STUDI PENAMBAHAN PERISAI RADIASI DI KANAL HUBUNG S-5 UNTUK MENGURANGI PAPARAN LINGKUNGAN

ABSTRAK ─ Telah dilakukan studi rencana penambahan perisai radiasi di atap kanal hubung S-5 dengan menggunakan bahan utama air. Tujuan penambahan perisai radiasi untuk mengurangi paparan pada atap kanal hubung S-5 agar pekerja radiasi tidak berpotensi menerima dosis radiasi melebihi Nilai Batas Dosis (NBD) yang diijinkan oleh BAPETEN, yaitu 20 mSv/tahun. Studi penambahan perisai radiasi dilakukan dengan membuat sebuah kolam pengukuran yang berukuran 8000(p)X2400(l)X300(t) mm3. Di dalam kolam ditentukan 9 titik pengukuran yang berjarak 1 meter. Pengukuran paparan radiasi, baik neutron maupun sinar-g, pada titik pengukuran dilakukan pada saat reactor beroperasi normal (15 MW), main shutter dan lithium shutter terbuka, dalam kondisi kolam belum diisi air, diisi air sedalam 15 cm dan 30 cm. Hasil pengukuran menunjukkan bahwa pada kedalaman air 30 cm paparan radiasi pada titik terdekat dengan sumber menurun dari 101,57 ɥSv/jam menjadi 1,09 ɥSv/jam untuk neutron dan 13.7 ɥSv/jam menjadi 3,95 ɥSv/jam untuk sinar γ. Paparan rad ini sudah tidak berpotensi menyebabkan pekerja radiasi mempunyai dosis melebihi NBD yang diijinkan oleh BAPETEN. Dari data pengukuran juga diperoleh data bahwa air sangat efektif untuk meredam radiasi neutron, tetapi kurang efektif untuk meredam radiasi sinar-g. Dari hasil studi rencana ini, akan dibuat perencanaan pembuatan perisai radiasi di atap kanal hubung S-5.  Kata kunci: perisai radiasi kanal hubung S-5, laju dosis S-5, paparan radiasi atap kanal hubung S-5 ABSTRACT ─ A study has been conducted for the addition of radiation shield on the roof of the S-5 canal using the main water material. The purpose of the adding a radiation shield is to reduce exposure to the S-5 canal roof so that radiation workers do not potentially receive radiation doses exceeding the Dose Limit (NBD) permitted by BAPETEN, ie 20 mSv/year. The study of the radiation shields additions was made by making a measuring pool with dimension 8000 X 2400 X 300 mm. Inside the pool is determined nine measurement point within 1 meter. Measurements of radiation exposure, both neutrons and g-rays, at the point of measurement are performed when the reactor operates normally (15 MW), the main shutter and open lithium shutter, in the condition the pool is not filled with water, filled with water as deep as 15 cm and 30 cm. The measurements showed that at a water depth of 30 cm the radiation exposure at the nearest point with the source decreased from 101.57 ɥSv/h to 1.09 ɥSv / h for neutrons and 13.7 ɥSv / hr to 3.95 ɥSv / h for γ rays. This radiation exposure has no potential to cause radiation workers to have a dose exceeding the NBD permitted by BAPETEN. From the measurement data also obtained data that water is very effective to reduce the radiation of neutrons, but less effective to reduce g-ray radiation. From the results of this study, will be made planning of radiation shielding on the roof of the S-5 canal. Keywords: radiation shield S-5 canal, S-5 dose rate, radiation exposure of S-5 canal roo

