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Our Need for Energy
A modern technological society like Australia makes substantial use of energy to make our lives better and more enjoyable.
Besides having direct benefits, access to cheap electricity and energy enables some aspects of sustainability, such as recycling, to thrive. For example steel-producing
mini-mills require substantial amounts of electricity but do not need Coking Coal, Iron Ore and reuse waste products which would otherwise be dumped somewhere in the environment.
While we can do much to conserve energy, the fact is that Australia has increased its energy consumption by over 2% per year since 1970. Our total energy needs are forecast to
increase by 50% in total by the year 2020.
Meeting this demand requires building many large power-plants over the next 15 years. If we do not do this and our energy demand grows as expected, we will be faced with large scale blackouts. For example, the State of Victoria had a reserve energy deficit of
500 Megawatts in the summer of 2005 which was twice the 229 Megawatt deficit of 2004. This deficit will continue to grow without substantial new electricity generation capacity. However Australia currently produces more Greenhouse Gas per Capita than
every other OECD country. If we build new Coal-fired plants we will make this situation even worse.
This is just Australia. The rest of World's use of energy will rise even faster. This is the inevitable consequence of the development of former third-world nations like China and India. Almost all Third World countries (and certainly China and India) intend to raise their standard of living to Western levels. Indeed if China's economic growth continues as it has for the last 25 years, it
will obtain per-capita wealth comparable to Australia's current income in the decade of the 2040's. India will likely take a few decades more.
Both these Countries have populations of around 1 billion people and such developments will more than double the
world demand for energy. Note that this
will happen. It is not something we in Australia or even the USA or Europe could stop even if we wanted to. The "Developing World" will use energy at a rate comparable to what we did before the end of the 21st Century.
China has
identified Nuclear Power as an
important component of its
future energy mix. India has
long-term plans to develop a fully indigenous Nuclear Power program to meet its own vast energy needs.
It is quite possible to utilize Nuclear Power to provide the vast majority of an entire country's need for electricity. The
French Nuclear Power program is the exemplar of this. In France, Nuclear Power provides 77% of the nation's need for electricity (the remainder being Hydroelectricity). France generates a surplus of electricity which it exports to neighbouring countries at a profit. It does this while costing the dismantling of its reactors and disposing of its waste products in the price of the electricity it generates.
The current electrical energy consumption for the entire planet is 1517 GW of continuous power.
There are
currently 439 nuclear power plants with a capacity of 371 GW. These
provided
16% of the electrical power production of the world.
The Australian Broadcasting Commission recently aired an excellent investigation into Nuclear Power, entitled "Who's afraid of Nuclear Power?". You can download this program from this
link.
How Nuclear Reactors Work
When an atom undergoes fission it splits into smaller atoms, other particles and releases
energy. Read about the
physics of fission. It turns out that it is
possible to harness the energy of this process on a large enough scale for it to be a
viable way of producing energy. Read about
how power plants work.
The fundamental point about nuclear energy is that the energy content of 1 gram of Uranium is equivalent to approximately 3 tonnes of coal. This means that we
need to consume about
3 million times less material with Nuclear Power compared to using Coal or
any other Fossil Fuel. This substantially reduces the volumes of fuel and waste of nuclear power compared to Fossil Fuels.
The Different Types of Nuclear Reactors
There are are a number of different types of Nuclear Reactors currently in operation throughout the world. Some of the most common types are described here.
Pressurized Water Reactors
Pressurized Water Reactors (PWR's) are by far the most common type of Nuclear Reactor deployed to date. Ordinary water is used as both neutron moderators and coolant. In a PWR the water used as moderator and primary coolant is separate to the water used to generate steam and to drive a turbine. In order to efficiently convert the heat produced by the Nuclear Reaction into electricity, the water that moderates the neutron and cools the fuel elements is contained at pressures 150 times greater than atmospheric pressure. You can find out more details of PWR reactors at the following link.
Pressurized Water Reactors.
