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The article presents the architecture of multi-level information-analytical system (IAS) based on the neural modules network (NMN). This network consists of neural modules which are placed at the three levels (local, region and nation geographically distributed medical centers). Procedures of learning and collectiverelearning of neural modules consider region particularities and are based on analysis, generalization and exchange of experience related to diagnosis of diseases. These procedures provide modification and filtering parameters used as input for the further learning of local and regional neural modules.A few fault-tolerant structures of NMN-based IAS are researched taking into account different options of server and communication redundancy. Reliability block diagrams for redundant IAS structures are developed and formulas for calculation of probability of upstate are analyzed.

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.

The use of wireless sensor networks (WSN) in industry and for forest fire detection has recently become increasingly popular. Assessment of the availability of such networks is an important task, since they perform essential functions in critical situations. Sensor networks can be used to prevent and detect forest fires, and they must meet high availability requirements. Various options for organizing the WSN system are considered - with and without recovery. For such systems, the paper evaluates the probability of no-failure operation, as well as the readiness function, taking into account the network coverage ratio. In the paper the Markov WSN model for evaluating its availability function is developed taking into account the network coverage area. The obtained graphical dependencies allow us to evaluate how a change in the failure rate of sensors or system equipment affects the availability function value. The goal of this paper is to obtain metrics to assess the availability of system for monitoring forest by WSN and the availability function of a network using the Markov models. A special metric, so-called coverage availability factor is suggested in this paper taking into account different combinations of sensor failures which influence on completeness of monitoring forest fires.

Safety and reliability assessment of instrumentation and control (I&C) systems used in different safety-critical industries is a responsible and challenging task. Different assessment models recommended by international and national regulatory documents and used by experts worldwide still have disadvantages and limitations. Therefore, studies of assessment model improvements and refinements are essential. This paper proposes that the assessment models be improved by taking into account different architectures of communications both between different systems and within one particular system. In most models, communication lines are considered absolutely reliable, but the analysis performed shows that the communications should be necessarily addressed. Several analytical models are described to assess the reliability of safety-critical systems for nuclear power plants with different communication options.

Route-based reliability models of the unmanned aerial vehicle (UAV) fleet carrying out monitoring of critical infrastructure facilities and comprising main and redundant UAVs are developed. A nuclear power plant (NPP) and monitoring stations (MSs) are considered as a critical infrastructure and critical infrastructure facilities, respectively. These models are used when multi-UAV routing for NPP monitoring and allow calculating the probability of the successful fulfilment of the plan (SFP) for the UAV fleet to cover the whole target MSs of the NPP. The dependencies showing the relationship of the probability of the SFP to both the UAV reliability function and used route-based reliability models are obtained and explored. An example of the proposed models application for routing main and redundant UAVs of the fleet to cover the whole target MSs of the Zaporizhzhia NPP is given.

The paper is devoted to research of reliability aspects of complex safety-critical systems (CSs). Nowadays such CSs are used in variety of applications, including safety systems for nuclear power plants (NPPs), power grids industrial systems and others. In the paper, models of reliability for CSs are developed and studied, taking into account intermodular and bridge communications. The following problems are resolved: a set of CSs is created based on majority voting according to the “2oo3” logic and redundancy according to the “1oo2” logic considering intermodular and bridge communications; 2) reliability block diagrams (RBDs), analytical models of CS reliability with (multi)cascade redundancy of “2oo3” and “1oo2” principles are developed (including RBDs of reactor trip systems considering communications); 3) the models are studied, the dependencies for failure-free operation probabilities of various CSs, failure rates of intermodular and bridge communications and voting elements are determined; 4) recommendations for the selection of CS types are stated.

Failure modes, effects and criticality analysis (FMECA) is a well-known risk assessment method used to diagnose potential failure modes of a product or system being designed. This method is much based on expert experience and aims to develop improvement strategies so as to reduce the risk of failures. XMECA is a generic extension of this approach that can be applied to analysis not only failures, but other aspects related to safety analysis like intrusions (IMECA) etc. Assumption modes and effect analysis refers to a suggested technique used to minimize risks involved in making assumptions done by expert during performance of XMECA. Possible assessment scenario are described.

