Field Programmable Gate Array Reliability Analysis Using the Dynamic Flowgraph Methodology

10 The objective of this chapter is to discuss two approaches for reliability analysis of digital 11 instrumentation and control systems in nuclear power plants taking into account the 12 regulatory side. Dynamic Flowgraph Methodology (DFM) and Markov/Cell-to-Cell 13 Mapping Technique (CCMT) are discussed and case studies developed are presented. 14 These case studies involve simplified control systems for a steam generator and a 15 pressurizer of a Pressurized Water Reactor (PWR) plant for the purpose of evaluating 16 each method. Advantages and limitations of each approach are addressed. For the DFM 17 approach, three concerns in the literature are addressed: modeling of the system itself, 18 incorporation of the methodology results into existing Probabilistic Safety Assessments 19 (PSA), and identification of software failures. The Markov/CCMT, which has been used 20 in dynamic probabilistic safety assessments, is approached by means of a simplified 21 digitally controlled water volume control system. The Markov/CCMT methodology 22 results in detailed data of the system reliability behavior in relation to time. However, 23 it demands a higher computational effort than usual as the complexity (i.e., number of 24 components and failure states) of the system increases. As a regulatory research 25 conclusion, the methodologies presented can be used on PSA risk informed assessment, 26 contributing to the regulatory side. 27

A comparison of fault trees and the Dynamic Flowgraph Methodology for the analysis of FPGA-based safety systems part 2: Theoretical investigations

With the development of the nuclear technology, the instrumentation and control (I&C) systems have evolved from the analog systems to the current state-of-the-art digital systems. It has been reported that China has recently developed the digital systems based on Field Programmable Gate Array (FPGA) in CAP1400 nuclear power plant. And the lack of methods in the verification and validation work of the FPGA systems has become an important issue. This thesis describes the basic principles of FPGA, and the development process of FPGA. And then, the thesis proposes an effective improved method—formal verification, describing three methods of formal verification in detail, namely theorem proof, model checking, and equivalence proof. Describing the FPGA verification methodology and pointing out the shortcomings of traditional simulation, comparing the formal verification and traditional simulation verification in terms of complexity, timing, and applications. We also discussed the importance of formal verification method in FPGA. We selected the temperature and power control chip based on FPGA as an example, using System Verilog Assertions (SVA) method of model checking, and verifying the SRAM controller module and the internal calculation module. Through the analysis of the results, this paper proved the feasibility of formal verification methods in the instrumentation and control system of nuclear power plants, and provided some references of verification work for other system chips in instrumentation and control of nuclear power plant in the future work. The thesis showed that verification engineers can use the formal verification method based on SVA to verify the robustness of the system quickly and accurately. This method improves the controllability and observability which are the main drawbacks of the traditional simulation verification. It also avoids several issues in the debug process of traditional simulation verification, improving the accuracy and completeness of the chip verification.

Currently, in few countries, there have been many projects related to the development of Field Programmable Gate Array (FPGA)-based Instrumentation and control (I&C) system designs for their nuclear power plant (NPP), whether for modernization or the new development of NPPs. Indonesia already develops a study related to High Temperature Gas Cooled Reactor as the generation IV for NPPs type for these few years with a specific type which is High Temperature Reactor–10 MW (HTR-10). Since the FPGA-based technology is new in the field, and both the international standards and guidance, from national and international has not defined provisions this issue, therefore verification and validation (V&V) activities for this HTR-10 are mandatory to be included in the design life cycle of I&C system development to get license approval from the national regulatory body. The FPGA-based system needs concentration both in hardware and software development, but commonly only software-related standards that usually included in the design and V&V in the previous computer-based I&C system. Therefore, in this study the V&V plan needs to be developed to state the methods to be required regarding the correctness of the applications of FPGA based I&C system. By arranging this V&V method, we will see whether they are easily applicable to actual systems, had the result to reach the requirement to have reliability, availability, maintainability and safety aspects, and has shortened and easier V&V step than computer-based I&C system. From the results of this study, it can be seen that the results of the method used for V&V between Programmable Logic Controller (PLC)-based and FPGA are almost the same because both have almost the same requirements, especially in software design. Some testing is not mandatory for FPGA-based because of the reduced system complexity. The use of FPGA can shorten the V&V process which can also reduce costs.

