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Performance determination and mechanical calculation of nuclear safety valve

Release Date: December 23, 2017

1. Determination of mechanical properties of materials:

The main parts of the valve are A182 or F316L stainless steel. According to ASME-Ⅲ-1, when the working temperature is 200 ℃, the allowable stress of the material can be checked [1] S 1 = 107MPa. Take the stainless steel elastic modulus E = 1.9 × 1011Pa, Poisson's ratio μ = 0.3, density ρ = 7 900kg / m3. The material of the bolt connector is 0Cr17Ni4Cu4Nb. According to GB 1220-92, the yield strength of the material Sy = 725 MPa, and the tensile strength [2] Su = 930 MPa.

The tensile strength of the material changes less with temperature.According to ZⅢ320 in RCC-M Volume I, the allowable application of bolts should be

Force [3] S 2 = min (0.25 Sy, 0.2 Su) = 181MPa.

2. Mechanical calculation of the valve under normal operating conditions:

Under normal operating conditions, the main loads on the valve include working pressure, bolt preload and self-weight. Because the working temperature of the valve is uniformly distributed, the thermal stress of the system is very small. No analysis is performed here. The working temperature only affects the allowable stress value of the structural material. In the process of establishing the finite element model, only the mass and stiffness distribution of the main components of the valve are considered, and the emphasis is on the simulation of the pressure boundary.

Due to the complicated shape of the main parts of the valve, the valve is divided into three parts for mechanical calculation. The first part is to calculate the valve body to obtain the valve body stress distribution; the second part is to calculate the valve cover to obtain the valve body stress distribution; the third part is to calculate the main connecting bolts of the valve to Bolts are evaluated for safety.