produc’ve*use*of*nuclear*spent*fuel · 2016-01-14 · produc’ve*use*of*nuclear*spent*fuel%...
TRANSCRIPT
Produc've Use of Nuclear Spent Fuel
Outline of Presenta'on
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² Data Sources ² CANDU and PWR Fuel Cycles ² Useable Components of Used Fuel ² Thermal versus Fast Neutron Reactors ² Uranium versus Thorium Fast Neutron Reactors ² Reducing Lifetime and Radio-toxicity of Used Fuel ² Advantages of Reprocessing Used Fuel for Energy ² Challenges to Developing Fast Reactors ² Q&A period.
Produc've Use of Nuclear Spent Fuel
Data Sources for Today’s Presenta'on
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² “Plentiful Energy – The Story of the Integral Fast Reactor”, Charles E. Till and Yoon Il Chang, available from www.amazon.ca
² “Thorium – Energy Cheaper than Coal”, Robert Hargrave, available from www.amazon.ca
² “Why Throw It Away? Productive Use of Nuclear Spent Fuel”, Peter Ottensmeyer, PEO-OSPE Joint Technical Forum, April 2013.
² “CANDU Spent Fuel: A Waste or a Resource?”, D. Rozon, NWMO Advisory Council Discussion Paper, Jan 2005.
² “Reprocessing Versus Direct Disposal of Spent CANDU Nuclear Fuel: A Possible Application of Fluoride Volatility”, D. Rozon and D. Lister, Jan 2008.
² If you are interested in the other energy related information or downloading this presentation, please visit OSPE’s website at:
http://www.ospe.on.ca/?page=adv_issue_energy
Produc've Use of Nuclear Spent Fuel
CANDU and PWR Fuel Cycles
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² A chain reaction only occurs with fissile isotopes. For thermal neutrons.
² U235 is the only fissile isotope found in nature. ² Fast neutrons can fission most transuranic (actinide) elements
(Np, Pu, Am, Cm, etc.) ² Nuclear reactor fuel can come in two forms. Fissile isotopes
and fertile isotopes. ² We can make more fissile isotopes inside a reactor by adding
neutrons to a fertile isotope. ² Ontario’s CANDU reactors use natural uranium fuel with 0.72%
U235 and 99.28% U238 and a heavy water moderator. ² PWR reactors use enriched uranium fuel at typically 3.2% U235
(enriched) and 96.8% U238 and ordinary (light) water moderator.
Produc've Use of Nuclear Spent Fuel
CANDU and PWR Fuel Cycles
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² To make enriched fuel we also create a depleted uranium stockpile as part of the fuel cycle.
² Depleted uranium is primarily U238 which has low levels of radioactivity because it does not go through the reactor. It is stored in drums.
² CANDU reactors utilize Uranium about 30% more efficiently than PWR reactors due to a more neutron efficient heavy water moderator.
² CANDU reactors produce more high level used fuel waste by weight per kWh compared to PWR’s because all the original mined Uranium goes through the reactor.
Produc've Use of Nuclear Spent Fuel
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Useable Components of Used Fuel
Isotope CANDU PWR U238: 98.58 % 93.79 % U235: 0.23 % 0.91 % U236: 0.07 % 0.40 % Pu239: 0.25 % 0.59 % Pu240: 0.10 % 0.23 % Pu241: 0.02 % 0.08 % Pu242: 0.01 % 0.05 % Waste + Minor Ac,nides: 0.67 % 3.21 %
Total 100.00 % 100.00 %
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Thermal versus Fast Neutrons
² Thermal Neutrons (found in CANDU, PWR, BWR)
² Typically 0.025 eV (move at about 2.2 km/sec).
² Do not fission actinides very well (only 1% of Pu240 and Pu242).
² Are absorbed readily by Xe135 which interferes with reactor operation and can poison out a reactor after a power reduction.
² Thermal reactors cannot load cycle easily.
² Thermal reactors consume only about 1% of fuel.
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Thermal versus Fast Neutrons
² Fast Neutrons (found in LFTR, IFR, FBR)
² Typically 2 MeV (move at 20,000 km/sec). ² Efficiently fission actinides (about 55% of Pu240 & Pu
242). ² Are NOT absorbed readily by Xe135. ² Fast reactors can load cycle easily. ² Fast reactors with fuel recycling consume nearly 100%
of fuel. ² Fast reactors with no recycling consume about 20% of
fuel.
