Institute of Physics, University of Birmingham, 2 November 2016
Generation IV Reactors
Richard StainsbyNational Nuclear LaboratoryRecent Ex-Chair of the GFR System Steering Committe eEuratom member of the SFR System Steering Committee
Slide 2Institute of Physics, University of Birmingham, 2 N ovember 2016
What are Generation IV reactors ?
Slide 3Institute of Physics, University of Birmingham, 2 N ovember 2016
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 4Institute of Physics, University of Birmingham, 2 N ovember 2016
Motivation for Generation IV• SUSTAINABILITY
• Nuclear Power with today’s Gen II (and soonGen 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 5Institute of Physics, University of Birmingham, 2 N ovember 2016
• 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 the rmal reactor, but some
of it is converted into a fissile isotope in reac tor.
• Only 0.72% of natural uranium is fissile (uranium-2 35):– 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, 64x103 tonnes/year for a 375 GWe global fleet
– 2035, 98x103 → 136x103 tonnes/year for a 540 → 746 GWe fleet
Some facts about natural uranium
5
(Source: 2011 OECD/NEA-IAEA "Red Book")
Slide 6Institute of Physics, University of Birmingham, 2 N ovember 2016
PWR fuel element (Mitsubishi Nuclear Fuel Co. Ltd)
Slide 7Institute of Physics, University of Birmingham, 2 N ovember 2016
Spent Fuel
Fresh Fuel20 kg of fissile material
9.3 kg of fissile material
Spent fuel is not so spent !
Slide 8Institute of Physics, University of Birmingham, 2 N ovember 2016
Open versus closed fuel cycles
Open fuel cycle
Closed fuel cycle
Slide 9Institute of Physics, University of Birmingham, 2 N ovember 2016
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 10Institute of Physics, University of Birmingham, 2 N ovember 2016
Uranium ore (mine)
Time (years)
Rel
ativ
e ra
dio
toxi
city
Spent fueldirect disposal
Pu +MA +FP
Plutonium recycling
MA +FP
P&T of MAFP
Benefit of removing Pu and minor actinides from HLW
Slide 11Institute of Physics, University of Birmingham, 2 N ovember 2016
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 12Institute of Physics, University of Birmingham, 2 N ovember 2016
“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 13Institute of Physics, University of Birmingham, 2 N ovember 2016
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 14Institute of Physics, University of Birmingham, 2 N ovember 2016
Coated particle fuels
But we have a zoo of options !
Uranium fuel Metal fuelMetal fuel
Oxide fuelOxide fuelNitride fuelNitride fuel
Carbide fuel Plutonium-uranium fuelPlutonium-uranium fuel
Uranium-thorium fuel
Molten salt fuel
Metal clad fuelMetal clad fuelCeramic clad fuel
Graphite moderatorLight water moderator Heavy water moderator
Molten salt coolantAlkali liquid metal coolant
Heavy liquid metal coolant
Gas coolants
Light water coolant
No moderatorNo moderator
Plutonium-thorium fuel
Slide 16Institute of Physics, University of Birmingham, 2 N ovember 2016
… And the energy comes from …
• Source: hyperphysics.phy-astr.gsu.edu
Slide 17Institute of Physics, University of Birmingham, 2 N ovember 2016
Critical Fission Chain Reaction
n U235 U235 U235
n (absorbed without fission)
n (leakage)
n
n (leakage)
n
n
n
n
This reaction is termed a “critical” reaction because the number of fissions remains constant in each generation (multiplication factor k=1)
The neutrons liberated in a fission event can cause further fissions, provided they are not absorbed within or lost from the system
Slide 18Institute of Physics, University of Birmingham, 2 N ovember 2016
Avoiding resonance capture in U238
Thermal neutrons
Fast neutrons
Epithermal neutrons
Thermal reactors, e.g.,AGR, PWR
Fast reactors, e.g., SFR, LFR, GFR
Slide 19Institute of Physics, University of Birmingham, 2 N ovember 2016
Capture without fission in U238
n U235 U235 U235
n (leakage)
n n
n (leakage)
n
n
n U238
Np239 Pu239 U239
n (leakage) U238
Pu239
U235
β-
β-
23 min 2.3 days
2.3 days
2 β- 0.063 sec
Fissile Isotopes
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 20Institute of Physics, University of Birmingham, 2 N ovember 2016
Plutonium breeding reaction
U23892 + n1
0 → U23992
Starts with neutron capture in uranium-238
Uranium-239 has a half-life of 23 minutes and decays to neptunium-239 by beta decay
U23992 → Np239
93 + β- + ν
Np23993
→ Pu23994 + β- + ν
Neptunium-239 has a half life of 2.3 days and decays to plutonium 239 by a further beta decay
Slide 21Institute of Physics, University of Birmingham, 2 N ovember 2016
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 22Institute of Physics, University of Birmingham, 2 N ovember 2016
Neutron yields per neutron captured in fissile nucl ides
• U233 yields the most neutrons in a thermal spectrum• Pu239 yields the most in a fast spectrum
Slide 23Institute of Physics, University of Birmingham, 2 N ovember 2016
How far can we go with breeding ?Scenario 1: LWR fleet• All reactors that contain uranium 238 will breed pl utonium:
• The measure of how good a reactor is at breeding is the “conversion ratio” (or exactly the same thing – the breeding rati o), CC = number of fissile items created / number of fis sile atoms consumedFor thermal reactors C < 1. For fast reactors C ≥ 1 (but can be < 1 if we
wish)
Start with N fissile atoms, after one irradiation w e get C×N fissile atoms.
