Nuclear power: No Solution to Climate Change

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SUMMARY

1. Nuclear Power is Not a Silver Bullet

Nuclear power could at most make a modest contribution to climate change abatement. The main limitation is that it is used almost exclusively for electricity generation, which accounts for less than 25% of global greenhouse emissions. Even tripling nuclear power generation would reduce emissions by less than 10% − and then only if the assumption is that it displaces coal.

2. Greenhouse Emissions from the Nuclear Fuel Cycle

Claims that nuclear power is 'greenhouse free' are false. Nuclear power is more greenhouse intensive than most renewable energy sources and energy efficiency measures. Life-cycle greenhouse emissions from nuclear power will increase as relatively high-grade uranium ores are mined out.

3. Nuclear Power – A Slow Response to an Urgent Problem

The nuclear industry does not have the capacity to rapidly expand production as a result of 20 years of stagnation. Limitations include bottlenecks in the reactor manufacturing sector, dwindling and ageing workforces, and the considerable time it takes to build a reactor and to pay back the energy debt from construction.

4. Nuclear Power and Climate Change

Countries and regions with a high reliance on nuclear power also tend to have high greenhouse gas emissions.

Some countries are planning to replace fossil fuel-fired power plants with nuclear power in order to increase fossil fuel exports − in such cases any potential climate change mitigation benefits of nuclear power are lost.

5. Climate Change and Nuclear Hazards

Nuclear power plants are vulnerable to threats which are being exacerbated by climate change. These include dwindling and warming water sources, sea-level rise, storm damage, drought, and jelly-fish swarms.

'Water wars' − in particular, disputes over the allocation of increasingly scarce water resources between power generation and agriculture − are becoming increasingly common and are being exacerbated by climate change

6. Weapons Proliferation and Nuclear Winter

Civil nuclear programs have provided cover for numerous covert weapons programs and an expansion of nuclear power would exacerbate the problem.

Nuclear warfare − even a limited nuclear war involving a tiny fraction of the global arsenal − has the potential to cause catastrophic climate change.

7. Renewables and Energy Efficiency

Global renewable power capacity more than doubled from 2004 to 2014 (and non-hydro renewables grew 8-fold). Over that decade, and the one before it, nuclear power flatlined.

Global renewable capacity (including hydro) is 4.6 times greater than nuclear capacity, and renewable electricity generation more than doubles nuclear generation. A growing body of research demonstrates the potential for renewables to largely supplant fossil fuels for power supply globally.

Energy efficiency and renewables are the Twin Pillars of a clean energy future. A University of Cambridge study concluded that 73% of global energy use could be saved by energy efficiency and conservation measures − making it far easier to achieve a low-carbon, non-nuclear future.

1. NUCLEAR POWER IS NOT A SILVER BULLET

"Saying that nuclear power can solve global warming by itself is way over the top".

-- Senior International Atomic Energy Agency energy analyst Alan McDonald, 2004.[1]

Nuclear power could at most make a modest contribution to climate change abatement. The main limitation is that it is used almost exclusively for electricity generation, which accounts for less than 25% of global (anthropogenic) greenhouse emissions.[2]

Doubling current nuclear capacity would reduce emissions by roughly 6% if nuclear displaced coal[3] − or not at all if nuclear displaced renewables and energy efficiency. Doubling nuclear power generation would require building 437 reactors to add to the 437 existing 'operable' reactors (380 gigawatts). It would also require new reactors to replace shut-down reactors − the International Energy Agency anticipates almost 200 shut downs by 2040.[4]

A 2007 report by the International Panel on Fissile Materials (IPFM) states that if nuclear power grew approximately three-fold to about 1000 GWe in 2050, the increase in global greenhouse emissions projected in business-as-usual scenarios could be reduced by about 10−20% − assuming that nuclear displaced coal.^[5] The IPFM scenario (which it does not advocate) assumes a business-as-usual doubling of greenhouse emissions by 2050, with 700 additional reactors reducing emissions from 14 billion metric tons to 13 billion metric tons. Thus the increase in emissions would be reduced by 1/7 or 14% and overall emissions would be reduced by 1/14 or 7% − assuming that nuclear displaces coal.

