Joint OSPE – PEO Chapter

Energy Policy Presentation

Prepared by OSPE’s Energy Task Force

Oct 2013

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Productive Use of Nuclear Spent Fuel

Data Sources

CANDU and PWR Fuel Cycles

Useable Components of Used Fuel

Thermal versus Fast Neutron Reactors

Uranium versus Thorium Fast Neutron Reactors

Reducing Lifetime and Radio-toxicity of Used Fuel

Advantages of Reprocessing Used Fuel for Energy

Challenges to Developing Fast Reactors

Q&A period.

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“Plentiful Energy – The Story of the Integral Fast Reactor”, Charles E. Till and Yoon Il Chang, available from www.amazon.ca

“Thorium – Energy Cheaper than Coal”, Robert Hargrave, available from www.amazon.ca

“Why Throw It Away? Productive Use of Nuclear Spent Fuel”, Peter Ottensmeyer, PEO-OSPE Joint Technical Forum, April 2013.

“CANDU Spent Fuel: A Waste or a Resource?”, D. Rozon, NWMO Advisory Council Discussion Paper, Jan 2005.

“Reprocessing Versus Direct Disposal of Spent CANDU Nuclear Fuel: A Possible Application of Fluoride Volatility”, D. Rozon and D. Lister, Jan 2008.

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

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A chain reaction only occurs with fissile isotopes. For thermal neutrons, U235 is the only fissile isotope found in nature. Fast neutrons can fission most transuranic (actinide) elements (Np, Pu, Am, Cm, etc.)

Nuclear reactor fuel can come in two forms. Fissile isotopes and fertile isotopes. However, we can make more fissile isotopes by adding neutrons to a fertile isotope inside a reactor.

Ontario’s CANDU reactors use natural uranium fuel with 0.72% U235 and 99.28% U238 and a heavy water moderator.

PWR reactors use enriched uranium fuel at typically 3.2% U235 (enriched) and 96.8% U238 and ordinary (light) water moderator.

To make enriched fuel we also create a depleted uranium stockpile as part of the fuel cycle. Depleted uranium is primarily U238 which has low levels of radioactivity because it does not go through the reactor. It is stored in drums.

CANDU reactors utilize Uranium about 30% more efficiently than PWR reactors due to a more neutron efficient heavy water moderator. However, because all the original mined Uranium goes through the reactor, CANDU reactors produce more high level used fuel waste by weight per kWh compared to PWR’s.

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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 Actinides: 0.67% 3.21%

Total 100.00% 100.00%

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Thermal Neutrons (found in CANDU, PWR, BWR)

typically 0.025 eV (moves at about 2.2 km/sec).

do not fission actinides very well (only 1% of Pu240 and

Pu242).

are absorbed readily by Xe135 which interferes with

reactor operation and can poison out a reactor after a

power reduction.

thermal reactors cannot load cycle easily.

thermal reactors consume only about 1% of fuel.

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Fast Neutrons (found in LFTR, IFR, FBR)

typically 2 MeV (about 20,000 km/sec).

efficiently fission actinides (about 55% of Pu240 & Pu 242).

are NOT absorbed readily by Xe135.

fast reactors can load cycle easily.

fast reactors with recycling consume nearly 100% of fuel.

fast reactors with no recycling consume about 20% of fuel.

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Uranium Fast Reactors (Integral Fast Reactor - IFR)

U235 or Pu239 as startup fuel – both are fissile.

U238 is used to breed more Pu239 which is fissile.

Pu239 fission produces excess neutrons that can be used to

breed more fuel than the reactor consumes.

breeding time can be adjusted by design but typically takes

about 9 yrs to double the fuel supply.

breeding capability can expand the supply of fissile isotopes

for thousands of years as energy requirements grow.

passively safe (shuts down on loss of power or coolant flow).

Closest to commercial scale demonstration (about 10 years).

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Thorium Fast Reactors (Liquid Fluoride Thorium Reactor –

LFTR)

typically uses U235 or Pu239 as startup fuel – both are fissile.

Th232 is used to breed U233 which is fissile.

Cannot breed more fuel than consumed due to fewer available

neutrons in the Th232/U233 fission process.

passively safe (shuts down on loss of power or coolant flow).

Not yet ready for commercial scale demonstration (likely 20+

years away).

Thorium is about 3 to 4 times more abundant and more evenly

distributed around the world than uranium.

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Intensity of radioactivity and length of time it lasts are both important measures of radio-toxicity or biological damage potential.

There are 3 major components in thermal reactor used fuel:

U238/U235

Actinides (Np, Pu, Am, Cm, etc.)

Fission products

U238/U235 are essentially natural uranium – long lived but not very radioactive.

Actinides are isotopes made in the reactor when uranium (or other actinides) absorbs a neutron. The group is highly radioactive and has a long life time.

Fission products are the isotopes created from splitting the uranium or actinides. There are both short and long lived fission products. The group is highly radioactive until the constituent isotopes decay.

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Years After U238/ IFR (U) IFR & LFTR LFTR (Th)

Irradiation U235 Actinides Fission Products Actinides

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 “relative” to natural uranium is shown. The values have been rounded for readability.

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Recycling allows us to separate the waste into two piles.

One pile contains the fission products that will be directed to a storage facility that would be designed for 400 years of storage. Storage can be on the surface, in an above ground mine or in a deep geological repository (DGR) depending on public acceptance. Theoretically after the fission products have decayed sufficiently we could retrieve and extract the rare earth isotopes for industrial use.

The other pile contains the U238/U235 and actinides. These can be sent back into the reactor to be consumed to produce either thermal or electrical energy.

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While the advantages appear substantial we also have a number of challenges to overcome:

some technical uncertainties still need to be resolved as we scale up the facilities to commercial size.

fuel reprocessing needs to be improved to extract at least 99.9% of the actinides out of the fission product pile otherwise the storage duration will significantly exceed 400 years.

recycling is currently expensive using chemical separation processes. Electrolysis processes promise to be more cost effective but they have not yet been developed to commercial scale.

governments are reluctant to step up and put billions of dollars on the table to develop and license a completely new reactor type.

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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