If the void coefficient is negative, what does it indicate about the reactor core?

If the void coefficient is negative, what does it indicate about the reactor core?

• A. Negative feedback loop
• B. Positive feedback loop
• C. No feedback
• D. Instability

Answer: (A)

The idea being tested is how reactivity responds to changes in voids (steam bubbles) inside the reactor. A negative void coefficient means that as voids increase, reactivity decreases. In practice, if power tends to rise and causes more boiling, the additional voids reduce reactivity and push the power back down. If power falls and boiling drops, voids decrease and reactivity rises, nudging power back up. This opposing action forms a negative feedback loop, which stabilizes the reactor rather than amplifying changes. It’s not a lack of feedback, and it’s not instability—the negative sign shows a self-correcting tendency that helps keep the reactor steady.

The idea being tested is how reactivity responds to changes in voids (steam bubbles) inside the reactor. A negative void coefficient means that as voids increase, reactivity decreases. In practice, if power tends to rise and causes more boiling, the additional voids reduce reactivity and push the power back down. If power falls and boiling drops, voids decrease and reactivity rises, nudging power back up. This opposing action forms a negative feedback loop, which stabilizes the reactor rather than amplifying changes. It’s not a lack of feedback, and it’s not instability—the negative sign shows a self-correcting tendency that helps keep the reactor steady.