No abstract

ABSTRAK PERBANDINGAN DENSITAS PELET UO2 HASIL PELETISASI MENGGUNAKAN SERBUK DAN MIKROSPIR UO2.Telah dilakukan pengembangan proses peletisasi menggunakan mikrospir UO2 sebagai pengganti serbuk UO2. Mikrospir bersifat speris, free flowing, porus dengan kekerasan tertentu (soft particle). Keunggulan penggunaan mikrospir pada proses peletisasi adalah tidak menimbulkan debu saat kompaksi dan lebih efektif dalam pengepakan sehingga tidak membutuhkan proses granulasi dan pelumas padat. Dihipotesakan bahwa penggunaan mikrospir UO2 dalam proses peletisasi akan memberikan densitas pelet sinter yang lebih tinggi dibandingkan dengan penggunaan serbuk UO2 pada parameter proses peletisasi yang sama. Mikrospir UO2 yang digunakan pada peletisasi ini berukuran 900 µm dan crushing strength 2,0 N/partikel , sedangkan serbuk UO2 yang digunakan berukuran antara 150-850 µm. Proses peletisasi mikrospir UO2 dan serbuk UO2 dilakukan dengan memvariasikan tekanan kompaksi antara 200 Mpa hingga 500 MPa dan disinter pada temperatur 1100 °C selama 6 jam dalam suasana campuran gas hidrogen dan nitrogen. Karakterisasi dilakukan pada pelet mentah dan pelet sinter mikrospir UO2 dan serbuk UO2 yang meliputi pengukuran dimensi, penimbangan berat dan pengukuran densitas. Pada variasi tekanan kompaksi diperoleh pelet mentah dan pelet sinter mikrospir UO2 dengan densitas lebih tinggi dibandingkan hasil peletisasi serbuk UO2. Diperoleh hasil bahwa densitas pelet mentah baik hasil kompaksi serbuk UO2 maupun mikrospir UO2 meningkat dengan bertambahnya tekanan kompaksi. Densitas pelet mentah mikrospir UO2 berkisar antara 82,1 -84,2 %TD. Pada kondisi penyinteran yang sama, baik kompakan serbuk UO2 maupun kompakan mikrospir UO2 memperlihatkan densitas meningkat dengan semakin besar tekanan proses kompaksi. Dari penelitian ini belum diperoleh pelet sinter UO2 dengan densitas sesuai persyaratan reaktor pengguna sehingga diperlukan penelitian lanjutan terkait parameter proses peletisasi dan spesifikasi mikrospir UO2 yang efektif dalam memberikan pelet sinter UO2 dengan densitas sesuai persyaratan.Kata kunci: peletisasi, UO2, mikrospir, serbuk, densitas.

coarser quartz particles, incompletely dissolved during firing and so enhancing the compressive stresses in the glassy Hardness and fracture toughness measurements are matrix. Indirect evidence comes from X-ray measurements reported for individual phases and interfacial composof the quartz d spacing8 implying a corresponding residual ites present in fired specimens of an Ecuadorian clay tensile stress in the quartz. However the strengthening is mineral. Each investigation used a half disc from only thought to be effective within a narrow range of quartz strength tests previously done and reported elsewhere.particle sizes, variously suggested to be between 2 and T he aim was to rationalise trends in the macroscopic 30 mm,8-13 and in quantities below 35%.14 Large quartz strength and density to quantify contributions from the particles appear to have a deleterious effect on the important components of the microstructure. T his was strength;8,14 Kobayashi et al.15 found the only identifiable achieved through application of an etching and gold fracture origins on fracture surfaces to be within quartz coating procedure prior to microindentation testing.grains. T he coating technique improved the clarity of theTo summarise, in those natural clays which contain both indents and made the diagonal and radial crack kaolinite and quartz, the first requirement for high strength measurements more accurate. T wo peaks in the strength is sufficient vitrification to substantially eliminate porosity, versus firing temperature curve are shown to arise from after which two separate but not conflicting mechanisms opposite trends in the toughness of the quartz grains may contribute to strengthening the kaolinite based matrix, and the matrix phase, together with a non-linear build their relative importance depending strongly on the size up of the volume of interfacial composite material which and amount of the quartz constituent. confines any cracks initiated in the residual quartzIn the work reported in the present paper the fired crystals at high firing temperatures.BCT /374 properties of a commercial Ecuadorian clay mineral, designated C1, with the composition 30% potassium feldspar, At the time the work was carried out the authors were 30% kaolin, and 30% quartz, have been studied. A firing in the Department of Industrial T echnology, University equation for this material has previously been derived16,17 of Bradford,

DIP-COATING PROCESS OF ZIRCALOY-2 FUEL CLADDING WITH COLLOIDAL GRAPHITE.The intensive researchs on high discharge burn-up of Light Water Reactor (LWR) fuel element have been continously performed due to the extension of fuel element's utility life. One of these researches was allowing for alteration of the existing zirconium-based clad system through coating. A coating technique with the coating layer thickness of 10 -30 µm will improve the corrosion resistance of cladding without changing the dimension of cladding. The scope of this current research is to obtain the zircaloy-2 cladding coated with ZrC layer by dipping process of zircaloy-2 specimens in colloidal graphite at room temperature. The dip-coated specimens undergo heating process at 700 o C, 900 o C and 1100 o C respectively in Argon gas atmosphere for 1 hour and are subsequently characterized by optical microscope and XRD. The optical microscope images show that the coating layers thickness are increased as the heating temperature increased. The coating layers thickness are 10 μm, 20 -40 μm and 100 μm for the specimens heated at 700 o C, 900 o C and 1100 o C respectively. The calculated diffusivity of carbon into zircaloy-2 cladding for the coated specimens at 700 o C, 900 o C and 1100 o C are 3,10216E-11 cm 2 s -1 ; 3,60479E-11 cm 2 s -1 and 4,00613E-11 cm 2 s -1 respectively. From XRD examination analysis reveals that the ZrC phase appears in the specimens heated at 1100 o C but it is not the case for specimens heated at both 700 o C and 900 o C. The coating layer of specimens heated at both 700 o C and 900 o C mostly consists of carbon. At these heating temperatures, carbon atoms have diffused into zircaloy-2 and substituted the zirconium atoms with a limited occupation to form C-Zr solid solution. At the temperature of 1100 o C, due to the increase in vibration energy, the carbon atoms have enough energy to diffuse to form the carbide phase. Heating process at higher than 700 o C, however, will degrade the zircaloy-2 cladding.. It is concluded that the dip-coating process of zircaloy-2 cladding in graphite colloid with subsequent high temperature heating is not the proper method to gain the ZrC-coated zircaloy-2 cladding. Therefore, as for the future works of this research, the others method should be searched and investigated to obtain the proper ZrC coating process on LWR zircaloy cladding which fulfills the dimension and quality requirements.