The Helen Caldicott Foundation | Can Nuclear Power Slow Down Climate Change? An analysis of nuclear greenhouse gas emissions.

Can Nuclear Power Slow Down Climate Change? An analysis of nuclear greenhouse gas emissions.

Can Nuclear Power Slow Down Climate Change? An analysis of nuclear greenhouse gas emissions.

Can Nuclear Power Slow Down Climate Change  (click title to access link to PDF of full report)

By Jan Willem Storm van Leeuwen Ceedata Consultancy

Commissioned by the World Information Service on Energy (WISE) Amsterdam, The Netherlands, November 2015

Supporting organizations:
Sortir du Nucléaire, France, Women in Europe for a Common Future (WECF), Nuclear Information & Resource Service (NIRS), USA, Ecodefense, Russia, Global 2000 (Friends of the Earth), Austria, Bürgerinitiative Lüchow-Dannenberg, Germany, Folkkampanjen mot Kärnkraft-Kärnvapen, Sweden

This report is sponsored by: the Greens in the European Parliament


The author would like to thank Mali Lightfoot, Executive Director of the Helen Caldicott Foundation, for her valuable suggestions and comments.

Jan Willem Storm van Leeuwen, MSc

With this study WISE hopes to contribute to a thorough debate about the best solutions to tackle climate change. Nuclear energy is part of the current global energy system. The question is whether the role of nuclear power should be increased or halted. In order to be able to fruitfully discuss this we should at least know what the contribution of nuclear power could possibly be.


Summary and conclusions (for complete report click on the link  above or go directly to the report on the WISE site which is downloadable)

Starting point

Nuclear power is claimed to be nearly carbon-free and indispensable for mitigating climate change as a result of anthropogenic emissions of greenhouse gases.
Assuming that nuclear power really does not emit carbon dioxide CO2 nor other greenhouse gases (GHGs), how large is the present nuclear mitigation share and how large could it become in the future? Could the term ‘indispensable’ in this context be quantfied? These issues are assessed from a physical point of view, economic aspects are left outside the scope of this assessment.

How large is the present nuclear mitigation share?

The global GHG emissions comprise a number of different gases and sources. Weighted by the global warming potential of the various GHGs 61% of the emissions were caused by CO2 from burning of fossil fuels for energy generation. Nuclear power could displace fossil-fuelled electricity generation, so hypothetically the maximum nuclear mitigation share would be 61% if the global energy supply were to be fully electric and fully nuclear.

In 2014 the nuclear contribution to the global usable energy supply was 1.6% and consequently the nuclear mitigation share was 1.0%.
The International Atomic Energy Agency (IAEA) asserts that the nuclear contribution to the global energy supply was 4.6% in 2014. However, this figure turns out to be based on a thermodynamically inaccurate statistical trick using virtual energy quantities.

How large could the nuclear mitigation to climate change become in the future according to the nuclear industry?

We found no hard figures on this issue, for that reason this study analyses the mitigation consequences of the envisioned developments of global nuclear generating capacity. During the past years the International Atomic Energy Agency and the nuclear industry, represented by the World Nuclear Association (WNA), published numerous scenarios of global nuclear generating capacity in the future, measured in gigawatt- electric GWe. Four recent scenarios are assessed in this study, as these can be considered to be typical of the views within the nuclear industry:

  • IAEA low: the global nuclear capacity remains flat at the current level until 2050.
  • IAEA high: the global nuclear capacity grows to 964 GWe by 2050, nearly three times the current globalcapacity of 333 GWe.
  • WNA low: the global nuclear capacity grows to 1140 GWe by 2060 and to 2062 GWe by 2100.
  • WNA high: the global nuclear capacity grows to 3688 GWe by 2060 and to 11046 GWe by 2100.

