CO2 Emissions from the Nuclear Fuel Cycle

Authors: Mark Diesendorf & Peter Christoff energyscience.org.auOnly reactor operation is CO 2 free; all the other the stages in the nuclear fuel chain use fossil fuels and hence emit CO 2 .

CO 2 Emissions from the nuclear fuel chain will increase substantially as the limited supplies of high-grade uranium ore are used up and as low-grade ore is mined and milled using fossil fuels.

The recent push for a revival of nuclear energy has been based on its claimed reduction of CO 2 emissions where it substitutes for coal-fired power stations. In reality, only reactor operation is CO 2 -free. All other stages of the nuclear fuel chain – mining, milling, fuel fabrication, enrichment, reactor construction, decommissioning and waste management – use fossil fuels and hence emit CO 2 . Also the transport between these parts of the fuel cycle can be very energy intensive as they can be in different countries and require shipping, trucking or rail.

These emissions have been quantified by researchers who are independent of the nuclear industry. Early work was published by Nigel Mortimer, 1 until recently Head of the Resources Research Unit at Sheffield Hallam University , UK . In the 2000s a very detailed study was done by Jan Willem Storm Van Leeuwen, a senior consultant in energy systems, together with Philip Smith, a nuclear physicist, both of whom are based in Holland. 2

These studies find that the CO 2 emissions depend sensitively on the grade of uranium ore used. Following Van Leeuwen and Smith, we define high-grade uranium ores to be those with at least 0.1% uranium oxide (yellowcake U 3 O 8 ). In simpler terms, for each tonne of ore mined and milled, at least 1 kg of uranium can be extracted. For high-grade ores, such as most of those currently being mined in Australia , the energy inputs from uranium mining and milling are relatively small. However, there are significant emissions from the construction and decommissioning of the nuclear power station, with the result that the station must operate for 2-3 years to generate these energy inputs. (For comparison, wind power requires only 3-7 months. 3 )

Low-grade uranium ores contain less than 0.01% yellowcake, i.e. they are at least 10 times less concentrated than the high-grade ores. To obtain 1 kg of yellowcake, at least 10 tonnes of low-grade ore has to be mined. This entails a huge increase in the fossil energy required for mining and milling. Van Leeuwen and Smith find that the fossil energy consumption for these steps in the nuclear fuel chain becomes so large that nuclear energy emits total quantities of CO2 that are comparable with those from an equivalent combined cycle gas-fired power station.

Furthermore, the quantity of known uranium reserves, with ore grades richer than the critical level of 0.01%, is very limited. The vast majority of the world's known uranium resources are low-grade. With the current contribution by nuclear energy of 16% of the world's electricity production, the high-grade reserves would only last several decades. If nuclear energy were to be expanded to contribute (say) half of the world's electricity, high-grade reserves would last less than a decade. No doubt more reserves of high-grade uranium ore will be discovered, perhaps even doubling current reserves, but this would be insufficient for a sustainable substitute for coal.

Recently a physicist, Martin Sevior has produced a critique of Van Leeuwen and Smith's results. 4 Sevior's results for high-grade uranium ore are based on the unpublished data from the Swedish electricity utility, Vattenfall. Unpublished sources have low scientific credibility. The actual results are unbelievable: for instance, based on these data, Sevior claims that the energy inputs to the construction of a nuclear power station are generated in only 1.5 months of its operation. This extraordinarily low result is contradicted by several earlier studies by independent analysts, who find that the energy payback period for the construction of both nuclear and coal fired power stations (which use similar types and quantities of construction materials) is several years. 5

There can be no doubt that, if uranium ore grade declines by a factor of 10, then energy inputs to mining and milling must increase by at least a factor of 10. 6 As ore grade decreases, there has to be grade at which the CO2 emissions from mining and milling become unacceptably high. However, the exact value of this critical ore grade is still subject to continuing scientific debate.

Are there alternative future pathways for nuclear energy that could have lower CO2 emissions? Although there are vast quantities of uranium oxide in the Earth's crust, almost all exist at very low concentrations, typically 4 x 10 -4 %, at which 1000 tonnes of ore would have to be mined to obtain 4 kg of uranium in the form of yellowcake. In this case the energy inputs to extract uranium would be much greater than the energy outputs of the nuclear power station. Sea-water contains uranium at a concentration of about 2 x 10 -7 %, meaning that 1 million tonnes of sea-water would have to be processed to extract just 2 kg of uranium.

