Biggest Nuclear Steam Turbin

GE Arabelle 1700 : 1.900 MW

https://www.ge.com/steam-power/products/steam-turbines/nuclear-arabelle

Mitsubishi Power Steam Turbine with 1880™ LSB : 2.000 MWe

https://power.mhi.com/catalogue/pdf/nuclear_turbine.pdf

Siemens SST-9000 : 1.900 MW

https://www.siemens-energy.com/global/en/offerings/power-generation/steam-turbines/utility-steam-turbines.html

The present day manufacturing industry for steam turbines are made by manufacturers include

• Siemens
• Mitsubishi KwHI 
• Toshiba IHI
• General Electric
• Turboatom
• Silmash and Ural TW
• BHEL
• Alstom, Doosan Škoda Power, Ansaldo, Nevsky Turbine Plant (Nevsky NTW), KTZ, Energomash-Atomenergo, MAPNA, and Toshiba.
• Chinese manufacturers like Harbin Electric, Shanghai Electric, and Dongfang Electric

Sumber :

https://en.wikipedia.org/wiki/Steam_turbine#Manufacturing