Control system design for a pressure-tube-type supercritical water-cooled nuclear reactor via a higher order sliding mode method

Nuclear power plants exhibit non-linear and time-variable dynamics.Therefore,designing a control system that sets the reactor power and forces it to follow the desired load is complicated.A supercritical water reactor(SCWR)is a fourth-generation conceptual reactor.In an SCWR,the non-linear dynamics of the reactor require a controller capable of control-ling the nonlinearities.In this study,a pressure-tube-type SCWR was controlled during reactor power maneuvering with a higher order sliding mode,and the reactor outgoing steam temperature and pressure were controlled simultaneously.In an SCWR,the temperature,pressure,and power must be maintained at a setpoint(desired value)during power maneuvering.Reactor point kinetics equations with three groups of delayed neutrons were used in the simulation.Higher-order and classic sliding mode controllers were separately manufactured to control the plant and were compared with the PI controllers speci-fied in previous studies.The controlled parameters were reactor power,steam temperature,and pressure.Notably,for these parameters,the PI controller had certain instabilities in the presence of disturbances.The classic sliding mode controller had a higher accuracy and stability;however its main drawback was the chattering phenomenon.HOSMC was highly accurate and stable and had a small computational cost.In reality,it followed the desired values without oscillations and chattering.

Artificial Intelligence Driven Nuclear Power Reactors(A Technical Memorandum)

The 21st Century era and new modern technologies surrounding us day-in and day-out have opened a new door to“Pandora Box”,that we do know it as AI(artificial intelligence)and its two essential integrated components namely ML(machine learning)and DL(deep learning).However,the strive and progress in AI,ML,and DL pretty much has taken over any industry that we can think of,when it comes to dealing with cloud of structured data in form of BD(big data).A NPP(nuclear power plant)has multiple complicated dynamic system-of-components that have nonlinear behaviors.For controlling the plant operation under both normal and abnormal conditions,the different systems in NPPs(e.g.,the reactor core components,primary and secondary coolant systems)are usually monitored continuously,which leads to very huge amounts of data.Of course Nuclear Power Industry in form of GEN-IV(Generation IV)has not been left behind in this 21st century era by moving out of GEN-III(Generation III)to more modulars form of GEN-IV,known as SMRs(small modular reactors),with a lot of electronic gadgets and electronics that read data and information from it to support safety of these reactor,while in operation with a built in PRA(probabilistic risk assessment),which requires augmentation of AI in them to enhance performance of human operators that are engaged with day-to-day smooth operation of these reactors to make them safe and safer as well as resilience against any natural or man-made disasters by obtaining information through ML from DL that is collecting massive stream of data coming via omni-direction.Integration of AI with HI(human intelligence)is not separable,when it comes to operation of these smart SMRs with state of the art and smart control rooms with human in them as actors.This TM(technical memorandum)is describing the necessity of AI playing with nuclear reactor power plant of GEN-IV being in operation within near term sooner than later,when specially we are facing today’s cyber-attacks with their smart malware agents at work.

Studies on Production Planning of Dispersion Type U3Si2-Al Fuel in Plate-Type Fuel Elements for Nuclear Research Reactors

Several fuel plants that supply nuclear research reactors need to increase their production capacity in order to meet the growing demand for this kind of nuclear fuel. After the enlargement of the production capacity of such plants, there will be the need of managing the new production level. That level is usually the industrial one, which poses challenges to the managerial staff. Such challenges come from the fact that several of those plants operate today on a laboratorial basis and do not carry inventory. The change to the industrial production pace asks for new actions regarding planning and control. The production process based on the hydrolysis of UF6 is not a frequent production route for nuclear fuel. Production planning and control of the industrial level of fuel production on that production route is a new field of studies. The approach of the paper consists in the creation of a mathematical linear model for minimization of costs. We also carried out a sensitivity analysis of the model. The results help in minimizing costs in different production schemes and show the need of inventory. The mathematical model is dynamic, so that it issues better results if performed monthly. The management team will therefore have a clearer view of the costs and of the new, necessary production and inventory levels.