Future options

A theoretically possible option would be to switch to fast breeder reactors , which produce so much plutonium that in theory they can multiply the original uranium fuel by 50. The world's last non-military fast breeder reactor, the French Superphoenix, was closed in 1998, after many technical problems and costing about A$15 billion. Even if another fast breeder were to be built in the future, large-scale chemical reprocessing of spent fuel would be necessary to extract the plutonium and unused uranium. Since spent fuel is intensely radioactive, reprocessing has its own hazards and costs. At present there is only one ‘commercial' plant reprocessing spent fuel in the world, La Hague in France . Three November 2006

plants were built and shut down in the USA and the British plant was closed temporarily in April 2005 following the discovery that high-level liquid waste, equivalent in volume to half and Olympic swimming pool, had been leaking undetected over the previous 9 months.

Another possible response to the shortage of high-grade uranium arises from estimates that there is about three times as much thorium in the Earth's crust as uranium. Thorium itself is not fissile (that is,. cannot be split), but, by bombarding it with neutrons, it can be converted into uranium-233, which is fissile. In a conventional approach, the neutrons would be produced by fission of a mixture of uranium-235 and plutonium-239. This would be a complicated system involving a type of breeder reactor, which takes us back to the problems outlined in the previous paragraph. India is attempting to develop such a system. A simpler thorium reactor design would use a particle accelerator to produce the neutrons. This has the advantage that the reactor is fail-safe. Unlike an ordinary uranium reactor, the accelerator-driven thorium reactor can be shut down by simply switching off the particle beam. The nuclear wastes produced by this kind of reactor have much shorter half-lives than from a uranium or plutonium reactor. 7

None of the above proposed ‘solutions' is commercially available and some may be decades away. So, on the basis of present nuclear technology and the small existing high-grade uranium reserves, the potential contribution of nuclear power to the reduction of CO 2 emissions is very limited.

References:

1 Mortimer, N 1991, ‘Nuclear power and global warming', Energy Policy 19:76-8, Jan-Feb.

2 Van Leeuwen, Jan Willem Storm and Smith, Philip 2005, Can nuclear power provide energy for the future; would

it solve the CO2-emission problem? www.stormsmith.nl (accessed 4/1/06 ).

3 E.g. Danish Wind Industry Association 1997, The Energy Balance of Wind Turbines, www.windpower.org/.

See also www.vestas.com/uk/environment/2005_rev/energybalance.asp.

4 Sevior M, 2006, Energy lifecycle of nuclear power.

www.nuclearinfo.net/Nuclearpower/WebHomeEnergyLifecycleOfNuclear_Power

5 e.g. AEA Technology 1998, Power generation and the environment – a UK perspective. Vol. 1. AEAT 3776.

Report prepared for European Commission ExternE study.

6 “At least” because more than one process is involved. It is quite possible that the efficiency of the other

processes decline as ore grade declines.

7 Dean T 2006, New age nuclear. Cosmos Issue 8, 40-49.

About the authors:

Dr Peter Christoff is the co-ordinator of Environmental Studies at the School of Social and Environmental Enquiry at the University of Melbourne . He lectures on climate politics and policy in the University's Centre for Public Policy, and has published widely on Australian and international environmental policy.

Dr Mark Diesendorf is Director of Sustainability Centre Pty Ltd and Senior Lecturer in Environmental Studies at University of New South Wales . He is co-editor with Clive Hamilton of the interdisciplinary book, “Human Ecology, Human Economy: Ideas for an Ecologically Sustainable Future”, and co-author of the national scenario study, “A Clean Energy Future for Australia ”.

 

The Nuclear Cycle Made Simple

Since the atomic bombing of Hiroshima and Nagasaki in 1945, the world has known of the horrors of the nuclear threat. The massive stockpile of nuclear weapons that has risen since - to the point that the planet could be blown up thousands of times over - compounds people’s fear of nuclear devastation, and shows the absurdity and destructiveness that those in power have yielded on our living planet.