The nuclear mitigation share in the four scenarios depends not only on the nuclear generation capacity, but also on the growth rate of the global GHG emissions. The IAEA expects a growth rate of the global energy consumption of 2.0-3.5% per year until 2050. This study assumes that global GHG emissions will grow during the next decades proportionally to global energy consumption: also at 2.0-3.5% per year. Based on this assumption – and still assuming nuclear power is free of CO2 and other GHG emissions (which it is not) – the mitigation shares would be as follows, the high figure at a global growth of 2.0%/yr, the low figure at 3.5%/yr:

• IAEA low: 0.5-0.3% by 2050.


  • IAEA high: 1.4-0.9% by 2050.
  • WNA low: 1.4-0.7% by 2060 and 1.1-0.3% by 2100.
  • WNA high: 4.5-2.4% by 2060 and 6.2-1.8% by 2100.What next after 2050?The IAEA scenarios are provided through 2050. Evidently the nuclear future does not end in 2050. On the contrary it is highly unlikely that the nuclear industry would build 964 GWe of new nuclear capacity by the year 2050 without solid prospects of operating these units for 40-50 years after 2050.
    How does the nuclear industry imagine development after reaching their milestone in 2050?Further growth, leveling off to a constant capacity, or phase-out? Or: let tomorrow take care of itself?What global construction rates would be required?By 2060 nearly all currently operating nuclear power plants (NPPs) will be closed down because they will reach the end of their operational lifetime within that timeframe. The current rate of 3-4 GWe per year is too low to keep the global nuclear capacity flat and consequently the global nuclear capacity is declining. To keep the global nuclear capacity at the current level the construction rate would have to be doubled. The average global construction rates that would be required in the industry scenarios are:

    • IAEA low: 7-8 GWe per year until 2050.
    • IAEA high: 27 GWe/yr until 2050.
    • WNA low: 25 GWe/yr until 2060 and 23 GWe/yr from 2060 until 2100.
    • WNA high: 82 GWe/yr until 2060 and 184 GWe/yr from 2060 until 2100.
      In view of the massive cost overruns and construction delays of new NPPs that have plagued the nuclear industry for decades it is not clear how the required high construction rates could be achieved.How are the prospects of new advanced nuclear technology?The nuclear industry promises the application within a few decades of advanced nuclear systems that would enable mankind to use nuclear power for hundreds to thousands of years. This promise concerns two main classes of closed-cycle reactor systems: uranium-based systems and thorium-based systems:

      • –  uranium-plutonium recycle in conventional reactors, generally light-water reactors (LWRs)
      • –  fast reactors, that are uranium-plutonium breeder reactors
      • –  thorium reactors.
        Because of the complexity of this matter the three options are briefly discussed below, starting with a brief description of a crucial component common to all three systems, reprocessing.ReprocessingA crucial technical component of the advanced reactor systems is the reprocessing of spent fuel, that is the sequence of physical and chemical processes required to separate spent nuclear fuel into a number of fractions: unused uranium, newly formed plutonium, actinides, fission products and other fractions. The reprocessed uranium and plutonium would be used to fabricate new nuclear fuel to be placed into reactors. In case of a thorium-based system the spent fuel would be separated into unused thorium-232, newly formed uranium-233, fission products and other fractions.Reprocessing is a complicated, highly polluting, and very energy-intensive process. Decommissioning and dismantling of a reprocessing plant after it has to be closed down requires massive investments of materials, energy and financial resources and likely will take more than a century of dedicated effort.


U-Pu recycle in LWRs

The first option, uranium-plutonium recycle in conventional reactors (LWRs), relates to the use of plutonium as fissile material in nuclear fuel instead of uranium-235, as in enriched uranium; this kind of fuel is usually called MOX: Mixed OXide fuel. If all spent fuel discharged from the current global nuclear fleet (all conventional reactors except one) were to be reprocessed and the plutonium obtained were to be used in conventional reactors, the global uranium demand would decrease by some 18%.

Physical analysis of U-Pu recycle in LWRs proves that the energy balance of the system is negative, meaning that the system is actually an energy sink instead of an energy source. The main cause of this is the required energy input of reprocessing and of the decommissioning and dismantling of the reprocessing plant at the end of its service life.

