  Although researchers have extensively studied student conceptions of
radioactivity, the conceptions held by pre-service teachers on this subject are
largely absent from the literature. We conducted a qualitative content analysis
of problem-centered interviews with pre-service teachers N = 13 to establish
which conceptions are held by pre-service teachers and to examine these
conceptions' structure in coordination classes. As has already been observed in
students, some pre-service teachers inadequately differentiate between
radioactive matter and ionizing radiation and between fission and decay. We
also observed that pre-service teachers tend to describe the activation of
materials due to ionizing radiation despite having previously denied an
activation, thus showing that the conception of activation of materials can
reemerge in particular framings. Within the interviews conducted, the concept
of energy emerged as a central coordination class regarding radioactivity. This
coordination class appeared across contexts and proved fruitful in explaining
pre-service teachers' conceptions about radioactivity. We will use the results
from this study to develop a teaching-learning laboratory for pre-service
teachers in which they can actively study high school students' conceptions
while reflecting on their own. In this way, these findings will contribute to
improving the structure of nuclear physics courses at the university.