Relevance of the paper is confirmed by the need to protect the security systems themselves, not only from physical damage, but also from cyber attacks by intruders. The paper explores the Markov model of the two-zone cyber-physical security system. Evaluation of the functioning of the multi-zone system was carried out taking into account two degrees of degradation (operative condition - the failure state of all zones). The state space of the model (or one fragment) has a dimension of 9 states. In the proposed model, hardware failures caused by vandal attacks on objects of the first zone and software failures due to cyber attacks on the functions of the second zone are considered. The simulation results illustrate different transition intervals of availability indicators of various levels of degradation to a stationary state. For different degrees of degradation, the minimum value of the availability function, the time interval of the transition of the availability function to the stationary mode, and the value of the availability function in the stationary mode are determined. When eliminating software defects and vulnerabilities, the increase in the availability function is 0.23% for a zero level of system degradation.

The information and control systems of Nuclear Power Plant and other safety critical systems are considered as a set of three independent hardware channels including online testing system. Nuclear Power Plant information and control systems design on programmable platforms is rigidly tied to the V-model of the life cycle. Safety and availability during its life cycle are assessed using Markov and multi-fragmental models. The multi-fragmental model MICS32 contains an absorbing state in case of hidden faults and allows evaluating risks of “hidden” unavailability. The MICS42 model simulates the “migration” of states with undetected failures into states with detected faults. These models describe the functioning of the system and the complete elimination of software faults. Results of multi-fragmental modeling are compared to evaluate proof test period taking into account requirements for SIL3 level and limiting values of hidden fault probabilities. Multi-fragment models are included in the assessing method of implementation safety requirements of ICS on programmable platforms. The information technology of decision support in assessing and managing the implementation of the requirements for ICS safety is also considered.

The paper describes modification of the ATA (Attack Tree Analysis) technique for assessment of instrumentation and control systems (ICS) dependability (reliability, availability and cyber security) called AvTA (Availability Tree Analysis). The techniques FMEA, FMECA and IMECA applied to carry out preliminary semi-formal and criticality oriented analysis before AvTA based assessment are described. AvTA models combine reliability and cyber security subtrees considering probabilities of ICS recovery in case of hardware (physical) and software (design) failures and attacks on components casing failures. Successful recovery events (SREs) avoid corresponding failures in tree using OR gates if probabilities of SRE for assumed time are more than required. Case for dependability AvTA based assessment (model, availability function and technology of decision-making for choice of component and system parameters) for smart building ICS (Building Automation Systems, BAS) is discussed.

Reliability analysis of system is a complex problem. One important step is reliability analysis is development of mathematical representation of the investigated system. Modern system is composed by many components with different attributes and properties that should be taken into account in his reliability analysis. Therefore, it is important to choose suitable approach for representation of the system behavior. One such approach is known as structure function. In this paper we will show how the structure function of the system can be used to acquire the reliability function. The specific aspect of this approach is the possibility to use for system with homogenous and heterogeneous components. This will be shown on the reliability analysis of the drone fleet.

Reliability analysis is important properties of any system and healthcare system too. The healthcare system has some specifics in reliability analysis. One of them is the heterogeneity, because this system includes components with different background, kind and properties (for example, equipment and human factor). Other specific of healthcare system is great influence of human factor. Typically, the influence of human factor is evaluated by special methods from special part of reliability engineering that is known as Human Reliability Analysis (HRA). But these methods can not be used for evaluation of technical part (components) of healthcare system. In this paper new method for healthcare system evaluation is developed. This method is proposed for the quantitative analysis of healthcare system and, in particular, for Importance Analysis of this system. It is based on the application of mathematical representation that is named Multi-State System (MSS) to indicate some (more than only two) performance levels in investigated system for more details analysis. In this paper the representation of healthcare system in form of Multi-Valued Decision Diagram is used, that typically used for the system of large dimension.

