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Session I.4.7

Part I Review of Fundamentals

Module 4 Sources of Radiation

Session 7 Nuclear Reactors

IAEA Post Graduate Educational CourseRadiation Protection and Safety of Radiation Sources

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Overview

In this session we will discuss Nuclear Reactors including

Types Basic Elements

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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) Gas-Cooled Reactors Fast Neutron Reactors Fast Breeder Reactors

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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 Plan

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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 are now operating in Japan; others under construction in several countries

Nine new nuclear reactor designs either approved or at advanced stages of planning

Advanced reactors incorporate safety improvements and are simpler to operate, inspect, maintain and repair

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The new generation of reactors have:

a standardized design to expedite licensing and reduce capital cost and construction time

enhanced safety systems to further reduce the possibility of core melt accidents

higher availability and longer operating life higher burn‑up to reduce fuel use and the

amount of waste, and will be economically competitive in a range of

sizes

Advanced Reactors

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More 'passive' safety features which rely on gravity, natural convection, etc., to avoid accidents

Two broad categories:

Evolutionary - basically new models of existing, proven designs

Developmental - depart more significantly from today’s 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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On‑power refueling is one of the unique features of the CANDU system

Due to the low excess reactivity of a natural‑uranium fuel cycle, the core is designed to be continuously "stoked" with new fuel, rather than completely changed in a batch process (as in LWRs)

This reduces core excess reactivity, and the requirement for burnable poisons, which in turn increases fuel burnup (decreases the fuel throughput rate)

CANDU Reactors

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Other advantages of on‑power refueling include: increased capacity factors (on-line

availability) ability to "fine‑tune" the power distribution ability to detect and remove defective fuel minimization of power perturbations

On‑power refuelling is achieved with two identical fuelling machines that latch on to opposing ends of a designated channel

Each machine, operated remotely from the control room, includes a magazine capable of either discharging new fuel or accepting spent fuel

CANDU Reactors

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Heavy Water

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High TemperatureGas Cooled Reactors

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Pebble Bed Reactor

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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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Reactors of the Future

Future reactors - known as Generation IV Lead-alloy, liquid-metal cooled fast reactor

system (LFR) Molten salt reactor system (MSR) Sodium liquid-metal cooled fast reactor Very high temperature gas-cooled reactor

system (VHTR) Supercritical water-cooled reactor system

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Where to Get More Information

Cember, H., Johnson, T. E., Introduction to Health Physics, 4th Edition, McGraw-Hill, New York (2008)

Martin, A., Harbison, S. A., Beach, K., Cole, P., An Introduction to Radiation Protection, 6th Edition, Hodder Arnold, London (2012)

Glasstone, S., Sesonske, A. Nuclear Reactor Engineering, 4th Edition, Dordrecht:Kluwer Academic Publishers (1995)

The six Generation IV reactor designs were taken from Nuclear News, Nov 2002

More information at: http://www.world-nuclear.org/info/inf08.html