According to a 2007 article in Progress in Nuclear Energy, a ten-fold increase in nuclear capacity by the end of the century would reduce greenhouse emissions by 15%.[6]

Clearly, nuclear power is not a 'silver bullet'.

2. GREENHOUSE EMISSIONS FROM THE NUCLEAR FUEL CYCLE

Claims that nuclear power is 'greenhouse free' are false. Nuclear power is more greenhouse intensive than most renewable energy sources and energy efficiency measures. Life-cycle greenhouse emissions from nuclear power will increase as relatively high-grade uranium ores are mined out and give way to the mining of lower-grade ores.

Greenhouse emissions arise across the nuclear fuel cycle – uranium mining, milling, conversion, and enrichment; reactor construction, refurbishment and decommissioning; waste management (e.g. reprocessing, and/or encasement in glass or cement); and transportation of uranium, spent fuel, etc.

Academic Benjamin Sovacool wrote in a 2008 paper:

"To provide just a rough estimate of how much equivalent carbon dioxide nuclear plants emit over the course of their lifecycle, a 1,000 MW reactor operating at a 90 percent capacity factor will emit the equivalent of 1,427 tons of carbon dioxide every day, or 522,323 metric tons of carbon dioxide every year. Nuclear facilities were responsible for emitting the equivalent of some 183 million metric tons of carbon dioxide in 2005. Assuming a carbon tax of $24 per ton − nothing too extreme − and that 1,000 MW nuclear plant would have to pay almost $12.6 million per year for its carbon-equivalent emissions. For the global nuclear power industry, this equates to approximately $4.4 billion in carbon taxes per year."[7]

In a ground-breaking study Sovacool screened 103 lifecycle studies of greenhouse emissions from the nuclear fuel cycle to identify the most current, original, and transparent studies.[8] He found that the mean value from those studies was 66 grams of carbon dioxide equivalent per kilowatt-hour (gCO2e/kWh).

Sovacool's paper provides the following figures (gCO2e/kWh):

Wind	9−10
Hydro	10−13
Biogas	11
Solar thermal	13
Biomass	14−31
Solar PV	32
Biomass	35−41
Geothermal	38
Nuclear	66
Natural gas	443
Diesel	778
Heavy oil	778
Coal	960−1050

Sovacool states: "Offshore wind power has less than one-seventh the carbon equivalent emissions of nuclear plants; large-scale hydropower, onshore wind, and biogas, about one-sixth the emissions; small-scale hydroelectric and solar thermal one-fifth. This makes these renewable energy technologies seven-, six-, and five-times more effective on a per kWh basis at fighting climate change. Policymakers would be wise to embrace these more environmentally friendly technologies if they are serious about producing electricity and mitigating climate change."[9]

In a 2009 paper prepared for the Australian Uranium Association, academic Manfred Lenzen concluded that life-cycle greenhouse emissions for nuclear power range from 10−130 gCO2e/kWh with the main variables being ore grades, enrichment technology, reactor fuel re-load frequency and burn-up, and to a lesser extent enrichment level, plant lifetime, load factors, and enrichment tails assay. Lenzen calculates a "worst case" – 0.01% ore grade, 75% load factor, 25 year lifetime, only diffusion enrichment, and a carbon-intensive background economy – resulting in emissions of 248 gCO2e/kWh.[10]

Others calculate still higher values, for example by assuming energy- and emissions-intensive burial of large volumes of low-level ore, waste rock, and mill tailings, rather than the current practice of surface storage.

Life-cycle greenhouse emissions from nuclear power will increase as relatively high-grade uranium ores are mined out. In 2009, mining consultancy firm CRU Group calculated that the average grade of uranium projects at the feasibility study stage around the world was 35% lower than the grades of operating mines, and that exploration projects had average grades 60% below existing operations.[11]

The extent of the increase in the greenhouse intensity of uranium mining is the subject of debate and considerable uncertainty. It depends not only on declining ore grades but also on other variables such as the choice of tailings management options at uranium mines.

