Structure Design And Stress Analysis Of CAP1400 Spring-loaded Main Steam Safety Valves

The CAP 1400 spring-loaded main steam safety valves are widely used to main steam pipelines in advanced nuclear power plants, which will been designed, manufactured and operated in China. This article mainly investigates the structure design and stress analysis, including seismic design, flexible disc design, primary stress and secondary stress analysis. For experiments, we use the Lms Testlab Signature Acquisition and transfer function method to measure first nature frequency, and the Alicona IFM G4 to obtain sealing surface profile. For simulations, commercial software Abaqus has been widely used to structure design and stress analysis.At the same time, the simulated results and the experimental results are been compared, so that we can verify the exactness of simulation. The main conclusions are shown as follows:(1) In seismic design, body thickness, stem stiffness, reinforcing rib has a little effect on first nature frequency, but the height and weight of spring is crucial to it. After structure optimization, the first nature frequency improved from 23.55 Hz to 37.11 Hz, and the simulated result 23.55 Hz has been validated by experiments. Static analysis was used to verify stress in seismic condition, and it meets the seismic design requirements.(2) During the inner pressure increasing from 0 MPa up to 8.56 MPa (setting pressure), the maximum contact pressure of flexible disc transfers from outer surface to inner surface. To the sealing surface of flexible disc, the plastic deformation located in the outer surface, which has a significant effect to repeatability; the maximum contact pressure located in inner surface when inner pressure close to setting pressure, which is crucial to sealing performance;(3) After overall and local structure design, stress analysis is been carried out. According to the standard of ASME BPVC III NC, the primary stress and primary stress plus secondary stress is been checked.