[en] The spacer grid is one of the main structural components in the fuel assembly, which supports the fuel rods, guides cooling water, and protects the system from an external impact load, such as earthquakes. In order to develop the spacer grid with the high mechanical performance, the mechanical and structural properties of the spacer grids must be extensively examined while designing it. In this report, the mechanical/structural test methods, i.e. the characteristic test of a spacer grid spring or dimple, static buckling test of a partial or full size spacer grid and dynamic impact test of them are described. The characteristic test of a spacer grid spring or dimple is accomplished with universal tensile test machine, a specimen is fixed with test fixture and then applied compressive load. The characteristic test data is saved at loading and unloading event. The static buckling test of a partial or full size spacer grid is executed with the same universal tensile testing machine, a specimen is fixed between cross-heads and then applied the compressive load. The buckling strength is decided the maximum strength at load vs. displacement curve. The dynamic impact test of a partial or full size spacer grid is performed with pendulum type impact machine and free fall shock test machine, a specimen is fixed with test fixture and then applied the impact load by impact hammer. Specially, the pendulum type impact test machine is also possible under the operating temperature because a furnace is separately attached with test machine

[en] Tube bundle structures within a Boiler or heat exchanger are laid the fluid-structure, thermal-structure and fluid-thermal-structure coupled boundary condition. In these complicated boundary conditions, Fluid-structure interaction (FSI) occurs when fluid flow causes deformation of the structure. This deformation, in turn, changes the boundary conditions for the fluid flow. The structural analysis discipline, and then independently analyzed each other. However, the fluid dynamic force effect the behavior of the structure, and the vibration amplitude of the structure to fluid. FSI analysis model was separately created fluid and structure model, and then defined the fsi boundary condition, and simultaneously analyzed in one domain. The analysis results were compared with those of the experimental method for validating the analysis model. Flow-induced vibration test was executed with single rod configuration. The vibration amplitudes of a fuel rod were measured by the laser vibro-meter system in x and y-direction. The analyses results were not closely with the test data, but the trend was very similar with the test result. In fsi coupled analysis case, the turbulent model was very important with the reliability of the accuracy of the analysis model. Therefore, the analysis model will be needed to further study

[en] Thin films of zinc germanate doped with manganese (Zn₂GeO₄:Mn) were fabricated by radio frequency magnetron sputtering, and their structural characteristics and luminescent properties were studied. The Zn₂GeO₄:Mn films exhibited a pronounced absorption edge at around 271 nm and a high optical transparency in the visible wavelength region with a peak transmittance of 0.927 at 691 nm. While the as-deposited Zn₂GeO₄:Mn films had an amorphous structure, the annealed films possessed a rhombohedral polycrystalline structure with a random crystallographic orientation of grains. The broad-band photoluminescence (PL) emission was observed from the annealed Zn₂GeO₄:Mn films. The PL emission spectrum showed a peak maximum at around 537 nm in the green range, which was accounted for by the intrashell transition of 3d⁵ orbital electrons from the ⁴T₁ lowest excitation state to the ⁶A₁ ground state in the divalent manganese ions. Two discrete peaks were observed in the PL excitation spectrum at 256 and 296 nm, which are considered to be associated with the band-to-band absorption of the host and the sub-band absorption from defect states, respectively. The green cathodoluminescence (CL) emission was obtained from the annealed Zn₂GeO₄:Mn films with a peak centered at around 534 nm, analogous to the PL emission spectrum.

