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Abstrak :
[ABSTRAK
Degradasi sifat mekanik zirkaloi-4 sebagai kelongsong bahan bakar nuklir akibat interaksinya dengan hidrogen tidak bisa dihindari bahkan selama periode operasi normal reaktor. Penelitian ini mengidentifikasi fasa hidrida dengan mengkondisikan zirkaloi-4 berada pada lingkungan hidrogen (hidrogenasi) pada beberapa tingkatan suhu serta efeknya terhadap zirkaloi-4 berdasarkan perubahan mikrostruktur dan sifat mekanik. Potongan material kelongsong bahan bakar nuklir berbasis zirkaloi-4 pra iradiasi digunakan dalam penelitian ini. Karakterisasi sebelum proses hidrogenasi meliputi massa,komposisi,fasa, mikrostruktur dan kekerasan mikro dilakukan sebagai data awal. Potongan material zirkaloi-4 dipanaskan pada beberapa tingkatan suhu, antara lain 3500C, 5000C, 5500C dan 6000C selama 2 jam sebelum dihidrogenasi dengan tekanan mencapai 1200 mbar selama kurang lebih 2 jam. Hasil perhitungan yang diplot pada diagram Pressure-Composition-Isotherm (PCI) menunjukkan bahwa penyerapan hidrogen pada suhu 3500C sebesar 0,17 persen berat dan mencapai nilai 0,74 persen berat pada suhu 6000C. Hal ini dikonfirmasi dengan ONH Analyzer yang mengukur kandungan hidrogen dalam rentang 10 ppm pada 3500C dan 1357 ppm pada 6000C. Keberadaan hidrogen dalam zirkaloi-4 terdeteksi pada munculnya puncak lemah δ-hydride pada identifikasi material uji yang dihidrogenasi pada suhu 6000C dan perubahan mikrostruktur yang memunculkan pertumbuhan struktur yang tampak seperti jarum pada setiap kenaikan suhu hidrogenasi. Kekerasan mikro pada pemanasan tanpa hidrogenasi pada suhu 6000C bernilai 150,66 HV sedikit dibawah nilai kekerasan pada material uji tanpa perlakuan yang bernilai 155,14 HV, sedangkan nilai kekerasan pada material uji yang dihidrogenasi pada suhu 6000C mengalami kenaikan cukup signifikan yang mencapai 194,04 HV sehingga pada kondisi awal LOCA, degradasi sifat mekanik akibat pengaruh hidrogen memerlukan evaluasi menyeluruh terkait dengan keselamatan operasi reaktor nuklir.

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ABSTRACT
Degradation of zircaloy-4 mechanical properties as nuclear fuel cladding due to its interaction with hydrogen during reactor normal operation is inevitable. This experiment identifies hydrides phase after gaseous hydriding at elevated temperature and its effect based on microstructure and mechanical properties evolution. Characterization before hydrogenation process include mass, composition, phase, microstructure and microhardness performed as the initial data. The unirradiated zircaloy-4 cladding materials were annealed 3500C, 5000C, 5500C and 6000C for couple hours before hydrided under hydrogen pressure until 1200 mbar for couple hours too. Calculation results are plotted on the Pressure-Composition-Isotherm (PCI) diagram that shows the hydrogen absorption only 0,17 %wt at 3500C and reach a 0.74 %wt at 6000C. This result is confirmed by the ONH Analyzer that measures the hydrogen content in the range of 10 ppm at 3500C and 1357 ppm at 6000C. Observation using X-Ray Diffractometer shows very weak of δ-hydride peaks based on fitting with hydride database. The optical microscope and scanning electron microscope confirms the presence of hydrides by describing the growth of needle-like as the increase in temperature. Results of microhardness test on annealed zircaloy-4 at 6000C without hydrogen have value about 150,66 HV, lower than as received material (155,14 HV), but material microhardness start to increase from the hydriding at 3500C and reach a significant increase when hydriding at 6000C (194,04 HV). Based on the data that shown in this study indicate that under early LOCA condition, degradation of mechanical properties due to the influence of hydrogen requires a evaluation related to the safety of nuclear reactors operation., Degradation of zircaloy-4 mechanical properties as nuclear fuel cladding due to its interaction with hydrogen during reactor normal operation is inevitable. This experiment identifies hydrides phase after gaseous hydriding at elevated temperature and its effect based on microstructure and mechanical properties evolution. Characterization before hydrogenation process include mass, composition, phase, microstructure and microhardness performed