Authors:Yong-Jae Kim, Chang-Kyu Kim, Cheol-Su Kim, Ju-Yong Yun, and Byung-Hwan Rho
A time-saving and accurate technique for determining226Ra in groundwater and soil was examined, using high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS). The
technique was applied to the determination of226Ra in groundwater and soil samples and compared with the conventional liquid scintillation counting method. This technique
was capable of completing226Ra counting within 3 minutes, without the in-growth period to allow radon and its progeny to achieve secular equilibrium with
the parent226Ra. The detection limits of HR-ICP-MS for226Ra in groundwater and soil were 0.19 mBq·1−1 and 0.75 Bq·kg−1, respectively, which were about 10 times lower than that of the liquid scintillation counter. The results obtained from HR-ICP-MS
in groundwater and soil were in accordance with those of LSC within a relative error of about 13%.
Authors:Wuon-Shik Kim, Hyeon-Soo Kim, Ki-Hwan Kim, Yong-Uhn Kim, and Ki-Hyon Kim
Neutrons from a source are moderated by means of hydrogenous materials such as polyethylene (PE) or water to reduce the energy of fast neutrons and to increase the fluence rate of moderated neutrons. The rise-time and -ray pulse height spectrum from a PE moderated241Am-Be neutron-gamma (n-) mixed source were measured by using6Li-BC501 scintillation detector and pulse shape discriminator (PSD) system. The difference in rise-time between and neutron signals tumed out to be 18.5 ns for the6Li-BC501 (n-) spectrometer system. The figure of merit (FOM) for this separation was estimated to be 1.52, and this was compared with the published results. From this comparison, the6Li-BC501 system has much superior characteristics in (n-) separation to other detector systems. Two Compton edges at around 1.87 and 3.99 MeV which are produced by H(n,)D reaction and by the first excited state of12C* from Be(, n)12C* reaction were also investigated.
Authors:Wuon-Shik Kim, Hyon-Soo Kim, Jong-Youl Kim, Ki-Hwan Kim, Yong-Uhn Kim, and Kwang-Pill Lee
The 1.369 MeV -rays emitted from24Na
–+ after23Na(n,)24Na reaction were counted by high purity germanium (HPGe) detector and the half-life of24Na was derived. This process was simulated by Monte Carlo Neutron and Photon Transport Code (MCNP-4A).252Cf neutron source was moderated by a polyethylene (PE) cylinder to increase the cross section of neutron absorption reaction and to decrease the biological hazard. NaCl powder of 20 cm3 and 40 cm3 volume in cylindrical polypropylene capsules were irradiated by the neutrons passed through the moderator. MCNP-4A was used to determine the optimum size of PE moderator, to assume the realistic geometry of the HPGe detector, and to assume the absolute efficiencies of the detector. The count rates for 1.369 MeV -rays in the HPGe detector were calculated by MCNP-4A for 20 cm3 and 40 cm3 NaCl. The accumulated counts calculated tumed out to be higher than those actually measured by 31% with a relative error of 3%. The half-life of24Na measured within 4% and 1% for 20 cm3 and 40cm3 NaCl agrees with that of the reference. So, we can say that the result of MCNP-4A has about 30% of accuracy and 3% of precision in simulating the neutron activation analysis.
Authors:Hyun-Je Cho, Yong-Sam Chung, and Young-Jin Kim
A prompt gamma activation analysis facility has been constructed on the ST1 horizontal beam port at the HANARO research reactor, KAERI in 2003. The detector system consists of a high-purity Ge detector surrounded by BGO/NaI(Tl) scintillators as an annulus type to reject the Compton scattered photons. Detection sensitivity for boron was obtained from the prompt gamma-ray spectra of boric acid, B(OH)3, containing 0.1-65 μg boron. The net peak for the calculation of the boron concentration was obtained by eliminating the sodium 472 keV peak, involved in the boron 478 keV peak. The biological samples used are NIST SRMs such as Peach Leaves, Apple Leaves, Tomato Leaves, Spinach Leaves, Total Diet, Typical Diet, Oyster Tissue and Corn Bran, etc. The measured values for high boron concentration showed up to a 3% of the relative, but in a low concentration below 5 ppm, present values were higher than the certified ones.
Authors:Jin-Hong Lee, Joung-Myung Lim, Ki-Hyun Kim, Yong Chung, and Kil-Yong Lee
Instrumental neutron activation analysis was used to measure the concentrations of about 27 elements associated with airborne PM 10 samples that were collected from a roadside sampling station at a moderately polluted urban area of Taejon city, Korea. The magnitude of their concentrations was clearly distinguished and spanned over four orders. If compared in terms of enrichment factors, it was found that certain elements (e.g., As, Br, Cl, Sb, Se, and Zn) are enriched in PM 10 samples of the study site. The factor analysis indicated three factors with statistical significance, which may exert dominant controls on regulating the metal concentration levels in the study area.
