Boiling water reactor fuel rod bundle with variable fuel rod spacing

摘要

A fuel assembly (10) for a BWR comprises an array of fuel pins (12) extending between upper (16) and lower (14) tie plates and surrounded by an outer fuel channel (11). The fuel pins (12) are held in place by a spacer grid (18) located between the upper (16) and lower (14) tie plates. The fuel assembly (10) is also provided with an inner water rod (44) which conducts coolant from the base of the assembly to the top. The lower tie plate (14) positions the base of the array at one pitch and the spacer grid (18) positions the array at a different pitch.