The information and control system (I&CS) of Nuclear Power Plant (NPP) is considered as a set of three independent hardware channels including on-line testing system. NPP I&C system’s design on programmable platforms is rigidly tied to the V-model of the life cycle. Functional safety and availability during its life cycle are assessed using Markov models. Markov models are used to assess availability function and proof test period. The basic single-fragment model MICS01 contains an absorbing state in case of hidden faults and allows to evaluate risks of “hidden” unavailability. The MICS02 model simulates “migration” of states with undetected failures into states with detected faults. The results of Markov modeling (models MICS01 and MICS02) are compared to evaluate proof test period taking into account requirements for SIL3 level and limiting values of hidden fault probabilities.

The information revolution has caused many aspects of human activity to critically depend on a wide variety of physically existing or virtual technological achievements such as electronic devices, computer systems, algorithms, cloud resources, artificial intelligence hardware and software entities etc. Many of these systems are used in highly sensitive contexts, such as military applications. This implies the existence of an increasing number of unintentional disturbances or malicious attacks. Successful operation requires qualities such as robustness, fault tolerance, reliability, availability and security. All these may be summarized by the title of survivability. Survivability of critical systems working for sensitive applications involves the ability to provide uninterrupted operation under severe disturbances, gracefully degrade when limiting conditions are reached and maintain the ability to resume normal service once the disturbances have been removed. Survivability is an important, even - though non – functional, lifecycle property of many engineering systems. Further desirable elements of survivability include the ability of systems to recognize and resist attacks or accidents, adapt in order to avoid them and modify their behavior in order to diminish the effects of similar future occurrences. This chapter presents a quantitative approach to assessing survivability and an account of survivability in military systems. A scheme for survivability via replica diversity in the implementation of the AES algorithm is then presented. Following that, an algorithm for adaptive attack aversion in user authentication systems is presented that is based on Boolean transformations. An approach for increased survivability in Internet of Things (IoT) systems is then presented. Finally, an algorithm for secure data storage in cloud resources is presented that allows attack detection and avoidance.

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.

The information and control system of smart building is considered as a set of subsystems including a building automation system (BAS) which has three-level structure (automation/control, communication, data base, cloud/management). BAS security and availability during its life cycle are assessed using the Markov models and Monte-Carlo simulation. Markov model is used to calculate BAS availability considering the possibility of recovery and different kinds of the faults. The Monte-Carlo simulation is applied to investigate any flow of intrusions into the BAS by analyzing system availability of a fault/vulnerability to occur during time depending on failure rate of its subsystems. The results of analytical and simulation modeling are compared to assure trustworthiness of availability assessment taking into account attacks on vulnerabilities.

The paper proposes description and classification of life cycle models for safety critical systems. Such description is based on V-models, as a result of analysis of products, processes and attributes of the systems. This allows for the decomposition, verification and management of non-functional requirements to systems, ensuring the completeness of audits and minimizing subsequent costs for their creation and implementation.

The concept of Big Data of Software Reliability (BDSWR) is discussed. According with publication overview it's concluded that BDSWR are not systematically analyzed and used for the reliability assessment of the software systems (SWS). It restricts the potential opportunities of the increase of the SWS reliability assessment accuracy. We offer to use big experimental data about the actual reliability of different SWS which are similar to assessed system. The approach is implemented by way of: 1) the search of BDSWR of the earlier developed similar systems; 2) data collection about of reliability indices of similar systems; 3) use of similar systems indices for reliability assessment and prediction of the evaluated system. Within the approach we offer the technique of big data and similarity-based reliability assessment. The offered technique is based on four principles of the SWS similarity and includes nine stages. The input data of the technique are artefacts of the evaluated system. The output data of the technique are reliability assessments of the evaluated system. The software tools of implementation of the technique are described such as: the agent for search and assessment of data size; the agent of similarity assessment; the agent of reliability assessment; the agent of the verification efficiency improving.

This paper is the continuation of the research devoted to enhancing the adequacy of reliability model of Nuclear Power Plant (NPP) Instrumentation and Control (IC maintenance of the system; using the N-version programming; software updates. Thus, the NPP I&C system reliability model to ensure its high level of adequacy and applicability has to take into account software and a hardware failure, as well as the non-exponential distribution of software updates that are implemented by K-phase Erlang Distribution.

