Nuclear power proposed as renewable energy

Although nuclear power is considered a low carbon power generation source,^[1] its legal inclusion with renewable energy power sources has been a subject of debate and classification. Statutory definitions of renewable energy usually exclude many present nuclear energy technologies, with notable exceptions in the states of Utah,^[2] and Arizona in the United States,^[3] where only a particular implementation of nuclear fission with "waste"/fuel recycling meets the state's criteria.^[4] Dictionary sourced definitions of renewable energy technologies often omit or explicitly exclude mention to every nuclear energy source, with an exception made for the natural nuclear decay heat generated within the Earth/geothermal energy.^[5][6]

The most common fuel used in conventional nuclear fission power stations, uranium-235 is "non-renewable" according to the Energy Information Administration, the organization however is silent on the recycled fuel of MOX.^[6] Similarly, the National Renewable Energy Laboratory does not mention nuclear power in its "energy basics" definition.^[7]

In 1987, the World Commission on Environment and Development (WCED) classified fission reactors that produce more fissile nuclear fuel than they consume (breeder reactors, and if developed, fusion power) among conventional renewable energy sources, such as solar and falling water.^[8] The American Petroleum Institute likewise does not consider conventional nuclear fission as renewable, but that breeder reactor nuclear fuel is considered renewable and sustainable, and while conventional fission leads to waste streams that remain a concern for millennia, the waste from efficiently burnt up spent fuel requires storage for no more than a thousand years.^[9][10][11] The monitoring and storage of radioactive waste products is also required upon the use of other renewable energy sources, such as geothermal energy.^[12]

Definitions of renewable energy

Renewable energy flows involve natural phenomena, which with the exception of tidal power, ultimately derive their energy from the sun(a natural fusion reactor) or from geothermal energy, which is heat derived in greatest part from that which is generated in the earth from the decay of radioactive isotopes, as the International Energy Agency explains:^[13]

Renewable energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly from the sun, or from heat generated deep within the earth. Included in the definition is electricity and heat generated from sunlight, wind, oceans, hydropower, biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources.

Renewable energy resources exist over wide geographical areas, in contrast to other energy sources, which are concentrated in a limited number of countries.^[13]

In ISO 13602-1:2002, a renewable resource is defined as "a natural resource for which the ratio of the creation of the natural resource to the output of that resource from nature to the technosphere is equal to or greater than one".

Conventional fission, breeder reactors as renewable

Nuclear fission reactors are a natural energy phenomenon, having naturally formed on earth in times past, for example a natural nuclear fission reactor which ran for thousands of years in present day Oklo Gabon was discovered in the 1970s. It ran for a few hundred thousand years, averaging 100 kW of thermal power during that time.^[14][15]

Conventional, human manufactured, nuclear fission power stations largely use uranium, a common metal found in seawater, and in rocks all over the world,^[16] as its primary source of fuel. Uranium-235 "burnt" in conventional reactors, without fuel recycling, is a non-renewable resource, and if used at present rates would eventually be exhausted.

A cutaway model of the 2nd most powerful presently operating fast breeder reactor in the world. The (BN-600), at 600 MW of nameplate capacity is equivalent in power output to a natural gas CCGT. It dispatches 560 MW to the Middle Urals power grid. Construction of a second breeder reactor, the BN-800 reactor was completed in 2014.

This is also somewhat similar to the situation with a commonly classified renewable source, geothermal energy, a form of energy derived from the natural nuclear decay of the large, but nonetheless finite supply of uranium, thorium and potassium-40 present within the Earth's crust, and due to the nuclear decay process, this renewable energy source will also eventually run out of fuel. As too will the Sun, and be exhausted.^[17][18]

Nuclear fission involving breeder reactors, a reactor which breeds more fissile fuel than they consume and thereby has a breeding ratio for fissile fuel higher than 1 thus has a stronger case for being considered a renewable resource than conventional fission reactors. Breeder reactors would constantly replenish the available supply of nuclear fuel by converting fertile materials, such as uranium-238 and thorium, into fissile isotopes of plutonium or uranium-233, respectively. Fertile materials are also nonrenewable, but their supply on Earth is extremely large, with a supply timeline greater than geothermal energy. In a closed nuclear fuel cycle utilizing breeder reactors, nuclear fuel could therefore be considered renewable. In 1983, physicist Bernard Cohen claimed that fast breeder reactors, fueled exclusively by natural uranium extracted from seawater, could supply energy at least as long as the sun's expected remaining lifespan of five billion years.^[19] This was based on calculations involving the geological cycles of erosion, subduction, and uplift, leading to humans consuming half of the total uranium in the Earth’s crust at an annual usage rate of 6500 tonne/yr, which was enough to produce approximately 10 times the world's 1983 electricity consumption, and would reduce the concentration of uranium in the seas by 25%, resulting in an increase in the price of uranium of less than 25%.^[19][20]

