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Science Festival / Fête de la Science 2021
The 30th edition of the Fête de la Science took place from 8 to 10 October in Hall 6 West in Nantes. It was once again an opportunity to discover the work of researchers, to share knowledge and to explore new knowledge. As every year, thanks to a team of dynamic scientists and technicians, Subatech took part in this important meeting between the general public of all ages and science, by making them (re)discover the fog chamber, the KM3NeT experiment and also the map of nuclei in legos. This edition was a great success with several hundred participants during the weekend.
Nantes research on astatine in the spotlight
Astatine is the rarest chemical element on Earth, and its 211 isotope is very promising for applications in targeted radiotherapy of cancers. Progress in this approach depends on a better understanding of the chemistry of astatine. Researchers from the CRCINA, Subatech and CEISAM laboratories have published a 15-year review of their work in the prestigious Accounts of Chemical Research journal. The most fundamental studies has made it possible to establish the nature of the astatine stable forms in water (Pourbaix diagram) and to reveal astatine ability to form so-called halogen bond interactions, i.e. specific and very directional attractive interactions. Thanks to a collaboration established with the European Organization for Nuclear Research (CERN - Switzerland), the electron affinity of astatine was successfully determined, which is essential to better understand its chemical behavior. The production of astatine-211 by the ARRONAX cyclotron has also enabled the development of new radiochemical synthesis methods and a real leap forward in its use in cancer therapy. The region Pays de la Loire has been supporting this work since 2005; it has also benefited from funding from the Programme d'Investissements d'Avenir (IRON and ArronaxPlus projects) and from the SIRIC ILIAD, and today Nantes is become the main world player in astatine research. This recognition is distinguished at the European level by the creation of an international clinical network (NOAR COST action) which aims to demonstrate that astatine-211 can become the European standard for the treatment of some cancerous pathologies
Guérard, F., Maingueneau, C., Liu, L., Eychenne, R., Gestin, J.-F., Montavon, G. & Galland, N. Advances in the Chemistry of Astatine and Implications for the Development of Radiopharmaceuticals. Acc. Chem. Res. 54, 3264–3275 (2021)
Fukushima, 10 years after
Ten years after the nuclear accident in Fukushima, studies to understand the causes and consequences of the nuclear disaster continue. After the accident, the three reactor cores melted, producing several hundred tonnes of corium and fuel debris, continuously generating heat through the radioactive decay of the fission products present in the corium.
Coordinated by Subatech, a collaboration with JAIEA, Kyshu University and Tokyo University of Technology in Japan and the French Atomic Energy Commission (CEA) has been initiated to summarise the research of the ten years after the accident.
These studies are crucial for any planning of reactor decommissioning.
The temporal evolution of water chemistry and radionuclide inventories leached from the debris by the cooling water was studied. A comparison between the concentration ratios of actinides and fission products measured in water and the results of leaching studies of spent nuclear fuel or debris simulated in the laboratory was carried out.
As with the leaching of spent fuel in the laboratory, the fractions of the 134,137Cs inventories that are analysed in the cooling water are orders of magnitude larger than those of the actinides. After more than 10 years of contact between fuel debris and water, the release rates of 137Cs remain higher than those of actinides even though the release rate of 137Cs from the debris has decreased by a factor of about 100 during this period. Actinide fixation in the debris is strong. The high stability of actinide fixation in debris makes the option of direct disposal of fuel debris as waste in appropriate containers after the decommissioning of reactors in the future viable.
Access to the article "Ten years after the NPP accident at Fukushima : review on fuel debris behavior in contact with water, Journal of Nuclear Science and Technology", https://doi.org/10.1080/00223131.2021.1966347
Authors : Bernd Grambow, Ayako Nitta, Atsuhiro Shibata, Yoshikazu Koma, Satoshi Utsunomiya, Ryu Takami, Kazuki Fueda, Toshihiko Ohnuki, Christophe Jegou, Hugo Laffolley& Christophe Journeau (2021)
Status of reactor corres, Fukushima at 2018: a) unit 1; b) unit 2, c) unit 3. In blue: as the cooling water flowed, the cores largely melted and much of it fell onto the concrete at the bottom, references: Mizokami S, Rempe JL. The Events at Fukushima Daiichi. Reference Module in Earth Systems and Environmental Sciences . Elsevier; 2020.