Risk Importance Measures for Maintenance in Non-Coherent Systems

2010 ◽  
Author(s):  
Ye Tao ◽  
Lixuan Lu
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Weak Links ◽  
Coherent System ◽  
Level Control ◽  
Coherent Systems ◽  
Component Importance ◽  
Wide Range ◽  
Undesired Event ◽  
Importance Analysis

Probabilistic Safety Assessment (PSA) has been an important tool to assist Nuclear Power Plants (NPPs) management over the years. Through PSA, the weak links of the whole system can be identified by component importance measures. The importance measures can be classified according to risk significance and safety significance. They signify the role that each component plays in either causing or contributing to the occurrence of an undesired event. A wide range of importance measures have been developed over the years and most of them are geared towards coherent systems. Importance analysis of non-coherent system is rather limited. In this paper, a set of component importance measures for non-coherent systems is analyzed and investigated. The comparison and the selection of the most informative and appropriate measures for guiding the maintenance of a system are presented. A steam generator level control system of NPP is used to demonstrate the application of the results.

scholarly journals A hybrid PSO-PID approach for trajectory tracking application of a liquid level control process

2015 ◽  
Vol 5 (2) ◽  
pp. 63-73 ◽  
Author(s):  
Turker Tekin Erguzel
Keyword(s):  
Water Level ◽  
Pid Controller ◽  
Nuclear Power ◽  
Power Plants ◽  
Control Process ◽  
Nonlinear Process ◽  
Reference Trajectory ◽  
Proportional Integral Derivative ◽  
Level Control ◽  
Steam Generators

Water level control is a crucial step for steam generators (SG) which are widely used to control the temperature of nuclear power plants. The control process is therefore a challenging task to improve the performance of water level control system. The performance assessment is another consideration to underline. In this paper, in order to get better control of water level, the nonlinear process was first expressed in terms of a transfer function (TF), a proportional-integral-derivative (PID) controller was then attached to the model. The parameters of the PID controller was finally optimized using particle swarm optimization (PSO). Simulation results indicate that the proposed approach can make an effective tracking of a given level set or reference trajectory.

scholarly journals The application of Deep Reinforcement Learning in Coordinated Control of Nuclear Reactors

2021 ◽  
Vol 2113 (1) ◽  
pp. 012030
Author(s):  
Jing Li ◽  
Yanyang Liu ◽  
Xianguo Qing ◽  
Kai Xiao ◽  
Ying Zhang ◽  
...  
Keyword(s):  
Control System ◽  
Reinforcement Learning ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Reactor ◽  
Coordinated Control ◽  
Level Control ◽  
Simulation Experiments ◽  
Reinforcement Learning Model ◽  
Reactor Control System

Abstract The nuclear reactor control system plays a crucial role in the operation of nuclear power plants. The coordinated control of power control and steam generator level control has become one of the most important control problems in these systems. In this paper, we propose a mathematical model of the coordinated control system, and then transform it into a reinforcement learning model and develop a deep reinforcement learning control algorithm so-called DDPG algorithm to solve the problem. Through simulation experiments, our proposed algorithm has shown an extremely remarkable control performance.

scholarly journals Component importance in coherent systems with exchangeable components

2015 ◽  
Vol 52 (3) ◽  
pp. 851-863 ◽  
Author(s):  
Serkan Eryilmaz
Keyword(s):  
Importance Measure ◽  
Coherent System ◽  
Coherent Systems ◽  
System A ◽  
Component Importance

This paper is concerned with the Birnbaum importance measure of a component in a binary coherent system. A representation for the Birnbaum importance of a component is obtained when the system consists of exchangeable dependent components. The results are closely related to the concept of the signature of a coherent system. Some examples are presented to illustrate the results.

scholarly journals High-Precision Noncontact Guided Wave Tomographic Imaging of Plate Structures Using a DHB Algorithm

2020 ◽  
Vol 10 (12) ◽  
pp. 4360
Author(s):  
Junpil Park ◽  
Jaesun Lee ◽  
Zong Le ◽  
Younho Cho
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Detection Efficiency ◽  
Detection System ◽  
Automatic Detection ◽  
Guided Wave ◽  
Direct Access ◽  
Experimental Conditions ◽  
Plate Structures ◽  
Wide Range

The safety diagnostic inspection of large plate structures, such as nuclear power plant containment liner plates and aircraft wings, is an important issue directly related to the safety of life. This research intends to present a more quantitative defect imaging in the structural health monitoring (SHM) technique by using a wide range of diagnostic techniques using guided ultrasound. A noncontact detection system was applied to compensate for such difficulties because direct access inspection is not possible for high-temperature and massive areas such as nuclear power plants and aircraft. Noncontact systems use unstable pulse laser and air-coupled transducers. Automatic detection systems were built to increase inspection speed and precision and the signal was measured. In addition, a new Difference Hilbert Back Projection (DHB) algorithm that can replace the reconstruction algorithm for the probabilistic inspection of damage (RAPID) algorithm used for imaging defects has been successfully applied to quantitative imaging of plate structure defects. Using an automatic detection system, the precision and detection efficiency of data collection has been greatly improved, and the same results can be obtained by reducing errors in experimental conditions that can occur in repeated experiments. Defects were made in two specimens, and comparative analysis was performed to see if each algorithm can quantitatively represent defects in multiple defects. The new DHB algorithm presented the possibility of observing and predicting the growth direction of defects through the continuous monitoring system.

