Fuel Cycle Performance of Thermal and Fast Spectrum Small Modular Reactors
Open Access
- Author:
- Hernandez, Richard
- Graduate Program:
- Nuclear Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 20, 2019
- Committee Members:
- Nicholas R. Brown, Thesis Advisor/Co-Advisor
William J Walters, Committee Member
Arthur Thompson Motta, Committee Member - Keywords:
- SMR- Small Modular Reactor
Fuel Cycle Analysis
Impacts of Neutron Leakage
Natural resource utilization
Spent Fuel Activity
Fuel Cycle Evaluation and Screening Study - Abstract:
- The work found in this thesis, consisted of the fuel cycle performance analysis of several thermal and fast spectrum small modular reactor (SMR) designs and concepts. This analysis was conducted following the guidelines found in the U.S. Department of Energy Office of Nuclear Energy (DOE-NE) Evaluation and Screening (E&S) study chartered in 2011. The impacts of core neutron leakage on the fuel cycle performance of these modular reactors, was investigated using several of the specific performance criteria identified in the E&S study. This work was accomplished by creating computer models from which neutronics investigations could be performed. The first study consisted of the construction of a VVER-1000 fuel assembly neutronics model. The specifications were taken from an international computational benchmark paper. This assembly model was used to conduct a fuel cycle investigation of the thermal spectrum VVER-like SMR designs described in this thesis. The impacts of different neutron leakage rates, fuel enrichments, and core power densities on the natural resource utilization and the highly radioactive waste outputs at 100 and 100,000 years after fuel discharged were analyzed. The study showed that core neutron leakage was the most impacting parameter to the fuel cycle performance of these thermal SMRs, and that changes in fuel enrichment and core power density had minimal impacts on both of these criteria studied. The 10% U-235 fuel enrichment case with 0% leakage, had a natural resource utilization of 314.5 t/GWe-yr. As leakage was increased to 3% and 7%, the resource utilization dropped to 344.1 and 394.7 t/GWe-yr respectively. Whereas, as fuel enrichment was increased to 15% and 19.7%, using the 0% leakage case, resource utilization dropped to 329 and 341 t/GWe-yr respectively. A 50% lower power density resulted in a slight increase of about 2 t/GWe-yr, when compared to the full power cases. The activity levels of the SNF+HLW for all of the cases studied were between 1.2E+06 and 1.4E+06 Ci/GWe-yr at 100 years, and between 1.6E+03 and 1.8E+03 Ci/GWe-yr at 100,000 years. The second study, involved the fuel cycle analysis of a neutronics computer model based on the component specifications of the fast spectrum special purpose heat pipe reactor. This concept was first proposed at Los Alamos National Laboratory (LANL). The LANL concept, was chosen to represent the Westinghouse 〖"eVinci" 〗^"TM" micro heat pipe reactor concept currently under development. This was due to their fundamental similarities, as well as the ambiguity surrounding the specific component details of the 〖"eVinci" 〗^"TM" concept found in open source papers. The initial investigation, consisted of analyzing the fuel cycle performance of a 10-year fuel cycle option simulated using the built neutronics computer model. This fuel cycle length was chosen, because Westinghouse indicated that the 〖"eVinci" 〗^"TM" concept is intended to operate for ten years without refueling. A 5MW and 25 MW rated core thermal output was used in this initial fuel cycle investigation. The natural resource utilization of the 5MW and 25MW were 9612 and 1933 t/GWe-yr respectively for the most efficient thermal cycle available for this concept. The waste metrics analyzed following criteria guidelines found in the E&S study, were around 1.00E+06 Ci/GWe-yr for both rated power cases at 100 years after fuel discharged. At 100,000 years after fuel discharge, the SNF+HLW activity in the 5MW and 25MW power cases were determined to be 3.37E+03 and 2.37E+03 Ci/GWe-yr respectively. Following, an investigation into the most optimal fuel cycle length of the special purpose reactor, with a rated thermal output of 25 MW, was conducted using a subset of the nine high level criteria found in the E&S study. The environmental impacts, natural resource utilization, waste management metrics and proliferation risk, as a result of this fuel cycle option, were all analyzed in this optimization study. The natural resource utilization of the most effective thermal cycle was determined to be 1704 t/GWe-yr. The land and water use were calculated to be about 0.784 square km and 25320 ML per GWe year respectively. Carbon emissions were 247 kilotons of CO2 per GWe year. Lastly, the impacts of core neutron leakage and parasitic absorption were quantified in a third fuel cycle investigation, utilizing the 25 MWth model used in the optimization study. The study concluded that the core neutron leakage was the most limiting factor to the fuel cycle performance of these fast spectrum SMR concepts. A reduction in core leakage from the reference model 18% rate to 9.7, resulted in an increase in natural resource utilization from 1704 to 350 t/GWe respectively.