Пособие для теплоэнергетиков 2 семестр



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Boiling Water Reactors (BWRs)

Boiling water reactors (BWRs) use heat released by nuclear fission to directly boil water that produces steam to drive a generator. These reactors are considered light water reactors, because they use ordinary water. Thirty-five of all nuclear reactors in the U.S., or approximately one-third, are boiling water reactors (BWRs).

Boiling water reactors (BWRs) are the second most common type of commercial nuclear reactors in the U.S. The most common is the pressurized water reactor.

The boiling water reactor is the same type of reactor as those severely damaged in Japan, when an earthquake and tsunami struck the Fukushima Daiichi Nuclear Power Plant in March 2011. Overheating and damage inside the reactors triggered ongoing radiation leaks that require evacuation of a 12 mile radius.

How a Boiling Water Reactor Works

In BWRs, the reactor pressure vessel is a large, 7-inch thick forged steel cylinder with domed ends. This vessel is kept inside a sealed containment building to prevent any radiation from escaping into the atmosphere if there is a failure or accident. These building are dome-shaped and are made of steel-reinforced concrete.

Unlike pressurized water reactors, BWRs actually boil the water. The core inside the containment structure of the typical BWR produces heat as 370-800 fuel assemblies sustain the nuclear chain reaction, which also serves as the moderator, circulated with electric pumps.

The water moves upward through the core, absorbing heat and producing a steam-water mixture.

The steam-water mixture is forced out the top of the core into two stages of moisture separation where water droplets are removed before the steam is allowed to enter the steam line.

The steam is piped to the turbine, causing it to turn the plant’s generator, producing electricity which is distributed to the grid.

The unused steam is exhausted into the condenser where it is condensed into water, which is pumped out of the condenser, reheated and pumped back to the reactor vessel.

The hot core at the center of the reactor is kept from overheating by a flow of cooling water circulated by pumps. This cooling function is so vital that reactors have backup generators designed to continue the water flow if the reactor goes out or malfunctions.

Refueling a Boiling Water Reactor

A boiling water reactor can run for 18 months to two years before it requires refueling. Refueling involves replacement of roughly 250 out of 764 (approximately one-third) of the bundled uranium dioxide pellets in a reactor pressure vessel. When the reactor is refueled, the spent fuel from the reactor is moved to onsite spent fuel pools or if the pools are at capacity, it’s stored in dry casks. These casks may also be used to transport spent fuel. Both storage methods are designed to keep radiation shielded and prevent it from escaping into the atmosphere.

Vocabulary

heat — тепло

nuclear fission — деление атомного ядра

pressurized water reactor — ядерный реактор с водой под давлением

damage — повреждение

overheating — перегрев

trigger – вызывать, запускать

radiation leak — утечка радиации

vessel — корпус ядерного реактора

containment building — защитная оболочка (ядерного реактора)

steel-reinforced concrete — армированный сталью бетон

core ядро

fuel — топливо

pump — насос

steam — пар

grid — решетка

backup — запасной

pellet – гранула, брикет

onsite spent fuel pools – местный резервуар для использованного ядерного топлива

dry casks — сухотарные бочки

storage – хранение

Tasks

1.Read the text and translate it.

2. Put the following words into the gaps:

steel-reinforced overheating fuel core triggered grid chain

1.The core inside the containment structure of the typical BWR produces heat as 370-800 fuel assemblies sustain the nuclear (….) reaction

2. The water moves upward through the (…), absorbing heat and producing a steam-water mixture.

3. When the reactor is refueled, the spent (…) from the reactor is moved to onsite spent fuel pools.

4. The hot core at the center of the reactor is kept from (…) by a flow of cooling water circulated by pumps.

5. Overheating and damage inside the reactor (…) ongoing radiation leaks.

6. The steam is piped to the turbine, causing it to turn the plant’s generator, producing electricity which is distributed to the (…).

