sector dynamics dominates minimal supersymmetric standard model (MSSM) running, even for the case of nonuniversal gaugino masses. For the case with moderate HS running with comparable MSSM running, and with universal gaugino masses, then the fine-tuning is ameliorated, but nonetheless remains high. Viable spectra with moderate HS running and with low fine-tuning and large μ can be found for nonuniversal gaugino masses. Published by the American Physical Society 2024

Transient evolution of thermal stratification and passive flow guidance inside a heat exchanger immersed thermal energy storage tank

Thermal stratification is being studied globally for thermal storage tanks while natural convection motion has a high impact on the phenomenon. Therefore, in this work, a conical guide geometry is introduced as a passive flow modifier to enhance the thermal stratification inside a cylindrical tank that is used for thermal storage purposes. The tank also has an immersed spiral coil heat exchanger in it. Transient evolution of thermal stratification inside the thermal storage tank is monitored for different charge flowrates and temperatures. The experimental data is used to benchmark a commercial computational fluid dynamics code relying on finite volume method. After seeing that the code simulates the transient thermal stratification with acceptable discrepancies, a conical guide geometry above the immersed heat exchanger is examined via the computational code for dimensional variations. The dimensions of the cone guide are defined based on thermal storage tank dimensions in order to have some degree of universality. The best performing cone guide in the simulations is then tested experimentally. It is validated that the proposed cone guidance enhanced thermal stratification evolution in the tank. An increase of 3.85 °C is obtained in the average tank temperature with the use of the cone guide after 3 h of charging. Approximate effectiveness of the heat exchanger coil is found about 90 % while a 7.6 % increase is realized by the utilization of the guide.

Exergy analysis under consideration of operational parameters by numerical approach in a two-stroke marine diesel engine

This paper presents a numerical approach of the influence of operational parameters on the exergy terms in a two-stroke marine diesel engine. Operational parameters are introduced as different start of injection (-4, -2, 0 and 2 °CA) and scavenge air inlet temperature (300, 312, 330 and 340 K) values. The energy analysis is conducted within a closed cycle by using a three-dimensional computational fluid dynamics code. The simulation results are compared with the corresponding experimental pressure data in the literature and show good agreement. Also, the exergy analysis is performed by a developed in-house computational code. Various exergy rates and cumulative exergies are detected and computed separately at operational parameters. The study reveals that varying the start of injection timing from −4 to 2 °CA at full load condition results in a decrease in exergy efficiency from 43.45 % to 41.36 %. Furthermore, an increase in scavenge air inlet temperature from 300 K to 340 K leads to a reduction in exergy efficiency from 42.83 % to 41.44 %. These findings underscore the critical influence of injection timing and scavenge air temperature on the exergy performance. In light of these results, this paper gains more insight into the impact of design parameters of a two-stroke marine diesel engine on exergy efficiency and presents a preliminary data for marine diesel engine manufacturers in the design of a two-stroke marine diesel engine that uses energy efficiently.

Online practical education and training in nuclear engineering: A methodological framework

The education of students in the field of nuclear engineering must combine theoretical and practical teaching, this is the only way to produce quality graduates. Practical education generally includes two areas — experimental teaching and the use of advanced computational codes for the simulation of physical phenomena. The availability of practical education is not a matter of course for all students. The transfer of practical teaching to an online environment opens up a lot of possibilities even for universities that do not have a nuclear reactor, laboratories or extensive computing infrastructure at their disposal.The article deals with key aspects that must be respected when implementing online practical education and training. The listed tips and recommendations are based on the experience gained during the COVID pandemic and during the solution of the PADINE-TT project, which was a response to the development of online teaching and its inclusion in teaching at individual universities.

