Twitter provides a complementary source of information to more traditional mechanisms of data collection of public opinion about technically complex and controversial topics like spent nuclear fuel (SNF) management. In this study, we apply content and network analysis to investigate the discourse surrounding public concerns about SNF management in the United States on Twitter during 2021. We explore two key research questions: (1) What issues do individuals bring up in the messages about SNF on social media platforms like Twitter? and (2) What can we learn from the network structure of online conversations about SNF management on Twitter? The results indicate that tweets about technology, community, health and safety, and legal and political topics consistently outpaced concerns about economic and environmental impacts connected to SNF management on Twitter, emphasizing potential risks more than benefits. This study also found that Twitter users’ conversations about SNF occur in tightly clustered groups of users centered around a small number of accounts. Together, the content and structure of the online discourse offers insight into public attitudes and concerns about SNF management from a variety of sources, providing experts with a baseline analysis of potentially salient issues that can inform communication with public audiences.