Recently, the significance of learners' informal reasoning on socio-scientific issues has received increasing attention among science educators. To gain deeper insights into this important issue, an integrated analytic framework was developed in this study. With this framework, 71 Grade 10 students' informal reasoning about nuclear energy usage was explored qualitatively and quantitatively. It was found that the students in this study tended to process reasoning from multiple perspectives, and most of them were prone to make evidence-based decisions. However, less than 40% of the participants were able to construct rebuttals against counter-arguments. It was also revealed that students' abundant usage of supportive arguments did not guarantee for their counter-argument construction as well as rebuttal construction, but their usage of counter-arguments might act as precursors to their construction of rebuttals. In addition, learners' usage of multiple reasoning modes might help them propose more arguments and, in particular, generate more counter-arguments, which may act as precursors to their rebuttal construction. This study also showed evidence that students' scientific knowledge that might be mainly acquired from school science instruction could be viewed as important foundation for better informal reasoning and decision-making on socio-scientific issues. (Contains 1 note, 11 tables, and 2 figures.)