STEAM TURBINE DEVELOPMENT FOR SMALL MODULAR REACTORS

Introduction of Small Modular Reactor (SMR) technology is likely to play a significant role in energy transition over the next decades by delivering safe, reliable, and sustainable power when required. There are currently more than ninety different types of SMRs in development employing various fuel and cooling solutions. The nearest to market SMR designs are based on state-of-the-art boiling water reactor (BWR) or pressurized water reactor (PWR) technologies and will generate electrical power using steam turbine generator sets operated using an optimized Rankine cycle. This paper will provide an insight on developments of new steam turbine modules for various inlet volumetric sizes suitable for the 50 MW to 500 MW power range focused on the major design considerations. Even though the steam expansions for the near to market SMRs vary significantly they all have wet steam expansions. The wetness significantly influences the performance and swallowing capacity of the modules. Like industrial or utility power plant of these sizes, steam turbines for SMRs will operate at full speed i.e., 3000 rpm for 50 Hz grids or 3600 rpm for 60 Hz grids although the smallest SMR may have high speed turbines. While the geometric features could be scaled from large nuclear machines with proven operating experience, nucleation effect and water droplet sizes does not scale in the same proportion and hence the impact of wetness needs special consideration. The design features need to reduce water erosion to the largest extent possible by suitably extracting water and hence improving performance and reliability. All SMR plants are expected to have significantly shorter lead times to commercial operation than today's large nuclear plant. This being achieved by modularizing the design, constructing in a factory environment, and consequently reducing the erection time and project cost. To achieve a high degree of construction schedule certainty, standardization of plant design across the different site locations is a strong consideration. Selection of a common steam turbine footprint without compromising performance at different cold end conditions is an important contributing factor.