Authors:Jong-Hwa Moon, Sun-Ha Kim, Yong-Sam Chung, and Young-Jin Kim
The k0-standardization method (k0-NAA) is known as one of the most remarkable progresses of the NAA with its many advantages. For the application of k0-NAA method at the NAA #1 irradiation position where the neutrons are well thermalized in the HANARO research reactor, KAERI,
Korea, the determination of the reactor neutron spectrum parameters such as α and f have been carried out. The measured values of α and f using the “Cd-ratio” triple monitor method were 0.127±0.022 and 1010±70, respectively. To evaluate the applicability of k0-NAA in our analytical system, the analysis of three kinds of SRMs was executed. The analytical results showed that the relative
error of most of the elements was less than 10% and the U-scores were within 2. It is turned out that the procedure of the k0-NAA in the HANARO research reactor is available for a practical application in the environmental fields.
Authors:Yong-Sam Chung, Jong-Hwa Moon, Sun-Ha Kim, Sang-Hoon Kang, and Young-Jin Kim
To enhance the applicability of the nuclear analytical technique in the field of industry and the environment, the inorganic
elemental content of the bottom ash from a municipal solid waste incinerator was determined by instrumental neutron activation
analysis. Bottom ash samples were monthly collected from an incinerator located at a metropolitan city in Korea, strained
through a 5 mm sieve, dried by an oven and pulverized by an agate mortar. The samples were irradiated at the NAA #1 irradiation
hole (thermal neutron flux: 2.92·1013 n·cm−2·s−1) in the HANARO research reactor of the Korea Atomic Energy Research Institute and the irradiated samples were measured by
a HP Ge gamma-ray spectrometer. Thirty-three elements including As, Cr, Cu, Fe, Mn, Sb and Zn were analyzed by an absolute
method. The quality control was conducted by a simultaneous analysis with NIST standard reference materials. The average concentrations
of the major elements such as Ca, Fe, Al, Na, Mg, K and Ti measured in the sample were 19.9%, 4.85%, 3.79%, 2.11%, 1.84%,
1.22% and 1.02%, respectively. In addition, the concentrations of the hazardous metals like Zn, Cu, Cr, Sb and As were 0.77%,
0.31%, 729 mg·kg−1, 116 mg·kg−1 and 22.2 mg·kg−1, respectively.
Authors:Dong-Yong Chung, Eung-Ho Kim, Young-Joon Shin, Jae-Hyung Yoo, and Jong-Duk Kim
The formation of precipitates by hydrazine was experimentally examined in the simulated high level liquid waste (HLLW), which was composed of 9 elements (Nd, Fe, Ni, Mo, Zr, Pd, Ru, Cs, Sr). Palladium was precipitated over 90% above 0.05M of hydrazine concentration and at 2M HNO3, while all of the other elements were hardly precipitated. The elements of Pd and Zr were precipitated 93% and 70% in the simulated solution in which the concentrations of Zr and Mo were decreased from 0.069M to 3.45·10–3M and 6.9·10–3M, respectively, and the acid concentration was decreased to about 0.5M after denitration. In a Pd solution of 0.5M and 2M HNO3, the precipitation yield of Pd increased with hydrazine concentration and reached over 98% at 0.1M. The precipitation yield of Pd at 0.5M HNO3 was higher than at 2M HNO3. The Pd precipitate, formed by adding hydrazine to an acidified solution, was an amorphous compound consisting of Pd, hydrazine, nitrate and hydrate.
Authors:Yong-Sam Chung, Jong-Hwa Moon, Kwang-Won Park, Sun-Ha Kim, Jin-Hong Lee, and Kil-Yong Lee
Instrumental neutron activation analysis was used for the analysis of 25 trace elements in airborne particulate matter (PM) for air pollution monitoring. For the collection of air samples, the Gent stacked filter unit low volume sampler and two types of Nuclepore polycarbonate filters were employed. Samples were collected at selected sampling dates in suburban and industrial regions of Daejon city in the Republic of Korea. Mass concentrations and black carbon of PM were measured, and enrichment factors were calculated. The results were used to describe the emission sources and their correlation patterns.
Authors:Dong-Yong Chung, Eung-Ho Kim, Young-Joon Shin, Jae-Hyung Yoo, Cheong-Song Choi, and Jong-Duk Kim
The decomposition rate of oxalate by hydrogen peroxide has been investigated by a KMnO4 titration method. The rate equation for decomposition of hydrogen peroxide in the aqueous phase is 1n([H2O2]/[H2O2]0)=–k1·t, where k1=0.2, for [H+]<2M, k1=0.2+0.34([H+]–2), for [H+]>2M. As the acidity increases over 2M, an acid catalysis effect appeard. The new rate equation proposed for the decomposition of oxalate by hydrogen peroxide is
The rate constant for decomposition of oxalate, k2, increased with nitric acid concentration and the effect of hydrogen ion concentration was expressed as k2=a[H+]n, where the values fora andn were a=1.54, n=0.3 at [H+]<2M, a=0.31, n=2.5 at [H+]>2M, respectively.