|Fig. 1: USS Minnesota (SSN 783). (Source: Wikimedia Commons)|
To further its influence as a global maritime force, the U.S. Navy introduced nuclear power into its submarine and aircraft carrier fleet starting in 1955 with the USS Nautilus (SSN 571). In 1982, Presidential Executive Order 12344 set forth the responsibilities of the Naval Nuclear Propulsion Program, including the research, development, safety, training, construction, maintenance, and disposal of nuclear propulsion systems throughout the U.S. naval fleet.  The program, commonly referred to as Naval Reactors (NR), aims at ensuring the safe and reliable operation of nuclear powered submarines, aircraft carriers, and their support facilities. Since its origin in 1955, nuclear power has provided the Navy with the mobility, flexibility, and endurance needed to carry out countless missions vital to national security. 
NR headquarters is located in Washington, D.C. and serves as the command center that directs all technical decision making in the procurement, operations, maintenance, training, and logistics for the Navy's nuclear propulsion systems. The organization is divided into two units: one housed within the Department of Energy and the other within the Department of the Navy. The director of NR leads both organizational units and has historically been an appointed U.S. Navy Admiral.
The U.S. Navy utilizes a pressurized water reactor (PWR) design for its nuclear propulsion plants, containing both primary and secondary system components. Uranium atoms in the reactor core undergo nuclear fission to produce heat, and that heat is transferred to high pressure water in the primary system closed loop. Next, the primary system water passes through a steam generator where it transfers its energy over to the secondary system before being pumped back to the reactor. The secondary system is also a closed loop and is isolated from the primary system. Operating at a lower pressure than the primary, the secondary system's water flashes to steam within the steam generator and drives a series of turbines to extract useful work. 
Private companies such as General Electric and Bechtel design and manufacture the reactor plant components for the nuclear power program. The manufacturing process to construct the elements of a reactor plant requires years of machining, welding, heat treatment, and testing. Due to the nature of warship operations, NR institutionalizes higher design and production standards for its naval reactors as compared to civilian reactors. The systems onboard naval vessels must be able to absorb battle shock, limit noise, accommodate personnel operating in close proximity to the reactor, and handle rapid changes in power. Figure 1 shows the Virginia-class submarine USS Minnesota (SSN 783), which contains General Electric's S9G reactor onboard. 
Electric Boat in Groton, CT and Huntington Ingalls Industries - Newport News Shipbuilding in Newport News, VA are two private shipyards that construct all of the Navy's nuclear powered ships. Alongside four public shipyards, these shipyards maintain, refuel, and overhaul the Navy's submarines and aircraft carriers. Additionally, tenders and support facilities are capable of performing minor maintenance and logistics support on nuclear powered ships outside of the shipyards. As naval vessels themselves, tenders can perform maintenance on forward deployed nuclear ships, thus enabling forces to remain on station for longer durations. 
The Naval Nuclear Laboratory is responsible for developing naval nuclear propulsion technology and providing technical support to ensure the safe operation of naval reactors. Within the Naval Nuclear Laboratory, Bettis and Knolls Atomic Power Laboratories are research and testing facilities for naval nuclear propulsion technology. Located in the Idaho National Laboratory, the Naval Reactors Facility examines spent nuclear fuel and looks to develop new technology based on its findings. The efforts from these labs have led to profound advances in naval reactor technology over the past several decades, which has empowered NR to maintain a record of over 151 million miles safely steamed on nuclear power without experiencing a nuclear incident. 
Naval Reactors' professional cadre of employees and demand for excellence have paved the way for the nuclear Navy's success over the years. The organization will continue to manage and lead the nuclear Navy into the future, as the role of submarines and aircraft carriers becomes even more prominent in today's increasingly complex battlefield.
© Christopher DiOrio. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 "Executive Order 12344 - Naval Nuclear Propulsion Program," U.S. Federal Register, 47 FR 4979, 3 Feb 82.
 "The United States Naval Nuclear Propulsion Program," U.S. Department of the Navy, March 2013.