Direct Numerical Simulation of a Turbulent Flow on an Oscillating Wall Using Cut-Cell Based Immersed Boundary Method

2016 ◽  
Author(s):  
Chiaki Kino
Keyword(s):  
Turbulent Flow ◽  
Nuclear Power ◽  
Power Plants ◽  
Separated Flow ◽  
Immersed Boundary ◽  
Turbulent Structures ◽  
Flow Induced Vibration ◽  
Production Term ◽  
Large Eddy Simulation Model ◽  
Wide Range

The flow-induced vibration of a pipe is an important issue in various engineering fields, and this phenomenon is widely observed in nuclear power plants. Although turbulent structures play important roles in the velocity and pressure fields in a pipe, only a few studies have been conducted on the turbulent flow on an oscillating wall. In this study, direct numerical simulations were conducted to establish a large eddy simulation model for a turbulent flow on an oscillating wall and scrutinize the energy transfer between the grid scale (GS) and sub-grid scale (SGS). Although energy is generally transferred from the GS to SGS (forward scatter), it is likely that energy is transferred from the SGS to GS (backward scatter) under specific conditions. The present numerical results indicated that backward scatter exists in the production term in the case of a static wavy wall. On the other hand, such backward scatter could not be observed in the case of an oscillating wall. It is well known that separated flows and backward flows are generated behind the crest. Stronger backward flows accelerate the main flow and enhance the velocity gradients in a wide range behind the crest. In the case of an oscillating wall, the development of separated flow is immature because the shape of the wall is not fixed. Eventually, the backward scatter is deemed to be suppressed.

Strategies for Improving Organizational Communication: Case Studies of Nuclear Power Plants Revisited

1985 ◽  
Vol 29 (4) ◽  
pp. 375-379
Author(s):  
Marjorie B. Bauman ◽  
Margery Davidson Boulette ◽  
Harold P. Van Cott
Keyword(s):  
Organizational Communication ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Intervention Strategy ◽  
Weak Links ◽  
Alternative Programs ◽  
Survey Results ◽  
Pros And Cons ◽  
Maintenance Work

This EPRI-sponsored study reviewed the organizational communications used by nuclear power plants (NPPs) and identified weak links in the chain of coordination and information processing required to effectively perform corrective and preventive maintenance in the plants. Preliminary survey results from four NPPs showed that many communication areas deserve special attention in order to improve the work request process and decrease the time delays involved in the performance of maintenance work. This study evaluates two alternative programs designed to improve the effectiveness of the work request process. One approach involves evaluating an automated work request system as a way of improving interdepartmental communication and job performance as they relate to the implementation of maintenance work requests. Another approach assesses the effectiveness of interdepartmental meetings for supervisors as a method for improving organizational communication. Results of this longitudinal study are reported. Pros and cons of each intervention strategy are also discussed.

Systematic Evaluation of Creep-Fatigue Life Prediction Methods for Various Alloys

2009 ◽  
Author(s):  
Yukio Takahashi ◽  
Bilal Dogan ◽  
David Gandy
Keyword(s):  
Power Generation ◽  
Nuclear Power ◽  
Power Plants ◽  
Strain Range ◽  
Creep Damage ◽  
Small Strain ◽  
Systematic Evaluation ◽  
Wide Range ◽  
Creep Fatigue ◽  
Different Temperatures

Failure under creep-fatigue interaction is receiving increasing interest due to an increased number of start-up and shut-down in fossil power generation plants as well as development of newer nuclear power plants employing low-pressure coolant. These situations have promoted the development of various approaches for evaluating its significance. However, most of them are fragment and rather limited in terms of materials and test conditions they covered. Therefore applicability of the proposed approaches to different materials or even different temperatures is uncertain in many cases. The present work was conducted in order to evaluate and compare the representative approaches used in the prediction of failure life under creep-fatigue conditions as well as their modifications, by systematically applying them to available test data on a wide range of materials which have been used or are planned to be used in various types of power generation plants. The following observations have been made from this exercise. (i) Time fraction model has a tendency to be unconservative in general, especially at low temperature and small strain range. Because of the large scatter of the total damage, this shortcoming would be difficult to cover by the consideration of creep-fatigue interaction in a fixed manner. (ii) Classical ductility exhaustion model showed a common tendency to be overly conservative in many situations, especially at small strain ranges. (iii) The modified ductility exhaustion model based on the re-definition of creep damage showed improved predictability with a slightly unconservative tendency. (iv) Energy-based ductility exhaustion model developed in this study seems to show the best predictability among the four procedures in an overall sense although some dependency on strain range and materials was observed.

scholarly journals Power Level Control of Nuclear Power Plant Based on Asymptotical State Observer under Neutron Sensor Fault

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Liming Zhang ◽  
Hongyun Xie ◽  
Qizhi Duan ◽  
Chao Lu ◽  
Jixue Li ◽  
...  
Keyword(s):  
Control System ◽  
Power Control ◽  
Control Systems ◽  
Nuclear Power ◽  
Power Plants ◽  
Power Level ◽  
Level Control ◽  
Power Control System ◽  
Neutron Sensors ◽  
And Control

Power level control is one of the critical functions in the instrument and control system of nuclear power plants (NPPs). In most power level control systems of NPPs, the power level or average neutron flux in reactor cores provided by out-of-core neutron sensors are usually measured as feedback of power control systems, while, as critical measuring devices, there is a risk of damage to out-of-core neutron sensors. For improving the operation reliability of NPPs under the neutron sensors’ failure, a power control system based on power observer is developed in this work. The simulation based on NPP simulator shows the power control system based on the observer is effective when neutron sensors fail.

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