In the evaluation of nuclear equipment, if the elastic analysis cannot meet the corresponding design criteria, the nonlinear analysis should be adopted to assess the safety of equipment. A new nonlinear calculations appendix is supplied in RCC-M 2017 edition annex ZC to secure the nonlinear F.E. calculation performance.
In this paper, the failure modes of nuclear engineering structure are discussed. In order to ensure the safe operation of the structure, the corresponding evaluation criteria formulated by RCC-M code are proposed. Based on the annex ZC of RCC-M 2017 edition, three kinds of nonlinear analysis methods, including limit analysis, plastic analysis and cycle analysis, are studied. The austenitic stainless steel typical nozzle model is used to carry out the finite element calculation. The effect on the limit load is compared between the limit load method of perfect elastoplastic analysis and the secant method of the elastoplastic analysis. The influence of the strain range method and the modified Ke method on the fatigue calculation results is also discussed. The strain range can be determined by monotonic calculation or cyclic calculation. The two kinds of approach are implemented in the elastic plastic fatigue calculation. Compared with the simplified elastic plastic fatigue results, using Ke method to calculate elastic-plastic fatigue can reduce the conservatism of the results.