The Decontamination of the Surface Oxide Layer of Radioactively Contaminated Tank

Sia Hwang,Ki Joon Kang,Hee Reyoung Kim 한국방사성폐기물학회 2021 한국방사성폐기물학회 학술논문요약집 Vol.2021 No.11

Hot Isostatic Press Analysis for Cement Solidification of Sludge Wastes From Decommissioning of the Nuclear Power Plant

Sia Hwang,Hee Reyoung Kim 한국방사성폐기물학회 2021 한국방사성폐기물학회 학술논문요약집 Vol.2021 No.06

Disposal Assessment of ß Radionuclide-Removed Waste From Spent Resin Tank at a Wolsong Nuclear Power Plant

Sia Hwang,Jae Hoon Byun,Hee Reyoung Kim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

We conducted safety assessments for the disposal of spent resin mixed waste after the removal of beta radionuclides (3H, 14C) in a landfill facility. The spent resin tank of Wolsong nuclear power plant is generated by 8:1:1 weight ratio of spent ion exchange resin, spent activated carbon and zeolite. Waste in the spent resin tank was classified as intermediate-level radioactive waste due to 14C. Other nuclides such as 60Co and 137Cs exhibit below the low-level radioactive waste criteria. The techniques for separating mixed waste and capturing 14C have been under development, with a particular focus on microwave-based methods to remove beta radionuclides (3H, 14C) from spent activated carbon and spent resin within the mixed waste. The spent resin and activated carbon within the waste mixture exhibits microwave reactivity, heated when exposed to microwaves. This technology serves as a means to remove beta isotopes within the spent resin, particularly by eliminating 14C, allowing it to meet the low-level radioactive waste criteria. Using this method, the waste mixture can meet disposal requirements through free water and 3H removal. These assessments considered the human intrusion scenarios and were carried out using the RESRAD-ONSITE code. The institutional management period after facility closure is set at 300 years, during which accidental exposures resulting from human intrusion into the disposal site are accounted for. The assessment of radiation exposure to intruders in a landfill facility included six human intrusion scenarios, such as the drilling scenario, road construction scenario, post-drilling scenario, and post-construction scenario. Among the six human intrusion scenarios considered, the most conservative assessment about annual radiation exposure was the post-drilling scenario. In this scenario, human intrusion occurs, followed by drilling and residence on the site after the institutional management period. We assumed that some of the vegetables and fruits grown in the area may originate from contaminated regions. Importantly, we confirmed that radiation doses resulting from post-institutional management period human intrusion scenarios remain below 0.1 mSv/y, thus complying with the annual dose limits for the public. This research underscores the importance of effectively managing and securing radioactive waste, with a specific focus on the safety of beta radionuclide-removed waste during long-term disposal, even in the face of potential human intrusion scenarios beyond the institutional management period.

쌀 종류에 따른 식혜의 품질특성 및 항산화 활성

황은선(Eun-Sun Hwang),손은명(Eun Myeong Shon),이시아(SiA Lee) 한국식품영양과학회 2020 한국식품영양과학회지 Vol.49 No.6