Current trends in computing require dedicated chips to speed up computing performances. These dedicated chips or ASICs are designed for specific applications, however, the drawback in this approach is that IC (Integrated Circuits) functionality cannot be changed. In areas where H/W programmability and reconfigurability is required, FPGA is the solution to achieve this. System on Chip (SOC) FPGAs (Field Programmable Gate Arrays) include processor hard blocks connected to fabric through various interconnects. This architecture provides better performance and the ability to run Operating Systems (OS) like Linux <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> that has direct access to programmable FPGA logic. This paper explains how to split the functions of an application code between hard block processor and FPGA fabric logic. OPUS is an open-source audio codec widely used in voice-over-IP (VoiP) applications. The codec execution can be accelerated by moving some of its functions to FPGA logic. One such function of OPUS code is implemented in FPGA logic using High-Level Synthesis (HLS). Shared DDR memory space is used to transfer the data between the processor and FPGA. In this paper, we summarize the reduction in execution time and processor load. The acceleration of OPUS codec allows processing of a greater number of audio channels in the SoC device compared to running the codec entirely on the processor.

Deregulation in the electricity market has resulted in a number of challenges in the nuclear power industry. Nuclear power plants must find innovative ways to remain competitive by reducing operating costs without jeopardizing safety. Instrumentation and Control (I&C) systems not only play important roles in plant operation, but also in reducing the cost of power generation while maintaining and/or enhancing safety. Therefore, it is extremely important that I&C systems are managed efficiently and economically. With the increasing use of digital technologies, new methods are needed to solve problems associated with various aspects of digital I&C systems. Probabilistic Safety Assessment (PSA) has proved to be an effective method for safety analysis and risk-based decisions, even though challenges are still present. This paper provides an overview of PSA applications in three areas of digital I&C systems in nuclear power plants. These areas are Graded Quality Assurance, Surveillance Testing, and Instrumentation and Control System Design. In addition, PSA application in the regulation of nuclear power plants that adopt digital I&C systems is also investigated.

This article proposes a cyber-security improvement plan for the DCS control system of nuclear power plants. Firstly, a brief introduction was given to the traditional architecture of DCS control systems of nuclear power plants. Secondly, the current cyber-security risks faced by DCS control systems in nuclear power plants were summarized, including identity authentication issues, access control issues, communication protocol issues, and data storage issues. Based on the cyber-security risks faced by the DCS control system in nuclear power plants, an improvement plan has been proposed for the DCS platform without increasing external cyber-security equipment. Firstly, regarding identity authentication, it is proposed that nuclear power plants have a very good physical protection that can effectively protect the operator station. However, for the engineer station, a dual factor identity authentication method needs to be added. Secondly, regarding access control, the shortcomings of role-based access control models were pointed out, and a location-based and task-based access control model was proposed. Then, in terms of security communication networks, the sensitive data range of nuclear power plants was analyzed, and communication was divided into internal communication and external communication. For internal communication, pre-stored keys can be used for encrypted communication. For external communication, certificates should be used for identity authentication, and then encrypted communication should be carried out. Finally, for data integrity, control system configurations can be saved through encryption. For passwords, they can be transmitted and saved through hash values.

During design of Instrumentation and Control (I&C) Systems in Nuclear Power Plants (NPP) engineer should take into account requirements for high reliability and safety. Engineer also needs to consider that addition of redundant subsystems (such as reactor protection, monitoring systems etc.) decreases the reliability of the whole I&C system. In this article we present the method for solution of the problem of improving NPP I&C systems safety by improving their reliability. The method is based on the state-transition model of NPP I&C system with split critical failure state. The key feature of this method is the possibility to calculate indicators of reliability and safety using one model. This possibility allows investigating the influences of the maintenance strategies and fault-tolerance design on the system's safety.

