Grid supports design for dual-cooled fuel rods

摘要

To enhance fuel safety and to achieve a power uprating, a new concept PWR (Pressurized Water Reactor) fuel, which is called a dual cooled fuel rod, has been studied since 2007. Although there are some challenging problems about each mechanical component, fuel rod supporting structures are especially dealt within this paper. In the dual-cooled annular fuel rod, an inner flow passage as well as an outer one is used not only to enhance the fuel safety but to achieve a power uprating through the decreasing fuel center temperature and increasing the heat transfer area between fuel and coolant. As a result, the diameter of dual-cooled fuel rods becomes 1.6 times bigger than a conventional solid fuel rod and the gap between the annular fuel and the spacer grid s straps is narrowed. This is a current key issue of fuel rod supports [1]. To accommodate the narrowed gap, spacer grids, such as the cantilever type, hemi-sphere type [2], circular insertion type [3], etc., were suggested. For some of these configurations, patents have been applied.