Portsmouth Gaseous Diffusion Plant is a facility located in Scioto Township, Pike County, Ohio, just south of Piketon, Ohio, that previously produced enriched uranium, including highly enriched weapons-grade uranium, for the United States Atomic Energy Commission (AEC), the U.S. nuclear weapons program, and Navy nuclear propulsion. In later years, it produced low-enriched uranium for fuel for commercial nuclear power reactors. The site never hosted an operating nuclear reactor.
The plant, so named because of its proximity to the city of Portsmouth, Ohio, approximately 22 miles south of the site, was one of three gaseous diffusion plants in the U.S., alongside the K-25 plant in Oak Ridge, Tennessee, and the Paducah Gaseous Diffusion Plant near Paducah, Kentucky. The plant was constructed between 1952 and 1956, with the first enrichment cells going online in 1954.
The former plant facilities are currently undergoing decontamination and decommissioning (D&D). Some site facilities are overseen by the United States Enrichment Corporation, a subsidiary of Centrus Energy. The D&D work on the older facilities to prepare the site for future use is expected to continue through 2024 and is being conducted by Fluor-B&W Portsmouth LLC.
Design The former gaseous diffusion plant covers of the site. The largest buildings – the process buildings – have a combined length of approximately , and cover about and contain of space. In use, the plant consumed a peak electrical demand of 2,100 megawatts.
Construction In August 1952, the United States Atomic Energy Commission (AEC) selected Scioto Township, a rural area occupied by family-owned farms, as the site for a new gaseous diffusion plant to produce highly enriched uranium, uranium-235, for use in military reactors and nuclear weapons production. Located near the junction of the Scioto and Ohio rivers, the site was chosen due to the economic availability of electric energy, availability of water for plant operation, adequate potential labor, suitable transportation facilities, geographic traits, and relative flatness of the topography.
The project was given expedited priority. Due to this prioritization, construction of the site had to start before all the architectural drawings for the site were completed. The Oak Ridge, Tennessee, operations of the AEC set up an organization designated "The Portsmouth Area" to direct construction and operation of the plant, select engineers and construction contractors, schedule delivery of critical materials and any other contingency. Uniform agreements were set up between labor and management to minimize the number of stoppages. Early planning and organization took place in improvised offices in city buildings in Portsmouth, including the National Guard Armory, the Elks City Club and the old farmhouses on the site itself. Nine architect engineer firms shared in the design of the plant, producing 12,000 design drawings, 40,000 construction drawings and 16,000 shop drawings. Advanced planning and scheduling were extremely important because the plant was designed to go into operation – or "on stream" – as soon as each unit or segment in a process building was completed while construction continued in other parts of the building.
Groundbreaking for the plant was on November 18, 1952. Earthmovers began leveling the rolling farmland for the building foundations on the same day. of structural steel, of reinforcing steel in the concrete floors, of process piping and of copper tubing were used in the construction of the three process buildings. An additional of tubing ran through the rest of the plant and into the control rooms. of concrete were required to complete the project. To support this, a separate concrete batching plant was constructed on plant site to serve all contractors; it produced of concrete per hour. In total, it took 70 million man hours for construction.
Two railroad lines, financing their own work, built spurs into the area to haul in building materials and heavy equipment, including of track on site. of roads were laid in the plant area, as well as a perimeter road that encircles the plant.
The original estimate for construction was four years at a cost of $1.2 billion. Construction was carried out by Peter Kiewit and Sons of Nebraska at a cost of $750 million. The site was completed several months ahead of schedule at 34% below the original cost estimate at a $400 million savings.
Operation Operations at the Portsmouth plant began in 1954 while construction was ongoing, with the plant coming fully online in early 1956 – several months ahead of schedule.
The primary mode of enrichment was the gaseous diffusion of uranium hexafluoride to separate the lighter fissile isotope, uranium-235 (U-235), from the heavier non-fissile isotope, uranium-238. The plant initially produced highly enriched uranium for the U.S. nuclear weapons program, but in the mid-1960s, the plant converted to low-enriched uranium fuel production for commercial nuclear power plants, where it took material from the Paducah Plant that had been enriched to 2.75% U-235 and further enriched it to approximately 4–5% for use in commercial nuclear power plants.
