[en] This paper deals with the core cooling performance by natural circulation during normal operation and a flow channel blockage event in an open tank-in-pool type research reactor. The cooling performance is predicted by using the RELAP5/ MOD3.3 code. The core decay heat is usually removed by natural circulation to the reactor pool water in open tank-in-pool type research reactors with the thermal power less than several megawatts. Therefore, these reactors have generally no active core cooling system against a loss of normal forced flow. In reactors with the thermal power less than around one megawatt, the reactor core can be cooled down by natural circulation even during normal full power operation. The cooling performance of natural circulation in an open tank-in-pool type research reactor has been investigated during the normal natural circulation and a flow channel blockage event. It is found that the maximum powers without void generation at the hot channel are around 1.16 MW and 820 kW, respectively, for the normal natural circulation and the flow channel blockage event

[en] The goal of CastScan is the development of a real-time, non-invasive solidification sensor for the metal casting industry. In metal casting processes, there always exists a solidification front, or liquid-solid interface, the shape and stability of which determines the production rate and quality and has a significant economic impact. Current technologies for monitoring the shape and position of the solidification front have their limitations. We have built a tomographic imager, which we have used to determine the shape of the liquid-solid interface in solidifying aluminum. The operating principle of the sensor is based on the density change between liquid and solid which ranges from 4% to 12% for most metals. For high energy x-rays, the absorption is essentially dependent only on the density of the material. The system includes a 6 MeV compact linac and a 128 element detector array. Typical spatial resolutions are ∼1.6 mm with a density precision of ∼2%

[en] It is generally assumed in the mechanistic film dryout model that the critical heat flux (CHF) arises when liquid film calculated from evaporation, droplet entrainment and deposition gets dryout. The dryout of film is usually assumed when film thickness becomes zero. However, it was indicated that the complete dryout assumption can estimate CHF well for uniform heating case but cannot simulate accurately for non-uniform heating case. The critical film thickness concept may be an appropriate approach physically because there is a possibility of instantaneous disappearance of liquid film when it gets very thin. Therefore, a critical dryout film thickness correlation was developed to properly model dryout phenomenon together with MARS code based on experimental data. The modified version of MARS implementing a newly developed critical dryout film thickness correlation was assessed using various dryout data including those of non-uniform heating case and flow reduction transient test. The prediction results showed improved agreement with the experimental data.

[en] Zirconium carbide has been chosen and studied as an advanced material of silicon carbide. In order to collect data on the basic properties and characteristics of Zirconium carbide, studies have been conducted using various methods. As a result of chemically vapor deposed subliming zirconium tetrachloride(ZrCl4) and using methane(CH4) as a source in hydrogen atmosphere, graphite film is deposited.. Zirconium carbide was deposited on the sample where silicon carbide was deposited on a graphite substrate using Zirconium sponge as a Zirconium source. In terms of physical characteristics, the deposited Zirconium carbide showed higher strength, but slightly lower elastic modulus than silicon carbide. In order to evaluate the mechanical properties of a coating layer in pre-irradiation step, internal pressure induced method and direct strength measurement method is carried out. In the internal pressure induced method, in order to produce the requirement pressure, pressure media is used. In the direct strength measurement method, the indentation experiment that indent on a hemisphere shell with plate indenter is conducted. For this method, the finite element analysis is used and the analysis is verified by indentation experiments. To measure the strength of TRISO particle SiC coating, SiC hemisphere shell is performed through grinding and heat treatment. Through the finite element analysis, strength evaluation equation is suggested. Using suggested equation, Strength evaluation is performed and the strength value shows 1025MPa as a result of statistical analysis

[en] The purpose of this study is to develop a test equipment for performance evaluation of safety systems in nuclear power plants. First, we develop an input-output simulator for reactor protection systems, ESF component control systems, and a data acquisition system for these I/O simulators as a hardware for this equipment. Then, we develop a software for human-machine interface system, which is easy-to-use and easy-to-modify. In addition, a simulation tool for a reactor trip switch gear is developed

