High-Fidelity Nuclear Energy System Optimization towards an Environmentally Benign, Sustainable, and Secure Energy Source

A new high-fidelity integrated system method and analysis approach was developed and implemented for consistent and comprehensive evaluations of advanced fuel cycles leading to minimized Transuranic (TRU) inventories. The method has been implemented in a developed code system integrating capabilities of MCNPX for highfidelity fuel cycle component simulations. The impact associated with energy generation and utilization is immeasurable due to the immense, widespread, and myriad effects it has on the world and its inhabitants. The polar extremes are demonstrated on the one hand, by the high quality of life enjoyed by individuals with access to abundant reliable energy sources, and on the other hand by the global-scale environmental degradation attributed to the affects of energy production and use. Thus, nations strive to increase their energy generation, but are faced with the challenge of doing so with a minimal impact on the environment and in a manner that is self-reliant. Consequently, a revival of interest in nuclear energy has followed with much focus placed on technologies for transmuting nuclear spent fuel. In this dissertation, a Nuclear Energy System (NES) configuration was developed to take advantage of used fuel recycling and transmutation capabilities in waste management scenarios leading to minimized TRU waste inventories, long-term activities, and radiotoxicities. The reactor systems and fuel cycle components that make up the NES were selected for their ability to perform in tandem to produce clean, safe, and dependable energy in an environmentally conscious manner. The reactor systems include the AP1000, VHTR, and HEST. The diversity in performance and spectral characteristics for each was used to enhance TRU waste elimination while efficiently utilizing uranium resources and providing an abundant energy source. The High Level Waste (HLW) stream produced by typical nuclear systems was characterized according to the radionuclides that are key contributors to long-term waste management issues. The TRU component of the waste stream becomes the main radiological concern for time periods greater than 300 years. A TRU isotopic assessment was developed and implemented to produce a priority ranking system for the TRU nuclides as related to long-term waste management and their expected characteristics under irradiation in the different reactor systems of the NES. Detailed 3D whole-core models were developed for analysis of the individual reactor systems of the NES. As an inherent part of the process, the models were validated and verified by performing experiment-to-code and/or code-to-code benchmarking procedures, which provided substantiation for obtained data and results. Reactor core physics and material depletion calculations were performed and analyzed. A computational modeling approach was developed for integrating the individual models of the NES. A general approach was utilized allowing for the Integrated System Model (ISM) to be modified in order to provide simulation for other systems with similar attributes. By utilizing this approach, the ISM is capable of performing system evaluations under many different design parameter options. Additionally, the predictive capabilities of the ISM and its computational time efficiency allow for system sensitivity/uncertainty analysis and the implementation of optimization techniques. The NES has demonstrated great potential for providing safe, clean, and secure energy and doing so with foreseen advantages over the LEU once-through fuel cycle option. The main advantages exist due to better utilization of natural resources by recycling the used nuclear fuel, and by reducing the final amount and time span for which the resulting HLW must be isolated from the public and the environment due to radiological hazard. If deployed, the NES can substantially reduce the long-term radiological hazard posed by current HLW, extend uranium resources, and approach the characteristics of an environmentally benign energy system.