7. These building are dome-shaped and are made of (…) concrete.

3. Translate from Russian into English:

запустить генератор

землетрясение и цунами

вызывать последующую утечку радиации

цилиндр из кованной стали

двигаться вверх по ядру

паро-водяная смесь

поданный по трубе в турбину

конденсатор

поток охлаждающей жидкости

способы хранения

4. Name the paronymous words to the following:

produce pressurized leak circulated mixture condenser

5. Make up three forms of the following verbs:

Drive, strike, make, keep

6. Find in the text the sentences with the predicate in the Passive Voice. Make the sentences active? If it is possible.

.

e.g. The core is cooled by ordinary water. — Ordinary water cools the core.

7. Answer the questions:

What do boiling water reactors use?

Why are these reactors considered light water reactors?

What types of reactors were damaged in Japan in 2011?

What did overheating and damage inside the reactors in Japan trigger?

What does the reactor pressure vessel of BWRs look like?

How is the core cooled?

8. Complete the sentences and translate them into Russian:

1) Thirty-five of all nuclear reactors in the U.S., or approximately one-third, are….

2) In BWRs, the reactor pressure vessel is a large, 7-inch thick forged steel cylinder…

3) The water moves upward through the core, absorbing heat and…

4) The unused steam is exhausted into the condenser where it is condensed into water, which is pumped out of the condenser, reheated and…

5) Reactors have backup generators designed to continue the water flow if….

6) The spent fuel from the reactor is moved to onsite spent fuel pools or if the pools are at capacity, it’s stored in….

9. Say if the sentence is true or false.

This vessel is kept inside a sealed containment building to prevent any radiation from escaping into the atmosphere/

These building are dome-shaped and are made of forged steel concrete.

BWRs actually boil the water.

The water moves upward through the core, absorbing heat and producing a fog-water mixture.

Water droplets are removed after the steam is allowed to enter the steam line.

The electricity from the generator is distributed to the grid/

The unused steam is exhausted into the onsite pool.

The hot core at the center of the reactor is kept from overheating by a flow of cooling water circulated by pumps.

10. Guess what it is:

— large, thick forged steel cylinder with domed ends

— this thing prevents any radiation from escaping into the atmosphere if there is a failure or accident

— place for storing the spent fuel

— a device for abstracting heat, as in a refrigeration unit

11. Describe the procedure of refueling a Boiling Water Reactor.

12. Describe the work of a boiling water reactor.

Fossil-fuel power station

fossil-fuel power station is a type of power station that burns fossil fuels such as coalnatural gas or petroleum (oil) to produce electricity. Central station fossil-fuel power plants are designed on a large scale for continuous operation. In many countries, such plants provide most of the electrical energy used.

Fossil fuel power stations have rotating machinery to convert the heat energy of combustion into mechanical energy, which then operates an electrical generator. The prime mover may be a steam turbine, a gas turbine or, in small plants, a reciprocating internal combustion engine. All plants use the energy extracted from expanding gas — steam or combustion gases. Byproducts of thermal power plant operation must be considered in their design and operation. Waste heat energy, which remains due to the finite efficiency of the CarnotRankine, or Diesel power cycle, is released directly to the atmosphere, directly to river or lake water, or indirectly to the atmosphere using a cooling tower with river or lake water used as a cooling medium. The flue gas from combustion of the fossil fuels is discharged to the air. This gas contains carbon dioxide, water vapour, as well as substances such as nitrogen oxides (NOx), sulfur oxides (SOx), mercury, traces of other metals, and, for coal-fired plants, fly ash. Solid waste ash from coal-fired boilers must also be removed. Some coal ash can be recycled for building materials. 

Fossil fueled power stations are major emitters of CO2, a greenhouse gas (GHG) which according to a consensus opinion of scientific organisations is a contributor to global warming as it has been observed over the last 100 years. Brown coal emits about 3 times as much CO2 as natural gas, and black coal emits about twice as much CO2 per unit of electric energy. Carbon capture and storage of emissions is not expected to be available on a commercial economically viable basis until government supported legislation is enacted.