Proportions of the isotopes, U-238 (blue) and U-235 (red) found in natural uranium, versus grades that are enriched. light water reactors and the natural uranium capable CANDU reactors, are primarily powered only by the U-235 component, failing to extract much energy from U-238. While by contrast uranium breeder reactors mostly use U-238/the primary constituent of natural uranium as their fuel.^[21]

Advancements at Oak Ridge National Laboratory and the University of Alabama, as published in a 2012 issue of the American Chemical Society, towards the extraction of uranium from seawater have focused on increasing the biodegradability of the process and reducing the projected cost of the metal if it was extracted from the sea on an industrial scale. The researchers' improvements include using electrospun Shrimp shell Chitin mats that are more effective at absorbing uranium when compared to the prior record setting Japanese method of using plastic amidoxime nets.^{[22][23][24][25][26][27]} As of 2013 only a few kilograms(picture available) of uranium have been extracted from the ocean in pilot programs and it is also believed that the uranium extracted on an industrial scale from the seawater would constantly be replenished from uranium leached from the ocean floor, maintaining the seawater concentration at a stable level.^[28] In 2014, with the advances made in the efficiency of seawater uranium extraction, a paper in the journal of Marine Science & Engineering suggests that with, light water reactors as its target, the process would be economically competitive if implemented on a large scale.^[29]

In 1987, the World Commission on Environment and Development(WCED), an organization independent from, but created by, the United Nations, published Our Common Future, in which a particular subset of presently operating nuclear fission technologies, and nuclear fusion were both classified as renewable. That is, fission reactors that produce more fissile fuel than they consume - breeder reactors, and when it is developed, fusion power, are both classified within the same category as conventional renewable energy sources, such as solar and falling water.^[8]

Presently, as of 2014, only 2 breeder reactors are producing industrial quantities of electricity, the BN-600 and BN-800. The retired French Phénix reactor also demonstrated a greater than one breeding ratio and operated for ~30 years, producing power when Our Common Future was published in 1987. While human sustained nuclear fusion is intended to be proven in the International thermonuclear experimental reactor between 2020 to 2030, and there are also efforts to create a pulsed fusion power reactor based on the inertial confinement principle(see more Inertial fusion power plant).

Fuel supply

Estimates of Available Uranium-235, an isotope required for the present world fleet of (LWRs)light water reactors, that is, not the uranium-238 feedstock needed for some breeder reactor designs, one of which was discussed above. Available U-235 estimates depend on what ore resources are included in the simple extrapolations. The squares represent relative sizes of different estimates, whereas the numbers at the lower edge give an estimate on how long the given resource would last at present U-235 consumption rates, a consumption rate based upon the unrealistic assumption that old LWR generation II reactors will still be operating after their lifetimes are up, 30 years from now, and that no Generation III reactors or generation IV reactors replace these less efficient reactors.
██ Reserves in current mines^[30]
██ Known economic reserves, a figure that has increased from 80 to over 100 years after this estimate was made in 2005.^[31][32][33]
██ Conventional undiscovered resources^[34]
██ Total ore resources at 2004 prices^[30]
██ Unconventional resources (at least 4 billion tons, could last for millennia)^[34]

The world's measured resources of uranium-235 in 2005, economically recoverable at a price of US$130/kg, was estimated to be enough to last from 80 to 100 years at current(2005-2006) consumption rates.^[31] According to the OECD's red book in 2011, due to increased exploration, known uranium-235 resources have grown by 12.5% since 2008, with this increase translating into greater than a century of uranium-235 available if the metals usage rate was to continue at the 2011 level.^[32][33][35]

30,000 to 60,000 years is one estimated supply lifespan of fission-based conventional/light water reactor reserves if it is possible to extract all the uranium from seawater, assuming current world energy consumption.^[36] Alternatively this is about 6,500 years with a potential nuclear reactor fleet of 3,000 GW, a quantity of electricity six to seven times higher than the current world civil nuclear power capacity.^[37]

The OECD have also calculated that with fast breeder reactors such as the BN-800 and conceptual Integral Fast Reactor, which has a closed nuclear fuel cycle with a burn up of, and recycling of, all the uranium, plutonium and minor actinides; actinides which presently make up the most hazardous substances in nuclear waste, there is 160,000 years worth of natural uranium in total conventional land resources and phosphate ore.^[38]

