Küçük Modüler Nükleer Reaktörün 3-Boyutlu Tasarımı ve Toryum Kullanımı ile Analizi

Abstract

The aim of this study is to investigate the thorium utilization for a novel Small Modular Nuclear Reactor designed with this study by generating the 3-dimensional (3D) model of the reactor. For this, MCNP6.1.1b code is used for neutronic and burnup analysis and COBRA-TF code is used for thermal-hydraulics analysis of the hottest channel of the designed reactor core. To perform neutronic and burnup analyses, full core model has been developed in MCNP6.1.1b. Energy generation data obtained from the developed reactor model is used to prepare an input for COBRA-TF code for performing the hottest channel analysis. Complete and accurate use of full and 1/6 core model is important in terms of analyzes performed. To easily model core loading pattern changes in the reactor core, a code system was developed in Python3 programming language which is rapidly create full and 1/6 reactor model, so platform independent core generation structure has been created. For the code system development, Cube coordinate system used in pixel calculation and computer games is adapted for hexagonal nuclear reactor core geometry. Since hexagonal geometry approach analysis is performed easily in Cube coordinate system, full and 1/6 reactor core models have been created rapidly. Since the geometric design values are constituted in parametric structure for nuclear reactor model, not only small nuclear reactor but also many nuclear reactors which have hexagonal unit cell structure can be easily created by the developed code system. In addition, a novel Python3 script which has ability to use NJOY nuclear data processing program is developed to create new ACE data libraries of whole elements to be used in MCNP6.1.1b code. The most update raw neutron data libraries which contain whole interaction and some bound scattering data are obtained from databases and they are produced at temperatures of reactor structures. Produced neutron data libraries are benchmarked with NEA International Criticality Safety Benchmark Evaluation Project (ICSBEP) test problems. Afterwards, temperature dependent neutron data libraries are prepared to contain temperatures of the materials used in nuclear reactor model, to be used by MCNP6.1.1b code. Formed modeling structure, obtained 3D model and prepared neutron data libraries are used to determine the suitability of using thorium in 3D core model. In the lights of obtained analysis preformed for the designed nuclear reactor core, estimated burnup values have been evaluated during the nuclear reactor design procedures. However, estimated fertile to fissile conversion has not been met. Besides, isotopic changes as a result of the nuclear reactions are investigated in the nuclear reactor core. By using the design and operational values of the modeled core, hottest channel of the reactor is simulated to calculate critical heat flux ratio to observe whether reactor will be safe for normal operation and anticipated operational transients or not.