• Minor Actinides
• MOX fuel
• nuclear fuel cycle GHGs emissions
• TRANSURANUS code
• TUBRNP
• weapon-grade Plutonium

The present work concerns the study of Plutonium and some Minor Actinides (MAs) radial distribution in PWRs MOX fuel pellets by means of TRANSURANUS code. The distribution models are obtained by improving the TRANSURANUS burnup model TUBRNP (TRANSURANUS burnup equations), by means of new equations integrated in the program structure. The input files taken as a reference are obtained from the literature analysis carried out in the first step of the work.
The first part of the thesis is dedicated to a brief state of the art revision focused on the plutonium issue, the MOX fuel question, and gives also a panoramic EPR-UK and Westinghouse PDR reactors, in order to obtain a framework of the worldwide situation and to gather data for the computational phase.
In the second step, the computational one, are described the procedures used to improve the TUBRNP and the results obtained by its application to 6 cases, namely a high burnup fuel, the EPR-UK reference MOX fuel, two weapons-grade MOX fuels and a MOX-EU fuel. Particularly, the analyses have provided the radial distribution of plutonium and MAs in the 6 fuel types. These distributions are analysed in detail and compared with the previous results arising from the old version of TUBRNP, already validated from ITU, in order to find out the principal equations terms that can affect the forecasting and that can be further improved to better describe the phenomenology.
Finally, in the third phase, is conducted a brief analysis of the question regarding the radiotoxicity reduction of spent nuclear fuel, quoting the recycling option, and a study of the GHGs emission related to the nuclear fuel cycle, delineating a forecast of future energy scenarios.