Generation IV Reactors - PDF Free Download

Generation IV Reactors Richard Stainsby National Nuclear Laboratory Recent Ex-Chair of the GFR System Steering Committee Euratom member of the SFR System Steering Committee

What are Generation IV reactors? Slide 2

Objectives of Generation IV Reactors SUSTAINABILITY To make better use of natural uranium Continued avoidance of greenhouse gas emissions from electricity generation To displace fossil fuels from traditional process heat markets To minimise the volume and long-term radiotoxicity of spent fuel wastes ECONOMICAL SAFE to be as safe as, or safer than current Gen III+ reactors PROLIFERATION RESISTANT Slide 3

Motivation for Generation IV SUSTAINABILITY Nuclear Power with today s Gen II (and soon Gen III/III+) reactor technology avoids significant greenhouse gas emissions from electricity generation Other than some application to desalination of seawater and district heating, no use has been made of nuclear-generated process heat All current Gen II/III reactors run on uranium (natural and enriched in U235) Uranium is a very finite resource (~100 years conventional U remaining) Plutonium extracted from spent fuel can be used as a fuel, but Gen II/III reactors make inefficient use of Pu. Slide 4

Some facts about natural uranium Natural uranium occurs with "fissile" and "fertile" isotopes: A fissile isotope can undergo fission easily in the world s power (thermal) reactors to release energy. A fertile isotope does not fission readily in a thermal reactor, but some of it is converted into a fissile isotope in reactor. Only 0.72% of natural uranium is fissile (uranium-235): 0.72% uranium-235 0.0055% uranium-234 99.2745% uranium-238 Global reserves of natural uranium: Known reserves, 7x10 6 tonnes Speculative reserves, 10.4x10 6 tonnes Annual global consumption: 2010, 64x10 3 tonnes/year for a 375 GWe global fleet (Source: 2011 OECD/NEA-IAEA "Red Book") 2035, 98x10 3 136x10 3 tonnes/year for a 540 746 GWe fleet Slide 5 5

PWR fuel element (Mitsubishi Nuclear Fuel Co. Ltd) Slide 6

Spent fuel is not so spent! 20 kg of fissile material Fresh Fuel 9.3 kg of fissile material Spent Fuel Slide 7

Open versus closed fuel cycles Open fuel cycle Closed fuel cycle Slide 8

Minor Actinides (Transuranic elements) A small fraction of heavy elements are produced in the reactor through neutron captures in plutonium: Americium (Am) Curium (Cm) Neptunium (Np) Whilst a small fraction of waste these nuclides are very significant radiologically: Very radiotoxic + very long half lives At present minor actinides are disposed of along with spent fuel (no reprocessing) or along with the fission products (after reprocessing). Slide 9

Relative radiotoxicity Benefit of removing Pu and minor actinides from HLW MA + FP Pu + MA + FP Plutonium recycling Spent fuel direct disposal Uranium ore (mine) FP P&T of MA Time (years) Slide 10

Nuclear process heat co-generation Lower temperature applications: e.g., seawater desalination, district heating uses for waste heat so can be served by all reactors types Higher temperature applications: e.g., chemicals production, oil refining, hydrogen production or advanced steelmaking. can only be served by the High Temperature gas-cooled Reactor, or HTR. Slide 11

New technology is needed to make better use of natural uranium better by two orders of magnitude Reactor operating temperatures need to be increased dramatically compared with Gen II/III light water reactors to become a versatile source of process heat. Slide 12

Basic elements of a reactor system Fuel to undergo fission to generate neutrons and heat Coolant to remove heat and to convert into useful work System to enable and control fission reaction System to confine radionuclides Slide 13

But we have a zoo of options! Uranium-thorium fuel Uranium fuel Ceramic clad fuel Metal fuel Metal clad fuel Plutonium-thorium fuel Oxide fuel Nitride fuel Coated particle fuels Plutonium-uranium Carbide fuel fuel Molten salt fuel No moderator Gas coolants Light water moderator Heavy water moderator Graphite moderator Heavy liquid metal coolant Alkali liquid metal coolant Molten salt coolant Light water coolant Slide 14

Revision of Fission Slide 15

And the energy comes from Source: hyperphysics.phy-astr.gsu.edu Slide 16

Critical Fission Chain Reaction The neutrons liberated in a fission event can cause further fissions, provided they are not absorbed within or lost from the system n (absorbed without fission) n n n n U 235 U 235 U 235 n n (leakage) n (leakage) n This reaction is termed a critical reaction because the number of fissions remains constant in each generation (multiplication factor k=1) Slide 17

Avoiding resonance capture in U238 Thermal neutrons Fast neutrons Thermal reactors, e.g., AGR, PWR Epithermal neutrons Fast reactors, e.g., SFR, LFR, GFR Slide 18

