Jong-Myoung Lim

Analytical evaluation of natural radionuclides and their radioactive equilibrium in raw materials and by-products

An investigation into the distribution of natural radionuclides and radioactive secular equilibrium in raw materials and by-products in a domestic distribution was conducted to deduce the optimum conditions for the analytical evaluation of natural radionuclides for (238)U, (226)Ra, and (232)Th using a gamma-ray spectrometer and inductively coupled plasma mass spectrometer (ICP-MS). The range of the specific activities of natural radionuclides was first evaluated by analyzing (228)Ac and (214)Bi, which are (232)Th and (226)Ra indicators, respectively, in about 100 samples of raw materials and by-products through a gamma-ray spectrometer. From further experiments using several samples selected based on the results of the distribution of natural radionuclides, the validation of their analytical evaluations for the indirect measurements using a gamma-ray spectrometer and direct measurements using ICP-MS was assured by comparing their results. Chemically processed products from the raw materials, such as Zr sand and ceramic balls, were generally shown for the type of bead and particularly analyzed showing a definite disequilibrium with above a 50% difference between (238)U and (226)Ra in the uranium series and (232)Th and (228)Ra in the thorium series.

Feasibility about the Direct Measurement of 226 Ra Using the Gamma-Ray Spectrometry

U should be corrected to calculate the net peak area in the energy spec-trum. In general, it is very difficult to conduct peaks stripping with difference of about 0.5 keV, although a HPGe with the superior resolution is applied and the maximum channels is applied to the spectrometer. In this study, several interference correction techniques in the direct measurement were surveyed to evaluate the feasibility for the measurement of

Indoor Air Quality Pollution of PM2.5 and Associated Trace Elements Affected by Environmental Tobacco Smoke

Environmental tobacco smoke (ETS) samples were collected separately in mainstream and side-stream smoke using a self-designed smoking machine, and a total 40 of PM2.5 was collected with low volume air sampler at indoor environments with and without ETS in Daejeon, Korea. About 20 trace elements including toxic metals like As, Cr, Mn, Se, V, and Zn were determined in PM2.5 and ETS samples by instrumental neutron activation analysis (INAA). It is found that the emission factors of K, Cl, Na, and Al were much higher than those of toxic elements for both mainstream and side-stream smoke. The average concentration of PM2.5 was enriched by 1.5 times at smoking area (58.7±18.1 µg/m 3 ) than at smoking free area (38.6±12.7 µg/m 3 ). The concentration ratio of each element between smoking and smoking free area were ranged from 1.1 to 6.0 except Cu (1.0); especially, Ce (6.0), La (5.2), K (2.3), and Co (2.0) showed higher ratio, which suggests that the ETS is one of the possible increasing factors of PM2.5 and elemental concentration at indoor environment.

Validation of the quantification of natural radionuclides in raw materials and by-products using gamma-ray spectrometry

The validation of a method for the indirect quantification for 238U, 226Ra, and 232Th activity and the direct quantification for 40K activity using gamma-ray spectrometry was performed in view of consistency, reliability, and accuracy of the results. The gas tightness of Al containers used to confine the radon gas was verified from the establishment of the secular equilibrium between 226Ra and its indicator. To evaluate validation parameters such as linearity, range, and accuracy, it was important to verify the equilibrium state of the reference materials (RM) for U and Th, because the ingrowth of progenies in the uranium decay series can affect the quantification of 226Ra activity even if based on a certified reference material (CRM), while the ingrowth of 228Ra from the thorium decay series should be secured in order to use 228Ac as an indicator of 232Th. In addition, the ruggedness of the method regarding different materials was checked using two kinds of CRM, namely bauxite as an example of a raw material and coal fly ash as a by-product.

Analytical method for the determination of gross beta, 90Sr, 226Ra and Pu isotopes in environmental samples

This study presents analytical methods for the determination of gross beta, 90Sr, 226Ra and Pu isotopes using samples in the IAEA-TEL-2015-04 ALMERA Proficiency Test exercise. Samples for gross beta were prepared by evaporation and then analyzed using a gas proportional counter. 90Sr in the liquid sample was concentrated as SrCO3 precipitates and purified by Sr resin. Pu isotopes and 90Sr in the soil sample were extracted from the sample by mineral acid leaching and separated using TEVA and Sr resin, respectively. Pu isotopes were determined by alpha spectrometry and 90Sr were determined with a liquid scintillation counter. Radium in the soil sample was extracted by LiBO2 fusion, and the radon-emanation method using LSC was applied for the determination of 226Ra.

Limitations of gamma-ray spectrometry in the quantification of 238U and 232Th in raw materials and by-products

The effect of interference and disequilibrium was evaluated in analyzing 238U and 232Th using gamma-ray spectrometry. The interference in 234Th as an indicator of 238U was considerably increased according to the activity level of 232Th compared with that of 238U. However, its correction was necessary to assume that the secular equilibrium in the thorium decay series must be secured in the material. In addition, the disequilibrium in the decay series can be easily shown in the chemical process for manufacturing materials. This makes the limitation in the indirect measurement of natural radionuclides using gamma-ray spectrometry, especially in chemically processed products.