FMEDA-Based NPP I&C Systems Safety Assessment: Toward to Minimization of Experts’ Decisions Uncertainty

2016 ◽  
Author(s):  
Alexander Yasko ◽  
Eugene Babeshko ◽  
Vyacheslav Kharchenko
Keyword(s):  
Nuclear Power ◽  
Safety Assessment ◽  
Power Plants ◽  
Failure Modes ◽  
Electronic Components ◽  
Life Cycle Stages ◽  
Safety And Reliability ◽  
The One ◽  
And Control ◽  
Criticality Analysis

There are many techniques for the Nuclear Power Plants Instrumentation and Control (NPP I&C) systems safety assessment. Each of them is suitable for specific types of I&C systems and life cycle stages. Though general procedures of techniques application are specified by standards and described by guides, there is no universal solution that could be unambiguously applied to any NPP I&C system. The Failure Modes, Effects and Diagnostics/Criticality Analysis (FME(D/C)A) is the one that is most often used. Using this technique, the process of assessment is not trivial because of dimensionality problem that is especially critical for modern NPP I&C systems that contain many complex electronic components. Another challenge is the need of compliance to varying requirements of standards. Furthermore, modern I&C systems are based on different platforms (FPGA, microcontrollers). Most of safety and reliability assessment techniques, including mentioned FME(D/C)A, are based on expertise and thereby results are dependent on experts’ decisions very much. This could be a serious challenge, because it is very difficult to find universal experts that have sufficient experience to be equally qualified in different electronic components (FPGA, microcontrollers etc.) used in modern I&C systems. The goal of this paper is to analyze the ways of automation of FMEDA-based NPP I&C systems safety assessment and minimization of uncertainty degree of experts’ decisions. Possible experts’ errors and the uncertainty degree of their decisions are analyzed. We propose integration of all existing FMEA-based techniques into XME(D/C)A that includes Functional FMEA, Design FMEA, Software FMEA, Hardware FMEA etc. Such approach allows performing more comprehensive analysis. Developed tool AXMEA (Automated XMEA) represents an integrated solution that provides the automation of stages of FMEDA technique applied to NPP I&C. The case study is the application of proposed technique and tool during SIL3 certification of the modular RadICS™ platform.

FMEDA and FIT-Based Safety Assessment of NPP I&C Systems Considering Expert Uncertainty

2018 ◽  
Author(s):  
Alexander Yasko ◽  
Eugene Babeshko ◽  
Vyacheslav Kharchenko
Keyword(s):  
Emotional Disorders ◽  
Nuclear Power ◽  
Safety Assessment ◽  
Failure Modes ◽  
Reliability Assessment ◽  
Software Tool ◽  
Critical Systems ◽  
System Specification ◽  
Multiple Faults ◽  
Safety And Reliability

The complexity of modern safety critical systems is becoming higher with technology level growth. Nowadays the most important and vital systems of automotive, aerospace, nuclear industries count millions of lines of software code and tens of thousands of hardware components and sensors. All of these constituents operate in integrated environment interacting with each other — this leads to enormous calculation task when testing and safety assessment are performed. There are several formal methods that are used to assess reliability and safety of NPP I&C (Nuclear Power Plant Instrumentation and Control) systems. Most of them require significant involvement of experts and confidence in their experience which vastly affects trustworthiness of assessment results. The goal of our research is to improve the quality of safety and reliability assessment as result of experts involvement mitigation by process automation. We propose usage of automated FMEDA (Failure Modes, Effects and Diagnostic Analysis) and FIT (Fault Insertion Testing) combination extended whith multiple faults approach as well as special methods for quantitative assessment of experts involvement level and their decisions uncertainty. These methods allow to perform safety and reliability assessment without specifying the degree of confidence in experts. Traditional FMEDA approach has several bottlenecks like the need of manual processing of huge number of technical documents (system specification, datasheets etc.), manual assignment of failure modes and effects based on personal experience. Human factor is another source of uncertainty. Such things like tiredness, emotional disorders, distraction or lack of experience could be the reasons of under- and over-estimation. Basing on our research in field of expert-related errors we propose expert involvement degree (EID) metric that indicates the level of technique automation and expert uncertainty degree (EUD) metric which is complex measure of experts decisions uncertainty within assessment. We propose usage of total expert trustworthiness degree (ETD) indicator as function of EID and EUD. Expert uncertainty assessment and Multi-FIT as FMEDA verification are implemented in AXMEA (Automated X-Modes and Effects Analysis) software tool. Proposed Multi-FIT technique in combination with FMEDA was used during internal activities of SIL3 certification of FPGA-based (Field Programmable Gate Array) RadICS platform for NPP I&C systems. The proposed expert trustworthiness degree calculation is going to be used during production activities of RPC Radiy (Research and Production Corporation). Our future work is related to research in expert uncertainty field and extension of AXMEA tool with new failure data sources as well as software optimization and further automation.

