ABSTRACT

The potential development of nuclear energy increases considerably with the increase of global energy demand. However, the management of the waste from spent nuclear fuel from conventional nuclear plants is one of the main problems that the use of this energy source faces nowadays. The aim of the present work is to make a conceptual design of the TADSEA (Transmutation Advanced Device for Sustainable Energy Applications): A pebble-bed accelerator driven system (ADS), cooled by Helium, that uses as fuel transuranic elements that are part of spent nuclear fuel from conventional light water reactors, encapsulated in the form of TRISO particles (TRIstructural-ISOtropic), to transmute these long lived radioactive elements into stable or short-lived elements, decreasing the mass and radiotoxicity of the waste, and also use the high temperatures that the coolant can reach at the core’s outlet in such systems, to produce Hydrogen from water, either by the Iodine-Sulfur (I-S) thermo-chemical cycle or by high temperature electrolysis. An analytic method was developed for the considered design in order to calculate the real porosity of the pebble bed, which is a very important parameter for neutronic and thermal-hydraulic calculations. Considering the real porosity, the neutronic design of the TADSEA was done, and taking into account different positions of the neutron source, the most uniform power density profiles were obtained inside the core for the different working states of the system using MCNPX software. The general scheme of the Hydrogen production plant was designed to assure a coolant outlet temperature high enough for Hydrogen production by the processes mentioned above, and coolant temperature profiles were obtained using ANSYS CFX software from the power density distributions obtained with MCNPX. Two models were designed for the study of the temperature distribution inside the fuel elements in order to prove that the limited temperature established for the type of fuel considered is not exceeded. Also, the calculation of the coolant pressure drop through the core was performed. This preliminary study lays the groundwork for future more detailed studies related to this topic.