COVER STORY | STEAM TURBINE DEVELOPMENT
Arabelle goes to new lengths
The two Arabelle steam turbine trains at Hinkley Point C in the UK, currently under construction, will each be capable of producing an astonishing 1770 MW (gross). A
key contributor to this unprecedented power output is the deployment of 75in last stage blades in the Low Pressure (LP) modules, the longest such blades ever made. The size, coupled with strict limits on their weight, posed significant challenges for the development team, requiring new design tools and manufacturing processes. The result: a high performance last stage, manufacturable at moderate cost
By: Ivan McBean Principal Engineer, Aerodynamics, Arabelle Solutions, Baden, Switzerland
THE ARABELLE TURBINE PLATFORM HAS been developed for nuclear half speed applications and can be deployed with different reactor types and for different cooling water temperatures. Some typical PWR applications include Akkuyu in Turkiye, Flamanville in France, and Taishan in China. The Arabelle turbine trains for these power plants have a high-pressure (HP) and intermediate-pressure (IP) module as well as multiple low-pressure (LP) turbine modules. In the LP turbines, the last stage blades have a length of 69in (1.7526m). More recent applications have been identified that involve even lower cooling water temperatures and higher steam volume flows at the LP turbine exhaust. This has led to the development of a 75in (1.905m) last stage blade to accommodate the required increase in LP exhaust area. This increase in last stage blade length posed a significant challenge to the design team in the development process due to the strict limits on last stage blade weight.
Turbine configurations for nuclear plants The main two categories of turbine configuration for nuclear power plants are referred to as half-speed (rotating at half of the grid frequency, 1500 RPM for a 50 Hz grid and 1800 RPM for a 60 Hz grid) and full speed (rotating at the grid frequency, 3000 RPM or 3600 RPM). Although there is a current trend to develop smaller reactors and full speed turbine designs, the economics of nuclear power plant design still require a high steam volume. A comparison of half-speed versus full-speed configurations for a given power plant output shows that the half speed layout involves a reduced number of LP turbine modules and a requirement for only one train, whereas at large power outputs the full-speed layout requires two trains. Clearly these are not the only considerations when designing the plant, and the plant economics vary over time and depend on the geographic location and power market. Nonetheless, the half speed train configuration remains the most
Above: Rendering of Arabelle LP module Source: Arabelle Solutions 26 | October 2024 |
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