Writing in the Journal of Industrial Ecology in 2012, Warner and Heath stated that emissions from the nuclear fuel cycle could increase by 55−220% with declining uranium ore grades.[12]

Academic Dr Mark Diesendorf states: "In the case where high-grade uranium ore is used, CO2 emissions from the nuclear fuel cycle are much less than those of an equivalent gas-fired power station. But the world's reserves of high-grade uranium are very limited and may only last a few decades. The vast majority of the world's uranium is low-grade. CO2 emissions from mining, milling and enrichment of low-grade uranium are substantial, and so total CO2 emissions from the nuclear fuel cycle become greater than or equal to those of a gas-fired power station."[13]

Keith Barnham, Emeritus Professor of Physics at Imperial College London, states that for ore with uranium concentration around 0.01%, the carbon footprint of nuclear electricity could be as high as that of electricity generation from natural gas.[14]

The German Environment Ministry stated in a 2006 report that a modern gas-fired power station in connection with heat production (co-generation) could be less carbon intensive than nuclear power.[15]

Some nuclear lobbyists claim that Generation IV fast neutron reactors would reduce emissions from the nuclear fuel cycle by using waste products (esp. depleted uranium and spent fuel) as fuel instead of mined uranium. One of the problems with that arguments is that Generation IV reactors are − and always have been − decades away:

• The Generation IV International Forum states: "Depending on their respective degree of technical maturity, the first Generation IV systems are expected to be deployed commercially around 2030−2040."[16]
• The International Atomic Energy Agency states: "Experts expect that the first Generation IV fast reactor demonstration plants and prototypes will be in operation by 2030 to 2040."[17]
• A 2015 report by the French government's Institute for Radiological Protection and Nuclear Safety states: "There is still much R&D to be done to develop the Generation IV nuclear reactors, as well as for the fuel cycle and the associated waste management which depends on the system chosen."[18]
• The World Nuclear Association noted in 2009 that "progress is seen as slow, and several potential designs have been undergoing evaluation on paper for many years."[19]

As for the real-world experience with fast neutron reactors, for the most part they have failed every test including carbon intensity. White elephants such as Japan's Monju reactor and France's Superphenix produced so little electricity that the carbon intensity must have been high. Monju operated for 205 days after it was connected to the grid in August 1995, and a further 45 days in 2010; apart from that it has been shut-down because of a sodium leak and fire in 1996, and a 2010 accident when a 3.3 tonne refuelling machine fell into the reactor vessel.[20] The lifetime load factor of the French Superphenix fast reactor − the ratio of electricity generated compared to the amount that would have been generated if operated continually at full capacity − was just 7% percent, making it one of the worst-performing reactors in history.[21]

3. NUCLEAR POWER – A SLOW RESPONSE TO AN URGENT PROBLEM

Expanding nuclear power is impractical as a short-term response to the need to urgently reduce greenhouse emissions. The industry does not have the capacity to rapidly expand production as a result of 20 years of stagnation. Limitations include bottlenecks in the reactor manufacturing sector, dwindling and ageing workforces, and the considerable time it takes to build a reactor and to pay back the energy debt from construction.

One constraint is the considerable time it takes to build reactors. The World Nuclear Industry Status Report 2014 noted that the average construction time of the last 37 reactors that started up was 10 years; and that at least 49 of the 67 reactors listed as under construction have encountered construction delays.[22]

The development of new reactor types − even those which are just modified versions of conventional reactor technology − further delays the construction and deployment of nuclear power. For example the EPR in Finland is 7−9 years behind schedule, and the EPR in France is five years behind schedule (and counting).[23]

Nuclear power is still slower for countries building their first reactor. The IAEA sets out a phased 'milestone' approach to establishing nuclear power in new countries, lasting from 11−20 years: a pre-project phase 1 (1−3 years), a project decision-making phase (3−7 years) and a construction phase (7−10 years).[24]

