Caratterizzazione sperimentale termofisica alle alte temperature di nitruri per applicazioni in reattori nucleari di nuova generazione - JRC-ITU-TN-2008/50

In this Ph.D. thesis an extensive experimental measurements and data analysis campaign has been carried out on nitride compounds considered as possible fuel for new generations of nuclear reactors. Thermophysical and thermochemical data and related analysis, obtained from measurements on ZrN, UN, (Zr, Pu) N and (U, Pu) N, are presented and discussed, comparing them, when applicable, with reference data available in literature. These compounds are of interest, beyond their large applications in the electronic and solar energy devices, also as fuels (e.g. UN) or inert matrices (e.g. ZrN) for the nuclear industry. This is due mainly to their excellent thermophysical properties, such as thermal conductivity and heat capacity, in comparison with the standard oxide fuels of today¿s Light Water Reactors (i.e. UO2 and, to a lesser extent (U, Pu)O2). The possible future use of the nitrides is foreseen in the context of the Generation IV reactors, which are designed to be more efficient, safer, more economic and more sustainable than today¿s reactors. The advanced fuels will work at higher temperatures, in order to reach higher temperatures of the coolant (490 ¿ 850 °C instead of ~320 °C for the LWR) and of the turbine steam or gas (hence more efficient thermodynamic cycle and higher thermal and electrical output). Moreover, they will fulfill the minor actinides burning function to minimize long term radiotoxicity of the nuclear waste and allow using recycled fissile material recuperated from fuel previously irradiated, to ensure better economy and sustainability of the whole fuel cycle. The present Thesis is written and submitted in order to fulfill the requirements to obtain the title of Ph.D. 4JRC.E.3-Materials researc