Hasil Pencarian  ::  Simpan CSV :: Kembali

"Technetium 99m, yang dihasilkan melalui molybdenum-99, merupakan radioisotop terbanyak digunakan di dunia kedokteran nuklir. Untuk memproduksi molybdenum-99, sekarang ini sedang dikembangkan reaktor nuklir jenis aqueous homogeneous reactor (AHR). Meskipun penelitian terkait AHR telah banyak dilakukan, belum begitu banyak referensi yang membahas tentang aspek materialnya, padahal aspek material merupakan salah satu hal yang penting untuk diperhatikan dalam mendisain AHR. Dalam hal ini, salah satu hal yang perlu untuk diteliti adalah berhubungan dengan integritas struktural bejana AHR yang diakibatkan oleh stress akibat adanya tekanan serta suhu operasi reaktor. Desain dari bejana harus mampu menahan kondisi pengoperasian normal, kondisi kecelakaan atau abnormal yang mungkin, serta mempertimbangkan adanya cacat retak yang mungkin ada pada bejana. Penelitian ini dilakukan melalui simulasi komputer metode finite elemen (FEM) dengan bantuan software ANSYS sedangkan verifikasinya dilakukan secara eksperimental. Akan tetapi, karena kompleksnya permasalahan dalam sebuah reaktor, maka verifikasi hanya dilakukan dengan cara membandingkan hasil uji tarik pada kondisi AHR dengan simulasi uji tarik dengan ANSYS. Hasil uji tarik secara eksperimen dan uji tarik secara simulasi ANSYS menunjukan korelasi yang sangat baik sehingga diasumsikan bahwa simulasi yang dilakukan dapat mewakili kejadian yang sebenarnya. Hasil simulasi pada AHR menunjukan bahwa tekanan dan suhu pada bejana berpengaruh pada stress material bejana. Semakin tinggi tekanan dan suhu pada bejana maka akan semakin tinggi juga stress yang diterima oleh material bejana. Ukuran cacat retak yang disimulasikan pada bejana juga memberikan pengaruh pada nilai stress intensity factor (SIF) yang dihasilkan dimana semakin besar ukuran cacat retak, akan menghasilkan nilai SIF yang juga semakin tinggi. Penggunaan material reflektor juga memberikan pengaruh yang signifikan terhadap stress yang diterima oleh bejana reaktor. Hal ini disebabkan adanya tambahan stress yang berasal dari thermal stress antara material bejana dan juga material reflektor. Dari seluruh simulasi yang dilakukan, nilai equivalent (von-Mises) stress yang dihasilkan masih dibawah nilai yield strength dan fracture toughness (KIC) bejana AHR sehingga integritas bejana masih terjaga dan retak yang ada tidak mengalami propagasi menjadi suatu kegagalan.

---

Technetium-99m, which is generated through a source of decaying molybdenum-99, is the the most commonly used medical radioisotope. To produce molybdenum-99, nuclear reactor types of homogeneous aqueous reactor (AHR) are being developed by many investigators. Although AHRs-related research have been done, yet many references that discuss the aspects of the material are rarely available. At the same time, material is one of important aspects to consider in designing AHR. In this case, one thing that needs to be investigated in relation to the structural integrity of AHR vessels is the stress caused by the pressure and temperature of the reactor operation.

The design of vessels needs to consider many aspects such as normal operating conditions, possibility of accident or abnormal conditions, as well as consideration of the existence of defects that may exist in the vessel. This research was peformed through a computer simulation by using finite element method (FEM) available in ANSYS. The validity of the simulation was then verified experimentally. However, due to the complication of the reactor, verification was just conducted by comparing the experimental results of tensile test at AHR contiditon with the tensile test simulated by using ANSYS.

The results of the experimental tensile test and the tensile test simulated by using ANSYS showed an excellent correlation. In this case, the results of the simulation was assumed to represent the actual event. The simulation results on AHR show that pressure and temperature in the vessel affect the stress of the vessel material. The higher the pressure and temperature in the vessel, the higher the stress of the vessel material. The size of the simulated crack defects in the vessels also affects the value of stress intensity factor (SIF); the greater the crack the higher the SIF value.