The French Nuclear Safety Authority (ASN) says that the initial development of a nuclear power industry requires at least 10−15 years in order to build up skills in safety and control and to develop a regulatory framework − that's 10−15 years even before reactor construction begins. Even with rapid progress, ASN estimates a minimum lead time of 15 years before a new nuclear power plant can be started up in a country that does not already have the required infrastructure.²⁴

In addition to reactor construction, further years elapse before nuclear power has generated as much as energy as was expended in the construction of the reactor. One academic report states: "The energy payback time of nuclear energy is around 6½ years for light water reactors, and 7 years for heavy water reactors, ranging within 5.6–14.1 years, and 6.4–12.4 years, respectively."[25]

By contrast, construction times for renewable energy sources are typically months not years, and likewise the energy pay-back period is typically months not years.

Another constraint is bottlenecks in the reactor manufacturing sector. Sharon Squassoni noted in a 2009 paper:

"A significant expansion will narrow bottlenecks in the global supply chain, which today include ultra-heavy forgings, large manufactured components, engineering, and craft and skilled construction labor. All these constraints are exacerbated by the lack of recent experience in construction and by aging labor forces. Though these may not present problems for limited growth, they will certainly present problems for doubling or tripling reactor capacity."[26]

Another constraint is the pattern of ageing nuclear workforces − the 'silver tsunami'.[27] In the UK, for example, a recent government report says that attrition rates in the ageing nuclear workforce are "high and growing" with more than 8,000 new employees a year needed every year for the next six years if the country's ambitious new-build programme is to succeed.[28] In addition, research and training facilities and courses have been on the decline.

A major expansion of nuclear power is theoretically possible over the medium- to long-term. The depletion of uranium resources could be a constraint. According to the World Nuclear Association, the world's present measured resources of uranium (5.9 Mt) in the cost category around 1.5 times present spot prices, are enough to last for about 90 years at the current usage rate of 66,000 tU/yr.[29]

4. NUCLEAR POWER AND CLIMATE CHANGE

Countries and regions with a high reliance on nuclear power also tend to have high greenhouse gas emissions. For example, the US operates 99 power reactors with a capacity of 98.8 GW (26% of the world total), with nuclear power generating over 19% of its electricity. Yet the US is one of the world's largest greenhouse polluters both in per capita and overall terms.

Some countries are planning to replace fossil fuel-fired power plants with nuclear power in order to increase fossil fuel exports. In such cases any potential climate change mitigation benefits of nuclear power are lost. World Nuclear News reported in 2010 that Venezuela, Russia, and some Middle East countries such as the UAE and Iran would prefer to export oil and gas rather than use them in domestic power plants.[30] Saudi Arabia is another country planning to build nuclear power plants in order to boost fossil fuel exports.[31]

5. CLIMATE CHANGE AND NUCLEAR HAZARDS

Nuclear power plants are vulnerable to threats which are being exacerbated by climate change − discussed in detail in Nuclear Monitor #770.[32]

A 2013 report by the US Department of Energy details many of the interconnections between climate change and energy.[33] These include:

• Increasing risk of shutdowns at thermoelectric power plants (e.g. coal, gas and nuclear) due to decreased water availability which affects cooling, a requirement for operation;
• Higher risks to energy infrastructure located along the coasts due to sea level rise, the increasing intensity of storms, and higher storm surge and flooding;
• Disruption of fuel supplies during severe storms;
• Power plant disruptions due to drought; and
• Power lines, transformers and electricity distribution systems face increasing risks of physical damage from the hurricanes, storms and wildfires that are growing more frequent and intense.

