1,721,243 research outputs found
Instrumentation and Control Systems for Nuclear Power Plants
No full textInstrumentation and Control Systems for Nuclear Power Plants provides the latest innovative research on the design of effective modern I&C systems for both existing and newly commissioned plants, along with information on system implementation. Dr. Cappelli and his team of expert contributors cover fundamentals, explore the most advanced research in control systems technology, and tackle topics such as the human– machine interface, control room redesign, and control modeling. The inclusion of codes and standards, inspection procedures, and regulatory issues ensure that the reader can confidently design their own I&C systems and integrate them into existing nuclear sites and projects
Intelligent identification of boiling water reactor state utilizing relevance vector regression models
No full textModernization of reactor instrumentation and control systems is mainly characterized by the transition from analog to digital systems, expressed by replacement of hardware equipment with new software-driven devices. Digital systems may share intelligence capabilities where except for measuring and processing information may also make decisions. State identification systems are systems that process the measurements taken over operational variables and output the state of the reactor. This paper frames itself in the area of control systems applied to state identification of boiling water reactors (BWRs). It presents a methodology that utilizes machine learning tools, and more specifically, a set of relevance vector machines (RVMs) in order to process the incoming signals and identify the state of the BWR in real time. The proposed methodology is comprised of two stages: in the first stage, each RVM identifies the state of the BWR, while the second stage collects the RVM outputs and decides about the real state of the reactor adopting majority voting. The proposed methodology is tested on a set of real-world BWR data taken from the experimental FIX-II facility for recognizing various BWR loss-of-coolant accidents (LOCAs) as well as normal states. Results exhibit the efficiency of the methodology in correctly identifying the correct state of the BWR while promoting real time identification by providing fast responses. However, a strong dependence of identification performance on the form of kernel functions is also concluded. Copyright © 2018 by ASME
IN-service inspection and on-line monitoring of inaccessible components in nuclear power plants using guided wave technology
No full textOne of the most challenging problems in the on-line monitoring of critical parameters of nuclear plants is the inspection of components that result inaccessible or difficult to reach. In this context, there is an increasing interest of the scientific community and industry for the use of Ultrasonic Guided Waves (UGW) for addressing this issue. In this work, the problem of the applicability of the UGW technique with magnetostrictive sensors to NPP structures is described, together with the outline of the related advantages as well as the main technical concerns that may arise from such applications. This methodology has been tested on experimental activities concerning high temperature applications. Results show the effectiveness of such an approach
Design of advanced controllers for nuclear reactors using an event-triggered control technique
No full textWhen a failure occurs in a nuclear plant, a lack in the response of the controller could lead to serious consequences. The fundamental properties to be ensured by the controller is the plant stability, to be formally proved if possible, and the robustness of the control law, which means fault tolerance and parameter variation tolerance. In this paper, using a mathematical model for the primary circuit of a PWR, accurate enough to catch the nonlinear time-varying, and switching nature of the system, two controllers are designed: an inventory controller for the primary circuit and a pressurizer pressure controller. These controllers do not use direct measurements of the pressurizer pressure or temperature, but use instead pressurizer wall temperature measurements and an observer. Disturbances and parameter variations are compensated by the use of sliding mode estimators, which guarantee robustness to the control scheme. Using an event triggered control control scheme, with varying sampling, the control law has been digitalized for a possible implementation on a digital platform. Copyright © 2015 by JSME
Evaluation of the current fast neutron flux monitoring instrumentation applied to LFR demonstrator alfred: Capabilities and limitations
No full textAmong Gen IV projects for future nuclear power plants, Lead Fast Reactors (LFR) seem to be a very interesting solution due to their benefits in terms of fuel cycle, coolant-safety and waste management. The novelty of the matter causes some open issues about coolant chemical aspect, structural aspects, monitoring instrumentation, etc. Particularly hard neutron flux spectra would make traditional neutron instrumentation unfit to all reactor conditions, i.e. source, intermediate, and power range. Identification of new models of nuclear instrumentation specialized for LFR neutron flux monitoring asks for an accurate evaluation of the environment the sensor will work in. In this study, thermal-hydraulics and chemical conditions for LFR core environment will be assumed, as the neutron flux will be studied extensively by means of the Monte Carlo transport code MCNPX. The core coolant's high temperature drastically reduces the candidate instrumentation, because only some kind of fission chambers and Self Powered Neutron Detectors can be operated in such an environment. This work aims to evaluate the capabilities of the available instrumentation (usually designed for Sodium Fast Reactors, SFRs) when exposed to the neutron spectrum derived from ALFRED, a pool-type small-power LFR project to demonstrate the feasibility of this technology into the European framework. This paper shows that such instruments do follow the power evolution, but they are not completely suitable to detect the whole range of reactor power. Some improvements are then possible in order to increase the signal-to-noise ratio, by optimizing each instrument in the range of reactor power, such to get the best solution. Some new detector designs are here proposed, and the possibilities for prototyping and testing by means of a fast reactor investigated. Copyright © 2015 by JSME
Design of control systems for nuclear plant processes: A hardware-in-The-loop simulation approach