The use of reflector material also has a significant influence on the stress experienced by the vessel reactor. This is due to the additional stress from thermal stress between the vessel and reflector materials. However the equivalent (von-Mises) stressess obtained from all of the simulation are still below the yield strength and fracture toughness (KIC) of the AHR vessel so that the integrity of the vessel is maintained and that any existing cracks would not propagate to becomea a failure."

"Penelitian ini bertujuan untuk mendapatkan karakteristik penurunan tekanan pada aliran evaporasi dua fase dengan jenis refrigeran propane (R-290) di pipa konvensional horizontal. Kondisi pengujian menggunakan berbagai variasi pengujian yaitu fluks kalor (q), fluks massa (G) dan nilai temperatur saturasi dengan menggunakan test section yang terbuat dari pipa stanless steel berdiameter 7,6 (mm) dengan panjang 1,07 (m). Refrigeran yang mengalir dipanaskan secara merata di sepanjang pipa test section. Hasil yang didapat adalah penurunan tekanan yang dipengaruhi oleh fluks kalor, fluks massa dan temperatur saturasi. Dari ketiga jenis variasi tersebut akan didapatkan nilai penurunan tekanan yang didapatkan secara eksperimen. Nilai penurunan tekanan ini akan dibandingkan dengan nilai penurunan tekanan yang didapat berdasarkan kalkulasi. Permodelan Homogeneous seperti McAdamas, Cicchitti, dan Dukler serta permodelan Separated seperti Lockhart - Martinelli digunakan sebagai pembanding terhadap penurunan tekanan eksperimen. Hal ini untuk melihat prediksi mana yang paling baik dalam penelitian yang dilakukan.

---

This study aimed to obtain the characteristics of the pressure drop in two - phase flow with evaporating refrigeran types of propane (R - 290) in the conventional horizontal pipe . Test conditions using a variety of tests that heat flux (q) , mass flux (G) and the saturation temperature values using a test section made of stanless steel pipe diameter 7.6 (mm) with a length of 1.07 (m). Refrigeran flowing heated evenly along the pipe test section . The result is that the pressure drop is influenced by the heat flux , mass flux and saturation temperature. From three types of variations will be obtained pressure values obtained experimentally. The pressure drop values will be compared with the value obtained by the pressure drop calculations. Modeling Homogeneous like McAdamas, Cicchitti, and Dukler and modeling Separated like Lockhart - Martinelli used as a comparison against the experimental pressure drop. It is to see where the best prediction of the research undertaken."

"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."

"In this paper, the problem of hydromagnetic convective flow along a semi-circular enclosure filled with nanofluidsusing a two-dimensionalnon-homogeneous model have been studied numerically.The circular wall of the enclosureis maintained at constant cold temperature whereas various combinations of the thermal boundary conditions at the bottom heated wall are considered. The enclosureis permeated by an inclined uniform magnetic field and the effects of gravity, Brownian motion and thermophoresis are incorporated into the nanofluid model. In the numerical simulation, here isconsidered water, kerosene as basefluids and Cobalt34, Fe Oas nanoparticles. The Galerkin weighted residual finite element method has been employed to solve the governing partial differential equations after converting them into a non-dimensional form using a suitable transformation of variables. The effects of various parameters such as Hartmann numberandRayleigh number on isotherms have been displayed graphically for 34Fe O -waternanofluid. The heat transfer augmentation for various thermal boundary conditions hasbeen done from the bottom heated wall for 34Fe O -waterandCobalt-kerosenenanofluid. The results show that the heat transfer rate can be decreased with the increasing values of the Hartmann number but it can be increased by increasing the Rayleigh number. The obtained numerical results also indicate that the variable thermal boundary conditions have significant effects on the flow and thermal fields. Finally, it is observed that the heat transfer rate is higher for Cobalt-kerosenenanofluid than for 34Fe O -waternanofluid. "