The nuclear accidents at Three Mile Island and Chernobyl confirmed the world’s fears of a radioactive disaster occurring at a nuclear reactor. We know uranium is radioactive, that radiation is bad and kills and mutates living organisms, and is the key ingredient of the nuclear cycle. But what is the nuclear cycle? It is hard to understand the scientific jargon and chemistry that comes with this killer technology, the most killer invention of them all. The nuclear cycle for power generation was called safe. Radioactivity will never be safe, no matter what precautions are taken. You don’t need a scientific degree to work that out.

Every part of the nuclear cycle is deadly. This is an attempt to simplify the nuclear cycle and what occurs during it. The nuclear cycle (or nuclear fuel cycle) involves many parts. It starts with land degradation, (for) uranium mining, conversion and enrichment of uranium to produce fuel for reactors, fission (splitting) of uranium in reactors to release heat, (for) the generation of electricity by steam turbines, reprocessing of spent fuel to isolate plutonium and unburned uranium, and storing the radioactive wastes for many thousands of years.

The fact that there is no cure to the enormous amount of nuclear waste we are creating, the nuclear ‘cycle’ is a bit of a misnomer. It is known as a cycle as the plutonium and unused uranium can be returned from the back end of the cycle to the near the front and reused as fuel by reprocessing the wastes.

However the ‘cycle’ is an unnatural one as it is transported around the world for its various operations, threatening radiation accidents at every part of the journey. An example of this is the reprocessing of spent uranium from Sydney’s Lucas Heights reactor. Recently sent to France for reprocessing, passing through local neighborhoods then over sea. It will return to Australia in fifteen years to be stored as nuclear waste.

Uranium is a naturally occurring radioactive element that is the key ingredient in the nuclear cycle.

This is due to its unstable atomic structure. Uranium is a dangerous substance as it is highly radioactive and produces radioactive waste that lasts for hundreds of thousands of years.

Within an atom, there is a nucleus with electrons (negative charge) that orbit around it. Protons (positive charge) and neutrons (neutral charge) are found within the nucleus. An atom is neutral if it has an equal number of elections and protons. Atoms of the same element have the same amount of protons. However atoms of the same element can have different amounts of neutrons and so have different atomic weights known as nuclides. For the uranium element, uranium-235 contains 143 neutrons and 92 protons within its nucleus whereas uranium-238 has 146 neutrons and 92 protons.

Some nuclides known as radioinuclides are unstable and decay into other nuclides. This decay is called radioactivity. Different radionuclides decay at different rates, depending on its instability. A half-life is the time it takes for half the radionuclide to decay. The half-life of uranium-235 is 713 million years while the half-life of uranium-238 is 4.5 billion years.

As the uranium atoms decay, alpha, beta and gamma rays are released. Alpha rays, heavy positively charged particles, can spread radiation very fast, moving several kilometers a second. Beta rays are negatively charged electrons 7000 times lighter than alpha particles, while gamma rays are electromagnetic radiation found in many radionuclides.

The energy released from the decay of uranium takes many thousands of years so cannot be put to use. The atom needs to be ruptured to produce the energy much quicker. In 1938 it was realised that bombarding uranium-235 with neutrons caused the unstable element to fission or split into two smaller atoms and releases more neutrons. This is known as atomic fission.

As uranium-235 atoms split more and more neutrons are released until a chain reaction starts. An uncontrolled chain reaction occurs in nuclear bombs, as seen in Hiroshima and Nagasaki. In a nuclear reactor, the chain reaction must be controlled to avoid the chain reaction growing to a dangerous explosion such as the ones that occurred at Chernobyl and Three Mile Island. Rods containing the element boron are used as boron can clean up excess neutrons. A safe working reactor needs to balance the neutrons being released with the number absorbed by uranium-235 as it splits. Many other safety mechanisms are required to avoid radiation accidents.

Uranium-238 is different to uranium-235 as it rarely fissions, but it can gain a neutron to create plutonium-239. Plutonium-239 is an artificial element that can only be produced by bombarding uranium with neutrons, a process that occurs at nuclear reactors. Plutonium is one of the most toxic substances known. One millionth of a gram is enough to cause cancer. Plutonium replaces calcium in mammal bones, so once in the food chain it remains there.

Plutonium-239 fissions faster than uranium-235. It is used in reactors known as breeder reactors as it is able to produce more plutonium-239 than it burns, overcoming problems of low uranium supplies. However the breeder reactor has not been practically successful and has been rejected by many countries due to safety concerns. It is also mixed with uranium fur use in thermal reactors. Plutonium is most likely to be stockpiled for nuclear bombs.

