Dresden 2026 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 12: Materials for the Storage and Conversion of Energy III / Functional Materials I

MM 12.7: Talk

Tuesday, March 10, 2026, 12:00–12:15, SCH/A216

Positron Annihilation Studies of Nuclear and Highly Oriented Pyrolytic Graphite — •Jagoda Urban-Klaehn, Arvin Cunningham, and William Windes — Idaho National Laboratory, 1955 Fremont Ave, Idaho Falls, ID 83415 USA

Graphite is a life-limiting component in nuclear reactor design thus its microstructure characterization and the effects of extreme conditions are of great importance.

We examined nuclear graphite materials of different origin, porosity and grain sizes by use of Positron Annihilation Lifetime Spectroscopy (PALS).

We determined that each type of graphite has its specific signature with trapping lifetimes in the range: 360-410 ps, and the most important factor was the grain size. Graphite with the coarse grain showed less positron trapping compared to fine grain which agrees with literature.

Graphite that was heat-treated (2300 C) showed a significant increase in positron trapping thus changes in the microstructure. PALS studies on Highly Oriented Pyrolytic Graphite (HOPG) polycrystalline specimens showed less trapping due to its polycrystalline nature. We are planning to use ELBE slow positron beam at different temperatures to study isotropic graphite defects formation enthalpy as well as crystalline graphite*s depth profiling.

Keywords: nuclear graphite; positron annihilation; Highly Oriented Pyrolytic Graphite; micro-structure; extreme conditions