[en] This study has been carried out under Korea-US joint I-NERI program. KAERI performs the software studies such as the fuel design development and replacement core evaluation and US ORNL performs the hardware studies such as fuel fabrication technology and irradiation tests. KAERI develops and constructs analysis systems and methods for core nuclear, thermal-hydraulic and fuel performance evaluation and safety analysis for application to a FCM fuel and core analysis. Using the analysis system and referencing OPR-1000 core, KAERI develops an optimum FCM fuel design that is neutronically, thermal-hydraulically and mechanically compatible with existing core and highly accident tolerant. For the selected FCM fuel design, quantitative core physics parameters are generated from a detailed core follow analysis for transition and equilibrium cycles of FCM fueled core. Using these parameters, core thermal margin and fuel integrity is assessed by core thermal-hydraulic and fuel performance analysis. And, safety margin and accident tolerance is then assessed for limiting design-basis and beyond-design-basis accidents. Together with the studies on fuel fabrication technologies and qualification performed by US ORNL, the feasibility of the FCM replacement fuel for LWRs is evaluated.

[en] In this project, the assessment and improvement of MARS code was performed by using the domestic thermal hydraulic experimental data. Firstly, thermal-hydraulic experimental data performed at universities in Korea were collected. Secondly, the data were evaluated by using the < Assessment Guidelines for Selection of the Data for Evaluation of MARS code> developed in this project. Thirdly, the < Domestic Thermal-Hydraulic Experiment databank> was developed by using the collected experimental data. Finally, the capability of MARS code was evaluated by using the experimental data (Condensation heat transfer experiment, CCFL experiment, PKL experiment and DVI line break experiment). It will be expected that the databank will be useful to the various T/H code assessment and the suggestions will improve the capability of MARS code

[en] This study was performed a survey of many hospitals using radioisotopes in order to check the amount of use and used radioisotopes, radioactive waste, status of radiation safety and control and the exposure of radiation workers who are working at department of nuclear medicine. At the time of the survey, this study is provided as a guide to the safe handling radionuclides. It will prove helpful all users. The basic objective of radiation safety technique and national standardization of safe handling radioactive materials are to keep the radiation dose to man as low as are under any regulation within the annual dose limits recommended by Most. Further routine monitoring of I-131 high dose therapy ward was carried out the effectiveness of safety precautions taken to prevent undue release of I-131 to the environment

[en] Although sensor techniques using radioisotope radiation sources have long been used in industry for simple applications, such as thickness sensors in sheet materials or as level sensors, recent developments in compact accelerator-based radiation sources as well as in radiation detectors have led to the development of real-time, non-invasive sensors with capabilities beyond that of conventional measuring methods. We will describe two new sensors: the first being a solidification sensor for the metal casting industry which measures in three-dimensions the liquid/solid interface in continuous casting of steel and other metals, and the second being a sensor for real-time analysis of hearth wall integrity in blast furnaces to measure both erosion of carbon thickness and to detect the formation of cracks in the bricks. The prototype of the solidification sensor is based on the use of a compact 6 MeV electron linac and produces tomographic images in real-time of the solidification process in molten aluminum. The blast furnace wall monitor has been modeled and components of the system are currently being designed using the 6 MeV linac as well as a 14 MeV neutron source. (author)

[en] Pure carbon- (C), nitrogen- (N) and titanium- (Ti) doped diamond-like carbon (DLC) coatings were deposited on silicon (Si) micro-molds by dc magnetron sputtering deposition to improve the tribological performance of the micro-molds. The coated and uncoated Si molds were used in injection molding for the fabrication of secondary metal-molds, which were used for the replication of micro-fluidic devices. The bonding structure, surface roughness, surface energy, critical load and friction coefficient of the DLC coatings were characterized with micro-Raman spectroscopy, atomic force microscopy (AFM), contact angle, microscratch and ball-on-disc sliding wear tests, respectively. It was observed that the doping conditions had significant effects on Raman peak positions, mechanical and tribological properties of the coatings. The G peak shifted toward a lower position with N and Ti doping. The DLC coating deposited with 1 sccm N₂ flow rate showed the lowest G peak position and the smoothest surface. The surface energies of the pure carbon and Ti-doped DLC coatings were lower than that of the N-doped DLC, which was more significant at a higher N₂ flow rate. In terms of adhesion and friction coefficient, it was observed that the Ti-doped DLC coating had the best performance. Ti incorporated in the DLC coating decreased the residual stress of the coating, which improved the adhesive strength of the coating with the Si substrate