Integrity of low-pressure steam turbine rotors in stress corrosion environments

For a number of years, stress corrosion cracking of turbine rotors has caused serious problems for power station operators. Steam turbine rotors of the shrunk-on disc type have been particularly susceptible, to the extent that about 75% of all nuclear power stations in the United States equipped with such rotors have experienced disc cracking due to stress corrosion. Operating experience shows that the welded rotor design provides the only proven solution to the problem of stress corrosion cracking. This is demonstrated convincingly by 33 nuclear power stations with 79 low-pressure rotors which have accumulated some 5 million operating hours. This contribution summarizes the reasons for the excellent operating behaviour of the welded rotor and compares it with other rotor designs. (Auth.)