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Kim B, Manchuri AR, Oh GT, Lim Y, Son Y, Choi S, Kang M, Jang J, Ha J, Cho CH, Lee MW, Lee DS. Experimental analysis and prediction of radionuclide solubility using machine learning models: Effects of organic complexing agents. JOURNAL OF HAZARDOUS MATERIALS 2024; 469:134012. [PMID: 38492397 DOI: 10.1016/j.jhazmat.2024.134012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/02/2024] [Accepted: 03/10/2024] [Indexed: 03/18/2024]
Abstract
Radioactive wastes contain organic complexing agents that can form complexes with radionuclides and enhance the solubility of these radionuclides, increasing the mobility of radionuclides over great distances from a radioactive waste repository. In this study, four radionuclides (cobalt, strontium, iodine, and uranium) and three organic complexing agents (ethylenediaminetetraacetic acid, nitrilotriacetic acid, and iso-saccharic acid) were selected, and the solubility of these radionuclides was assessed under realistic environmental conditions such as different pHs (7, 9, 11, and 13), temperatures (10 °C, 20 °C, and 40 °C), and organic complexing agent concentrations (10-5-10-2 M). A total of 720 datasets were generated from solubility batch experiments. Four supervised machine learning models such as the Gaussian process regression (GPR), ensemble-boosted trees, artificial neural networks, and support vector machine were developed for predicting the radionuclide solubility. Each ML model was optimized using Bayesian optimization algorithm. The GPR evolved as a robust model that provided accurate predictions within the underlying solubility patterns by capturing the intricate relationships of the independent parameters of the dataset. At an uncertainty level of 95%, both the experimental results and GPR simulated estimations were closely correlated, confirming the suitability of the GPR model for future explorations.
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Affiliation(s)
- Bolam Kim
- Department of Environmental Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea
| | - Amaranadha Reddy Manchuri
- Department of Environmental Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea
| | - Gi-Taek Oh
- Department of Chemical Engineering, Keimyung University, 1095 Dalgubeol-daero, Dalseo-gu, Daegu 42601, Republic of Korea
| | - Youngsu Lim
- Department of Environmental Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea
| | - Yuhwa Son
- LILW Technology Team, Korea Radioactive Waste Agency, 19 Chunghyochun-gil, Gyeongju-si, Gyeongsangbuk-do 38062, Republic of Korea
| | - Seho Choi
- LILW Technology Team, Korea Radioactive Waste Agency, 19 Chunghyochun-gil, Gyeongju-si, Gyeongsangbuk-do 38062, Republic of Korea
| | - Myunggoo Kang
- LILW Technology Team, Korea Radioactive Waste Agency, 19 Chunghyochun-gil, Gyeongju-si, Gyeongsangbuk-do 38062, Republic of Korea
| | - Jiseon Jang
- HLW Technology Development Institute, Korea Radioactive Waste Agency, 174 Gajeong-ro, Yuseong-gu, Daejeon 34129, Republic of Korea
| | - Jaechul Ha
- LILW Technology Team, Korea Radioactive Waste Agency, 19 Chunghyochun-gil, Gyeongju-si, Gyeongsangbuk-do 38062, Republic of Korea
| | - Chun-Hyung Cho
- HLW Technology Development Institute, Korea Radioactive Waste Agency, 174 Gajeong-ro, Yuseong-gu, Daejeon 34129, Republic of Korea
| | - Min-Woo Lee
- Department of Chemical Engineering, Keimyung University, 1095 Dalgubeol-daero, Dalseo-gu, Daegu 42601, Republic of Korea
| | - Dae Sung Lee
- Department of Environmental Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea.
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Cho S, Kim HK, Kim TH, Cha W, Cho HR. Thermodynamic Studies on the Hydrolysis of Trivalent Plutonium and Solubility of Pu(OH) 3(am). Inorg Chem 2022; 61:12643-12651. [PMID: 35921136 DOI: 10.1021/acs.inorgchem.2c01590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The temperature-dependent reaction properties of actinide elements are of particular interest in the safety assessment of high-level radioactive waste (HLRW) disposal systems. In this study, the hydrolysis of Pu(III) and the solubility of Pu(OH)3(am) were investigated at various temperatures (10-40 °C) in 0.1 M NaClO4. A strong reducing condition for maintaining the oxidation state of Pu(III) while slowly increasing the pH of the solution was realized by electrolysis. The formation constants of the first hydrolysis species, log *β1', and the solubility products of Pu(OH)3(am), log *Ks,0', at 10, 17, and 40 °C were experimentally determined using spectrophotometry, laser-induced breakdown detection, and radiometry. The enthalpy and entropy changes for these reactions were estimated using the van't Hoff equation. The first hydrolysis of Pu(III) is endothermic (ΔrHm° = 34.10 ± 4.48 kJ mol-1), and the dissolution of Pu(OH)3(am) is exothermic (ΔrHm° = -294.29 ± 23.05 kJ mol-1) with negative entropy changes. These thermodynamic data will contribute to improving the reliability of the safety assessment of HLRW disposal facilities and understanding the geochemical behavior of Pu under reducing or anoxic aqueous conditions at elevated temperatures.
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Affiliation(s)
- Sangki Cho
- Nuclear Chemistry Research Team, Korea Atomic Energy Research Institute, Daejeon 34057, Republic of Korea.,Department of Radiochemistry and Nuclear Nonproliferation, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Hee-Kyung Kim
- Nuclear Chemistry Research Team, Korea Atomic Energy Research Institute, Daejeon 34057, Republic of Korea
| | - Tae-Hyeong Kim
- Nuclear Chemistry Research Team, Korea Atomic Energy Research Institute, Daejeon 34057, Republic of Korea
| | - Wansik Cha
- Nuclear Chemistry Research Team, Korea Atomic Energy Research Institute, Daejeon 34057, Republic of Korea
| | - Hye-Ryun Cho
- Nuclear Chemistry Research Team, Korea Atomic Energy Research Institute, Daejeon 34057, Republic of Korea.,Department of Radiochemistry and Nuclear Nonproliferation, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
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