Steam-Assisted Pyrolysis System for Decontamination and Volume Reduction of Radioactive Organic Waste

Kim

J Mater Cycles Waste Manag

et al. 2016

A stepwise thermal treatment process for the recovery of uranium phosphate from uranium-dissolved spent TBP was demonstrated. The pathway of the reactions involved in the thermal decomposition and oxidation processes of uranium-bearing spent TBP was established based on the results of thermogravimetric analyses. Relatively low-temperature pyrolysis is required to avoid the condensation of corrosive phosphoric acid via vaporization. Low-temperature pyrolysis residue was analyzed and found to be composed of pyrocarbon, phosphorus oxide (P 2 O 5 ) and two types of uranium phosphate (UP 2 O 7 and UP 4 O 12 ). Uranium pyrophosphate (UP 2 O 7 ) was recovered from the burning out of pyrocarbon in the pyrolysis residue after the dissolution removal of phosphorus oxide in water. A substantial recovery of uranium by the proposed stepwise thermal treatment method was successfully demonstrated by a treatment of pyrolysis residue from a benchscale low-temperature pyrolysis process.

Section: Demonstration Test Of the Stepwise Thermal Treatmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Recovery of uranium phosphate by a stepwise thermal treatment of uranium-bearing spent TBP

Kim

J Mater Cycles Waste Manag

et al. 2016

“…The decommissioning of a nuclear power plant (NPP) generates various types of waste and approximately 70% of the waste is reported to be concrete waste [1][2][3][4][5]. Concrete waste from NPPs is characterized by being heavy and volumetric, and thus requires a larger area for its disposal.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Changes in the Separation Process for the Performance of Recycled Cement Powder: A Comparison with a Previous Study for Radioactive Waste Immobilization

et al. 2022

Separation of hydrated cement paste from aggregate is a key technology to reduce the amount of radioactive concrete waste during the decommissioning process. If separated cement-paste portions can be recycled as a solidifying agent for other radioactive waste, the amount of radioactive concrete waste could be close to “zero”. A study was conducted to achieve circular economy in the area of concrete decommissioning and found it to be successfully used as a solidifying agent for immobilization of liquid radioactive waste. However, previous work used a process that requires large amounts of energy (heat treatment was applied to most of the concrete fraction) because the objective was to completely remove hydrated cement powder from the aggregate. In this work, the separation system was modified to increase energy efficiency (heat treatment was applied to separated powder only), but such a change decreased the surface area of the recycled cement powder due to a higher inclusion of aggregate powder. A relatively lower solution to binder ratio could have been achieved for the preparation of wasteform specimens, and as a result, a 28 day compressive strength of wasteform could have become higher, but the final leachability indices were lower than the results observed from previous work. The results from 28 day compressive strength, thermal cycling and 90 day leaching experiments met the acceptance criteria for wasteform, indicating that this modified system can also be used for immobilization of liquid radioactive waste to meet the “zero” production of concrete waste during the decommissioning of a nuclear power plant. It should be noted that accurate monitoring of aggregate content in recycled cement powder during production is important to maintain proper reactivity of recycled cement powder.

“…원자력 시설 건물은 철근콘크리트 구조로 되어 있어 원 전 해체 시에는 다량의 콘크리트 방사성 폐기물과 폐 토 양, 금속폐기물 등이 발생할 것으로 예상된다 Abdel Geleel and Mahmoud, 2012). 원전 해체로 인하여 발생되는 콘크리트 폐기물은 대부분 극저준위로 분류되지만, 전체 폐기물 중 콘크리트 폐기물이 60-80% 로 상당한 부분을 차지한다 (Sawada et al, 2005;Sasaki et al, 2009 (Cheon et al, 2018 (Malviya, 2006;Kim et al, 2020 (Shin, 2003;Kang et al, 2011 (Oh and Kim, 2002;Jang, 2003;Oh, 2005;Yeon et al, 2008 (Binkhorst and Cornelissen, 1998;Mun et al, 2017 Kim et al, 2005;Lee et al, 2013;Kim and Chung, 2019 Shi and Fernández-Jiménz, 2006;Saleh et al, 2019). 이러한 주요 화합물은 식 (1)-(2)와 같은 수화반응을 일으켜 시멘트의 강도를 발 현시킬 수 있다 (Kim and Jo, 1999).…”

unclassified

A Review on the Recycling of the Concrete Waste Generate from the Decommissioning of Nuclear Power Plants

Jeon

Lee

et al. 2021

Econ. Environ. Geol.

Globally, nuclear-decommissioning facilities have been increased in number, and thereby hundreds of thousands of wastes, such as concrete, soil, and metal, have been generated. For this reason, there have been numerous efforts and researches on the development of technology for volume reduction and recycling of solid radioactive wastes, and this study reviewed and examined thoroughly such previous studies. The waste concrete powder is rehydrated by other processes such as grinding and sintering, and the processes rendered aluminate (C 3 A), C 4 AF, C 3 S, and β-C 2 S, which are the significant compounds controlling the hydration reaction of concrete and the compressive strength of the solidified matrix. The review of the previous studies confirmed that waste concretes could be used as recycling cement, but there remain problems with the decreasing strength of solidified matrix due to mingling with aggregates. There have been further efforts to improve the performance of recycling concrete via mixing with reactive agents using industrial byproducts, such as blast furnace slag and fly ash. As a result, the compressive strength of the solidified matrix was proved to be enhanced. On the contrary, there have been few kinds of researches on manufacturing recycled concretes using soil wastes. Illite and zeolite in soil waste show the high adsorption capacity on radioactive nuclides, and they can be recycled as solidification agents. If the soil wastes are recycled as much as possible, the volume of wastes generated from the decommissioning of nuclear power plants (NPPs) is not only significantly reduced, but collateral benefits also are received because radioactive wastes are safely disposed of by solidification agents made from such soil wastes. Thus, it is required to study the production of non-sintered cement using clay minerals in soil wastes. This paper reviewed related domestic and foreign researches to consider the sustainable recycling of concrete waste from NPPs as recycling cement and utilizing clay minerals in soil waste to produce unsintered cement.