Characteristics of Thermal Neutron Flux Distribution in a Phantom Irradiated by Epithermal Neutron Beam from Double Layer Beam Shaping Assembly (DBSA)

Bilal odin; Gede Bayu Suparta; Arief Hermanto; Dwi Satya Palupi; Yohannes Sardjono; Rasito A

doi:10.52763/PJSIR.PHYS.SCI.62.3.2019.167.173

Bilal odin Department of Physics, Faculty of Mathematic and Natural Science, Gajah Mada University, Indonesia
Gede Bayu Suparta Department of Physics, Faculty of Mathematic and Natural Science, Gajah Mada University, Indonesia
Arief Hermanto Department of Physics, Faculty of Mathematic and Natural Science, Gajah Mada University, Indonesia
Dwi Satya Palupi Department of Physics, Faculty of Mathematic and Natural Science, Gajah Mada University, Indonesia
Yohannes Sardjono Center for Accelerator Science and Technology, National Nuclear Energy Agency, Indonesia
Rasito A Center for Science and Applied Nuclear Technology, Bandung, Indonesia

DOI: https://doi.org/10.52763/PJSIR.PHYS.SCI.62.3.2019.167.173

Keywords: double-layers BSA, MCNPX, PHITS, neutron flux, phantom

Abstract

A simulation study on the Double-layer Beam Shaping Assembly (DBSA) system has been carried out. This study used fast neutron beam resulting from reactions of 30 MeV protons with beryllium target. The MCNPX code was utilized to design the DBSA and the phantom as well as to calculate neutron flux on the phantom. The distribution of epithermal neutron flux and gamma in the DBSA and phantom were computed using the PHITS code. The spectrum of radiation beams generated by the DBSA shows the characteristics that the typical epithermal neutron flux of 1.0 x10⁹ n/(cm².s), the ratio of epithermal to the thermal and fast neutron flux of 344 and 85, respectively and the ratio of gamma dose to the epithermal neutron flux of 1.82 x 10^-13 Gy.cm². The test of epithermal neutron beams irradiation on the water phantom shows that epithermal neutrons are thermalized and penetrate the phantom up to 12 cm in depth. The maximum value of neutron flux is 1.1 x 10⁹ n/(cm².s) at a depth of 2 cm in phantom.