Post on 21-Dec-2015
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Sources of Radiation
Nuclear Power Reactors
Day 4 – Lecture 3
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Objective
To discuss about Nuclear Power Reactors including their Types and Basic Elements
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Contents
Types of Nuclear Reactors• PWRs• BWRs• CANDU• Advanced Nuclear Reactors
Components of a Nuclear Power Plant
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The Beginning
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Fossil vs Nuclear
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Nuclear Reactors
Types of Nuclear Reactors:
Light Water Reactors (LWR) Heavy Water Reactors (HWR) High-Temperature Gas-Cooled Reactors Fast Neutron Fast Breeder
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Primordial Nuclides
Nuclide Half-life Natural Activity
235U 7.04 x 108 yr 0.711% of all natural uranium
238U 4.47 x 109 yr 99.275% of all natural U; 0.5 to4.7 ppm total U in common rocks
232Th 1.41 x 1010 yr 1.6 to 20 ppm in common rocks
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Fission
1n + 235U fission products
available for more fission
Slow Neutron Interactions
the mean number of neutrons released per fission for U-235 is 2.5). This leads to a self-sustaining chain reaction or “critical mass.”
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Boiling Water (BWR)Nuclear Reactors
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Pressurized Water (PWR)Nuclear Reactors
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The next five slides display the main components of a Nuclear Power Plant:
Control Building Containment Building Turbine Building Fuel Building Diesel Generator Building Auxiliary Building
Components of a Nuclear Plant
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Control Building
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Containment Building
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Turbine Building
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Fuel Building
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Diesel Generator andAuxiliary Buildings
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Protective Barriers
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Steam Generator
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Nuclear Reactors
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Advanced Reactors
The first advanced reactors now operating in Japan
Nine new nuclear reactor designs either approved or at advanced stages of planning
Incorporate safety improvements and are simpler to operate, inspect, maintain and repair
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The new generation of reactors have:
a standardised design to expedite licensing, reduce capital cost and reduce construction time
higher availability and longer operating life, will be economically competitive in a range of sizes, further reduce the possibility of core melt accidents
higher burn‑up to reduce fuel use and the amount of waste
Advanced Reactors
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More 'passive' safety features which rely on gravity, natural convection to avoid accidents
Two broad categories:
Evolutionary - basically new models of existing, proven designs
Developmental - depart more significantly from today¹s plants and require more testing and verification before large‑scale deployment
Advanced Reactors
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CANDU Reactors
CANDU stands for "Canada Deuterium Uranium“
It is a pressurized‑heavy‑water, natural‑uranium power reactor designed first in the late 1950s by a consortium of Canadian government and private industry
All power reactors in Canada are CANDU type
The CANDU designer is AECL (Atomic Energy of Canada Limited), a federal crown corporation
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CANDU Reactors
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CANDU Reactors
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High TemperatureGas Cooled Reactors
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High TemperatureGas Cooled Reactors
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Pebble Bed Reactor
In the 1950s, Dr Rudolf Schulten ( 'father' of the pebble bed reactor) had an idea. The idea was to compact silicon carbide coated uranium granules into hard billiard-ball-like
graphite spheres to be used as fuel for a new high-temperature, helium-cooled type of reactor. The idea took root, and in due course, the AVR, a 15 MW (megawatt) demonstration pebble bed reactor, was built in Germany. It operated successfully for 21 years.
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Pebble Bed Reactor
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Pebble Bed Reactor
Potential Problems (according to some groups)
It has no containment building
It uses flammable graphite as a moderator
It produces more high level nuclear wastes than current nuclear reactor designs
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Pebble Bed Reactor
Potential Problems (according to some groups)
It relies heavily on nearly perfect fuel pebbles
It relies heavily upon fuel handling as the pebbles are cycled through the reactor
There's already been an accident at a pebble bed reactor in Germany due to fuel handling problems
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Where to Get More Information
Cember, H., Johnson, T. E, Introduction to Health Physics, 4th Edition, McGraw-Hill, New York (2009)
More information at: http://www.pbmr.co.za/index.htm