Hierarchical zeolite was prepared from natural zeolite using tandem acid-base treatments and applied as adsorbent for Th(IV) removal. Natural zeolite occurred naturally as microporous material. It was modified using two familiar methods simultaneously, dealumination and desilication techniques, to change its micropore size into hierarchical pores. Extensive characterization of both natural and modified zeolites were conducted using XRD, BET, SEM-EDS, and AAS. XRD Patterns of raw, pre-treated , and acid-base tandem modified zeolites show that the modification process has not changed the crystal properties of this material. However, the Si/Al ratio is increased from 6.688 to 11.401 for Na-zeolite (NaZ) and modified zeolite, ZA2B respectively. The surface area is increased from 125.4 m 2 /g (NaZ) to 216.8 m 2 /g (ZA2B), indicative of the creation of mesopore in addition to naturally micropore structure. The application of these zeolite materials as adsorbent were carried out using solution of 50 ppm Th 4+ measured using UV-Vis spectrophotometer. The UV-Vis result shows that the modified zeolite (ca. 10 mg) has higher adsorption capacity than natural zeolite. The adsorption process does not fit into Langmuir and Freundlich isotherm and the adsorption capacity of this material increase from 909 mg/g to 2000 mg/g for NaZ and ZA2B respectively.
DESIGN OF DRY CASK STORAGE FOR SERPONG MULTI PURPOSE REACTOR SPENT NUCLEAR FUEL. The spent nuclear fuel (SNF) from Serpong Multipurpose Reactor, after 100 days storing in the reactor pond, is transferred to water pool interim storage for spent fuel (ISFSF). At present there are a remaining of 245 elements of SNF on the ISSF,198 element of which have been re-exported to the USA. The dry-cask storage allows the SNF, which has already been cooled in the ISSF, to lower its radiation exposure and heat decayat a very low level. Design of the dry cask storage for SNF has been done. Dual purpose of unventilated vertical dry cask was selected among other choices of metal cask, horizontal concrete modules, and modular vaults by taking into account of technical and economical advantages. The designed structure of cask consists of SNF rack canister, inner steel liner, concrete shielding of cask, and outer steel liner. To avoid bimetallic corrosion, the construction material for canister and inner steel liner follows the same material construction of fuel cladding, i.e. the alloy of AlMg2. The construction material of outer steel liner is copper to facilitate the heat transfer from the cask to the atmosphere. The total decay heat is transferred from SNF elements bundle to the atmosphere by a serial of heat transfer resistance for canister wall, inner steel liner, concrete shielding, and outer steel liner respectedly. The rack canister optimum capacity of 34 fuel elements was designed by geometric similarity method basedon SNF position arrangement of 7 x 6 triangular pitch array of fuel elements for prohibiting criticality by spontaneous neutron. The SNF elements are stored vertically on the rack canister. The thickness of concrete wall shielding was calculated by trial and error to give air temperature of 30 oC and radiation dose on the wall surface of outer liner of 200 mrem/h. The SNF elements bundles originate from the existing racks of wet storage, i.e. rack canister no 3, 8 and 10. The value of I0 from the rack no 3, 8 and 10 are 434.307; 446.344; and 442.375 mrem/h respectively. The total heat decay from rack canister no 3,8 and 10 are 179.640 ; 335.2; and 298.551 watts. The result of the trial and error calculation indicates that the rack canister no 3, 8 and 10 need the thickness of concrete shielding of 0.1912, 0.1954 and 0.1940 m respectively.Keywords: heat and radiation decay, spent fuel , storage cask.
Concentrating of solution by evaporation with tubular heating surface evaporator is the effective method for decontamination of radioactive waste. Radioactive matter was concentrate with decontamination factor 104-105 for Cs-137. The evaporation of liquid waste from Serpong Nuclear Facilities having the permanent hardness of CaSO4 and MgSO4 with ratio of 2:1 generates fouling scale. The presence of scale on the evaporator gives the additional cost i.e. increasing of the capital investment cause of oversize of heat transfer surface area, increasing of energy cost for same evaporator capacity due to the presence of fouling heat transfer resistance, the presence of time loosing for maintenance and descaling, the chemical cost for descaling, and decreasing of the production capacity cause of decreasing of production time comparing the condition without the presence of fouling scale. For the problem solution, it is necessary to perform the sequence action starting the prevention of fouling scale formation, than monitoring of the fouling factor (Rd), and finally removing of fouling scale by chemical descaling. The prevention of fouling scale formation is performed by separation of soluble and suspended solid and utilization of chemical inhibitor before evaporation operation. The monitoring of fouling factor is performed during evaporation operation by reading the operating parameter of evaporation on the control panel i.e. mass flow rate of heating steam, mass flow rate of liquid waste, the input and output of steam temperature, and the input and output of liquid waste temperature. The energy for evaporation can be calculated, than the clean and dirty overall heat transfer coefficient can be calculated, so the fouling factor can be obtain. The removing of fouling scale or descaling process is performed by immersion of evaporator circuits using nitric acid solution of 10% weight concentration, and by mechanical brushing during maintenance activity. The prevention, monitoring, and removing of scale fouling on the operation of evaporator is described on the paper.
Kegiatan industri nuklir menimbulkan limbah cair organik seperti limbah detergen dari pencucian pakaian kerja, pelarut 30% TBP (tri-n-butyl phosphate) dalam kerosen dari pemurnian ataupun pengambilan uranium dari gagalan fabrikasi elemen bahan bakar, pelarut yang mengandung D2EHPA (di-2-ethyl hexyl phosphoric acid) dan TOPO (trioctyl phospine oxide) dalam kerosin dari pemurnian asam fosfat. Limbah tersebut bersifat bahan berbahaya dan beracun (B-3) serta radioaktif, oleh karena itu limbah tersebut harus diolah sehingga terjadi detoksifikasi B-3 dan dekontaminasi radionuklidanya. Telah dilakukan penelitian proses oksidasi biokimia pengolahan limbah simulasi cair organik radioaktif dari pencucian pakaian kerja menggunakan campuran bakteri mutan aerob bacillus sp, pseudomonas sp, arthrobacter sp, dan aeromonas sp. Limbah berkadar deterjen 1,496 g/L, aktivitas 10-1Ci/m3, dengan COD (Chemical Oxygen Demand) 128, BOD (Biological Oxygen Demand) 68 dan TSS (Total Suspended Solid) 1000 ppm, diolah dengan oksidasi biokimia dengan penambahan bakteri yang diberi nutrisi nitrogen dan fosfor, dan diaerasi. Hasilnya menunjukkan bahwa bakteri mampu menguraikan detergen menjadi karbon dioksida dan air sehingga memenuhi baku mutu air golongan B dengan kadar BOD dan COD berturut-turut berharga 6 dan 0 ppm, diperlukan waktu penguraian 106 jam untuk pemenuhan baku mutu tersebut. Semakin lama waktu proses memberikan kadar padatan total dalam lumpur semakin besar karena biomassa yang terbentuk dari massa koloni bakteri yang hidup dan mati semakin banyak.
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