['It', 'can', 'be', 'observed', 'that', 'the', 'sequential', 'increase', 'of', 'the', 'layer', "'s", 'thickness', 'converge', 'to', 'an', 'asymptotic', 'value', 'of', 'reactivity', 'reduction', 'slightly', 'over', '800pcm', '.']