Ordinary-Portland-cement solidification of Cs-137 contaminated electric arc furnace dust from steel production industry in Thailand

Abstract

The cementation was used to immobilize the Cs-137 contaminated electric arc furnace dust (EAFD). Various mixing recipes were used to prepare the EAFD-cement waste form specimens. The strength test, the ANSI/ANS-16.1 leaching test and the immersion test were performed to judge whether the cured specimens satisfy the Radwaste disposal requirements. The strengths of all specimens were higher than the acceptable limit (3.45 MPa). The specimen's strength depended on the EAFD content, the water-to-binders ratio, and the curing time. Moreover, it could be affected by the leaching of the cement and EAFD components. The leaching results showed that the Cs-137 could be totally leached after ending of the test. There is a positive correlation between the quantity of Cs-137 in the leachate and the leachate pH. The Cs-137 leachability index (LI) decreased as the EAFD content and the ratio increased. The LI values ranged from 5.9 to 6.4. The Cs-137 leaching from the specimens could be controlled by the diffusion or the surface wash-off, depending on the recipes used. Additionally, the Cs-137 leaching might be controlled by multiple mechanisms. The findings reasonably recommend that the recipe with the ratio of 0.40 and 40 % EAFD could be used for the EAFD immobilizing.

Keywords

• EAFD
• Cs-137
• Radwaste
• Accidental melting
• Conditioning
• Leaching