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"The Fukushima accident resulted in the melting of the reactor core due to loss of supply of coolant when the reactor stopped from operating conditions. The earthquake and tsunami caused loss of electricity due to the flooding that occurred in the reactor. The absence of the coolant supply after reactor shutdown resulted in heat accumulation, causing the temperature of the fuel to rise beyond its melting point. In the early stages of the accident, operator could not determine the severity of the accident and the percentage of the reactor core damaged. The available data was based on the radiation exposure in the environment that was reported by the authorities. The aim of this paper is to determine the severity of the conditions in the reactor core based on the radiation doses measured in the environment. The method is performed by backward counting based on the measuring radiation exposure and radionuclides releases source term. The calculation was performed by using the PC-COSYMA code. The results showed that the core damage fraction at Dai-ichi Unit 1 was 70%, and the resulting individual effective dose in the exclusion area is 401 mSv, while the core damage fraction at Unit 2 was 30%, and the resulting individual effective dose was 99.1 mSv, while for Unit 3, the core damage fraction was 25% for an individual effective dose of 92.2 mSv. The differences between the results of the calculation for estimation of core damage proposed in this paper with the previously reported results is probably caused by the applied model for assessment, differences in postulations and assumptions, and the incompleteness of the input data. This difference could be reduced by performing calculations and simulations for more varied assumptions and postulations."

"Gamma Valerolactone (GVL) merupakan senyawa organik turunan dari asam levulinat yang memiliki banyak kegunaan, salah satunya adalah sebagai aditif bahan bakar. Penelitian ini difokuskan pada perancangan reaktor unggkun trickle skala komersial untuk sintesis GVL dari asam levulinat pada katalis Ru/C. Pemodelan matematis yang digunakan adalah model reaktor unggun trickle aksisimetri dua dimensi untuk perpindahan massa dan momentum di celah unggun, aksisimetri dua dimensi untuk perpindahan energi di dalam unggun, dan satu dimensi untuk perpindahan massa dan di partikel katalis. Tujuan dari penelitian ini adalah mendapatkan desain reaktor dengan volume paling kecil untuk produksi GVL sebanyak 1.239 ton. Desain reaktor dilakukan melalui simulasi pada COMSOL Multiphysics 5.5, dengan mengubah parameter operasi berupa suhu, tekanan, GHSV, LHSV, dan diameter katalis, sehingga didapatkan kondisi optimal pada masing-masing parameter. Hasilnya, didapatkan parameter operasi optimal dengan suhu 423 K, tekanan 25 bar, GHSV 0.065 s-1, LHSV 0.00117 s-1, diameter katalis 3 mm, diameter reaktor 5 cm, dan panjang reaktor 5 m. Laju alir yang dihasilkan dari reaktor skala komersial dengan kondisi optimal adalah 7.06 kg/hari, sehingga diperlukan 536 buah tube untuk memperoleh kapasitas produksi sebanyak 1.239 ton.

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Gamma Valerolactone (GVL) is an organic compound derived from levulinic acid that has many uses, one of which is as a fuel additive. This research is focused on designing a commercial scale trickle bed reactor for the synthesis of GVL from levulinic acid on a Ru/C catalyst. The mathematical modelling used is a two-dimensional axisymmetric trickle bed reactor model for mass and momentum transfer in the bed gap, two-dimensional axisymmetric for energy transfer in the bed, and one-dimensional for mass transfer and in the catalyst particles. The objective of this research is to obtain a reactor design with the smallest volume to produce 1,239 tons of GVL. The reactor design was carried out through simulations on COMSOL Multiphysics 5.5, by changing the operating parameters such as temperature, pressure, GHSV, LHSV, and catalyst diameter, so that optimal conditions were obtained for each parameter. As a result, the optimal operating parameters were obtained with temperature 423 K, pressure 25 bar, GHSV 0.065 s-1, LHSV 0.00117 s-1, catalyst diameter 3 mm, reactor diameter 5 cm, and reactor length 5 m. The flow rate produced from a commercial scale reactor with optimal conditions is 7,06 kg/day, so 536 tubes are needed to obtain a production capacity of 1,239 tons."