Prospects of Technological Improvement of Nuclear and Environmental Safety of World Energy

Today, the most urgent problem of the existing and future nuclear power industry is to ensure the nuclear and environmental safety of the operation of nuclear power reactor units (NPPs) and nuclear power plants (NPPs). It is solved thanks to the application of deeply echeloned protection and an anti-accident complex of methods and means for effective control of the operation of active reactor zones (AZR). However, the danger of existing NPPs in the world from time to time manifests itself in the form of severe post-project accidents and catastrophes with the release into the environment of a significant amount of radioactive materials dangerous for all living things. The results of the analysis show that the unconditional fulfillment of the main requirements of nuclear environmental safety and biocompatibility is possible only in the so-called wave nuclear reactor of the G-V generation, which, unlike reactors of the previous generations III, II+ and IV, does not require supercritical loading of the core with nuclear fuel. In the active zone of this reactor, nuclear-physical processes governed by physical law are implemented, which exclude the operator’s participation in regulating the reactivity of the reactor’s active zone, which makes it the reactor with the highest level of nuclear and environmental safety today, which is based on the principles of so-called internal safety, free from the human factor. The possibility of burning nuclear fuel based on U238 and Th232 in it expands the reserves of energetic nuclear fuel almost to inexhaustibility. The technology of nuclear reactors of the G5 generation through the secondary use of spent irradiated nuclear fuel (SNF) for the production of energy and energy raw materials with simultaneous burning of it to an environmentally safe state is able to quickly reduce the available stocks and further production of dangerous SNF, guarantee the nuclear and environmental safety of NPPs with reactors G5 and to technologically make nuclear post-project accidents and disasters impossible at the level of physical law with the complete elimination of the human factor.

Assessment of Axial Power Peaking Factors in GHARR-1 LEU Core: A Decadal Simulation Analysis

This study aims to thoroughly investigate the axial power peaking factors (PPF) within the low-enriched uranium (LEU) core of the Ghana Research Reactor-1 (GHARR-1). This study uses advanced simulation tools, like the MCNPX code for analysing neutron behavior and the PARET/ANL code for understanding power variations, to get a clearer picture of the reactor’s performance. The analysis covers the initial six years of GHARR-1’s operation and includes projections for its whole 60-year lifespan. We closely observed the patterns of both the highest and average PPFs at 21 axial nodes, with measurements taken every ten years. The findings of this study reveal important patterns in power distribution within the core, which are essential for improving the safety regulations and fuel management techniques of the reactor. We provide a meticulous approach, extensive data, and an analysis of the findings, highlighting the significance of continuous monitoring and analysis for proactive management of nuclear reactors. The findings of this study not only enhance our comprehension of nuclear reactor safety but also carry significant ramifications for sustainable energy progress in Ghana and the wider global context. Nuclear engineering is essential in tackling global concerns, such as the demand for clean and dependable energy sources. Research on optimising nuclear reactors, particularly in terms of safety and efficiency, is crucial for the ongoing advancement and acceptance of nuclear energy.

Novel Technological Developments with Impacts on Perspectives for Mobile Nuclear Power Plants

New research developments suggest that nuclear reactors using fusion may enter the market sooner than imagined even for mobile applications, like merchant ship propulsion and remote power generation. This article aims at pointing such developments and how they could affect nuclear fusion. The method is enumerating the main nuclear reactors concepts, identifying new technological or theoretical developments useful to nuclear field, and analysing how new recombination could affect feasibility of nuclear fusion. New technologies or experimental results do not always work the way people imagine, being better or worse for intended effects or even bringing completely unforeseen effects. Results point the following designs could be successful, in descending order of potential: aneutronic nuclear reactions using lattice confinement, aneutronic nuclear reactions using inertial along magnetic confinement, hybrid fission-lattice confinement fusion, and fission reactions.

A novel approach for radionuclide diffusion in the enclosed environment of a marine nuclear reactor during a severe accident

A severe accident in a marine nuclear reactor leads to radionuclide leakage,which causes hidden dangers to workers and has adverse effects of environmental pollution.It is necessary to propose a novel approach to radionuclide diffusion in a confined environment after a severe accident in a marine nuclear reactor.Therefore,this study proposes a new method for the severe accident analysis program MELCOR coupled with computational fluid dynamics scSTREAM to study radioactive diffusion in severe accidents.The radionuclide release fraction and temperature calculated by MELCOR were combined with the scSTREAM calculations to study the radionuclide diffusion behavior and the phenomenon of radionuclide diffusion in different space environments of the reactor under the conditions of varying wind velocities of the ventilation system and diffusion speed.The results show that the wind velocity of the ventilation system is very small or zero,and the turbulent diffusion of radionuclides is not obvious and diffuses slowly in the form of condensation sedimentation and gravity settlement.When the wind speed of the ventilation system increases,the flow of radionuclides meets the wall and forms eddy currents,affecting the time variation of radionuclides diffusing into chamber 2.The wind velocity of the ventilation system and the diffusion speed has opposite effects on the time variation trend of radionuclide diffusion into the four chambers.

