Wan Kim

Daily intakes of naturally occurring radioisotopes in typical Korean foods

The concentrations of naturally occurring radioisotopes ((232)Th, (228)Th, (230)Th, (228)Ra, (226)Ra, and (40)K) in typical Korean foods were evaluated. The daily intakes of these radioisotopes were calculated by comparing concentrations in typical Korean foods and the daily consumption rates of these foods. Daily intakes were as follows: (232)Th, 0.00-0.23; (228)Th, 0.00-2.04; (230)Th, 0.00-0.26; (228)Ra, 0.02-2.73; (226)Ra, 0.01-4.37 mBq/day; and (40)K, 0.01-5.71 Bq/day. The total daily intake of the naturally occurring radioisotopes measured in this study from food was 39.46 Bq/day. The total annual internal dose resulting from ingestion of radioisotopes in food was 109.83 muSv/y, and the radioisotope with the highest daily intake was (40)K. These values were same level compiled in other countries.

Luminescence and photostimulated luminescence of SrCl2:Eu2+ doped with Na+ ions

The photoluminescence (PL) and photostimulated luminescence (PSL) properties of SrCl2:Eu2+ and SrCl2:Eu2+:Na+ are investigated. A strong PSL emission is observed for SrCl2:Eu2+ and its intensity is enhanced by codoping with Na+ ions. The mechanisms of PL and PSL are discussed in relation to the formation of F centers in SrCl2:Eu2+ and SrCl2:Eu2+:Na+.

230,232Th in milk, meat, and grain in korea

The concentrations of natural radioisotopes 230Th and 232Th in Korean foods were measured by the method of calcium oxalate co-precipitation in addition to the conventional anion-exchange method and alpha spectroscopic measurement. The 230Th concentrations(mBq/kg-fresh) in Korean foods were found to be as follows: milk 0.14~2.45, pork 2.98~8.97, beef 1.94~9.80, chicken 1.22~13.0, rice 0.43~2.35, wheat 0.53~14.4, and soybeans, 8.44~91.6. The 232Th concentrations(mBq/kg-fresh) in Korean foods were found to be as follows: milk 0.01~2.46, pork 0.28~9.32, beef 1.02~5.34, chicken 0.56~4.98, rice 0.32~2.54, wheat 0.53~20.0, and soybeans, 2.30~42.2. The annual internal dose of Th was also estimated. The annual internal dose of 230Th and 232Th in milk was about 0.006 uSv/yr and much lower than that of other countries because of the low intake of milk in Korea compared to other countries. The annual internal dose of 230Th and 232Th in the rice was about 0.043 pSv/yr and highest because rice is the staple food of Koreans.

Optical Pumping Spin Exchange 3He Gas Cells for Magnetic Resonance Imaging

We present a device for spin‐exchange optical pumping system to produce large quantities of polarized noble gases for Magnetic Resonance Imaging (MRI). A method and design of apparatus for pumping the polarization of noble gases is described. The method and apparatus enable production, storage and usage of hyperpolarized noble gases for different purposes, including Magnetic Resonance Imaging of human and animal subjects. Magnetic imaging agents breathed into lungs can be observed by the radio waves of the MRI scanner and report back physical and functional information about lung’s health and desease. The technique known as spin exchange optical pumping is used. Nuclear magnetic resonance is implemented to measure the polarization of hyperpolarized gas. The cells prepared and sealed under high vacuum after handling Alkali metals into the cell and filling with the 3He‐N2 mixture. The cells could be refilled. The 3He reaches around 50% polarization in 5–15 hours.

Polarized 3He Target Setup with Spin Exchange Method

Polarized 3He target plays an important role in studying form factor and spin structure function of neutron with spin‐dependent electron scattering. It is also widely used in applications, for example, as MRI and spin filter, etc. Presently we are developing polarized 3He target using spin exchange optical pumping method. The progress in construction of Vacuum and NMR systems are reported. We also present the preliminary results from study of thermal equilibrium signals of water.

Luminescence in SrCl 2 :Eu 2+ ,Na + X-ray Storage Phosphor

Photoluminescence(PL), photostimulated luminescence(PSL) and thermoluminescence(TL) in : , phosphor powder were measured, and the activation energies(trap depth) of traps associated with TL and PSL were investigated. The PL and PSL in the studied sample is due to the 5d\longrightarrowtransition of . TL glow curve is single peak, and its peak temperature is about 377.2 K. The PL, PSL and TL emission spectra of the phosphors are located in the range of 380∼440 nm, peaking at 408 nm. The activation energy of the PSL trapping center is 0.78 eV and that of the TL trapping center is 0.79 eV. We, thus, suggest that the trapping centers giving rise to the PSL are identical to those giving rise to the TL.

Photostimulated Luminescence and Photoluminescence of SrCl 2 :Eu 2+ Phosphors

phosphors were prepared by the solid phase reaction method, and their photostimulated luminescence(PSL) and photoluminescence(PL) characteristics were investigated. The PSL and PL peak of the phosphors are due to the transition of ions in phosphors. The PSL and PL spectrum obtained by the 355nm excitation was observed in region with the peak at 407 nm. The dose response of the PSL phosphors were linear within of 100 kV X-ray. The fading of the phosphors at room temperature was approximately 60% after 20 min.

Preparation and Properties of the X-ray Storage Phosphors BaFBr 1-x I x :Eu 2+ , Na +

The forming conditions of X-ray storage phosrhors , have been investigated, and measured the PSL emission spectra and its intensity, fading characteristics and does dependence of the prepared phosphors. These characteristics were compared with those of commercial image plate (ST-III) obtained from Fuji Photo Film Co. The optimal preparing conditions of , Phosphor were 0.5 mol% of , 4.0 mol% of NaF and composition ratio x

Thermoluminescence and Photostimulated Luminescence of BaFBr:BaFBr:Eu 2+ Phosphor

BaFBr: phosphors were prepared, and the thermoluminescence(TL) and photostimulated luminescence(PSL) of the prepared phosphors were measured. Two glow peaks around 352 and 448 K are observed for x-ray irradiated BaFBr: phosphors, and the activation energy of the main glow peak(352 K) was about 0.96 eV. The spectral range of the PSL was , and the activation energy of the trap giving rise to PSL was about 0.98 eV. The activation energy of the traps giving rise to TL is agreed to those giving rise to PSL within experimental error.