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The Hanford Site is a facility of the government of the United States established to provide plutonium necessary for the development of nuclear weapons. It was established in 1943 as the Hanford Engineer Works, part of the Manhattan Project, and codenamed "Site W." No longer used to produce plutonium, it is currently the United States' most contaminated nuclear site.
The site occupies 586 square miles (1,517 km²) in Benton County, south-central Washington, and is approximately equivalent to half the total area of the state of Rhode Island (centered on.) The Federal government bought the towns of White Bluffs and Hanford and all of the surrounding farmland and orchards, and evacuated the residents to make room for the site.
Plutonium manufactured at the Hanford site was used to build the first nuclear bomb, which was tested at the Trinity site near Alamogordo, New Mexico, and used to build Fat Man, the bomb that was dropped on Nagasaki, Japan.
Currently, the Hanford Site is engaged in the world's largest environmental cleanup, with many challenges to be resolved in the face of overlapping technical, political, regulatory, and cultural interests. The cleanup effort is focused on three outcomes: restoring the Columbia River corridor for other uses, converting the central plateau to long-term waste treatment and storage, and preparing for the future.
Although most of the original Hanford Site is in Benton County, approximately twenty percent was once across the Columbia River in Grant and Franklin counties. This land has since been returned to private use and is now covered with orchards and irrigated fields. In 2000, large portions of Hanford were turned over to the Hanford Reach National Monument.
History of the Hanford Nuclear Site
The Uranium Committee of the federal Office of Scientific Research and Development (OSRD) decided to sponsor an intensive research project on plutonium. At this time, plutonium was a rare element that had been isolated in a University of California laboratory only nine months prior. The OSRD placed the contract with the University of Chicago Metallurgical Laboratory (Met Lab). Communities surrounding the Hanford Nuclear Reservation in southeastern Washington were exposed to radionuclides, particularly iodine-131, released during the period 1945 to 1951.
Selecting the Hanford Site
In June 1942, the Army Corps of Engineers formed the Manhattan Engineer District (MED) to construct industrial-size plants to manufacture the plutonium and uranium for the Met Lab scientists. In November 1942, the DuPont Company was recruited, and reluctantly agreed, to be the prime contractor for the construction of the facility. DuPont recommended that the plutonium production facilities be located far away from the existing uranium production facilities at Oak Ridge, Tennessee, and described the ideal site:
Although General Leslie Groves considered five other locations, the Hanford Site was chosen in December 1942 as "ideal in virtually all respects" (Matthias 1987), except for the farming towns of White Bluffs and Hanford. General Groves then established the Hanford Engineer Works. Beginning in February 1943, the Federal Government acquired 670 square miles (1,740 km²) from ~1,300 people (Gephart 2003). Because of wartime food shortages, the Manhattan Project used American prisoners to harvest the fields and orchards.
The Hanford Engineer Works (HEW) broke ground in March 1943, and immediately launched a massive construction project. Before the end of the war in August 1945, the HEW built 554 buildings (in addition to building living quarters and the City of Richland, Washington), including:
The Hanford Engineer Works used 780,000 cubic yards (600,000 m³) of concrete and 40,000 tons of structural steel and consumed US$230 million dollars between 1943 and 1946.
Building the reactors
The DuPont Company started to build the first Hanford nuclear reactor, B pile (building 105-B), in August 1943. (Fission reactors were originally called "piles".) Construction was completed more than a year later, on September 13, 1944. Testing started on July 12, 1944, and B pile was charged with uranium slugs on September 26, 1944 (Gephart 2003). The uranium slugs were short cylinders, 8 inches (20.3 cm) tall with a 1.4 inch (3.55 cm) diameter (Gephart 2003). Plutonium production began on September 26, 1944 (Gephart 2003). B reactor went critical in late September 1944, and after overcoming nuclear poisoning, produced its first plutonium on November 6, 1944. This plutonium was then refined in the 221-T plant and shipped to Los Alamos, beginning on December 26, 1944 (Gephart 2003). The first shipment was on February 5, 1945, leading the way to future shipments which were used in the Trinity Test and Fat Man, the bomb dropped on Nagasaki, Japan.
After starting construction on B pile, DuPont started construction on two identical reactors, 105-D, which started production in December 1944, and 105-F, which started production in February 1945. All three reactors (105-B, 105-D, and 105-F) initially operated at 250 megawatts (MW).
As no one had ever built an industrial-scale reactor before, the scientists and the DuPont engineering team were unsure how much heat would be generated by fission during normal operations. Seeking the greatest margin of error, DuPont engineers installed ammonia-based refrigeration systems with the 100-D and 100-F reactors to further chill the river water prior to its use as the reactor coolant.
Plutonium separation plants
Plutonium was produced in the Hanford reactors when a U-238 atom in a fuel slug absorbed a neutron to form U-239. The U-239 rapidly undergoes beta decay to give Np-239, which rapidly undergoes a second beta decay, giving Pu-239. The irradiated fuel slugs were transported by rail to three huge remotely operated chemical separation plants called "canyons", that were located about 10 miles (16 km) away. A series of chemical processing steps separated the small amount of plutonium that was produced from the remaining uranium and the fission waste products.
After the plutonium was extracted and refined in these plants, it was delivered to Los Alamos for use in the Trinity test device and the "Fat Man" bomb dropped on Nagasaki, Japan.
