• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1535-1540
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• 2022

A solid tungsten target was used at the China Spallation Neutron Source (CSNS) with 100 kW proton beam power. To improve the lifetime, hot isostatic pressing (HIP) process was selected to bond tantalum cladding with tungsten plates. Radioactive isotope ¹⁸²Ta, an activation product of tantalum, was found in the cooling water after a period of operation, however, no radioactive isotopes of ¹⁸⁷W was found, which shows the tantalum layer remained mostly intact. The CSNS Target-1 had been operating safely for three years and was replaced by Target-2 in August 2020.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.378-390
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• 2023

The SPES (Selective Production of Exotic Species) facility, currently under development at Legnaro National Laboratories of INFN, aims at the production of intense RIB (Radioactive Ion Beams) employing the Isotope Separation On-Line (ISOL) technique for interdisciplinary research. The radioactive isotopes of interest are produced by the interaction of a multi-foil uranium carbide target with a 40 MeV 200 μA proton beam generated by a cyclotron proton driver. The Target Ion Source (TIS) is the core of the SPES project, here the radioactive nuclei, mainly neutron-rich isotopes, are stopped, extracted, ionized, separated, accelerated and delivered to specific experimental areas. Due to efficiency reasons, the TIS unit needs to be replaced periodically during operation. In this highly radioactive environment, the employment of autonomous systems allows the manipulation, transport, and storage of the TIS unit without the need for human intervention. A dedicated remote handling infrastructure is therefore under development to fulfill the functional and safety requirement of the project. This contribution describes the layout of the SPES target area, where all the remote handling systems operate to grant the smooth operation of the facility avoiding personnel exposure to a high dose rate or contamination issues.

• Progress in Medical Physics
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• v.23 no.3
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• pp.162-168
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• 2012

In proton therapy, in vivo dose verification is one of the most important parts to fully utilize characteristics of proton dose distribution concentrating high dose with steep gradient and guarantee the patient safety. Currently, in order to image the proton dose distribution, a prompt gamma distribution detection system, which consists of an array of multiple CsI(Tl) scintillation detectors in the vertical direction, a collimator, and a multi-channel DAQ system is under development. In the present study, the optimal design of prompt gamma distribution detection system was studied by Monte Carlo simulations using the MCNPX code. For effective measurement of high-energy prompt gammas with enough imaging resolution, the dimensions of the CsI(Tl) scintillator was determined to be $6{\times}6{\times}50mm^3$. In order to maximize the detection efficiency for prompt gammas while minimizing the contribution of background gammas generated by neutron captures, the hole size and the length of the collimator were optimized as $6{\times}6mm^2$ and 150 mm, respectively. Finally, the performance of the detection system optimized in the present study was predicted by Monte Carlo simulations for a 150 MeV proton beam. Our result shows that the detection system in the optimal dimensions can effectively measure the 2D prompt gamma distribution and determine the beam range within 1 mm errors for 150 MeV proton beam.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2139-2146
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• 2023

During reactor operation, the divertor must withstand unprecedented simultaneous high heat fluxes and high-energy neutron irradiation. The extremely severe service environment of the divertor imposes a huge challenge to the bonding quality of divertor joints, i.e., the joints must withstand thermal, mechanical and neutron loads, as well as cyclic mode of operation. In this paper, potassium-doped tungsten (KW) is selected as the plasma facing material (PFM), oxygen-free copper (OFC) as the interlayer, oxide dispersion strengthened copper (ODS-Cu) alloy as the heat sink material, and reduced activation ferritic/martensitic (RAFM) steel as the structural material. In this study, a vacuum brazing technology is proposed and optimized to bond Cu and ODS-Cu alloy with the silver-free brazing material CuSnTi. The most appropriate brazing parameters are a brazing temperature of 940 ℃ and a holding time of 15 min. High-quality bonding interfaces have been successfully obtained by vacuum brazing technology, and the average shear strength of the as-obtained KW/Cu and ODS-Cu alloy joints is ~268 MPa. And a fabrication route for manufacturing the flat-type divertor target based on brazing technology is set. For evaluating the reliability of the fabrication technologies under the reactor relevant condition, the high heat flux test at 20 MW/m² for the as-manufactured flat-type KW/Cu/ODS-Cu/RAFM mockup is carried out by using the Electron-beam Material testing Scenario (EMS-60) with water cooling. This paper reports the improved vacuum brazing technology to connect Cu to ODS-Cu alloy and summarizes the production route, high heat flux (HHF) test, the pre and post non-destructive examination, and the surface results of the flat-type KW/Cu/ODS-Cu/RAFM mockup after the HHF test. The test results demonstrate that the mockup manufactured according to the fabrication route still have structural and interfacial integrity under cyclic high heat loads.