Quantum-dot cellular automata (QCA) is a promising, emerging nano-technology based on single electron effects in quantum dots and molecules. This paper presents design, implementation and simulation of a configurable logic block for a field programmable gate arrays (FPGA) by QCA. Previous works focus on QCA-based FPGA that have fixed logic and programmable interconnection or programmable logic and fixed interconnection; however, proposed structures in this paper have programmable logic and programmable interconnection. The presented look-up table implemented with novel structure which has been allowed as frequently as the read/write operation occurs, also acts as a pipeline. In this paper, we presented novel decoders and multiplexers and implemented with QCA, designed with the minimum number of majority gates and cells. Finally, a new configurable logic block (CLB) is designed, implemented and simulated in the QCA, which used signal distribution network method to avoid the coplanar problem of crossing wires. Also, QCADesigner software is used for detailed layout and QCADesigner attend with HDLQ verilog are used for circuit simulation. The proposed CLB is simulated with programming by the QCADesigner software. The area and delay of QCA-based CLB presented in this paper compared to the CLB based on CMOS, nanomaterial and CNT (32 nm). Results show that proposed CLB will do the task with a minimum clock and can be configured as a FPGA.

The design framework of human-machine interface (HMI) provides guiding principles for the display of digital information on the system interface. In order to solve the problem of human error caused by the unreasonable design of information interaction interface of complex system, this paper takes the feedwater flow control system (ARE) of nuclear power plant as an example to optimize . The design of the human-machine interface of the system is based on the framework of function behavior state (FBS), defines the mapping relationship between various levels of the system interface, defines the information requirements of the monitoring system interface and presents the information according to the cognitive decision-making theory, and improves it on the basis of the original interface. The purpose of this research is to make the monitoring interface more consistent with the mental model of the operator and reduce the cognitive workload and error probability, so as to ensure the safe and reliable operation of the nuclear power plant. This research also provides some reference for the optimal design of the HMI of the monitoring system of the nuclear power plant in the future.

