Kil Yong Lee

Application of Laser Induced Plasma Spectroscopy to the Analysis of Rock Samples

Laser induced plasma spectroscopy has been applied to the analysis of element distribution mapping of polished rock sections. The plasma was generated by focusing a frequency-doubled second harmonic 532 nm Nd:YAG laser on the target under atmospheric conditions. The experimental parameters, such as laser energy, atomic emission line and time profile of the plasma spectrum, were characterized to obtain optimum experimental conditions and estimate the element composition of the target surface. For the element mapping of samples, an X–Y stage was used to move the sample and an element image of 50 × 50 mm could be made in 30 min. Using this technique, the element concentration distribution of Ba, Cu, Fe, Mn, Pb, Si and Sr in polished rock sections were obtained. Quantitative analysis was achieved by analyzing standard rock samples. Calibrated concentration versus plasma intensity was used for the color grading for the mapping of element concentration distribution.

Determination of U, Th and other impurities in molybdenum by radiochemical neutron activation analysis

A radiochemical separation method has been applied for determining uranium, thorium and other impurities in molybdenum metallic powder. The impurities of Na, K, Sm, Cr, Zr, Cs, Rb, Zn, Fe, Co and La were separated with a cation exchange resin, and uranium and thorium were, then, separated with an anion exchange resin. The content of impurities were determined by a single comparator method using two monitors, gold and cobalt.

Sorption properties of152Eu and241 Am in geological materials: Eu as an analogue for monitoring the Am behaviour in heterogeneous geological environments

In order to confirm the similar behavior of Eu and Am in heterogeneous geological materials, we carried out the batch experiments for determining the sorption property of radionuclides,152Eu and241Am. We used four different types of core rocks including biotite banded gneiss, biotite gneiss, metabasite and andestic tuff, and selected two samples per each lithology, one of which is fracture-bearing and another is fracture-free. Except for metabasites, rock samples of each type are similar in their compositions. We calculated sorption ratios of two radionuclides from the experimental results. Biotite gneiss and tuff had similar sorption trends for152Eu and241Am regardless of the existence of fractures, whereas two metabasite samples showed very different sorption properties. Such difference in the sorption trends revealed a close relationship with chemical compositions of the host rocks. Nevertheless,152Eu and241Am showed similar adsorption trends for all the samples with variable contact times regardless of petrography and pH variations, and particularly, the sorption trends of152Eu and241Am in the metabasites were similar. This observation suggests that Eu and Am have similar sorption properties on geological materials. Therefore, Eu can be used as a useful analogue of Am in all kinds of geological environments regardless of variations in lithology and pH of groundwater. In addition, sorption ratios of152Eu and241 Am are correlated with the contents of P2O5 and TiO2, suggesting that the chemical components such as P2O5 and TiO2 might be important for deciphering the interaction between the radionuclide and groundwater.

Neutron activation analysis of high purity nickel by solvent extraction using 2-benzylpyridin/benzene

A radiochemical neutron activation analysis using solvent extraction has been applied for the determination of trace impurities in high purity nickel. Because of the high activity of58Co produced by the nuclear reaction,58Ni(n,p)58Co, cobalt should be separated from the impurities. Removal of cobalt from the other trace elements in the aqueous acidic solution containing 1M thiocyanate ion (KSCN) was achieved by extraction with 1M2-benzylpyridin (BPy) in benzene. From the result of tracer experiments, cobalt was completely separated from most other elements except Fe, Mo and Zn. To determine the experimental accuracy, NIST SRM 673 nickel oxide was analyzed and the results agreed well within 10% deviation. This established radiochemical method was applied to the analysis of high purity nickel samples.

Using 222Rn as a naturally occurring tracer to estimate NAPL contamination in an aquifer

The naturally occurring radioisotope (222)Rn was used as a partitioning tracer to evaluate the presence and amount of a non-aqueous phase liquid (NAPL) in an aquifer. The batch experiment results of a diesel contaminated soil showed that the emanation rate of (222)Rn decreased to 31%, relative to a background rate. Batch experiment results of water contaminated by gasoline, diesel, PCE and TCE were similar. A field study to examine TCE contamination was conducted using 54 groundwater samples in Wonju city, Republic of Korea. Estimates of TCE contamination ranged from <0.001 mg/L to 14.3mg/L, and (222)Rn concentrations ranged from 1.89 Bq/L to 444. Results of (222)Rn analysis showed that TCE contamination was mainly restricted to an asphalt laboratory area and that the (222)Rn values of a NAPL-contaminated aquifer were correlated with TCE analytical results.