АНАЛІЗ НАСЛІДКІВ ЕКСТРЕМАЛЬНИХ СИТУАЦІЙ НА БАЗІ ЧИСЕЛЬНИХ МОДЕЛЕЙ

The report considers some classes of numerical models that were built to predict the consequences of emergencies at industrial enterprises. The first class of models has been developed to predict chemical air pollution in case of accidental emissions of toxic substances. Modeling is carried out on the basis of the fundamental equations of aerodynamics and mass transfer. Difference splitting schemes are used for the numerical solution of the modeling equations. The second class of CFD models is designed to assess the risk of thermal damage to people in the event of thermal pollution of the air environment. The third class of models was developed to assess the risk of injury to people when a shock wave moves. To solve this problem Euler equations were used. Computer codes were developed on the base of proposed numerical models.

JSI TRIGA fuel rod reactivity worth experiments for validation of Serpent-2 and RAPID fuel burnup calculations

Reactivity worth of fuel rods at the JSI TRIGA research reactor was measured. Differently burned fuel rods were chosen to validate fuel burnup calculations. Two methods of measuring reactivity worth of fuel rods are used, traditional method is compared to newly introduced method using fuel rods swapping. Connection between both methods is described theoretically and the theory is validated experimentally. Fuel rod worth calculated using the newly introduced fuel rod swap method was within 1σ of worth measured using the traditional method. In addition to the recently performed experiments, weekly measurements of reactor core reactivity throughout the operational history are used for validation. The measured data were used to validate the fuel burnup and core criticality calculations. Fuel burnup calculations are performed using three different computer codes: the deterministic TRIGLAV, the Monte Carlo Serpent-2, and the hybrid RAPID. Great agreement was observed for Serpent-2 and RAPID by simulating fuel rod worth and its burnup, indicating that the fuel burnup and criticality calculations are accurate and that reactivity changes due to small burnup differences on the order of 10 pcm can be accurately simulated. In addition it was shown using ex-core detectors and large fission chamber that detector response changes due to fuel swapping are evident for fuel rod burnup differences of 20 MWd/kg. Fuel burnup calculations were further validated on excess reactivity measurements for three mixed TRIGA cores. The calculated burnup reactivity coefficient ΔρBU using Serpent-2 and RAPID was within 1σ of the measurements, showing both codes are capable of calculating burnup for different TRIGA fuel types.

Computational Thinking During a Short, Authentic, Interdisciplinary STEM Experience for Elementary Students

AbstractSTEM experiences that capture students’ curiosity have a unique role in inspiring awe in science, enculturing science engagement, and recruiting students to pursue STEM careers. Here, we present a unique interdisciplinary STEM experience for elementary school students that teaches them to write computer code to test primate intelligence at a zoo where they test their code with real monkeys. In a pilot study involving 3rd to 6th grade students, we find that students can acquire “hard skills” in computational thinking during this short-term immersive STEM experience, with a significant increase in accuracy and problem-solving attempts at post-test. Furthermore, students’ interests in animal science, computers, and robots remain stable or even increase following this experience, demonstrating the project’s capacity to blend technical skills with authentic scientific exploration. Teachers’ feedback highlights the positive impact on critical thinking and leadership. This research underscores the potential of free-form, authentic, interdisciplinary STEM experiences to simultaneously nurture computational skills and a passion for science.

Hydrogen refueling stations powered by hybrid PV/wind renewable energy systems: Techno-socio-economic assessment

