FIELD OF THE INVENTION 
       [0001]    The present invention relates to analysis of diversity and defense-in-depth; more particularly, relates to evaluating problems in a digital instrument and control system for diversity and defense-in-depth analysis, including software common mode failure, interaction errors between an operator and an interface of the digital instrument and control system and complexity of a software fault. 
       DESCRIPTION OF THE RELATED ARTS 
       [0002]    Single failure criterion for safety of a nuclear power plant requires that any single failure in a safety system do not make the whole safety system stop running. Hence, redundant facilities are usually set at critical points to conform to the single failure criterion. In another word, when a facility fails, another facility of the like is turned on to prevent from hurting safety of the nuclear power plant. 
         [0003]    A digital instrument and control system is driven by software, which is different from mechanisms of software faults and failures of the digital instrument and control system. Although traditional redundant facilities may reduce impact of hardware failures, software common mode failure of the digital instrument and control system would destroy defense mechanism of the redundant facilities. Hence, if common mode failure happens, the redundant facilities may fail to function. Since the digital instrument and control system is driven by software, serious situation may be resulted owing to the malfunction of the digital instrument and control system once the common mode failure happens. 
         [0004]    As is obvious to modern life, the digital instrument and control system is widely used, where its functions are powerful and its interfaces are user friendly with abundant information provided. However, some critical issues may beat the safety system and increase difficulties in diversity and defense-in-depth analysis, like software common mode failure of the digital instrument and control system, interaction errors between an operator and an interface of the digital instrument and control system and complexity of a software fault. Among them, the interaction errors between the operator and the interface of the digital instrument and control system are most crucial. Yet, solutions for the crucial issue are still not ideal. Hence, the prior arts do not fulfill all users&#39; requests on actual use. 
       SUMMARY OF THE INVENTION 
       [0005]    The main purpose of the present invention is to provide a simulation platform for evaluating problems in a digital instrument and control system for the diversity and defense-in-depth analysis, including software common mode failure, interaction errors between an operator and an interface of the digital instrument and control system and complexity of a software fault. 
         [0006]    The second purpose of the present invention is to estimate possible interaction errors between an operator and an interface of the digital instrument and control system to find new fault modes and to deduce scenarios for finding weakness of a safety system and evaluating a design of a diversity and defense-in-depth system to improve safety of a nuclear power plant 
         [0007]    To achieve the above purposes, the present invention is a diversity and defense-in-depth simulation apparatus, comprising: (a) a safety control system simulator, comprising: (a1) a hardware architecture being an industrial personal computer in a cabinet of the safety control system simulator and having a first hardware I/O interface; (a2) a software architecture, comprising: (a21) a first user interface layer; (a22) a core model of said safety control system simulator; (a23) a first hardware I/O data processing module; (a24) a first operating system; and (a25) a PXI hardware I/O interface layer; and (a3) a kernel architecture, comprising: (a31) a program workflow control module; (a32) an external interface processing module; and (a33) a safety control system module; and (b) an enhanced nuclear power plant simulator, comprising: (b1) a hardware architecture being an industrial personal computer in a cabinet of the enhanced nuclear power plant simulator and having a second hardware I/O interface; (b2) a software architecture, comprising: (b21) a second user interface layer; (b22) an enhanced nuclear power plant simulation module; (b23) a second hardware I/O data processing module; (b24) a second operating system; and (b25) a hardware I/O interface layer; and (b3) a kernel architecture, comprising: (b31) a system calculation module; and (b32) a nuclear power plant simulation calculation module, where parameters of the enhanced nuclear power plant simulator and control responses of the safety control system simulator are mutually transferred through hard-wired connections at backplanes. Accordingly, a novel diversity and defense-in-depth simulation apparatus is obtained. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which 
           [0009]      FIG. 1  is the structural view showing the preferred embodiment according to the present invention; 
           [0010]      FIG. 2  is the view showing the hardware architecture; 
           [0011]      FIG. 3  is the view showing the software architecture of the safety control system simulator; 
           [0012]      FIG. 4  is the view showing the software architecture of the enhanced nuclear power plant simulator; 
           [0013]      FIG. 5  is the view showing the kernel architecture of the safety control system simulator; and 
           [0014]      FIG. 6  is the view showing the kernel architecture of the enhanced nuclear power plant simulator. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    The following description of the preferred embodiment is provided to understand the features and the structures of the present invention. 
