Ion-beam-assisted characterization of quinoline-insoluble particles in nuclear graphite

TL;DR

This study uses ion-beam-assisted SEM analysis to investigate quinoline-insoluble particles in nuclear graphite, revealing their microstructural evolution and distribution differences that influence irradiation behavior.

Contribution

It introduces a combined ion irradiation and SEM method to analyze QI particles in graphite, providing new insights into their microstructural changes and effects on dimensional stability.

Findings

QI particles become hillocks after irradiation

Higher QI concentration in NBG-18 reduces dimensional shrinkage

Densified QI spheres have weak bonding with graphite

Abstract

The irradiation behavior of graphite is essential for its applications in nuclear industry. However, the differences between graphite's behaviors are not well understood because of the very limited knowledge of microstructural differences between graphites. One typical structure, quinoline insoluble (QI) particle, was investigated using IG-110 and NBG-18 graphite. After irradiation, the QI particles on the polished surface were proved to become hillocks and can be easily identified by using a scanning electron microscope (SEM). Thus a method combining ion irradiation and SEM characterization was proposed to study the distribution and concentration of QI particles in graphite. During irradiation, the QI particles were found to evolve into densified spheres which have weak bonding with the surrounding graphite structures, indicating that the densification of QI particles does not contribute obviously to graphite dimensional shrinkage. A much higher concentration of QI particles in NBG-18 than IG-110 was characterized and is suggested to be responsible for the smaller maximum dimensional shrinkage of NBG-18 than IG-110 during irradiation.