![iaea-tecdoc-1188 iaea-tecdoc-1188](https://img.yumpu.com/19535566/1/500x640/cilt-volume-17-say-number-1-2-2006-111496-kb-veteriner-.jpg)
14 on sub-regions of Unit 1 particulates indicated a high degree of compositional heterogeneity, with all of the elements encountered within these samples attributable to either reactor fuel/components, or fission products. Its 134Cs/ 137Cs activity ratio (<1.0) invokes a source attributable to reactor Unit 1 and a release on the 12th March 2011 (Unit 3 is excluded because of the prevailing wind conditions at the time 15). Termed “Type B” by Satou (2016) 13, this similarly amorphous material is composed predominantly of Si glass and is sub-millimeter in maximum dimension. In contrast, material derived from closer to the plant, located more northerly than the main plume produced by Unit 2, has received scant scientific attention.
![iaea-tecdoc-1188 iaea-tecdoc-1188](https://s3.manualzz.com/store/data/021384155_1-d08c09b06cd1e91e8a66597ae3f49a25-360x466.png)
By comparing the measured radiocesium activity ratios ( 134Cs/ 137Cs) of this material with reactor-core inventory modelling 12, these micron-scale “Cs-balls” were attributed to the emission from reactor Unit 2 13, 14. The subsequent discovery of the more wide-spread dispersion of such micron-scale fallout material prompted further investigations on the structure and composition of such spherical material using an expanding suite of advanced analytical techniques 8, 9, 10, 11, the most common being transmission electron microscopy (TEM). examined the internal structure of some of these micron-scale particles using synchrotron-radiation (SR) x-ray fluorescence (XRF) 7. Progressing the analysis of Adachi et al., who employed scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS), work by Abe et al. 6 first reported the isolation and analysis of infrequent, but considerably more active, particles (averaging 2 μm in diameter) from material obtained 170 km southwest of the FDNPP, attention was diverted to alternative forms of Fukushima-derived contamination. Immediately after the accident, considerable research effort was invested into studying the radiocesium strongly adsorbed to phyllosilicate minerals in sediments 5.
![iaea-tecdoc-1188 iaea-tecdoc-1188](https://i1.rgstatic.net/publication/344999658_Dielectric_loss_and_extended_voltage_response_measurements_for_low-voltage_power_cables_used_in_nuclear_power_plant_potential_methods_for_aging_detection_due_to_thermal_stress/links/5f9bdbb292851c14bcf2e8b9/largepreview.png)
Estimates place the total release from this International Nuclear Event Scale (INES) Level 7 event at between 340 PBq and 800 PBq 3 – one tenth of that resulting from the Chernobyl accident 25 years earlier 4. Loss of coolant incidents (LOCI) associated with three of the sites nuclear reactors 2 were responsible for the radioactive releases. Such a high void ratio, comparable to geological pumice, suggests such material formed during a rapid depressurisation and is potentially susceptible to fragmentation through attrition.įollowing the 2011 magnitude 9.0 Great Tōhoku earthquake and subsequent tsunami off the eastern coast of Japan 1, a considerable amount of radioactivity was released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) into the global environment. We consider the structure and composition of the particle to suggest it formed from materials associated with the reactor Unit 1 building explosion, with debris fragments embedded into the particles surface. A heterogeneous distribution of the various elemental constituents is observed inside a representative particle, which also exhibited a Fukushima-derived radiocesium (134Cs, 135Cs and 137Cs) signature with negligible natural Cs. The particles are shown to exhibit significant structural similarities being amorphous with a textured exterior, and containing inclusions of contrasting compositions, as well as an extensive internal void volume – bimodal in its size distribution. A suite of particles is analyzed from a locality 2 km from the north-western perimeter of the site – north of the primary contaminant plume in an area formerly attributed to being contaminated by fallout from reactor Unit 1. Results from this study allow for the proposition of the likely formation mechanism of the particles, as well as the potential risks associated with their existence in the environment, and the likely implications for future planned reactor decommissioning. Both the three-dimensional internal structure and elemental distribution of near-field radioactive fallout particulate material released during the March 2011 accident at the Fukushima Daiichi Nuclear Power Plant is analysed using combined high-resolution laboratory and synchrotron radiation x-ray techniques.