What is the primary means of preventing a rod ejection accident?

• A. Redundancy in the reactor trip system
• B. Thorough vessel head inspections
• C. Regular boron concentration checks
• D. Enhanced coolant flow

Answer: (B)

Preventing a rod ejection accident mainly comes from keeping the boundary that contains the control rod drive intact. The rods enter and exit the core through the reactor vessel head and its penetrations, so any cracks, corrosion, or bolt failures in the vessel head could create a path for a rod to be forcibly ejected under pressure. Regular, thorough inspections of the vessel head are the best way to catch such flaws early and schedule repairs or replacements before an ejection scenario can develop.

Other measures address different aspects of safety but don’t prevent the mechanical ejection path itself: having a redundant reactor trip system helps ensure a rapid shutdown if something goes wrong, but it doesn’t stop the physical ejection mechanism from failing; monitoring boron concentration keeps reactivity in check, which is about shutdown margins rather than preventing a mechanical ejection; and boosting coolant flow improves heat removal, not the integrity of the rod drive boundary.