Patent ID: 7509242

Claim:
A system for designing a nuclear fuel assembly which is intended to be positioned in a nuclear reactor, the assembly comprising a plurality of guide tubes and a control cluster which itself comprises a plurality of control rods which are received in the guide tubes and a support for the control rods, the assembly comprising a helical spring for damping an impact of the support against an upper end piece of the assembly in an event of the control cluster falling during a shutdown of the nuclear reactor, the system comprising a computer and a storage arrangement configured to store at least a program comprising instructions for performing the following steps of designing a nuclear fuel assembly: establishing a progression of speed of the control cluster after the impact of the support against the upper end piece; establishing, based on the speed of the control cluster after the impact of the support against the upper end piece, a maximum longitudinal load for compression of the spring; and establishing, based on the maximum longitudinal load for compression of the spring, at least a maximum shearing stress in the spring.