Building the machines that advance scientific knowledge is one of the most significant challenges of our time. So-called Big Science instruments are unique; the expertise required to build them is multidisciplinary, and few countries can build and maintain them. Since resources and budgets are not unlimited, these require efficient solutions. Big Science machines take a decade to plan, a decade to build, and at least a decade to operate. One such machine is the largest fusion reactor project, ITER, which promises to be the next step in fusion research and has a big challenge in system integration. To mitigate the integration effort, ITER has invested in standardization, both in software and hardware, introducing standard instrumentation software named Nominal Device Support (NDSv3); Micro Telecommunication Computing Architecture (MTCA) as the long-term hardware standard choice, and EPICS as a general-purpose distributed control system. These control systems are essential in the management of the facility. They provide functions such as communication protocols, process management, monitoring, alarms, and human-machine interfaces. But also, more advanced access to databases or data acquisition systems. The latter is typically managed by a Field Programmable Gate Array (FPGA), of which facilities can easily have thousands of these FPGAs managing millions of signals within the control system environment. Nevertheless, these FPGA data acquisition (DAQ) systems continue to be labor-intensive. Standardized, modular, and open-source frameworks have been proposed to solve this problem, however, the FPGA programming expertise requirement remained. This thesis proposes a complete technology stack that considers these DAQ systems from the control system to the hardware. It provides a methodology using the Open Computing Language (OpenCL) to reduce the FPGA programming effort. The FPGA devices are programmed using C/C++-like environments, which are much simpler than traditional Hardware Description Languages (HDLs). The software, named IRIO-OpenCL, is written in C++ following ITER's NDSv3 model, which abstracts and generalizes the development of software device drivers and simplifies the interface to EPICS. IRIO-OpenCL is specifically designed to simplify the integration of intelligent instrumentation systems, allowing the integration of algorithms into the FPGA without modifying large parts of the supporting library. The MTCA standard was chosen to maintain modularity. The chassis backplane connects to the devices via Ethernet and PCIe, enabling standard communications. The Advanced Mezzanine Card is the typical MTCA FPGA-based DAQ carrier board. It connects the FPGA to the chassis backplane and typically provides FPGA Mezzanine Connectors (FMCs) for plugging in analog-to-digital (ADC) carrier boards. An ADC connected via the FMC interface samples the analog signals passed to the OpenCL processing kernels. Using OpenCL, the FPGA kernels communicate with the host machine in a standardized way. To demonstrate the applicability of this methodology, reference problems were selected from the literature and implemented, both with traditional and deep learning (DL) solutions. The methodology elaborates on connecting the OpenCL kernels for any use case, and the results show examples of kernel sets. The neutron flux measurement problem is solved at 1GS/s in real time using pulse counting and Campbell techniques, using 40% of the target Arria10 FPGA. The DL application example is based on a neutron/gamma discrimination neural network (NN) that achieves a classification rate of up to 1.3 MEvents/s using less than 25% of the target resource. RESUMEN Construir máquinas que avancen el conocimiento científico es uno de los desafíos más significativos de nuestro tiempo. Los instrumentos de la llamada Big Science son únicos; las competencias requeridas para su construcción son multidisciplinares, y pocos países pueden construirlos y mantenerlos. Dado que los recursos y presupuestos no son ilimitados, estos requieren soluciones eficientes. Las máquinas de Gran Ciencia tardan una década en planificarse, una década en construirse y al menos una década en operarse. Una de estas máquinas es el proyecto del reactor de fusión más grande, ITER, que promete ser el siguiente paso en la investigación de fusión y presenta un gran desafío en la integración de sistemas. Para mitigar el esfuerzo de integración, ITER ha invertido en estandarización, tanto en software como en hardware, introduciendo un software de instrumentación estándar llamado Nominal Device Support v3 (NDSv3); Micro Telecommunication Computing Architecture (MTCA) como la elección estándar de hardware a largo plazo, y EPICS como un sistema de control distribuido de propósito general. Estos sistemas de control son esenciales en la gestión de la instalación ya que proporcionan funciones como protocolos de comunicación, gestión de procesos, monitorización, alarmas e interfaces de usuario, además de acceso avanzado a bases de datos o sistemas de adquisición de datos. Este último es típicamente gestionado por un Field Programmable Gate Array (FPGA), de los cuales las instalaciones pueden tener fácilmente miles de unidades gestionando millones de señales dentro del entorno del sistema de control. Estos sistemas de adquisición de datos (DAQ) con FPGA siguen requiriendo programación experta y laboriosa. Se han propuesto marcos estandarizados, modulares y de código abierto para resolver este problema, sin embargo, la necesidad de experiencia en