Boiling Water Reactors
In a Boiling Water Reactor (BWR), ordinary light water is used as both a moderator and coolant, like the PWR. However unlike the PWR, in a Boiling Water Reactor there is no separate secondary steam cycle. The water from the reactor is converted into steam and used to directly drive the generator turbine. These are the second most commonly used types of reactors. Find out more about Boiling Water Reactors at the following link.
Boiling Water Reactors.
High Temperature Gas Cooled Reactors.
High Temperature gas cooled reactors operate at significantly higher temperatures than PWRs and use a gas as the primary coolant. The nuclear reaction is mostly moderated by carbon. These reactors can achieve significantly higher efficiencies than PWRs but the power output per reactor is limited by the less efficient cooling power of the gas. You can find out more about these types of reactors at the following link.
High Temperature, Gas Cooled pebble reactors
Heavy Water Reactors
Heavy Water reactors are similar to PWRs but use water enriched with the deuterium isotope of Hydrogen as the moderator and coolant. This type of water is called "heavy water" and makes up about 0.022 parts per million of water found on Earth. The advantage of using Heavy water as the moderator is that natural, unenriched Uranium can be used to drive the nuclear reactor. You can find out more about these reactor types at the following link.
CANDU Heavy Water Reactors
Advanced Nuclear Fission Technology
Please read
the physics of fission before reading this section.
Uranium Fast Breeder Reactors
Natural Uranium consists of 0.7% 235U and 99.3% 238U. All commercial Power reactors used in the world today utilize the 235U component in natural Uranium as the primary means of maintaining a chain reaction. The most troublesome component of nuclear waste are the tran-Uranic elements that occur when 238U captures a neutron and transmutes to 239Pu. Further neutron captures on this element lead to a buildup of long-lived transuranic nuclei. However 239Pu is also fertile and undergoes fission like 235U. Advanced reactor designs exploit this to convert the 238U to 239Pu. If the reactor avoids the slowing down, "thermalization" of neutrons, there are sufficient excess neutrons that it is possible to convert more 238U to 239Pu than 235U is consumed. These reactors use the unmoderated "fast" neutrons directly produced via the fission process.
Thus
these reactors "breed" 239Pu from 238U and so produce more fuel than they consume. The use of fast-breeder technology makes it possible to increase the efficiency of Uranium use by over a factor of 50. It is then possible to exploit the vast quantities of depleted Uranium stockpiled around the world to generate electricity. In addition the excess neutrons can be used to transmute the long-lived transuranic waste from current Nuclear Power reactors to ever-heavier isotopes until they eventually fission. Thus these reactors can be used to "burn" the most troublesome component of nuclear waste.
There have been a
number of
reactors that demonstrated that the Fast-Breeder concept works in principle at large scale. The
superphenix and
monju reactors in France and Japan have had serious technical issues and superphenix has been shut down. This type of reactor is more costly to construct and more difficult to operate than a conventional second-generation Power Reactor. Never-the-less these experiments have provided valuable data that will be used as input for the "Fourth Generation" nuclear reactors presently under research and development.
Thorium Breeder Reactors
Thorium is an element that is 3 times more abundant than Uranium on earth. It has a single stable isotope 232Th. In a nuclear reactor this isotope can capture a neutron and be converted to 233U. 233U undergoes fission like 235U and 239Pu. However when 233U fissions it releases more neutrons than either 235U or 239Pu. Consequently it is possible to to construct a breeder reactor that utilizes thermal neutrons to both generate energy and to breed 233U from Thorium given sufficient initial quantities of 233U mixed with 232Th.
A further advantage of Thorium breeders is that the amount of transuranic waste is vastly decreased compared to a Uranium or Plutonium based reactor.
The
Indian Nuclear Power program has a long term goal of utilizing the Thorium cycle to obtain energy independence.
Accelerator Driven Fission.
