Impact of Core Power Density on Economics of a Small Integral PWR

Increasing the core power density of nuclear reactors allows higher power generation from the same volume, reducing the cost of the plant. The lower power rating and higher degree of inherent safety for small modular reactors motivate exploring the highest achievable power density to improve their economics and overcome lack of economy of scale. Given the urgency to deploy carbon free energy sources in the near term, the current nuclear fuel supply must be adopted. Assuming standard 17x17 pressurized water reactor (PWR) fuel assemblies with enrichment below 5%, a parametric study on core power density of an integral PWR (iPWR) is performed. The reference core design is rated at 60 kW/L and composed of 77 reduced-height fuel assemblies. The reactivity control during normal operation is assumed to utilize soluble boron and fuel burnable poisons. The commercial STUDSVIK code package is used to design cores ranging from 20 kW/L to 170 kW/L. This range results in respective output powers between 50 to 420 MWe for an assumed 32% plant thermal efficiency. Core safety parameters, such as peaking factors, Minimum Departure from Nucleate Boiling Ratio and maximum fuel temperatures are evaluated for all designs. Simplified economic evaluation of lifetime-levelized unit costs for the fuel cycle, operation and maintenance and capital expenditures was performed as a function of power density. The relatively low core discharge burnup (32 MWD/kgU) leads to high lifetime-levelized fuel cycle unit cost for the reference core. However, increase in power density allows significant reduction in operation, maintenance and capital unit costs. Doubling power density resulted in 80% reduction in total levelized cost of electricity. The unique features of a forced circulation iPWR technology combined with compact steam generator technology could allow achieving high power densities (>125 kW/L). Specific examples on relationship of cost and safety margins are also discussed.