In a fossil fuel power plant the chemical energy stored in fossil fuels such as coalfuel oilnatural gas or oil shale and oxygen of the air is converted successively into thermal energymechanical energy and, finally, electrical energy. Each fossil fuel power plant is a complex, custom-designed system. Construction costs, as of 2004, run to US$1,300 per kilowatt, or $650 million for a 500 MWe unit. Multiple generating units may be built at a single site for more efficient use of landnatural resources and labour. Most thermal power stations in the world use fossil fuel, outnumbering nucleargeothermalbiomass, or solar thermal plants.

Heat into mechanical energy

The second law of thermodynamics states that any closed-loop cycle can only convert a fraction of the heat produced during combustion into mechanical work. The rest of the heat, called waste heat, must be released into a cooler environment during the return portion of the cycle. The fraction of heat released into a cooler medium must be equal or larger than the ratio of absolute temperatures of the cooling system (environment) and the heat source (combustion furnace). Raising the furnace temperature improves the efficiency but complicates the design, primarily by the selection of alloys used for construction, making the furnace more expensive. The waste heat cannot be converted into mechanical energy without an even cooler cooling system. However, it may be used in cogeneration plants to heat buildings, produce hot water, or to heat materials on an industrial scale, such as in some oil refineries, plants, and chemical synthesis plants.

The Carnot cycle is the theoretically most efficient closed thermodynamic cycle for conversion of heat energy into useful work, and practical fossil-fuel stations cannot exceed this limit. In principle, fuel cells do not have the same thermodynamic limits as they are not heat engines.

Coal

Coal is the most abundant fossil fuel on the planet. It is a relatively cheap fuel, with some of the largest deposits in regions that are relatively stable politically, such as ChinaIndia and the United States. This contrasts with natural gas and petroleum, the largest deposits of which are located in the politically volatile Persian Gulf. Solid coal cannot directly replace natural gas or petroleum in most applications, petroleum is mostly used for transportation and the natural gas not used for electricity generation is used for spacewater and industrial heating. Coal can be converted to gas or liquid fuel, but the efficiencies and economics of such processes can make them unfeasible. Vehicles or heaters may require modification to use coal-derived fuels. Coal can produce more pollution than petroleum or natural gas.

Fuel transport and delivery

Some plants are built near coal mines and coal is delivered by conveyors. Plants may get as many as three to five trains a day, especially in «peak season» during the hottest summer or coldest winter months (depending on local climate) when power consumption is high. A large thermal power plant stores several million metric tons of coal for winter use when the lakes are frozen.

Modern unloaders use rotary dump devices, which eliminate problems with coal freezing in bottom dump cars. The unloader includes a train positioner arm that pulls the entire train to position each car over a coal hopper. The dumper clamps an individual car against a platform that swivels the car upside down to dump the coal. Swiveling couplers enable the entire operation to occur while the cars are still coupled together. Unloading a unit train takes about three hours.

For start up or auxiliary purposes, the plant may use fuel oil as well. Fuel oil can be delivered to plants by pipelinetankertank car or truck. Oil is stored in vertical cylindrical steel tanks with capacities as high as 90,000 barrels (14,000 m3)’ worth.

Plants fueled by natural gas are usually built adjacent to gas transport pipelines or have dedicated gas pipelines extended to them.

Fuel processing

Coal is prepared for use by crushing the rough coal to pieces less than 2 inches (5 cm) in size. The coal is then transported from the storage yard to in-plant storage silos by rubberized conveyor belts at rates up to 4,000 short tons per hour.

In plants that burn pulverized coal, silos feed coal pulverizers (coal mills) that take the larger 2-inch (51 mm) pieces, grind them to the consistency of face powder, sort them, and mix them with primary combustion air which transports the coal to the boiler furnace and preheats the coal in order to drive off excess moisture content. A 500 MWe plant may have six such pulverizers, five of which can supply coal to the furnace at 250 tons per hour under full load.