본 연구에서는 3가지 종류의 쌀(백미, 현미 및 가바현미)을 이용하여 식혜를 제조하고 식혜의 이화학적 품질, 아미노산 함량 및 항산화 활성을 시판 식혜 3종과 비교하였다. 백미로 제조한 식혜의 가용성 고형분은 17.0°Brix로 현미나 가바현미로 제조한 식혜와 시판 식혜에 비해 높았다. 백미로 제조한 식혜의 pH는 5.31이었고, 현미와 가바현미로 제조한 식혜의 pH는 5.44와 5.46으로 백미 식혜에 비해 다소 높게 나타났다. 백미로 제조한 식혜의 sucrose 함량은 현미와 가바현미로 제조한 식혜보다 높았고, home-made 식혜는 시판 식혜에 비해 glucose 함량이 3.96~4.40배 높았다. 식혜에서 20종의 아미노산을 분석하였고 제조한 식혜가 시판식혜에 비해 GABA와 필수아미노산 함량이 높았고, 특히 현미와 가바현미로 제조한 식혜는 백미로 제조한 식혜에 비해 높은 GABA 함량을 나타냈다. 현미와 가바현미로 제조한 식혜에서 총 폴리페놀 및 총 플라보노이드 함량이 높았다. 항산화 활성은 시판 식혜에 비해 제조한 식혜에서 높았고, 백미< 현미< 가바현미의 순으로 높게 나타났다. 이상의 결과를 통해 백미로 제조한 식혜나 시판 식혜에 비해 현미나 가바현미로 제조한 식혜는 GABA를 비롯한 아미노산, 총폴리페놀 및 플라보노이드 함량이 높고 항산화 활성이 우수하여 기능성 식혜 제조의 원료로서의 가능성이 있는 것으로 사료된다. Sikhye was prepared using three types of rice [milled rice, brown rice, and gamma-aminobutyric acid (GABA) brown rice], and the physicochemical quality, amino acid content, and antioxidant activity of Sikhye were compared with those of three commercially available Sikhye. The soluble solid content of Sikhye made with white rice was higher than that of Sikhye made with brown rice or GABA rice and was higher than that of commercial Sikhye. The glucose content was 3.96∼4.40 times higher than that of commercial Sikhye. Sikhye made with brown rice or GABA rice showed higher GABA and essential amino acid contents than Sikhye made with white rice or commercial Sikhye. The total polyphenol and flavonoid contents of Sikhye prepared from brown rice or GABA rice were higher than those of white rice or commercial Sikhye. The 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical scavenging activity was higher in homemade Sikhye than in commercial Sikhye, and antioxidant activity was in the order of white rice < brown rice < GABA rice. Based on these results, Sikhye made with brown rice or GABA rice had higher amino acid, total polyphenol and flavonoid contents, and superior antioxidant activity compared to Sikhye made with white rice and commercial Sikhye.

The Characteristics of Solidified Sludge According to the Distribution of Ferro Frit Powder in Sludge

Ki Joon Kang,Sia Hwang,Hee Reyoung Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

In nuclear power plant, there were many contaminated tanks dispose of radioactive fluid waste. These tanks are made of stainless-steel, and corrosion can occur when tanks are exposed to radioactive fluid waste containing moisture for a long time. Therefore, those sludge waste including radionuclide should be collected, solidified, and disposed of. If sludge can be melted, sludge can be easily solidified. However, melting points of sludge components (Fe2O3, NiO, Cr2O3) are very high as 1565, 1955, and 2435 , respectively. Therefore, melting sludge is difficult. If a solidification auxiliary material such as cement or asphalt is used to help solidify, solidification can easily occur, but cement and asphalt are vulnerable to heat. Vitrification using glass material can be solidification method, but the waste loading ratio of glass material is higher than 50%. High waste loading ratio is weakness in terms of volume reduction of waste. In this study, ferro frit powder (Na2O, K2O, CaO, Al2O3, B2O3, SiO2, ZnO) is used as solidification auxiliary material. When ferro frit powder mixed with sludge material are melted in sludge material, melted ferro frit powder can stick sludge material and can solidify sludge material without melting. Sludge can be solidified by using ferro frit powder with a smaller waste loading ratio than the vitrification method. However, since the waste loading ratio of the solidification auxiliary material is small, if ferro frit powder is not uniformly distributed between sludge powder, solidification may not be performed properly. Although the mixing ratio between sludge and ferro frit in solidified sludge is same, when the distribution of ferro frit powder in sludge is non-homogeneous, the difference in chemical and physical characteristics as compressive strength and leaching resistance can be observed in solidified sludge. As the ferro frit mixing ratio in the site where ferro frit exists was relatively high, the melting point of the mixed powder (sludge+ferro frit) decreased, and the mixed powder could not maintain its shape and melted. In the case of the area where ferro frit does not exist, since only the stainless-steel oxide sludge exists, sludge was not melted, and the shape was maintained. However, it was confirmed that the leaching resistance was lowered by visually observing the color change of the leachate within a short period of time (about 2 hours) when solidified sludge was immersed in the leachate.

