Déchet radioactif

Résumé

Un déchet radioactif est un déchet qui, du fait du niveau de sa radioactivité, nécessite des mesures de radioprotection particulières. Ces déchets doivent réglementairement faire l'objet d'une caractérisation radiologique (par le producteur de déchets) et d'un contrôle (par le centre de stockage), afin d'assurer que leur stockage est adapté à leur radioactivité éventuelle, et ne crée pas de risque radiologique. Le cas échéant, dans de nombreux pays, des « déchets nucléaires » sans radioactivité significative peuvent être « libérés » après contrôle, pour être traités comme des déchets d'activités économiques de même type. La plus grande partie des déchets radioactifs provient de l'industrie nucléaire qui utilise et génère des matières radioactives dans les différentes étapes du cycle du combustible nucléaire. Les déchets radioactifs proviennent également de la médecine nucléaire, d'industries non nucléaires (extraction des terres rares par exemple), de l'utilisation passée d'éléments r

Source officielle

https://fr.wikipedia.org/wiki/D%C3%A9chet_radioactif

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Standardisation des outils de calcul pour les ADS et leur application à différents scénarios de transmutation des déchets

Marco Cometto

The management of radioactive wastes from the nuclear fuel cycle has become an important issue in the development of future, more sustainable nuclear energy systems. Partitioning and transmutation (P&T) of actinides and some long-lived fission products could reduce the mass and radiotoxicity of highlevel wastes and possibly ease repository licensing requirements. Influenced by political and technological developments, an increasing number of countries employing nuclear power have become interested in P&T technology which involves the development of new types of critical and/or sub-critical reactors and very efficient fuel cycle strategies. The present thesis is closely connected to two P&T related projects of the OECD Nuclear Energy Agency in Paris, a numerical benchmark exercise for an accelerator-driven minor actinides burner and a calculational system study on the role of accelerator-driven systems (ADS) and advanced fast reactors (FR) in advanced nuclear fuel cycles. The author co-coordinated the benchmark exercise and performed the comparative analysis of the different "fuel cycle schemes" investigated in the system study. The benchmark exercise contributed to a greater understanding of the physical phenomena characteristic of the transmutation of actinides in a closed fuel cycle, and allowed to test and improve the tools used for modeling ADSs and corresponding advanced fuel cycles. This work thus effectively led to the development of an efficient and more complete calculational scheme, which has permitted an in-depth and reliable analysis of different transmutation scenarios to be carried out. To quantitatively assess the advantages and drawbacks of transmutation, we considered a limited number of "base" transmutation scenarios which constitute an envelope for various possible transmutation strategies employing fast spectrum systems. We then evaluated, for an equilibrium situation, the main aspects which characterise the different transmutation strategies, such as the nuclear park composition, the mass and toxicity of the waste, the need for natural uranium, the in-pile and out-pile mass inventories and, finally, the fuel cycle requirements. Thus, this study has allowed for the reliable comparison of performances of the three main options in the nuclear waste management, viz. open cycle, recycling of plutonium alone and recycling of all the actinides, as well as an evaluation of the advantages and disadvantages of ADSs in comparison to advanced critical reactors in the management of minor actinides or transuranics. The last part of the dissertation is dedicated to a phase-out study for two schemes employing either ADSs or critical reactors. It has been shown thereby that advanced systems, optimised for an equilibrium fuel composition, can indeed be used to reduce the inventory of transuranics. A comparison of ADS and FR performances has been made in this context, and the relative benefits of transmutation have been quantified in each case taking into consideration, more realistically, the residual mass inventory after the shutdown of all nuclear installations.

EPFL2003

Chargement

Professor Laloui gave an interview to Migros Magazine. The talk was about nuclear waste storage. As we know, disposal of nuclear waste abroad is forbidden since 2006 and therefore new solutions are being considered. The solution discussed is underground waste storage that could hold up to 100 000 square meters of radioactive waste.

2018

Chargement

The semester project was under the course Physics lab IVb at EPFL. At EPFL site, the experimental fission reactor CROCUS is shielded by concrete which becomes radioactive as a result of neutron interaction. The activation is of interest to study for validation of models and cal- culations, and to quantify the amount of radioactive waste when the reactor will be recycled. In this project, measurements on concrete ac- tivation by NaI- and HPGe-detectors were performed on an in-cavity concrete block, together with TLD measurements on neutron flux in- side the core of CROCUS and in the cavity. The concrete activation and neutron flux allows for comparison and validation of models. The in-cavity concrete block had a low activation, trace elements of 60Co and 65Zn seem to be existing. The relative flux was the highest for structures close to the core and at the ceiling. In future projects, more experimental data on both concrete activation and neutron flux would be performed to acquire uncertainty estimations and correction factors.

2017

Chargement

Standardisation des outils de calcul pour les ADS et leur application à différents scénarios de transmutation des déchets

Marco Cometto

EPFL2003