sionalism and hard work during the experiments, I would like to highlight their kindness in making us having a agreeable stay at Belarus. I wish to acknowledge as well the institutions that have provided nancial support for the work carried out during this PhD thesis: the EU 6th Framework program through IP-EUROTRANS Contract No. FI6W-CT2005-516520 and the ENRESA-CIEMAT agreement for the Transmutation Applied to High Level Radioactive Waste.Third, I want to thank as well all the colleagues from the Nuclear Innovation Unit and Nuclear Fission Division at CIEMAT during all these years, for all that I have learned with them and all the help they have provided at many instances, which would be endless to detail. In particular, special thanks to those that have revised the manuscript: Manuel Fernández-Ordóñez, Francisco Álvarez-Velarde and Juan Blázquez. I am also indebted to the administrative and services sta at CIEMAT for their usually invisible, albeit indispensable, assistance in many daily tasks. In particular, I would like to mention the Documentation Service for their help in nding many of the bibliographic references of this thesis.And nally, last but not least, I would like to acknowledge my family for all their support during all these years.