[en] This report is prepared to suggest a practical Probabilistic Safety Assessment (PSA) methodology of safety-critical digital instrumentation and control (I and C) systems. Even though conventional probabilistic safety assessment methods are immature for applying to microprocessor-based digital systems, practical needs force to apply it because the result of probabilistic safety assessment plays very important role in proving the safety of a designed system. Microprocessors and software technologies make the digital system very complex and hard to analyze the safety of their applications. The aim of this is: (1) To summarize the factors which should be represented by the model for probabilistic safety assessment and to propose a standpoint of evaluation for digital systems. (2) To quantitatively presents the results of a mathematical case study which examines the analysis framework of the safety of digital systems in the context of the PSA. (3) To show the results of a sensitivity study for some critical factors

[en] This report describes the review results of the safety assessment and reliability analysis techniques of digital instrumentation and control (I and C) systems. The techniques are far from that of analog I and C systems because of the characteristics of digital systems. This report categorizes the current issues related to the safety assessment of digital I and C systems into three groups as follows: 1. The methodologies which could integrate the characteristics of hardware and that of software. 2. The methodologies which effectively represent safety improvement due to the fault-tolerant mechanisms embedded in digital I and C systems. 3. The methodologies which could effectively represent the phased-mission systems. (author)

[en] To develop the methodology for evaluating the software reliability included in digital instrumentation and control system (I and C), many kinds of methodologies/techniques that have been proposed from the software reliability engineering fuel are analyzed to identify the strong and week points of them. According to analysis results, methodologies/techniques that can be directly applied for the evaluation of the software reliability are not exist. Thus additional researches to combine the most appropriate methodologies/techniques from existing ones would be needed to evaluate the software reliability. (author)

[en] The test facility for performance verification of the control element drive mechanism (CEDM) of next generation power plant was installed at the site of KAERI. The CEDM was featured a mechanism consisting of complicated mechanical parts and electromagnetic control system. Thus, a new CEDM design should go through performance verification tests prior to it's application in a reactor. The test facility can simulate the reactor operating conditions such as temperature, pressure and water quality and is equipped with a test chamber to accomodate a CEDM as installed in the power plant. This test facility can be used for the following tests; endurance test, coil cooling test, power measurement and reactivity rod drop test. The commissioning tests for the test facility were performed up to the CEDM test conditions of 320 C and 150 bar, and required water chemistry was obtained by operating the on-line water treatment system

[en] For dynamic and urgent situation such as emergency situation, it is found that the operator's capability to recover the plant from transient is a critical key for plant safety. From the recorded VTR tape for emergency training of MCR operators, the measures affecting to information deliver are disclosed, verbal protocol analysis is performed for these measures, and thus the communication level is assessed in terms of information deliver

[en] For evaluating the design issues in the advanced MMI, we have studied the selection of evaluation issues, evaluation schedules, and the application method of evaluation results from the beginning of APR1400 MMI design project. For producing input for human reliability analysis, we proposed a new error taxonomy and approach to explain the new human error potential. In order to evaluate whether or not the lifetime of APR1400 I and C system meet 60 years, the lifetime of the system has been calculated by using failure rates in this research. In order to qualify the software of APR1400 protection system, the detail scope and contents are to develop the methods, to evaluate the design results using the methods, and to establish a database for the evaluation. In external vessel cooling strategy to maintain the reactor vessel integrity in a severe accident of the APR 1400, an evaluation methodology was developed, and the failure possibility of penetrations and failure mode of the reactor vessel penetrations have been estimated through experiments and analysis. Two types of experiments have been performed using alumina melt as a simulant and a sustained heating method using an inductor, and their results have been evaluated along with APR 1400 using the LILAC, the FLUENT, and the ABAQUS computer codes

