Canada’s Nuclear History

Wilhelm Röntgen
Wilhelm Conrad Röntgen.

Even though radioactivity has existed in the universe since the dawn of time, it remained essentially undiscovered until the late nineteenth century when scientists of the day were developing equipment that happened to accidentally allow for its detection.  In 1895, in Bavaria, Wilhelm Conrad Röntgen discovered what would later be known as x-rays when he noticed that something invisible must have been transmitted through the space around the gas discharge tubes in his lab causing nearby crystals to glow.  A year later in France, Henri Becquerel serendipitously discovered that something similar was happening that allowed uranium ore to produce an image on photographic plates.  In the following years, Becquerel, fellow French Scientists Pierre and Marie Curie, British scientist J.J. Thomson, and Ernest Rutherford from New Zealand determined that these occurrences were due to unseen alpha particles, beta particles, and gamma rays being emitted from certain materials. The name radioactivity was given to the mysterious phenomenon.

Albert_Einstein
Albert Einstein.

In 1905 the German physicist Albert Einstein develops the theory that mass has energy, and making the assumption that we could produce energy by converting the material. This relationship is expressed by the equation E = mc2. Over the next 35 years, many researchers from various parts of Europe performing work that will ultimately confirm the hypothesis put forward by Einstein. In 1932, British researcher James Chadwick discovered the neutron.  That same year John Douglas Cockcroft of England and Ernest Thomas Sinton Walton from Ireland produced nuclear transformations by bombarding atoms with accelerated protons.  In 1934, French chemists Irene Curie and her husband Jean Frédéric Joliot found that such transformations created artificial radionuclides. That same year Italian physicist Enrico Fermi found that a much greater variety of artificial radionuclides could be formed when neutrons were used instead of protons.

Fermi continued his experiments, mostly producing heavier elements from his targets, but surprisingly, with uranium, some much lighter ones as well. In 1939, German physicists Otto Hahn and Fritz Strassmann showed that the new lighter elements were barium and others which were each about half the mass of uranium, thereby demonstrating that atomic fission or splitting had occurred. Austrian physicists Lise Meitner and Otto Robert Frisch, working under Danish physicist Niels Bohr, hypothesized that this occurred because the neutron was captured by the uranium nucleus, causing severe vibrations leading to the nucleus splitting into two not quite equal parts. They calculated the energy release from this fission to be of the order of 200 million electron volts, based on the difference in mass before and after the fission. Otto Frisch later confirmed this experimentally. This loss in mass was explained by a hypothesis proposed by Einstein. In 1905, German physicist Albert Einstein developed the theory that mass and energy were equivalent, hypothesizing that energy could be produced through the transformation of matter. His equation, E=mc2, is probably the best known equation in science. Over the next 35 years many dedicated scientists in various regions throughout Europe worked on research that was eventually able to verify Einstein’s hypothesis. Einstein’s theory of mass energy was correct – and in a huge way!

Over the next five years, brought on primarily by involvement in the Second World War, research continued into the ability to release large amounts of energy from the fissioning of uranium.  Many of the European scientists mentioned above fled their home countries and Adolf Hitler’s Nazi regime.  Several were welcomed by the governments of England and the United States to set up labs and continue their important research in safety. While some of the work was focused on utilizing this new nuclear energy for powering naval vessels, another line of top secret research known as the Manhattan Project, was being undertaken to determine how a nuclear chain reaction might be used for destructive purposes in the form of a weapon. This research eventually led to the development of extremely powerful bombs which, in August of 1945, were dropped by the American military on the Japanese cities of Hiroshima and Nagasaki and brought about the end of the war.  For most people around the World, news of these attacks was their unfortunate introduction to the emerging science of nuclear energy.