The rod cluster control assembly (RCCA) is designed with appropriate limits on the maximum worth so that the core internal structures can provide core cooling without damage to the integrity of the coolant pressure boundary at an ejection of a RCCA. Secondly, it is designed with appro­priate limits on the maximum reactivity insertion rate so that the fuel integrity is secured at a simultaneous withdrawal of two banks of RCCAs at the maximum speed. Thirdly, it is also designed with appropriate limits on the maximum worth so that the fuel integrity is secured at a drop of a fully-withdrawn RCCA at the hot full power condition.