Preliminary thermal and mechanical analysis on the reactor core of a new heat pipe cooled reactor applied in the underwater environment

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The heat pipe cooled nuclear reactor (HPR) has great potential in the underwater applications, as a reliable energy system provider, due to its advantages in the passive heat removal capability and avoidance of single point failure. For the newly proposed HPR concept design, NUclear Silence ThermoElectric Reactor (NUSTER), the thermal and mechanical analysis is performed, on the three-dimensional detailed solid core model, through the coupling of ANSYS Fluent and Mechanical. The safety limits are preliminarily proposed for the NUSTER, based on which the paper analyzes the reactor thermal and mechanical characteristics under the normal and heat pipe failure accidents. It is found that the core components, including the fuel rods, matrix and heat pipe can operate with large thermal margin in the normal condition. The heat pipe failure accidents will cause the large temperature increase of the fuel rods, matrix and heat pipes and significantly change the thermal stress distribution in the fuel Molybdenum (Mo) cladding and matrix. The Mo matrix temperature exceeds its temperature limit and the average thermal stress increases significantly in the two adjacent heat pipes failure accident of the 1/8 reactor core, indicating the further optimization of the matrix material in the future design.