After prompt criticality in a water-moderated reactor, which mechanism initially reduces the fission rate?

💡 Explanation

Doppler broadening increases neutron absorption in uranium-238 because higher fuel temperatures cause greater thermal motion, which smears the resonance peaks, therefore increasing the effective resonance integral rather than control rods removing neutrons or delayed neutrons initiating reactions.

• Which consequence results when rapid outgassing overwhelms vacuum chamber's cryopump capacity?
• Which mechanism causes increased NOx formation when a gasoline engine operates lean with high compression ratio?
• During microwave communication, which mechanism introduces signal fading due to atmospheric conditions?
• Which risk increases when impedance mismatch occurs inside underground fiber optic data lines?
• Which risk significantly increases within a medical PET scanner undergoing prolonged use?
• Which risk increases during fiber optic communication cabling splices?