RADIOACTIVITY AND RADIOACTIVE EXPOSURES - раздел Иностранные языки, THE PRE_ATOMIC AGE
Radioactivity And The Associated Radiation Exposures Are Some...
Radioactivity and the associated radiation exposures are sometimes thought of as environmental problems that have been created by modern science and technology. However, substantial amounts of radioactivity exist in nature and have existed on Earth since its original formation. All biological species evolved on Earth, for better or worse, in this radioactive environment. Radioactivity could be plausibly termed the oldest “pollutant” if one chooses to describe an integral part of the natural world as a pollutant.
With the advent of controlled nuclear fission, we have obtained the ability to create concentrations of radioactivity that far exceed those encountered in the natural environment. An effort is made to minimize human exposure by isolating this material or surrounding it with shielding, but some exposure nonetheless occurs. To gain perspective on the seriousness of the potential resulting problems, we consider in this chapter the sources and amounts of artificial and natural radioactivity. Natural radioactivity here provides a reference or benchmark by which to gauge the significance of the man-made radioactivity.
Human awareness of the existence of ionizing radiation dates only to the period around 1900. Wilhelm Roentgen discovered X-rays in 1895, and within the next 5 years, Henri Becquerel and Marie and Pierre Curie discovered the previously unsuspected ionizing radiations from uranium ore. These were the newly named alpha particles, beta particles, and gamma rays from the radioactive decay of uranium and its associated products. The nature of these radiations and of radioactivity was quickly elucidated by investigators in France, Great Britain, and elsewhere.
The particles from radioactivity and cosmic rays constitute natural ionizing radiation. “Man-made” ionizing radiation comes from X-ray machines, nuclear accelerators, and nuclear reactors, as well as from artificial radionuclides produced by accelerators and reactors. The significant safety and environmental issues that arise in the consideration of nuclear power are related to the radionuclides produced in nuclear reactors. The benefits of X-rays for medical diagnostic purposes were recognized almost immediately after their discovery and the purported benefits of radium, extracted from uranium ore, were proclaimed soon after. The belief that radium had curative properties continued into the 1920s, with horrors such as the sale of “medicines” laced with radium. Surprisingly, underground sites that feature enhanced exposure to radon persist in the United States and elsewhere to this day. At the same time, radium—and later other radionuclides—have been used for better justified purposes, including many applications in medicine and industry.
Along with a growing use of X-rays and natural radioactive materials, there arose a recognition of the health risks of excessive exposure to ionizing radiation. These were recognized following exposures of radiologists, X-ray technicians, and, in a particular tragedy, radium watch dial painters. The dangers were first widely recognized in the 1920s and serious attempts to establish safety standards date from the late 1920s, starting with occupational hazards. Since the 1950s, the setting of standards has been expanded to apply to the general population, usually with criteria that are substantially stricter than those for occupational exposures.
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RADIOACTIVITY AND RADIOACTIVE EXPOSURES
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Pre-reading tasks
1. The text you are to read is headlined “The Pre-atomic Age”. In your opinion, what can it run about?
2. Think of and write down 4-5 questions the answers to which you expect
THE PRE-ATOMIC AGE
Ancient Greek philosophers were the first known scientists to suggest that matter was made up of small, unseen elements, a theory described as “atomism” by Democritus of Abdera in the 5th century В
Comprehension check
1. Choose the best ending a, b, or c to complete the sentences.
1. Ancient Greek philosophers
a) were the first to suppose that matter was composed of small
Vocabulary work
1. The words given in A are used in the text above. Find their synonyms in B.
A
B
to suggest
Pre-reading tasks
1. Have you ever heard about John Dalton, Heinrich Geissler, William Crookes?
2. Can you recollect what they are famous for? What contributions to science did they make?
Comprehension check
1. Consult the text above and complete the following sentences.
1. Atomism reentered scientific ... in the 19th century.
2. Dalto
Pre-reading tasks
1. Do you know:
a) the names of Henri Becquerel and Pierre and Marie Curie? What are they famous?
b) when the Curies and Becquerel worked?
c) what
HENRI BECQUEREL AND THE CURIES’ DISCOVERIES
X-rays were only the first, surprise of the 1890s. New rays were soon detected which proved to be even more profoundly alien to known science.