[en] The purpose of this project is to independently conduct the performance test of the spacer grids and the cladding material of the 16x16 and 17x17 advanced fuels for Westinghouse type plants, and to improve the relevant test technology. Major works and results of the present research are as follows. 1. The design and structural features of the spacer grids were investigated, especially the finally determined I-spring was thoroughly analyzed in the point of the mechanical damage and characteristic. 2. As for the mechanical tests of the space grids, the characterization, the impact and the fretting wear tests were carried out. The block as well as the in-grid tests were conducted for the spring/dimple characterization, from which a simple method was developed that simulated the boundary conditions of the assembled grid straps. The impact tester was modified and improved to accommodate a full size grid assembly. The impact result showed that the grid assembly fulfilled the design criteria. As for the fretting wear tests, a sliding test under the room temperature air/water, a sliding/impact test under the room temperature air and a sliding/impact tests under the high temperature and pressure environments were carried out. To this end, a high temperature and pressure fretting wear tester was newly developed. The wear characteristic and the resistibility of the advanced grid spring/dimple were analyzed in detail. The test results were verified through comparing those with the test results by the Westinghouse company. 3. The properties and performance of the newly adopted material for the cladding, Low Sn Zirlo was investigated by a room and high temperature tensile tests and a corrosion tests under the environments of 360 .deg. C water, 400 steam and 360 .deg. C 70ppm LiOH. Through the present project, all the test equipment and technologies for the fuel components were procured, which will be used for future domestic development of a new fuel

[en] Primary purpose of the project is to complete a basic design of the power uprating dual-cooled fuel's structural components for an actual use in the existing nuclear power plants. It also includes a basic design of the components of a dual-cooled fuel rod. To this end, during the three years of the first stage (2007.03.∼2010.02.), concepts and technical issues of the structural components such as a supporting structure, guide thimbles and instrumentation tube and the top and bottom end pieces were derived in order to comply with the functional requirements and design criteria of them. Basic design was carried out to resolve the issues by using analytical methods as well as experiments, and observed finally is that a structural compatibility of the designed dual-cooled fuel to the Korean Standard Nuclear Power Plant (OPR-1000). As for the dual-cooled fuel rod's components such as a plenum spring, a spacer and end plugs, a concept of them was established by using the basic dimension and array produced by other sub-projects. In turn, the basic design was completed by using the finite element analysis and conventional mechanical design formulae. Additionally, a welding method and equipment for a dual-cooled fuel rod specimen was also successfully developed to prepare for the irradiation tests at the HANARO. It was shown that a dual-cooed fuel for the OPR-1000 can be designed after manufacturing the partial assembly with the designed components and their drawings. The first stage was completed with passing the Gate checks proposed at the beginning. During the second stage(2010.03.∼2012.02.), researches on the mechanical behavior and structural integrity of the designed dual-cooled fuel will be conducted for preparing a license of it, which should be done when the dual-cooled fuel is commercialized

[en] Analyzed are the tractions induced by the generalized contact configuration and the tilting of the contacting body. The friction energy dissipation from the contact surface differs if the contacting body is tilted and the end profile of it changes. The internal stress is found to move to the direction of the tilting. Therefore, it is thought that a special concern needs to be given during the contact design in the point of tilting (and alignment). From the crack analysis, it is found that the influence of the tilting on the cracking behaviour is negligible. When a bulk tension is applied, however, K_I increases considerably even though the variation of K_II is very small. In that case, K_I increases as the crack length increases. The improvement of contact configuration is taken into consideration as one of the approaches to restrain the contact failure. As for the configurations, a rounded punch (R-punch), a truncated punch (T-punch) and a rounded and truncated punch (RT-punch) are considered. By the R-punch, the slip region is the smallest, and so is its expansion velocity. In the case of partial slip, it is found that the slip region can expand to the location of the peak normal traction. If shear force exceeds further, gross slip immediately occurs in the whole contact area. So, the limit of the shear force is the one by which the location of shear peak reaches that of normal peak to form the partial slip. To restrain the contact failure, especially wear damage, it is required to confine the shear force less than the limit. The wear in water environment is more severe than that in air. This is explained by the size and the dispersion of the wear debris, which is affected by the environmental difference. No oxidation is found on the worn surface. The wear coefficient K of the workrate model is larger in the case of gross slip compared with K of partial slip. The mechanism of fretting wear has been said that it starts from the adhesive wear, then abrasive wear prevails after wear debris is produced. Since this cycle can be accelerated in water due to the ease of the debris dispersion, the severe wear in water may be explained such a way. On the other hand, it is found difficult to say that the wear volume increase rate is always linear to the workrate, which the workrate model implies. It may be influenced by the material difference, the experimental condition (e.g., environment) and the slip regime

