The urgency to address climate change and the diminishing sustainability of fossil fuels has propelled nuclear energy into the forefront of global energy solutions. This advanced textbook aims to provide nuclear science and engineering students with a holistic view and mechanistic understanding on the underlying nuclear physics processes. Based on the award-winning classes the authors have been teaching to first-year graduate students at MIT Nuclear Science and Engineering Department, this book aims to equip the next-generation nuclear scientists and engineers with the knowledge and insights needed to harness the vast potential of nuclear energy responsibly and innovatively. Through the pages of this book, students will journey into the heart of nuclear physics, exploring its foundational principles and the recent technological advancements that promise to redefine our energy future. Numerous Questions, Problems, and research-project-level Capstone Projects are added to facilitate active learning. Fundamentals such as quantum mechanics and latest progress such as machine learning and fusion breakthroughs are introduced in a balanced manner. Our goal is to provide a thorough grounding in the subject matter, preparing students to tackle the challenge on global climate change from a perspective of nuclear radiation interactions.