Hydrogen is considered as an attractive alternative to fossil fuels in the transportation sector. However, the penetration of Fuel Cell Electric Vehicles (FCEV) is hindered by the lack of hydrogen refueling station infrastructures. In this study, the feasibility of a hybrid PV/wind system for hydrogen refueling station is investigated. Refueling events data is collected in different locations including industrial, residential, highway, and tourist areas. Station Occupancy Fractions (SOF) and Social-to-Solar Fraction (STSF) indicators are developed to assess the level of synchronization between the hydrogen demand and solar potential. Then, a validated computer code is used to optimize the renewable system components for off/on-grid cases based on minimizing the Net Present Cost (NPC) and the Loss of Hydrogen Supply Probability (LHSP). For off grid cases, the results show that STSF attains maximum value in the industrial area where 0.62 fraction of refueling events occur during the sunshine hours and minimum NPC is achieved. It is observed that when STSF attains lower values of 0.52, 0.41 and 0.38 for residential, highway, and tourist areas, NPC increases by 8, 16 and 31%, respectively. This is associated with lower level of coordination between the hydrogen demand and solar potential. The same conclusion can be stated for the on-grid cases. Therefore, for green hydrogen production via solar energy utilization, it is recommended that a tariff should be applied to encourage refueling hydrogen vehicles during the availability of solar radiation while reducing the environmental impact, storage requirements, and eventually the cost of hydrogen production.

Design and evaluation of a kind of polymer-bonded explosives with improved mechanical sensitivity and thermal properties

The emergence of TKX-50, an energetic ionic salt with a high enthalpy of formation and low sensitivity, has opened a new path for the development of high-energetic, insensitive composite explosives. However, due to the poor interfacial binding properties of TKX-50 with conventional binders, there is a lack of effective guidance for the design of TKX-50 based composite explosives. To address the above issues, the interactions between carboxymethyl cellulose acetate butyrate (CMCAB) and other binders with explosives TKX-50/HMX were compared using the molecular dynamics method. Based on the simulations, TKX-50/HMX/CMCAB-based polymer-bonded explosives (PBXs) were prepared with CMCAB as binder, which displays a high binding energy (Ebind) with TKX-50 and high cohesive energy density (CED), and the effect of TKX-50 content on the performance of PBXs was investigated. The physical properties of PBXs, specifically the morphology, mechanical sensitivity, and thermal conductivity, were analyzed by SEM, sensitivity apparatus, and thermal conductivity meter, respectively. The specific heat capacity (Cp) and non-isothermal decomposition temperature of PBXs were tested by DSC, and then the corresponding thermal kinetic parameters were analyzed to evaluate their thermal safety. The adiabatic thermal decomposition processes of PBXs were tested using an ARC instrument. The decomposition mechanism and kinetics were also explored to further analyze their thermal stability and thermal safety under adiabatic conditions. The computer code EXPLO5 was used to predict the detonation parameters of PBXs. The results showed that CMCAB and TKX-50 displayed favorable interfacial bonding properties, and TKX-50 can be bonded with HMX to form a molding powder with a desirable morphology and safety profile. The TKX-50 in PBXs effectively improves the mechanical sensitivity and thermal safety of PBX and has a significant effect on the detonation performance of PBX. This research demonstrates a novel method suitable for screening and investigating high-energetic insensitive explosive systems compatible with TKX-50.

The convergence approach may be critical to improving early situational awareness in hostile radioactive environments

This study explores the impact of a simulated radiological dispersal device (RDD) event in an urban area on young adults around 20 years old. The RDD releases radioactive Cs-137 (7.0E+3 Ci), a common industrial sterilization source. The study aims to demonstrate that combining computational codes and epidemiological models can produce valuable data to guide initial actions when confronting a hostile radioactive environment. The HotSpot Health Physics and RESRAD-RDD codes were used in the simulation to evaluate the event's initial phase. The codes were executed together, and the HotSpot output data was input into RESRAD-RDD. Based on simulated radiation dose levels, estimated doses were incorporated into radioepidemiological models proposed by the Committee on Biological Effects of Ionizing Radiation (BEIR V or VII report). Despite limitations, data transfer between the models revealed no discontinuities or antagonisms. Radiation doses were simulated under three exposure conditions and two atmospheric release modes (day or night), suggesting that atmospheric conditions, sex, and exposure routine can strongly influence the perception of radiation impacts. This combination of methods can increase situational awareness and help with decision-making and developing coping strategies.