         [0016]    Please refer to  FIG. 1 , which is a structural view showing a preferred embodiment according to the present invention. As shown in the figure, the present invention is a diversity and defense-in-depth simulation apparatus, comprising a safety control system simulator  1  and an enhanced nuclear power plant simulator  2 . 
         [0017]    The safety control system simulator  1  comprises a user interface  11  and a safety control system  12 . Therein, the user interface  11  is used for operating a safety system manually and for showing information. The safety control system  12  simulates behaviors of the safety system, where parameters of the enhanced nuclear power plant simulator  2  are received through a first hardware I/O interface  101  of the safety control system simulator  1 ; and corresponding commands are transferred through the first hardware I/O interface  101  to control the enhanced nuclear power plant simulator  2  according to control logics of the safety system. 
         [0018]    The enhanced nuclear power plant simulator  2  is based on a nuclear power plant simulator  21 , which receives commands through a second hardware I/O interface  201  to control the safety control system simulator  1  and feeds back reactions of a nuclear power plant for a diversity and defense-in-depth analysis. 
         [0019]    Please refer to  FIG. 2 , which is a view showing a hardware architecture. As shown in the figure, a hardware architecture according to the present invention comprises a safety control system cabinet  10  and a nuclear power plant simulator cabinet  20 . 
         [0020]    The safety control system cabinet  10  is an industrial personal computer platform having a first hardware I/O interface  101 , where a safety control system simulator has safety control logics developed through an intuitive graphic programming language; and the first hardware I/O interface  101  is a data acquisition card, a chassis or a control card. 
         [0021]    The nuclear power plant simulator cabinet  20  is an industrial personal computer platform having a second hardware I/O interface  201 , where the second hardware I/O interface  201  of an enhanced nuclear power plant simulator  2  is an industrial hardware I/O interface to communicate with a nuclear power plant simulator  21  (shown in  FIG. 1 ) through TCP/IP. Thus, the safety control system simulator  1  and the enhanced nuclear power plant simulator  2  are well communicated through the first and the second hardware I/O interfaces  101 , 201 . 
         [0022]    Hence, parameters of the enhanced nuclear power plant simulator  2  and responses of control of the safety control system simulator  1  are mutually transferred between the first hardware I/O interface  101  of the safety control system simulator  1  and the second hardware I/O interface  201  of the enhanced nuclear power plant simulator  2  through hard-wired connections at backplanes. 
         [0023]    Please refer to  FIG. 3 , which is a view showing a software architecture of a safety control system simulator. As shown in the figure, a software architecture of a safety control system simulator comprises a first user interface layer  111 , a safety control core model  112 , a first hardware I/O data processing module  113 , a first operating system  114  and a PXI hardware I/O interface layer  115 . 
         [0024]    The first user interface layer  111  provides manual operation of the safety control system simulator; and shows parameters of an enhanced nuclear power plant simulator and states of the safety control system simulator under automatic control. 
         [0025]    The safety control core model  112  is a core program of the safety control system simulator to simulate control logics of the safety control system simulator; receives parameters of the enhanced nuclear power plant simulator through the first hardware I/O data processing module  113 , like water level signals and pressure signals, etc.; and obtains control commands through logical calculation with the parameters to control facilities in the enhanced nuclear power plant simulator. 
         [0026]    The first hardware I/O data processing module  113  converts electrical data obtained from the PXI hardware I/O interface layer  115  into industrial sums to judge correctness of signals and provides warning to the safety control core model  112 . 
