Chemical State Analysis of Heavy Metals and Radioactive Cesium in Municipal Solid Waste Incineration Fly Ash Contaminated with Radioactive Cesium Released by the FDNPP Accident.

The chemical states of heavy metals and radioactive Cs were estimated in fly ash sampled at Fukushima prefecture, Japan. Estimating the speciation of incinerator fly ash is important to ensure an appropriate and efficient management of fly ash generated from disaster-related waste. In this study, fly ash collected at a waste incineration facility in Fukushima prefecture was treated using a sequential extraction test. The test results indicated that the solubility behavior of radioactive Cs was similar to that of NaCl and KCl, and approximately 60% of radioactive Cs was included as water-soluble chloride compounds in the fly ash sample. Most heavy metals eluted in three fractions, in the extraction steps for carbonate-bound, free oxide, and bound to organic matter species. The chemical states of elements in the three non-water-soluble fractions and residue showed minimal elution into the environment. Therefore, most heavy metals in the fly ash exhibited minimal elution into the environment.

Total Quantification of Magnesium Alloys by X-ray Fluorescence Spectrometry Using the "Standardless" Fundamental Parameter Method.

X-ray fluorescence spectrometry using the "standardless" fundamental parameter method has been studied for the whole elemental analysis of magnesium alloys. Twelve major elements were determined: Mg, Al, Si, Ca, Mn, Fe, Ni, Cu, Zn, Ag, Sn and Pb. The specimens used were over 30 mm in diameter and greater than 10 mm thick to determine Sn Kα which has the largest analyzing depth (9 mm) through the alloy samples. The surfaces of the specimens were polished with fine alumina abrasive paper (#240) to remove the oxide layer and to avoid the influence of any surface roughness variation on the intensities of Mg Kα, Al Kα and Si Kα which have smaller analyzing depths. The total quantitative values of the 12 elements, determined by the FP calculation, were normalized to 100 mass%. The analytical values obtained by this method were comparable to those obtained by the conventional calibration curves method. The relative standard deviations were 6.6% for 0.0014 mass% of Ni, and 0.005% for 93.82 mass% of Mg in AZ91 series Mg alloys. The validation results of the proposed method for 12 elements were successful for the five CRMs tested.

Characterization of soluble and insoluble radioactive cesium in municipal solid waste incineration fly ash.

Soluble and insoluble radioactive cesium in municipal solid waste incineration fly ash were analyzed by X-ray diffraction and gamma-ray spectrometry. A total of 60% of soluble radioactive cesium was determined using the Tessier extraction method, and it was almost same extraction rate with Japanese leaching test No.13. In addition, chloride compounds such as halite (NaCl) and sylvite (KCl) showed same behavior with soluble radioactive cesium, therefore, soluble radioactive cesium existed as a chloride (CsCl) with water solubility characteristics. Almost insoluble radioactive cesium trapped into silicate of crystalline phase or amorphous phase was eluted by hydrogen fluoride treatment. Radioactive 137Cs was released in three stages by heating treatment (untreated - 400 °C, 600 °C-800 °C, and 800 °C-1000 °C) according to decreasing amorphous content. The relationship between the concentrations of radioactive 137Cs and amorphous phase exhibited good linearity (R = 0.9278). Insoluble radioactive 137Cs was contained in inner part of the amorphous phase, and free radioactive cesium was determined from the concentration of the amorphous phase.

Crystal Morphology Analysis for Heavy Elements in Municipal Solid Waste Incineration Fly and Bottom Ash by X-ray Characterization Techniques.

The elemental and crystalline phase compositions of fly ash collected before and after spraying of the ash with slaked lime (first and second fly ash) and the bottom ash of municipal solid waste collected at an incineration plant were analyzed using powder briquette by X-ray fluorescence spectrometry and Rietveld refinement by X-ray diffraction. The crystalline and amorphous phase contents were quantified by adding 10% corundum as an internal standard. In the first fly ash, SiO2, Cl, and CaO were the main components, and several thousand ppm (µg/g) of Zn and Pb were detected. Anhydrite, gehlenite, and amorphous phases were the main phases in the first fly ash samples. The components of the first fly ash originated exclusively from the incineration of municipal solid waste in a furnace. The crystal morphologies of the heavy elements in the ash samples were estimated by determining the correlations among the concentrations of all the elements. The heavy elements in the bottom ash showed no strong correlations with other elements; therefore, the heavy elements in the bottom ash were present in an amorphous phase.

Evaluation of physicochemical properties of radioactive cesium in municipal solid waste incineration fly ash by particle size classification and leaching tests.

After the Fukushima Daiichi-Nuclear Power Plant accident, environmental recovery was a major issue because a considerable amount of municipal solid waste incineration (MSWI) fly ash was highly contaminated with radioactive cesium. To the best of our knowledge, only a few studies have evaluated the detailed physicochemical properties of radioactive cesium in MSWI fly ash to propose an effective method for the solidification and reuse of MSWI fly ash. In this study, MSWI fly ash was sampled in Fukushima Prefecture. The physicochemical properties of radioactive cesium in MSWI fly ash were evaluated by particle size classification (less than 25, 25-45, 45-100, 100-300, 300-500, and greater than 500 µm) and the Japanese leaching test No. 13 called "JLT-13". These results obtained from the classification of fly ash indicated that the activity concentration of radioactive cesium and the content of the coexisting matter (i.e., chloride and potassium) temporarily change in response to the particle size of fly ash. X-ray diffraction results indicated that water-soluble radioactive cesium exists as CsCl because of the cooling process and that insoluble cesium is bound to the inner sphere of amorphous matter. These results indicated that the distribution of radioactive cesium depends on the characteristics of MSWI fly ash.

Radioactive nuclides in the incinerator ashes of municipal solid wastes before and after the accident at the Fukushima nuclear power plant.

Radioactive nuclides in the incinerator ashes of municipal solid wastes were determined by γ-ray spectrometry before and after the accident at the Fukushima nuclear power plant (March 11, 2011). Incinerator ash samples were collected in northern Kyushu, Japan, which is located approximately 1200 km west-southwest (WSW) of the Fukushima nuclear power plant, from April 2006 to March 2007 and from March 2011 to October 2011. (40)K, (137)Cs, (208)Tl, (212)Pb, (214)Pb, (212)Bi, (214)Bi, and (228)Ac were identified in the ashes before the accident (~February 2011) and (134)Cs was identified along with these eight nuclides in the ashes after the accident (March 2011~). A sequential extraction procedure based on a modified Tessier method with added water extraction was used for 1st fly ash sampled in August 2011 because the highest activity concentrations of (134)Cs and (137)Cs were observed for this sample. The speciation of radioactive nuclides in the fly ash was achieved by γ-ray spectrometry and powder X-ray diffractometry for the extraction residues. Little variation was observed in the distribution of the chemical forms of (134)Cs and (137)Cs in 1st fly ash of municipal solid waste; one half of (134)Cs existed as water soluble salts and the other half as carbonate compounds, whereas 75% of (137)Cs existed as water soluble salts with the remainder as carbonates(10%) and sulfides (15%). These results show that 88% of the total radioactive Cs existed in water soluble and ion extractive forms and might be at risk for elution and diffusion with rain and wind.