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Kim S.M.,Korea Hydro and Nuclear Power Co. | Kim H.T.,Korea Hydro and Nuclear Power Co. | Choi S.S.,Atomic Creative Technology Co.
Canadian Nuclear Society - 31st Annual Conference of the Canadian Nuclear Society and 34th CNS/CNA Student Conference 2010 | Year: 2010

The Wolsong CANDU-6 can be differently treated to a certain extent in terms of operation and safety due to the wide span of commissioning dates between, namely, Unit 1 and Units 2,3,4. This fact resulted in the use of non-unified technical specification (OP&P style in Unit 1 and US standard technical specification style in Units 2,3,4). Thus, it became necessary to improve Limiting Condition for Operations (LCOs) that have been based upon insufficient selection criteria in context of safety standards in the past. The newly developed ISTS for Wolsong CANDU-6 is aimed to achieve the following points, (1) Elimination of unnecessary LCOs that are irrelevant to plant safety, (2) Unification of similar LCOs and relocating them, (3) Application of any improvements gained from operational experiences and/or research works, (4) Reinforcement of technical bases and also placing greater emphasis on human factor principles in order to make technical specification clearer and easier to understand. The goal of Wolsong CANDU-6 ISTS development is to improve plant safety practically by selecting safety significant LCOs, optimise surveillance requirements and reinforce technical bases, in order that the development of the first one for Pressurized Heavy Water Reactor (PHWR) nuclear power plants could be accomplished in the world. Furthermore, it can be utilized as the standard technical specification to prepare Wolsong-1 Improved Technical Specification (ITS) for the continuing operation after the major refurbishment.


Kim H.-J.,Atomic Creative Technology Co. | Chung D.-H.,Atomic Creative Technology Co. | Kim J.-H.,Atomic Creative Technology Co. | Kim S.-M.,Korea Hydro and Nuclear Power Co.
Canadian Nuclear Society - 32nd Annual Conference of the Canadian Nuclear Society and 35th CNS/Can Student Conference 2011 | Year: 2011

A preliminary study has been conducted to help estimate BP/CP uncertainty of Wolsong CANDU 6 reactors by using the WIMS/DRAGON/RFSP-IST code system. The study is focused on the effects of RFSP-IST core modeling practices, especially, in context of laying out mesh spacings associated with the structural materials in the core. The conceptual approach to figure out the effects of mesh spacing layouts associated with the structural materials is supported by the newly updated code system representing the state-of-the-art CANDU reactor physics theory and methodologies, especially, the DRAGON-IST generated incremental cross sections. The application of RFSP-IST fine mesh core model has been exercised to Wolsong Unit 2 core tracking simulations for about one year period of reactor operations. The results so obtained clearly indicate that the improved validation practices and methodology presented here could be qualified to be incorporated into the entire package of BP/CP uncertainty analysis methodologies in order to enhance the quality and reliability of error estimates related to the various topics, e.g., such as, off-line flux mapping errors.


Kim W.-S.,Korea Hydro and Nuclear Power Co. | Lee S.-D.,Korea Hydro and Nuclear Power Co. | Jang K.-S.,Korea Hydro and Nuclear Power Co. | Kim J.-H.,Atomic Creative Technology Co. | And 3 more authors.
International Congress on Advances in Nuclear Power Plants 2010, ICAPP 2010 | Year: 2010

EOP (Emergency Operating Procedure) is the operating procedure document which describes the operator's action needed for the maintenance of nuclear power plant (NPP) safety when a certain accident takes place. EOPs of Wolsong NPP Units 2,3,4 (CANDU 6) have been revised aiming at the optimization of procedure to recover the NPP from an accident and the minimization of human errors. The revised overall EOPs are composed of 2 EOPs describing the accident diagnosis and recovery of critical safety parameters and 13 EOPs describing the operator actions needed for the individual accidents which include LOCA and MSLB and so on. The purpose of the present study is to verify the revised EOPs if the procedures and operator actions described in each EOP are fully appropriate and effective for the safe shutdown of NPP leading to temperature low enough to start the long term cooling using the shutdown cooling system and for the maintenance of fuel and pressure boundary integrity. The verification was carried out with the deterministic safety analysis methodology using the CATHENA computer program which is a Thermalhydraulic numerical code used in the safety analysis of CANDU 6 reactors. CATHENA can simulate the various thermalhydraulic behaviors which are expected to happen during each accident and by various operator actions. From the verification results it can be assured that the revised individual EOPs have the enough appropriateness with respect to the engineering aspects and effectiveness in view of fuel and pressure boundary integrity.


