Editing Willard Libby (section)

==Manhattan Project==
On December 8, 1941, the day after the [[Japanese attack on Pearl Harbor]] brought the United States into [[World War II]], Libby volunteered his services to Nobel Prize laureate [[Harold Urey]]. Urey arranged for Libby to be given leave from the University of California, Berkeley and to join him at [[Columbia University]] to work on the [[Manhattan Project]], the wartime project to develop [[atomic bomb]]s,<ref name="Nobelprize.org"/><ref name="TIME" /> at what became its Substitute Alloy Materials (SAM) Laboratories.{{sfn|Hewlett|Anderson|1962|p=128}} During his time in the New York City area, Libby was a resident of [[Leonia, New Jersey]].<ref>{{cite news |url=https://query.nytimes.com/gst/fullpage.html?res=9E01EFDF113CF936A25755C0A961958260 |title=Well-Read, Well-Shaded and Well-Placed |newspaper=[[The New York Times]] |date=June 15, 1997 |access-date=March 30, 2011 |quote=Much later, its residents included five Nobel Prize winners, among them Enrico Fermi, one of the developers of the atomic bomb, and Willard Libby, who discovered radiocarbon dating; Sammy Davis Jr., Pat Boone and Alan Alda, the entertainers, and Robert Ludlum, the author }}</ref>

Over the next three years, Libby worked on the [[gaseous diffusion]] process for [[uranium enrichment]].{{sfn|Carey|2006|pp=231–232}} An atomic bomb required [[fissile]] material, and the fissile [[uranium-235]] made up only 0.7 percent of natural uranium. The SAM Laboratories therefore had to find a way of separating kilograms of it from the more abundant [[uranium-238]]. Gaseous diffusion worked on the principle that a lighter gas diffuses through a barrier faster than a heavier one at a rate inversely proportional to its molecular weight. But the only known gas containing uranium was the highly corrosive [[uranium hexafluoride]], and a suitable barrier was hard to find.{{sfn|Hewlett|Anderson|1962|pp=29–31}}

Through 1942, Libby and his team studied different barriers and the means to protect them from corrosion from the uranium hexafluoride.{{sfn|Hewlett|Anderson|1962|pp=99–100}} The most promising type was a barrier made of powdered [[nickel]] developed by Edward O. Norris of the Jelliff Manufacturing Corporation and Edward Adler from the [[City College of New York]], which became known as the "Norris-Adler" barrier by late 1942.{{sfn|Hewlett|Anderson|1962|pp=101, 126}}

In addition to developing a suitable barrier, the SAM Laboratories also had to assist in the design of a gaseous separation plant, which became known as [[K-25]]. Libby helped with the engineers from [[Kellex]] to produce a workable design for a pilot plant.{{sfn|Hewlett|Anderson|1962|pp=121–124}} Libby conducted a series of tests that indicated that the Norris-Adler barrier would work, and he remained confident that with an all-out effort, the remaining problems with it could be solved. Although doubts remained, construction work began on the K-25 full-scale production plant in September 1943.{{sfn|Hewlett|Anderson|1962|pp=130–134}}

As 1943 gave way to 1944, many problems remained. Tests began on the machinery at K-25 in April 1944 without a barrier. Attention turned to a new process developed by Kellex. Finally, in July 1944, Kellex barriers began to be installed in K-25.{{sfn|Hewlett|Anderson|1962|pp=137–141}} K-25 commenced operation in February 1945, and as cascade after cascade came online, the quality of the product increased. By April 1945, K-25 had attained a 1.1% enrichment.{{sfn|Jones|1985|pp=167–171}} Uranium partially enriched in K-25 was fed into the [[calutron]]s at [[Y-12 National Security Complex|Y-12]] to complete the enrichment process.{{sfn|Hewlett|Anderson|1962|pp=159–160}}

Construction of the upper stages of the K-25 plant was cancelled, and Kellex was directed to instead design and build a 540-stage side feed unit, which became known as K-27.{{sfn|Jones|1985|pp=158–165}} The last of K-25's 2,892 stages commenced operation in August 1945.{{sfn|Jones|1985|pp=167–171}}   On August 5, K-25 starting producing feed enriched to 23 percent uranium-235.{{sfn|Jones|1985|p=148}} K-25 and K-27 achieved their full potential only in the early postwar period, when they eclipsed the other production plants and became the prototypes for a new generation of plants.{{sfn|Jones|1985|pp=167–171}} Enriched uranium was used in the [[Little Boy]] bomb employed in the [[bombing of Hiroshima]] on August 6, 1945.{{sfn|Hewlett|Anderson|1962|pp=401–403}} Libby brought home a stack of newspapers and told his wife,  "This is what I've been doing."<ref name="TIME" />