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Abstrak :
Ketergantungan yang tinggi pada sumber energi fossil, masih menjadi permasalahan utama penyediaan energi nasional. Penyediaan energi primer nasional dipenuhi dari batubara, minyak bumi dan gas bumi, dan sektor transportasi merupakan pengguna energi energi bahan bakar minyak (BBM) terbesar di Indonesia. Guna mengatasi permasalahan tersebut, pemerintah mendorong diversifikasi bahan bakar di sektor transportasi, antara lain dengan penggunaan bahan bakar nabati (BBN). Salah satu bahan bakar alternatif yang dapat digunakan untuk mengurangi dan menggantikan penggunaan bahan bakar fosil adalah biodiesel. Sebagai bahan bakar alternatif, biodiesel masih memiliki kendala dalam pemanfaatannya. Biodiesel sangat rentan terhadap oksidasi dan juga memiliki ikatan asam lemak jenuh yang sangat rentan terhadap pembekuan kristal dalam suhu kamar. Oksidasi ini akan menyebabkan terjadinya pembentukan gum, deposit, dan sedimen yang dapat meningkatkan viskositas dan menyebabkan penurunan kualitas bahan bakar. Biodiesel lebih sensitif dibandingkan dengan minyak solar terhadap temperatur rendah yang dimana lebih mudah membeku atau pembentukan kristal yang dapat membuat filter tersumbat. Kegagalan fungsi utama filter tersebut merupakan suatu akibat dari adanya kontaminan dan komponen penyumbat filter seperti kelompok glycerin (monoglycerin, diglycerin, trigliceryn), air, sodium/soap, polimer, dan mikroba. Oleh karena itu, diperlukan studi untuk mengetahui pertumbuhan kontaminan dan pengaruhnya terhadap karakterisktik campuran biodiesel di dalam tangki. Uji presipitasi dilakukan pada campuran biodiesel B30 pada tangki kapal selama 30 hari dengan pengambilan sampel tiap dua hari sekali. Densitas, viskositas kinematik, cleanliness, dan water content juga diujikan dalam penelitian ini. Berdasarkan hasil uji presipitasi, didapatkan adanya peningkatan kontaminan sebesar 382% selama 30 hari penyimpanan. Hasil uji cleanliness menunjukan bahwa bahan bakar tersebut tidak memenuhi standar Worldwide Fuels Charter. Hasil pengujian densitas cenderung konstan pada angka 835 gr/cm3 dan viskositas kinematik pada angka 3,35 mm2/s. Nilai water content juga masih berada di bawah ambang batas. Pengujian menunjukan bahwa waktu penyimpanan tidak berpengaruh pada karaktersitik bahan bakar seperti denistas, viskositas kinematik, dan water content. ...... High dependence on fossil energy sources is still a major problem in national energy supply. National primary energy supply is met from coal, oil and natural gas, and the transportation sector is the largest user of energy from fuel oil (BBM) in Indonesia. In order to overcome these problems, the government is encouraging diversification of fuels in the transportation sector, including the use of biofuels (BBN). One alternative fuel that can be used to reduce and replace the use of fossil fuels is biodiesel. As an alternative fuel, biodiesel still has problems in its utilization. Biodiesel is very susceptible to oxidation and also has saturated fatty acid bonds which are very susceptible to freezing crystals at room temperature. This oxidation will cause the formation of gums, deposits, and sediments which can increase the viscosity and cause a decrease in fuel quality. Biodiesel is more sensitive than diesel oil to low temperatures where it freezes more easily or crystals form which can clog filters. The main function failure of the filter is a result of the presence of contaminants and filter plug components such as glycerin groups (monoglycerin, diglycerin, triglyceryn), water, sodium/soap, polymers, and microbes. Therefore, a study is needed to determine the growth of contaminants and their effect on the characteristics of the biodiesel mixture in the tank. The precipitation test was carried out on the B30 biodiesel mixture in the ship's tank for 30 days with sampling every other day. Density, kinematic viscosity, cleanliness, and water content were also tested in this study. Based on the results of the precipitation test, it was found that there was an increase in contaminants of 382% during 30 days of storage. The cleanliness test results show that the fuel does not meet the Worldwide Fuels Charter standards. Density test results tend to be constant at 835 gr/cm3 and kinematic viscosity at 3.35 mm2/s. The water content value is still below the threshold. Tests show that storage time has no effect on fuel characteristics such as density, kinematic viscosity, and water content.

