Lecture18-ComponentsofNuclearPowerPlant_2

8/9/2019 Lecture18-ComponentsofNuclearPowerPlant_2

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Page 1 of 5Lecture 18

Lecture 18: Components of

Nuclear Power PlantThe Nuclear Power Station

A Nuclear power station uses nuclear energy for generating electrical energy.

This power station is generally located far from populated areas. This kind of power station can be used to produce large amounts of electrical energy. In most countries these power stations areused as Base load power stations. This is because they can take several days to be warmed up and

brought on-line.

Operation

Heavy elements such as ranium ! "#$ % or Thorium !Th "#" % are sub&ected to nuclear fission ina reactor to produce steam at high temperatures and pressure.

'team runs a steam turbine which converts this energy into mechanical energy.

The turbine drives the alternator which converts mechanical energy into electrical energy.

Pros & Cons: what this power station presents

Advantages Disadvantages'mall amounts of fuel re(uired )uel is e*pensive and hard to recover +ower plant re(uires less space ,apital cost very high

ow running charges rection / commissioning of plant re(uiresgreat technical knowledge

conomical for producing bulk electricalenergy

)ission by-products are generally 0adioactive/ may cause nuclear pollution

arge available deposits of fuel around theworld

1aintenance costs are high

0eliability of operation Not suited for varying loads as reactor does notrespond to fluctuations

2oes not re(uire large (uantities of water for cooling

2isposal of nuclear by-product is difficult / problematic

)uture generations will want to depend more on this type of electricity generating power station!and other renewable energy sources%3 due to a fast increasing depletion of fuels !,oal%. There area number of construction pro&ects currently underway for this kind of power station around theworld.


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Steam Power station Schematic arrangement

Figure 18 1: Nuclear power plant!pressuri"ed water reactor Sche#atic

Constituents o$ Nuclear power station

)igure 45.4 shows a schematic of the general arrangement of a nuclear power station. Theconstituents of the schematic are labeled in the table below as follows6

%ocationo$ Nuclear power station: influencing factors

Availa ilit' o$ water:'ufficient water must be available for cooling3 thus plant must be situated near a river or by sea-side.

7ey for figure schematic!4%--reactor block !"%--cooling tower !#%8reactor !49%--river !"4%--pump!:%--control rod !$%--support for pressure !9%--steam generator !4;%--cooling-water circulation

!;%--fuel element !5%--turbine !


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Disposal o$ waste:>aste produced is generally reactive3 and thus must be disposed of properly to avoid healthha?ards. >aste must be disposed in deep trench or in sea away from shore.

Distance $ro# populated areas:1ust be far away from populated areas as there may be radio-active particles in the atmospherenear plant. However3 the radio-activity released by a nuclear power plant is significantly less thana similar coal-powered plant.

Transportation $acilities:The site should be accessible by rail and !or% road for ease in transporting e(uipment /machinery.

Design (e)uire#ents and *ngineering Considerations

Fuel Consu#ption

)ission )ragments are the result of fission 'ome fragments are neutron absorbers >hen too many fragments e*ist3 and not enough fresh fuel e*ists to compensate3 the fuel

bundle must be replaced with a new or less @burnt fuel assembly

Forms of Uranium in Power Reactor Fuel 4. ranium 1etal". ranium Cther 1etal Alloy#. ,eramic ranium 2io*ide:. ranium ,arbide$. ranium 'ilicide

Desirable Fuel Material Properties4. ow cost - constituents and fabrication". Dood neutron economy#. Dood corrosion resistance to coolant:. +hysical stability under effects of irradiation3

temperature3 +ressure

(eactor Coolants

,oolants transfer thermal energy and keep the fuel from overheating 1ost reactors use water as both coolant and moderator

Alternative Power Reactant Coolant 4. ,C " Das". Helium#. Crdinary >ater

Fig. 18.2: Basic Reactor Fuel Arrangement


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:. Heavy >ater $. Crganic )luid9. i(uid 1etal

Desirable Properties of Reactant Coolant 4. High heat capacity". Dood heat transfer properties#. ow neutron absorption:. ow neutron activation$. ow operating pressure re(uirement at high operating temperature9. Non-corrosive to fuel cladding and coolant system;. ow cost

+oderators , (e$lectors

1oderators slow neutrons down so they are available for fission 'ome of these use @Heavy >ater at the moderator 'ome use graphite as the moderator The purpose of the reflector is to reflect !as a mirror% some of the escaping neutrons back into

the core area where they become available to induce fission. >ater serves this function in most reactor designs.

Alternative Power Reactor Moderators4. Draphite". Crdinary >ater#. Heavy >ater

Desirable Properties of Reactant Moderators4. High moderating efficiency

". ow neutron absorption#. )reedom from damage E irradiation corrosion:. ow cost E 0aw material3 manufacture3 installation

Control +aterial

,ontrol 0ods i(uid material Installed +oisons

All absorb neutrons3 making them unavailable for fission

Fig. 18.3: Moderating Arrangement


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(eactor Si"e and Shape

eakage depends on surface area of core Neutron production is enhanced with a larger core

volume3 since more fuel can be put into the core A ,ylindrical shape is used 'urface Folume ratio will be small 0eactor si?e is based on the desired power level and

safety considerations

Fig. 18.4: The Control Rods

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