Voids in the coolant primarily concern which reactor type?

• A. PWR
• B. BWR
• C. Both PWR and BWR equally
• D. Neither

Answer: (B)

The main idea here is how steam voids in the coolant affect the neutron economy and reactor reactivity. In a Boiling Water Reactor, the core actually operates with boiling coolant, so steam voids are a regular and influential part of the reactor environment. When voids form, they change how neutrons are moderated and how effectively they cause fission, altering reactivity in a way that must be actively managed. That makes void behavior in the coolant a central factor in both design and safety for BWRs.

In a PWR, the core is kept under high pressure so the coolant stays liquid, and voids are not a normal condition. Any void formation tends to reduce moderation and is typically associated with a negative reactivity effect, so voids are not the primary design or operational concern there. This contrast is why voids in the coolant are most closely tied to Boiling Water Reactors.