As a physicist who has vested my career in energy research, the claim that nuclear energy will never be cost-effective is one I have heard countless times but refuse to believe. The importance of safe and efficient power generation to energy security — and national security — challenges me to push the boundaries of what is possible. Nuclear energy is by far the largest source of clean, non-intermittent electricity in the United States. We have more reactors than any other nation and produce over 25% of the global supply of nuclear power. But nuclear energy isn't just important to the U.S. — it also plays a critical role in energy markets around the world. As of 2015, 13 countries relied on nuclear energy to provide at least 25% of their electricity. One thing is clear: The world needs nuclear.