Editing Manhattan Project (section)

=== X-10 Graphite Reactor ===
{{Main|X-10 Graphite Reactor}}
[[File:X10 Reactor Face.jpg|thumb|Workers load uranium slugs into the X-10 Graphite Reactor.|alt=Two workmen on a movable platform similar to that used by window washers, stick a rod into one of many small holes in the wall in front of them.]]
In March 1943, DuPont began construction of a plutonium plant on a {{convert|112|acre|km2|1|adj=on}} site at Oak Ridge. Intended as a pilot plant for the larger production facilities at Hanford, it included the air-cooled [[X-10 Graphite Reactor]], a chemical separation plant, and support facilities. Because of the subsequent decision to construct water-cooled reactors at Hanford, only the chemical separation plant operated as a true pilot.<ref name="Jones, pp. 204-206">{{harvnb|Jones|1985|pp=204–206}}.</ref> The X-10 Graphite Reactor consisted of a huge block of graphite, {{convert|24|ft|m}} per side, weighing around {{convert|1500|ST}}, surrounded by {{convert|7|ft|m}} of high-density concrete as a radiation shield.<ref name="Jones, pp. 204-206" />

The greatest difficulty was encountered with the uranium slugs produced by Mallinckrodt and Metal Hydrides. These had to be coated in aluminum to avoid corrosion and the escape of fission products into the cooling system. The Grasselli Chemical Company attempted to develop a [[tinning#Hot-dipping|hot dipping process]] without success. [[Alcoa]] tried canning, developing a new process for flux-less welding; 97% of the cans passed a standard vacuum test, but high temperature tests indicated a failure rate of more than 50%. Nonetheless, production began in June 1943. The Metallurgical Laboratory eventually developed an improved welding technique with the help of [[General Electric]], which was incorporated into the production process in October 1943.<ref>{{harvnb|Hewlett|Anderson|1962|pp=208–210}}.</ref>

The X-10 Graphite Reactor went critical on 4 November 1943 with about {{convert|30|ST}} of uranium. A week later the load was increased to {{convert|36|ST}}, raising its power generation to 500&nbsp;kW, and by the end of the month the first 500&nbsp;mg of plutonium was created.<ref>{{harvnb|Hewlett|Anderson|1962|p=211}}.</ref> Gradual modifications raised the power to 4,000&nbsp;kW in July 1944. X-10 operated as a production plant until January 1945, when it was turned over to research.<ref name="Jones 1985 209">{{harvnb|Jones|1985|p=209}}.</ref>