Hiroshima_ The World's Bomb - Andrew J. Rotter [44]
The army-sponsored program, called the NI (for Nishina) Project, inched forward from May 1943 on. Located in Riken building number 49, put up the previous year in part as a mess hall, it was dedicated almost exclusively to the separation of U-235 through the time-consuming method of gaseous diffusion, such as Francis Simon had explored at Oxford. (The work was now more sophisticated than Simon’s experiments with the family kitchen strainer. Researchers were to make hexafluoride gas, then force it through a number of baffles, whose tiny holes were to admit the light 235 isotope while blocking the bulkier U-238.) The gas itself proved difficult to produce: much-qualified triumph came in January 1944, with the emergence of a hexafluoride crystal the size of a grain of rice. The entire process remained on a ludicrously small scale. Riken lacked the space, the money, the isotope separators, and even the electricity needed to create the fissionable uranium necessary for a bomb; Walter Grunden estimates that by early 1945 the lab would have needed 10 percent of the electrical power then available in the entire country to be successful. That February, Nishina placed what distillate his researchers had produced into one of his cyclotrons and blasted it with neutrons. No radioactivity resulted. Then, on 13 April, American bombers struck Tokyo. In the pre-dawn chill, hours after the planes had dropped their bombs and flown off, Building No. 49 suddenly burst into flames and was destroyed. That all but put an end to Japan’s atomic quest.
Its destruction was no great surprise, and at the time well down the list of Japanese disappointments and concerns. The Japanese government never expected to have an atomic bomb, and the military branches, working separately from each other, saw nuclear bombs as a prospect more remote than the fabrication of other fantastic weapons. Scientists like Nishina were unenthusiastic about the bomb, and others, including Kigoshi and his colleague Takeuchi, were in over their heads. Theoretical sophistication aside, Japanese scientists lacked the apparatus and materials they needed to do more than dream about an atomic bomb. By 1945, like their countrymen and -women, they were trying desperately to survive. (Dower observes that Kigoshi was finally so weak with hunger that he had trouble holding a test tube steady.) History might have remembered Japan’s pursuit of an atomic bomb as simple folly. In the aftermath of Hiroshima and Nagasaki, it seemed equally a grim irony.13
4. Germany’s nuclear projects
Scientists and statesmen in Europe and the United States were largely unaware of Japanese efforts to build a bomb, and they allowed themselves to be unaware because they were unconcerned at the prospect. The Japanese, the ‘little men’, were regarded with contempt in the West: they were able imitators of the inventions of others, it was said, but incapable of developing new, large-scale technologies on their own. This was not the view held of the Germans. Despite losing dozens of distinguished scientists as refugees from Nazism, Germany in the 1930s retained some of the best theoretical and experimental physicists in the world. Otto Hahn remained. Kurt Diebner led physics research at the Army Weapons Bureau and in the early years of the war took charge of uranium research at the Kaiser Wilhelm Institute in Dahlem. Paul Harteck, the physical chemist who predicted a powerful nuclear explosive in 1939, was at Hamburg; Carl Friedrich von Weizsacker, whose father, Ernst, was the second-ranking official in the German Foreign Office, was at