Neptunium-237 is a radioactive isotope of the element neptunium, which is part of the actinide series in the periodic table. It has a half-life of about 2.14 million years, making it one of the more stable isotopes of neptunium. Neptunium-237 is produced primarily in nuclear reactors and can be found in spent nuclear fuel. This isotope is significant in nuclear science and waste management because it can be used in the production of plutonium-238, which is utilized in radioisotope thermoelectric generators for space missions. Additionally, neptunium-237 is studied for its potential applications in nuclear medicine and as a tracer in environmental studies.