The general structure and main principles of creating a multi-version post-severe NPP accident monitoring system, which consists of one wired and three drone-based wireless network subsystems, are proposed. Reliability block diagrams for the system are built. On the basis of the reliability block diagrams, reliability models of the system are developed. The dependence on probability of failure-free operation for different structures of the system on number of the redundant drones for the Wi-Fi drone-based communication section is obtained and analysed.

Reliability design, availability and performance assessment of multi-state multiprocessor system with structural redundancy involves solving number of issues. This paper outlines a cutting-age technology of the analytical modelling of the discrete-continuous stochastic systems for automated development the Markovian chains to assess the availability and Performance of multi-state multiprocessor system, which shows the algorithm for reliability behaviour. For various configurations of the multi-state multiprocessor system, the use of the proposed model and problem-oriented software, ASNA represents the ability to automate constructed the Markovian chains after developed the structural-automated model. This model includes a number of settings: numbers of processor in the main sub-system; numbers of processor in the diverse sub-system; number of processor in hot standby; number of processor in cold standby; failure rate of the processor; mean time of sub-system repair; the structure of the system’s and reliability behaviours. The proposed structural-automated model for the automated development the Markovian chains are subject to structure adaptation of the multi-state multiprocessor system and/or the algorithms of reliability behaviour. This allows us to obtain a new model and the feasibility to automate development of the Markovian chains.

Operating reliability assessment of instrumentation and control systems (I&Cs) is always one of the most important activities, especially for critical domains like nuclear power plants (NPPs). Intensive use of relatively new technologies like field programmable gate arrays (FPGAs) in I&C which appear in upgrades and in newly built NPPs makes 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 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 I&C at design stage is a quite challenging task. Therefore, operating reliability assessment is one of the most preferable ways to perform comprehensive analysis of FPGA-based NPP I&Cs. This paper summarizes our experience on operating reliability analysis of FPGA based NPP I&Cs.

Nowadays cyber security assurance is one of the key challenges of safety critical software based NPP I&C (Nuclear Power Plants Instrumentation and Control) systems requirements profiling, development and operation. Any I&C system consists of a set of standard software (SW), hardware (HW) and FPGA components. These components can be selected and combined in different ways to address the particular control and safety assurance related tasks. Some of them are proprietary software (PS) and commercial off-the-shelf (COTS) components developed previously. Application of such components reduces the level of safety and cyber security, because they can contain vulnerabilities that were created intentionally. In this case, targeted attacks can lead to a system failure. National Vulnerability Database (NVD) and other open databases contain information about vulnerabilities which can be attacked by insiders or other intruders and decrease cyber security of NPP I&C systems. In this paper, we propose a safety assessment technique of NPP I&C systems, which consists of the following procedures: 1. Analysis of I&C architecture to assess influence of OTS component failures on dependability (reliability and safety) of the system. For that purpose, FMEDA or similar techniques can be applied. As a result, three-dimension criticality matrixes (CM) (with metrics of detection, probability and severity) are developed for different components (SWFCM and HW/FPGAFCM). 2. The IMECA-based assessment of OTS components and their configuration. In this case, CMs (SWICM and HW/FPGAICM) describe the degree of failure component influence on cyber security. 3. Joining of criticality matrixes (SWFCM and HW/FPGAFCM, SWICM and HW/FPGAICM), impact analysis of components depending on degree of influence on cyber security and safety as a whole. 4. Developing of Security Assurance Case and selecting of countermeasures according to safety (cyber security)/costs criteria. The developed tool supports creation of criticality matrixes for each analyzed component of the system and I&C as a whole. Joining of criticality matrixes allows creating common matrix for system cyber security and functional safety. The tool supports decision making to optimize choice of countermeasures according to criterion of safety and security/cost criterion.

