Academic literature on the topic 'Radioactivity. Radiation. Thorium'

In 1896, Henri Becquerel (1852–1908) had discovered, by chance, the phenomenon of radioactivity, after he found that uranium salts left on top of covered photographic plates produced an image on the plates when they were later developed. Soon afterwards, thorium was also found to be radioactive. In 1898 Marie Curie (née Sklodovska) realized that certain minerals were more ‘radioactive’ (a term she first introduced) than could be rationalized by the amount of uranium or thorium that they contained. She guessed that they might contain trace amounts of an even more radioactive element, and during the long purification process, she eventually realized that two such elements were present. The naming of the first of these, discovered in July 1898, is described by her daughter Eve Curie in her biography of her mother: . . . ‘You will have to name it,’ Pierre said to his young wife, in the same tone as if it were a question of choosing a name for little Irène [their first daughter]. The one-time Mlle Sklodovska reflected in silence for a moment. Then, her heart turning toward her own country which had been erased from the map of the world, she wondered vaguely if the scientific event would be published in Russia, Germany and Austria—the oppressor countries—and answered timidly: ‘Could we call it “polonium”?’ . . . Marie Curie named the element after her homeland, Poland, but the country did not exist as a separate entity at that time, and her choice was something of a political statement. The second element discovered by Marie and Pierre Curie was found to be millions of times more radioactive than uranium. This element they called ‘radium’ because of its intense radioactivity. Over three and a half years later, when they finally isolated a tenth of a gram of purified radium salts from tonnes of pitchblende ore, the Curies were delighted to find that the substance was spontaneously luminous. After the discovery that uranium and thorium were radioactive, in September 1899, Ernest Rutherford (1871–1937) made a further discovery: ‘In addition to this ordinary radiation, I have found that thorium compounds continuously emit radio-active particles of some kind, which retain their radio-active powers for several minutes.

Chapter 2 grounds the study in an exploration of the ecological, material, and social contours of the region. It focuses on the backstories of Kudankulam as the site for a nuclear plant and the spaces of criticality that were generated. The formidable presence of the nuclear plant, visual, material and discursive spawned a range of reactions that spanned from intrigue to ambivalence to resistance. With an overview of ‘hot spots’ in Kanyakumari and Tirunelveli Districts, the prospect of more radioactivity applies not just to the Kudankulam Nuclear Power Plant but also to high levels of background radiation in peninsular India, and the mining of sand for atomic minerals particularly for alternative sources of nuclear fuel by way of thorium. Along the way, we assess the repercussions of new hierarchies with the migrant middle class of nuclear employees and the entrenchment of old ones along caste-communal lines.

One of the first pictures made with X-rays by Wilhelm Roentgen, when he discovered them in 1895, was of the hand of a colleague of his, a Dr. von Koelliker. The bones of his hand and a ring he was wearing stand out clearly; the flesh appears as a faint halo around the bones. A glance at the photograph makes it obvious why the medical possibilities of X-rays were almost immediately recognized. X-rays were used first for diagnosis, and later for treatment of disease as well, but they were the first form of radiation shown also to cause disease. In the early years of radiology, radiologists used to hold the X-ray film in place close to the patient’s body, thus receiving intense exposures of their hands. There were unexpected difficulties in arranging for a celebratory dinner for the Society of Radiologists in Philadelphia on the twenty-fifth anniversary of the discovery of X-rays: so many of the members had lost fingers or hands that they found it too awkward to eat in public. The discovery of X-rays led in 1896 to the discovery of radioactivity by Henri Becquerel, who observed, almost by accident, that compounds of the metallic element uranium emitted a kind of radiation that like X-rays passed through the black paper photographic film was wrapped in and darkened the film. Marie and Pierre Curie, following up his work, found that the strongest sources of the radioactivity were impurities in the uranium compounds and were able to extract small quantities of other much more radioactive elements from them, including polonium and radium. Becquerel and the Curies were awarded the Nobel Prize in physics in 1903. At first, the energy given out steadily by radioactive substances could not be explained, and some scientists proposed that they might provide unlimited sources of energy. It was soon shown that radioactive substances, like any other fuel, are used up as energy is given out: the radioactive atoms are undergoing disintegration into other, different kinds of atoms. When an atom of uranium-238 emits alpha radiation, it changes at the same time into an atom of a rare element called thorium, also radioactive.

The plutonium in the Northern Rio Grande is entirely artificial. Small amounts of plutonium may have formed in exceptionally rich uranium deposits in south-central Africa, but for practical purposes, until its manufacture in 1939, the element did not occur in the earth’s environment. Although the detailed story of the origins of plutonium are beyond the scope of this book, a summary of that history does clarify the issues regarding plutonium in the Northern Rio Grande in the late twentieth century. The purposes of this chapter are to review the origins of plutonium and to examine briefly the nature of that element. Modern nuclear physics, which ultimately led to the production of plutonium, began with the publication of the discovery of X-rays by Wilhelm Conrad Röntgen in 1896. His work showed that the physical world was much more complicated than previously thought and that energy could be emitted from substances. In the same year, Henri Becquerel of Paris showed that uranium emitted radiation, and soon thereafter Marie and Pierre Curie coined the term radioactivity to describe the emissions they recorded from two newly discovered elements, radium (named after its radiative properties) and polonium (named after Marie Curie’s home country of Poland). Between 1898 and 1902, Ernest Rutherford of Cambridge University and, later, McGill University explored processes of radioactive decay that generated free electrons (beta radiation) and bursts of energy (gamma radiation) and discovered that some elements changed their basic properties during the emission. Rutherford termed these changes transmutation and laid the philosophical foundations for understanding atomic structure. The transmutation of elements was a significant addition to the rapidly expanding knowledge about the number and types of elements in the natural world. Between 1894 and 1900, William Ramsey enlarged the periodic table with an entire family of inert gases, and by 1903 more than a dozen radioactive elements were known. By 1903, it was obvious that the decay process explained many observed elemental changes: Americans Bertram B. Boltwood and Herbert N. McCoy showed that radium descended from uranium, and Otto Hahn connected several types of thorium.