A fission reactor is a device that harnesses the power of nuclear fission to generate electricity. There are several synonyms for this term, including nuclear reactor, atomic reactor, and atomic pile. While the principle behind all these terms is the same, each has its own connotations and history. For instance, 'atomic pile' refers to the first experimental nuclear reactors built during the Manhattan Project, while 'nuclear reactor' is a more generic term that can refer to both fission and fusion reactors. Whatever name you use, these devices remain a vital part of our energy infrastructure, providing clean, reliable, and low-carbon electricity to millions of homes and businesses around the world.