ELSY core design static, dynamic and safety parameters with the open square FA

This work has been carried out within the framework of the STREP ELSY (European Lead-cooled SYstem, 6th EU FP) that investigates the technical and economical feasibility of a 600 MWe power nuclear reactor. Even if the project foresees the utilisation of ELSY for waste transmutation, this report (Deliverable D8, WP 2, Task 2.2) deals with a typical pure MOX loading configuration without 'waste', i.e MAs, to be transmuted. One of the main challenge points in the core design, made up of wrapper-less square Fuel Assemblies, is the small difference between the coolant average outlet temperature and the max allowable cladding one, that requires a rather flat radial power distribution, goal achieved by three enrichment radial zones. Three different independent control sets of absorbers have been introduced to achieve the required reliability for reactor shutdown and safety: eight traditional concept Control Rod assemblies, and two innovative systems of sparse control 'Finger Absorber' Rods. A subset of these finger rods is devoted to both compensate and control the reactivity during the fuel cycle; their positioning could be used to further improve the power flattening.