Ko B.-J.,Atomic Creative Technology Co. | Kim M.-H.,Korea Atomic Energy Research Institute | Chung B.-J.,Jeju National University
Journal of Mechanical Science and Technology | Year: 2012

Natural convection experiments were carried out for a wide range of the Grashof number from 10 4 to 5 × 10 9 or for the Rayleigh number from 10 7 to 10 13 in order to seek the proper transition criteria from laminar to turbulent. Using the analogy concept, heat transfer systems were simulated by corresponding mass transfer systems. The copper sulfate electroplating system was chosen as the mass transfer system. The experimental results closely reproduced the McAdams's correlation for laminar and Fouad's for turbulent. The Sherwood numbers obtained from the experiment were proportional to the 1/4 power of Rayleigh number or Grashof number at laminar region and the near 1/3 power at turbulent region as the well known theory. This paper concludes that the proper transition criteria of the natural convection should be the Grashof number of 10 9. The originality of this paper comes from the fact that the study deals with very large value of Schmidt number and that by using the analogy experiment methodology, high values of Rayleigh number and Grashof number were achieved with a relatively short test facility. © 2012 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.


Chung D.-H.,Atomic Creative Technology Co. | Kim H.-J.,Atomic Creative Technology Co. | Kim S.-M.,Korea Hydro and Nuclear Power Co.
Canadian Nuclear Society - 32nd Annual Conference of the Canadian Nuclear Society and 35th CNS/Can Student Conference 2011 | Year: 2011

A study has been carried out to gain a picture and some quantitative evaluations of the structural material mesh spacing layout effects of Wolsong CANDU 6 reactors by using the WIMS/DRAGON/RFSP-IST code system. The newly updated code system has been validated to some extents by comparing the Phase-B pre-simulation results of Wolsong Unit 1 against the previously acquired Phase-B commissioning test measurements of Wolsong Units 1,2,3,4. The code validation efforts resulted in the conclusions that the newly adopted code system could be used for the operational support of Wolsong CANDU 6 reactors. As an ongoing striving for the improvement of safe and economic operation of the reactors, a project on BP/CP uncertainty analysis with respect to the WIMS/DRAGON/RFSP-IST code system is planned. The results obtained in the present study strongly suggest that the effects of mesh spacing layouts of structural materials could be used as an important parameter to help grasp a more realistic glance on the overall off-line flux mapping errors that contribute to BP/CP uncertainties.


Chung D.-H.,Atomic Creative Technology Co. | Cho C.-H.,Atomic Creative Technology Co.
Canadian Nuclear Society - 34th Annual Conference of the Canadian Nuclear Society and 37th CNS/CNA Student Conference 2013 | Year: 2013

The RFSP-IST/CERBERUS [1] simulations are conducted with RRS on in order to be applied for various accident analyses of CANDU 6 reactors, such as, LBLOCA, SBLOCA, In-CORE LOCA, LOR and moderator accidents. The steady-state initial conditions are set by coupling with the thermalhydraulic code CATHENA [2], so that the initial conditions for the other important accident scenarios, e.g., LBLOCA, could also be established based upon the history of RRS actions that realistically follow the reactor operations. The representative cases studied here are selected in application to the moderator drain accidents, which demand the soundness and reliability of RRS predictions that show the capability of coping with the appreciable top-to-bottom flux tilts during the progress of transients. The CANDU 6 RRS algorithm requires a minimal time-step size of Δt=0.5 s that corresponds to the bulk control temporal sequences. An attempt has been made to double the time-step size to Δt=1.0 s. The results so obtained are compared against the simulation results that are obtained by using Δt=0.5 s.