A method of improving the reliability of sensory data coming from measurement and control modules of distributed information-measuring systems and control actions formed by those modules is described. The proposed technical solutions by correcting additive, multiplicative and nonlinear error components of analog-to-digital converters provide the high reliability, survivability and. The preliminary reliability assessment of the proposed module is carried-out, and it confirmed the redundancy mechanisms need to be applied on the individual microcontroller, the sensor and the individual execution unit.

One of the most important components of smart grid digital substation is the merging unit (MU). A possibility to consider the MU as a recovered multi-state system (RMSS) is shown. It is also shown that the MU can be considered as a system, which consists of one “core” and one “shell”. The “core” of the MU is its part, which provides functions for performing analog-to-digital (digital) conversion. The “shell” of the MU is its part which provides synchronous measurements of vector functions. Existing approaches to RMSS assessment based on Markov models are considered. Degradation levels for MU are obtained and degradation diagrams (DD) are developed. On the basis of the DD, the models of RMSS availability with using Markov chains (MC) are proposed and analysed. The main feature of the proposed MC-based models is consideration of testing and recovery errors caused by problems of checking coverage and faults of checking means. The models also take into account two different preventive maintenance policies (PMP). According to the first policy (PMP1), preventive maintenance is performed through exponentially distributed time. According to the second one (PMP2), preventive maintenance is performed both through exponentially distributed time and when failures are detected in the current testing. The features of the models applications for RMSS with proposed PMP are shown. Recommendations based on the research results for improving maintenance policy and availability of the MU are formulated. Future research directions can be related to development of MC-based models for smart grid with two and more “core” and “shell”. Besides, development and research of smart grid models for cases of its components multiple failures are important as well.

Digital substations (DS) of smart grid are complex multi-component maintained systems, consisting of a lot of hardware and software components. Failures of the components cause functional and parametrical degradation of the substations. According with systems (DS) structure the reliability-block diagram (RBD), the structure function and the structure function and the Direct Partial Logical Derivatives (DPLDs) for RMSS “electronic transformers—merging unit” are considered. The mathematical tool of logical differential calculus and DPLD in particular are used in many application problems. One of them is reliability engineering. The principal condition of the DPLD application in reliability analysis is the representation of system under investigation by the structure function. We consider the calculation some of these measures as structural, Birnbaum’s, and criticality for the analysis of the electronic transformers—merging unit. The structure function of this unit based on the operation conditions of this system (unit). The construction of this function allows estimating the most important components of this system in stationary state through structural, Birnbaum’s, and criticality importance measures. According with developed technique an example of DS availability model is presented and discussed.

The information and control system of smart building is considered as a set of subsystems including a building automation system (BAS). BAS security and availability during its life cycle are assessed using the Attack Tree Analysis (ATA) and Markov models. The ATA is applied to investigate any intrusions into the BAS by analyzing system probability of a fault/vulnerability to occur during period of time depending on failure probability of its subsystems. Markov model is used to calculate BAS availability considering the possibility of recovery and different kinds of the faults.

This paper presents the approach to research integrated drone-based systems for post emergency monitoring of NPPs as systems with a multi-level degradation. Reliability block diagrams of the systems are built. Degradation levels, conditions which determine them and formulae for calculating the reliability functions of the systems on these levels are proposed. The possibility of using developed models for research systems with a multi-level degradation and using drones are shown

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.

Providing the high availability level for the Instrumentation and Control (I&C) Systems in Nuclear Power Plants (NPP) is highly important. The availability of the critical NPP I&C systems depends on the hardware and software reliability behavior. The high availability of the I&C systems is ensured by the following measures: structural redundancy with choice of the I&C system configurations (two comparable sub-systems in the I&C system, majority voting "2oo3", "2oo4", etc.), maintenance of the I&C system, which implies the repair (changing) of no operational modules, using the N-version programming, software updates, automatic software restart after temporary interrupts caused by the hardware fault. This paper proposes solution of the following case: the configuration of the fault-tolerant I&C system with known reliability indexes of hardware (failure rate and temporary failure rate) is chosen, the maintenance strategy of hardware (mean time to repair, numbers of repair) is specified. In these circumstances it is important to determine quantitative requirements to software reliability: number of software updates during operation I&C system, acceptable duration of the new software version development, acceptable duration of the automatic software restart, determination of acceptable failure rate for each software version. The value of the operational software parameters is determined for the specified availability level of the I&C system. The planned number of software updates determines the duration of testing in order to identify and correct the design faults. Duration of the software testing is limited to the moment when predicted model shows a specified number of hidden (undetected) design faults. To solve this issue, the availability model of the fault-tolerant I&C system was developed in the discrete-continuous stochastic system form. We have estimated the influence of the I&C system on the operational software parameters. Two configurations of I&C systems are presented in this paper: two comparable sub-systems in I&C system, and I&C system with majority voting "2oo3".

