Fuel assembly

Purpose: To obtain an adequate excess reactivity or an allowance for reactor shutdown with ease by controlling the loading amount of fissile material or burnable poison while leaving fuel assemblies arranged in the reactor core. Constitution: A tie plate has a large aperture allowing a fuel rod to pass therethrough, along the inner surface of which a pair of first grooves pass vertically corresponding to each other and a pair of second grooves are formed with an adequate length from the bottom displaced circumferentially by 900 from the first grooves respectively. A replacing fuel rod is inserted so that the tab fits the first and second grooves. Upon replacing the fuel rod, the fuel rod to be replaced can easily be removed by depressing the upper end plug from above to detach the tab from the lower face of the upper tie plate and rotating it by 900 to align with the first groove. (Horiuchi, T.)