[en] A Finite Element (FE) Model was proposed on the partial bundle assembly (5x5) consisted of 21 to 24 dummy rods, 1 to 4 guide tubes and 5 spacer grids. The 3-D model was made by IDEAS modeler first, and then transferred to ABAQUS program to be performed for vibration analysis. It was obtained that the vibration modes of the bundle assembly and each rod in it were separately presented. The beam modes of the partial bundle were appeared from the first mode to the approximately tenth mode at first. After then, dozens of the first vibration modes of the rods came, and then the several beam modes of the bundle followed again. This phenomenon continuously repeated as the natural frequency went high. It was, also, obtained that the results from the single rod analysis were identical to those of each rod extracted from the partial bundle analysis. In addition, it was judged that two guide tubes were proper for 5x5 bundle assembly

[en] For the high performance fuel development research of PWR fuel, a test loop is designed and constructed to evaluate the performances of the spacer grid developed. The test loop is called FIVPET(Flow-Induced Vibration and Pressure drop Evaluation Test loop). The performance test of the space grids will be carried out with the 5x5 rod bundle that consists of 23 dummy rods, 2 guide tubes and 5 spacer grids. In this report, the vibration characteristics of the FIV test loop are investigated by the Finite Element(FE) analysis and the modal test. Also, the supporting performances of the current pipe supports and fixtures are checked by analysis results and improved. For the FE analysis, 3-D beam element is used for the pipes and the test section and mass element used for the valves and flanges. The 'U' restrainer stiffness determined by numerical simulation is used for the FE model. The result of the FE analysis is compared with that of the modal test. The higher mode similarity between the test and analysis is observed in a few low modes. After that, the mode similarity reduce as the mode goes high. It is concluded that the first to the third vibration modes are observed at the lower parts of the 6 inches restoring line, followed by a local mode at the test section, and the natural frequencies of the modes are 22.4 Hz, 26.0 Hz, 27.5 Hz and 31.4 Hz. By adding or changing some supporting conditions, unwanted vibration modes of the loop can be eliminated or restricted

[en] The spacer grid is one of the main structural components in the fuel assembly, Which supports the fuel rods, guides cooling water, and protects the system from an external impact load, such as earthquakes. Therefore, the mechanical and structural properties of the spacer grids must be extensively examined while designing it. In this report, free fall type shock tests on the several kinds of the specimens of the spacer grids were also carried out in order to compare the results among the candidate grids. A free fall carriage on the specimen accomplishes the test. In addition to this, a finite element method for predicting the critical impact strength of the spacer grids is described. FE method on the buckling behavior of the spacer grids are performed for a various array of sizes of the grids considering that the spacer grid is an assembled structure with thin-walled plates and imposing proper boundary conditions by nonlinear dynamic impact analysis using ABAQUS/explicit code. The simulated results results also similarly predicted the local buckling phenomena and were found to give good correspondence with the shock test results

[en] In order to perform the one-sided and the through-grid impact tests for a new developed spacer grid, the drop type impact test machines were established. The dynamic impact test is to get some basic data for accident analysis such as impact strength, stiffness, and coefficient of the restitution. Furthermore, these developed test methods and procedures will be qualified standard for increasing the reliability of the test results. Chapter 2 provides an introduction to the test facilities and instrumentations. Chapter 3 describes on how spacer grid and the single span fuel assembly specimen will be prepared. In addition to this, how to set up these testing machines. Chapter 4 illustrates detail test procedure on how to acquire impact signal of the two kinds of the specimen. Chapter 5 deals with signal processing and analysis for the test data. Finally, chapter 6 summarise the overall test procedure and the test method