Shippingport Light Water Breeder Reactor

The Shippingport Light Water Breeder Reactor, which ran from 1977 to 1982, demonstrated that a thorium and uranium 233 core can breed fuel, ending with 1.39 percent more fissile material.

Core 3 at the Shippingport Atomic Power Station in Pennsylvania produced about 2.1 billion kilowatt hours of gross electricity over roughly 29,000 effective full power hours, and assay of 524 discharged fuel rods confirmed the gain in fissile inventory. Examiners found no fuel element defects. Power operation stopped on October 1, 1982, and the Department of Energy completed dismantlement in 1989 for $91.3 million.

Shippingport was the first full scale American reactor built only to make civilian electricity. Its third core used pellets of thorium oxide and uranium 233 oxide in Zircaloy 4 tubes, and it controlled reactivity by moving fuel in place of neutron absorbing control rods. That choice removed a source of parasitic neutron loss, and the loss was the margin that made breeding possible in light water.

For energy investors, utilities, and policy professionals, the record carries a plain commercial message. The physics worked in 1982. The fuel cycle around it needs recycled uranium 233, shielded fabrication, and reprocessing that has never operated at industrial scale, and those requirements kept the concept off the market. The federal outlay for the Shippingport pressurized water and breeder programs was estimated at $622.2 million in 1975, and the breeder core never entered commercial service.

Shippingport was exempt from licensing by the Nuclear Regulatory Commission, so no licensing record exists for a thorium fed light water reactor. A developer today would proceed under 10 CFR Part 50, Part 52, or the optional Part 53 that took effect on April 29, 2026, and uranium 233 is controlled as special nuclear material of the highest security category. The sections below trace the history, the engineering, the cost, the back end of the fuel cycle, three documented precedents, the strongest case against thorium breeding, and the decisions that follow for each audience.

Background and History

How Did Shippingport Become the First Full Scale Civilian Reactor in America?

Shippingport became the first full scale civilian power reactor in America because a cancelled aircraft carrier reactor was redirected to Pennsylvania in 1953. In April 1953 the Atomic Energy Commission proposed canceling the carrier propulsion reactor under development at the Westinghouse Bettis laboratory and moving its funds to a civilian power plant. On December 8, 1953 the President of the United States proposed the Atoms for Peace program before the United Nations General Assembly, and the Commission sought a utility partner to build the plant.

Duquesne Light Company won the partnership. Its bid supplied the land, the turbine generator, and $5.0 million toward light water reactor research, and the contract was signed in March 1954. Ground was broken on September 6, 1954 before about 1,400 guests, with the first scoop of earth activated by remote control from Denver. The Division of Naval Reactors under Rear Admiral Hyman Rickover held primary responsibility for the reactor, and the site sat on the Ohio River about 25 miles from Pittsburgh.

The reactor was a pressurized water design with a primary system near 2,000 pounds per square inch, four steam generators, and a single turbine. Rickover chose uranium dioxide fuel in Zircaloy cans over a uranium molybdenum alloy, and the choice became the standard for the civilian industry. The plant reached criticality at 4:30 a.m. on December 2, 1957, delivered first power to the grid on December 18, and reached its full 68,000 kilowatts on December 23, 1957.

What Happened to Core 1 and Core 2?

Core 1 and Core 2 proved the seed and blanket concept at commercial scale. Core 1 was installed in October 1957, weighed 58 tons, and carried 165 pounds of 93 percent enriched uranium as seed inside 14.2 tons of natural uranium as blanket, and it produced close to 2 billion kilowatt hours before replacement in 1964. Core 2 operated from February 3, 1965 to February 4, 1974, raised electrical capacity from 60,000 to 100,000 kilowatts, and produced almost 3.5 billion kilowatt hours. It used 20 seed assemblies with hafnium control rods and 77 blanket assemblies.

A turbine generator mechanical failure took the plant offline on February 4, 1974. The Energy Reorganization Act of 1974 split the Atomic Energy Commission in January 1975 into the Nuclear Regulatory Commission and the Energy Research and Development Administration, which held Naval Reactors, and the Department of Energy absorbed that administration in 1977.

Why Did the Atomic Energy Commission Build a Breeder Core for Shippingport?

The Commission approved the breeder research program in December 1965 as a path to stretch the uranium supply, since a reactor that made more fissile fuel than it consumed would need less mined ore. A 1961 advisory committee had already concluded that future plants needed to be far larger than 60 megawatts, and the Naval Reactors team studied designs of up to 750 megawatts. The Water Cooled Breeder Program ran from 1965 to 1987.

Fabrication of the breeder core finished in 1976 to 1977. The core reached initial criticality on August 26, 1977, and the President directed it to full power by closed circuit television on December 2, 1977. The 1975 audit had scheduled installation for early 1976, so the core arrived about a year late. It then ran for almost five years.

When uranium proved plentiful in the 1980s, the case for a breeder weakened. The plant ended power operation on October 1, 1982, and a 1980 landmark designation by the American Society of Mechanical Engineers recorded the facility’s place in the history of the profession. The core was removed, examined, and sent to Idaho, and the plant went to decommissioning