Produc've Use of Nuclear Spent Fuel
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Uranium versus Thorium Fast Neutron Reactors
² Uranium Fast Reactor (Integral Fast Reactor - IFR)
² U235 or Pu239 as startup fuel – both are fissile.
² U238 is used to breed more Pu239.
² Pu239 fission produces excess neutrons that can be used to breed more fuel than the reactor consumes.
² Breeding time can be adjusted by design but typically takes about 9 years to double the fuel supply.
² Breeding capability can expand the supply of fissile isotopes for thousands of years as energy requirements grow.
² Passively safe - shuts down on loss of power or coolant flow. Operates at low pressure – simplifies containment.
² Design close to a commercial scale demonstration (about 10 years away).
Produc've Use of Nuclear Spent Fuel
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Uranium versus Thorium Fast Neutron Reactors
² Thorium Fast Reactors (Liquid Fluoride Thorium Reactor – LFTR) ² Typically uses U235 or Pu239 as startup fuel – both are
fissile. ² Th232 is used to breed U233 which is a fissile isotope. ² Cannot breed more fuel than consumed due to fewer
available neutrons in the Th232/U233 fission process. ² Passively safe - shuts down on loss of power or coolant
flow. ² Not yet ready for commercial scale demonstration
(likely 20+ years away). ² Thorium is about 3 to 4 times more abundant and more
evenly distributed around the world than uranium.
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Reducing Life'me and Radio-‐toxicity of Used Fuel
² Intensity of radioactivity & lifetime are both important measures of radio-toxicity or biological damage potential.
² There are 3 major components in thermal reactor used fuel: ² U238/U235
² Actinides (Np, Pu, Am, Cm, etc.)
² Fission products
² U238/U235 are essentially natural uranium – long lived but not very radioactive.
² Actinides are isotopes made in the reactor via neutron absorption. Actinides are highly radioactive with a long life.
² Fission products are the isotopes created from splitting the uranium or actinides. Both short and long lived products are produced. Highly radioactive until the isotopes have decayed.
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Reducing Life'me and Radio-‐toxicity of Used Fuel
Years AOer U238/ IFR (U) IFR & LFTR LFTR (Th) Irradia,on U235 Ac,nides Fission Products Ac,nides
10 1 1000 1000 700 100 1 1000 100 500 400 1 1000 1 500 1,000 1 1000 0.01 100 10,000 1 800 0.01 30 100,000 1 30 0.007 2 1,000,000 1 0.3 0.002 0.6
Note: Radiological toxicity “rela,ve” to natural uranium is shown. The values have been rounded for readability.
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Advantages of Recycling Used Fuel for Energy
² Recycling allows us to separate the waste into two piles.
² One pile contains the fission products that will be directed to a storage facility that would be designed for 400 years of storage.
² Storage can be on the surface, in an above ground mine or in a deep geological repository (DGR) depending on public acceptance.
² Theoretically after the fission products have decayed sufficiently we could retrieve and extract the rare earth isotopes for industrial use.
² The other pile contains the U238/U235 and actinides. These can be sent back into the reactor to be consumed to produce either thermal (steam) or electrical energy.
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Challenges to Developing Fast Reactors
² While the advantages appear substantial we also have a number of challenges to overcome:
² Some technical uncertainties still need to be resolved as we scale up the facilities to commercial size.
² Fuel reprocessing needs to be improved to extract at least 99.9% of the actinides.
² Chemical recycling is expensive. Electrolysis promises to be more cost effective but not yet proven at commercial scale.
² Governments are reluctant to step up and put billions of dollars on the table for a new reactor type.
² There is no consensus yet of whether the new reactors should be large (>1000 MW) or small factory fabricated units (20 to 100 MW).
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Summary
² IFR and LFTR technology promise a 100 fold increase in energy output and a 1000 fold reduction in radioactive waste lifetime.
² Breeding capability of an IFR can supply enough fissile materials for full utilization of Thorium reserves in an LFTR.
² Technical and cost challenges need to be overcome.
² Fuel reprocessing and proliferation is a public concern.
² Nuclear technology and radioactive wastes is a public concern.
Produc've Use of Nuclear Spent Fuel
Questions ?
Notes: This presenta'on can be downloaded at:hNp://www.ospe.on.ca/?page=adv_peochap Would you like to become a member of OSPE? Visit: hNp://www.ospe.on.ca/?page=JOIN
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