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Design principles: Currently, all container specifications for low-temperature pressure vessels are based on allowable stresses determined by the tensile strength or yield strength at room temperature. This method can effectively prevent failure due to large plastic deformation. How to determine the required level of resilience should be decided based on the principles adopted. The first principle allows for certain defects, but cracking should be prevented. Welded areas generally have more defects and lower toughness. And fractures always start at defects and areas with poor toughness. Therefore, when applying this principle, it is necessary to determine the properties of the heat-affected zone and the weld seam. It requires the areas with the lowest toughness to be able to withstand the strain generated by external loads. The second principle allows for the presence of defects and the possibility of cracking in the weld areas with poor resilience; it relies primarily on the base material to prevent crack propagation and thus avoid failure accidents. Since the toughness of the weld metal, fusion zone, and heat-affected zone is lower than that of the base material, cracks tend to propagate along the weld area; therefore, this method is not reliable for preventing brittle fracture. The third principle allows cracking to occur at defects, while all parts of the container can prevent the crack from spreading. It has two disadvantages. ①When using this method to prevent brittle fracture, materials with very high toughness must be selected, which means the material costs are extremely high ； ②The effectiveness of it as an absolute safety criterion is related to the type of structure. The results of blast testing on containers with defects show that crack stopping is easier under fully hydraulic conditions; whereas under pneumatic conditions or those with partial gas presence, crack stopping is more difficult due to the larger amount of energy stored in the system, or specialized crack-stopping structures must be designed. For low-temperature pressure vessels in the petrochemical, refrigeration, and air separation industries, the medium inside them is often in a gaseous state or a gas-liquid two-phase state; therefore, the crack prevention principle cannot be used to avoid low-temperature brittle fracture.