The French p
Comprehension check
1. Match the discoveries and inventions with the names of scientists.
Marie Curie
found out that uranium salt emitted pen
Vocabulary work
1. There are some words given in bold type in the text. Choose their synonyms in the box below.
to emit
to discover
Pre-reading tasks
1. The text you are going to read is headlined “Further advances in the field of radioactivity”. In your opinion,
- what does it run about?
- what
FURTHER ADVANCES IN THE FIELD OF RADIOACTIVITY
Their work, which led to the Nobel Prize for both (and two prizes for Marie, a rare honor), confirmed the cathode-ray research of British scientist J. J.Thomson, who had experimente
Pre-reading tasks
1. If you were asked to make a report on the theme “From nuclear reactions to nuclear fission” which events would you include in it and what scientists would you mention? Comment
FROM NUCLEAR REACTIONS TO NUCLEAR FISSION
In 1913, Neils Bohr, a brilliant Danish physicist and a post-doctoral student of Rutherford’s, elaborated and modified Rutherford’s model by incorporating quantum mechanical (the study of mechanica
Comprehension check
1. Some dates, namely years are mentioned in the text. Match them with the events described.
J. Chadwick discovered the
Vocabulary work
1. The words given in two columns of the box are mentioned in the text and they have similar meanings. Find and name these pairs.
A
Pre-reading tasks
1. The paragraphs of the text given below are jumbled. Arrange them in the logical order. Comment on your choice of paragraphs succession.
2. You are sure to know the name of a f
SPECULATIONS BEFORE THE DISCOVERY OF FUSION
Atomic energy, now usually called nuclear energy, became a gleam in the eye of scientists in the early part of the 20th century. The possibility that the atom held a vast
Pre-reading tasks
1. Otto Hahn, Lise Meitner, Fritz Strassman made several key breakthroughs revealing secrets of nuclear fission. Can you give any information about these scientists? If nothing is known to you,
REVEALING SECRETS OF NUCLEAR FISSION
Enrico Fermi and his colleagues missed a reaction in the uranium which would later be determined to be the first example of nuclear fission. The task, therefore, fell tо scientist Otto Hahn, who wa
Comprehension check
1. Match the names of scientists with the information about them. (Sometimes information refers to more than one scientist).
Otto Hahn
co
Vocabulary work
1. Find synonyms or antonyms among the words given in italics in the text and name them. Be careful as the verbs are used in different forms
2. Fill in the tab
Follow-up activities
1. In pairs, discuss the information given in the text.
2. Make up a short report based on the text. (Presenting only key ideas).
3. Find some add
FISSION AND THE FIRST REACTORS
Fission of uranium was discovered—or, more precisely, recognized for what it was—in 1938. Scientists quickly recognized that large amounts of energy are released in fission and that
Pre-reading tasks
1.In the text below the names of Henri Becquerel, Pierre and Marie Curie, Ernest Rutherford are mentioned. Recollect what each of them is famous for. The table below will help you to fulfill the
RADIOACTIVE MATERIALS AS SOURCES OF NUCLEAR ENERGY
Radioactive … involves the spontaneous disintegration of an atomic nucleus. As the nucleus …, various particles as well as high-energy electromagnetic waves are … . Ra
Pre-reading tasks
1. The text you are to read is headlined “Boiling water reactors”. In your opinion, what problems are discussed in this text?
2. If you were to make a report on this theme wha
BOILING WATER REACTORS
Consider the simplified schematic of one of the most common types of nuclear reactor, a boiling water reactor. (See the accompanying illustration.) Boiling water reactors were firs
GLOBAL WARMING AND NUCLEAR POWER
The idea behind global warming is simple enough. Earth’s atmosphere retains some of the heat that Earth receives from the Sun. The amount of heat retained depends upon the chemical composition of t
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