Research on Special Analysis of Verification and Validation in Nuclear Power Instrument and Control System

2017 ◽  
Author(s):  
Jingbin Liu ◽  
Yan Feng ◽  
Ning Qiao ◽  
Yunbo Zhang ◽  
Zhongqiu Wang
Keyword(s):  
Nuclear Power ◽  
Software Verification ◽  
Hazard Analysis ◽  
Security Analysis ◽  
Verification And Validation ◽  
Special Analysis ◽  
Life Cycle Stages ◽  
Traceability Analysis ◽  
And Control ◽  
Criticality Analysis

At present, there is still lack of detailed software V&V guidance standards in China, while a number of US nuclear power units and I&C platform are introduced and applied. So the software verification and validation work in our country usually cited the methods in IEEE 1012. With reference to the requirements of IEEE 1012, the V&V process of the software can be mainly divided into three forms: audit evaluation, special analysis and testing. This paper focuses on these parts and gives a detailed description and annotations of the technical methods and their life cycle stages in IEEE 1012, which cover multiple V&V phases. At the same time, the author puts forward his own understanding of the special analysis approach and procedure, such as criticality analysis, interface analysis, traceability analysis, hazard analysis, risk analysis and security analysis, and gives his own experience and related recommendations.

Application of Probabilistic Safety Assessment in the Design of Instrumentation and Control Systems for Nuclear Power Plants

2017 ◽  
Author(s):  
Pengyi Peng ◽  
Weidong Liu ◽  
Zhichao Yang
Keyword(s):  
Risk Assessment ◽  
Optimal Design ◽  
System Design ◽  
Nuclear Power ◽  
Safety Assessment ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Probabilistic Safety Assessment ◽  
And Control ◽  
Probabilistic Safety

Instrumentation and control (I&C) systems in nuclear power plants (NPPs) have the ability to initiate the safety-related functions necessary to shut down the plants and maintain the plants in a safe shutdown condition. I&C systems of low reliability will bring risks to the safe operation of NPPs. A sufficient level of redundancy and diversity of I&C design to ensure the safety is a major focus when designing a new reactor. Usually multiple signal paths are included in an I&C system design. Meanwhile, besides the protection and safety monitoring system (PMS), other sub-systems of I&C such as the diverse actuation system (DAS) will be included as a diverse backup of PMS to perform the functions of reactor trip and engineered safety features actuation systems (ESFAS). However, the construction costs increase as the level of system redundancy and diversity grows. In fact, from the perspective of deterministic theory, an I&C system of only two chains can meet the single failure criterion. So how to obtain the balance of safety and economy is a challenging problem in I&C system designing. Probabilistic Safety Assessment (PSA) is the most commonly used quantitative risk assessment tool for decision-making in selecting the optimal design among alternative options. In this paper, PSA technique was used to identify whether the I&C system design offers adequate redundancy, diversity, and independence with sufficient defense-in-depth and safety margins in the design of a new reactor. Firstly, detailed risk assessment criteria for I&C design were studied and identified in accordance with nuclear regulations. Secondly, different designs were appropriately modeled, and the risk insights were provided, showing the balance of safety and economy of each design. Furthermore, potential design improvements were evaluated in terms of the current risk assessment criterion. In the end, the optimal design was determined, and uncertainty analyses were performed. The results showed that all four designs analyzed in this paper were met the safety goals in terms of PSA, but each design had a different impact on the balance of risk. As the support systems of the NPP we analyzed were relatively weak, loss of off-site power and loss of service water were two main risk contributors. The common cause failure of reactor trip breakers and the sensors of containment pressure were risk-significant. After identifying the major risk factors, the I&C design team can perform subsequent optimizations in the further design based on the PSA results and achieve an optimal balance between safety and economy.

scholarly journals Neutron flux simulation of a one-dimensional reactor zone taking into account xenon generation

Energetika ◽  
2020 ◽  
Vol 65 (4) ◽  
Author(s):  
Zsófia Tóth ◽  
Dániel Péter Kis
Keyword(s):  
Numerical Methods ◽  
Neutron Flux ◽  
Nuclear Power ◽  
Power Plants ◽  
Research Work ◽  
Reactor Core ◽  
Time And Space ◽  
One Dimensional ◽  
Safety And Reliability ◽  
The One

The energy in nuclear power plants is produced by thermal fission. It is extremely important to be able to monitor the processes in the reactor to ensure the safety and reliability of the power plant. One of the main traits of the reactor core is neutron flux. It changes in time and space therefore it is crucial to be able to simulate its changes with computer codes. In the research work a program code was established in the Matlab software with which the neutron flux of a one-dimensional zone can be simulated with homogenous and heterogenic zone parameters as well. The code is written using the one-group one-dimensional time- and space-dependent diffusion equation. The equation of an average delayed neutron group and xenon and iodine distributions was also included in the system to give a more precise look on the problem. The main innovation in the code is that numerical methods were used to solve the problem: the finite difference approach was applied for the place-dependent and for the time-dependent solution. The advantage of this code compared to other ones is that one-dimensional zones can be simulated in a really short time and it still gives a precise solution because of the complex numerical methods used.

