PENGARUH ADITIF UREA DAN HMTA SERTA TEMPERATUR DAN WAKTU REDUKSI TEHADAP SPESIFIKASI KERNEL UO2

ABSTRAK PENGARUH ADITIF UREA DAN HMTA SERTA TEMPERATUR DAN WAKTU REDUKSI TERHADAP SPESIFIKASI KERNEL UO2. Pengaruh aditif urea dan heksa metilen tetra amin (HMTA) serta temperatur dan waktu reduksi terhadap spesifikasi kernel UO2 telah dipelajari. Kernel UO2 dibuat dengan proses total gelasi uranium (TGU). Sebagai bahan dasar digunakan uranil nitrat, urea, HMTA, polivinil alkohol (PVA) dan tetra hidro furfural (THF). Pertama kali dibuat 20 ml larutan campuran uranil nitrat 1M, urea divariasi 1-2 M, 1,6 g PVA, THF 2 M dan air. Sambil diaduk dan dipanaskan pada temperatur 70oC selama 20 menit sampai terbentuk larutan homogen. Setelah itu, larutan didiamkan selama 2 jam pada temperatur ruangan, kemudian HMTA divariasi 1-2M dan ditambahkan serta diaduk agar terbentuk larutan sol. Untuk mendapatkan kernel UO2 bulat seperti bola, larutan sol diteteskan kedalam larutan NH4OH 5 M pada temperatur ruangan, menghasilkan gel, lalu direndam, dicuci dengan amonia, air panas dan dikeringkan pada temperatur 150oC selama 4 jam, untuk menghilangkan sisa senyawa kimia yang tidak bereaksi. Setelah itu, gel dikalsinasi pada 800oC selama 4 jam, menghasilkan kernel U3O8, Kemudian kernel U3O8 direduksi pada temperatur 850oC selama 2 jam dengan gas H2 dalam medium gas N2 pada tekanan 50 mmHg hingga dihasilkan kernel UO2. Juga dipelajari pengaruh temperatur dan waktu reduksi kernel U3O8 hasil kalsinasi gel pada kondisi yang sama. Gel yang digunakan mempunyai komposisi, UO2(NO3)2 1M, urea 1M, 1,6 g PVA, THF 2M dan HMTA 1M. Temperatur reduksi divariasi dari 600-850oC dan waktu dari 1-4 jam. Spesifikasi kernel UO2 yang meliputi kerapatan, luas muka spesifik, jari-jari pori rerata dan rasio O/U dianalisis. Hasil analisis menunjukkan bahwa pembuatan kernel UO2 dapat dilakukan dengan proses gelasi total uranium, menggunakan uranil nitrat, urea, HMTA, PVA dan THF sebagai bahan dasar. Perubahan konsentrasi aditif urea dan HMTA serta temperatur dan waktu reduksi berpengaruh terhadap spesifikasi kernel UO2. Kondisi relatif baik diperoleh pada konsentrasi urea 1,8 M dan HMTA 1,8 M, temperatur reduksi 800-850oC dan waktu reduksi 2 jam. Kernel UO2 yang dihasilkan mempunyai mikrostruktur halus, kerapatan sebesar 58,45 -66,70 % DT, luas muka spesifik sebesar 3,97-4,79 m2/g, jari-jari pori rerata sebesar 16,69-24,69 Å dan rasio O/U sebesar 2,04-2,09. Kata kunci: Aditif, gelasi total uranium, sol, gel , karakterisasi, spesifikasi dan mikrostruktur ABSTRACT THE INFLUENCE OF THE UREA, HMTA AS ADDITIVE, TIME AND TEMPERATURE OF REDUCTION ON UO2 KERNEL SPECIFICATION. The influence of the urea and HMTA as additives, time and temperature reduction on UO2 kernel specification has been studied. UO2 kernel was made up by total gelation process uranium (TGU)). Uranyl nitrate, urea, HMTA, polyvinyl alcohol (PVA), and tetra hidrofurfural (THF), were used as base materials. First step, 20 ml mixed solution that consist of 1M uranyl nitrate, varied 1 to 2 M urea, 1.6 g PVA, 2M THF, and water. The were prepared solution then was stirred and heated up to 70oC temperature for 20 minutes to form homogenous solution. The solution then was left on room temperature for 2 hours. On that solution HMTA that varied 1 M to 2 M was added while being stirred in order to be sol solutions. The sol solution was dropped into solution of 5 M NH4OH on room temperature to get spherical UO2 kernel, then was soaked, washed using ammonia, hot water and dried at 150 oC for 4 hours to remove chemical compound residue that was not reacted. After that, gel was calcinated at 800oC for 4 hours, to produce that U3O8 kernel, then followed reduction process at 850oC for 2 hours using the H2 and N2 gases on 50 mmHg. The influence of time and temperature reduction on the calcinated U3O8 kernel at the same conditions was also studied. The composition of used gel were 1M UO2(NO3)2, 1M urea, 1.6 g PVA, 2M THF and 1M HMTA, and temperature reduction were varied from 600 to 850oC for 1 to 4 hours. UO2 kernel spesification were analyzed on their density, spesific surface area, means pore radius and O/U ratio. The result, showed that UO2 could be produced by total gelation process of uranium using uranyl nitrate, urea, HMTA, PVA, and THF as constituent materials. The varied concentration of urea & HMTA, time and temperature reductions have influenced on UO2 kernel spesification. The relative condition was achieved on the composition of 1.8 M urea, 1.8 M HMTA concentration, temperature reduction 800-850oC for 2 hours of time reduction. Resulted UO2 kernel has fine microstructure, the density was 58.45 – 66,70 % DT, spesific surface area was 3.97- 4.79 m2/g, mean pore radius was 16.69-24.69 Å and the O/U ratio was 2,04-2,09. Key words: The additive, total gelation of uranium, sol, gel, characterization, specification and microstructur