Behavior of Radioactive Elements during Thermal Treatment of Nuclear Graphite Waste

YANG, Hee-Chul,EUN, Hee-Chul,LEE, Dong-Gyu,OH, Won-Zin,LEE, Kune-Woo Atomic Energy Society of Japan 2005 Journal of nuclear science and technology Vol.42 No.10

<P>Nuclear graphite waste retains various radioactive elements. This study investigated the behavior of the radioactive elements during a thermal treatment of the nuclear graphite waste, based on the thermodynamic equilibrium. Two typical thermal conditions were simulated: an excess air incineration and a hydrothermal oxidation. Tritium, <SUP>14</SUP>C and <SUP>36</SUP>Cl are expected to be present in the gas phase throughout the whole waste thermal systems. <SUP>133</SUP>Ba, <SUP>90</SUP>Sr, <SUP>22</SUP>Na, and <SUP>137</SUP>Cs were analyzed to be semi-volatile elements. Their behavior will be dependent upon the gaseous atmosphere as well as the operating temperature. Uranium species are expected to convert into a gas-phase UO<SUB>3</SUB> at temperatures above 1,000°C under excess air incineration atmospheres. Other radioactive elements such as <SUP>59</SUP>Ni, <SUP>60</SUP>Co, <SUP>141</SUP>Ce, <SUP>152</SUP>Eu and <SUP>241</SUP>Am are non-volatile at temperatures up to 1,200°C, regardless of the gaseous atmosphere being simulated.</P>

Realization of radioactive equilibrium in the KRISS radon chamber

Lee, M.S.,Park, T.S.,Lee, J.M. Pergamon Press ; Elsevier Science Ltd 2013 Applied radiation and isotopes Vol.81 No.-

The maintenance of radioactive equilibrium between radon and its decay products in a radon chamber is necessary to calibrate radon decay product monitors. In this study, the activity concentrations of radon decay products have been measured, and mosquito-repellent incense has been used to produce aerosol particles in the chamber. Filter papers with 8 μm pore size were used to collect aerosol in the chamber. The activity concentrations of radon decay products have been evaluated by the Modified Tsivoglou Method. The correction factors due to the differences in counting time requirements of the Modified Tsivoglou Method and the time delay between consecutive measurements have been determined. Finally, the radioactive equilibrium has been confirmed by applying the Bateman equation.

Study of atmosphere parameters of the IVV-2M reactor hall

Vasyanovich M.E.,Zhukovsky M.V.,Nazarov E.I.,Russkikh I.M. 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.11

The paper presents the results of a study of radioactive noble gases and from decay products in the atmosphere of the reactor hall of the research nuclear reactor IVV-2M. The distribution of short-lived 88Rb and 138Cs activity by sizes of aerosol particles was measured in the range of 0.5e1000 nm. It is shown that radioactive aerosols are characterized by three main modes with AMTD 2e3 nm, 7e15 nm and 400 nm. About 70% of aerosol activity is due to 88Rb. The equilibrium factor between 88Kr and 88Rb is 0.2 ± 0.1. The total concentration of aerosols particles was measured using an aerosol diffusion spectrometer. The value of unattached fraction of radioactive aerosols in the atmosphere of reactor hall IVV- 2M was f ¼ 0.15e0.25 at the average total aerosol particles concentration from 20,000 cm3 to 53,000 cm3.

A New Perspective- Analysis of Strontium-90

Hyuncheol Kim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

The radioactive contamination in the ocean has raised significant concern on the environmental impact among Asian and Pacific countries since the Fukushima Daiichi Nuclear Power Plant accident (Mar 11, 2011). The first step in determining the contamination by the radioactive material is monitoring anomalies of environmental radioactivity of interest. As a result, each country has its own environmental radioactivity surveillance program. Strontium-90 (half-life 28.8 y) is one of the radionuclides of high interest in the environment, owing to its high fission production rate and biological accumulation resulting from similar chemical behavior with calcium. The level of Strontium-90 in the seawater is very low, with a global average of about 1 mBq kg-1. Consequently, it requires large volume of seawater sample, typically ranging from 40 L to 60 L. The purification of 90Sr from seawater sample is challenging due to the high salinity and presence of stable Sr (about 7 ppm). Therefore, the conventional method for determining 90Sr is time-consuming and labor-intensive work. The author reported an advanced method, which is a more analyst-friendly and simpler method compared to the current method, for the determination of 90Sr in seawater. This method focuses on the separation of 90Y, which is equilibrium with 90Sr, utilizing a commercialized extraction resin. As a result, it takes less than 3 hours to determine 90Sr in 50 L of seawater sample and requires less labor. Additionally, this approach could be applied to the analysis of 90Sr in radioactive waste

