General Groves oversaw the construction of the Pentagon, but more notably, directed the Manhattan Project that developed the atomic bomb during World War II.
Groves died on July 13, 1970, at 73 years of age. He is interred in Arlington National Cemetery, next to his brother, Allen, who died of pneumonia in 1916. Grace, his wife, was interred next to Groves in 1986.
The tombstone marks his participation in the Manhattan Project along with the insignia. The grave faces the Pentagon, which can be seen in the distance.
This Seederer-Kohlbusch scale, circa 1944, is found in a side room of the B Reactor at Hanford along with displays of other artifacts and mementos of the Manhattan Project. This is the original scale used to weigh the first milligrams of plutonium (Pu) produced at the facility.
In October 1943, construction began on the B Reactor at the Hanford Site in Washington, with the purpose of producing plutonium. Fuel slugs — uranium billets extruded into slugs and sealed in aluminum jackets — were then placed in the reactor for several weeks to a year. The reactor went critical on September 26, 1944. The first irradiated slugs were discharged from the reactor on December 25, 1944.
Fuel slugs were then removed from the reactor and placed in a 90-day underwater cooling off period before being transported by train to the Hanford T Plant, which began operations on December 26, 1944. Next, the bismuth phosphate process was used on the fuel slugs to separate the plutonium from uranium and other fission products. The final processed product was plutonium nitrate, which made for safer shipping to Los Alamos.
In late January, 1945, the first milligrams of plutonium produced at Hanford were weighed on this scale then sent by courier to Los Alamos for testing. Los Alamos received its first plutonium from Hanford on February 2, 1945.
Subsequently, Building D in the Tech Area at Los Alamos would purify and fabricate the plutonium nitrate received from Hanford into the highly purified metallic hemispheres used in the Trinity and Nagasaki devices.