Manhattan Project
In September 1942, Lieutenant Colonel Kenneth Nichols met Sengier in his New York office. Nichols had been ordered to find uranium by the head of the Manhattan Project, General Leslie Groves. He asked if the Union Minière could supply uranium ore, and Sengier's answer became history: "You can have the ore now. It is in New York, a thousand tons of it. I was waiting for your visit." Nichols had heard of the ore from the State Department and Louis Rosen, but was surprised at the amount: 1,200 tons, of which 100 tons was to go to Canada immediately for refining by Eldorado Mining and Refining in Port Hope, Ontario.
Nichols and Sengier negotiated a contract, and the Staten Island stockpile was transferred to the United States Army. Since Tizard had informed him about uranium's potential a couple of years earlier, Sengier had a pretty good idea why Nichols had shown up to inquire about his ore deposits, something Nichols elaborated on during a 1965 Voices of the Manhattan Project interview by the journalist Stephane Groueff:
"He had been following some of the work done by the French scientists before the war, and he knew the importance of the uranium as a possibility. Sengier knew what the hell we were doing. He just said, "I think I know what you’re doing, but you don’t need to tell me. Just assure me it’s for military purposes.""
In his 1962 book about the Manhattan Project, Now It Can Be Told, Groves wrote that "as a Belgian, Sengier appreciated fully the absolute necessity of an Allied victory." Nichols, when questioned about Sengier's motives, stated:
"I think it was partly patriotic, partly commercial. Their main market at that time was radium, and they sold about 300 tons a year of uranium to the ceramics industry for coloring. I think his main interest was probably commercial, to have a radium supply in the US, in case Europe was overrun, as it was. He had shipped some stuff from the Congo to Belgium, which was captured by the Germans and Patton finally rescued it. You can get the story of that from Groves. Shipped a big bulk of it to the US, and stored in Staten Island. I think he realized it had a possible military significance, but also had a commercial significance. He was interested—I think he had some indications from other people that this project was continuing in the US, so I think he was interested in getting it into the right hands."
The Shinkolobwe mine had been closed since 1937, and had fallen into disrepair and flooded. The United States Army sent a squad from its Corps of Engineers to restore the mine, expand the aerodromes in Léopoldville and Elisabethville, and build a port in Matadi, on the Congo River. The army also secured the remaining ore (3000 tons) in Shinkolobwe, which was shipped to the United States. In his 1987 book, The Road to Trinity, Nichols wrote:
"Our best source, the Shinkolobwe mine, represented a freak occurrence in nature. It contained a tremendously rich lode of uranium pitchblende. Nothing like it has ever again been found. The ore already in the United States contained 65 percent U3O8, while the pitchblende aboveground in the Congo amounted to a thousand tons of 65 percent ore, and the waste piles of ore contained two thousand tons of 20 percent U3O8. To illustrate the uniqueness of Sengier's stockpile, after the war the MED and the AEC considered ore containing three-tenths of 1 percent as a good find. Without Sengier’s foresight in stockpiling ore in the United States and aboveground in Africa, we simply would not have had the amounts of uranium needed to justify building the large separation plants and the plutonium reactors."
The agreement between the United States, the United Kingdom, and Belgium lasted ten years and continued after the war. The uranium agreements in part explain Belgium's relative ease in rebuilding its economy after the war, as the country had no debt with the major financial powers.
