In general, digital twin refers to a digital replica of physical process or systems. We have proposed the digital twin concept of a mother design for twin children (experiment and simulation) with a help of the additive manufacturing technology. Moreover, the digital triplet concept to derive the regressive and well-correlated design on the basis of knowledge and experiences with a help of machine learning and statistics. The paper addresses our developed technologies of powder production, powder metallurgy, three-dimensional modelling, additive manufacturing to expand material variations for broadening the application of additive manufacturing. Devised additive-manufacturing method is devoted for complex structures with scalable measurement and control systems, including wide variety of thermal-hydraulic applications together with computational multi-fluid dynamic simulations in terms of the nuclear safety.