Lim C.-K.,Atomic Creative Technology Co. | Lim C.-K.,Kyung Hee University | Chung B.-J.,Atomic Creative Technology Co. | Chung B.-J.,Kyung Hee University
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2015

Natural convection experiments were carried out on inclined plates. A copper sulfate electroplating system was adopted to simulate heat transfer based on analogy. The lengths of the copper plates were 0.1 and 0.35 m, corresponding to Grashof numbers of 8.06 × 107 and 3.45 × 109. The inclination of the plates varied from upward-facing (UF) horizontal to downward-facing (DF) horizontal. Test results for the DF plate agreed well with Rich’s theory, that the Nusselt number can be calculated by replacing g with gcosθ in the heat transfer correlation for a vertical plate and those for the UF plate reveal that the development of the boundary layer and the flow separation occurs repeatedly for the whole plate length. The copper-plating patterns for the UF plates visualized the location of flow separation. The empirical correlation predicting the critical distance and the heat transfer correlations was proposed. © 2014, Springer-Verlag Berlin Heidelberg.


Chung D.-H.,Atomic Creative Technology Co. | Kim B.-G.,KEPCO E&C | Kim S.-M.,Korea Hydro and Nuclear Power Co. | Suh H.-B.,Korea Hydro and Nuclear Power Co. | And 2 more authors.
Canadian Nuclear Society - 31st Annual Conference of the Canadian Nuclear Society and 34th CNS/CNA Student Conference 2010 | Year: 2010

The Wolsong-1 Phase-B pre-simulations have been carried out with the exclusive use of the code suite WIMS/DRAGON/RFSP-IST in replacement of the previous PPV/MULTICELL/RFSP code system in preparation of tests to be conducted as scheduled in December 2010 after the refurbishment. A comprehensive simulation package has been undertaken starting from the approach to first criticality to the flux measurements and scan. In order to secure the validity of the results, the simulations are performed using both the Uniform and SCM fuel tables. An elaborating contribution has been invested into the work in view of the inexperience of using WIMS/SCM fuel tables as well as incremental cross sections generated by using DRAGON-IST. The overall assessment of simulation results indicates that the newly adopted WIMS/DRAGON/RFSP-IST code suite could be used in replacement of PPV/MULTICELL/RFSP for the verification against the Phase-B test results.


Lim C.-K.,Atomic Creative Technology Co. | Chung B.-J.,Kyung Hee University
International Communications in Heat and Mass Transfer | Year: 2014

Experiments on chimney systems were performed using a copper electroplating system based on the analogy concept. Numerical investigations were carried out to examine the influence of an anode placed at the center of a chimney system. The chimney heights were varied for RaD=7.23×109 and Sc=2094. As the chimney height increased, the heat transfer rates were enhanced but the enhancement rate decreased. Comparison of the numerical results with and without the anode showed different velocity and temperature profiles near the anode. However, those near the heated wall exhibited similar values. Thus, the influence of the anode was negligible at a heated wall. This study provides a theoretical background of using an anode to simulate chimney phenomena. © 2014 Elsevier Ltd.


Ko B.-J.,Atomic Creative Technology Co. | Chung B.-J.,Jeju National University
Transactions of the Korean Society of Mechanical Engineers, B | Year: 2010

Experiments on laminar mixed convection in a vertical pipe were performed for the Re range 1,000-3,000, the GrH range 105-10 8. the Pr range 2,000-7,000, and aspect ratio range 1-7. Using the analogy concept, heat transfer systems were simulated by mass transfer systems. A cupric acid-copper sulfate electroplating system was adopted as the mass transfer system, and the mass transfer rates were measured. The measured Mi values were far greater than those previously reported because of the large value of Pr in this experiment As the aspect ratio in this study was not sufficiently large for the flow to be fulh/ developed, the test results were similar to those for mixed convection on a vertical plate rather than that inside a long vertical pipe. It was concluded that the behavior of laminar mixed convection of a developing flow in a vertical pipe at a low aspect ratio and low GrH is similar to that of laminar mixed convection in the vertical plate. As the aspect ratio and GrH increase, the laminar nixed convection phenomena becomes similar to mat observed in a fully developed flow in the vertical pipe.

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