Liquid Metal Fast Breeder Reactors Martin W. Metzner November 19, 2007

Overview of Fast Breeder Reactors Produce more fissile material than is consumed Technology first developed in the 1950’s Utilize uranium 60 times as efficienctly as PWRs Cooled by liquid metal

Fast Breeder Reactors vs. Pressurized Water Reactors FBR Fuel is enriched to % Fuel is enriched to % Moderator: none Moderator: none Heat transfer by liquid metal or metal alloys Heat transfer by liquid metal or metal alloys Typically sodium Reactor under low pressure Reactor under low pressure ~1.2 fissile atoms produced per fission ~1.2 fissile atoms produced per fissionPWR Fuel is enriched to 3- 5% Moderator: water Heat transfer by water Reactor under high pressure Fissile material is only consumed

Breeding Fuel Theory Each fission produces on average 2.4 neutrons Each fission produces on average 2.4 neutrons Fissile material: U-235, Pu-239 or Pu-241 Critical reaction Critical reaction One neutron per fission causes another fission 1.4 neutrons are left over to enrich depleted fuel 1.4 neutrons are left over to enrich depleted fuelPractice Typical FBR produces about 1.2 fissile atoms per consumed fissile atom Can produce enough fissile material in 10 years to replace spent fuel and enough to power another reactor for 10 years

FBR Design 1)Highly enriched uranium or plutonium 2)Control rods (same material as core) 3)Depleted uranium 4)Heat is transferred from primary to secondary sodium 5)Heat is transferred from secondary sodium to water Figure: Baksiden, modified by Martin Metzner

Nuclear Fuel Initially FBRs were designed to use pure uranium oxide fuel Eventually switched to MOX Mixed oxide fuel (MOX): Mixed oxide fuel (MOX): Mixture of UO 2 and PuO 2 Already an existing source of fissile plutonium Nuclear warheads Nuclear warheads Highly enriched, former USSR and USA currently dismantling arsenals Depleted PWR fuel Depleted PWR fuel Low enrichment caused by the fusion of U-238 and a neutron Must be processed before it can be used

Liquid Metal Coolant Typical metal used is sodium Some reactors use lead, lead-bismuth alloy, or sodium fluoride salt Some reactors use lead, lead-bismuth alloy, or sodium fluoride salt Advantages of sodium Low melting temperature (98°C) Low melting temperature (98°C) High boiling temperature (892°C) High boiling temperature (892°C) High heat capacity High heat capacity System can run at low pressure System can run at low pressure Risks of sodium Burns when it comes in contact with air or water Burns when it comes in contact with air or water Poisonous fumes Poisonous fumes

FBRs Today Only six active today Half of these are in Russia Half of these are in Russia Average lifespan of reactors is only about 20 years Many shut down prematurely Many shut down prematurely Superphenix (France) and KNK 2 (Germany) were never operational Superphenix (France) and KNK 2 (Germany) were never operational Plagued by political controversy Only one notable accident Monju (Japan) in 1995 Monju (Japan) in 1995 A pipe carrying secondary sodium ruptured A pipe carrying secondary sodium ruptured OutputMweOperation USA EBR EBR Fermi SEFOR Fast Flux TFN/A UK Dounreay FR Prototype FR France RapsodieN/A Phenix Now Superphenix Germany KNK India FBTRN/A1985-Now Japan JoyoN/A1978-Now Monju , 08? Kazakhstan BN Russia BR 5/10N/A , 1973-Now BOR Now BOR Now Table: World Nuclear Association, June 2006

Future of Fast Breeders Next generation may use noble gases such as helium or argon instead of sodium Increase in the breeding ratio Believed that a ratio of 1.3 will be possible Believed that a ratio of 1.3 will be possible Smaller reactors Lower maintenance and repair costs Lower maintenance and repair costs Higher reactor temperatures Can be used for thermochemical hydrogen production Can be used for thermochemical hydrogen production

References Conflict. Baksiden. 16 Nov For image on slide 4. Fast Breeder Reactors. Georgia State University. 16 Nov Fast Neutron Reactors. June World Nuclear Association. 16 Nov Guidez, J, et al. Phenix: The Irradiation Program for Transmutation Experiments. Nuclear Energy Agency. 31 Aug Nov Mixed Oxide Fuel (MOX). Sept Uranium Information Centre. 16 Nov