         [0027]    The first operating system  114  has a hardware I/O interface driver  1141  and is a platform executing the safety control core model  112  to read data required for the first hardware I/O data processing module  113  through the hardware I/O interface driver  1141  or to write data to the PXI hardware I/O interface layer  115 , immediately. 
         [0028]    The PXI hardware I/O interface layer  115  is composed of a power supplier and a hardware I/O interface conformed to industrial PXI standards to process analog and digital signals; is connected with the first operating system  114  through signals in an optical fiber; and is connected with the enhanced nuclear power plant simulator through physical wires. 
         [0029]    Please refer to  FIG. 4 , which is a view showing a software architecture of an enhanced nuclear power plant simulator. As shown in the figure, a software architecture of an enhanced nuclear power plant simulator comprises a user interface layer  211 , an enhanced nuclear power plant simulation module  212 , a second hardware I/O data processing module  213 , a second operating system  214  and a hardware I/O interface layer  215 . 
         [0030]    The second user interface layer  211  provides manual operation of an enhanced nuclear power plant simulator; and shows parameters of the enhanced nuclear power plant simulator and states of control of a safety control system simulator. 
         [0031]    The enhanced nuclear power plant simulation module  212  is a core program of the enhanced nuclear power plant simulator for simulating facilities of a safety system; and receives control commands of the safety control system simulator through the second hardware I/O data processing module  213  to control the safety control system simulator with parameters of the enhanced nuclear power plant simulator and reactions of the facilities. Therein, the facilities include all kinds of pumps, gates, motors and safety facilities; and the reactions include reactions of a core and calculations of pressures, flows and temperatures. 
         [0032]    The second hardware I/O data processing module  213  converts electrical data obtained from the hardware I/O interface layer  215  into industrial sums to judge correctness of signals and provides warning to the enhanced nuclear power plant simulation module  212 . 
         [0033]    The second operating system  214  has a second hardware I/O interface driver  2141  and is a platform executing the enhanced nuclear power plant simulator to read data from the second hardware I/O data processing module  213  through the second hardware I/O interface driver  2141  or to write data to the hardware I/O interface layer  215 , immediately. 
         [0034]    The hardware I/O interface layer  215  is an industrial programmable logic controller (PLC), comprising a central processing unit (CPU), a power supplier and an analog/digital signal I/O module; is connected with the second operating system through an Ethernet network; and is connected with the safety control system simulator through physical wires. 
         [0035]    Please refer to  FIG. 5 , which is a view showing a kernel architecture of a safety control system simulator. As shown in the figure, a kernel architecture of a safety control system simulator comprises a program workflow control module  121 , an external interface handling module  122  and a safety control system module  123 . 
         [0036]    The program workflow control module  121  loads initial conditions from a file system and, after initializing all parameters, controls a whole simulation flow, including simulation start and simulation stop. At the same time, the program workflow control module  121  coordinates data communication and controls work flow between the external interface handling module  122  and the safety control system module  123 . 
         [0037]    The external interface handling module  122  comprises a file system processing module  1221 , a first man-machine interface processing module  1222  and a third hardware I/O data processing module  1223 , where the file system processing module  1221  accesses data of an external file system, loads the initial conditions and initializes the parameters; the first man-machine interface processing module  1222  receives and processes parameters and commands from an external user interface and provides parameters of a power plant on the external user interface; and the third hardware I/O data processing module  1223  receives and sets analog and digital signals of an enhanced nuclear power plant simulator from an external hardware interface through the first and the second hardware I/O data processing module  113 , 213  (shown in  FIG. 3  and  FIG. 4 ). 
         [0038]    The safety control system module  123  is a core module of a safety control system simulator to simulate control logics of a safety system, comprising basic logic control, logic control of qualified OR gate with 2 inputs ON (QOR2), linear control (PID control), and trip control of safety signal. The safety control system module  123  receives parameters of the enhanced nuclear power plant simulator through the third hardware I/O data processing module  1223  to response corresponding control signals for facilities. At last, the control signals are transferred to the enhanced nuclear power plant simulator through the third hardware I/O data processing module  1223  to control the facilities. 
