Complex sentence: Each fuel element was in diameter and housed 164 uranium oxide pellets enriched to 4.4% U- 235, except for the 16 center elements which were enriched to 4.2% and the outer 16 elements at 4.6%.
Split into simpler sentences: Each fuel element was in diameter and housed 164 uranium oxide pellets enriched to an average of 4.4% U- 235. The 16 center elements were enriched to 4.2%, and the outer 16 elements to 4.6%.