PELGRIMM

"PELlets versus GRanulates: Irradiation, Manufacturing & Modelling"

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 Obiettivo del progetto (Objective)

'PELGRIMM is a 4 year project, addressing Minor-Actinide (MA) bearing fuel developments for Generation IV Fast Reactor Systems to support the Strategic Research Agenda (SRA) of the European Sustainable Nuclear Energy –Technology Platform (SNE-TP). Both options, MA homogeneous recycle in driver fuels with MA content at a few percent, and heterogeneous recycle on UO2 fuels bearing high MA contents, located in the radial core blanket, are considered. Two fuel forms (pellet and spherepac) will be investigated. Indeed, spherepac technology (that leads to production of beads that can be directly loaded in pins) is attractive regarding MA-bearing fuels as it would lead to a significant simplification of the fabrication process and to a better accommodation of solid swelling (compared to pellets) under irradiation. These developments extend Europe's leading role in this area. A total of 12 partners from research institutions, education establishments and industries will collaborate to share and leverage their skills, progress and achievements, covering a comprehensive set of investigations: fuel fabrication, fuel behaviour under irradiation through an irradiation test and the execution of Post Irradiation Examinations, modelling and simulation of fuel behaviour and performance under irradiation, from normal operating conditions to severe accidents, and finally by providing unique education and training possibilities. Finally, synergies will be sought with other ongoing European projects. Furthermore, the PELGRIMM project will contribute actively to the EURATOM’s contribution to Generation IV International Forum (especially SFR).'

Introduzione (Teaser)

After plutonium, MAs are the main contributors to the long-term radiotoxicity of spent nuclear fuels. To reduce the amount of MAs from spent fuel and therefore its radiotoxicity, new nuclear fuel concepts are being developed.

Descrizione progetto (Article)

The focus of the 'Pellets versus granulates: Irradiation, manufacturing & modelling' (http://www.pelgrimm.eu/ (PELGRIMM)) project is the transmutation of MAs, the fundamental step in closing the nuclear fuel cycle. Within the PELGRIMM project, irradiated samples of sphere-pac fuel, prepared by the EU-funded 'Fabrication, irradiation and reprocessing of fuels and target for transmutation' (FAIRFUELS) project are being examined.

Fuel in the form of small spheres is produced by internal gelation, which guarantees homogeneity as compared to standards pellets. Internal gelation is a chemical reaction occurring when the base solution is heating up to 80? C. The sphere-pac fuel allows the introduction of MAs into the fuel matrix and transmutates them in a fast reactor.

A different option involved diluting MA in uranium dioxide (UO2) matrices of varying porosity and also irradiating in the same sodium-cooled fast reactor in Petten. These so-called MA-bearing blankets along with sphere-pac fuels and conventional pellets were irradiated for approximately 304 days.

The PELGRIMM scientists have prepared the samples for their transfer to the Laboratoire d'examen des combustibles actifs (LECA) facility in Cadarache for testing. In addition, a series of models describing the fuel behaviour under fast neutron irradiation have been developed. A significant volume increase observed during the Marios and Sphere experiment was attributed to the production of helium.

Helium production is linked to the transmutation of americium, one of the radioactive elements that contributes largely to the long-term radioactivity of spent nuclear fuels. Investigations on recycling MA-bearing fuels has started recently but many aspects remained unknown. For example, knowledge remains limited in terms of the role that microstructure or temperature play in the behaviour of nuclear wastes when irradiated.

The PELGRIMM project is expected to capitalise on the efforts of the FAIRFUELS project as well as other EU-funded projects to efficiently close the nuclear fuel cycle. Closed nuclear fuel cycles will ultimately reduce the volume and radioactive content of long-lived nuclear wastes which require disposal in geological repositories.