         [0039]    Please refer to  FIG. 6 , which is a view showing a kernel architecture of an enhanced nuclear power plant simulator. As shown in the figure, a kernel architecture of an enhanced nuclear power plant simulator comprises a system calculation module  221  and a nuclear power plant simulation calculation module  222 . 
         [0040]    The system calculation module comprises a general core flow control module  2211 , an interface processing module  2212  and a database processing module  2213 . 
         [0041]    The general core flow control module  2211  processes calculations on starting and calculations on running simulation. After starting the system, parameters of a power plant are loaded from database to process initial calculations with the parameters; and, then, basic calculations, including version declaration of a user interface, are processed. At this moment, commands and situations are inputted with control authority transferred to the nuclear power plant simulation calculation module  222  for simulation thereafter. 
         [0042]    The interface processing module  2212  comprises a second man-machine interface processing module and a fourth hardware I/O data processing module, where the second man-machine interface processing module receives and processes parameters and commands from an external user interface and shows the parameters and results on a man-machine interface. The fourth hardware I/O data processing module converts electrical data obtained from a PLC into industrial sums to judge correctness of signals and provides warning to the enhanced nuclear power plant simulator. 
         [0043]    The database processing module  2213  accesses databases, where initial conditions are loaded before simulations; parameters and dose amounts are dynamically recorded during simulation; and a plot database and a malfunction database are accessed. 
         [0044]    The nuclear power plant simulation calculation module  222  comprises a common calculation module  2221 , a simulation calculation module  2222  and a historical records management module  2223 . The nuclear power plant simulation calculation module  222  processes a cycle of simulation in 0.5 seconds; then, after the simulation, control authority is transferred to the historical records management module  2223 . Therein, the common calculation module  2221  comprises parameter declarations and theoretical model functions of the enhanced nuclear power plant simulator; and the theoretical model functions comprise Moody chart functions, Euler equations, decay heat curve functions and interpolation functions. 
         [0045]    The simulation calculation module  2222  comprises processes of initializing parameters of the enhanced nuclear power plant simulator and processing simulation functions of the enhanced nuclear power plant simulator. Besides, the simulation calculation module  2222  controls a simulation flow of the enhanced nuclear power plant simulator by controlling control rods, a core, a spray system, containment, an emergency cooling system and a plurality of pumps. 
         [0046]    The historical records management module  2223  simultaneously renews and shows parameters of a power plant on a user interface layer; and records the parameters of the power plant through the database processing module  2213 . 
         [0047]    Thus, a diversity and defense-in-depth simulation apparatus is obtained according to the present invention, which provides a simulation platform for evaluating problems in a digital instrument and control system, including software common mode failure, interaction errors between an operator and an interface of the digital instrument and control system and complexity of a software fault. Hence, interaction errors between an operator and an interface of the digital instrument and control system can be estimated to find new fault modes and to deduce scenarios. A method for finding weakness of a safety system can be thus developed to evaluate a design of a diversity and defense-in-depth system for improving safety of a nuclear power plant. 
         [0048]    To sum up, the present invention is a diversity and defense-in-depth simulation apparatus, where a simulation platform is provided for evaluating problems in a digital instrument and control system and interaction errors between an operator and an interface of the digital instrument and control system; and thus new fault modes can be found and scenarios can be deduced to develop methods for finding weakness of a safety system and further for evaluating a design of a diversity and defense-in-depth system to improve safety of a nuclear power plant 
         [0049]    The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.
A simulator system transfers parameters between a power plant simulator and a safety control simulator. Problems concerning software common mode failure, interface interactions errors, software failure complexity, and so on, are evaluated. Thus, diversity and defense-in-depth are analyzed and safety is improved.