Fast reactors: uranium-plutonium breeders

The term ‘fast reactor’ usually refers to the breeder system, a closed-cycle system that would generate (breed) more fissile nuclei from uranium than consumed in the fission process by converting non-fissile uranium-238 nuclei into fissile plutonium nuclei. During the 1980s and 1990s this type of reactor was usually called a ‘breeder’ or ‘fast breeder reactor’ (FBR) but this term has disappeared from the publications of the IAEA and the nuclear industry. Now the breeder concept is part of the so-called Generation IV program. This program also includes other types of fast reactors without a breeding capacity that are not discussed here.

The envisioned breeders would be able to extract 50-100 times more energy from a kilogram of natural uranium than the current conventional reactors, that cannot fission more than about 0.6% of the nuclei in natural uranium. The prefix ‘fast’ refers to the fact that this type of reactors operate with fast neutrons, contrary to the currently operating commercial reactors in which fission occurs by thermal (slow) neutrons.

A breeder (FBR) is not just a reactor but a cyclic system consisting of a fast-neutron nuclear reactor plus a reprocessing plant plus a fuel fabrication plant. Each of the three components of the cycle would have to operate flawlessly and finely tuned to the two other without any interruption. If one component fails in any respect, the whole system fails and breeding is out of question. Operation of the cyclic system is further complicated by the high radioactivity of the materials to be processed, increasing with each following cycle. Four decades of intensive research in several countries and investments of some $100bn, have proven that the breeding cycle is technically unfeasible. The failure to materialize the U-Pu breeder concept can be traced back to fundamental laws of nature, especially the Second Law of thermodynamics. Thermodynamics is the science of energy conversions; it is at the basis of physics, chemistry and biology. From the Second Law follows, among other consequences, that separation processes of mixtures of different substances never go to completion and consequently perfect materials are not possible. Critical in the breeder cycle is the reprocessing of the spent fuel as soon as possible after unloading from the reactor.

Thorium reactors

Thorium is a radioactive metal, more abundant in the Earth’s crust than uranium. The concept of the thorium reactor is based on the conversion by neutron capture of non-fissile thorium-232 into uranium-233, which is as fissile as plutonium-239. Application of thorium-based systems would make nuclear power independent of the uranium supply, according to the promises of the nuclear industry.

The fundamental obstacles that render the U-Pu breeder technically unfeasible apply also to the thorium breeder. Another drawback of the thorium cycle is that a thorium reactor cannot sustain a fission process in combination with breeding uranium-233 from thorium-232, but always would need an external accelerator- driven neutron source, or the addition of extra fissile material, such as plutonium or uranium-235 from conventional reactors.



In the end the breeder concepts, U-Pu as well Th-U, turn out to be based on inherently unfeasible assumptions. Conditio sine qua non for closed-cycle nuclear generating systems is the availability of:

  • perfect materials
  • fail-safe and fool-proof technical systems with perfectly predictable properties across decades
  • perfect separation of strongly radioactive, complex mixtures of numerous different chemical species into 100% pure fractions.None of these conditions is possible, as a consequence of the Second Law of thermodynamics, and for that reason materialization of the breeder concept is inherently unfeasible.
    From this observation it follows that nuclear power in the future would have to rely solely on once-through reactor technology based on natural uranium. As a consequence the size of the uranium resources will be a restricting factor.