Markov's chains are widely applied in quantitative analysis of safety-critical systems. There are few roadblocks for greater application of the Markov's chains: accounting the additional hardware and software component (or FPGA) increases the model state-space and complicates analysis, the non-numerically sophisticated user may find it difficult to decide between the variety of numerical methods and tools to determine the most accurate for their application. Obtaining the high trusted modeling results becomes a nontrivial task. We present the metric-based approach for selection of the applicable solution technique based on the analysis of several Markov chain parameters. Three optimization criteria for informed tool selection were developed to support the decision-making between the wide set of applicable software. Presented approach and criteria are applied as the stepwise tools-and-techniques selection procedure that aims to reduce the risks, increase an accuracy and optimize time needed for Markov's chains analysis. Paper presents the case study of reliability and safety assessment for industrial Nuclear Power Plant Instrumentation and Control system using the optimized tools-and-techniques selection procedure.

Industrial safety critical instrumentation and control systems (I&Cs) are facing more with information (in general and cyber, in particular) security threats and attacks. The application of programmable logic, first of all, field programmable gate arrays (FPGA) in critical systems causes specific safety deficits. Security assessment techniques for such systems are based on heuristic knowledges and the expert judgment. Main challenge is how to take into account features of FPGA technology for safety critical I&Cs including systems in which are applied diversity approach to minimize risks of common cause failure. Such systems are called multi-version (MV) systems. The goal of the paper is in description of the technique and tool for case-based security assessment of MV FPGA-based I&Cs.

New attributes (characteristics, requirements) are proposed as an essential part of a software quality model related to green software. It consists of two main attributes, namely resource (energy) saving and sustainability. Evolution of software quality models is analyzed in context of greenness and reliability. In particular, well known software quality models beginning from on the? rst McCall ' s model (1977) to models described in standards ISO/IEC9126 (2001) and ISO/IEC25010 (2010) are analyzed according to green and reliability issues. Comparison of the software quality models is carried out using a special metrics of complexity and technique considering the number of levels and attributes and their semantics. Prediction of complexity for the next software quality model (2020) is ful ? lled and variants of green software attributes inclusion in model are proposed. Metrics for assessment of reliability, green related and other quality attributes are analyzed considering the standards ISO/IEC25023 and ISO/IEC9126. Results of comparing metric sets of for these standards are described.

The paper discusses the problems of resilient software engineering for unmanned software-based space systems. Resilience is achieved by online patching of software upon emergence of defects providing a stable link to the ground control center. Based on the specifics of satellite orbits it offers two case models: a multifragment one—for systems with a continuous link from geostationary orbits; a multiphase one—for recurrent link from elliptic orbits. The results of the modeling offer the possibility to plan the values of the software initial failure rate and the period of preventive tests that would ensure required reliability and availability.

This paper presents the development of the MFMC-based methodology and technique for modelling and quantitative availability assessment of critical ITinfrastructure consisting of maintained and partially unmanned systems. It takes into consideration a variation of system and component parameters and, in particular, variation of failure rates caused by detection and elimination of design faults.

The paper discusses importance of assessment of interference degree for various attributes of safety-critical systems, including safety and security, proposes applicable metrics, as well as represents an approach to assessment of safety-critical systems. Such approach relies on performance of gap analysis and consideration of influence of human, technique and tool. The approach is applicable to various safety-critical systems, including FPGA-based instrumentation and control (I&C) systems. Requirements of US Nuclear Regulatory Commission to security assessment and assurance for safety critical NNP I&C systems are analyzed. Profiling of the requirements considering features of FPGA-based I&Cs is described. As a case-study some results of security assessing for FPGA platform using Intrusion Modes and Effect Criticality Analysis (IMECA) are illustrated.