The plant had a capacity of 8.3 million separative work units per year (SWU/year) in 1984 in 4,080 stages. Three buildings – X-326, X-330 and X-333 – housed gaseous diffusion equipment, and three cooling tower complexes – X-626, X-630 and X-633 – were used to remove process heat. of water went through the 11 cooling towers daily, of which evaporated into the air. Water came from well fields installed at the Scioto River, supplying 40 million gallons per day when operating at full capacity.
To support operations, the AEC entered into a contract to become the largest single consumer/customer in the history of the electrical utility industry at that time. The plant set new records for single customer site usage with 18 billion kilowatt-hours annually, and demand peaking at more than 2,000 megawatts. The two largest private power plants in the world up to that time were built to supply the facility, one at Clifty Creek in Madison, Indiana, and another at Kyger Creek in Gallipolis, Ohio. They were also the most efficient coal-fired power plants in the world, producing one kilowatt-hour of electricity for every of coal. The power plants used of coal annually to support operations.
United States Enrichment Corporation (USEC, now Centrus) ceased gaseous enrichment operations at the Portsmouth plant in May 2001 after it consolidated operations at the Paducah plant in Kentucky. The following year, transfer and shipping operations were also consolidated in Paducah. Although USEC had nine years' time and had received the funding, it ceased the Portsmouth enrichment cascade in a dirty power-down, without purging the diffusion cells. Geoffrey Sea wrote in September 2013 that USEC's demise will be either by creditors (by the October 2014 loan repayment deadline), "regulators who find their spines" or by "repeal of the USEC Privatization Act by Congress".
Workers at the plant were represented by the Oil, Chemical and Atomic Workers International Union (OCAW).
Plant operator The plant was operated by the Goodyear Tire and Rubber Company from its startup until 1986, when the contract was taken over by Martin Marietta. In 1993, USEC took overall responsibility for the Paducah and Portsmouth enrichment plants, continuing the operating contract with Martin Marietta. In 1995, the operator became Lockheed Martin with the merger between it and Martin Marietta. In May 2001, the plant ceased gaseous diffusion enrichment operations and was placed in cold standby. In 2006, the site work shifted into cold shutdown transition in preparation for future decontamination and decommissioning (D&D). In 2011, after 10 years of maintaining the enrichment facilities in a safe shutdown condition and providing general sitewide services, USEC returned the gaseous diffusion plant facilities to the U.S. Department of Energy for decontamination and decommissioning.Portsmouth Gaseous Diffusion Plant Background. US Department of Energy. https://www.energy.gov/pppo/portsmouth-site/portsmouth-background
Depleted uranium conversion (DUF6) Depleted uranium – uranium material with a reduced percentage of the fissile isotope U-235 following processing in the form of depleted uranium hexafluoride (DUF6) – remains on site for continuing processing. The DUF6 Conversion facilities are located at both the Portsmouth Gaseous Diffusion Plant and the Paducah Gaseous Diffusion Plant. Each facility consists of four buildings – a conversion building, an administration building, a warehouse and a potassium hydroxide (KOH) regeneration building – as well as rail heads, five large acid storage tanks and lay-down areas for DUF6 steel cylinders. In 2002, DOE awarded Uranium Disposition Services, LLC (UDS) a contract to design, build and operate the DUF6 conversion plants to convert the DUF6 to uranium oxide and hydrofluoric acid. In December 2010, the DOE awarded Babcock & Wilcox Conversion Services LLC (BWCS) a contract to operate the DUF6 Conversion Plants through March 2016; it completed the transition of the contract for initial operations of the DUF6 Project in March 2011. Both plants were expected to be fully operational in fall 2011. As of June 2022, Mid-America Conversion Services is the operator of the facility.Home; Mid-America Conversion Services; https://duf6-mcs.com/; retrieved June 24, 2022.
Centrifuge separation enrichment Enrichment of isotopes of several elements was pursued using gas centrifuge technology prior to World War II. The DOE originally began developing gas centrifuge technology for mass production uranium enrichment in the early 1960s.
DOE Gas Centrifuge Enrichment Plant During the early 1980s, the DOE had begun construction of a centrifuge enrichment plant known as the DOE Gas Centrifuge Enrichment Plant (GCEP) at the Portsmouth site before abandoning the project in June 1985 after spending $3 billion. The major buildings constructed for the GCEP were left in place after the project cancellation.
American Centrifuge Lead Cascade Facility