Development of an Electronic Actuating Control Mechanism to Operate a Remotely Controlled 2-Wheel Rice Transplanter

Mechanical transplanters are adopted to reduce human drudgery in manual transplanting. Different types of manual and self-propelled paddy transplanters are commercially available. The human involvement is higher for operating a 2-wheel paddy transplanter operator has to walk 10-22 km behind the machine in a day in puddled field conditions under high temperature (38-440 C) and humid conditions (70-80% RH) in summer. Besides that, the operator has to walk within the 30 cm row width, which causes chafing between the thighs of an operator. To reduce the physical and physiological workload of an operator, an integrated control lever actuating mechanism with gear motors was developed to operate a 2-wheel paddy transplanter remotely. The inductive proximity sensors (SN04-N distance detector) were used to control the crank rotation position of the gear motors, motor drives (BTS 7960), and microcontroller (STM32F4) was used to connect with the auto-driver kit to control the motor mechanism and sensors. The auto-driver kit consisted of a variety of accessories, a physical programmable circuit board, and software, that runs on a PC, used to write and upload computer code as a simplified version of C++ to the physical board. Although the initial cost of the machine with the developed system has been increased up to 28%, but at the same time the effective field capacity has been increased from 0.158 ± 0.02 ha h-1 to 0.175 ± 0.04, resulting the area covered per day and per year has also increased up to 11%. With the development of remotely controlled system, the labor requirement has been reduced from 20± 1 to 13± 1 man h ha-1, which results reduction up to 40%. Moreover, the human fatigue in terms of physical and physiological work load involved while walking behind the transplanter has been eliminated at much extent. As compared to the existing walk-behind type paddy transplanter, the net profit with the developed system rise up to 18.50 to 26.61 % per year and a boost of 34.10 to 51.63% in benefit-cost ratio. Field evaluation of a developed remote-controlled system for a two-wheel rice transplanter would be viable, reducing fatigue among machine operators/farm workers while increasing work productivity and safety.

FP-LAPW study of structural, magnetic, electronic, elastic, and thermoelectric properties of CoCrS Half-Heusler compound

The present article has utilized the WIEN2k computational code to examine the structural, elastic, electronic, magnetic, thermoelectric, and dynamic aspects of the CoCrS Half-Heusler (HH) compound. In this work, calculations have been performed by utilizing the full-potential linearized augmented plane wave method using density functional theory. The electronic bandgap was better interpreted by using the modified Becke–Johnson exchange–correlation functional. We evaluated various electronic properties of the CoCrS HH compound, including band structure plots and density of states. Furthermore, we examined the magnetic characteristics through the computation of magnetic moments and the examination of the spin-polarized electronic state behavior. We also determined the elastic properties of the CoCrS HH compound. These properties, which include stiffness, resilience, and general stability, provide important information about how the material responds to mechanical deformation. Moreover, we explored the electronic structure and found that type 5 of CoCrS exhibits a metallic behavior. In addition, we examined the compound’s thermoelectric properties. Finally, the dynamical properties indicate that type 5 of CoCrS is dynamically stable.

CYBER TECHNOLOGIES IN MODERN INTERNATIONAL CONFLICTS AND METHODS OF ENSURING CYBERSECURITY

The article examines the problems of cybersecurity of the state. As you know, the number and scale of international conflicts have increased recently. The methods of conducting armed conflicts have also changed. More and more people began to move from conventional military clashes to information wars and cyber wars. Over time, technological progress has led to the emergence of new arenas for conflicts between countries and factions. Cyberwar has become one of these arenas, where the main weapons are not missiles and submachine guns, but computer codes and supercomputers. This article reveals the role of cyber technologies in modern international conflicts and presents what threats and opportunities they provide on the battlefield.

