Материал: Аврамова NUCLEAR ENGLISH 2013

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The fact that one free neutron can lead to the release of two or three makes it possible to extract energy in useful quantities from this process, because the neutrons released may trigger а chain reaction - they may collide with other nuclei that in turn split to produce more neutrons, and so on. In а nuclear reactor, the reaction is controlled so that, on average, one neutron from each fission event leads to the release of another. If you allow on average more than one neutron from each event to cause further fission, the neutron flux increases and the power output goes up.

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So what stops the chain reaction from running out of control? In the reactor core, the rods of natural or enriched uranium are interspersed with control rods, which regulate the rate of fission by absorbing the neutrons. These rods can be raised or lowered to keep the release of energy steady. They are made of neutron-absorbing material, typically boron or cadmium, so when lowered into the core they absorb excess neutrons and slow down the reaction. Raising them speeds it up. Reactors have а fail-safe design: the rods automatically drop into place in an emergency, shutting down the reactor as quickly as possible. The accident at Chernobyl in Ukraine in April 1986 happened during а test in which operators deliberately ignored and disabled safety mechanisms and withdrew most of the control rods. The core overheated and а fire broke out, releasing large amounts of radioactive material. More than 9,000 extra deaths from cancer have since been recorded in the local population.

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Circulating around the core is а coolant that carries away the heat. Gas-cooled reactors use СО2, as а coolant. Pressurized reactors use water. After the coolant has been heated in the core of the reactor, it is pumped through а heat exchanger where it transfers its energy to water, creating high-pressure steam. The steam is used to turn turbines which drive а generator. This part of а nuclear power station is like any other thermal electricity-generating station.

Do you know how the barn got its name? Read the passage and

find out.

A barn is a unit of cross-section equal to 10-24 cm2. It is more or less equivalent to the cross-sectional area of a nucleus, but refers to the

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probability of a particular interaction, not a physical area. The origin of the term «barn» is curious. Here is a popular myth about it.

Once in December of 1942, a group of nuclear physicists were having dinner in the café of Purdue University. With cigarettes and coffee, the conversation turned to the topic of cross sections.

In the course of the conversation it was mentioned that there was no name for the unit of cross section of 10-24 cm2. The tradition of naming a unit after some great man closely associated with the field ran into difficulties, since no such persons could be brought to mind.

Failing in this, the names of Oppenheimer and Bethe were tried, since these men had suggested and made possible the work on the problem with which the Purdue project was concerned. The “Oppenheimer” was rejected because of its length, although in shortened form an

“Oppy” or “Oppie” would seem to be short enough. The “Bethe” was thought to be confusing because of the wide-spread use of the Greek letter. Since John Barkley was directing the work at Purdue, his name was tried, but the “Barkley” was thought to be too long. The “John” was considered, but it was rejected because of the wide use of the term for purposes other than as the name of a person. Then one of the authors led to the bridging between “Barkley” and “John”. This immediately seemed good and further it was pointed out that a cross section of 10-24 cm2 for nuclear processes was really "as big as a barn” (i.e. an easy target for nuclear bombardment)

The term “barn” is spelled just that way, and no capital letter “B” is needed, and that the plural form is “barns” with no letter “e” involved.

The meanings of “millibarn” and “kilobarn” are obvious.

Unit 6

Reading 6-A

Pros and Cons of Nuclear Power Plants

Power corrupts, but we need electricity.

Nuclear power has a number of advantages, as well as a number of depressing negatives. As far as positives go, nuclear power's biggest advantage is related to the simple fact that it does not depend on fossil fuels. Coal and natural gas power plants emit carbon dioxide into the atmosphere, contributing to climate change. With nuclear power plants,

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CO2 emissions are minimal. Besides, a properly functioning nuclear power plant actually releases less radioactivity into the atmosphere than a coal-fired power plant. Finally, the cost of nuclear power is not affected by fluctuations in oil and gas prices.

As for negatives, nuclear fuel may not produce CO2, but it does cause problems. Historically, mining and purifying uranium has not been a very clean process. Even transporting nuclear fuel to and from plants poses a contamination risk. And once the fuel is spent, you cannot just throw it in the city dump. It is still radioactive and potentially deadly.

On average, a nuclear power plant annually generates 20 metric tons of spent nuclear fuel, classified as high-level radioactive waste. When you take into account every nuclear plant on Earth, the combined total amount is roughly 2,000 metric tons yearly. All of this waste emits radiation and heat, meaning that it will eventually corrode any container and can prove lethal to nearby life forms. Eventually, spent nuclear fuel will decay to safe radioactive levels, but it takes tens of thousands of years. Currently, most spent nuclear fuel is stored at reactor sites in specially designed storage pools. In the future, much of this waste may be mixed with glass and transported deep underground. In the meantime, however, this waste has to be stored, monitored and guarded to prevent the materials from falling into the wrong hands. All of these services cost money -- on top of the high costs required to build a plant.

Nuclear waste can pose a problem, and it is the result of properly functioning nuclear power plants. When something goes wrong, the situation can turn catastrophic. The Chernobyl disaster is a good example. In 1986, the Ukrainian nuclear reactor exploded, releasing 50 tons of radioactive material into the surrounding area, contaminating millions of acres of forest. The disaster forced the evacuation of at least 30,000 people, and eventually caused a number of deaths from cancer and other illnesses.

Chernobyl is still a black eye for the nuclear power industry, often overshadowing some of the environmental advantages the technology has to offer.

Exercise 1. Match the following Russian and English equivalents.

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Exercise 2. Below you will see a list of words related to Reading 6-A. Translate the words and write ten sentences using the words below.

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Exercise 3. Put each of the following words in its correct place in the passage below.

Nuclear, burn, chain, dangerous, energy, reactor, robot, rods, shielding, turbines, uranium, waste, water.

1.Is nuclear power renewable? [yes/no]

2.Nuclear power stations use _______ as fuel. They need very little

fuel, compared to a «fossil» power station because there is much more

______ in nuclear fuel.

3.The ______ reaction inside the ______ creates heat, which turns

______ into steam to drive ______, which drive generators to make electricity.

4.The fuel _____ are safe to handle before they go into the reactor, it is only when they come out that you need to handle them with ______

arms and heavy ______.

5.______ power stations do not create atmospheric pollution, because they do not _____ anything. However, the small amount of _____

that they do produce is very _______.

Exercise 4. Use Reading 6-A to answer the questions below.

1.What is the biggest advantage of nuclear power?

2.What fuels contribute to climate change?

3.Why are nuclear power plants more environmentally friendly than gasand coal-fired plants?

4.What economic advantage does nuclear power offer?

5.What risk do nuclear power plants pose?

6.What processes in the nuclear industry cause environmental contamination?

7.What is the most important source of contamination? Why?

8.How long does it take for spent nuclear fuel to decay to safe levels?

9.How is spent fuel stored currently?

10.What will happen to nuclear waste in the future?

11.What is the biggest risk posed by nuclear power?

12.What happened at Chernobyl in 1986?

13.What were the consequences of the disaster?

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