Capture without fission in U238 β - β - U 239 23 min Np 239 Pu 2.3 days 239 n U 238 n (leakage) n n n U 235 U 235 U 235 0.063 sec n n U 235 2 β - n (leakage) n (leakage) U 238 Fissile Isotopes 2.3 days Pu 239 Fertile Isotopes Neutrons captured by U238 are not lost completely as they make Pu239, but they are lost from the immediate population that is needed to sustain fission. Slide 19

Plutonium breeding reaction Starts with neutron capture in uranium-238 238 92 U + n 1 239 0 U 92 Uranium-239 has a half-life of 23 minutes and decays to neptunium-239 by beta decay 239 U 239 92 Np 93 + β - + ν Neptunium-239 has a half life of 2.3 days and decays to plutonium 239 by a further beta decay 239 93Np 239 94 Pu + β - + ν Slide 20

What are the ingredients of a self-sustaining closed fuel cycle? Three important commodities: A stock of fissile material A stock of fertile material Excess neutrons Stock of fissile material Dictates the size of the reactor fleet Stock of fertile material Dictates how long the fleet can operate Excess neutrons More than two neutrons from each fission event must survive, i.e., avoid leakage and absorption in everything other than U238 Slide 21

Neutron yields per neutron captured in fissile nuclides U233 yields the most neutrons in a thermal spectrum Pu239 yields the most in a fast spectrum Slide 22

How far can we go with breeding? Scenario 1: LWR fleet All reactors that contain uranium 238 will breed plutonium: The measure of how good a reactor is at breeding is the conversion ratio (or exactly the same thing the breeding ratio), C C = number of fissile items created / number of fissile atoms consumed For thermal reactors C < 1. For fast reactors C 1 (but can be < 1 if we wish) Start with N fissile atoms, after one irradiation we get C N fissile atoms. Theoretically, after many recycles the total number of fissile atoms is: N T = N + CN + C 2 N + C 3 N + C 4 N +. For C < 1, N T N / (1 - C), so for a LWR C ~ 0.5, so N T 2 N Conclusion large-scale MOX recycle in LWRs results in very limited conservation of uranium - in practice degradation of Pu vector means that only on recycle is feasible in a thermal reactor. Slide 23

How far can we go with breeding? Scenario 2: Fast Reactor fleet Using fast reactors we increase the amount of fissile material available by a factor of up to 100 Because: N T = N + CN + C 2 N + C 3 N + C 4 N +. for C 1 In reality we are limited by the amount of uranium 238 that have But we still have enough fuel to last for about 4000 years!. and as much, or more, again in thorium reserves. Pu vector does not degrade in fast reactors so we can recycle indefinitely (or as long as we have U-238 as a feedstock) Slide 24

World energy reserves without fast reactors Slide 25

World energy reserves with fast reactors Slide 26

Making sense of the options in Gen IV Uranium-thorium fuel Uranium fuel Ceramic clad fuel Metal fuel Metal clad fuel Plutonium-thorium fuel Oxide fuel Nitride fuel Coated particle fuels Plutonium-uranium Carbide fuel fuel Molten salt fuel No moderator Gas coolants Light water moderator Heavy water moderator Graphite moderator Heavy liquid metal coolant Alkali liquid metal coolant Molten salt coolant Light water coolant Slide 27

VHTR SCWR MSR Uranium fuel Oxide fuel Coated particle fuels Graphite moderator Gas coolants Uranium fuel Oxide fuel Metal clad fuel Light water moderator Heavy water moderator Light water coolant Plutonium-uranium fuel Plutonium-thorium fuel Uranium-thorium fuel Molten salt fuel Graphite moderator Molten salt coolant Concentric cold duct Gas turbine Hot duct Core Prismatic graphite rods With TRISO particles Shut-down recirculator and IHX The Gen IV Thermal Reactors Slide 28

SFR GFR LFR Plutonium-uranium fuel Metal fuel Oxide fuel Nitride fuel Metal clad fuel No moderator Alkali liquid metal coolant The Gen IV Fast Reactors Plutonium-uranium fuel Carbide fuel Ceramic clad fuel No moderator Gas coolants MSFR Plutonium-thorium fuel Uranium-thorium fuel Molten salt fuel No moderator Molten salt coolant Plutonium-uranium fuel Oxide fuel Nitride fuel Metal clad fuel No moderator Heavy liquid metal coolant Slide 30