A STUDY ON ADSORPTION AND DESORPTION BEHAVIORS OF ¹⁴C FROM A MIXED BED RESIN

Park, Seung-Chul,Cho, Hang-Rae,Lee, Ji-Hoon,Yang, Ho-Yeon,Yang, O-Bong Korean Nuclear Society 2014 Nuclear Engineering and Technology Vol.46 No.6

Spent resin waste containing a high concentration of $^{14}C$ radionuclide cannot be disposed of directly. A fundamental study on selective $^{14}C$ stripping, especially from the IRN-150 mixed bed resin, was carried out. In single ion-exchange equilibrium isotherm experiments, the ion adsorption capacity of the fresh resin for non-radioactive $HCO_3{^-}$ ion, as the chemical form of $^{14}C$, was evaluated as 11mg-C/g-resin. Adsorption affinity of anions to the resin was derived in order of $NO_3{^-}$ > $HCO_3{^-}{\geq}H_2PO_4{^-}$. Thus the competitive adsorption affinity of $NO_3{^-}$ ion in binary systems appeared far higher than that of $HCO_3{^-}$ or $H_2PO_4{^-}$, and the selective desorption of $HCO_3{^-}$ from the resin was very effective. On one hand, the affinity of $Co^{2+}$ and $Cs^+$ for the resin remained relatively higher than that of other cations in the same stripping solution. Desorption of $Cs^+$ was minimized when the summation of the metal ions in the spent resin and the other cations in solution was near saturation and the pH value was maintained above 4.5. Among the various solutions tested, from the view-point of the simple second waste process, $NH_4H_2PO_4$ solution was preferable for the stripping of $^{14}C$ from the spent resin.

감마선 분광법을 이용한 지하수 중의 ²²⁶Ra 분석

서범경,이길용,윤윤열,이근우,Seo, Bum-Kyoung,Lee, Kil-Yong,Yoon, Yoon-Yeol,Lee, Kune-Woo 한국분석과학회 2003 분석과학 Vol.16 No.1

시료 전처리가 필요 없는 감마선 분광분석법을 이용하여 지하수 중의 라듐 ($^{226}Ra$) 분석을 위한 측정법을 확립하였다. 방사평형된 딸핵종을 이용한 라듐의 분석 시 가장 문제가 되는 대기 중 라돈 딸핵종에 의한 바탕계수는 측정함 내부로 질소가스를 흘려주므로써 해결하였고, 라듐과 그 딸핵종들 사이의 방사평형 과정에서 생성된 라돈가스의 용기 외부로의 누출은 밀폐된 알루미늄 용기를 사용함으로써 방지할 수 있었다. 또한 측정용기 내부의 공기층에 의한 방사능 변화정도를 조사하기 위하여 임의로 공기층을 만들어 측정한 결과, 물 속에 녹은 라돈의 공기층으로의 발산에 의한 방사능 변화정도는 통상적인 측정오차인 5% 범위 이내였다. 측정 시 검출기 주위로 질소가스를 흘려줌으로서 대기 중 라돈 딸핵종에 의한 간섭을 제거하였고, 검출하한값을 0.02 Bq/L로 낮출 수 있었다. 이는 최근 US Environmental Protection Agency (EPA)에 의하여 제안된 지하수 중의$^{226}Ra$ Maximum Contaminant Level (MCL)인 0.74 Bq/L보다 충분히 작은 값으로서 감마선 분광법을 이용하여 지하수 중의 라듐을 방사능 농도를 정확히 결정할 수 있다는 것을 확인하였다. The measurement of radium ($^{226}Ra$) in the groundwater was established using ${\gamma}$-ray spectroscopy without sample preparation. The background interference by air borne radon daughter nuclides was reduced by $N_2$ gas flow into the counting chamber. Leakage of radon gas produced in the radioactive equilibrium with radium and its daughter nuclides was prevented by use of the air-tighted aluminium container. We investigated the effect of air layer in the counting container. Radioactivity variation due to emanation of radon into the air layer was within the counting error range 5%. When the nitrogen gas was flowed around the detector, peak counts of ${\gamma}$-rays from the daughters of airborne radon was decreased and detection limit was decreased to 0.02 Bq/L. The detection limit of detector was lower than 0.74 Bq/L, the $^{226}Ra$ Maximum Contaminant Level (MCL) in the groundwater proposed by US Environmental Protection Agency (EPA). It was confirmed that $^{226}Ra$ radioactivity in the groundwater could be determined by the ${\gamma}$-ray spectroscopy.