programación FPGA no se ha podido eludir. Esta tesis propone una pila de tecnologías que considera estos sistemas DAQ desde el sistema de control hasta el hardware. Proporciona una metodología utilizando el Open Computing Language (OpenCL) para reducir el esfuerzo de programación FPGA. Los dispositivos FPGA se programan utilizando entornos similares a C/C++, que son mucho más simples que los Lenguajes de Descripción de Hardware (HDL) tradicionales. El software, llamado IRIO-OpenCL, está escrito en C++ siguiendo el modelo de NDSv3 de ITER, que abstrae y generaliza el desarrollo de controladores de dispositivos de software y simplifica la interfaz con EPICS. IRIO-OpenCL está específicamente diseñado para simplificar la integración de sistemas de instrumentación inteligentes, permitiendo la integración de algoritmos en el FPGA sin modificar grandes partes de la biblioteca de soporte. El estándar MTCA fue elegido para mantener la modularidad. El backplane del chasis se conecta a los dispositivos a través de Ethernet y PCIe, habilitando comunicaciones estándar. La Advanced Mezzanine Card es la placa portadora DAQ FPGA típica de MTCA, que conecta el FPGA al backplane del chasis y típicamente proporciona FPGA Mezzanine Connectors (FMC) para conectar placas con conversores analógico-digitales (ADC). Un ADC conectado a través de la interfaz FMC muestrea las señales analógicas pasadas a los núcleos de procesamiento OpenCL. Utilizando OpenCL, los núcleos FPGA se comunican con la máquina anfitriona de una manera estandarizada. Para demostrar la aplicabilidad de esta metodología, se seleccionaron e implementaron problemas de referencia de la literatura, tanto con soluciones tradicionales como de Deep Learning (DL). La metodología elabora ejemplos de conexión de núcleos OpenCL para cualquier caso de uso, y los resultados muestran ejemplos de conjuntos de núcleos. El problema de medición del flujo de neutrones se resuelve a 1GS/s en tiempo real utilizando técnicas de conteo de pulsos y Campbell, utilizando el 40% del objetivo FPGA Arria10. El ejemplo de aplicación DL se basa en una red neuronal para la discriminación neutrones/gammas que logra una tasa de clasificación de hasta 1.3 MEventos/s utilizando menos del 25% de la FPGA objetivo. LABURPENA Ezagutza zientifikoa aurreratzen duten makinak eraikitzea gure garaiko erronka garrantzitsuenetako bat da. Big Science deritzonaren makinak bakarrak dira; beharrezko esperientzia diziplina anitzekoa da, eta herrialde gutxik eraiki eta mantendu ditzakete. Baliabideak eta aurrekontuak mugagabeak ez direnez, konponbide eraginkorrak behar dira. Zientzia Handi makinak hamarkada bat behar dute diseinatuak izateko, hamarkada bat eraikitzeko eta gutxienez hamarkada bat jarduteko. Makina horietako bat fusio-erreaktore handienaren proiektua da, ITER, fusio-ikerketan hurrengo urratsa izango dena eta sistemak integratzeko erronka handia aurkezten duena. Integrazio-ahalegina arintzeko, ITERek estandarizazioan inbertitu du, bai softwarean bai - eta EPICS helburu orokorreko kontrol-sistema banatua. Kontrol-sistema horiek funtsezkoak dira instalazioa kudeatzeko. Komunikazio-protokoloak, prozesuen kudeaketa, monitorizazioa, alarmak eta pertsona-makina interfazeak bezalako funtzioak ematen dituzte, datubaseetarako edo datuak eskuratzeko sistemetarako sarbide aurreratua izateaz gain. Azken hori "Field Programmable Gate Array" (FPGA) batek kudeatzen du, milaka FPGA konektatuz makina bakoitzean eta kontrol-sistemaz milioika seinale kudeatuz. FPGA duten datuak eskuratzeko sistemek (DAQ) programazio aditua eta neketsua eskatzen jarraitzen dute. Problema hori ebazteko marko estandarizatuak, modularrak eta kode irekikoak proposatu dira, hala ere, FPGA hardware programazio espezializatuaren beharra ezin izan da ukatu. Tesi honek DAQ sistema hauek kontrol sistematik hardwareraino kontsideratuz teknologia bilduma bat programazio-ahalegina murrizten du. FPGA gailuak C/C++ antzeko inguruneak erabiliz programatzen dira, - OpenCL izenekoa, C++n idatzita dago, ITERren "Nominal Device Support v3" (NDSv3) eredua jarraituz. Honek software-gailuen garapena diseinu abstraktu eta orokorrez EPICSekiko interfazea sinplifikatzen du. IRIOOpenCL berariaz diseinatuta dago instrumentazio-sistema adimendunen integrazioa sinplifikatzeko, eta algoritmoak FPGAn integratzea ahalbidetzen du, software zati handiak aldatu gabe. Modularitateari eusteko, MTCA estandarra aukeratu da. Txasisaren backplanea Ethernet eta PCIe bidez konektatzen da gailuetara, komunikazio estandarrak gaituz. "Advanced Mezzanine Card" MTCAren ohiko DAQ FPGA plaka eramailea da. FPGA txasisaren backplanera konektatzen du eta, normalean, "FPGA Mezzanine Connectors"ak (FMC) ditu plaka bihurgailu analogiko-digitalak (ADC) konektatzeko. ADCak, FMC interfazearen bidez konektatuta, OpenCL prozesatze-nukleoetara igarotako seinale analogikoak bihurtzen ditu. OpenCL erabiliz, FPGA nukleoak ordenagailuarekin modu estandarizatuan komunikatzen dira. Metodologia horren aplikagarritasuna egiaztatzeko, erreferentziazko adibideak literaturatik hautatu eta nukleoen konexio-adibideak egiten ditu, edozein kasutan erabiltzeko, eta emaitzek nukleo multzoen adibideak erakusten dituzte. Neutroi-fluxuaren neurketak 1GS/s-ko ebazten dira real time errendimenduaz, pultsuak eta Campbell zenbatzeko teknikak erabiliz, Arria10 FPGAren % 40 erabiliz. Azkenik, DL aplikazioaren adibidea, neutroi/gamma sailkapena, sare neuronal batean oinarritzen da, eta FPGAren baliabideen % 25 baino gutxiago erabiliz 1.3 MSailkapen/s sailkapen-tasa lortzen du.

