Nuclear Power Plant Component Materials Fatigue Damage Under Random Loading, Rain Flow Method

Now, the lifetime of the overseas first generation commercial nuclear powers plants is going to be end. In the developed countries in nuclear power, such as American Japan > Germeny, the second goal of nuclear power research is to operate plants for their optimum lifetime and ensure the operating safety beyond the original design life.In China, though the nuclear power industry started very laterly, there are multi-type reactors, it is very difficult to operate them, the management level of lifetime is lower than that in overseas. To evaluate plants accident and provid the basis beyond the original design life, the transient monitoring of the key components should be built up.The 300 series austenitic stainless steel, which is the main material of the containment buildings pressure boundary and the control rod drive mechanisms(CRDMs), will be damaged for the fatigue. Since the fatigue is the damage cumulative process, it is necessary to study 300 series austenitic stainless steel fatigue behavior with the plants transient changing.In this text, the 321 SS is selected to study fatigue behaviorThree load spectrum (max-damage, mid-damage, min-damage) are designed and separated with the rainflow method, the fatigue cumulative usage factors(CUF) are calculated according the ASME.The experimentation indicate that it is viable to calculate the CUF of the plants key components, such as containment buildings pressureboundary and CRDMs, with the rainflow method and ASME. The retardation of tensile overload will reduce the 321SS crack growth speed for the furcation on the fracture section. But the sequence effect of load is not obvious, this phenomenon is related with that the tensile overload is overlarge and the compress load is too small, or with the very narrow crack growth section which will let the statistics of fatigue cover up the sequence effect of load.