However, recent studies have shown that the Cs concentrations are associated with discrete Zn–Fe-oxide nanoparticles embedded in a pure SiO 2 glass matrix, as well as numerous nano-scale inclusions with a variety of fission products 15, 16. CsMPs were initially considered as amorphous glass particles containing various elements derived from the reactors that were melted into the glass matrix 12, 13, 14. The 134Cs/ 137Cs radioactivity ratio of ~1 indicates that they originated from the FDNPP. Different from the soluble Cs, the CsMPs are sparingly soluble in water. This is another important route of Cs migration in the environments. A possible cause of the heterogeneity is the formation of Cs-rich microparticles (CsMPs), with a high Cs radioactivity per unit mass, found at a range of distances from the FDNPP 12. However, Cs in the contaminated soils is heterogeneous and concentrated locally at the micron scale as hot spots, as revealed through autoradiography 9, 10, 11, and this heterogeneity has not been fully described. Subsequently, a soluble form of Cs was tightly bound to the interlayers of clays, such as vermiculite, and remained within the top ~5 cm of the soil 3, 9, 10.
Previous studies of the distribution and migration of radioactive Cs in the surface environment around Fukushima 4, 5, 6, 8, 9, 10, 11, 12 indicated that an initially soluble form of radioactive Cs was released from the damaged reactors and spread over the Fukushima Prefecture and the surrounding area through dry and wet deposition 3, 4, 5, 8. About 1–7% of the Cs inventory of three reactor cores was released 3, 7. Radioactive Cs, 134Cs and 137Cs, are the most important radionuclides contributing to the high radiation in the environment near the FDNPP at present because of their relatively short half-lives, 2.06 and 30.07 years, respectively 6. The released radionuclides, including noble gases (Xe and Kr) and volatile fission products (I, Cs, Te, Sb, and Ag), contaminated the surface over ~14,000 km 2 surrounding the FDNPP 1, 2, 3, 4, 5, requiring the evacuation of some 100,000 residents. Radionuclides with ~520 PBq initial total activity were released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) as a result of the nuclear disaster that occurred after the Tohoku earthquake on Ma1. Also, the CsMPs were an important medium of transport for the released radionuclides in a respirable form. The nano-scale texture and isotopic analyses provide a partial record of the chemical reactions that occurred in the fuel during meltdown.
Analogue reactor meltdown walkthrough code#
The values are higher than the average burnup estimated by the ORIGEN code and lower than non-irradiated fuel, suggesting non-uniform volatilization of U from melted fuels with different levels of burnup, followed by sorption onto Zn–Fe-oxides. The 235U/ 238U values in two CsMPs: 0.030 (☐.005) and 0.029 (☐.003), are consistent with that of enriched nuclear fuel. nH 2O, CsMPs are comprised mainly of Zn–Fe-oxide nanoparticles in a SiO 2 glass matrix (up to ~30 wt% of Cs and ~1 wt% of U mainly associated with Zn–Fe-oxide).Apart from crystalline Fe-pollucite, CsFeSi 2O 6 U, Cs, Ba, Rb, K, and Ca isotopic ratios were determined on three CsMPs (3.79–780 Bq) collected within ~10 km from the FDNPP to determine the CsMPs’ origin and mechanism of formation. Highly radioactive cesium-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) provide nano-scale chemical fingerprints of the 2011 tragedy.
0 kommentar(er)