Over the last 10 years the idea of using a high current, high energy accelerator to drive Nuclear Fission has emerged. These are the Accelerator Driven Systems or ADS. Unlike a Nuclear Reactor, an ADS drives Nuclear reactions that will stop if the proton beam from the accelerator stops. Thus there is no prospect of nuclear chain reactions proceeding out of control. ADS can be used to either generate energy or to transmute transuranic long-lived waste into much shorter lived radio-nuclei, or they can be used to do both. In addition these systems hold prospect of efficiently burning 238U and naturally occurring Thorium, which is 3 times more abundant than Uranium. Over the last 10 years the ADS has progressed from proof of principle experiments to
one tenth scale test facilities.
More details of Accelerator driven Fission systems are found
here
The Fourth Generation Reactors
In 2002 the Gen iV Internation Forum (GIF) nations (Argentina, Brazil, Canada, France, Japan, Korea, South Africa, Switzerland, Russia, United Kingdom and the United States of America) proposed a long term research and developement
program to investigate 6 promising new reactor designs.
The six design concepts are:
These reactor concepts are designed to address the energy needs of the World into the far future (post 21st century).
- They efficiently utilize Uranium (many can employ depleted Uranium or "spent" fuel from current reactors).
- Destroy a large fraction of nuclear waste from current reactors via transmutation.
- Generate Hydrogen for transportation and other non-electric energy needs.
- Be inherently safe and easy to operate.
- Provide inherent resistance to Nuclear Weapons proliferation.
- Provide a clear cost advantage over other forms of energy generation.
- Carry a financial risk no greater than other forms of energy generation.
These reactor concepts are at various levels of development. The first deployments of Generation IV reactors are not expected until 2015. Most will not be ready before 2025. However the long term potential of these projects is enormous. For example one Molten-Salt Reactor designed to consume one tonne of Uranium per year, could supply sufficient Hydrogen to supply
3 million passenger vehicles. The waste from the plant's year's operation would occupy half the volume of a typical domestic refrigerator. The radioactivity of the waste would diminish to background levels in about 500 years.
Safety of Nuclear Power Plants
Safety is taken very seriously by those working in nuclear power plants. The main safety concern is the emission of uncontrolled radiation into the environment which could cause harm to humans both at the reactor site and off-site. A summary by the nuclear world association on environmental, health and safety issues can be found at
the Nuclear World Association website.
The Union of Concerned Scientists has an
extensive website devoted to the detailed safety issues faced by American Nuclear Power Industry. These provide an interesting perspective on the importance both of a vigilent safety culture and a pro-active regulatory oversight.
Safety Mechanisms of a Nuclear Power Reactor
By regulation, the design of the nuclear reactor must include provisions for human (operator) error and equipment failure. Nuclear Plants in the western world use a "Defense in Depth" concept which is a system with multiple safety components, each with back-up and design to accommodate human error. The components include:
1. Control of Radioactivity
This requires being able to control the neutron flux. Recall that in a nuclear reactor when a neutron is captured by a fuel nucleus (generally uranium) the nucleus splits releasing radioactive particles (or undergoes fission). Hence if we decrease the neutron flux we decrease the radioactivity. The most common way to reduce the neutron flux is include neutron-absorbing control rods. These control rods can be partially inserted into the reactor core to reduce the reactions. The control rods are very important because the reaction could run out of control if fission events are extremely frequent. In modern nuclear power plants, the insertion of all the control rods into the reactor core occurs in a
few seconds, thus halting the nuclear reaction as rapidly as possible.
In addition, most reactors are designed so that beyond optimal level, as the temperature increases the efficiency of reactions decreases, hence fewer neutrons are able to cause fission and the reactor slows down automatically.
2. Maintenance of Core Cooling
In any nuclear reactor some sort of cooling is necessary. Generally nuclear reactors use water as a coolant. However some reactors which cannot use water use sodium or sodium salts.
3. Maintenance of barriers that prevent the release of radiation
There is a series of physical barriers between the radioactive core and the environment. For instance at the
Darling Nuclear Generation Station in Canada the reactors are enclosed in heavily reinforced concrete which is 1.8m thick. Workers are shielded from radiation via interior concrete walls. A vacuum building is connected to the reactor buildings by a pressure relief duct. The vacuum building is a 71m high concrete structure and is kept at negative atmospheric pressure. This means that if any radiation were to leak from the reactor it would be sucked into the vacuum building and therefore prevented from being released into the environment.