ANALISIS FASA MINOR DENGAN TEKNIK DIFRAKSI NEUTRON

ABSTRAKANALISIS FASA MINOR DENGAN TEKNIK DIFRAKSI NEUTRON. Keberadaan fasa minor dalam suatu cuplikan telah dianalisis dengan teknik difraksi neutron. Dalam penelitian ini dipilih cuplikan partikel nano Fe (PNF) sebagai objek studi kasus. Langkah pertama adalah menyiapkan cuplikan PNF dengan teknik ball milling. Cuplikan hasil milling selanjutnya disebut FIC2. Keberadaan fasa-fasa yang terbentuk di dalam cuplikan FIC2 dianalisis secara kualitatif dan kuantitatif dengan teknik difraksi neutron resolusi tinggi (HRPD) dan difraksi sinar-X (XRD). Data difraksi dianalisis dengan metode Rietveld memanfaatkan program FullProf dan dilakukan dengan mengacu pada data dukung, yakni ukuran partikel dan sifat magnetik bahan. Kedua jenis data dukung tersebut diperoleh berturut-turut dengan PSA (Particles Size Analyzer) dan VSM (Vibrating Samples Magnetometer). Hasil analisis menunjukkan bahwa kualitas fitting pola difraksi neutron lebih baik dari kualitas fitting pola difraksi sinar-X. Dari data difraksi neutron diperoleh bahwa FIC2 terdiri dari fasa Fe, gFe2O3, dan Fe3O4 berturut-turut sebanyak 78,62; 21,37 dan0,01%. Dari data difraksi sinar-X didapat bahwa FIC2 terdiri dari fasa Fe dan gFe2O3 berturut-turut sebanyak 99,96 dan 0,04%; sedangkan keberadaan fasa Fe3O4 tidak teramati.Dengan teknik difraksi neutron, keberadaan fasa minor dapat ditentukan secara akurat. Kata kunci: difraksi neutron, difraksi sinar-X, fasa minor. ABSTRACT ANALYSIS OF MINOR PHASE WITH NEUTRON DIFFRACTION TECHNIQUE. The presence of minor phases in a sample have been analyzed with the neutron diffraction technique. In this research, the sample of Fe nanoparticles (FNP) has been selected as the object of case study. The first step was to prepare the FNP sample with the ball milling technique. Hereinafter, the sample of milling result was referred FIC2. The presence of phases formed in FIC2 were analyzed qualitatively and quantitatively using the high resolution neutron diffraction (HRPD ) and X-Ray Diffraction (XRD) techniques. The diffraction data were analyzed by means of the Rietveld method utilizing a computer code, namely FullProf and performed by referring to the supporting data, namely particle size and magnetic properties of materials. The two kinds of supporting data were obtained from the PSA (Particles Size Analyzer) and VSM (Vibrating Samples Magnetometer), respectivelly.The analysis result shows that quality of fitting for neutron diffraction pattern is better than the fitting quality for x-ray diffraction pattern. Of the HRPD data were revealed that FIC2 consists of Fe, gFe2O3 and Fe3O4 phases as much as 78.62; 21.37 and 0.01%, respectively. Of the XRD data were obtained that FIC2 consits of Fe and gFe2O3 phases with amount of 99.96 and 0.04%, respectively; the presence of Fe3O4 phase was not observed. With the neutron diffraction technique, the presence of minor phase can be determined accurately. Keywords: neutron diffraction, X-ray diffraction, minor phase

Effects of the Preheating Temperature on the Crystal Structure and Texture of Martensitic Stainless Steel

Theoretically, the preheating temperature refers to the start martensite temperature (Ms), and the martensite transformation can be considered as the conservation of the invariant habit-plane in the lattice structure. The habit-plane is the interface plane between austenite and martensite as measured on a macroscopic scale.  From the calculation, Ms = 252 °C. The martensite formation can be affected by temperature or stress treatment. In this experiment, temperature treatment was conducted. The sample was treated at 250 °C ± 10 °C. Before and after the pre-heat treatment, the sample was characterized using the neutron diffraction method. BATAN’s Texture Diffractometer (DN2) with a neutron wavelength of 1.2799Å was used to characterize the sample. Analysis of the crystal structure showed that there are three phases before the preheating. The lattice parameters (a) obtained were as follows: for the -phase, a = 2.8501 ± 0.0004 Å; for the α’phase, a= b =2.517 ± 0.003 Å, and c= 3.581 ± 0.002 Å; for the -phase, a= 3.5884 ± 0.0004 Å, Rwp = 17.94%, and = 1.33. After preheating, only the -phase appears with a = 3.5830 ± 0.0005 Å, Rwp = 26.03%, and = 1.17. The orientation distribution function is modeled by the sample symmetrization model based on triclinic to orthorhombic sample symmetry. It shows that, before being preheated, the -phase has {100} <001> with texture index (F2 ) between 0.701 m.r.d. to 3.650 m.r.d., the α-phase has a texture index between 0.923 m.r.d. to 1.768 m.r.d., and the ’-phase has a texture index between 0.910 m.r.d. to 1.949 m.r.d. After being preheated, the -phase also has {100} <001> with a texture index between 0.846 m.r.d. to 3.706 m.r.d. It can be concluded, that because of the high preheating temperature, a phase change from martensite to austenite occurred that allowed the sample to be welded easily. After preheating, the -phase has the same cubic type orientation {100} <001>, and the texture index is nearly the same as that before preheating, with not martensite present