The Technical Development for Reuse of Radioactive Concrete Waste Generated by Dismantling of Nuclear Facilities

As part of a fundamental study for the reuse and recycling of contaminated concrete wastes generated by dismantling a research reactor, KAERI has been developing separation technology which recovers for reuse and recycling aggregates from the dismantled concrete. The separation is based on a thermal treatment followed by mechanical processes such as a crushing, milling and sieving. The separation test of concrete waste (i.e., light concrete and heavy concrete) was performed using radioisotope (⁶⁰Co). The distribution of ⁶⁰Co has been investigated for the effects of the heating temperature, washing and aggregate size such as gravel, sand and paste using a mechanical and thermal unit process. The experimental results showed that most of the ⁶⁰Co nuclide could be removed from the gravel, sand aggregate and concentrated into a paste. Especially, we found that the heating temperature played an important role in separating the ⁶⁰Co nuclide from the concrete waste. The optimum heating temperature for the removal of the ⁶⁰Co was about 500°C. According to an increase of the heating temperature, the amount of transferred ⁶⁰Co to the paste linearly increased because the bond between the aggregate and paste matrix is reduced. Contamination of concrete is mainly concentrated in the porous paste and not in the dense aggregate such as the gravel and sand. Concrete can be separated into contaminate and clean parts by means of a unit process based on a crushing, heating, milling and sieving at over 1mm. Through experiments, the clean aggregate can be reused and recycled by up to 70%. By thermally and mechanically separating this concrete waste from the clean dense aggregate particles, a considerable volume reduction can be reacted.