Nuclear geyser model of the origin of life:Driving force to promote the synthesis of building blocks of life

We propose the nuclear geyser model to elucidate an optimal site to bear the first life.Our model overcomes the difficulties that previously proposed models have encountered.Nuclear geyser is a geyser driven by a natural nuclear reactor,which was likely common in the Hadean Earth,because of a much higher abundance of 235U as nuclear fuel.The nuclear geyser supplies the following：（1）high-density ionizing radiation to promote chemical chain reactions that even tar can be used for intermediate material to restart chemical reactions,（2）a system to maintain the circulation of material and energy,which includes cyclic environmental conditions（warm/cool,dry/wet,etc.）to enable to produce complex organic compounds,（3）a lower temperature than 100℃ as not to break down macromolecular organic compounds,（4）a locally reductive environment depending on rock types exposed along the geyser wall,and（5）a container to confine and accumulate volatile chemicals.These five factors are the necessary conditions that the birth place of life must satisfy.Only the nuclear geyser can meet all five,in contrast to the previously proposed birth sites,such as tidal flat,submarine hydrothermal vent,and outer space.The nuclear reactor and associated geyser,which maintain the circulations of material and energy with its surrounding environment,are regarded as the nuclear geyser system that enables numerous kinds of chemical reactions to synthesize complex organic compounds,and where the most primitive metabolism could be generated.

Development and Application of Maintenance Template in Pressurized Water Reactor Nuclear Power Plant

Good practices of maintenance optimization in nuclear power field need to be effectively consolidated and inherited,and maintenance optimization can provide technology support to create a long-term reliable and economic operation for nuclear power plants( NPPs) especially for a large number of nuclear powers under construction. Based on the development and application of maintenance template in developed countries,and combining with reliability-centered maintenance( RCM) analysis results and maintenance experience data over the past ten years in domestic NPPs, the development process of maintenance template was presented for Chinese pressurized water reactor( PWR) NPP,and the application of maintenance template to maintenance program development and maintenance optimization combined with cases were demonstrated. A shortcut was provided for improving the efficiency of maintenance optimization in domestic PWR NPP,and help to realize a safe,reliable,and economic operation for domestic NPPs.

Influence of the Impeller/Guide Vane Clearance Ratio on the Performances of a Nuclear Reactor Coolant Pump

An AP1000 nuclear reactor coolant pump is considered to assess the influence of the Impeller/Guide vane clearance on the performances of this type of pumps.Experiments and numerical simulations relying on an unidirectional fluid-solid coupling approach are used to investigate the problem(stress,strain and mode of the rotor).The results reveal the relationship existing between the hydraulic performance of the nuclear reactor coolant pump and the clearance ratio.The effect of clearance ratio on the maximum equivalent stress on the back surface of the impeller blade is greater than that on the working surface(the maximum equivalent stress on the back surface of impeller blade is about three times that on the working surface).The clearance ratio has a scarce effect on the first six natural frequencies of the rotor of the nuclear reactor coolant pump.The related vibrational modes have different waveforms.

Nuclear Energy and Its History: Past Consequences, Present Inadequacies and a Perspective for Success

An attempt is made to locate nuclear technology within a logical context considering history, risks, societal catastrophes and perspectives: the need is identified for a new direction in the exploitation in order to restore the role in energy production. We depict the situation coming from a marvelous history of discoveries started at the beginning of the XX century;heroes are recalled who made possible something that is inconceivable today: design, construction and production of electricity in a few years;that history was tainted by intentional nuclear explosions, i.e. the original sin that we are now paying. Then, we attempt to show that the societal risk is an inherent part of the civilization. Restoring the public trust (towards nuclear fission technology) by matching nuclear safety with the current technological status and advancers in risk assessment is the key objective. The “independent assessment”, or a principle for the exploitation of nuclear energy already stated in the 50’s of the previous century, shall then re-appear. This is used to erect the signpost for a “dynamic barricade” to further reduce the risk of operation of nuclear reactors and to match the design with current technological capabilities and with the frontiers of the research.

Wide Range Neutron Monitoring(WRNM)System in Boiling Water Reactors(A Short Communication&Memorandum)

The WRNM(wide range neutron monitoring)is a newly developed neutron monitoring channel which was initially conceived as a means to meet Regulatory Guide 1.97 requirements for post-accident neutron monitoring.The scope was expanded to include the startup monitoring function with the aim of replacing both the source and IRMs(intermediate range monitors)in BWRs(boiling water reactors).The WRNMs,consisting of a newly designed fixed incore regenerative sensor and new electronics,which include both counting and MSV(mean square voltage)channels,have been tested in several reactors and its capabilities have been confirmed.The channel will cover the neutron flux range from 103 nv to 1.5×103 nv;it has greater than 1 decade overlap between the counting and MSV channels.Because of the regenerative fissile coating the sensor,even though fixed incore,has a life of approximately 6.0 full power years in a 51 kW/L BWR and similar situation has been proposed for newly designed small modular reactor such as BWRX-300 of General Electric Hitachi reactor.

