b'Moving BeyondNew characterization technique offers a structural integrity metric for reactor Displacements Perpressure vessel steels, which are critical for evaluating nuclear reactor safety Atom: A New Approachandlifetime.for Rapidly QuantifyingT he main objectives of this research were to develop and demonstrate a new experimental approach for directly measuring radiation RadiationDamage damage of irradiated reactor materials that augments the calculation of displacements per atom and elucidates the recovery mechanisms during controlled annealing of these materials when coupled with advanced simulation and modeling. This was successfully accomplished by developing advanced scanning calorimetric techniques, advanced characterization of pre- and post-annealed samples, and advanced molecular dynamics and kinetic Monte Carlo TOTAL APPROVED AMOUNT:models of the irradiated materials studied.$1,019,000 over 3 years This research resolved and interpreted previously unobservable defects in irradiated PROJECT NUMBER:metals through their energetic signatures. In neutron irradiated titanium, we 19A39-070 investigated the final radiation damage recovery stage using differential scanning calorimetry (DSC) and reported first-of-a-kind measurements of stored energy from PRINCIPAL INVESTIGATOR:radiation damage in titanium. Additionally, we discovered two distinct exothermic Scott Middlemas release peaks indicating the recovery mechanism involves two sub-stages, whereas CO-INVESTIGATORS: the previous radiation damage recovery model predicted one. Molecular dynamics Daniel Murray, INL simulations of defect annealing explored the corresponding defects for each process Michael Short, Massachusetts Instituteand were directly correlated to the experimental DSC results.of Technology In a neutron-irradiated reactor pressure vessel, DSC and Flash DSC annealing experiments were performed and correlated with the pre- and post-annealed primary elemental distribution and defect structure using atom probe tomography, transmission electron microscopy, and positron annihilation spectroscopy. DSC experiments were performed on boron-doped 316 steel and ion-irradiated silicon carbide cladding materials.(a) DSC measures defect energy release upon annealing. (b) Atom probe tomography reveals key microstructural information of neutron irradiated reactor pressure vessel steel.30'