• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.581-588
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• 2020

The membrane fouling is an important problem for FO applied to the radioactive wastewater treatment. The FO fouling characteristics for simulated radioactive wastewater treatment was investigated. On-line cleaning by deionized (DI) water and external cleaning by ultrasound and HCl were applied for the fouled membrane. The effectiveness and foulant removing amount by each-step cleaning were evaluated. The membrane fouling was divided into three stages. Co(II), Sr(II), Cs(I), Na(I) were all found deposited on both active and support layers of the membrane surface, resulting in membrane surface became rougher and more hydrophobic, which increased membrane resistance. On-line cleaning by DI water recovered the water flux to 69%. HCl removed more foulants than ultrasound.

• Nuclear Engineering and Technology
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• v.50 no.6
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• pp.886-889
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• 2018

This article presented two-staged chemical precipitation for radioactive wastewater decontamination by using chemical agents. The total amount of radioactive wastewater was $35m^3$, and main radionuclides were Cs-137, Cs-134, and Co-60. Initial radioactivity concentration of the liquid waste was 2264, 17, and 9 Bq/L for Cs-137, Cs-134 and Co-60, respectively. Potassium ferrocyanide, nickel nitrate, and ferrum nitrate were selected as chemical agents at high pH levels 8-10 according to the laboratory jar tests. After the process, radioactivity was precipitated as sludge at the bottom of the tank and decontaminated clean liquid was evaluated depending on discharge limits. By this precipitation method decontamination factors were determined as 66.5, 8.6, and 9 for Cs-137, Cs-134, and Co-60, respectively. By using the potassium ferrocyanide, about 98% of the Cs-137 was removed at pH 9. At the bottom of the tank, radioactive sludge amount from both stages was totally $0.98m^3$. It was transferred by sludge pumps to cementation unit for solidification. By chemical processing, 97.2% of volume reduction was achieved. The potassium ferrocyanide in two-staged precipitation method could be used successfully in large-scale applications for removal of Cs-137, Cs-134, and Co-60.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.738-745
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• 2019

Coprecipitation using hydrous ferric oxide (HFO) has been effectively used for the removal of radionuclides from radioactive wastewater. This work studied the dynamic behavior of HFO floc formation during the neutralization of acidic ferric iron in the presence of several radionuclides by using a photometric dispersion analyzer (PDA). Then the coagulation-flocculation system using HFO-anionic poly acrylamide (PAM) composite floc system was evaluated and compared in seawater and distilled water to find the effective condition to remove the target nuclides (Co-60, Mn-54, Sb-125, and Ru-106) present in wastewater generated in the severe accident of nuclear power plant like Fukushima Daiichi case. A ferric iron dosage of 10 ppm for the formation of HFO was suitable in terms of fast formation of HFO flocs without induction time, and maximum total removal yield of radioactivity from the wastewater. The settling time of HFO flocs was reduced by changing them to HFO-PAM composite floc. The optimal dosage of anionic PAM for HFO-anionic PAM floc system was approximately 1-10 ppm. The total removal yield of Mn-54, Co-60, Sb-125, Ru-106 radionuclides by the HFO-anionic PAM coagulation-flocculation system was higher in distilled water than in seawater and was more than 99%.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.391-396
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• 2006

When radioactive wastewater was solidified treatment by cement, the drying rate of cement and the volume reduction ratio was decreased because of boric acid component in the wastewater. In order to supplement the demerit, effects of paraffin wax investigated in this study. Paraffin wax has a hydrophobic properties and a low affinity with inorganic materials. When the radioactive wastewater was tested by a small of wax, the compressive strength of solidified waste are decreased Therefore boric acid in radioactive wastewater are first treated by alkali salt and coated by the stearic acid. During the solidification step, The amount of paraffin wax addition get the result that the compressive strength of solidification with cement was the same as that with paraffin wax. The leaching properties of radioactive waste solidified was the same CFL (cumulative fraction leached), PR (penetration rate), effective diffusivity if paraffin wax content in solidified waste was 20% or 25%.

• Maritime Security
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• v.2 no.1
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• pp.125-149
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• 2021

Even 10 years after the Fukushima nuclear disaster, Japan has yet to solve the problems emerging from generating contaminated water every day. Japan has unilaterally decided to release nuclear wastewater in the sea despite Korea's concerns about safety as their radioactive water storage tanks reach the limits. Despite Korea's response, Japan is still preparing to discharge nuclear wastewater without fulfilling its obligations under the United Nations Convention on the Law of the Sea. There are concerns about marine pollution caused by the radioactive materials from nuclear wastewater and invading Korea's maritime sovereignty. In particular, it is impossible to reverse the effects of environmental pollution, so plans to discharge radioactive water must be prevented unless immediate safety is guaranteed. This study proposes Korea's response strategy to resolve the conflict between the two countries due to plans to release contaminated water. Korea should respond to Japan's release of nuclear wastewater in the sea in various ways through cooperation with Japan, provisional measures, and cooperation with neighboring countries.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.05a
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• pp.399-400
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• 2018

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.516-522
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• 2023

The co-precipitation process plays a key role in the decontamination of radionuclides from low and intermediate levels of liquid waste. For that reason, the removal of Cs ions from waste solution by the co-precipitation method was carried out. A simulated liquid waste (¹³³Cs) was prepared from a 0.1 M CsCl solution, while wastewater generated by washing steel ash served as a representative of radioactive cesium solution (¹³⁷Cs). By co-precipitation, potassium ferrocyanide was applied for the adsorption of Cs ions, while nickel nitrate and iron sulfate were selected for supporting the precipitation. The amount of residual Cs ions in the CsCl solution after precipitation and filtration was determined by ICP-OES, while the radioactivity of ¹³⁷Cs was measured using a gamma-ray spectrometer. After cesium removal, the amount of cesium appearing in both XRD and SEM-EDS was analyzed. The removal efficiency of ¹³³Cs was 60.21% and 51.86% for nickel nitrate and iron sulfate, respectively. For the ash-washing solution, the removal efficiency of ¹³⁷Cs was revealed to be more than 99.91% by both chemical agents. This implied that the co-precipitation process is an excellent strategy for the effective removal of radioactive cesium in waste solution treatment.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4441-4448
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• 2022

The electrochemical oxidation process has been widely studied in the field of wastewater treatment for the decomposition of organic materials through oxidation using ·OH generated on the anode. Pt anode electrodes with high durability and long-term operability have a low oxygen evolution potential, making them unsuitable for electrochemical oxidation processes. Therefore, to apply Pt electrodes that are suitable for long-term operation and large-scale processes, it is necessary to develop a new method for improving the decomposition rate of organic materials. This study introduces a method to improve the decomposition rate of organic materials when using a Pt anode electrode in the electrochemical oxidation process for the treatment of organic decontamination liquid waste. Electrochemical decomposition tests were performed using sodium dodecylbenzenesulfonate (SDBS) as a representative organic material and a Pt mesh as the anode electrode. Y₂O₃ particles were introduced into the electrolytic cell to improve the decomposition rate. The decomposition rate significantly improved from 21% to 99%, and the current efficiency also improved. These results can be applied to the electrochemical oxidation process without additional system modification to enhance the decomposition rate and current efficiency.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.11a
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• pp.482-483
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• 2018

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.11a
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• pp.355-356
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• 2018