Thorium, an often overlooked alternative to U-238 in breeder reactors, is several times(about 3 to 4)^[39][40][41] more abundant in Earth's crust than all isotopes of uranium combined, with the only natural thorium isotope thorium-232 being several hundred times more abundant than uranium-235.^[42] The average concentration or occurrence of thorium in seawater however is over 1000 times lower, in the range of nanograms per liter compared to uranium which is about 3 micrograms per liter,^{[39][43][44][45]} 3 mg(milligrams) per cubic meter/ton of water.^[28]

In 1983, physicist Bernard Cohen claimed that fast breeder reactors, fueled exclusively by natural uranium extracted from seawater, could supply energy at least as long as the sun's expected remaining lifespan of five billion years.^[19] This was based on calculations involving the geological cycles of erosion, subduction, and uplift, leading to humans consuming half of the total uranium in the Earth’s crust at an annual usage rate of 6500 tonne/yr, which was enough to produce approximately 10 times the world's 1983 electricity consumption, and would reduce the concentration of uranium in the seas by 25%, resulting in an increase in the price of uranium of less than 25%.^[19][20]

Fusion fuel supply

If it is developed, Fusion power would provide more energy for a given weight of fuel than any fuel-consuming energy source currently in use,^[46] and the fuel itself (primarily deuterium) exists abundantly in the Earth's ocean: about 1 in 6500 hydrogen(H) atoms in seawater(H2O) is deuterium in the form of (semi-heavy water).^[47] Although this may seem a low proportion (about 0.015%), because nuclear fusion reactions are so much more energetic than chemical combustion and seawater is easier to access and more plentiful than fossil fuels, fusion could potentially supply the world's energy needs for millions of years.^[48][49]

In the deuterium + lithium fusion fuel cycle, 60 million years is the estimated supply lifespan of this fusion power, if it is possible to extract all the lithium from seawater, assuming current(2004) world energy consumption.^[50] While in the second easiest fusion power fuel cycle, the deuterium + deuterium burn, assuming all of the deuterium in seawater was extracted and used, there is an estimated 150 billion years of fuel, with this again, assuming current(2004) world energy consumption.^[50]

Legislation in the United States

Inclusion under the "renewable energy" classification as well as the low-carbon classification could render nuclear power projects eligible for development aid under more jurisdictions. Thus a key issue regarding this classification of nuclear power is inclusion in Renewable portfolio standard (RES).

A bill proposed in the South Carolina Legislature in 2007-2008 aimed to classify nuclear power as renewable energy. The bill listed as renewable energy: solar photovoltaic energy, solar thermal energy, wind power, hydroelectric, geothermal energy, tidal energy, recycling, hydrogen fuel derived from renewable resources, biomass energy, nuclear energy, and landfill gas.^[51]

In 2009 the Utah state passed the bill ECONOMIC DEVELOPMENT INCENTIVES FOR ALTERNATIVE ENERGY PROJECTS including incentives for renewable energy projects. It includes a direct reference to nuclear power: "Renewable energy" means the energy generation as defined in Subsection 10-19-102 (11) and includes generation powered by nuclear fuel. The bill passed the house with 72 yeas, 0 nays, and 3 absent, passed the senate with 24 yeas, 1 nay, and 4 absent, then received the governor's signature.^[2]

In 2010 the Arizona Legislature included nuclear power in a proposed bill for electric utility renewable energy standards. The bill defined "renewable energy" as energy that is renewable and non-carbon emitting. It listed solar, wind, geothermal, biomass, hydroelectric, agricultural waste, landfill gas and nuclear sources.^[3]

In 2015 the Arizona bill specified that "Nuclear energy from sources fueled by uranium fuel rods that include 80 percent or more of recycled nuclear fuel and natural thorium reactor resources under development" are renewable.^[52]

Supporters

Nuclear energy has been referred to as "renewable" by the politicians George W. Bush,^[53] Charlie Crist,^[54] and David Sainsbury.^[55][56] In 2006, speaking on the topics of economic growth and getting oil from parts of the world where "they simply don’t like us", US President Bush said: "Nuclear power is safe and nuclear power is clean and nuclear power is renewable".^[53]

See also

• Non-renewable resource#Nuclear fuel
• peat - a fuel that is variously classified as a "slow-renewable" by the IPCC or as a non-renewable fossil fuel by the UNFCC
• peak uranium
• Nuclear power debate
• Nuclear fusion
• Star lifting

References