Nuclear Reactors - Nuclear Reactor Physics and Nuclear Reactor Lab - Lecture Slides, Slides of Nuclear Physics

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Nucular Reactors:

Classification and Technology

Reaction Types

•Three main reaction types:

•Radioactive Decay

•Atomic Batteries•Radioisotope thermoelectric generators

•passive

•Nuclear Fusion

•Not suitable for power production yet •Nuclear Fission

•Used in most reactors including all commercial ones

Radioactive Decay (passive) - RTG

•Electric Generator

•Obtains power from passive radioactive decays•Utilized in satellites and space probes•Seebeck effect

• Junction of two dissimilar metals at differenttemperatures create a current •Fuel

•Long half life, low shielding...•Plutonium 238 most common

Advantages and Disadvantages

•Advantages:

•Relatively constant powerproduction•Useful for long timemissions•Solar Panels not applicable •Disadvantages:

•Decays over time•May require shielding•Radioactive waste

Nuclear Fission Reactors - Overview

•First Reactor:

•Chicago Pile-1•Enrico Fermi in 1942•Inspired by the discovery that Uranium fissions after beingbombarded with neutrons •Fission process creates new neutrons

•Creates chain reaction that needs to be moderated•Unmoderated reaction used for bombs

Nuclear Fission - Process

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Fission is initialized in thereaction chamber

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Creates Chain reaction

Nuclear Fission - Process

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Fission is initialized in thereaction chamber

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Creates Chain reaction

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Moderators are used tocontrol the amount ofneutrons in the reactorchamber

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Heat released from fissionis processed via heatexchangers or directly viasteam turbines

Nuclear Fission - Process

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Turbines create electricityand the coolant is recycledthrough the reactor

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The environmentalproblems with nuclearreactors is the heat that isreleased into theenvironment from thecondensors.

Fast Neutron Reactor

•Fuel must be enriched•Produces fast neutrons•Can be used for transmutation•Fuel Production•Breeder Reactors•Fast Breeder Reactors

Nuclear Fission - Moderators

•Graphite moderate reactors

•Graphite has high neutron absorption cross section •Water moderated reactors

•Heavy water moderated reactors

•can be fueled with unenriched uranium •Light Water moderated reactors

•Negative feedback stabilizes reaction (neutronabsorption)

•Light element moderated reactors

•are moderated by a light elements such as Li or Be •Organically moderated reactors

•Use biphenyl and terphenyl as moderator and coolant

Nuclear Fission Reactors - Coolant

•Pressurized Water Cooling

•specialized pressure vessel•A pressurizer is partiallyfilled with water•steam bubble is maintainedabove it by heating thewater with submergedheaters•Avoid film boiling

Nuclear Fission Reactors - Coolant

•Boiling water reactor

•Simplification of designs for civilian purposes•Heat is generated directly in the reaction chamber•Chamber is still pressurized and boils at about 285 degreesCelsius

Liquid Metal Cooled Reactors

•Liquid metal cooled nuclear reactor

•primary coolant is a liquid metal•Used in nuclear submarine use•extensively studied for powergeneration applications•Fast Breeder Reactors•Lead•Sodium•Bismuth•Mercury

Gas Cooled Reactors

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Gas cooled reactors•^

Use inert gases such as Heliumor Carbon dioxide to cool

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Some heat the gas enough torun turbines

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Older models run through heatexchangers to generate steam

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Can be refuelled while online

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Higher thermal efficiency thanBWRs

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Uses fuel less efficiently though

1. Charge tubes2. Control rods3. Graphite moderator4. Fuel assemblies5. Concrete pressure vessel and radiationshielding6. Gas circulator7. Water8. Water circulator9. Heat exchanger10. Steam