Research on manufacture technology of spherical fuel elements by dry-bag isostatic pressing

Abstract

The steady development of high-temperature gas-cooled reactors (HTRs) has increased the requirements for the production cost and quality of fuel elements. Green fuel element pressing is one of the key steps to increase the production capacity. This paper proposes a proprietary vacuum dry-bag isostatic pressing (DIP) apparatus. The structural change of the matrix graphite powder during the DIP process was examined by analyzing the density change of the matrix graphite spheres with pressure. The soft molding process was simulated using the finite element method. The dimensional changes in the spheres during the pressing, carbonization, and purification stages were explored. The performance of the fuel matrix produced by the DIP method was comprehensively examined. The fuel matrix met the technical requirements and its anisotropy was significantly reduced. The DIP method can significantly improve both the production efficiency and quality of fuel elements. This will play a key role in meeting the huge demand for fuel elements of HTRs and molten salt reactors.