The Stored Energy Fingerprints of Radiation Damage
Tesi esterna in azienda
Riferimenti esterni Michael Short - MIT Cambridge (MA) - USA
Gruppi di ricerca ESSENTIAL
Tipo tesi COMPUTAZIONALE/SPERIMENTALE
Descrizione The current unit of radiation damage, the displacements per atom (DPA), is a calculated exposure parameter that does not directly yield the defect populations responsible for irradiation-induced material properties. Were an 'a posteriori' measure of radiation damage to exist, it would help to answer numerous, lingering questions about the nature and effects of irradiation. We propose the use of stored energy fingerprints as this new, more descriptive unit of radiation damage. They can be measured after irradiation, and they are hypothesized to yield information about the resulting defect populations. We present a combination of timeaccelerated molecular dynamics (MD) simulations and nanoscale differential scanning calorimetry (nanoDSC) measurements, which together paint a more measurable picture of the multiscale nature of radiation damage. Potential applications range from settling the question of neutron/ion irradiation equivalency, to quantitatively understanding dose rate effects, to verification of historical uranium enrichment 
A first part of the project will simply collect previous work done at MIT [e.g. 2], analyzing the defects that were formed during simulated irradiation in fusion-relevant materials, finding the average energies of each type of defect that forms in the materials. Previous work found out that, as the PKA energy increased, the average energy of each defect remained constant, but the amount of clustering and the number of dislocations increased. Defect clusters and dislocations each had their own energies associated with them, allowing for some differentiation in defects solely based on the stored energy.
Calorimetry heating was also simulated on the irradiated materials, showing the effect that the heating rate has on the process. The simulations allow for extrapolation to experimental heating rates.
Further work at the Mesoscale Nuclear Materials Laboratory, in which the proponent would like to be involved, deals with irradiating single crystal metals and performing nanocalorimetry on the obtained samples, thus working to obtain the energy stored in each material due to irradiation. The long-term goal is to determine if this metric, the Wigner energy, is a viable way of measuring radiation damage, and if so, it will allow for a better, more universal understanding of how irradiation affects materials.
Conoscenze richieste Eccellenza in impianti nucleari, modellistica, interazione radiazioni-materia
Scadenza validita proposta 23/10/2024 PROPONI LA TUA CANDIDATURA