2 research outputs found
Potential Releases of <sup>129</sup>I, <sup>236</sup>U, and Pu Isotopes from the Fukushima Dai-ichi Nuclear Power Plants to the Ocean from 2013 to 2015
After the Fukushima Dai-ichi nuclear
accident, many efforts were put into the determination of the presence
of <sup>137</sup>Cs, <sup>134</sup>Cs, <sup>131</sup>I, and other
gamma-emitting radionuclides in the ocean, but minor work was done
regarding the monitoring of less volatile radionuclides, pure beta-ray
emitters or simply radionuclides with very long half-lives. In this
study we document the temporal evolution of <sup>129</sup>I, <sup>236</sup>U, and Pu isotopes (<sup>239</sup>Pu and <sup>240</sup>Pu)
in seawater sampled during four different cruises performed 2, 3,
and 4 years after the accident, and we compare the results to <sup>137</sup>Cs collected at the same stations and depths. Our results
show that concentrations of <sup>129</sup>I are systematically above
the nuclear weapon test levels at stations located close to the FDNPP,
with a maximum value of 790 × 10<sup>7</sup> at·kg<sup>–1</sup>, that exceeds all previously reported <sup>129</sup>I concentrations
in the Pacific Ocean. Yet, the total amount of <sup>129</sup>I released
after the accident in the time 2011–2015 was calculated from
the <sup>129</sup>I/<sup>137</sup>Cs ratio of the ongoing <sup>137</sup>Cs releases and estimated to be about 100 g (which adds to the 1
kg released during the accident in 2011). No clear evidence of Fukushima-derived <sup>236</sup>U and Pu isotopes has been found in this study, although
further monitoring is encouraged to elucidate the origin of the highest <sup>240</sup>Pu/<sup>239</sup>Pu atom ratio of 0.293 ± 0.028 we
found close to FDNPP
Radiochemical Determination of Long-Lived Radionuclides in Proton-Irradiated Heavy-Metal Targets: Part ITantalum
In
this study, distillation, precipitation, and ion-exchange methods
were chosen for the separation of the long-lived β-emitters <sup>129</sup>I, <sup>36</sup>Cl and the α-emitters <sup>154</sup>Dy, <sup>148</sup>Gd, <sup>150</sup>Gd, and <sup>146</sup>Sm from
Ta targets irradiated with protons up to 2.6 GeV to determine their
production cross sections. Measurements of <sup>129</sup>I/<sup>127</sup>I and <sup>36</sup>Cl/<sup>35</sup>Cl ratios were performed with
accelerator mass spectrometry. After separation of the lanthanides,
the molecular plating technique was applied to prepare thin samples
to obtain highly resolved α-spectra. Autoradiography and focused
ion beam/scanning electron microscopy techniques were used to characterize
the lanthanide deposited layer. Experimental cross-section data are
compared with theoretical predictions obtained with INCL++ and ABLA07
code, and a satisfactory agreement is observed