Lesson 3 ◆ 3.2 Fuel Assemblies
  • An 1100 MWe PWR core may contain 193 fuel assemblies
  • These are composed of over 50,000 fuel rods and approximately 18 million fuel pellets
  • Rods are held in a square lattice by spacer grids (which also serve as coolant mixers)
  • Typical rod array: 17 x 17 or 14 x 14 (including control rod guide tubes)
  • Top and bottom nozzles support the overall skeletal structure
  • Fuel stays in the core for several years
  • During refuelling (every 12 to 18 months), typically one-third or one-quarter of the core is removed to storage, while the remainder is rearranged to a location better suited to its remaining enrichment level
  • Cladding is Zircaloy