[en] As discussing the relation between power flow difference and vibration level difference, the simplification of power flow difference expression of vibration isolation devices leads to an expression which shares the same characteristics with power flow difference by using only vibration response, for example, vibration displacement, and by the comparison of the new expression and the one of vibration level difference, the article puts forward a new calculating method of vibration level difference with the consideration of weight factor. The FEM results show that in the not very high frequency region, both the simplification and approximation of power flow difference expression are reasonable and the vibration difference curve is more similar to the curve of power flow difference when mixed with a coefficient on behalf of force factor. (authors)

[en] Air valves are common devices in nuclear power plants to control air flux and pressure. To ensure the structural safety, the air valve of the emergency negative pressure system of the nuclear power plant is analyzed by finite element method (FEM). Based on the calculation of the inherent frequency of the air valve structure, the stress and the deformation of the air valve structure under earthquake are obtained. The analysis results show that the stress and the deformation satisfy the requirements of relative seismic codes, indicating that the air valve structure is safe and reliable under earthquake. (authors)