Failure Modes, Effects, and Diagnostic Analysis (FMEDA) is a popular technique for evaluation of reliability and safety of a given product. This paper discusses possible challenges in application of FMEDA and related analysis techniques to complex electronic products like FPGA-based platforms. Ways of tool support to make FMEDA automated are addressed.

For multiversion majority-redundant computer-aided control systems, systematization of adaptation methods that are stable to hardware and software failures, a method for estimating their reliability from an event graph model, and a method for selecting a standard architecture with regard for reliability requirements are studied.

The application of complex electronic components such as systems-on-chips (including systems-on-programmable-chips using field programmable gate arrays (FPGAs)) in industrial instrumentation and control systems (I&Cs) causes risks for ensuring of safety. Nuclear power plant (NPP) I&C projects on FPGA are complex solutions which include both software and hardware components. Information security (system’s ability to protect the information and data from unauthorized access and modification) is a subordinate property with respect to safety of many I&Cs, primarily to the NPP reactor trip systems. Such hierarchy may be taken into account by implementation of security informed safety (SIS) approach. Recent events like Stuxnet or Duqu showed vulnerabilities in industrial embedded IT-Systems. In order to remove or reduce security risks, which could increase overall safety risk, the holistic analytical technique are necessary. The goal of the paper is to present the technique for of SIS-based assessment of the NPP I&C systems. The proposed SIS-oriented method of NPP I&C systems assessment includes the models and techniques. To decrease the risk of manual errors, the tool for the SIS-oriented assessment automation is described. The tool is based on joint use of abovementioned models and techniques, is proposed. The tool allows conducting the joint use of the following analysis techniques: GAP and IMECA.

Features of verification FPGA-based safety critical I&C systems (FBIC) using of fault-insertion technique (FIT) are analyzed. The FIT is applied in process of certification to meet requirements of IEC 61508 according with safety integrity level (SIL). Specific aspects of FBIC SIL-certification are described. Concept of FIT-ability, theoretical issues and optimal FIT procedure taking into account different points and means of fault insertion are offered. The developed technique and tool to verify FPGA-based platform RadICS using FIT procedure during SIL-certification are described.

Diversity is the general approach used for decreasing common cause failure (CCF) risks of instrumentation and control (I&C) systems. Differences in equipment, development and verification technologies, implemented functions, etc. can mitigate the potential for common faults. Diversity and defense-in-depth (D3) is the required attribute of Nuclear Power Plant (NPP) I&C systems important for safety. One of the key theoretical and practical problems is diversity estimation and optimization of used version redundancy capacity. Existing NUREG guidelines published in reports CR-7007 and CR-6303 present the technical basis for establishing acceptable mitigating strategies that resolve D3 assessment findings. These approaches work in the terms of diversity attributes and associated criteria aimed at the potential for CCF vulnerabilities and make possible to choose I&C system architecture based on combinations of diversity criteria. But they do not provide measures (diversity indexes or metrics) to calculate reliability of such system in the context of CCF. In the report some other techniques for diversity assessment are analyzed, as well as advantages and disadvantages of these techniques in comprising with NUREG-based method are described. Possibilities of their joint applications and tool support are considered. The combined use of reliability models, diversity metrics and reliability indexes of system components allows enhancement of estimation sensitivity, making sufficiency criteria for diversity and redundancy more concrete and choice of technical solutions more informed and confident at the early stages of NPP I&C system design. The problems for future research are stated as creation of Safety-Case-oriented techniques and tools for multi-version NPP I&C systems assessment.

