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- Author or Editor: H. G. Kim x
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Abstract
Monochromatic MeV-energy neutron source for secondary reaction was developed utilizing tritium embedded titanium (Ti-3H) thin film via 3H(p,n)3He reaction. We have measured the neutron energies and the energy spread by resonance reactions of 12C(n,tot) and 28Si(n,tot). The available energy was within the range from 0.6 to 2.6 MeV. Energy spread was 1.6% at energy of 2.077 MeV. The flux in the beam direction was determined to be 3.76·107 n/s/sr by irradiating 197Au by about 2 MeV neutrons. This source was shown to be useful for measurements of nuclear data by measuring the total cross sections of neutrons on Fe and comparing these data to the data of ENDF-6.
Nuclear Techniques in National Security Studies on Contraband Detection
IEC-based neutron generator for security inspection system
Summary
The Federal Radiological Monitoring and Assessment Center (FRMAC) is authorized by the Federal Radiological Emergency Response Plan to coordinate all off-site radiological response assistance to state and local governments, in the event of a major radiological emergency in the United States. The FRMAC is established by the U.S. Department of Energy, National Nuclear Security Administration, to coordinate all Federal assets involved in conducting a comprehensive program of radiological environmental monitoring, sampling, radioanalysis, quality assurance, and dose assessment. During an emergency response, the initial analytical data is provided by portable field instrumentation. As incident responders scale up their response based on the seriousness of the incident, local analytical assets and mobile laboratories add additional capability and capacity. During the intermediate phase of the response, data quality objectives and measurement quality objectives are more rigorous. These higher objectives will require the use of larger laboratories, with greater capacity and enhanced capabilities. These labs may be geographically distant from the incident, which will increase sample management challenges. This paper addresses emergency radioanalytical capability and capacity and its utilization during FRMAC operations.
A simple, rapid, and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the determination of zinc pyrithione (ZnPT) and pyrithione (PT) in shampoos. The method consisted of a liquid–liquid extraction for sample preparation. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode via the positive electrospray ionization interface. A linear regression (weighted 1/x) was used to fit calibration curves over the concentration range of 50–2000 ng/mL for both ZnPT and PT. Excellent linearity (r 2 ≥ 0.9996) was achieved for all. The method was validated and found to be accurate (95.9–108.2% for ZnPT and 94.9–110.4% for PT), precise, and selective. Analytes in shampoos were found to be stable in the autosampler (6 °C for 6 h), in room temperature (for 6 h), and after three freeze–thaw cycles, and recovery of analytes was reproducible (90.8–94.6% for ZnPT and 90.2–96.3% for PT).
Abstract
Neutron capture cross sections on 63Cu and 186W were measured by fast neutron activation method at neutron energies from 1 to 2 MeV. Monoenergetic fast neutrons were produced by 3H(p,n)3He reaction. Neutron energy spread by target thickness, which was assumed to be the main factor of neutron energy spread, was estimated to be 1.5% at neutron energy of 2.077 MeV. Neutron capture cross sections on 63Cu and 186W were calculated by reference comparison method on those of 197Au(n,γ). Not only statistical errors of gamma-counts from samples but also systematic errors in the counting efficiency for HP Ge detector and the uncertainty of areal density of samples were considered in calculating neutron capture cross section. Estimated neutron capture cross sections on 63Cu and 186W were also compared with ENDF-6 data.
Abstract
A nanosecond proton bunching system has been constructed at Korea Institute of Geoscience and Mineral Resources (KIGAM). This pulsed ion beam will be converted into corresponding duration of neutron pulse, which can reduce the scattered neutron background during neutron spectroscopy. The pulsed beam is obtained by deflection and double bunching by RF field. RF fields are applied to deflection and bunching electrodes as 2 kV p-p, 4 MHz and 2 kV p-p, 8 MHz, respectively. A push-pull RF amplifier has been designed and constructed with a maximum output power of 300 W continuous wave (CW) between 2 and 30 MHz. The main parameters of bunching beam were as follows: 8 MHz repetition rate, 2 ns FWHM, approximately 20% of duty factor and the maximum energy spread of 2 keV within a pulse.
