The Bettis Atomic Power Laboratory (BAPL) is operated for the Department of Energy by Bechtel Bettis, Inc., and was formerly operated by Westinghouse Electric Corporation. Bettis is engaged solely in the design and development of naval nuclear propulsion plants. The Naval Nuclear Propulsion Program is a joint Navy/DOE program responsible for all matters pertaining to Naval nuclear propulsion. This Program is distinct from the remainder of DOE both by Presidential Executive Order and by statute.

The Lab provides technical support for the safe and reliable operation of existing Naval reactors. Bettis designed reactor plants for the first nuclear-powered submarine (USS Nautilus), the first nuclear-powered aircraft carrier (USS Enterprise), all of the Nimitz-class aircraft carriers, and the USS Seawolf.

On 10 December 1948 the Atomic Energy Commission (AEC) awarded a contract to Westinghouse to develop, design and construct, test and operate a land-based prototype water-cooled reactor power plant suitable for submarine propulsion. This prototype became known as the S1W or Mark 1. Final shutdown of the S1W prototype occured on 17 October 1989.

A major new initiative for the Laboratory is design of the nuclear propulsion plants and electrical power systems for the next class of US Navy aircraft carriers.

Activities relating to naval nuclear propulsion systems are performed in accordance with the requirements and authority of the Naval Nuclear Propulsion Program, a joint DOE and U.S. Department of Navy program responsible for all activities relating to naval nuclear propulsion. BAPL operations include development and testing of nuclear fuel materials and reactor materials, including radiochemical analysis.

Pressurized Water Reactors [PWR] were originally designed by Westinghouse Bettis Atomic Power Laboratory for military ship applications, then by the Westinghouse Nuclear Power Division for commercial applications. The first commercial PWR plant in the United States was Shippingport, which was located near Pittsburgh, Pennsylvania.

Located south of Pittsburgh in Large, PA, Pittsburgh Materials Technology Inc. (PMTI) was formed in 1993 from a unit of Westinghouse. The Large PA site where PMTI is now located was built by Joseph Large, Jr., who began distilling Monongahela Pure Rye whiskey there in 1795. During World War II, the distillery made alcohol for the war effort. Westinghouse Electric Corporation, as operator of the Bettis Atomic Power Laboratory, began using the site in 1951 for materials processing operations related to the Navy nuclear submarine effort. In the late 50's, the nation began working on space nuclear propulsion and Westinghouse established the Astronuclear Laboratory to participate in this effort. In 1961, Astronuclear was awarded a contract to design and build a Nuclear Engine for Rocket Vehicle Application (NERVA). The Large site became the focus for that effort.