Nanomaterials Driven Magnetic Nuclear Fusion Confinement Approaches(A Technical Memorandum)

Nuclear energy driven magnetic confinement via donut shape device known as Tokamak,a toroidal apparatus,for producing controlled fusion reactions in hot plasma,was originally suggested as a basic yet more promising fusion reactor.Today the more innovative version of this apparatus that is known as an ITER(international thermonuclear experimental reactor)shows a way toward MCF(magnetic confinement fusion)of hot plasma goal by satisfying Lawson’s Criteria to some degree of achievement.However,since this fusion driven reactor of hot plasma needs to operate at almost 150 million Celsius,the internal material of this reactor is a matter of concern for scientists that are involved with its fabrication.Uniqueness of nanomaterials from the point of view of physical and chemical properties is suggested as a possible potential application for this special and innovative reactor for a nuclear fusion device.Convergence of nanotechnology in study of new generation of materials of this kind can shape the path for various technological developments and a large variety of disciplines,including MCF driven plasma of hot fusion as well.This short TM(technical memorandum)written by these two authors will cover this aspect of technology in a holistic way and the more granular level is left to the reader of this TM to investigate further.

Dynamic evaluation of a scaled-down heat pipe-cooled system during start-up/shut-down processes using a hardware-in-the-loop test approach

Micro-mobile heat pipe-cooled nuclear power plants are promising candidates for distributed energy resource power genera-tors and can be flexibly deployed in remote places to meet increasing electric power demands.However,previous steady-state simulations and experiments have deviated significantly from actual micronuclear system operations.Hence,a transient analysis is required for performance optimization and safety assessment.In this study,a hardware-in-the-loop(HIL)approach was used to investigate the dynamic behavior of scaled-down heat pipe-cooled systems.The real-time features of the HIL architecture were interpreted and validated,and an optimal time step of 500 ms was selected for the thermal transient.The power transient was modeled using point kinetic equations,and a scaled-down thermal prototype was set up to avoid mod-eling unpredictable heat transfer behaviors and feeding temperature samples into the main program running on a desktop PC.A series of dynamic test results showed significant power and temperature oscillations during the transient process,owing to the inconsistency of the rapid nuclear reaction rate and large thermal inertia.The proposed HIL approach is stable and effective for further studying of the dynamic characteristics and control optimization of solid-state small nuclear-powered systems at an early prototyping stage.

MATRIX INVESTIGATION ON ISAICHEV ORIENTATION RELATIONSHIP

By means of TEM technique the orientation relationships of cementite, precipitated from islands of granular bainite during tempering, with ferrite have been observed. By calculating the eigenvalues and eigenvectors of transformation matrix, Isaichev relationship has been analyzed. The results indicate that Isaichev relationship is indeed the sum of Kurdjumov-Sachs relationship and Pitsch relationship, so the viewpoint that the cementite with Isaichev relationship precipitates from austenite, instead of ferrite, was confirmed. Moreover, the matrix calculation shows that three reported orientation relationships among austenite, ferrite and cementite in pearlitic transformation cannot be simultaneously valid. (Edited author abstract) 4 Refs.

Nusselt number correlation for turbulent heat transfer of helium-xenon gas mixtures

A gas-cooled nuclear reactor combined with a Brayton cycle shows promise as a technology for highpower space nuclear power systems.Generally,a helium-xenon gas mixture with a molecular weight of14.5-40.0 g/mol is adopted as the working fluid to reduce the mass and volume of the turbomachinery.The Prandtl number for helium-xenon mixtures with this recommended mixing ratio may be as low as 0.2.As the convective heat transfer is closely related to the Prandtl number,different heat transfer correlations are often needed for fluids with various Prandtl numbers.Previous studies have established heat transfer correlations for fluids with medium-high Prandtl numbers(such as air and water)and extremely lowPrandtl fluids(such as liquid metals);however,these correlations cannot be directly recommended for such helium-xenon mixtures without verification.This study initially assessed the applicability of existing Nusselt number correlations,finding that the selected correlations are unsuitable for helium-xenon mixtures.To establish a more general heat transfer correlation,a theoretical derivation was conducted using the turbulent boundary layer theory.Numerical simulations of turbulent heat transfer for helium-xenon mixtures were carried out using Ansys Fluent.Based on simulated results,the parameters in the derived heat transfer correlation are determined.It is found that calculations using the new correlation were in good agreement with the experimental data,verifying its applicability to the turbulent heat transfer for helium-xenon mixtures.The effect of variable gas properties on turbulent heat transfer was also analyzed,and a modified heat transfer correlation with the temperature ratio was established.Based on the working conditions adopted in this study,the numerical error of the property-variable heat transfer correlation was almost within 10%.

