Nuclear reactor fears eased as US lab clears graphite of safety risk

Researchers at Oak Ridge National Laboratory (ORNL) have resolved a decades-old debate regarding the impact of microscopic pores in graphite used in nuclear reactors. Their study, published in the journal Carbon, confirms that the natural porosity within graphite blocks does not affect the material’s atomic vibrations or its fundamental neutron moderation properties. This finding is significant because graphite has been a key component in nuclear reactors since the first reactor in 1942, valued for its ability to withstand extreme temperatures and slow down neutrons to sustain controlled nuclear chain reactions. The research provides greater confidence in the safety and design of current and next-generation reactors, including very high-temperature reactors (VHTRs) and molten salt reactors. The study addressed a critical flaw in previous models that treated graphite porosity by randomly removing atoms, which artificially distorted the material’s vibrational properties and led to overestimations in reactor criticality calculations. Using advanced neutron scattering experiments combined with machine-learned atomic potentials, the ORNL team demonstrated that the increased neutron