Stability and steady state analysis of control and safety systems of Nuclear Power Plants

This paper presents an I/sub DDQ/-based test strategy for detecting bridging faults in the logic resources of reprogrammable field programmable gate arrays (FPGAs). The proposed approach utilizes the programmability of the configurable logic blocks (CLBs) to achieve 100 percent coverage of I/sub DDQ/ testable bridging faults. We use a hierarchical approach for generating tests and configurations. At the chip level, the CLBs are viewed as a homogeneous two-dimensional array. Two configuration strategies are suggested to simultaneously test each CLB. Within each CLB, we test for external bridging faults between the combinational and sequential logic modules (e.g., flip-flops, multiplexers, lookup tables), Finally, we test for internal bridging faults within each module based on their implementation. Since reconfiguration programming time dominates total test time, even with slow I/sub DDQ/ vectors, we use a bottom-up test generation approach to minimize the number of programming phases first and, then, to minimize the number of test vectors. The Xilinx XC4000 family of SRAM-based FPGAs is used as an example application of the proposed approach. One hundred percent coverage for I/sub DDQ/-testable bridging faults is achieved in five programming phases and 16 I/sub DDQ/ vectors. Since the lookup tables in the CLB can be configured as RAM, the RAM modes are also tested. This requires a further phase, using 48 test vectors and 38 I/sub DDQ/ measurements.

Considering characteristics of nuclear power plant digital instrumentation and control system, challenges of reliability assessment of digital instrumentation and control system are pointed out. As for its dynamic behavior and multi-states failure mode, limitation of traditional methods, research status and applicability of dynamic flowgraph methodology and other advance dynamic reliability assessment approach were introduced and compered. It's concluded that Dynamic flowgraph methodology maybe the dominant one in future after simplify its model procedure and reduction computational cost of its deductive analysis.

Deregulation forces Nuclear Power Plants (NPPs) to operate not only safely, but also more economically. Instrumentation and Control (I&amp;C) systems in NPPs play an important role to reduce operational related costs. Therefore, a well-planned test and maintenance (T&amp;M) strategy for I&amp;C systems is more important then ever in this deregulated energy market. This paper presents a general T&amp;M framework for digital I&amp;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&amp;M interval. Costs associated with not only T&amp;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.