The aim of the project is to experimentally and computationally evaluate advanced fuel assemblies with enhanced accident tolerance that are at an early stage of technological readiness but represent a significant technological advance. These are materials such as SiC/SiC, FeCrAl alloys, ODS or Cr-Ni alloys. The project will obtain and characterise samples of advanced claddings in their original state. These will then be tested according to the developed methodologies, which will be continuously adapted to the specificities of the materials and using existing knowledge of nuclear fuel. The objective of the experimental evaluation is to describe the degradation mechanisms of the concepts tested and their limiting parameters with respect to operational and accident conditions. The project will furthermore focus on detailed microstructure characterisation by light microscopy, advanced electron microscopy techniques (FIB-SEM using EDS-WDS-EBSD techniques and TEM) and micro/nanoindentation method to complement the microstructure analyses with changes in local mechanical properties. Similarly, the microstructure will be monitored at the sites where the mechanical abrasion resistance test was performed. Further activity will focus in the first phase on the production of fuel rod segments with high density uranium fuel and zirconium matrix. The produced segments will be characterised in their original state (uranium quantity and homogeneity, steam corrosion rate, image analysis and chemical/crystallographic analysis to show the distribution of the different phases) and after conditions corresponding to a LOCA. Light Optical microscopy (LOM) and advanced scanning electron microscopy (SEM using EDS-WDS-EBSD techniques) and gamma scanning in HC will be used to characterize the initial state and microstructure condition after LOCA experiments. Nanoindentation methods will also be used to analyse the changes in local mechanical properties of individual phases after LOCA. The experimental work will be complemented by neutron-physics calculations to estimate the influence of nuclear data libraries, which is non-negligible in the field of alternative materials. Integral to the extension of the competencies in the study of ATF claddings and fuels will be the conceptual design and work on irradiation rig/capsules for use on the LVR-15 reactor with consideration of heat removal (it is envisaged to use samples in the geometry of current UO2 fuel pellets or pellets of Burnable Absorbers), including performing activation analyses to determine the activities of irradiated samples and developing a strategy for transport and handling in hot cells.

Klíčová slova
Innovative nuclear fuel; ATF; Accident tolerant fuel; Advanced nuclear fuel; nuclear fuel matrix; nuclear fuel cladding