Structure Simulation And Optimization Research Of Helium Vessel In China Spallation Neutron Source Target Station

China Spallation Neutron Source (CSNS) is the first spallation neutron source designed and constructed by China independently. The Helium vessel, in which target, slowing down devices, reflectors and shield components are installed, is the main mechanical support structure in CSNS target station. Severe requirements are made for the stress and deformation of Helium vessel to ensure the accuracy of the neutron scattering measurements. And special considerations are also required under the lifting and transport cases for the special structure of Helium vessel.(1) Structure analysis of overall model and fore local models of Helium vessel were carried out by using ANSYS and Workbench. According to the relevant standards and technical requirements, the stress and displacement of Helium vessel under different cases were evaluated and the results of evaluation can meet the requirements, and the reliability of the mechanical structure of Helium vessel was proofed.(2)The static analysis and thermal-structural coupling analysis of Lower Outer Reflector Plug, which is the key component of the core vessel in the China Spallation Neutron Source target station, were conducted using the commercial numerical software ANSYS and CFX. The fields of stress and displacement in different working conditions were achieved. The results indicate that the thermal load affect the stress intensity too much and should be considered in the process of strength evaluation. Although the mechanical strength of Lower Outer Reflector Plug can satisfy the criterion, the risk of strength failure of Lower Outer Reflector Plug under the situation of long time cooling failure was also predicted.(3) Suitable connection between Helium vessel and skirt was selected through comparative analysis among three connection schemes. The local model of dovetail-type pin, which is the most dangerous structure, was established and optimization analysis was carried out. The results show that the maximum stress is decreased by19.7%and the connection is more safe.(4) According to the relevant design manuals, locations of lifting lugs and transport saddles were determined. Flange lug, tail lug and tension bands on saddles were designed and checked. And security of Helium vessel under the cases of the lifting and transport is also ensured.Outcomes of the thesis offered an important basis to the mechanical structural design of Helium vessel.