Thermal-hydraulic Stability Analysis of Nuclear Heating Reactors

The two-phase flow instability that can occur in a natural circulation system is of importance in the design of nuclear heating reactors. The time domain code RETRAN-02 and the frequency domain code NUFREQ were applied to estimate the instability boundary and the effects of such parameters as pressure, inlet resistance and riser height in NHR-5 and an experimental loop. The results of the calculations and the experiments are in good agreement. Nonlinear density wave oscillations were analyzed using the RETRAN-02 code. The theory of nonequilibrium thermodynamics was used to find an explicit criterion to estimate the threshold of the stability. Experimental simulation of the nuclear feedback density wave instability was also carried out in a test loop using. computer controlled electric power.

Research and Development of Nuclear Heating Reactors in China

The research and development (R & D) of nuclear heating reactors (NHRs) have been conducted as one of the national key projects in science and technology in China since the 1980s. This paper presents the development status. main design featur and safety concepts of the NHR.

Principles of Constructing a Correct Microscopic Theory

In our time, experimental physicists have obtained data on a very large number of phenomena and objects of the physical world. Very rarely there is a situation when theoretical physicists do not have enough experimental data to understand some known fundamental law of Nature. This situation arose almost a hundred years ago and sparked a discussion between A. Einstein and N. Bohr on the probabilistic nature of microcosm phenomena. From the time, it seemed that most physicists are inclined to believe that the proponents of a quantum explanation of the randomness of the phenomena of radioactive decay are right. Now this problem has been solved experimentally. The results of these measurements [1] show that A. Einstein and other proponents of determinism were right. In most cases, theoretical models are based on some already existing experimental data and are intended to explain them. At the same time, in the twentieth century, among microscopic, well-mathematically based models, there were several that raise doubts about their correctness, since they cannot explain a number of other experimental data that can be attributed to the fundamentally important properties of the studied objects [2] [3]. Therefore, the usual criterion for the correctness of the theory, which consists of its agreement with the measurement data, is ambiguous in this case. An additional criterion for the correctness of a microscopic theory can be formulated if it is assumed that the microscopic theory must be quantum one. The coefficients of quantum equations are world constants. Therefore, the solutions of these equations must be equalities made up of world constants only. For this reason, a correct microscopic model must rely on equalities consisting of world constants only. This criterion is shown to work successfully for models of superfluidity and superconductivity, for models of a number of particles, and models of the star interior.

Dimensional Analysis and Similarity Method Driving Self-similar Solutions of the First and Second Kind Inducing Energy

Nearly all scientists,at conjunction with simplifying a differential equation,have probably used dimensional analysis.Dimensional analysis(also called the Factor-Label Method or the Unit Factor Method)is an approach to the problem that uses the fact that one can multiply any number or expression without changing its value.This is a useful technique.However,the reader should take care to understand that chemistry is not simply a mathematics problem.In every physical problem,the result must match the real world.In physics and science,dimensional analysis is a tool to find or check relations among physical quantities by using their dimensions.The dimension of a physical quantity is the combination of the fundamental physical dimensions(usually mass,length,time,electric charge,and temperature)which describe it;for example,speed has the dimension length/time,and may be measured in meters per second,miles per hour,or other units.Dimensional analysis is necessary because a physical law must be independent of the units used to measure the physical variables in order to be general for all cases.One of the most derivation elements from dimensional analysis is scaling and consequently arriving at similarity methods that branch out to two different groups namely self-similarity as the first one,and second kind that through them one can solve the most complex none-linear ODEs(Ordinary Differential Equations)and PDEs(Partial Differential Equations)as well.These equations can be solved either in Eulearian or Lagrangian coordinate systems with their associated BCs(Boundary Conditions)or ICs(Initial Conditions).Exemplary ODEs and PDEs in the form of none-linear can be seen in strong explosives or implosives scenario,where the results can easily be converted to induction of energy in a control forms for a peaceful purpose(i.e.,fission or fusion reactions).