At the lower end of the risk spectrum, there are many instances of nuclear plants operating at reduced power or being temporarily shut down due to water shortages or increased water temperature (which can adversely affect reactor cooling and/or cause fish deaths and other problems with the dumping of waste heat in water sources). Reactors in several countries have been forced to close during heat waves, when they're needed the most. For example, France had to purchase power from the UK in 2009 because almost a third of its nuclear generating capacity was lost when it had to cut production to avoid exceeding thermal discharge limits.[34]

At the upper end of the risk spectrum, climate-related threats pose serious risks, such as storms cutting off grid power, leaving nuclear plants reliant on generators for reactor cooling. A 2004 incident in Germany illustrates the risks. Both Biblis reactors (A and B) were in operation when heavy storms knocked out power lines. Because of an incorrectly set electrical switch and a faulty pressure gauge, the Biblis-B turbine did not drop, as designed, from 1,300 to 60 megawatts. Instead the reactor scrammed. When Biblis-B scrammed with its grid power supply already cut off, four emergency diesel generators started. Another emergency supply also started but, because of a switching failure, one of the lines failed to connect. These lines would have been relied upon as a backup to bring emergency power from Biblis-B to Biblis-A if Biblis-A had also been without power. The result was a partial disabling of the emergency power supply from Biblis-B to Biblis-A for about two hours.[35]

'Water wars' will become increasingly common with climate change − in particular, disputes over the allocation of increasingly scarce water resources between power generation and agriculture. Nuclear power reactors consume massive amounts of water − typically 36.3 to 65.4 million litres per reactor per day − primarily for reactor cooling.[36]

Jellyfish swarms have caused problems at many nuclear plants around the world.[37] Increased fishing of jellyfish predators and global warming are contributing to higher jellyfish populations. Monty Graham, co-author of a study on jellyfish blooms published in the Proceedings of the National Academy of Sciences, blames global warming, overfishing, and the nitrification of oceans through fertiliser run-off.[38]

The Union of Concerned Scientists argued in a 2013 report:

"Low-carbon power is not necessarily water-smart. Electricity mixes that emphasise carbon capture and storage for coal plants, nuclear energy, or even water-cooled renewables such as some geothermal, biomass, or concentrating solar could worsen rather than lessen the sector's effects on water. That said, renewables and energy efficiency can be a winning combination. This scenario would be most effective in reducing carbon emissions, pressure on water resources, and electricity bills. Energy efficiency efforts could more than meet growth in demand for electricity in the US, and renewable energy could supply 80% of the remaining demand."[39]

The REN21 'Renewables 2015: Global Status Report' states:[40]

"All energy systems are susceptible to climate variability and extremes. For example, decreasing water levels and droughts can lead to the shutdown of thermal power plants that depend on water-based cooling systems. Dry periods, alternating with floods, can shift erosion and deposition patterns, altering growth rates of biomass and affecting the quality and quantity of the potential fuel output. The melting of glaciers, induced by temperature increases, can have a negative effect on hydropower systems by causing infrastructure damage from flooding and siltation, as well as affecting generation capacity. The efficiency of solar PV declines with high temperatures and dust accumulation, and most of today's wind turbines shut down in winds exceeding 100 to 120 kilometres per hour.

"Typical responses to reducing system vulnerability involve reinforcing existing infrastructure (including strengthening transmission towers and lines); ensuring redundancy of critical systems; building seawalls around power plants; reducing the need for power plant cooling water; and storing larger quantities of fuel at plants. More innovative strategies include local generation and storage, diversification of energy sources, use of a combination of smart grids and technologies, and improving capabilities to couple and decouple individual systems from the central grid system during emergencies.

"Although renewable energy systems are also vulnerable to climate change, they have unique qualities that make them suitable both for reinforcing the resilience of the wider energy infrastructure and for ensuring the provision of energy services under changing climatic conditions. System modularity, distributed deployment, and local availability and diversity of fuel sources − central components of energy system resilience − are key characteristics of most renewable energy systems. Ultimately, renewable energy systems improve the resilience of conventional power systems, both individually and by their collective contribution to a more diversified and distributed asset pool."

6. WEAPONS PROLIFERATION AND NUCLEAR WINTER

Global expansion of nuclear power would inevitably involve the growth and spread of stockpiles of weapons-useable fissile material and the facilities to produce fissile materials (enrichment plants for highly enriched uranium; and reactors and reprocessing plants for plutonium). Global expansion of nuclear power would lead to an increase in the number of 'threshold' or 'breakout' nuclear states which could quickly produce weapons drawing on expertise, facilities and materials from their 'civil' nuclear program.

