Page "Hanford Site" Paragraph 26

Construction on B Reactor began in August 1943 and was completed just over a year later, on September 13, 1944.

The reactor went critical in late September and, after overcoming nuclear poisoning, produced its first plutonium on November 6, 1944.

Plutonium was produced in the Hanford reactors when a uranium-238 atom in a fuel slug absorbed a neutron to form uranium-239.

U-239 rapidly undergoes beta decay to form neptunium-239, which rapidly undergoes a second beta decay to form plutonium-239.

The irradiated fuel slugs were transported by rail to three huge remotely operated chemical separation plants called " canyons " that were located about 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.

This first batch of plutonium was refined in the 221-T plant from December 26, 1944, to February 2, 1945, and delivered to the Los Alamos laboratory in New Mexico on February 5, 1945.