하나로를 이용한 중성자 이중 포획반응에 의한 166Ho 생성량 평가

김종범,최강혁 한국방사선산업학회 2015 방사선산업학회지 Vol.9 No.3

In this paper, production of 166Ho by double neutron capture from HANARO researchreactor was evaluated. This production approach provides 166Ho with high specific activity. 164Dyis transmuted into 165g+mDy by (n,γ) reaction, then 165g+mDy is transmuted into 166Dy by (n,γ)reaction. At the end of neutron irradiation, population of 166Dy atoms reaches highest point. And164Dy exists as a mixture with 165mDy, 165Dy, 166Ho and 165Ho at this point. To obtain 166Ho with highspecific activity, Ho isotopes from irradiated target is separated out. Then 166Ho decayed from166Dy is eluted at radioactive equilibrium state. At each step, the number of relevant nuclide iscalculated by the state equation. The neutron irradiation time for maximum 166Dy is calculated for283 hour. When 100 mg target of Dy2O3 (96.8% enriched 164Dy) is used, possible activity of 166Ho is3.54 Ci (1.31×1011 Bq). For separation efficiency of Dy/Ho is 99.99%, 166Ho/Ho is 0.62.

Molten Salt Oxidation of Ion-exchange Resins Doped with Toxic Metals and Radioactive Metal Surrogates

YANG, Hee-Chul,CHO, Yong-Jun,EUN, Hee-Chul,YOO, Jae-Hyung,KIM, Joon-Hyung Atomic Energy Society of Japan 2005 Journal of nuclear science and technology Vol.42 No.1

<P>Ion-exchange resins doped with toxic metals and radioactive metal surrogates were test-burned in a bench-scale molten salt oxidation (MSO) reactor system. The purposes of this study are to confirm the destruction performance of the two-stage MSO reactor system for the organic ion-exchange resin and to obtain an understanding of the behavior of the fixed toxic metals and the sulfur in the cationic exchange resins. The destruction of the organics is very efficient in the primary reactor. The primarily destroyed products such as carbon monoxide are completely oxidized in the secondary MSO reactor. The overall collection of the sulfur and metals in the two-stage MSO reactor system appeared to be very efficient. Over 99.5% of all the fixed toxic metals (lead and cadmium) and radioactive metal surrogates (cesium, cobalt, strontium) remained in the MSO reactor bottom. Thermodynamic equilibrium calculations and the XRD patterns of the spent salt samples revealed that the collected metals existed in the form of each of their carbonates or oxides, which are non-volatile species at the MSO system operating conditions.</P>

Research on the Reliability of Measurement of Natural Radioactive Nuclide Concentration of U-238

Cha Seok Ki,Joo Sun Dong,Lee Hoon,Kim Gee Hyun 대한방사선방어학회 2016 대한방사선방어학회 학술발표회 논문요약집 Vol.2016 No.12

The Transport Characteristics of ²³⁸U, ²³²Th, ²²⁶Ra, and ⁴⁰K in the Production Cycle of Phosphate Rock

Jung, Yoonhee,Lim, Jong-Myoung,Ji, Young-Yong,Chung, Kun Ho,Kang, Mun Ja The Korean Association for Radiation Protection 2017 방사선방어학회지 Vol.42 No.1

Background: Phosphate rock and its by-product are widely used in various industries to produce phosphoric acid, gypsum, gypsum board, and fertilizer. Owing to its high level of natural radioactive nuclides (e.g., $^{238}U$ and $^{226}Ra$), the radiological safety of workers who work with phosphate rock should be systematically managed. In this study, $^{238}U$, $^{232}Th$, $^{226}Ra$, and $^{40}K$ levels were measured to analyze the transport characteristics of these radionuclides in the production cycle of phosphate rock. Materials and Methods: Energy dispersive X-ray fluorescence and gamma spectrometry were used to determine the activity of $^{238}U$, $^{232}Th$, $^{226}Ra$, and $^{40}K$. To evaluate the extent of secular disequilibrium, the analytical results were compared using statistical methods. Finally, the distribution of radioactivity across different stages of the phosphate rock production cycle was evaluated. Results and Discussion: The concentration ratios of $^{226}Ra$ and $^{238}U$ in phosphate rock were close to 1.0, while those found in gypsum and fertilizer were extremely different, reflecting disequilibrium after the chemical reaction process. The nuclide with the highest activity level in the production cycle of phosphate rock was $^{40}K$, and the median $^{40}K$ activity was $8.972Bq{\cdot}g^{-1}$ and $1.496Bq{\cdot}g^{-1}$, respectively. For the $^{238}U$ series, the activity of $^{238}U$ and $^{226}Ra$ was greatest in phosphate rock, and the distribution of activity values clearly showed the transport characteristics of the radionuclides, both for the byproducts of the decay sequences and for their final products. Conclusion: Although the activity of $^{40}K$ in k-related fertilizer was relatively high, it made a relatively low contribution to the total radiological effect. However, the activity levels of $^{226}Ra$ and $^{238}U$ in phosphate rock were found to be relatively high, near the upper end of the acceptable limits. Therefore, it is necessary to systematically manage the radiological safety of workers engaged in phosphate rock processing.