However, their research left them a useful legacy. By the time the war ended, Canada had the second largest nuclear research establishment in the world, overshadowed only by the United States. Their work on constructing nuclear reactors led to the building of the NRX (National Research eXperimental) reactor at the Chalk River Laboratories near Ottawa. It remained the world’s largest nuclear reactor for many years and soon began producing radioisotopes. Those are still used today to diagnose and treat cancer, and Canada has since been the world’s largest exporter of radioisotopes. Another reactor ten times as large was soon under construction and this became the NRU (National Research Universal) reactor. When it began work in 1957 it was, like NRX, the most powerful reactor in the world, and remained so for many years.
The United States, however, became the focus of nuclear research and was destined to become the first nation to exploit the power of the atom. In 1939, Albert Einstein wrote a key letter that was delivered personally to the President. In it he stated: ‘A single [atom] bomb might well destroy a city and some of the surrounding territory’. President Roosevelt was impressed, and he immediately appointed Lyman Briggs at the National Bureau of Standards to set up the ‘Uranium Committee’. Once the recommendations of the Maud Committee had been discussed, and the Americans knew that a bomb could be built with far smaller amounts of fissile materials than anyone had realized, it was decided to press ahead urgently with development. In 1942 this led to the Manhattan Engineer Project which had the express aim of producing an atomic bomb. The project derived its name from the concentration of expertise in Manhattan itself. Within the borough there were some ten research sites, almost all of which stand to the present day. Their original headquarters were in a skyscraper adjacent to City Hall. Little has ever been said about these establishments since; the tourist or investigator will find little to remind today’s citizens of what went on. A historian of the period, Dr Robert S. Norris, says that as many as 5,000 staff were coming and going. Each person knew only enough to do their job — few had any sort of overview.
The scientists originally on the committee were from various nations: the United States, Germany, Hungary, Italy, Denmark, Switzerland and Britain. To the British, where the research had made most progress, it seemed timely to shift the work to America where there were more resources, and where — unlike Britain — the industrial and research establishment was not overrun by the need simply to survive the onslaught of Germany. In the United States there was an immediately warm response to the project. Soon, however, the disparate nature of the nationalities involved was seen as problematical. Many of the British team had family in Europe, including some in nations that were now enemies of the Allied cause. The Americans felt that this could compromise security, and soon took over the project.
They envisaged two types of atom bomb, one using uranium, the other plutonium. Work began at once on constructing an atomic pile under the leadership of a brilliant physicist, Enrico Fermi. It was called Chicago Pile-1 (CP-1) and stood on a rackets court under the abandoned west stands of the original Alonzo Stagg Field stadium at the University of Chicago. In December 1942 the first sustained nuclear reaction was started — and the dream of atomic power was known to be real. America could now produce the isotopes (like U-235) she needed to plan an atomic bomb.
Discoveries of which the people of the United States are not aware may affect the welfare of this nation in the near future. The liberation of atomic power which had been achieved places atomic bombs in the hands of the Army. It places in your hands, as Commander-in-Chief, the fateful decision whether or not to sanction the use of such bombs in the present phase of the war against Japan.
We, the undersigned scientists, have been working in the field of atomic power. Until recently, we have had to fear that the United States might be attacked by atomic bombs during this war and that her only defense might lie in a counterattack by the same means. Today, with the defeat of Germany, this danger is averted and we feel impelled to say what follows:
The war has to be brought speedily to a successful conclusion and attacks by atomic bombs may very well be an effective method of warfare. We feel, however, that such attacks on Japan could not be justified, at least not unless the terms which will be imposed after the war on Japan were made public in detail and Japan were given an opportunity to surrender.
If such public announcement gave assurance to the Japanese that they could look forward to a life devoted to peaceful pursuits in their homeland and if Japan still refused to surrender our nation might then, in certain circumstances, find itself forced to resort to the use of atomic bombs. Such a step, however, ought not to be made at any time without seriously considering the moral responsibilities which are involved…
Leo Szilard and 69 co-signers
Work on the project now proceeded rapidly and a prototype weapon was successfully tested at Alamogordo, in the deserts of New Mexico, on 16 July 1945. Although the United States now had the atomic bomb, the war against Germany was already at an end, and the conflict with Japan was nearing its close. On 17 July 1945 Leo Szilard and 69 co-signatories from the Manhattan Project in Chicago petitioned the President of the United States with their avowed opposition to any use of such a weapon against civilians in war. One of them was a good friend of mine, George Svihla. He said to his dying day that the use of the bomb against Japan was indefensible: the United States could have announced the success of the atom bomb tests, and warned the Japanese that the weapon would assuredly be used if they did not capitulate; but to use it on cities crammed with civilians in the dying days of conflict seemed inhuman and morally wrong. The signatories also foresaw an era when atomic weapons would be used indiscriminately by all sides, with devastating effects. In that sense the petition was wrong — the ever-present threat of annihilation acted as a deterrent against the use of nuclear weapons from that day on, and no nuclear bomb has since been used in warfare.
World leaders always seem to want to find a war in which they can prove their might, and the newly elected President Truman was convinced that America could make the ultimate grand gesture by using her new bomb, and hasten the end of the war into the bargain. He considered the appeals, but decided to disregard them. On 6 August 1945 a B-29 Superfortress bomber named Enola Gay delivered its uranium bomb (code named Little Boy) to Hiroshima. It was 9ft 9in (3m) long and 2ft 4in (71cm) in diameter and weighed 8,900lb (4,000kg). Its design was unbelievably simple: two sub-critical masses of U-235 at each end of the bomb were forced together in an instant by conventional explosive, and exploded straightaway. Of the 131lb (59kg) of the uranium in the bomb, less than a kilogram underwent nuclear fission. The force of the explosion was roughly equivalent to 15,000 tons of TNT and it is believed to have killed 140,000 people outright. Yet the amount of uranium that was directly converted into energy is unbelievably small. It amounted to just 600 milligrams — 1/50 oz.
On 9 August a second atomic bomb was dropped. This was a plutonium weapon code named Fat Man and was detonated over Nagasaki. This bomb was 10ft 8in (3.3m) long and 5ft (1.5m) in diameter, weighing 10,200lb (4,600kg). Its explosive was a different man-made isotope, plutonium-239. In this alternative design, a single sphere of plutonium weighing 14lb (6.35kg) was installed in the weapon, and 64 detonators fitted around it fired simultaneously. These compressed the sphere so that it imploded on itself and, with the atoms now more tightly packed, it went critical and detonated. The energy released was equivalent to 21,000 tons of TNT, yet it came from the conversion into energy of less than 1 gram of the plutonium (1/30oz). It killed about 40,000 people in an instant, and the following day Japan capitulated.