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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Bismuth phosphate process | 1/2 | https://en.wikipedia.org/wiki/Bismuth_phosphate_process | reference | science, encyclopedia | 2026-05-05T13:04:37.315754+00:00 | kb-cron |
The bismuth-phosphate process was used to extract plutonium from irradiated uranium taken from nuclear reactors. It was developed during World War II by Stanley G. Thompson, a chemist working for the Manhattan Project at the University of California, Berkeley. This process was used to produce plutonium at the Hanford Site. Plutonium was used in the atomic bomb that was used in the atomic bombing of Nagasaki in August 1945. The process was superseded in the 1950s by the REDOX and PUREX processes.
== Background == During World War II, plutonium was used to make both the first atomic bomb ever to be detonated (near Alamogordo, New Mexico) and the atomic bomb that was dropped on Nagasaki in Japan. Plutonium had only been isolated and chemically identified in 1941, so little was known about it, but it was thought that plutonium-239, like uranium-235, would be suitable for use in an atomic bomb.
== Producing plutonium on an industrial scale == Plutonium could be produced by irradiating uranium-238 in a nuclear reactor, but developing and building a reactor was a task for the Manhattan Project physicists. The task for the chemists was to develop a process to separate plutonium from the other fission products produced in the reactor, to do so on an industrial scale at a time when plutonium could be produced only in microscopic quantities, and to do so while working with dangerously radioactive chemicals like uranium—the chemistry of which little was known—and plutonium, the chemistry of which almost nothing was known.
== Experiments with separation methods == Chemists explored a variety of methods for separating plutonium from the other products that came out of the reactor:
Glenn Seaborg, one of the chemists who had first isolated and chemically identified plutonium, used lanthanum fluoride to perform the first successful separation of a weighable quantity of plutonium in August 1942. This lanthanum fluoride process became the preferred method for use in the Manhattan Project's plutonium separation semiworks at the Clinton Engineer Works and the production facilities at the Hanford Site, but the bismuth phosphate process was eventually adopted instead because further work revealed a variety of difficulties with the lanthanum fluoride process: Recovering the precipitate through filtration or centrifugation was difficult. The lanthanum fluoride process required large quantiles of hydrogen fluoride, which corroded equipment. There were problems stabilizing plutonium in its hexavalent state in the fluoride solution (discovered by Charles M. Cooper of DuPont, who would be responsible for the design and construction of the facilities). Isadore Perlman and William J. Knox Jr. looked into peroxide separation because most elements form soluble peroxides in neutral or acid solution. They soon discovered that plutonium was an exception. After a good deal of experimentation, they found that they could precipitate plutonium by adding hydrogen peroxide to a dilute uranyl nitrate solution. They were then able to get the process to work, but it produced tons of precipitate, in contrast to the lanthanum fluoride process that produced only kilograms. John E. Willard tried an alternative approach, based on the fact that some silicates absorbed plutonium more readily than other elements. This method worked but with low efficiency. Theodore T. Magel and Daniel K. Koshland Jr. researched a solvent-extraction processes. Harrison Brown and Orville F. Hill experimented with separation using volatility reactions, based on how uranium could be readily volatilized by fluorine.
== Discovery and adoption of the bismuth phosphate process == While the chemical engineers worked on these problems, Seaborg asked Stanley G. Thompson, a colleague at Berkeley, to have a look at the possibility of a phosphate process because it was known that the phosphates of many heavy metals were insoluble in an acid solutions. Thompson tried phosphates of thorium, uranium, cerium, niobium and zirconium without success. He did not expect bismuth phosphate (BiPO4) to work any better, but when he tried it on 18 December 1942, he was surprised to find that it carried 98 percent of the plutonium in solution. The crystalline structure of bismuth phosphate is similar to that of plutonium phosphate, and this became known as the bismuth phosphate process.
Cooper and Burris B. Cunningham were able to replicate Thompson's results, and the bismuth phosphate process was initially adopted as a fallback in case the lanthanum fluoride process could not be made to work. The processes were similar and the equipment used for lanthanum fluoride could be adapted for use with Thompson's bismuth phosphate process. In May 1943, the DuPont engineers decided to adopt the bismuth phosphate process for use in the Clinton semiworks and the Hanford production site.
== Discovery of plutonium's two oxidation states == As Brown, Hill, and other chemists explored plutonium chemistry, they made the crucial discovery that plutonium has two oxidation states, a tetravalent (+4) state and a hexavalent (+6) state, which have different chemical properties that could be exploited. (This work was performed at the Manhattan Project's Radiation Laboratory at the University of California, Metallurgical Laboratory at the University of Chicago and Ames Laboratory at Iowa State College.)
== Process ==