A Risk-Informed On-Line Test and Maintenance Framework for Redundant Instrumentation and Control Systems in Nuclear Power Plants

2004 ◽  
Author(s):  
Lixuan Lu ◽  
Jin Jiang
Keyword(s):  
Reliability Analysis ◽  
Control Systems ◽  
Nuclear Power ◽  
Safety Assessment ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Energy Market ◽  
On Line ◽  
Line Test ◽  
And Control

Deregulation forces Nuclear Power Plants (NPPs) to operate not only safely, but also more economically. Instrumentation and Control (I&C) systems in NPPs play an important role to reduce operational related costs. Therefore, a well-planned test and maintenance (T&M) strategy for I&C systems is more important then ever in this deregulated energy market. This paper presents a general T&M framework for digital I&C systems in NPPs. There are three main parts within this framework: probabilistic safety assessment (PSA), reliability analysis, and costs evaluation. PSA is used to set risk-informed unavailability limits. Reliability analysis is used to derive the relation between the unavailability and the T&M interval. Costs associated with not only T&M, but also reactor mal-shutdowns are evaluated. The Shutdown System Number One (SDSI) in Canadian Deuterium-Uranium (CANDU) based NPPs is used as an example system to illustrate the proposed framework.

scholarly journals PRACTICAL ASPECTS OF OPERATING AND ANALYTICAL RELIABILITY ASSESSMENT OF FPGA-BASED I&C SYSTEMS

2020 ◽  
pp. 75-83
Author(s):  
Eugene Babeshko ◽  
Vyacheslav Kharchenko ◽  
Kostiantyn Leontiiev ◽  
Eugene Ruchkov
Keyword(s):  
Integrated Circuits ◽  
Control Systems ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Failure Modes ◽  
Reliability Assessment ◽  
Operating Reliability ◽  
Analytical Reliability ◽  
And Control

Operating reliability assessment of instrumentation and control systems (I&Cs) is always one of the most important activities, especially for critical domains such as nuclear power plants (NPPs). It is an important source of I&C reliability information preferable to lab testing data because it provides information on I&C reliability under real use conditions. That is the reason that now it is a common practice for companies to have an established process of collecting operating reliability data on a large variety of used components on regular basis, maintaining a database with failure information, total operation time, typical failure modes, etc. The intensive use of complicated components like field-programmable gate arrays (FPGAs) in I&C which appear in upgrades and newly-built nuclear power plants makes the task to develop and validate advanced operating reliability assessment methods that consider specific technology features very topical. Increased integration densities make the reliability of integrated circuits the most crucial point in modern NPP I&Cs. Moreover, FPGAs differ in some significant ways from other integrated circuits: they are shipped as blanks and are very dependent on the design configured into them. Furthermore, FPGA design could be changed during planned NPP outage for different reasons. Considering all possible failure modes of FPGA-based NPP instrumentation and control systems at the design stage is a quite challenging task. Therefore, operating reliability assessment is one of the most preferable ways to perform a comprehensive analysis of FPGA-based NPP I&Cs. Based on information in the literature and own experience, operational vs analytical reliability could be pretty far apart. For that reason, analytical reliability assessment using reliability block diagrams (RBD), failure modes, effects and diagnostics analysis (FMEDA), fault tree analysis (FTA), fault insertion testing (FIT), and other techniques and their combinations are important to meet requirements for such systems. The paper summarizes our experience in operating and analytical reliability assessment of FPGA based NPP I&Cs.

scholarly journals Analysis of Operational Events Caused by Faults of NPP Digital Instrumentation and Control Systems

2019 ◽  
pp. 47-53
Author(s):  
O. Butova ◽  
O. Klevtsov ◽  
O. Pecherytsia ◽  
S. Trubchaninov ◽  
M. Yastrebenetsky
Keyword(s):  
Control Systems ◽  
Nuclear Power ◽  
Power Plants ◽  
Joint Research ◽  
Digital Instrumentation ◽  
Systems Software ◽  
Technical Report ◽  
The One ◽  
Cable Lines ◽  
And Control

The paper presents the analysis of operational events at nuclear power plants (NPPs) of Ukraine caused by failures and defects of the instrumentation and control systems (I&C systems). The effort contains statistical information about the number and the share of operational events at Ukrainian NPPs due to incorrect performance of analog and digital I&C systems in the general amount of events. The categories of these events according to the international and national classifications have been considered. The paper provides for the brief overview of the recently published EC Joint Research Center Technical Report on digital I&C systems at NPPs of foreign countries based on the information from IAEA and U.S. NRC databases. There are causes of operational events due to defects of the specified systems and main recommendations on their prevention. Using the approach similar to the one in the Technical Report, the paper presents the detailed analysis of direct and root causes, as well as correction measures for the operational events at Ukrainian NPPs from 2013 to 2018 caused by digital I&C systems. The experts considered separately four groups of events due to defects of components in the peripheral part of the digital I&C systems (sensors, actuators), central part of digital I&C systems (software and hardware), cable lines and electronic components of analog I&C systems (built-in components). There is an additional analysis of root causes of events related to digital I&C systems by the types of systems and lifecycle stages (design, mounting, operation) and main sources of occurrences within the systems (software, hardware, cables, etc.).

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