Numerical Analysis Of Post Weld Heat Treatment Of CAP1400 Nuclear Power Containment Vessel

The steel containment vessel is a special equipment of the third generation advanced PWR AP/CAP reactor nuclear power plant.It is a cylindrical vertical steel pressure vessel containing the upper and lower elliptical heads,and the shell material is SA-738 Gr.B plate.And it is designed,manufactured and installed according to ASME(American Society of Mechanical Engineers)boiler and pressure vessel subsection NE.The AP1000 steel containment vessel has been completed in Zhejiang Sanmen and the Shandong Haiyang nuclear power plant.According to the specification,the post weld heat treatment is required only between the first circle of the cylinder and the insert plate which is thicker,and the other welds do not need to be heat treated after welding.The diameter and the thickness of CAP1400 steel containment vessel,which is designed by our country,is larger than that of AP1000,so that the post weld heat treatment is required for the whole cylinder.Due to the construction characteristics,CAP1400 steel containment vessel can not be whole post weld treated,also local post weld treated for full circle weld required by ASME code can not be performed within the capacity limitation of electricity at the site.In this paper,the suggestted local post weld treatment plan is put forward through the finite element numerical analysis according to the characteristics of post weld treatment,principle of not producing harmful stress distribution to the product quality,to ensure the stability and security of the structure while in the process of the post weld treatment,and to improve the quality of construction.Through the tensile test,the mechanical properties of SA-738 Gr.B steel plate produced by different steel mills in China are determined and the actual performance data of the materials used in the numerical analysis are obtained.The heat conduction coefficient of the asbestos insulation board is determined by the temperature gradient distribution test of different structural types.The simplified finite element model is established by taking the steel safety shell type structure type.The thermal elastoplastic finite element method is used to simulate the local whole heat treatment of the welded joint of the steel safety shell,the local section heat treatment,the sectional local heat treatment of the circumferential welds in the dense zone,the heat treatment of the equipment gate,the heat treatment of the personnel gate and the heat treatment of the inserting plate.At the same time,the deformation value is too large for the equipment gate to heat treatment along the weld seam,which has exceeded the requirement of the design side of the tube deformation not more than one wall thickness.The heat treatment after welding is converted into sectional heat treatment.The numerical analysis is carried out for the H01 and H02 of the equipment gate in different structural positions,and the segmentation is analyzed.The later deformation value and stress value.The segmented condition,heating requirement and temperature gradient distribution of the heat treatment for the girth weld of the cylinder were analyzed,and a recommended scheme for partial gate heat treatment of the equipment gate was put forward.Deformation monitoring was carried out in post weld heat treatment of CAP1400 containment construction site,and the results were basically consistent with the data analyzed in this paper.