Former US Vice President Al Gore has neatly summed up the problem: "For eight years in the White House, every weapons-proliferation problem we dealt with was connected to a civilian reactor program. And if we ever got to the point where we wanted to use nuclear reactors to back out a lot of coal ... then we'd have to put them in so many places we'd run that proliferation risk right off the reasonability scale."[41]

Running the proliferation risk off the reasonability scale brings the debate back to climate change − a connection explained by Alan Robock in The Bulletin of the Atomic Scientists:

"As recent work ... has shown, we now understand that the atmospheric effects of a nuclear war would last for at least a decade − more than proving the nuclear winter theory of the 1980s correct. By our calculations, a regional nuclear war between India and Pakistan using less than 0.3% of the current global arsenal would produce climate change unprecedented in recorded human history and global ozone depletion equal in size to the current hole in the ozone, only spread out globally."[42]

Nuclear expansion would also increase the availability of nuclear materials for radioactive 'dirty bombs'. It would also increase the number of potential targets for terrorist attacks or conventional military strikes by nation-states (such as the repeated military strikes and attempted strikes on nuclear sites in the Middle East).

The US National Intelligence Council argued in a 2008 report that the "spread of nuclear technologies and expertise is generating concerns about the potential emergence of new nuclear weapon states and the acquisition of nuclear materials by terrorist groups."[43]

As long ago as 1946, the Acheson-Lilienthal Report commissioned by the US Department of State identified intractable problems:

"We have concluded unanimously that there is no prospect of security against atomic warfare in a system of international agreements to outlaw such weapons controlled only by a system which relies on inspection and similar police-like methods. The reasons supporting this conclusion are not merely technical, but primarily the inseparable political, social, and organizational problems involved in enforcing agreements between nations each free to develop atomic energy but only pledged not to use it for bombs. National rivalries in the development of atomic energy readily convertible to destructive purposes are the heart of the difficulty."[44]

Fissile materials

A May 2015 report written by Zia Mian and Alexander Glaser for the International Panel on Fissile Materials provides details on stockpiles of fissile materials. As of the end of 2013, civilian stockpiles contained 57,070 weapon-equivalents: 61 tons of highly enriched uranium (4,070 weapons), and 267 tons of (separated) plutonium (53,000 weapons).[45] The figures are far greater if plutonium in spent fuel is included.

Harold Feiveson calculates that with an increase in nuclear power capacity to 3,500 GW (compared to 380 GW as of June 2015), about 700 tonnes of plutonium would be produced annually.[46] That amount of plutonium would suffice to build 70,000 nuclear weapons, and if we assume an average 40-year reactor lifespan the accumulated plutonium would suffice to build 2.8 million weapons.

Similarly, the Intergovernmental Panel on Climate Change maps out a scenario whereby nuclear capacity would grow to about 3,300 gigawatts in 2100 and the accumulated plutonium inventory would rise to 50-100 thousand tonnes (IPCC, 1995). That amount of plutonium would suffice to build 5−10 million nuclear weapons.[47]

The challenge is still greater as a result of the practice of plutonium stockpiling. Japan's plutonium stockpiling, for example, clearly fans proliferation risks and tensions in north-east Asia. Diplomatic cables in 1993 and 1994 from US Ambassadors in Tokyo questioned the rationale for the stockpiling of so much plutonium. A 1993 US diplomatic cable posed these questions: "Can Japan expect that if it embarks on a massive plutonium recycling program that Korea and other nations would not press ahead with reprocessing programs? Would not the perception of Japan's being awash in plutonium and possessing leading edge rocket technology create anxiety in the region?"[48]

A 2007 report by the International Panel on Fissile Materials (IPFM) states:

"Even a modest expansion of nuclear power would be accompanied by a substantial increase in the number of countries with nuclear reactors. Some of these countries would likely seek gas-centrifuge uranium-enrichment plants as well. Centrifuge-enrichment plants can be quickly converted to the production of highly enriched uranium for weapons. It is therefore critical to find multinational alternatives to the proliferation of national enrichment plants.

