Encapsulation of Enhanced Waste from Molten Salt Oxidation in Geopolymer Matrix

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F26722445%3A_____%2F24%3AN0000115" target="_blank" >RIV/26722445:_____/24:N0000115 - isvavai.cz</a>

Result on the web

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DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Encapsulation of Enhanced Waste from Molten Salt Oxidation in Geopolymer Matrix

Original language description

During the operation of nuclear facilities, a high volume of Radioactive Organic Waste is generated. High prices for repositories force Radioactive Waste (RaW) producers to lower the volume of organic waste and several processing techniques are being developed. The processes range from the stabilisation of Radioactive Solid Organic Waste (RSOW) in the geopolymer matrix up to thermal treatment like incineration or newly developing Molten Salt Oxidation. During the MSO process, the solid organic waste is dosed, together with an oxidising medium, under the surface of the molten salt, where flameless oxidation occurs, and non-combustible materials are trapped in the molten salts. The molten salts can vary for each process, but Na2CO3 is mainly used for its low melting point, good obtainability, and low corrosion medium for the reactor components. During the previous experiments, the molten salt waste was found to be very hard to stabilise due to its water absorption and formation of hydrates. This feature caused an efflorescence and cracking of the samples with higher waste loading and in contact with water. To improve the encapsulation properties of the samples, the molten salts were chemically enhanced through a chemical reaction with a solution of Ca(OH)2 to form a more stable form. After the reaction, the decantate was mainly composed of Na2Ca(CO3)2.5H2O. In the previous experiments, the resulting samples had high mechanical strength but low workability and fast setting time, which prevented the use of more than 15 wt.% waste loading. Therefore, the recipe was improved by adding 5 wt.% of water into the mixture to improve the workability, and the mixing time was reduced from 10 to 5 minutes. The curing of the prepared samples was under controlled conditions, and the XRD analysis and mechanical stress test were performed to determine their physical and mechanical properties. The experiments were conducted with 5, 10, 15 and 20 wt.% of enhanced waste added into the matrix. Compressive strength tests demonstrated satisfactory mechanical performance for future use, but more research is needed to determine possible waste load increases and sample stability.

Czech name

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Czech description

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Type

O - Miscellaneous

CEP classification

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OECD FORD branch

20401 - Chemical engineering (plants, products)

Project

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Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2024

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů