A method to design a nuclear fuel assembly having the following steps
including establishing the falling speed of the control rod upon entry
into the lower damping portion when the control cluster falls in the
event of a shutdown of the nuclear reactor, establishing, based on the
falling speed established in step a), the progression of the falling
speed of the control rod in the lower damping portion, establishing,
based on the progression of the speed established in step b), a maximum
elevated pressure produced in the liquid contained in the lower damping
portion, and establishing, based on the maximum elevated pressure
established in step c), a maximum circumferential stress produced in the
lower damping portion.