Generation IV Proposed systems 3 Fast Reactors Sodium Cooled Fast Reactor (SFR) Lead Cooled Fast Reactor (LFR) Gas Cooled Fast Reactor (GFR) 3 other systems ( thermal, epithermal) Molten Salt Reactor (MSR) (Epithermal) Supercritical Water Reactor (SCWR) (Thermal or possibly fast) Very High Temperature Reactor (VHTR) (Thermal) Fast spectrum versions of the MSR and the SCWR have been proposed since the publication of the roadmap Slide 31

Sodium-cooled fast reactor (SFR) Slide 32

Superphenix Creys-Malville, France Images courtesy of NERSA Slide 33

Superphenix core map Image courtesy of NERSA Slide 34

Current SFR demonstrator concepts Steam generator Secondary pump Combined pump and IHX ASTRID Pool type - France JSFR Loop type - Japan Reactor Vessel Slide 35

UK fast reactors Dounreay Fast Reactor (DFR) metal fuel, highly enriched U235/U238 fuel, sodium-potassium eutectic liquid metal coolant, 72MWth (1959-1977). Prototype fast reactor (PFR), also at Dounreay mixed oxide fuel, Pu/U238, sodium liquid metal coolant, 600MWth (1974-1994). Both now shut down and partially decommissioned. Developed the Commercial Demonstration Fast Reactor (CDFR) 1970 s and 80 s UK was an equal major partner in the development of the European Fast Reactor, EFR, (with France and Germany) 1988-1998 Slide 36

Gas-cooled fast reactor (GFR) Slide 37

Generation IV GFR - Summary Helium coolant Fast neutron spectrum High outlet temperature Back-up for SFR + Transparent coolant + High temperature/efficiency + Strong Doppler effect + Weak void effect + Chemically and neutronically inert coolant + Zero activation cooant - Decay heat removal (LOCA) - High power density - Low thermal inertia - High coolant pumping power Thermal power Coolant in/out System pressure 2400 MWth 400 C/850 C 70 bar Slide 38

GFR fuel initial composite concept A reference GFR core considered by CEA. Cylindrical core filled with hexagonal subassemblies, containing a triangular pitch rod array. Fuel : (U,Pu)C Cladding : SiC/SiCf with an internal metallic liner for leak tightness to prevent fission gas release to coolant) Slide 39

Gas Cooled Fast Reactors: Fuel Element Slide 40

The lead-cooled fast reactor (LFR) Slide 41 41

Gen IV LFR reference concepts Small transportable system (SSTAR) (10-100 MWe) Evolutionary changes may include CLOSURE HEAD CO2 OUTLET NOZZLE (1 OF 8) CO 2 INLET NOZZLE (1 OF 4) Pb-TO-CO 2 HEAT EXCHANGER (1 OF 4) FLOW SHROUD RADIAL REFLECTOR ACTIVE CORE AND FISSION GAS PLENUM FLOW DISTRIBUTOR HEAD CONTROL ROD DRIVES CONTROL ROD GUIDE TUBES AND DRIVELINES THERMAL BAFFLE GUARD VESSEL REACTOR VESSEL Generation IV Nuclear Energy System for the Lead-cooled Fast Reactor Revised on 18 October, 2010 Preparing Today for Tomorrow s Energy Needs Forced cooling Oxide fuel Steam cycle ELFR Hexagonal Wrapped Fas FAs extended to cover gas from lower support ELSY (600 MWe) Slide courtesy of Alex Alemberti, Ansaldo Slide 42 42

Molten Salt (thermal) Reactor (MSR) ORIGINAL GenIV concept uses an epithermal neutron spectrum. The fuel is a liquid and the fuel is also the primary coolant. Slide 43 43

MSFR Closed On-Site Fuel Cycle (Equilibrium Conditions) U + Pu + minor actinides Fission products U238 or Th232 Molten Salt Reactor On-site reprocessing plant Fission products + U + Pu + minor actinides (Am, Np, Cm) Slide 44 44

The MSFR can maintain a sustainable breeding reaction with thorium Image courtesy of H Boussier (CEA) Slide 45 45

Molten Salt Fast Reactor (MSFR) Slide 46 46

Conclusions The case made for the development of Fast Reactors made in the 1940 s and 1950 s is still relevant today. There is a tendency to base decisions about the long term development of fast reactors and closed fuel cycles on the spot price of uranium at the time the decision is taken. Spot prices of commodities just reflect demand at that time and do not necessarily reflect the scarcity of the resource. Majority of systems being considered in Generation IV are fast reactors (or have fast spectrum variants) Without fast reactors, nuclear fission will have a lifespan of only about 100-200 years. With fast reactors we can generate thousands of years of electricity (and other energy forms) using a small refinement of 1970 s technology. Even if the fuel supply arguments are discounted, fast reactorss offer an effective means to manage the build up of spent fuel from Gen II/III plants and to manage Pu stockpiles Slide 47