Dry active wastes (DAWs) are a type of combustible radioactive solid waste, which includes decontamination paper, protective clothing, filters, plastic bags, etc. generated from operating nuclear facilities and decommissioning projects. The volume of DAWs could be increased over time, disadvantage to higher disposal costs and space utilitization of disposal site. Additionally, incineration methods cannot be applied to DAWs, unlike general environmental waste, due to concerns about air pollution and the release of harmful chemicals with radioactive nuclides into the atmosphere. Recently, KAERI developed an alternative thermochemical process for reducing the volume of DAW, which involves a step-wise approach, including carbonization, chlorination, and solidification. The purpose of this process is to selectively separate the radioactive nuclides from carbonized DAWs that are less than clearance criteria, which can be disposed of as non-radioactive waste. In this research, we investigated the thermal decomposition characteristics of DAWs using nonisothermal thermogravimetric analysis, which was performed with different categorized wastes and heating conditions. As a result, the cellulose DAWs such as decontamination paper and cotton were thermally decomposed in three or four-step depending on the heating conditions. On the other hand, the hydrocarbon and rubber DAWs such as plastic bags and latex were thermally decomposed in one or two-step. Therefore, it could be suggested the thermochemical treatment conditions that minimize the decomposition of DAWs by controlling the reaction steps, and we will try to apply these results for cellulose type DAWs such as decontamination paper and cotton, which is generated majorly from the nuclear facilities in the future.

Various dry actives wastes (e.g., gloves, wipers, shoes, clothes) are generated during operation and maintenance of nuclear facilities. Among those, latex gloves gets interest because they contain both organic and inorganic compounds. CaCO3 is a common filler material for production of latex rubbers. Here, latex gloves were thermally treated in a closed vessel to separate the organic and inorganic compounds. Using the closed vessel is beneficial as it can prevent escape of any species, including radioactive nuclides in a real case, generated during the treatment. It was found that thermal decomposition of latex gloves occurred above 250°C. Latex gloves were decomposed to gas, liquid, and solid compounds. The gas product is thought to be volatile organic compounds (VOCs). The liquid product seems to be a mixture of oils and water. A CaCO3 phase was identified in the solid product, as expected. The VOCs can be easily separated at room temperature by purging in vacuum or inert atmosphere. The liquid-solid mixture can be separated by distillation. It is thought that gammaemitting nuclides, such as Cs-137, Sr-90, and Co-60, dominantly remain in the solid product. In the best situation, the solid product is the only subject to be transferred to final wasteform fabrication stream and thus volume of final waste can be reduced. Surrogates of contaminated latex gloves (containing Cs, Sr, and Co) were prepared and they were treated at 350°C in the closed vessel. How these contaminants behaves in this thermal process will be discussed in the presentation.