스마트 콘트랙트의 금융법적 문제와 규제 수단에 대한 검토

Recent interest rate rises and economic unrest have caused a significant contraction in the decentralized financial industry. The large-scale decline compared to the traditional institutionalized financial industry shows that the right level of financial regulation can help to revitalize the market. As such, the need for regulation in the decentralized financial industry is increasingly recognized, but the discussion is limited to the characteristics of the underlying virtual assets, and there is a lack of discussion on the technologies that form the basis of the decentralized financial industry, such as smart contract.
 There is much debate about the definition of a smart contract, but basically, a smart contract can be defined as computer code, implemented on blockchain technology, that, upon the occurrence of a specified condition or conditions, is capable of running automatically according to pre-specified functions. The origin of smart contract technology does not necessarily require blockchain technology, but the current usage and practical implementation of the term usually involves blockchain technology. These smart contracts are associated with various legal issues due to the important characteristics of (1) anonymity, (2) inconsistency between intent and code content(Similar to the issue “der Unstimmigkeiten von Willen und Erklärung”), (3) circumvention, and (4) decentralized autonomous organization.
 The existing regulatory discourse is excellent at achieving its objectives, but it has limitations in terms of (1) specificity and (2) voluntariness. A new regulatory approach needs to consider the specific characteristics of smart contract, the main transaction method of Decentralized finance, while encouraging voluntary responses from individuals. The Smart Contract Self-Review Board, Private Key Custodian Organization, and Entrusted Certification System are solutions based on these requirements, but it is difficult to judge that they completely solve the legal problems of smart contracts, and further discussion is needed on a regulatory method with an incentive structure that can attract voluntarism.

Algorithms and Faith: The Meaning, Power, and Causality of Algorithms in Catholic Online Discourse

The purpose of this article is to present grassroots concepts and ideas about “the algorithm” in the religious context. The power and causality of algorithms are based on lines of computer code, making a society influenced by “black boxes” or “enigmatic technologies” (as they are incomprehensible to most people). On the other hand, the power of algorithms lies in the meanings that we attribute to them. The extent of the power, agency, and control that algorithms have over us depends on how much power, agency, and control we are willing to give to algorithms and artificial intelligence, which involves building the idea of their omnipotence. The key question is about the meanings and the ideas about algorithms that are circulating in society. This paper is focused on the analysis of “vernacular/folk” theories on algorithms, reconstructed based on posts made by the users of Polish Catholic forums. The qualitative analysis of online discourse makes it possible to point out several themes, i.e., according to the linguistic concept, “algorithm” is the source domain used in explanations of religious issues (God as the creator of the algorithm, the soul as the algorithm); algorithms and the effects of their work are combined with the individualization and personalization of religion; algorithms are perceived as ideological machines.

Investigating the impact of Trombe wall parameters on thermal performance and room temperature in the Iraqi climate

AbstractTrombe wall serves as an effective passive heating element, and its performance is heavily reliant on local climate conditions. This study involved both experimental and numerical analyses of a full‐scale test room equipped with a Trombe wall under Iraqi climate conditions. To facilitate this investigation, an experimental test room was constructed in Kirkuk city with dimensions of 4.0 m × 3.0 m × 2.75 m. In addition, a numerical simulation method based on computational fluid dynamics was developed and a computer code was created to investigate the performance of the system. The accuracy of the developed numerical approach was validated against experimental data collected from the test room. This analysis was conducted specifically for the period of February 17–18, which represents the coldest month of winter in the study area. The performance of the system was assessed with respect to various parameters; air gap width variations (2, 4, 6, and 10 cm), massive wall thickness ranging from 15 to 35 cm with 5 cm increments, channel width options (3, 5, 10, 15, and 20 cm), and vent heights ranging from 5 to 20 cm in 5 cm increments. Furthermore, an investigation of the impact of replacing the air in the air gap with inert gases, specifically argon, krypton, and a mixture of these gases with air was conducted, as well. The outcomes indicate that both the channel width and vent height do not have a significant impact on the system's performance. However, the width of the air gap has a modest effect on system performance, and the best performance was observed with a smaller gap width, specifically 2 cm. The most significant impact on room temperature is observed when the storage wall thickness is varied. In the case of wall thickness of 15 cm, there is a notably higher fluctuation in room temperature between the maximum and minimum values, reaching approximately 16°C. For a wall thickness of 35 cm, however, this fluctuation is significantly reduced to about 3°C. The system efficiency as determined after 24 h of operation period improved significantly when the air was replaced by an inert gases or a mixture of gases in the air gap. Compared to air, the increase in efficiency is about 14.8% for argon, 17.7% for krypton, and 20.6% for the mixture of gases.