One issue the duPont team needed to tackle with these plants was that once they began processing irradiated slugs, the machinery would become radioactive to the point that it would be unsafe for humans ever to come in contact with it. They therefore had to devise methods to allow for replacement of any component via remote control. They came up with a modular cell concept, which allowed major components to be removed and replaced entirely by an operator sitting in a heavily shielded overhead crane. The method required early practical application of two technologies quite familiar to us today: Teflon, used as a gasket material, and closed-circuit television to give the crane operator a better view of what he was doing.
On March 10, 1945, a Japanese fire balloon descended in the vicinity of the site. This balloon caused a short circuit in the power lines supplying electricity for the nuclear reactor cooling pumps, but backup safety devices restored power almost immediately.
Cold War era
During the Cold War, the HeW built H-Reactor, with 400 MW, that started in 1949, and DR (for D-Replacement) Reactor, with 250 MW, started up in 1950. C-Reactor (105-C), at 600 MW, was located next to B-Reactor and started in 1952, and soon became the chief development and testing machine at the Hanford site. Within three months of its startup, C-Reactor's primary function was experimentation for the design of the "twin" K-Piles (KE and KW) - the 1955 "jumbos", each outputing 1,800 MW.
By the early 1960s, extensive modifications and upgrades had allowed the five reactors that were built in the 1940s to achieve power levels ranging from 2,015 to 2,210 MW each, C-Reactor achieved a power level of 2,500 MW, and the K-Piles achieved power levels of 4,400 MW each.
The Hanford B-Reactor continued to operate during the Cold War and produced tritium for the hydrogen bomb. B-Reactor was deactivated on February 12, 1968. Since then, most of the surrounding structures have been removed and buried and the other Hanford reactors have been entombed ("cocooned") to allow radioactivity to decay. The B-reactor has not been mothballed and is planned to become a museum.
All nine nuclear reactors were built along Hanford Reach on the Columbia River. With an average individual life span of 22 years, the reactors were closed down between 1964 and 1987.
The Hanford reactors required a huge volume of water from the Columbia River to dissipate the heat that was produced by the nuclear reactions. Huge water systems drew cooling water from the Columbia River and after treating this water for use by the reactors, returned water to the river. Before being pumped back into the river, the used water was held in large tanks known as retention basins for up to six hours. Longer-lived isotopes were not affected by this retention, and several terabecquerels entered the river every day. By the early 1960s, there were protests from the health departments of Oregon and Washington, as well as the U.S. Public Health Service. There were also numerous gas plumes of radioactive steam, which threw toxic iodine isotopes into the air.
Because of the demands for increased plutonium production, the Hanford Reactors had an increasingly severe problem with "slug failures"—the undesirable penetration of a fuel element's aluminum jacket by cooling water that caused the uranium to swell and block the coolant flow within the process tube and melt the slugs within that tube. No slug failures occurred during World War II, but by December 1945, 125 slugs with "blisters" had been found by visual inspection in the irradiated fuel storage basins at the rear of the three reactors. For the next seven years, blistered and ruptured fuel elements were opened and examined using a special underwater lathe in steel tanks located in the 111-B Test Building. After the 327 Post Irradiation Test Facility was ready, with its hot cells, the 111-B Building continued to be used as an examination facility for sections of corroded and failed process tubes.
When fuel ruptures did occur, the process tube containing the failure was emptied into the irradiated fuel storage basin. Sometimes, severe ruptures had to be removed with a rotary reamer and a hydraulic ram, with the damaged process tube then split with a special tube splitter, and then pulled out and chopped into short lengths with a unique Hanford Site instrument known as the "guillotine".
During the 25 years that the site operated, many puzzles relating to the practicalities of nuclear piles were solved and new machines developed to improve operating efficiencies. However, while technical operating challenges progressed well, waste disposal solutions remained elusive, and effluents continued to be released to the Columbia River.
Most of Hanford's reactors were shut down in the 1960s but nuclear waste still remains at the site. Parts of the 560 square mile (1,450 km²) site are highly contaminated. Examples of the scale of the problem are:
Cleanup to a nationally accepted level will likely take until 2030 and cost at least $50 billion.. At present, about 11,000 workers work to consolidate, clean up, and mitigate waste, contaminated buildings, and contaminated soil.
Under the present cleanup plan, lower-level hazardous wastes are buried in huge lined pits that are sealed and that will be monitored with sophisticated instruments for many years. The high-level nuclear waste, as well as tanks full of highly toxic chemicals, pose a much more difficult problem. As an example, plutonium has a half-life of 24,100 years, and a decay of ten half-lives is required before a sample is considered to be safe. Disposal of plutonium and other high-level radioactive wastes and toxic chemicals is a difficult problem that continues to be a subject of intense debate. The Department of Energy is currently building a vitrification plant on the Hanford site. Vitrification is a method that will combine these dangerous wastes with glass to render them stable. Bechtel, the San Francisco based construction and engineering firm, has been hired to construct the Vit Plant, which will cost approximately $12 billion and will be operational in 2019. Construction began in 2001.
Clean land released to other uses
Although uranium enrichment and plutonium breeding have been slowly phased out at Hanford, its strong legacy remains in Richland, Washington, which was transformed from a sleepy farm town to a bustling city by the Hanford project. As the nearest city to the site, the feat of feeding the United States' vast nuclear program in a cold war world created a strong community of highly skilled scientists and engineers.
Hanford became the location of the Department of Energy Pacific Northwest National Laboratory owned by the United States government and operated by Battelle Memorial Institute just north of Richland. A map of the site can be found on the Benton County Emergency Services web site
Other facilities located at Hanford Site:
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hanford_Site". A list of authors is available in Wikipedia.|