as the initial data. The unirradiated zircaloy-4 cladding materials were annealed 3500C, 5000C, 5500C and 6000C for couple hours before hydrided under hydrogen pressure until 1200 mbar for couple hours too. Calculation results are plotted on the Pressure-Composition-Isotherm (PCI) diagram that shows the hydrogen absorption only 0,17 %wt at 3500C and reach a 0.74 %wt at 6000C. This result is confirmed by the ONH Analyzer that measures the hydrogen content in the range of 10 ppm at 3500C and 1357 ppm at 6000C. Observation using X-Ray Diffractometer shows very weak of δ-hydride peaks based on fitting with hydride database. The optical microscope and scanning electron microscope confirms the presence of hydrides by describing the growth of needle-like as the increase in temperature. Results of microhardness test on annealed zircaloy-4 at 6000C without hydrogen have value about 150,66 HV, lower than as received material (155,14 HV), but material microhardness start to increase from the hydriding at 3500C and reach a significant increase when hydriding at 6000C (194,04 HV). Based on the data that shown in this study indicate that under early LOCA condition, degradation of mechanical properties due to the influence of hydrogen requires a evaluation related to the safety of nuclear reactors operation.]

Abstrak :
Reaktor Riset Nuklir dengan air ringan sebagai zat pendingin memiliki sistem pendingin yang dilengkapi dengan komponen kamar tunda. Fungsi ruang tunda adalah untuk menunda aliran agar gas hasil reaksi fisi khususnya Nitrogen-16 (N-16) dapat meluruh pada ambang batas yang diizinkan. Gas tersebut akan menumpuk pada bagian atas kamar tunda yang diduga sebagai sebab terjadinya shutdown operasi reaktor karena sinyal Loss Of Coolant Accident (LOCA). Tujuan dari penelitian ini adalah mengetahui performa dari kamar tunda. Performa yang ingin di kaji meliputi lama waktu aliran didalam kamar tunda, serta perubahan hilang tekan terhadap penumpukan gas didalamnya. Computations fluid dynamics (CFD) menggunakan metode particle tracking pada model skala kamar tunda dilakukan untuk mengetahui lama waktu tinggal aliran. Metode pengujian eksperimen dengan membuat model skala uji digunakan untuk melihat fenomena variasi rasio udara terjebak terhadap perubahan hilang tekan pada kamar tunda. Hasil simulasi model skala menunjukkan waktu tinggal aliran selama 15,6 detik dan divalidasi dengan persamaan skala yang dilakukan dan didapatkan error sebesar 10,09%. Meningkatnya rasio udara terjebak didalam kamar tunda sebanding dengan kenaikan hilang tekan didalamnya. Kenaikan hilang tekan kamar tunda mulai mempengaruhi sistem pada rasio udara terjebak sebesar 12%, dimana terlihat pembentukan buble dan laapisan udara di bawah sekat 1 serta adanya void yang terbentuk pada outlet. ......The Nuclear Research Reaktor with light water as a coolant has a cooling system equipped with a delay chamber component. The function of the delay chamber is to delay the flow so that the fission gas can decay at the permissible threshold, especially Nitrogen-16 (N-16). The gas will accumulate at the top of the delay chamber that suspects to activate the Loss Of Coolant Accident (LOCA) signal and shut down the reaktor. The purpose of this study was to determine the performance of the decay chamber. Performances of the delay chamber are the residence time of the flow inside the delay chamber and the change of pressure drop due to gas accumulation inside. The delay chamber scaled model simulation has been carried out. Computations fluid dynamics (CFD) using the particle tracking method carried out to determine the residence time of the flow. The experimental test scale model is used to see the relationship between trapped air and pressure drop inside the delay chamber. The CFD scale model simulation results that the residence time of the flow is 15.6 seconds. the result is validated by the scale equation and an error of 10.09% is obtained. An increase in the ratio of trapped air causes an increase in pressure drop between the inlet and outlet. The increase in pressure loss inside the delay chamber began to affect the system at a 12% trapped air ratio. The experiment has shown the formation of bubbles and air layers inside the delay chamber and the presence of voids formed at the outlet.