[en] A model free controller utilizing a set of linguistic fuzzy logic of the human operator's experience is developed to control the steam generator water level in a pressurized water reactor. Only 9 rules for control action are generated from the inputs of water level error and mass flow error implicitly representing the time variation of the collapsed water level. The bell type membership functions of the premise side and the result side are tuned by the sensitivity study. This compact fuzzy logic controller shows a robust control during transient and on offset error and oscillation during steady state operation. For a multi-ramp power increase from start-up to full power, the proposed controller shows good performance for the entire range. (Author)

[en] This paper concerns with developing a simplified in-core fuel management scoping tool for PWR. For this purpose the point reactivity model is put into a fuel cycling decision code, FCYPRM. Modified Borresen's coarse-mesh diffusion theory and nodal expansion method are utilized to form a spatial neutron analysis code, CMSNAP. Numerical experiments are performed to determine a set of empirical shuffling rules for working out an automated fuel loading pattern search code, ALPS. The numerical examples are presented for verifying effectiveness and applicability of individual codes. By structuring and applying three codes for reload core design problem of a PWR, it is demonstrated that these codes provide an effective in-core fuel management scoping tool for PWR. (Author)

[en] This paper reports an experimental study of direct containment heating(DCH) which would occur if the primary system pressure is still high at the time of vessel breach during a light water reactor core melt accident. The experiments were conducted in 1/30-scale cavity models of Kori unit 1 and 2 and Young Kwang unit 3 and 4 nuclear power plants. One 1/20-scale model of the Kori plant was also used to investigate the scaling effect. The primary variables in the experiments were initial vessel pressure, vessel breach size enhance the melt dispersal fraction. Also, the cavity geometry appears to affect the dispersal rate greatly. A simple correlation of melt dispersal fraction is proposed in terms of nondimensional effective period. This correlation shows good agreement with the present experimental data, the KAIST data and the BNL data. (Author)

[en] Among those tests performed during the Yonggwang Nuclear Power Plant Units 3 and 4 (YGN 3 and 4) Power Ascension Test period, the Loss of a Main Feedwater Pump test at 100% power is one of the major test which characterize the capability of YGN 3 and 4. In this event, one of the two normally operating main feedwater pumps is tripped resulting in a 50% reduction in the feedwater flow. Unless the NSSS and Turbine/Generator control systems actuate properly, the reactor will be tripped on low SG water level or high pressurizer pressure. The test performed at Unit 3 was successful by meeting all acceptance criteria, and the plant was stabilized at a reduced power level without reactor trip. The measured test data for the major plant parameters are compared with the predictions made by the KISPAC computer code, an updated best-estimate plant performance analysis code, to verify and validate its applicability. The comparison results showed good agreement in the magnitude as well as the trends of the major plant parameters. Therefore, the KISPAC code can be utilized for the best-estimate nuclear power plant design and simulation tool after a further verification using other plant test data. 10 refs., 12 figs., 1 tab. (author)

[en] The adoption of expert systems mainly as operator supporting systems is becoming increasingly popular as the control algorithms of system become more and more sophisticated and complicated. The verification phase of knowledge base is an important part for developing reliable expert systems, especially in nuclear industry. Although several strategies or tools have been developed to perform potential error checking, they often neglect the reliability of verification methods. Because a Petri net provides a uniform mathematical formalization of knowledge base, it has been employed for knowledge base verification. In this work, we devise and suggest an automated tool, called COKEP(Checker of Knowledge base using Extended Petri net), for detecting incorrectness, inconsistency, and incompleteness in a knowledge base. The scope of the verification problem is expended to chained errors, unlike previous studies that assume error incidence to be limited to rule pairs only. In addition, we consider certainty factor in checking, because most of knowledge bases have certainly factors. 8 refs,. 2 figs,. 4 tabs. (author)

[en] A total of 77 cases was identified to have human errors from a total of 255 trips occurred from 1978 to 1992 in Korea NPPs. The cases were analyzed to investigate how many human errors occurred on which work conditions to find out the areas of high priority for human error reduction. For the analysis of the 77 trip cases due to human errors, classifications were made for the following four categories; plant systems, work situation, job types, and error types. Erroneous tasks critically influencing the plant trips were carefully identified and analyzed according to the classifications. Based on the results for the individual cases, the cases were counted for the classification items in each of the four categories, then also for the group of categories to investigate the relationships among the categories in aspects of human error occurrences. As results, the plant systems, work situations, and job types, and error types that are dominant in human errors related to the trips were identified. 9 refs., 10 figs., 9 tabs. (author)

[en] The hydrogenated amorphous silicon (a-Si: H) holds good promise for radiation detection from its inherent merits over crystalline counterpart. For the application to alpha spectroscopy, the induced charge collection in a-Si: H pin detector diodes was simulated based on a relevant non-uniform charge generation model. The simulation was performed for the initial energy and the range of incident alpha particles, detector thickness and the operational parameters such as the applied reverse bias voltage and shaping time. From the simulation, the total charge collection was strongly affected by hole collection as expected. To get a reasonable signal generation, therefore, the hole collection should be seriously considered for detector operational parameters such as shaping time and reverse voltage etc. For the spectroscopy of alpha particle from common alpha sources, the amorphous silicon should have about 70 μm thickness. 9 refs., 7 figs., 2 tabs. (author)

[en] A general method is proposed for elastic stiffness analysis of the leaf type holddown springs using only the geometric data and Young's modulus of the springs. In this method, an engineering beam theory and Castigliano's theory are applied to elastic stiff analysis of the leaf type holddown springs. To show reliability and effectiveness of this method, the elastic stiffness from the proposed method is compared with test results and from the comparison, the proposed method has been proven to be effective for estimating the elastic stiffness of the leaf springs. 10 figs., 2 tabs., 7 refs. (Author)

[en] YGN 3 is the first nuclear power plant to use the Core Protection Calculator (CPC) as the core protection system and the Core Operating Limit Supervisory System (COLSS) as the core monitoring system in Korea. The CPC is designed to provide on-line calculations of Departure form Nucleate Boiling Ratio (DNBR) and Local Power Density (LPD) and to initiate reactor trip if the core conditions exceed the DNBR or LPD design limit. The COLSS is designed to assist the operator in implementing the Limiting Conditions for Operation (LCOs) in Technical Specifications for DNBR/Linear Heat Rate (LHR) margin, azimuthal tilt, and axial shape index and to provide alarm when the LCOs are reached. During YGN 3 initial startup testing, extensive CPC/COLSS related tests were performed to verify the CPC/COLSS performance and to obtain optimum CPC/COLSS calibration constants at various core conditions. Most of test results met their specific acceptance criteria. In the case of missing the acceptance criteria, the test results were analyzed, evaluated, and justified. Through the analysis and evaluation of each of the CPC/COLSS related test results, it can be concluded that the CPC/COLSS are successfully implemented as designed at YGN 3. 6 figs., 5 tabs., 11 refs. (Author)

[en] This paper describes the counting-loss problem for radiation measurement. Multi-channel analyzers and spectrometers adopt various techniques for compensation for counting-losses in processing the radiation pulses from a detector. Researchers have tried to seek the best solution for the problem. However, any absolute solution has not been reached and vendors of radiation instruments use their own algorithms individually. This survey explains the various compensation algorithms with electronic implementation approach. Shortcomings and merits of each algorithm are also reviewed and a direction is suggested of the recommendable development strategy for counting-loss compensation. 11 figs., 1 tabs., 12 refs. (Author)