The Solidification of Radioactive Sludge Powder Based on Metallic Oxide and Ferro Frit Powder by Hot Isostatic Pressing

Ki Joon Kang,Sia Hwang,Hee Reyoung Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1

The mixing powder of vitrification material and metallic oxide sludge was solidified by hot isostatic press method and was tested to check whether the solidified waste disposal acceptance criteria were met or not. From various contaminated tank in nuclear power plants, and other nuclear energy facilities, radioactive sludge based on metallic oxide can be generated. The most of tank consist of stainless steel can be oxidated by the long-term exposure on oxygen and moisture, and then can be made sludge layer based on metallic oxide on the inner wall of contaminated tank. Radioactive sludge waste should be solidified and disposed. Melting and hardening is the most basic method for solidification. The melting points of metallic oxide of stainless steel as Fe3O4, NiO, Cr2O3 are 1597, 1955, 2435, respectively. Those are very high temperature. To melt these metallic oxides, a furnace capable of raising the temperature to a very high temperature is required, which requires a lot of thermal energy, which may lead to an increase in disposal cost. Therefore, it is necessary to lower the melting point and solidify non-melted metallic oxide powder by adding vitrifying material powder as Na2O, SiO2, B2O3. The more vitrification material is added, the easier it is to solidify the sludge based on metallic powder at a low temperature, but there is a problem in that the total waste volume increases due to the addition of vitrification material. In this study, the mixing ratio and temperature conditions that can fix the sludge while adding a minimum amount of vitrification material will be confirmed. Mixing ratio conditions of the vitrification material and sludge powder are 10:90, 15:85, 20:80, 25:75. To fix the metallic oxide sludge by melting only the vitrification material without completely melting the metallic oxide, compression by external pressure is required. Therefore, the HIP (Hot Isostatic Pressing) method was used to solidify the metallic oxide sludge by simultaneously heating and pressurizing it. Because the softening points of most of vitrification based on Na2O, SiO2, B2O3 are ranged from 800 to 1000, temperature conditions are 800, 900, 1000. Since the compressive strength for disposing of the solidified materials was 3.4 MPa, the maximum pressure condition was set to 5000 psi (about 34 MPa), which is 10 times 3.4 MPa. And optimal mixing ratio, temperature, pressure conditions that meet the solidified waste disposal acceptance criteria will be found.

Reinforce on Leaching Resistance of Solidified Cement by Hot Isostatic Press

Ki Joon Kang,Sia Hwang,Hee Reyoung Kim 한국방사성폐기물학회 2021 한국방사성폐기물학회 학술논문요약집 Vol.2021 No.06

