Which action is not part of boron dilution mitigation?

Which action is not part of boron dilution mitigation?

• A. Rapid insertion of soluble boron
• B. Adjusting control rods to reduce reactivity
• C. Reducing reactor power with existing safety systems
• D. Do nothing and wait for natural stabilization

Answer: (D)

In a boron dilution event, the reactor loses some of its boron concentration, which raises reactivity. The goal of mitigation is to counter that reactivity increase quickly with active steps that restore negative reactivity or reduce the driving force for neutrons. Adding soluble boron rapidly reintroduces absorbing material, lowering reactivity fast. Adjusting the control rods to absorb more neutrons directly reduces reactivity as a countermeasure. Reducing reactor power with existing safety systems lowers the neutron production and gives more time to manage the boron concentration and reactivity safely. Doing nothing and waiting for natural stabilization is not a mitigation action because it does not actively counter the reactivity increase and could allow the reactor to approach unsafe conditions.

In a boron dilution event, the reactor loses some of its boron concentration, which raises reactivity. The goal of mitigation is to counter that reactivity increase quickly with active steps that restore negative reactivity or reduce the driving force for neutrons. Adding soluble boron rapidly reintroduces absorbing material, lowering reactivity fast. Adjusting the control rods to absorb more neutrons directly reduces reactivity as a countermeasure. Reducing reactor power with existing safety systems lowers the neutron production and gives more time to manage the boron concentration and reactivity safely.

Doing nothing and waiting for natural stabilization is not a mitigation action because it does not actively counter the reactivity increase and could allow the reactor to approach unsafe conditions.