Theoretically, after many recycles the total number of fissile atoms is:
NT = N + CN + C2N + C3N + C4N + ….
For C < 1, NT → 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 o f Pu vector means that only on recycle is feasible in a thermal react or.
Slide 24Institute of Physics, University of Birmingham, 2 N ovember 2016
How far can we go with breeding ?Scenario 2: Fast Reactor fleet
Using fast reactors we increase the amount of fissi le material available by a factor of up to 100
Because:
NT = N + CN + C2N + C3N + C4N + ….→∞ 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 ca n recycle indefinitely (or as long as we have U-238 as a feedstock)
Slide 25Institute of Physics, University of Birmingham, 2 N ovember 2016
World energy reserves without fast reactors
Slide 26Institute of Physics, University of Birmingham, 2 N ovember 2016
World energy reserves with fast reactors
Slide 27Institute of Physics, University of Birmingham, 2 N ovember 2016
Coated particle fuels
Making sense of the options in Gen IV
Uranium fuel Metal fuelMetal fuel
Oxide fuelOxide fuelNitride fuelNitride fuel
Carbide fuel Plutonium-uranium fuelPlutonium-uranium fuel
Uranium-thorium fuel
Molten salt fuel
Metal clad fuelMetal clad fuelCeramic clad fuel
Graphite moderatorLight water moderator Heavy water moderator
Molten salt coolantAlkali liquid metal coolant
Heavy liquid metal coolant
Gas coolants
Light water coolant
No moderatorNo moderator
Plutonium-thorium fuel
Slide 28Institute of Physics, University of Birmingham, 2 N ovember 2016
Coated particle fuels
VHTR SCWR MSR
Oxide fuelOxide fuel Uranium-thorium fuel
Molten salt fuelMetal clad fuelMetal clad fuel
Graphite moderatorLight water moderator
Heavy water moderator Molten salt coolantGas coolants Light water coolant
Plutonium-thorium fuelPlutonium-uranium fuelPlutonium-uranium fuel
Oxide fuelOxide fuel
Uranium fuel
Graphite moderator
Uranium fuel
CorePrismatic graphite rodsWith TRISO particles
Hot duct
Concentriccold duct
Shut-downrecirculator and IHX
Gas turbine
The Gen IV Thermal Reactors
Slide 29Institute of Physics, University of Birmingham, 2 N ovember 2016
Coated particle fuels
Uranium fuel Metal fuelMetal fuel
Oxide fuelOxide fuelNitride fuelNitride fuel
Carbide fuel Plutonium-uranium fuelPlutonium-uranium fuel
Uranium-thorium fuel
Molten salt fuel
Metal clad fuelMetal clad fuelCeramic clad fuel
Graphite moderatorLight water moderator Heavy water moderator
Molten salt coolantAlkali liquid metal coolant
Heavy liquid metal coolant
Gas coolants
Light water coolant
No moderatorNo moderator
Plutonium-thorium fuel
Making sense of the options in Gen IV
Slide 30Institute of Physics, University of Birmingham, 2 N ovember 2016
SFR GFR LFR
Nitride fuelNitride fuel
Carbide fuelPlutonium-uranium fuelPlutonium-uranium fuel
Uranium-thorium fuel
Molten salt fuel
Metal clad fuelMetal clad fuel
Ceramic clad fuel
Molten salt coolant
Heavy liquid metal coolant
No moderatorNo moderator
Plutonium-thorium fuel
Gas coolants
Plutonium-uranium fuelPlutonium-uranium fuel
Oxide fuelOxide fuel
No moderatorNo moderator
Metal fuelMetal fuel
Nitride fuelNitride fuel
Metal clad fuelMetal clad fuel
Alkali liquid metal coolant
Plutonium-uranium fuelPlutonium-uranium fuel
Oxide fuelOxide fuel
No moderatorNo moderator
No moderatorNo moderator
MSFR
The Gen IV Fast Reactors
Slide 31Institute of Physics, University of Birmingham, 2 N ovember 2016
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 32Institute of Physics, University of Birmingham, 2 N ovember 2016
Sodium -cooled fast reactor (SFR)
