National Nuclear Security Administration (NNSA) | 67,940 followers on LinkedIn. Peace Through Atomic Strength | Established by Congress in 2000, NNSA is a semi-autonomous agency within the U.S. Department of Energy that protects our nation by designing and delivering a safe, secure, reliable, and effective U.S. nuclear stockpile; forging solutions that enable global security and stability through nonproliferation and counterproliferation; responding to nuclear and radiological emergencies in the U.S. and abroad; providing nuclear propulsion to power a global U.S. Navy; and leveraging transformative technologies to address emerging challenges.