Abstrak :
[ABSTRAK
Limbah Bahan Bakar Nuklir Bekas (BBNB) merupakan salah satu limbah yang dihasilkan dalam pengoperasian reaktor nuklir. Limbah ini masih menghasilkan produk fisi dan panas hasil reaksi yang masih tinggi sehingga perlu dikelola dengan baik agar efek radiasi yang ditimbulkan tidak keluar di lingkungan. Penelitian ini akan dilakukan pemodelan panas peluruhan pada penyimpanan kering BBNB bentuk pebble dengan tipe storage tank yang telah digunakan pada reaktor HTR 10 menggunakan software ORIGEN-ARP. Dengan computational fluid dynamics (CFD) menggunakan Comsol Multiphysics maka pengaruh kecepatan udara pendingin dan ketebalan lapisan pengungkung terhadap profil suhu di setiap segmen storage dapat diketahui sehingga keselamatan penyimpanan BBNB pada aspek suhu dapat dianalisis. Dari hasil perhitungan dapat diketahui bahwa panas peluruhan yang dihasilkan oleh BBNB setelah keluar dari reaktor sebesar 620,2260 watt. Panas peluruhan tersebut semakin menurun seiring dengan lamanya waktu penyimpanan. Ketebalan beton tidak terlalu berpengaruh terhadap penurunan suhu di storage tank. Hal ini disebabkan oleh konduktivitas panas beton yang rendah sehingga laju perpindahan panas di setiap variasi ketebalan tidak berbeda secara signifikan. Ketebalan stainless steel berpengaruh terhadap gradien perubahan suhu pada storage tank. Semakin tipis stainless steel maka semakin banyak laju panas yang dialirkan dari grafit ke beton, sehingga suhu pada beton semakin besar. Semua hasil simulasi pada berbagai kondisi memenuhi syarat parameter suhu maksimum keselamatan.

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ABSTRACT Nuclear Fuel Waste is one of waste generated in operation of nuclear reactors. This waste is still producing fission products and heat of reaction that need to be managed properly so the effects of radiation emitted do not expose to environment. This research will be carried out modeling the decay heat in dry storage of pebble nuclear spent fuel with the type of storage tanks that have been used in the reactor HTR 10 using ORIGEN-ARP software. The effects of cooling air velocity and confinement layer thickness on temperature profile in every segment of storage can be determined with computational fluid dynamics (CFD) using Comsol Multiphysics so the safety of nuclear spent fuel storage on temperature aspects can be analyzed. Based on the calculation results can be seen that the decay heat generated by nuclear spent fuel after coming out from the reactor is 620.2260 watts. The decay heat decreases as the length of storage time. Concrete thickness does not significantly affect the declining temperature gradient in the storage tank. This is caused by the low thermal conductivity of concrete so the heat transfer rate in each variation of thickness is not different significantly. Stainless steel thickness affects the declining temperature gradient. Thinner the thickness of the stainless steel is used, greater the reduction of temperature gradient so equilibrium temperature of storage tank can be quickly achieved. All simulation results under various conditions compliy with the maximum temperature parameters of safety.;Nuclear Fuel Waste is one of waste generated in operation of nuclear reactors. This waste is still producing fission products and heat of reaction that need to be managed properly so the effects of radiation emitted do not expose to environment. This research will be carried out modeling the decay heat in dry storage of pebble nuclear spent fuel with the type of storage tanks that have been used in the reactor HTR 10 using ORIGEN-ARP software. The effects of cooling air velocity and confinement layer thickness on temperature profile in every segment of storage can be determined with computational fluid dynamics (CFD) using Comsol Multiphysics so the safety of nuclear spent fuel storage on temperature aspects can be analyzed. Based on the calculation results can be seen that the decay heat generated by nuclear spent fuel after coming out from the reactor is 620.2260 watts. The decay heat decreases as the length of storage time. Concrete thickness does not significantly affect the declining temperature gradient in the storage tank. This is caused by the low thermal conductivity of concrete so the heat transfer rate in each variation of thickness is not different significantly. Stainless steel thickness affects the declining temperature gradient. Thinner the thickness of the stainless steel is used, greater the reduction of temperature gradient so equilibrium temperature of storage tank can be quickly achieved. All simulation results under various conditions compliy with the maximum temperature parameters of safety., Nuclear Fuel Waste is one of waste generated in operation of nuclear reactors. This waste is still producing fission products and heat of reaction that need to be managed properly so the effects of radiation emitted do not expose to environment. This research will be carried out modeling the decay heat in dry storage of pebble nuclear spent fuel with the type of storage tanks that have been used in the reactor HTR 10 using ORIGEN-ARP software. The effects of cooling air velocity and confinement layer thickness on temperature profile in every segment of storage can be determined with computational fluid dynamics (CFD) using Comsol Multiphysics so the safety of nuclear spent fuel storage on temperature aspects can be analyzed. Based on the calculation results can be seen that the decay heat generated by nuclear spent fuel after coming out from the reactor is 620.2260 watts. The decay heat decreases as the length of storage time. Concrete thickness does not significantly affect the declining temperature gradient in the storage tank. This is caused by the low thermal conductivity of concrete so the heat transfer rate in each variation of thickness is not different significantly. Stainless steel thickness affects the declining temperature gradient. Thinner the thickness of the stainless steel is used, greater the reduction of temperature gradient so equilibrium temperature of storage tank can be quickly achieved. All simulation results under various conditions compliy with the maximum temperature parameters of safety.]