"If a large-scale expansion of nuclear power were accompanied by a shift to reprocessing and plutonium recycle in light-water or fast reactors, it would involve annual flows of separated plutonium on the scale of a thousand metric tons per year − enough for 100,000 nuclear bombs." [49]

7. RENEWABLES AND ENERGY EFFICIENCY

The REN21 'Renewables 2015: Global Status Report' details the striking growth of renewables over the past decade.[50] Renewable energy provided an estimated 19.1% of global final energy consumption in 2013, and growth in capacity and generation continued to expand in 2014. Heating capacity grew at a steady pace, and the production of biofuels for transport increased.

The most rapid growth, and the largest increase in capacity, occurred in the power sector, led by wind, solar PV, and hydropower. Renewables accounted for approximately 59% of net additions to global power capacity in 2014, with significant growth in all regions of the world.

Global renewable power capacity − excluding hydro − grew eight-fold from 85 GW in 2004 to 657 GW in 2014. Solar PV capacity has grown at a phenomenal rate, from 2.6 GW in 2004 to 177 GW in 2014. Over the same period wind power capacity increased from 48 GW to 370 GW.

Global renewable power capacity − including hydro − more than doubled from 800 GW in 2004 to 1,712 GW in 2014 (an estimated 27.7% of the world's power generating capacity in 2014).

In 2014, total installed renewable capacity (including hydro) increased by 8.5%, compared to 0.6% for nuclear power. Hydro capacity rose by 3.6% while other renewables collectively grew nearly 18%.

By way of sharp contrast, nuclear power has flatlined for the past two decades. Nuclear power capacity was 365 GW in 2004 and 376 GW in 2014, and the number of reactors declined from 443 to 439 over that period.[51]

Renewable capacity (including hydro) of 1,712 GW is 4.6 times greater than nuclear capacity of 376 GW.

But the capacity factor of some renewables (e.g. solar PV and wind) is lower than that of nuclear power, so how do the figures stack up when comparing electricity generation? The REN21 report states that as of the end of 2014, renewables (including hydro) supplied an estimated 22.8% of global electricity (hydro 16.6% and other renewables 6.2%). Nuclear power's share of 10.8%[52] is less than half of the electricity generation from renewables − and the gap is widening.

Renewables jobs have also increased dramatically, with more than 7.7 million people now employed in the sector worldwide.

The REN21 report notes that the growth of renewables is being driven by declining costs and that "in many countries renewables are broadly competitive with conventional energy sources." Further, "growth in renewable energy (and energy
efficiency improvements) continues to be tempered by subsidies to fossil fuels and nuclear power, particularly in developing countries."

One final point from the REN21 report warrants mention. The report states: "Despite rising energy use, for the first time in four decades, global carbon emissions associated with energy consumption remained stable in 2014 while the global economy grew; this stabilisation has been attributed to increased penetration of renewable energy and to improvements in energy efficiency."

Deep cuts

Renewables are leaving nuclear power in their wake. But is the growth trajectory of renewables commensurate with the deep cuts in greenhouse emissions required to avert climate change? The short answer is: no.

Could renewables largely supplant fossil fuelled power plants if there was the political will to make the transition happen? Or is an 'all of the above' approach including renewables and nuclear necessary? There is a growing body of research on the potential for renewables to largely or completely supplant fossil fuels for power supply globally.[53]

Of particular interest are:

• countries with a large number of reactors − only France (58) and the US (99) have more than 50 power reactors;
• countries with a very heavy reliance on nuclear power (e.g. nuclear supplies around 75% of France's electricity); and
• countries with very large and growing populations and increasing energy demand (e.g. India and China).

USA: The Nuclear Information & Resource Service maintains a list of reports demonstrating the potential for the US (and Europe) to produce all electricity from renewables.[54]

France: A recent report by ADEME, a French government agency under the Ministries of Ecology and Research, shows that a 100% renewable electricity supply by 2050 in France is feasible and affordable.[55] For an all-renewables scenario, the report proposes an ideal electricity mix: 63% from wind, 17% from solar, 13% from hydro and 7% from renewable thermal sources (including geothermal energy). The report estimates that the electricity production cost (currently averaging 91 euros per MWh) would be 119 euros per megawatt-hour in the all-renewables scenario, compared with a near-identical figure of 117 euros per MWh with a mix of 50% nuclear, 40% renewables, and 10% fossil fuels.

