Seawater leakage of a condenser caused by titanium tubes fracture occurred frequently during the nuclear power units operation

which seriously affects safe and stable operation of the unit. Through statistical analysis of the previous events and metallology analysis of the titanium tube

it is confirmed that the all the cracking of titanium tube occurred under half-side operation of the condenser or the load shedding operating mode of the nuclear power units. Fatigue fracture was found through the micro-images analysis of the cracked titanium tubes. By studying the design criterion of the condenser and comparing with the industry design criterion

the unreasonable calculation of critical and maximum actual velocity was found to be the main root cause. Moreover

the high operating power of the unit under the half-side condenser operation further caused the fluid elastic vibration of the titanium tube. Finally

through the preventive measures such as tubes plugging

adding anti-abrasive strips and unit power control during half-side condenser operation

the seawater leakage risk was reduced effectively. In new design of this kind condenser

the span of titanium tubes was reduced

to improve the safety margin of fluid elastic vibration of the titanium tube fundamentally.