The mining of uranium is also a dangerous business. Miners are exposed to the hazards of ionizing radiation from radon and radioactive dust. The environment of the mine and surrounds is destroyed. The local communities, often indigenous people, the waterways and whole ecosystems are under threat of, and often are contaminated by radioactive materials. People suffer cancer and birth defects. Other living organisms also suffer these and other fates.

Tailings dams are where all the unwanted material that is mined is stored. Once the mining stops, the tailing dams are left to become hills of fine sand like solids. This retains 80% of the radioactivity of the uranium ore body. Some of this waste material can decay into a gas (radon-222) which can spread over the region. Radioactive radium, dust and radon contaminate surrounding ecosystems. Natural disasters, such as earthquakes or flash floods are often not considered when the dams are designed, posing additional threats. The radioactive dangers persist for over 100 000 years from these uranium mining tailings dams.

An enrichment nuclear reactor producing reactor grade uranium (3% uranium-235) can also produce higher weapons grade uranium (over 90% uranium-235) for use in nuclear weapons. When Australia sells uranium to America or France there is no guarantee that the uranium is only being used for nuclear power. An enrichment plant can produce fuel for nuclear weapons very quickly. Uranium hexafluride (hex) is used for enriching uranium to weapons grade and is a radioactive gas at low temperatures. The hex gas causes major kidney damage, as well as other radiation problems. These gases are released into the atmosphere during enrichment. Workers are also exposed.

Every year one third of the fuel rods in a reactor are replaced. The spent uranium fuel rods are stored in cooling ponds at the reactor to lose its initial radioactivity and heat. This will be reprocessed or stored indefinitely. Each year in an average nuclear reactor, about 250kgs of plutonium is left in the spent fuel.

Radioactive water and gases are regularly released from a nuclear reactor, into the ocean and atmosphere. Many reactors are built near rivers and water supplies. Releasing tritium (radioactive hydrogen) which has been linked to child leukemia and birth defects, and is readily absorbed through the skin. ‘Minor’ accidental releases occur and can often not be publicized. Others like Chernobyl leave a legacy known for generations, affecting millions of people.

Decommissioning a reactor is very expensive, though the price rises the longer it is in operation, as the waste and the reactor must be stored and guarded for hundreds of years. People living near reactors have higher levels of cancer and other illnesses, especially children. All radiation released into the environment will harm living organisms.

Depleted uranium called tails is uranium-238, depleted of its uranium-235. As well as converting it into plutonium, it is also used as depleted uranium weaponry, which has been receiving a lot of attention lately due to increased cancers and illnesses (and birth defects in offspring) of returned Gulf and Balkan war veterans where the weapons were used. (Not to mention the communities that live there) The depleted uranium tails are stronger than lead and able to pierce tanks and other armoured vehicles. It is still radioactive and dangerous to health.

Nuclear waste is placed in three different categories, depending on their health risk- low, intermediate and high levels.

Low level waste includes radioactive rubbish like tools, plastic, building materials, paper and clothing, which are contaminated throughout the nuclear cycle. It is dumped in shallow landfill and covered with earth. Before 1975, it was merely dumped at sea.

Intermediate waste includes containers, equipment and sludges contaminated with transuranic elements, like plutonium and americium. This waste is buried in concrete lined trenches in guarded areas. However, intermediate waste has leaked into surrounding soil and waterways.

Reprocessing uranium produces extremely dangerous radioactive liquid wastes. Most of this high level waste is stored in tanks until it evaporates or solidifies into glass blocks. The glass blocks are to be placed into deep burial sites. The heat of radioactivity (decay) has been found to crack the glass blocks, so it is now placed in cool stores for 100 years before burial.

The fact that the proponents of nuclear power can demand more and more reactors and still not have a safe, long term plan for the storage of this long-lived deadly waste, shows at the very least, irresponsibility or even the possible future genocide of the whole planet. It shows contempt for past, present and future generations. In 5000 years, people will still have radioactive disasters waiting to happen, as in 100 000 years. Of course they may not have to worry about it, as then there is the story of the nuclear bombs.....STOP THE INSANITY LET’S HALT THE NUCLEAR CYCLE.

Daniel Moss