No full textNuclear domain can be considered as a challenging field of application for control systems and the related electronic technology. A prototypal version for controllers is often mandatory for a preventive test and performance evaluation. Control engineers often develop very accurate model of a specific process with very sophisticated control laws using a simulation environment. Even if simulations are fundamental for studying the process and selecting the best control technique, this theoretical effort can be a critical issue for the subsequent hardware implementation of the controller on real electronic devices, leading to a difficult conversion from software to hardware. In this context, the so called Hardware-In-The-Loop HIL simulations is a valid help, allowing a plant process to be simulated in a real time environment and the control unit to be realized on a real component and included in the whole simulation. In this work, HIL simulations are presented and compared to fully software simulations in case of the prototype realization of a pressure controller for a Pressurized Water Reactor PWR. Digital hardware technology is here introduced from the scratch into the project, and the physical implementation of the control unit is taken into account from the beginning, with a significant improvement of the accuracy of the controller in the real process. The control unit is based on a Field- Progammable-Gate-Array (FPGA), a widespread device for realtime control. FPGAs let designers to program a wide number of digital gates in their functionalities with a intrinsic determinism. In addition, processes can be managed in a real parallelism and without the resource sharing as in a CPU operating system. Results demonstrate the effectiveness of such an approach
Design of advanced controllers for pressure control in nuclear reactors: A general approach
No full textWhen a failure occurs in a nuclear plant, a lack in the response of the controller could lead to serious consequences. The fundamental property to be ensured by the controller is the plant stability, possibly proved formally, and at least in the range of validity of the process model. In this work, using a mathematical model for the primary circuit of a PWR, accurate enough to catch the nonlinear, time-varying, and switching nature of the system, and suitable for the control purposes, the reactor power controller, the inventory controller for the primary circuit, and the pressurizer pressure controllers are designed. These controllers do not use direct measurements of the pressurizer pressure or temperature, but they use instead pressurizer wall temperature measurements. Disturbances and parameter variations are compensated by the use of sliding-mode terms, which guarantee further robustness to the control scheme. The switching nature of the controller, reflecting the switching nature of the pressurizer dynamics, and the nonlinear terms implemented in the controllers, along with classical PI actions, ensure better transient behaviors. Hence, they represent an evolution and an improvement with respect to classical PID controllers, usually implemented in standard control actions
Real-time state identification of boiling water reactors using relevance vector machines
No full textAutomated state identification systems facilitate reactor monitoring and control of nuclear systems by consolidating information collected by deployed sensors. In the current paper, we present the use of relevance vector machines (RVM) for real-time state identification of boiling water reactors (BWR). In particular, RVM models utilize the incoming signals of interest and identify in real time the state of the BWR either as normal or as one of the transition states. Each of the RVM models is assigned to a single signal; it receives the measured value at each instance and outputs the identified BWR state. The state that has been designated by the majority of the signals is displayed to the human operator as the identified BWR state. The proposed methodology is applied and tested on a set of signals taken from the FIX-II experimental facility that is a scaled representation of a BWR. Copyright © 2016 by ASME
Nonlinear, advanced pressure controller for a PWR pressurizer
No full textA controller is usually designed using a model (control model) which can be analytically simple, but accurate enough to capture the main characteristics of the underlying physics. There are only a few papers in the literature that report simple dynamic models for boiling or pressurized water reactors. A relatively simple dynamic model for PWR, from the literature, was considered by the authors, and a dynamic controller for the pressurizer water level and pressure was proposed. The nonlinear controller will take advantage of the sliding mode results on parameter estimation, enhancing its robustness versus parameter uncertainties and external disturbances. In particular, the high order sliding mode technique, or super-twisting algorithm, has been used to determine an estimator, embed'ded in the controller dynamics, which estimates in finite time the (unknown) perturbative terms due to parameter uncertainties and external disturbances. In this way, these perturbative terms can be cancelled by the control, and the dynamic behaviour of the controlled system sensibly improves with respect to both PID controllers, usu'ally used in such applications, and nonlinear controllers, cancelling nonlinear terms. A comparative study of the proposed controller, in the presence of faults and/or reference transients in III Gen PWRs, is reported
Fast neutron-flux monitoring instrumentation for lead fast reactors: A preliminary study on fission chamber performances
No full textAlthough Sodium Fast Reactors (SFRs) are the most investigated solutions for the future fast-flux facilities so far, Lead Fast Reactors (LFRs) promise to be a very competitive alternative thanks to their peculiarity concerning coolant-safety, fuel cycle and waste management. Nevertheless, the development of LFRs presents today some drawbacks still to be solved. Due to the harder neutron flux, the current instrumentation developed for SFRs is likely to be extended to LFRs as a first attempt. Otherwise, new monitoring instrumentation could be developed in order to assure more tailored results. Different measurement technologies can be considered for fast flux monitoring and flux absolute measurements in order to provide a reliable and quick calibration of the overall reactor neutron instrumentation. The goal of this paper is to study the validity of typical fast reactor fission chamber designs (e.g. SuperPhénix fission chambers), indicating which are the limitations when used in a LFR environment. Afterwards, alternative detector solutions with enhanced sensitivity and response will be proposed
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