The design of the reactor also includes multiple back-up components, independent systems (two or more systems performing the same function in parallel), monitoring of instrumentation and the prevention of a failure of one type of equipment affecting any other.
Further, regulation requires that a core-meltdown incident must be confined only to the plant itself without the need to evacuate nearby residence.
Safety is also important for the workers of nuclear power plants. Radiation doses are controlled via the following procedures,
- The handling of equipment via remote in the core of the reactor
- Physical shielding
- Limit on the time a worker spends in areas with significant radiation levels
- Monitoring of individual doses and of the work environment
See the following websites for more detailed information and further references,
World Nuclear Association Summary on Nuclear Reactor Safety
Wikipedia information on Nuclear Reactors
Safety Mechanisms at a Canadian Nuclear Power Station
Final report of the US Nuclear Regulatory Commission on the Advanced Westinghouse AP1000 Nuclear Reactor design
In addition readers should be aware that the safety of any large scale industrial activity is an on-going concern and must always be taken seriously. Nuclear Power is certainly no exception and unfortunately the US Nuclear Industry did not give it the full attention it needed before the Three Mile Island accident. An excellent description of the safety issues surrounding early nuclear power plants is provided by Robert Pool. It can be downloaded
from here. The article describes how complex interacting technologies offer substantial challenges to safety. Consequently a major goal of
3rd generation Power plants is to provide inherent safety and simpler design.
Accidents at Nuclear Power Plants
Like any large scale industrial activity, there have been numerous accidents and mistakes at Nuclear Power plants and reprocessing facilities. A partial list of these is available from this
wikipedia link.
However two large accidents have had the greatest impact on global consciousness regarding Nuclear Power. These are:
Here are additional links that describe the after effects of the Chernobyl accident.
The Chernobyl accident resulted from a lack of "safety culture" at the plant, design flaws in the RBMK reactor and a violation of procedure. The lessons learned from Chernobyl and the phasing out of the older reactor design means that an accident of this type is most unlikely to occur again.
Since the contained meltdown at Three Mile Island reactor, many improvements have been made to Nuclear Reactor design. The third generation reactors currently proposed are designed so that a failure leading to a contained core melt-down, (which would destroy the commercial value of the reactor) should occur at the rate of
1 in 2-million reactor-years. If the cost of a new reactor is 2 billion dollars and operates for 60 years, this risk would amount to an extra $80,000 insurance.
After the events on September 11th, 2001, many people were reasonably concerned about the safety of nuclear power plants from terrorist activities. However the containment facilities of
nuclear reactors and the
structures holding spent fuel rods are very strong and make hard terrorist targets.
Radiation
Dose
The biological effects of heavy particle ionising radiation are measured with a quantity called Absorbed Dose. However, while two differing particles may have the same amount of energy, they may have very different responses from our living, biological cells, so a factor called
Relative Biological Effectiveness (RBE) is also used. RBE is a measure of the amount of cell damage a given type of particle causes as compared to a dose of x-rays with the same energy. The combination of RBE with Absorbed dose is measured in units called Sieverts.