[en] The DVI test specification was prepared. The PIRT(Phenomena Identification Ranking Table) for DVI ECCS in case of LBLOCA was generated and preliminary analysis was performed. Using the MARS 3D best estimate analysis on the DVI ECCS performance test facility was performed in order to modify the thermal-hydraulic models associated with DVI. The MARS code was verified and used for the best-estimate analysis of KNGR LBLOCA and directions for the modification of model and conservativeness of LBLOCA EM was suggested. Based on the analysis and test result the pressure forcing function of sparger was generated. The analysis based on the modified Rayleigh-Plesset equation reasonably reproduced the oscillation of air bubble discharged from sparger. Using similitude rule a procedure for the enlargement of FD was developed and full size FD was designed for verification test. Numerical simulation of flow field in vortex chamber was performed to provide information for the modification of FD for optimum operational characteristics. CEDM life test was performed up to 220,000 ft and technical manual and software for control system was developed. Direct steam condensation with water and air bubble oscillation in IRWST pool was experimentally investigated at small scale test facility

[en] The major objective of this work is tow-fold: one is to develop a methodology to determine the best VHTR types for the nuclear hydrogen demonstration project and the other is to evaluate the various hydrogen production methods in terms of the technical feasibility and the effectiveness for the optimization of the nuclear hydrogen system. Both top-tier requirements and design requirements have been defined for the nuclear hydrogen system. For the determination of the VHTR type, a comparative study on the reference reactors, PBR and PBR, was conducted. Based on the analytic hierarchy process (AHP) method, a systematic methodology has been developed to compare the two VHTR types. Another scheme to determine the minimum reactor power was developed as well. Regarding the hydrogen production methods, comparison indices were defined and they were applied to the IS (Iodine-Sulfur) scheme, Westinghouse process, and the, high-temperature electrolysis method. For the HTE, IS, and MMI cycle, the thermal efficiency of hydrogen production were systematically evaluated. For the IS cycle, an overall process was identified and the functionality of some key components was identified. The economy of the nuclear hydrogen was evaluated, relative to various primary energy including natural gas coal, grid-electricity, and renewable. For the international collaborations, two joint research centers were established: NH-JRC between Korea and China and NH-JDC between Korea and US. Currently, several joint researches are underway through the research centers

[en] These works focus on the development of attainment indices for nuclear hydrogen key technologies, the analysis of the hydrogen production process and the performance estimation for hydrogen production system, and the assessment of the nuclear hydrogen production economy. To estimate the attainments of the key technologies in progress with the performance goals of GIF, itemized are the attainment indices based on SRP published in VHTR R and D steering committee of Gen-IV. For assessing the degree of attainments in comparison with the final goals of VHTR technologies in progress of researches, subdivided are the prerequisite items conformed to the NHDD concepts established in a preconceptual design in 2005. The codes for analyzing the hydrogen production economy are developed for calculating the unit production cost of nuclear hydrogen. We developed basic R and D quality management methodology to meet design technology of VHTR's needs. By putting it in practice, we derived some problems and solutions. We distributed R and D QAP and Q and D QAM to each teams and these are in operation. Computer simulations are performed for estimating the thermal efficiency for the electrodialysis component likely to adapting as one of the hydrogen production system in Korea and EED-SI process known as the key components of the hydrogen production systems. Using the commercial codes, the process diagrams and the spread-sheets were produced for the Bunsen reaction process, Sulphuric Acid dissolution process and HI dissolution process, respectively, which are the key components composing of the SI process

[en] These works focus on the development of attainment indices for nuclear hydrogen key technologies, the analysis of the hydrogen production process and the performance estimation for hydrogen production systems, and the assessment of the nuclear hydrogen production economy. The codes for analyzing the hydrogen production economy are developed for calculating the unit production cost of nuclear hydrogen. We developed basic R and D quality management methodology to meet design technology of VHTR's needs. By putting it in practice, we derived some problems and solutions. We distributed R and D QAP and Q and D QAM to each teams and these are in operation. Computer simulations are performed for estimating the thermal efficiency for the electrodialysis component likely to adapting as one of the hydrogen production system in Korea and EED-SI process known as the key components of the hydrogen production systems. Using the commercial codes, the process diagrams and the spread-sheets were produced for the Bunsen reaction process, Sulphuric Acid dissolution process and HI dissolution process, respectively, which are the key components composing of the SI process