"The present study investigates the aqueous stability of polyethylene glycol and oleic acid- based anionic surfactants through the dynamic light scattering (DLS) and zeta potential methods, for application in enhanced oil recovery (EOR). Polyethylene glycol dioleate sulfonate (PDOS) surfactant solutions were prepared in concentrations of 0.05, 0.1, 0.3, 0.5, and 1 wt% in deionized water. Aqueous stability of PDOS was assessed by measuring the droplet size over five days, using nano particle analyzer HORIBA SZ-100 at 25oC. Results show that good aqueous stability of PDOS was achieved at concentrations of 0.1 to 1 wt%, but with the droplet size becoming unstable at the lowest concentration of 0.05 wt%. The polydispersity indices were classified into polydisperse distribution type recorded as 0.3 to 0.5 at concentrations of 0.05 and 0.1 wt% and 0.2 at concentrations of 0.3 to 1 wt%. The critical micelle concentration (CMC) of PDOS was 0.3% and the interfacial tension of PDOS surfactant above the CMC was around 10-3 dyn/cm. The zeta potential of PDOS surfactant without the addition of salt in concentrations of 0.05, 0.1, 0.3, 0.5, and 1 wt% was highly stable up to -96.8, -90.5, -89.6, -82.3, and -64.4 mV, respectively. With the addition of salt they were moderately stable at a concentration of 1 wt%. The conductivity increased with increasing concentration. The zeta potential of PDOS with the addition of salt was moderately stable in a concentration of 1%. Although PDOS with concentration of 0.05% showed a high value of zeta potential with the addition of salt, there is no guarantee that the PDOS surfactant solution will be stable for five days."

"ABSTRAKFitness For Service (FFS) Assessments adalah teknik evaluasi kuantitatif untuk menentukan apakah suatu equipment/peralatan bisa beroprasi secara aman dalam kurun waktu tertentu[1], yang merupakan suatu penetapan dan langkah penaksiran terhadap suatu system berdasarkan Standard/CODE yang telah disepakati sebagai acuan (API 579-1 /ASME FFS-1). Dan jenis pressure vessel yang mengalami aging, lebih beresiko terhadap semua jenis kerusakan, maka perlu dilakukan jenis analisa kelayakan tertentu untuk memastikan kemampuan dan kelayakan alat tersebut.PV Elite adalah aplikasi desain yang di gunakan dan diakui secara internasional untuk analisa desain struktur menara proses dan Vessel horizontal/vertikal, seperti menganalisa ketebalan dinding untuk head, shell dan cone, ukuran komponen untuk kombinasi tekanan yang tepat (internal dan eksternal), berat mati (kondisi berdiri, operasi dan tes hidrostatik), serta beban angin dan seismik berdasarkan pada Code yang berlaku secara internasional[2]. Aplikasi ini akan menampilkan resume dari desain (dalam hal ini kondisi aktual) mengikuti kondisi operasi.Pada penelitian ini semua jenis bejana tekan (pressure vessel) memenuhi kriteria API 579/ASME FFS-1, dan memiliki remaining life yang baik (berkisar antara 9,6 sampai 232 tahun) juga nilai MAWP (Máximum Allowable Working Pressure) melebihi MAWPrequirement, penggunaan software PV Elite mampu menunjukkan detail dari equipment dalam bentuk 3D, namun gagal menggambarkan bentuk heat exchangger dalam model shellbox.

---

ABSTRACT

Fitness For Service (FFS) Assessments is the technique of quantitative evaluation to determine whether an equipment / appliances can all operating safely within a certain time [1], which is a determination and step assessment to a system based on the Standard / CODE has been agreed as a reference ( API 579-1 / ASME FFS-1). And the type of pressure vessel which is experiencing aging, more at risk of all kinds of damage, it is necessary to a certain kind of feasibility analysis to ensure the capability and feasibility of such a device.

PV Elite is a design application that is in use and internationally recognized for the analysis of the design of the tower structure process and vessel horizontally/vertically, as analyzing the thickness of the wall for the head, shell and cone, component size for the combination of proper pressure (internal and external), dead weight (condition stand up, operating and hydrostatic test), as well as wind and seismic loads based on internationally accepted CODE [2]. This application will display the resume of the design (in this case the actual conditions) to follow the operating conditions.

In this study all kinds of pressure vessel (pressure vessel) meets the criteria of API 579 / ASME FFS-1, and has a good life remaining (ranging from 9.6 up to 232 years) is also worth MAWP (Maximum Allowable Working Pressure) exceeds MAWPrequirement, use PV Elite software is able to show the detail of equipment in 3D, but failed to describe the form of heat exchanger in shellbox models."