As a result of the Fukushima Daiichi Nuclear Power Plant accident on March 11, 2011 in Japan radioactive nuclides, primarily Cs-134 and Cs-137 were released, contaminating municipal solid waste and sewage sludge in the area. Although stabilizing the waste and reducing its volume is an important issue differing from Chernobyl nuclear power plant accident, secondary emission of radioactive nuclides as a result of any intermediate remediation process is of concern. Unfortunately, there is little research on the behavior of radioactive nuclides during waste treatment. This study focuses on waste incineration in an effort to clarify the behavior of radioactive nuclides, specifically, refuse-derived fuel (RDF) with added Cs-133 (stable nuclide) or Cs-134 (radioactive nuclide) was incinerated in laboratory- and pilot-scale experiments. Next, thermogravimetric (TG) and differential thermal analysis (DTA) of stable Cs compounds, as well as an X-ray absorption fine structure (XAFS) analysis of Cs concentrated in the ashes were performed to validate the behavior and chemical forms of Cs during the combustion.
Our results showed that at higher temperatures and at larger equivalence ratios,Cs-133 was distributed to the bottom ash at lower concentration, and the influence of the equivalence ratio was more significant at lower temperatures. Cs-134 behaved in a similar fashion as Cs-133. We found through TG DTA and XAFS analysis that a portion of Cs in RDF vaporizes and is transferred to fly ash where it exists as CsCl in the MSW incinerator.
We conclude that Cs-contaminated municipal solid wastes could be incinerated at high temperatures resulting in a small amount of fly ash with a high concentration of radioactive Cs, and a bottom ash with low concentrations. (C) 2015 Elsevier Ltd. All rights reserved.