China: A 2015 report by the China National Renewable Energy Centre finds that China could generate 85% of its electricity and 60% of total energy from renewables by 2050.[56]

India: A detailed 2013 report by WWF-India and The Energy and Resources Institute maps out how India could generate as much as 90% of total primary energy from renewables by 2050.[57] The study develops and evaluates a potential growth path involving large deployment of renewables − especially solar, wind and hydro − for electricity generation, with second-generation and algal biofuels meeting the additional demands of the transport sector. It argues that aggressive efficiency improvements also have large potential and could bring in savings of the order of 59% by 2050.

Twin Pillars: Energy efficiency and renewables

A June 2015 report by the International Energy Agency (IEA) compares an 'INDC' scenario, based on 'Intended Nationally Determined Contributions' nominated by (some) countries in advance of the UN climate conference in December 2015, with a more ambitious 'Bridge Scenario'.[58] Energy efficiency does much of the heavy lifting in reducing energy-related greenhouse emissions in the Bridge Scenario compared to the INDC scenario. Energy efficiency accounts for 49% of the reduction by 2030, renewables 17%, upstream methane reductions 15%, fossil-fuel subsidy reform 10%, and reducing inefficient coal 9%.[59]

The IEA report's comments on renewables are worth noting. In the Bridge Scenario, 60% of new power capacity between 2015 and 2030 comes from renewables (23% wind, 17% solar PV, 14% hydro, 6% other renewables) compared to just 6% for nuclear, with fossil fuels accounting for the remaining 34%.[60] In the Bridge Scenario, nuclear accounts for 13% of global power capacity in 2030, almost three times lower than renewables' share of 37% (hydro 18%, wind 9%, solar PV, 4%, bioenergy 4%, geothermal 1%, and concentrated solar power 1%).

In the scenario presented in the International Energy Agency's 'World Energy Outlook 2014', which envisages modest efforts to reduce emissions, oil demand in 2040 would be 22% higher without the cumulative impact of energy efficiency measures, gas demand 17% higher and coal demand 15% higher.[61] The report states: "Beyond cutting energy use, energy efficiency lowers energy bills, improves trade balances and cuts CO2 emissions. Improved energy efficiency compared with today reduces oil and gas import bills for the five largest energy-importing regions by almost $1 trillion in 2040."

The REN21 report notes that renewables and energy efficiency are twin pillars of a sustainable energy future − enabling applications that otherwise might not be technically or economically practical and rendering the outcome greater than the sum of the parts. The report provides examples of the synergies:

• Synergies for greater system benefits: Efficient building systems and designs, combined with on-site renewable energy generation, reduce end-use energy demand, electrical grid congestion and losses, and the monetary and energy expenditures associated with fuel transportation.
• Synergies for greater renewable energy share in the energy mix. Improving end-use efficiency and increasing use of on-site renewables reduce primary energy demand. With lower end-use energy requirements, the opportunity increases for renewable energy sources of low energy density to meet full energy-service needs. Targets to increase the share of renewables in total energy consumption can be achieved through both increasing the amount of renewable energy and reducing total energy consumption.
• Synergies for greater investment in renewables and efficiency. Improvements in end-use energy efficiency reduce the cost of delivering end-use services by renewable energy, and the money saved through efficiency can help finance additional efficiency improvements and/or deployment of renewable energy technologies. These synergies exist across numerous sectors, from buildings and electrical services to transportation and industry.

A 2011 study by University of Cambridge academics concluded that a whopping 73% of global energy use could be saved by practically achievable energy efficiency and conservation measures.[62] Julian Allwood, one of the authors of the study, said: "We think it's pretty unlikely that we'll find a good response to the threat of global warming on the supply side alone. But if we can make a serious reduction in our demand for energy, then all the options look more realistic."[63]