베이킹 시간에 따른 쿠키의 품질 특성, 아크릴아마이드 함량 및 항산화 활성

황은선(Eun-Sun Hwang),이시아(SiA Lee) 한국식품영양과학회 2021 한국식품영양과학회지 Vol.50 No.3

일정한 배합비로 쿠키 반죽을 제조한 후, 오븐에 굽는 시간을 12, 16, 20 및 24분으로 달리하여 쿠키를 완성하고 품질 특성, 아크릴아마이드 함량 및 항산화 활성을 측정하였다. 수분함량은 12분 동안 구운 쿠키에서 4.24%로 가장 높았고, 굽는 시간이 16분에서 24분까지 증가함에 따라 3.52%에서 1.95%로 감소하였다. 조단백질 및 조지방은 각각 1.11~1.15%와 22.15~22.63%였고, 조회분 함량은 0.46~0.47%로 굽는 시간에 따른 통계적인 차이는 없는 것으로 나타났다. 당도의 경우 12~20분 동안 구운 쿠키는 3.9°Brix였고, 24분 동안 구운 쿠키는 3.8°Brix로 약간 감소하였다. pH는 12분 동안 구운 쿠키에서는 pH 6.62로 가장 높았고, 굽는 시간이 길어질수록 pH는 감소하여 pH 5.79까지 낮아졌다. 쿠키의 명도(L<SUP>*</SUP>)와 황색도(b<SUP>*</SUP>)는 가열시간에 비례하여 감소하였고, 적색도(a<SUP>*</SUP>)와 갈색화 지표는 굽는 시간이 길어짐에 따라 증가하였다. 제조한 쿠키의 아크릴아마이드 함량은 12분 동안 구운 시료 1 g당 34.67 ng이었고, 굽는 시간이 16분 및 24분으로 길어짐에 따라 각각 57.91 및 198.55 ng으로 증가하여 갈색화 지표와 아크릴아마이드 함량은 비례관계에 있음을 확인하였다. 쿠키의 굽는 시간이 증가함에 따라 총 폴리페놀과 총 플라보노이드 함량은 12분 동안 가열하여 제조한 쿠키에 비해 각각 1.11~2.65배 및 1.07~1.24배 증가하였다. 쿠키의 굽는 시간이 길어질수록 항산화 활성의 증가와 함께 아크릴아마이드 생성도 높아짐을 확인하였다. 따라서 쿠키 제조 시 항산화 물질의 함량, 항산화 활성 및 아크릴아마이드 생성을 고려한 적절한 시간 설정이 필요할 것으로 사료된다. A uniform cookie dough having the same ingredients was put in an oven and baked for 12, 16, 20 and 24 min. The quality characteristics, acrylamide content, and antioxidant activity were subsequently determined. Highest moisture content (4.24%) was obtained in cookies baked for 12 min, and was observed to decrease from 3.52% to 1.95% as baking time increased from 16∼24 min. Crude protein, crude fat, and ash contents were not statistically different according to baking time. Cookies baked for 12 min had the highest pH 6.62, which then decreased to 5.79 with increasing time. The L<SUP>*</SUP> and b<SUP>*</SUP> values of the cookies were observed to proportionately decrease with increasing baking time, whereas the a<SUP>*</SUP> value and browning index showed time-dependent increase. With increasing baking time of cookies, the total polyphenol and total flavonoid contents increased from 1.11 to 2.65 times and 1.07 to 1.24 times, respectively, as compared to cookies prepared by baking for 12 min. We further confirmed that the longer the baking time of the cookies, higher was the antioxidant activity and production of acrylamide. Taken together, our results indicate the necessity to set an appropriate time for baking cookies, by considering the content of antioxidants, antioxidant activity, and acrylamide production for the duration.

Vitrification Analysis of Washing Sludges From Stainless Steel Tank Using Hot Isostatic Press & High-Temperature Furnace

Jaeho Lee,Hee Reyoung Kim,Ki Joon Kang,Sia Hwang 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1

The optimum vitrification conditions of the radioactive waste using high-temperature furnace and HIP (Hot Isostatic Press) were studied for the successful reduction of the solidification volume, radioactive level, satisfying the disposal criteria such as leaching rate and compressive strength. Vitrification is receiving attention for the solidification disposal of intermediate and low-level radioactive wastes for its chemical-physical stability and leachability. Its principle is to trap the radioactive material in a fixed structure of the glass type materials, such as Boron Trioxide, Silicon Dioxide and Phosphorus Pentoxide. Sludge targeted in this study is assembly of materials while sludge is stored in the stainless-steel tank before disposal, which consists of Fe3O4 (14.9wt%), Fe2O3 (3.8wt%), and Cr2O3 (6.3wt%), cement paste (25wt%) and detergent/shower sludge (50wt%). The detergent/shower sludge generated from the washing the clothes that were worn during the work at the laboratory and nuclear power plant contains organic materials that are vulnerable to chemical reactions, therefore, immobilization of organic material by the incinerating step, which can also immobilize the radioactive substance, was applied. Its composition – containing Cs-133 and Co-59 substitution for Cs-134 and Co-60 that are radioactive – was analyzed by XRD before and after the mineralization of the sludge using high temperature furnace in different temperature, to identify the remaining element and the features of the mineralized sludge. Targeted sludge was vitrificated using Hot Isostatic Press in with different pressure and temperature conditions, to find out the optimum vitrification conditions. Vitrificated waste was evaluated in many aspects - leaching evaluation following ANS16.1, compressive strength evaluation of 3.44 MPa (waste disposal criteria), volume reduction before and after the sequence.