Summary
Capsaicin has been reported to exhibit an inhibitory effect on the P-glycoprotein (P-gp) function in vitro. To investigate its concentration-dependent effect in vivo, a sensitive assay that can characterize the absorption and disposition of capsaicin needs to be developed. This study reports the development of a sensitive LC-MS/MS assay for the determination of capsaicin in mouse plasma. The sample pretreatment involved a one-step extraction of 20 μL plasma with t-butyl methyl ether. Separations were achieved on a C18 column and the detection was performed on an LC-ESI-MS/MS by multiple reaction monitoring. The assay was linear over a wide concentration range from 0.325 to 650 ng mL−1 (r > 0.999), with a LLOQ of 0.325 ng mL−1. The developed method was applied to i.v. (dose 0.325 and 0.65 mg kg) and oral absorption (dose 40 mg kg) studies in mice. After i.v. injection, the t 1/2,λz, V z and CL s ranged from 0.13–0.16 h, 127.6–141.8 mL, and 547.3–775.4 mL/h, respectively. After oral administration, a secondary peak was observed and the terminal half-life was prolonged (1.51 h). Capsaicin was poorly absorbed, with the absolute oral bioavailability (F) ranging from 1.02% to 1.56%. The developed assay may be useful in studies where sample volumes are limited.
Summary
In order to evaluate the use of gamma-ray treatment as a pretreatment to conventional biological methods, the effects of gamma-irradiation on biodegradability (BOD5/COD) of textile and pulp wastewaters were investigated. For all wastewaters studied in this work, the efficiency of treatment based on TOC removal was insignificant even at an absorbed dose of 20 kGy. However, the change of biodegradability was noticeable and largely dependent on the chemical property of wastewaters and the absorbed dose of gamma-rays. For textile wastewaters, gamma-ray treatment increased the biodegradability of desizing effluent due to degradation of polymeric sizing agents such as polyvinyl alcohol. Interestingly, the weight-loss showed the highest value of 0.97 at a relatively low dose of 1 kGy. This may be caused by the degradation of less biodegradable ethylene glycol prior to terephthalic acid decomposition. For pulp wastewater, the gamma-ray treatment did not improve the biodegradability of cooking and bleaching of C/D effluents. However, the biodegradability of bleaching E1 and final effluents was abruptly increased up to 5 kGy then slowly decreased as the absorbed dose was increased. The initial increase of biodegradability may be induced by the decomposition of refractory organic compounds such as chlorophenols, which are known to be the main components of bleaching C/D and final effluents.
Abstract
The method of tritium labeling of polychlorinated biphenyls (PCBs) has been developed. It allows producing of uniformly labeled tritium PCBs. High specific activity permits the tracing all of the tritium labeled PCBs biodegradation products. Radiochemical approach of the investigation of PCBs microbial degradation has been developed and PCB-destructive activity of soil bacteria strains has been studied. It was found that 4 investigated bacteria strains of Bacillus sp. has the ability accumulate and destroy PCBs. Use of developed radiochemical methods in complex with other analytical methods in investigation of PCBs biodegradation provide useful additional information. The radiochemical methods developed can be successfully used for wide screening of microorganisms, destructors of PCBs.
Abstract
239+240Pu concentrations and 240Pu/239Pu atom ratios in bottom sediments of the Yellow Sea, Korea Strait, East Sea (Sea of Japan), Sea of Okhotsk, and Northwest Pacific Ocean were determined. In coastal sediments near the Korean Peninsula, 239+240Pu concentrations varied from 0.02 to 1.72 Bq.kg-1, and their 240Pu/239Pu atom ratios from 0.15 to 0.24, with an average of 0.20±0.03. 240Pu/239Pu atom ratios of bottom sediments in the deep NW Pacific Ocean and its marginal seas (East, Okhotsk seas) were in the range of 0.15-0.23. A little elevated 240Pu/239Pu atom ratios in the bottom layer sediment may be due to Pu released into the environment during the pre-moratorium period, having high 240Pu/239Pu atom ratios and low 238Pu/239+240Pu activity ratios.
To solve a geophysical inverse problem means applying measurements to determine the parameters of the selected model. The inverse problem is formulated as the Bayesian inference. The Gaussian probability density functions are applied in the Bayes's equation. The CHAMP satellite gravity data are determined at the altitude of 400 km altitude over the South part of the Pannonian Basin. The model of interpretation is the right vertical cylinder. The parameters of the model are obtained from the minimum problem solved by the Simplex method.