In plants that do not burn pulverized coal, the larger 2-inch (51 mm) pieces may be directly fed into the silos which then feed either mechanical distributors that drop the coal on a traveling grate or the cyclone burners, a specific kind of combustor that can efficiently burn larger pieces of fuel.

Vocabulary

fossil fuels — ископаемое топливо

combustion – сгорание

reciprocating internal combustion engine – поршневой двигатель внутреннего сгорания

cooling tower  — охлаждающая башня

flue gas — топочный (дымовой) газ

carbon dioxide – углекислый газ

nitrogen oxide – оксид азота

fly ash — летучая зола, зольная пыль

carbon capture – поглощение углерода

oil shale — нефтеносный сланец

closed-loop cycle – замкнутый цикл

combustion furnace — пламенная печь

cogeneration plant — теплоэлектростанция

oil refinery — нефтеперегонный завод

exceed — превышать

fuel cells – топливные элементы, баки

abundant – обильный, богатый

petroleum — нефть

unfeasible — невыполнимый

conveyor — конвейер

consumption — потребление

unloader — разгрузочная машина

rotary dump device – вращательное свалочное устройство

a coal hopper — угольный бункер

clamp – схватывать, скреплять, зажимать

swivel — вращать

coupler — сцепщик

tank car — цистерна

pipeline — трубопровод

in-plant storage silo – бункер для хранения на территории станции

pulverized coal — угольная пыль

grind — дробить

face powder — пудра

preheat — разогреть

excess moisture content – избыточная влажность

MWe — мегаватт электроэнергии

a traveling grate — движущаяся колосниковая решётка

cyclone burner – циклонная горелка, топка

1.Read the text and translate it.

2. Put the following words into the gaps:

chemical biomass energy vapour greenhouse combustion

Fossil fuel power stations have rotating machinery to convert the heat energy of ……. into mechanical energy.

All plants use the……  extracted from expanding gas — steam or combustion gases.

This gas contains carbon dioxide, water……, as well as substances such as nitrogen oxides (NOx), sulfur oxides (SOx), mercury, traces of other metals, and, for coal-fired plants, fly ash.

Fossil fueled power stations are major emitters of CO2, a ….. gas (GHG) which according to a consensus opinion of scientific organisations is a contributor to global warming as it has been observed over the last 100 years.

In a fossil fuel power plant the …. energy stored in fossil fuels such as coalfuel oilnatural gas or oil shale and oxygen of the air is converted successively into thermal energymechanical energy and, finally, electrical energy

Most thermal power stations in the world use fossil fuel, outnumbering nucleargeothermal,…… or solar thermal plants.

3. Translate from Russian into English:

— преобразовать часть тепловой энергии в механическую работу

— отработанное тепло

— охлаждающая среда

— повысить температуру печи

— дешевое топливо

— залежи

— загрязнение

— доставлять

— уменьшать

— давать возможность, делать возможным

— выделенный трубопровод

— консистенция

— распределитель

— кидать

4. Name the paronymous words to the following:

Convey load couple modify heat

5. Find in the text the sentences with the predicate in the Passive Voice. Make the sentences active? If it is possible.

.

e.g. The core is cooled by ordinary water. — Ordinary water cools the core.

6.Find English equivalents in the text to the following Russian sentences:

Все станции используют энергию, выделяемую из расширяющегося газа – пара или газообразных продуктов сгорания.

Дымовой газ, выделяемый при сгорании ископаемого топлива, попадает в воздух.

Твердые отходы, образующиеся в угольном бойлере, должны быть удалены.

Отработанное тепло не может быть конвертировано в механическую энергию без охлаждающей системы.

Станции, работающие на натуральном газе, обычно строятся рядом с газовым трубопроводом.



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