TOP NOZZLE ASSEMBLY HAVING IMPROVED HOLD DOWN PERFORMANCE IN A FUEL ASSEMBLY OF A NUCLEAR REACTOR

摘要

PURPOSE: A pushing spring unit for a top fixing body and the top fixing body for a nuclear fuel assembly are provided to improve stability against the mechanical and structural deformation of a nuclear fuel assembly by decreasing the hold-down margin in a startup condition and a hot full power condition of a nuclear reactor. CONSTITUTION: A pushing spring unit is combined with the upper side of a top fixing body which fixes a nuclear fuel assembly. A pushing spring unit includes a first cervical spring(110) and a second cervical spring(130). The first cervical spring acts against the pushing force applied to the nuclear fuel assembly in a startup condition or hot full power condition. A second cervical spring acts against the pushing force applied to the nuclear fuel assembly in only the startup condition.