Follow-up

Text 3

Text 2

Text 1

Reading

Pre-reading

The texts for reading are extracts from magazine articles. Here are the headlines of the articles. Scan the texts and match the headlines with the correct text and explain your choice.

a Nuclear Power in the Future

b What Happened at Chernobyl

c A Guide to Radiation

Read the text given by the teacher and share the information with your group mates. Make use of the following phrases: in my personal opinion; to my mind; it would be more reasonable to…; on the one hand,… on the other hand; I could be wrong but I think; personally I feel that; my concern is…; this is what I think.

At 1.23 a.m. local time on 26 of April 1986 a series of explosions shook the number 4 reactor at the Chernobyl nuclear power station in the Ukraine. The energy of these explosions was minuscule compared with a nuclear bomb, but something had occurred which many scientists and engineers believed was never likely to happen – the top of the reactor had been torn open, exposing a burning core which sprayed radioactive debris into the air. It took heroic efforts over the next ten days to control this release, during which time several thousand tones of boron, lead, dolomite and sand were dropped from helicopters to prevent any further nuclear reactions and effectively seal the core before its final covering in concrete.

Some of the first casualties were firemen, many of whom suffered severe radiation burns fighting secondary fires caused by hot fuel fragments falling on flammable roof materials on other reactor buildings. Soviet scientists, reporting in 1986 at the International Atomic Energy Agency, indicated that 31 people had died and 135 000 people had evacuated from within a 30 km radius.

Immediate deaths and injuries were not the only effects of the accident, however. Enormous sums of money have been spent since on decontamination and protection of water supplies. Some future cancers will be due to Chernobyl although they will not be detectable amongst the cancers caused by other factors. The radioactivity also penetrated far beyond the USSR across Europe, giving rise to further problems. Areas where heavy rainfall caused concentrated patches of ground contamination were particularly badly affected. In Britain this occurred over North Wales, the Lake District and Scotland, and has resulted in sales of sheep being restricted from some of these sales areas over a long period of time.

Chernobyl was therefore a very major accident, releasing a substantial proportion of the radioactivity in the core to the environment. It resulted from violations of safety regulations and design flaws in this type of reactor, and emphasized the need for great care in the design, construction and operation of nuclear reactors. (The automatic mechanisms which shut down reactors safely if any irregularity or failure occurs are obviously vital). It has also focused attention worldwide on many questions concerning nuclear power and its safety.

If used with proper care and with wastes properly disposed of, nuclear power is potentially the least polluting major energy source. Unlike the burning of coal, it does not have the side effects of acid rain and possible changes in the climate. However the Chernobyl disaster has reminded us of the importance of high safety standards which must be used to reduce the potential danger to insignificant levels. The future success of nuclear power depends on the public being convinced that safety and radiation protection standards [in Britain] are very high and that nuclear power offers a real benefit.

Much will also depend on the development and cost of other energy sources, such as coal. If the costs of other energy sources, and the cost or uranium, rise substantially, then fast-breeder reactors should become economic and help us to make much better use of uranium reserves. At present it seems unlikely that they will be widely used before the early decades of the next century.

If fast-breeder reactors are not accepted by the public, there will be a greater need to develop fusion power. Fusion is the energy source that powers the sun. In contrast to fission, fusion involves bringing tow atoms together (or fusing them). One way of doing this is to confine a high temperature gas of electrically charged atoms (a ‘plasma’) with the aid of strong magnetic fields. Unfortunately, nuclei repel each other strongly until they are very close together, and so very high temperatures and strong magnetic fields are needed. When two light atoms (for example two hydrogen atoms), the resulting mass is less than that of the two separate particles and so energy is released.

In the immediate future, radioactivity will undoubtedly continue to be an emotive subject, as will nuclear safety and waste disposal. It is only understanding the benefits and the risks, and through confidence in the safe operation of the nuclear industry, that the trust of the public can be gained.

Radioactivity was discovered in 1896 by Antoine Henry Becquerel, who noticed that uranium salts had a pronounced effect on photographic plates even through thin sheets of metal. It arises from the spontaneous disintegration of the nucleus of a radioactive element (radio nuclide) such as uranium – 238. There are four principal types of radiation – alpha and beta rays (which are actually emissions of subatomic particles) and gamma- and x-rays (which are forms of electromagnetic radiation). Radioactivity is usually measured in terms of curies (Ci), named after physicist Marie Curie; 1 Ci=3.71010 disintegrations per second, which is the number of disintegrations undergone by one gram of the element radium in 1 second.

Humans can absorb radiation either externally (through the skin) or internally (by consuming the food). Absorption is measured in terms of grays (Gy), where 1 Gy=1 joule of energy per kilogram of body tissue. A given number of grays can have different effects on health, however, depending on the type of radiation a person is exposed to and the particular tissues affected. For this reason, radiation doses are usually measured in terms of sieverts (Sv), or the number of grays times an appropriate quality factor. Humans naturally receive small doses of radiation (on the order of 1 to 5 millisieverts (mSv) per year). Larger doses are invariably associated with the mishandling of radioactive materials.

From the standpoint of human health, the most worrisome radio nuclides are strontium-90 and cesium-137, both of which have half-lives of approximately 30 years. Strontium-90 accumulates in bones, while cesium-137 passes through the metabolic system. Given the number and complexity of the health problems that exposure to radiation can cause it is difficult to determine exact thresholds for either death or disease. Current standards call for limiting the uniform irradiation of the whole body to 5 mSv per year and the exposure of particular organs and other tissues to 50 mSv per year.

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