Abstract: An austenitic stainless steel includes a mixed grain structure composed of a columnar crystal having an average crystal grain size of 20 ?m or less and an equiaxed crystal having an average crystal grain size of 5.0 ?m or less, in which an area proportion of the columnar crystal in the mixed grain structure is 20% or more, and an average crystal grain size of the whole mixed grain structure is 5.0 ?m or less. Accordingly, it is possible to provide a material having excellent irradiation resistance and mechanical properties.

Abstract: An austenitic stainless steel includes a mixed grain structure composed of a columnar crystal having an average crystal grain size of 20 ?m or less and an equiaxed crystal having an average crystal grain size of 5.0 ?m or less, in which an area proportion of the columnar crystal in the mixed grain structure is 20% or more, and an average crystal grain size of the whole mixed grain structure is 5.0 ?m or less. Accordingly, it is possible to provide a material having excellent irradiation resistance and mechanical properties.

Abstract: A manufacturing system of an additive manufacturing body is provided, by which the accuracy of evaluating a defect during additive manufacturing and the quality of the body can be improved. A manufacturing system of an additive manufacturing body of the present invention includes: an additive manufacturing device; an inspection device having a camera for photographing the powder layer or the solidified layer; and a control device that controls the additive manufacturing device and the inspection device, in which: the camera can photograph the powder layer for each powder layer forming step that is performed repeatedly, or can photograph the solidified layer for each solidified layer forming step that is performed repeatedly; and the control device selects a photographing condition of the camera according to the conditions of the additive manufacturing process.