Sang-In Bak

GEANT4 and PHITS simulations of the shielding of neutrons from the 252 Cf source

Monte Carlo simulations are performed by using the GEANT4 and the PHITS for studying the neutron-shielding abilities of several materials, such as graphite, iron, polyethylene, NS-4-FR and KRAFTON-HB. As a neutron source, 252Cf is considered. For the Monte Carlo simulations by using the GEANT4, high precision (G4HP) models with the G4NDL 4.2 based on ENDF/B-VII data are used. For the simulations by using the PHITS, the JENDL-4.0 library is used. The neutron-dose-equivalent rates with or without five different shielding materials are estimated and compared with the experimental values. The differences between the shielding abilities calculated by using the GEANT4 with the G4NDL 4.2 and the PHITS with the JENDL-4.0 are found not to be significant for all the cases considered in this work. The neutron-dose-equivalent rates obtained by using the GEANT4 and the PHITS are compared with experimental data and other simulation results. Our neutron-dose-equivalent rates agree well with the experimental dose-equivalent rates, within 20% errors, except for polyethylene. For polyethylene, the discrepancies between our calculations and the experiments are less than 40%, as observed in other simulation results.

Simulation and measurement of characteristics of MICROMEGAS gaseous detectors

MICROMEGAS detectors have been developed for the detection and tracking of charged and neutral particles. The control parameters of MICROMEGAS include materials, the type of gases, the mixing ratio of gases and the geometry. Simulations of MICROMEGAS are conducted to optimize the characteristics and performance with respect to the nature of the gas mixture, applied voltages of drift and amplification regions. Quantities such as the equi-potential lines, electron drift lines, and avalanche process of electrons and ions are calculated. Two MICROMEGAS detectors are built and characterized by using standard X-ray sources. The voltage gains are measured against the applied voltage range for different gas pressures and are compared with our simulation results.

Design study and heat transfer analysis of a neutron converter target for medical radioisotope production

A worldwide challenge in the near future will be to find a way of producing radioisotopes in sufficient quantity without relying on research reactors. The motivation for this innovative work on targets lies in the accelerator-based production of radioisotopes using a neutron converter target as in the transmutation by adiabatic resonance crossing concept. Thermal analysis of a multi-channel helium cooled device is performed with the computational fluid dynamics code CFX. Different boundary conditions are taken into account in the simulation process and many important parameters such as maximum allowable solid target temperature as well as uniform inlet velocity and outlet pressure changes in the channels are investigated. The results confirm that the cooling configuration works well; hence such a solid target could be operated safely and may be considered for a prototype target.

Implementation of an LBE spallation target in an accelerator-driven molten salt subcritical reactor

ABSTRACT An accelerator-driven system (ADS) combined with a subcritical molten salt reactor (MSR) is a type of hybrid reactor originally designed to use Th/U (or U/Pu ) fuel cycles. In most accelerator-driven molten salt reactor (AD-MSR) concepts, the salt material is also used as a target for inducing spallation neutrons. Although a neutron source is an important component in the design of ADS, only a few studies have addressed the effects of the neutron spallation source in the AD-MSR. Incidentally, there is no quantitative study on how much the beam power can be reduced by installing a spallation target in a sodium chloride-based fast reactor. We studied the proton and the neutron source efficiencies of an AD-MSR with chloride fuels by considering an Lead Bismuth Eutectic (LBE) spallation target. This LBE target is found to increase the proton source efficiency significantly. The required beam power for an AD-MSR can be reduced by 33 % and 16 % for NaCl-Th/233U and NaCl-U/Pu fuels, respectively, relative to the AD-MSR without the LBE spallation target by keeping the same keff. The energy gain can be increased up to 1.5 times and 1.2 times for NaCl-Th/233U and NaCl-U/Pu fuels, respectively. Thus, incorporating a spallation target module in an AD-MSR can significantly reduce the burden on the accelerator.

ADS Research Activities at Sungkyunkwan University

Thorium-based accelerator-driven system (ADS) technology for future nuclear energy is being developed at Sungkyunkwan University. Our research activities include research on computational modeling, partitioning and transmutation, detector development, and life cycle assessment analysis. A brief overview is given here.

Neutronic Analysis and Transmutation Performance of Th-Based Molten Salt Fuels

There have been many studies on lithium–beryllium fluoride compounds as the molten salt coolant for thorium-based molten salt reactors (MSR), but sodium- or lead-based chloride compounds have not been studied. we studied a subcritical ADS with molten salt fuels using thorium and MA for investigating the potential of the system to breed 233U and burn MA.