Classification of Korean old potteries by trace elements analysis

Instrumental neutron activation analysis (INAA), ICP/MS and XRF were applied for the characterization of relative locales of Korean old potteries, which had three different era and four regional characters. From the elemental analysis, two major elements such as Fe, Ti and some minor elements such as Cr, Sc, Zr were supposed to the main contributing factors for the regional classification. And the contents of rare earth elements, such as Eu and La were different in each pottery.

DETERMINATION OF U AND Th IN TUNGSTEN BY RADIOCHEMICAL NEUTRON ACTIVATION ANALYSIS

A radiochemical separation method using an anion exchange resin has been applied to 4N grade tungsten for determining U, Th and 4 other elements. While tungsten remained in the resin, Na, K and As were separated with 0.05M HCl and 1M HF and then U, Th and Cr were eluted with 1M HCl and 1M HF. The separation yield of neptunium (U) was influenced largely by the amount of thorium, but this influence could be neglected as the concentration of the thorium was below 0.5μg/ml. The content of these elements were calculated by a single comparator method using monitors, gold and cobalt. The detection limits of U and Th are 4.0 and 1.2 ppb, respectively.

An open loop equilibrator for continuous monitoring of radon at the groundwater–surface water interface

AbstractA continuous monitoring system (CMS) using an open loop equilibrator for assessment of 222Rn at the groundwater–surface water interface was developed and tested. For the characterization and validation of the system, three air loops (open loop, closed loop, and open bubble loop) were tested in relation to high and precise count rates, rapid response, and equilibration of radon. The water and air stream is fed to the equilibrator by an experimental setup with a commercial submersible water pump and the internal pump with built-in radon-in-air detector. Efficiency calibration of the CMS is done by simultaneous determination of a groundwater sample using liquid scintillation counting, and the RAD7 accessories RAD-H2O, BigBottle RAD-H2O. The higher count rates are provided by the closed loop. However, the open loop with bubbler (open bubble loop) provides the best precision count rates, rapid response, and equilibration time. The CMS allows radon determination in discrete water samples as well as continuous water streams.

Determination of recharge fraction of injection water in combined abstraction-injection wells using continuous radon monitoring

The recharge fractions of injection water in combined abstraction-injection wells (AIW) were determined using continuous radon monitoring and radon mass balance model. The recharge system consists of three combined abstraction-injection wells, an observation well, a collection tank, an injection tank, and tubing for heating and transferring used groundwater. Groundwater was abstracted from an AIW and sprayed on the water-curtain heating facility and then the used groundwater was injected into the same AIW well by the recharge system. Radon concentrations of fresh groundwater in the AIWs and of used groundwater in the injection tank were measured continuously using a continuous radon monitoring system. Radon concentrations of fresh groundwater in the AIWs and used groundwater in the injection tank were in the ranges of 10,830-13,530 Bq/m3 and 1500-5600 Bq/m3, respectively. A simple radon mass balance model was developed to estimate the recharge fraction of used groundwater in the AIWs. The recharge fraction in the 3 AIWs was in the range of 0.595-0.798. The time series recharge fraction could be obtained using the continuous radon monitoring system with a simple radon mass balance model. The results revealed that the radon mass balance model using continuous radon monitoring was effective for determining the time series recharge fractions in AIWs as well as for characterizing the recharge system.

Tritium concentration in rain with seasonal variation

The concentration of the tritium in precipitation from 2007 to 2009 has been analyzed for using tracer of groundwater study. The samples were collected monthly at Daejeon. The tritium concentrations in precipitation were ranged from 4.2 TU to 18.6 TU. The contents were higher at spring and fall season and lower at summer and winter season. The weighted average tritium content in precipitation was .