Reactors of the Future

Reed Reactor Special Requal Lecture

Reactors of the Future

Generations III+ through V

Ian Flower

What will we cover?

Tour of Reactor DesignsGeneration III+Generation IVGeneration V

Limitations/Advantages of EachRoad Map for the future


Where are we?


Advanced Reactors

Improvements on current designs:

ABWR (Advanced Boiling Water Reactor)ESBWR (Economic Simplified BWR)Subcritical ReactorsThorium-Based Reactors


ABWR

GE HitachiHuge improvements on existing BWR technology

DigitalEmergency CoolingRecirculationCleanup LoopControl Rod precision


ESBWR

No Recirculation Pumps

Core is shorter

Gravity makes it passively safe.


Generation IV

GoalsEnvironmental FriendlinessMinimization of WasteFuel UtilizationEfficiencyLower costsPassive SafetyEliminate need for offsite emergency responseTerrorist-proof reactors

DesignsGFR (Gas-cooled Fast)LFR (Lead-cooled Fast)SFR (Sodium-cooled Fast)MSR (Molten-Salt Reactor)SCWR (SuperCritical Water)VHTR (Very High Temperature)


Gas-cooled Fast Reactor


Gas-cooled Fast Reactor

GFRCO2 or HeHigher TemperatureNon activated coolantNo flashes to steamHave to consider:

Neutron absorption leads to positive void coefficient

Fuel ElementsCeramicsGood at High TemperatureRetain Fission Fragments


A Note About Fast Reactors

No ModeratorDifficult to controlControl rods are too slow to make adjustmentsStabilized instead by:

Doppler BroadeningNeutron PoisonsNeutron Reflector

Acceptable fuels

Uranium, ObviouslyBut more things, too!

Thorium yields U233TransuranicsBreeder potential


Sodium-cooled Fast Reactor


Sodium-cooled Fast Reactor

The closest to constructionCons:

Sodium activatesSodium is really reactive

Pros:Can reuse high-level waste soonSodium can be kept at atmospheric pressureSodium is a bad moderatorSeveral reactors connected to same water system


Another Note About Fast Reactors

Excess heat can be used to produce Hydrogen fuel

I’ll leave the deciphering of this diagram to others


Lead-cooled Fast Reactor


Lead-cooled Fast Reactor

I know what you’re thinking.WHY LEAD?!

ShieldingTerrorism-PreventionNon moderatorNon-reactingThermal conductivityHigh Boiling Point

But current designs would have cores that last 10-30 years!


A Final Note on Fast Reactors

Nuclear Fuel CycleLife cycle of nuclear fuel from mining to disposal

Open Fuel Cycle (aka once through)

Use the fuel once, dispose of it

Closed Fuel CycleFuel is reprocessed


Molten Salt Reactor


Two types:•LFTR•UF4

Molten Salt ReactorPros:

Leaks are easy to containHigh temperature leads to good thermal efficiencyWork in all sizesAlready proven technologyTerrorist-proofRefuel as you go

Cons:Chemical processing plants can pose additional risks


A Note on the Thorium Fuel Cycle

Thorium is 3-4 times as abundant as U238Thorium comes in the isotope you wantHigher Melting PointHigher Thermal conductivity


What the H is Supercritical Water?


Supercritical Water Reactor


Supercritical Water Reactor

Supercritical Water: not as good of a moderatorPros:

Could operate as a Thermal Reactor or Fast ReactorMuch more efficient energy gainSimpler DesignsDon’t have to be as large

Cons:Need better materialsNeed to figure out how to start upNot sure how it will work


Why would we still use Thermal Reactors?To augment the

cycle that we already have:

Fast reactors make the waste disposal needs of thermal reactors obsoleteThermal reactors generate lots of powerThermal reactors are easy to build and control


Very High Temperature Reactor


Very High Temperature ReactorMost common design:Pebble Bed Reactor

Tennis-ball sized spheres of moderator and fissile materialCeramicsCooled by a gas, can be cooled naturally

Pros:EconomicHydrogen ProductionSafer than current reactors

Cons:Materials research needed


Generation V

Theoretical Designs:

Nuclear Thermal RocketNuclear Lightbulb (Rocket)Fission Fragment Reactor (Rocket)

There is a trend hereReed Reactor Special Requal

Lecture

Nuclear Thermal Rocket

Pass a working fluid through a reactorCreate thrustLiquid Core designs

Liquid mixture of fuel/working gas

Gas Core designsToroidal pocket of gaseous fuel


Nuclear Thermal Rocket

Problems:Not incredibly efficient unless Liquid/GasLiquid/Gas are hard to build

Pros:Liquid/Gas would be amazing


Nuclear Lightbulb

Gas CoreVery Hot

Approx. 25000 CHotter than the surface of the sun

EM produced all UltravioletQuartz wall divides core and propellant


Nuclear LightbulbAs a Power Reactor?

Closed loopWorking gas instead of propellant

Pros:Efficient conversion of energy to power

Cons:25000 C? Wow!Neutron Flux would be unwieldy


Gas Core EM Reactor


Nuclear Lightbulb

Photo-Voltaics

Photo-Voltaics

Fission Fragment Rocket

The concept:Fission produces heavy, high energy byproductsExhaust the fission fragments!


Fission Fragment Rocket


a fissionable filaments, b revolving disks,c reactor core, d fragments exhaust

A fission fragments ejected for propulsionB reactorC fission fragments decelerated for power generationd moderator (BeO or LiH), e containment field generator, f RF induction coil

Fission Fragment Reactor

But what about power?

Part C produce electricity

Pros:Skip the Carnot CycleIncredibly efficientIsotopic Separation


Timeline

Viability:Show that it all works in theory

PerformanceShow that it all works individually in practice

DemonstrationBuild large prototypes and watch carefully


Two Graphs For You


Date post:	16-May-2015
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Reactors of the Future

Technology