Which scenario constitutes a core reload error during refueling?

• A. Placing partially burnt and new fuel assemblies exactly according to core design
• B. Placing partially burnt and new fuel assemblies in a way not following core design
• C. Replacing cladding with incorrect material
• D. Using only new fuel assemblies

Answer: (B)

The main idea is that fuel management during refueling must follow a predefined pattern that balances reactivity and power distribution. Partially burnt fuel and fresh fuel behave differently in neutronics, so their placement is not arbitrary. If you insert them in a way that does not align with the approved reload design, you upset the neutron flux balance, creating localized power peaking, uneven burnup, and tighter safety margins. This is a reload error because it violates the planned arrangement that keeps the reactor operating safely and efficiently.

When the partially burnt and new fuel are placed exactly as the design specifies, that’s how the core is intended to be loaded. Replacing cladding with an incorrect material is a separate fabrication/handling mistake, not the reload-pattern error described here. Using only new fuel would also deviate from the planned pattern, but the scenario in question highlights the mismatch with the established design as the error.