MIT study could help predict graphite lifespan in nuclear reactors

A recent MIT study has advanced understanding of how graphite, a critical material in nuclear reactors, behaves under radiation. Graphite is widely used as a neutron moderator and reflector in reactors, playing a key role in sustaining controlled nuclear chain reactions. However, radiation exposure causes graphite to deform through swelling, shrinking, and cracking, complicating predictions of its lifespan. The MIT team applied a statistical method called the Weibull Distribution alongside X-ray scattering techniques to analyze irradiated graphite samples from Oak Ridge National Laboratory. Their research revealed unexpected pore behavior: initially, pores fill as graphite degrades, but over prolonged irradiation, a recovery or annealing process occurs where new pores form and existing pores smooth and enlarge, influencing the material’s volume changes. This discovery sheds light on graphite’s complex composite structure—comprising crystalline filler particles, a less crystalline binder matrix, and pores ranging from nanometers to microns—that affects its radiation response. The study’s findings could lead to more accurate, non-destructive predictions of graphite’s