Title: HELIOS - The New Design of the Irradiation of U-free Fuels for Americium Transmutation
Citation: Proceedings of Global 2009 p. Paper 9052 (2000-2015)
Publisher: Société Française d'Energie Nucléaire (SFEN)
Publication Year: 2009
JRC N°: JRC49276
URI: https://www.sfen.fr/index.php/plain_site/global_2009
Type: Articles in periodicals and books
Abstract: Americium is one of the radioactive elements that mostly contribute to the radiotoxicity of the nuclear spent fuel. Transmutation of long-lived nuclides like Americium is an option for the reduction of the mass, the radiotoxicity and the decay heat of nuclear waste. The HELIOS irradiation experiment is the last evolution in a series of experiments on americium transmutation. The previous experiments, EFTTRA-T4 and T4bis, have shown that the release or trapping of helium is the key issue for the design of such kind of target. In fact, the production of helium, which is characteristic of 241Am transmutation, is quite significant. The experiment is carried out in the framework of the 4-year project EUROTRANS of the EURATOM 6th Framework Programme (FP6). Therefore, the main objective of the HELIOS experiment is to study the in-pile behaviour of U-free fuels such as CerCer (Pu, Am, Zr)O2 and Am2Zr2O7+MgO or CerMet (Pu, Am)O2+Mo in order to gain knowledge on the role of the fuel microstructure and of the temperature on the gas release and on the fuel swelling. The experiment was planned to be conducted in the HFR (High Flux Reactor) in Petten (The Netherlands) starting the first quarter of 2007. Because of the innovative aspects of the fuel, the fabrication has had some delays as well as the final safety analyses of the original design showed some unexpected deviation. Besides, the HFR reactor has been unavailable since August 2008. Due to the reasons described above, the experiment has been postponed. HELIOS should start in the first quarter of 2009 and will last 300 full power days. The paper will cover the description of the new design of the irradiation experiment HELIOS. The experiment has been split in two parts (HELIOS1 and HELIOS2) which will be irradiated together. Moreover, due to the high temperature achieved in cladding and to the high amount of helium produced during transmutation the experiment previously designed for a high flux position has been moved to a position which has a lower thermal flux of about 0.5*1018 m-2s-1 and a total neutron flux of about 3.3*1018 m-2s-1. The updated nuclear analyses and thermal analyses will be presented in the paper. The paper will also address the detailed thermo-mechanical analyses of the most critical components in term of safety as well as the assembly work performed to prepare the experiment to be safely irradiated in the HFR.
JRC Directorate:Energy, Transport and Climate

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