Full report includes chapters on:

  • How much uranium would be needed to sustain the various scenario’s? (Pg 7)
  • How are the prospects of the global uranium supply? (Pg 7)
  • What are the thermodynamic boundaries of uranium-for-energy resources? (Pg 8)
  • How much CO2 does nuclear power emit? (Pg 8)
  • Does nuclear power also emit other greenhouse gases? (Pg 9)
  • Does nuclear power emit other climate changing gases? (Pg 9)
  • Are the published nuclear GHG emission figures comparable to renewables? (Pg 9)
  • What is the energy debt and what are the delayed CO2 emissions of nuclear power? (Pg 10)
  • What consequences of the energy debt could be expected? (Pg 10)
  • How independent is the information supply to the public on nuclear matters? (Pg 11)
  • Are releases of radioactive materials into the human environment really of minor importance? (Pg 11)
  • Conclusions (Pg 12)
  • Contents (Pg 13-15)


Summary and conclusions


  1. 1  Global context of nuclear powerGlobal greenhouse gas emissions World gross energy supply Thermodynamic inaccuracies InconsistenciesFinal energy use
    Nuclear contribution to GHG emission mitigation in 2010
  2. 2  Nuclear CO2 mitigation scenario’sPresent state
    Scenario 0, phase-out
    Scenario 1, constant nuclear capacity, IAEA low Scenarios 2 and 3, constant mitigation share Scenario 4, IAEA highScenarios 5 and 6, WNA scenario’s Overview
    Scenarios after 2050 or 2060? Construction ratesHealth hazards
  3. 3  Thermodynamics of closed-cycle nuclear systemsAdvanced nuclear technology Reprocessing of spent fuel U-Pu recycle in LWRs
    Risks of nuclear terrorism Fast reactorsThorium Conclusion
  4. 4  Uranium supplyConventional uranium resources Unconventional uranium resources Economics and uranium resources Thermodynamic boundaries
  5. 5  Nuclear power and thermodynamicsWhy a thermodynamic analysis?
    Energy costs energy
    Nuclear process chain
    Back end of the nuclear process chain as it ought to be Materials consumed by the nuclear energy system Origin of the nuclear CO2 emission


Energy analysis
Thermodynamic quality of uranium resources
Energy cliff
Depletion of uranium resources: a thermodynamic notion CO2 trap

  1. 6  Energy debt and delayed CO2 emissionsDynamic energy balance of nuclear power Energy debt
    Delayed CO2 emissions
    MisconceptionFinancial debt
    View of the nuclear industry
    Questionable assumptions
    Après nous le déluge
    Economic preferences and nuclear security
  2. 7  Other greenhouse gasesGlobal warming potential
    Fluorine consumption in the nuclear process chain
    Chlorine use for fuel fabrication
    Nuclear emission of non-CO2 greenhouse gases: a well-kept secret False comparison
    Krypton-85, another nuclear climate changer
    Health hazards of krypton-85

Acronyms and physical units



Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7

Energy actually produced in 2010
Summary of nuclear capacity scenarios
Summary of capacity, uranium usage and total uranium demand Identified conventional uranium resources
Summary of total uranium demand and mitigation shares
Contributions to the specific CO2 emission of the nuclear energy system Greenhouse gases



Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25

Outline of the assesment
Global greenhouse gas emissions
Actual global gross energy production in 2010
Virtual energy units added to real energy units by nuclear industry Physical energy flows of the world in 2010
Global greenhouse gas emissions by gas and source
Nuclear share of world energy production in 2010
Scenarios of global nuclear generating capacity
Scenarios 1,2 and 4 extended to 2100, variant 1
Scenarios 1,2 and 4 extended to 2100, variant 2
Maximum nuclear mitigation contribution by 2050-2060
Outline of the radioactive mass flows of reprocessing of spent fuel Economic model of availability of mineral resources
Economic model of availability of uranium resources
Simple outline of the nuclear process chain
Full process chain of a LWR in once-through mode
Lifetime material flows of the complete nuclear energy system
Material balances of nuclear power and wind power systems Contributions to the specific CO2 emission of the nuclear energy system Specific nuclear CO2 emission as function of the uranium ore grade Energy cliff of the nuclear system
Depletion of currently known uranium resources
CO2 trap over time
Dynamic energy balance of the nuclear energy system
Delayed nuclear CO2 emissions

  • Introduction (Pgs 16-17)
  • Global Context of Nuclear Power (begins Pg 18)

Read full report at WISE PDF link:


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