Elastic-Plastic Analysis and Evaluation Method for the Research Reactor Irradiation Device

Mechanical calculation and evaluation of the loop irradiation device are prerequisites for ensuring structural integrity and conducting irradiation tests. The design of the HFETR (High Flux Engineering Test Reactor) irradiation device adopted a double layer pipe, which included the pressure pipe and the insulation pipe. Early HFETR irradiation devices did not consider a fracture accident of the pressure pipe. This paper proposed for the first time a stress analysis and evaluation method for the insulation pipe under the hypothetical fracture of the pressure pipe. This paper uses the elastic-plastic analysis method to analyze the stress and strain of the insulation pipe, and evaluates it using the non-elastic evaluation criteria of the ASME code. The results showed that the stress of the insulation pipe exceeded the material yield strength at this operating temperature, resulting in permanent deformation. However, its plastic deformation was relatively small, with a maximum plastic principal strain of 0.507%, which was far less than the limit of 2.5% in the ASME code. The method proposed provides a reference for the design and evaluation of irradiation devices in other research reactors.