Producing intense radioactive beams, in particular those consisting of short-lived isotopes requires the control of the release efficiency. The released fractions of 11 elements were measured on 14 samples that were characterized by various physicochemical analyses in a correlated paper (Part 1). A multivariate statistical approach, using the principal component analysis, was performed to highlight the impact of the microstructure on the release properties. Samples that best release fission products consist of grains and aggregates with small size and display a high porosity distributed on small diameter pores. They were obtained applying a mixing of gro und uranium dioxide and carbon nanotubes powders leading to homogeneous uranium carbide samples with a porous nanostructure. A modelling under on-line ALTO conditions was carried out using the FLUKA code to compare the yields released by an optimized and a conventional target.
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Introduction:The research and development program at the ALTO facility (Accélérateur Linéaire et Tandem d'Orsay) of the Institut de Physique Nucléaire d'Orsay (IPNO) aims to provide new beams of exotic and neuton-rich nuclei, as intense as possible. At ALTO, neutron-rich nuclei are produced by photofission in thick uranium carbide targets. An efficient way to improve the intensities of the radioactive beams, in particular those consisting of short-lived isotopes, would be to develop dense and porous targets. These two properties are antagonistic but essential to increase the fission fragment quantity produced and diffuse them out of the target respectively.