实用英语U2TextB.ppt
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1、Pre-Reading Task While-Reading Task After-Reading Task,Unit 2: Text B,Pre-reading Task,Text-related Information Pre-reading Activity,Nuclear Power,Text-related Information,Text-related Information,Nuclear Power:,The energy consumed or produced in modifying the composition of the atomic nucleus and p
2、owering electricity-generating plants in countries throughout the world. It is seen by many as the source of inexpensive, clean power; but because of the hazardous radiation emitted in producing that power and the radioactivity of the materials used, others feel that it may not be a viable energy al
3、ternative to the use of fossil fuels or solar energy.,Text-related Information,At present, only the fission process is used in the commercial production of energy, usually to make electricity, but also occasionally to produce steam for district heating or industrial applications. Public opinion rema
4、ins largely favourable toward nuclear energy. However, questions about the safety and economy of nuclear power have created perhaps the most emotional battle yet fought over energy. Nuclear opponents emphasize a number of unanswered questions about the environment, such as the effects of low-level r
5、adiation over long periods, the likelihood of major accidents at a nuclear power plant, and nuclear powers waste products.,1. What are the advantages and disadvantages of nuclear power? 2. From the title of the passage, guess whether the author is for or against theuse of nuclear power. Now read the
6、 passage and see if you agree with what the author says.,Pre-reading Task,Exercise 1 Before reading the passage, think over the questions.,Text B Detailed Study of the Text,While-Reading Task,Text B Nuclear Power: Advantages That Outweigh the Risks 1 The views expressed in the debate on the safety o
7、f nuclear power have come mainly from the interested parties the United Kingdom Atomic Energy Authority and British Nuclear Fuels Limited on the one hand, and the various environmental groups on the other. It is not surprising therefore that the public is confused by the many contradictory statement
8、s, some of which have been sensational.,While-Reading Task,Furthermore, most of the responsible contributions to the debate have been written in such highly technical terms as to be incomprehensible to the lay reader. We believe there is a need for an impartial and dispassionate analysis of the issu
9、es involved in language the public can understand. 2 While every effort should be made to develop the more promising natural sources as quickly as possible, we believe it will be virtually impossible for any of them to make a significant contribution to the energy gap before the beginning of the nex
10、t century.,While-Reading Task,3 If the world is not to face a substantial fall in living standards with a very real risk of civil upheaval if not war there is no alternative but to rely on a major contribution of energy from nuclear sources. However, as it is, there are genuine anxieties which must
11、be answered objectively. These fall under the following broad headings: (I) The long-term effects of the low level radiation to which workers in the plants and the public may be exposed; (II) the possibility of a “run away” leading to an atomic explosion; (III) the disposal of radioactive waste.,Whi
12、le-Reading Task,4 We will deal with these in turn. 5 1 Acceptable limits of radiation: The long-term effect of low doses of radiation is a particularly difficult subject since medical experts disagree on the interpretation of such statistical evidence as is available. However, two facts emerge which
13、 seem to us significant: (a) there is no evidence that the incidence of cancer or other diseases among the work-force of the United Kingdom nuclear plants is higher than the national average. (b) the average exposure of the public to radiation as a result of nuclear power is only a minute fraction (
14、0.2 per cent) of the radiation from other sources mainly natural.,While-Reading Task,6 2 The worst conceivable accident: It must be accepted that no process or mechanism can be 100 per cent safe. However, under no circumstances could a thermal power reactor of any type explode like an atomic bomb. T
15、he worst that could happen in the improbable event of a whole series of unlikely incidents happening together, would be an escape of radioactivity to the surrounding atmosphere. 7 It has been calculated by Professor Rasmussen, of the Massachusetts Institute of Technology, that the chances of such an
16、 accident causing 100 deaths for a group of 100 power plants would be one incident in 100 000 years.,While-Reading Task,While-Reading Task,8 3 The disposal of radioactive waste. The spent fuel elements from any reactor are highly radioactive and contain fission and other products with half lives ran
17、ging from a few seconds to many thousands of years. 9 It should be realized, however, that the radiation (of whatever sort) emitted by a particular element is caused by the process of its radioactive decay. The elements with a high rate of decay (short half lives) therefore emit very intense radiati
18、on, while those with low rates of decay (long half lives) emit only low levels.,10 After chemical separation, some of the elements (uranium and plutonium) are recycled for further use; the remainder have to be stored or disposed of in some way. The highly active concentrated wastes in liquid form ar
19、e at present stored in stainless steel double-walled tanks for additional safety. There would be obvious advantages from the point of view of long-term storage if the concentrates could be converted to a solid, and a process has been worked out for turning them into an insoluble glass.,While-Reading
20、 Task,11 There are areas in the earths crust where the natural levels of radioactivity are already high, and as in so many other instances, the additional radiation due to mans efforts would be insignificant compared with natural sources.,While-Reading Task, Nuclear Power: More Advantages Than Risks
21、,Nuclear Power: Advantages That Outweigh the Risks, The different opinions which come from a discussion on the safety of nuclear power .,The views expressed in the debate on the safety of nuclear power have come mainly from the interested parties . and the various environmental groups on the other.,
22、e.g. The topic aroused an interesting debate. Truth develops through debate between different views.,debate: n. a public meeting in which a question is talked over by at least 2 people or groups, each expressing a different point of view; argument or discussion in general,e.g. There is urgent need t
23、o debate this issue openly. The subject was hotly debated.,cf. debate : v. to argue about (something) in an effort to persuade other people,the groups that are directly concerned with the issue and are likely to be affected by its results,the interested parties:,groups who are concerned with the pro
24、tection of the environment from pollution, etc.,the environmental groups:, So it is not surprising that the public doesnt know who is right because many views in the debate are contradictory and some of them have been shocking.,It is not surprising therefore that the public is confused by the many c
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