• Progress in Medical Physics
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• v.26 no.4
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• pp.250-257
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• 2015

Multi-leaf collimator (MLC) systems are frequently used to deliver photon-based radiation, and allow conformal shaping of treatment beams. Many proton beam centers currently make use of aperture and snout systems, which involve use of a snout to shape and focus the proton beam, a brass aperture to modify field shape, and an acrylic compensator to modulate depth. However, it needs a lot of time and cost of preparing treatment, therefore, we developed the manual MLC for solving this problem. This study was carried out with the intent of designing an MLC system as an alternative to an aperture block system. Radio-activation and dose due to primary proton beam leakage and the presence of secondary neutrons were taken into account during these iterations. Analytical calculations were used to study the effects of leaf material on activation. We have fabricated tray model for adoption with a wobbling snout ($30{\times}40cm^2$) system which used uniform scanning beam. We designed the manual MLC and tray and can reduce the cost and time for treatment. After leakage test of new tray, we upgrade the tray with brass and made the safety tool. First, we have tested the radio-activation with usually brass and new brass for new manual MLC. It shows similar behavior and decay trend. In addition, we have measured the leakage test of a gantry with new tray and MLC tray, while we exposed the high energy with full modulation process on film dosimetry. The radiation leakage is less than 1%. From these results, we have developed the design of the tray and upgrade for safety. Through the radio-activation behavior, we figure out the proton beam leakage level of safety, where there detects the secondary particle, including neutron. After developing new design of the tray, it will be able to reduce the time and cost of proton treatment. Finally, we have applied in clinic test with original brass aperture and manual MLC and calculated the gamma index, 99.74% between them.

• Journal of radiological science and technology
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• v.40 no.2
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• pp.297-302
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• 2017

In this study, the generation of photoneutrons between the 10 MV FF mode and the FFF mode was evaluated and the amount of photoneutrons generated by the 10 MV and 15 MV energy changes in the FFF mode was evaluated. The generated neutrons were evaluated at 13 measurement points and the KTEPC was used to collect the generated neutrons. 10 MV FF mode was measured at 10 MV FF mode and FFF mode at all measurement points. In the superior direction, 0.455mSv and 0.152mSv were the largest, and more than 33% optical neutron was generated in FF. 10 MV in FFF mode, 15 MV in 15 MV, and 0.402 mSv in the direction of Superior, and 6.9% in the direction.

• Journal of radiological science and technology
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• v.40 no.2
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• pp.281-287
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• 2017

The purpose of this study is to calculate the thickness of shielding for concrete which is mainly used for radiation shielding and study of the walls constructed to shield medical linear accelerator. The optimal shielding thickness was calculated using MCNPX(Ver.2.5.0) for 10 MV of photon beam energy generated by linear accelerator. As a result, the TVL for photon shielding was formed at 50~100 cm for pure concrete and concrete with Boron+polyethylene at 80~100 cm. The neutron shielding was calculated 100~140 cm for pure concrete and concrete with Boron+polyethylene at 90~100 cm. Based on this study, the concrete is considered to be most efficient method of using steel plates and adding Boron+polyethylene th the concrete.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.8-8
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• 2003