The diversity approach is commonly used to ensure dependability attributes of such critical computer-based systems as nuclear power plants information and control (NPPs I&C) systems, including the Reactor Trip System. There are two basic problems emerging in this approach - the choice of product-process diversity kinds and assessment of multi-version systems dependability. This paper presents a study for dependability assessment of two architectures of a typical NPP I&C system, the Reactor Trip System: a diverse two-channel system with three parallel tracks on voting logic “2-out-of-3” in each channel and a diverse three-channel system with two parallel tracks on voting logic “1-out-of-2” in each channel. The multi-fragmentation approach is proposed to provide a detailed description of RTS hardware-software interconnection. The resulting models are stiff, which poses a problem in case of achieving the accurate numerical solution. Thus, the models are solved using a number of approaches and tools to verify the results. Obtained results can help to make informed decision between the observed RTS architectures.

This paper considers the aspects of green-technologies application in the human-machine interfaces (HMI) of information and control systems (I&Cs). The improved quality model of user-program interface, which introduces and elaborates green characteristics, is presented. The I&Cs reliability analysis is provided using Markov's model, that takes into account HMI properties and operator errors. The model is solved using mathematical package Mathematica and obtained results analysis is presented. In addition, the paper considers the structure of information technology for HMI quality assessment, that allows to increase the assessment trustworthiness.

The paper is devoted to the analysis of the verification objectives and features for information and control systems (ICS) software at the different stages of life cycle, in particular, on development and operation stages for space ICS software. Theoretic-set description of objectives, verified functions considering their criticality for space systems software and scenarios of online verification are proposed. Availability Markov chains based models are developed for different scenarios of space systems software online verification. Multi-fragment Markov models of ICS software for a serviced spacecraft is researched taking into account updating and removal of detected faults.

Diversity is the general approach used for decreasing common cause failure (CCF) risks of instrumentation and control (I&C) systems. Differences in equipment, development and verification technologies, implemented functions, etc. can mitigate the potential for common faults. Diversity and defense-in-depth (D3) is the required attribute of Nuclear Power Plant (NPP) I&C systems important for safety. One of the key theoretical and practical problems is diversity estimation and optimization of used version redundancy capacity. Existing NUREG guidelines published in reports CR-7007 and CR-6303 present the technical basis for establishing acceptable mitigating strategies that resolve D3 assessment findings. These approaches work in the terms of diversity attributes and associated criteria aimed at the potential for CCF vulnerabilities and make possible to choose I&C system architecture based on combinations of diversity criteria. But they do not provide measures (diversity indexes or metrics) to calculate reliability of such system in the context of CCF. In the report some other techniques for diversity assessment are analyzed, as well as advantages and disadvantages of these techniques in comprising with NUREG-based method are described. The combined use of reliability models, diversity metrics and reliability indexes of system components allows enhancement of estimation sensitivity, making sufficiency criteria for diversity and redundancy more concrete and choice of technical solutions more informed and confident at the early stages of NPP I&C system design. The problems for future research are stated as creation of Safety-Case-oriented techniques and tools for multi-version NPP I&C systems assessment.

The Smart Grid is a movement to bring the electrical power grid up to date so it can meet the current and future requirement so fits customers. Nuclear power plant is a part of smart grid generation system. The problem of safe interaction between nuclear power plant and power grid considering the Fukushima nuclear accident is becoming topical. Despite of undoubted benefits of smart grid for industrial and private customers smart grid technologies bring new risks for NPP. Smart grid security and reliability become new important issues for safety evaluation. Smart grid substations which provide power supply for NPP play can significantly determine NPP safety. A new class of safety critical substation with a critical load should be considered. The smart grid and safety critical smart grid substation (CSGS) mutual influences are evaluated with Bayesian Belief Network (BBN) where nodes represent different CSGS and NPP, links are caused by different types of influences.

Challenges related to verification and validation (VV) of FPGA-based safety critical I&C systems (FICS) are analyzed. One of the mandatory techniques applied in process of VV and certification to requirements of IEC 61508 according with safety integrity level (SIL) is the fault insertion or injection testing (FIT). Specific features of FICS SIL-certification and FIT are described. Concept of FIT-ability, some theoretical issues and algorithm of the optimal FIT procedure taking into account different points and means of fault injection are suggested. The developed technique and tool VTP has been applied to verify modules of FPGA-based platform RadICS during SIL-certification.