A general-purpose code for correlated sampling using batch statistics with MCNP6 for fixed-source problems

Background Correlated sampling can be applied with batch statistics using MCNP6’s tally fluctuation chart (TFC) to reduce the uncertainty of a difference of tallies between a base case and a perturbed case without modifying the source code. The cases are correlated if they are run with the same random number sequence. Equations implemented Equations used to apply correlated sampling to the difference of two tallies are summarized from previous work. Equations used to apply correlated sampling to a ratio of two tallies, to the difference of two tallies divided by a third tally, and to other combinations of ratios are presented. New computer code A general-purpose, command-line-driven computer program, COSUBS (Correlated Sampling Using Batch Statistics), is presented that reads MCNP6 TFCs from output files and applies these equations. The user specifies the input relative perturbation, if desired, and any normalization tally, if desired. Example problems show how to run COSUBS and interpret the output.

Enhancing blast mitigation in tunnels with expansion chamber subjected to high explosives detonations for protecting underground facilities

This paper presents a numerical investigation into the effect of expansion chamber in mitigating overpressures and impulses in protective tunnels subjected to detonation of high explosives. Blast shockwave propagation in a protective tunnel, with dimensions of 160 m in length, 8.9 m in width and 7.2 m in height, was simulated using a computational fluid dynamics code, Viper::Blast. The design parameters of the expansion chamber cover a broad spectrum chamber lengths between 6.1 and 12.1 m, widths spanning from 10.7 to 97 m, length-to-width ratios from 0.0 (indicating no chamber) to 5.0, heights of 8.0 and 14.9 m, and chamber-to-tunnel width ratios in the range of 1.2 to 10.9 m. Two charge weights of 1000 and 2000 kg of TNT were employed to assess their influences. To ensure the reliability of the CFD model, mesh sensitivity analysis, overpressure stability assessments, and validation studies were undertaken. A parametric analysis was then conducted using the validated model to derive an optimal design for the expansion chamber within the specified tunnel. Recommendations for incorporating an expansion chamber into protective tunnels under blast events are provided.

Numerical simulation of fluid dynamics and mixing in headers of sodium-air heat exchangers

The paper presents the results of a numerical simulation for sodium fluid dynamics and mixing in the tubing system of an air-cooled heat exchanger (AHX), which is a part of the emergency cooldown system (ECS) of sodium fast reactors (SFRs). Non-uniform sodium flows in the AHX tubing system may lead to the mixing of different-temperature sodium flows, temperature fluctuations and tube breaks. It was found in the course of investigating accidents involving breaks in the PFR and Phénix reactor AHX tubing systems that the failure was caused by the metal temperature fluctuations (Cruickshank and Judd 2005). The numerical simulation used three- and one-dimensional computer codes. It has been found that the calculations of the AHX sodium flow rate distribution with a practically acceptable accuracy can be performed using a one-dimensional code. The factors that influence the non-uniform distribution of sodium flows in the AHX tubing system have been analyzed. Calculations have been performed for the AHX sodium flow distributions and for the mixing of different-temperature sodium flows in the AHX outlet header. The results are presented from calculating the amplitude of sodium fluctuations near the AHX header walls. The effect from shutting down several modules on the non-uniform flow distribution and temperature fluctuations in the AHX has been investigated. Approximations of numerical solutions have been obtained for the sodium flow distribution as a function of the number of the modules shut down.