Electron-phonon interaction plays a significant role in forming of colossal magnetoresistance effect (CMR). Polaron formation was observed by neutron diffraction and by extended X-ray absorption fine structure (EXAFS) analysis. Local probe as given by the EXAFS is a useful method to study the polaronic charge and its dependence on temperature and ions size. Here we present the EXAFS study of polaronic charge in La/sub 0.7/Ca/sub 0.3-X/Ba/sub X/MnO₃ compositions. The single phase La/sub 0.7/Ca/sub 0.3-X/Ba/sub X/MnO₃ manganites (x=0; 0.03; 0.06, ..., 0.3) were prepared by ceramic technology [1]. The Curie temperature was determined by extrapolation of the temperature dependence of the magnetization (down to zero magnetization). EXAFS experiments were carried out at the 7C EC beam line of the Pohang Light Source (PLS) in Korea. The atomic pair distribution functions (PDF) were obtained by re-regularization method [2] from filtered spectra. The PDF for the x=0.3 sample showed a single peak function and for x=0.0, 0.03, 0.06, 0.09, 0.12 compositions were asymmetric in agreement with a small Jahn-Teller elongation of two (short and long) bonds of the MnO/sub 6/ octahedron. Dispersion, σ/sub Min-O//sup 2/, and asymmetry, σ/sub Min-O//sup 3/, of the Mn-O bond distances varied significantly with x and showed a maximums at x=0.09. The maximum of σ/sub Min-O//sup 2/ is caused by increase of dynamic rms displacements of the Mn-O distances near the T/sub C/. The observed x dependence of σ/sub Min-O//sup 3/ reflects the reduction of charge carriers mobility at approaching to T/sub C/ from low as well as high temperatures.

• Progress in Medical Physics
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• v.10 no.3
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• pp.151-157
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• 1999

The GafChromic film was used for the dosimetry of a balloon angio catheter filled with the radioisotope HO-166 for endovascular irradiation. The balloon angio catheter was 2 cm long and 3 mm in diameter when inflated. The isotope, Ho-166, was produced by the neutron bombardment using the research reactor in Korea Atomic Energy Research Insititute. Co-60 teletherapy beam was used for making H-D curve for the Gaf-Chromic film. The film dosimetry was measured with a videodensitometer. The radial dose distribution indicated that the absorbed dose dropped to about 20% of the surface dose at the 1 mm away from the balloon surface and at 5 mm position the dose decreased to below 1% of the surface dose. The result also shows that with the specific activity of Ho-l66, 250 mCi/ml it takes 230 seconds to deliver 1200 cGy to the region where is 1mm away from the balloon surface. The concentric isodose curves were also presented. The Ho-166 is an another alternative for endovascualr irradiation to prevent restenosis after PTCA (Percutaneous Trans Coronary Angioplasty)

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.407-408
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• 2011

Natural boron consists of two stable isotopes 10B and 11B with natural abundance of 18.8 atom percent of 10B and 81.2 atom percent of 11B. The thermal neutron absorption cross-section for 10B and 11B are 3837 barn and 0.005 barn respectively. 10B enriched specific compounds are used for control rods and as a reactor coolant additives. In this work 2 methods for boron enrichment were analysed: 1) Gas irradiation in static conditions. Dissociation occurs due to multiphoton absorption by specific isotopes in appropriately tuned laser field. IR shifted laser pulses are usually used in combination with increasing the laser intensity also improves selectivity up to some degree. In order to prevent recombination of dissociated molecules BCl3 is mixed with H2S 2) SILARC method. Advantages of this method: a) Gas cooling is helpful to split and shrink boron isotopes absorption bands. In order to achieve better selectivity BCl3 gas has to be substantially rarefied (~0.01%-5%) in mixture with carrier gas. b) Laser intensity is lower than in the first method. Some preliminary calculations of dissociation and recombination with carrier gas molecules energetics for both methods will be demonstrated Boron separation in SILARC method can be represented as multistage process: 1) Mixture of BCl3 with carrier gas is putted in reservoir 2) Gas overcooling due to expansion through Laval nozzle 3) IR multiphoton absorption by gas irradiated by specifically tuned laser field with subsequent gradual gas condensation in outlet chamber It is planned to develop software which includes these stages. This software will rely on the following available software based on quantum molecular dynamics in external quantized field: 1) WavePacket: Each particle is treated semiclassicaly based on Wigner transform method 2) Turbomole: It is based on local density methods like density of functional methods (DFT) and its improvement- coupled clusters approach (CC) to take into account quantum correlation. These models will be used to extract information concerning kinetic coefficients, and their dependence on applied external field. Information on radiative corrections to equation of state induced by laser field which take into account possible phase transition (or crossover?) can be also revealed. This mixed phase equation of state with quantum corrections will be further used in hydrodynamical simulations. Moreover results of these hydrodynamical simulations can be compared with results of CFD calculations. The first reasonable question to ask before starting the CFD simulations is whether turbulent effects are significant or not, and how to model turbulence? The questions of laser beam parameters and outlet chamber geometry which are most optimal to make all gas volume irradiated is also discussed. Relationship between enrichment factor and stagnation pressure and temperature based on experimental data is also reported.