Slide 33Institute of Physics, University of Birmingham, 2 N ovember 2016
Superphenix – Creys -Malville , France
Images courtesy of NERSA
Slide 34Institute of Physics, University of Birmingham, 2 N ovember 2016
Superphenix core map
Image courtesy of NERSA
Slide 35Institute of Physics, University of Birmingham, 2 N ovember 2016
Current SFR demonstrator concepts
ASTRID – Pool type - France JSFR – Loop type - J apan
Secondary pump
Steam generator
Reactor Vessel
Combined pumpand IHX
Slide 36Institute of Physics, University of Birmingham, 2 N ovember 2016
UK fast reactors• Dounreay Fast Reactor (DFR) – metal fuel, highly enri ched U235/U238
fuel, sodium-potassium eutectic liquid metal coolan t, 72MWth (1959-1977).
• Prototype fast reactor (PFR), also at Dounreay – mixe d 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 37Institute of Physics, University of Birmingham, 2 N ovember 2016
Gas-cooled fast reactor (GFR)
Slide 38Institute of Physics, University of Birmingham, 2 N ovember 2016
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 2400 MWth
• Coolant in/out 400°C/850°C
• System pressure 70 bar
Slide 39Institute of Physics, University of Birmingham, 2 N ovember 2016
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 40Institute of Physics, University of Birmingham, 2 N ovember 2016
Gas Cooled Fast Reactors: Fuel Element
Slide 41Institute of Physics, University of Birmingham, 2 N ovember 2016
The lead-cooled fast reactor (LFR)
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Slide 42Institute of Physics, University of Birmingham, 2 N ovember 2016
Gen IV LFR reference concepts
CLOSURE HEAD
CO 2 INLET NOZZLE
(1 OF 4)
CO2 OUTLET NOZZLE
(1 OF 8)
Pb-TO-CO2 HEAT EXCHANGER (1 OF 4)
ACTIVE CORE AND FISSION GAS PLENUM
RADIAL REFLECTOR
FLOW DISTRIBUTOR HEAD
FLOW SHROUDGUARD VESSEL
REACTOR VESSEL
CONTROL ROD DRIVES
CONTROL
ROD GUIDE TUBES AND DRIVELINES
THERMAL BAFFLE
Small transportable system(SSTAR) (10 - 100 MWe)
Evolutionary changesmay include
Forced coolingOxide fuelSteam cycle
ELSY (600 MWe)
ELFRHexagonal Wrapped FasFAs extended to cover gas from lower support
Generation IV Nuclear Energy System for the Lead-cooled Fast Reactor
Preparing Today for Tomorrow’s Energy Needs
Revised on 18 October, 2010
Slide courtesy of Alex Alemberti, Ansaldo42
Slide 43Institute of Physics, University of Birmingham, 2 N ovember 2016 43
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 44Institute of Physics, University of Birmingham, 2 N ovember 2016 44
MSFR – Closed On -Site Fuel Cycle(Equilibrium Conditions)
U238 or Th232
Fission products + U + Pu + minor actinides (Am, Np, Cm)
On-site reprocessing
plant
Fission products
U + Pu + minor actinides
Molten Salt Reactor
Slide 45Institute of Physics, University of Birmingham, 2 N ovember 2016
The MSFR can maintain a sustainable breeding reaction with thorium
Image courtesy of H Boussier (CEA)45
Slide 46Institute of Physics, University of Birmingham, 2 N ovember 2016
Molten Salt Fast Reactor (MSFR)
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Slide 47Institute of Physics, University of Birmingham, 2 N ovember 2016
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 lon g 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 t hat time and do
not necessarily reflect the scarcity of the resourc e.• 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 yea rs of electricity
(and other energy forms) using a small refinement o f 1970’s technology.
• Even if the fuel supply arguments are discounted, f ast reactorss offer an effective means to manage the build up of spent fuel from Gen II/III plants and to manage Pu stockpiles