| Estimated dose (Micro-Sieverts) | Activity |
|---|
| 5 | sleeping next to your spouse for one year |
| 10 | a year of watching TV at an average rate |
| 10 | a year of wearing a luminous dial watch |
| 10 | a year of living in the USA from nuclear fuel and power plants |
| 10 | a day from background radiation (average, varys a lot throughout the world) |
| 20 | having a chest x-ray |
| 65 | flying from Melbourne to London, via Singapore |
| 300 | Yearly dose due to body's potassium-40 |
| 460 | maximum possible offsite dose from Three Mile Island Accident |
| 400 - 1000 | Average annual dose from Medical sources |
| 7,000 | having a PET scan |
| 8,000 | having a chest CT (CAT) scan |
| 50,000 | off-site dose from accident at Chernobyl Nuclear Power Plant (estimates vary widely) |
| 2,000,000 | Typical single dose to Cancer region from Radiation Therapy |
| 700,000 - 13,000,000 | staff and firefighters at the Chernobyl Nuclear Power Plant during and immediately after the accident |
| 65,000,000 | Typical total dose to Cancer region from Radiation Therapy |
Background, naturally occurring environmental sources of radiation include cosmic radiation (which occurs when subatomic particles from outside the solar system interact with the Earth's atmosphere and produce a shower of gamma rays, neutrons and leptons), terrestrial radiation (due to naturally occurring radionuclides such as uranium, radium and thorium which are present in rocks, soil and water), internal radionuclides (most common is potassium-40 which emits beta and gamma particles as it decays, and may be found as a fraction of the total amount of potassium in the body). The largest source of our dose from background radiation is from radon-220 and radon-222 gases, which are the airborne products of the decay of terrestrial uranium. Inhalation of radon gas contributes approximately two-thirds of the dose that is received from natural, background sources.
Biological Effects of Radiation.
Thus we can see that during our normal daily activities we are continually
exposed to ionising radiation both from natural and human-made sources.
The passage of ionising radiation through the body may produce adverse
biological effects. The effects of concern are primarily, although not
solely, due to damage to the genetic material inside the cell; the DNA
or `double-helix' molecule that carries genetic information. The current
scientific data suggests that there is no safe minimum, or threshold, for adverse
radiation effects on the DNA of biological systems and that even small
doses can produce consequences for the organism. The low-dose response
of biological systems it believed to be linear - that is, smaller
doses of radiation produce a proportionately smaller risk of adverse
effects like a straight-line graph.
The biological effects fall into the following categories;
Cell Death or Apoptosis
- biological systems are composed
of many individual tiny cells; each with its own DNA (only
red blood cells don't have any DNA - they lose it during development).
If there is catastrophic damage to vital cell function by radiation
energy absorption the cell may cease to function and `die'.
Cancer Induction
- in this case the DNA is damaged or altered
but the alteration is not lethal to the cell. If the normal regulator
genes which control the rate at which cells divide and die are rendered
malfunctioned the cell may become `immortal' and multiply at an
abnormal rate producing an out-of-control growth of a line of abnormal
cells. This is a cancer. Most tissues can produce cancers with enough
radiation damage but rapidly dividing tissue lines, such as blood-forming
`haemopoietic' lines which may produce leukemias, are particularly vulnerable. The
risk for cancer production in the general population is estimated
to be approximately 0.06 cases per million Micro-Sieverts of absorbed dose.
Genetic Damage to Future Generations
- this can arise because
mutations, or changes in the pattern of bases in the DNA, can occur
in the DNA that ends up in sperm or eggs and becomes a permanent
feature of any resulting babies. Most often, radiation induced damage
to such egg or sperm DNA is incompatible with the life of the fetus
in utero but there is a finite chance of a live baby being born with
defects. This is of particular concern because the damage to the genetic
material can then be passed on to all future generations and become a
permanent feature of the gene-pool; damaging many individuals. Of course,
such mutations are also a natural part of life and the evolution of
biological systems. The concern is that we do not want to increase the
mutation rate above the natural background rate. The estimated risk
of permanent damage to a second generation (grandchild) individual
is 0.02 cases per million Micro-Sievert of exposure.
Dose-Response Tissue Reactions
- or `radiation burns'. These
are the sorts of effects seen immediately after the bombing of
Hiroshima; but lesser effects can occur with smaller doses. However, there
does seem to be a `threshold' for this kind of effect with very small
doses encountered in normal life (apart from sun-burn!) not producing
detectable damage.
More information on the biological effects of radiation can be found
at the
International Commission on Radiological Protection
web site.
A Study on Childhood Cancers in Great Britain
A study on the incidence of childhood cancer around nuclear power plants in Great Britain by the Health Protection Agency for the committee on Medical Aspects of Radiation in the environment concluded that there have been no increase in childhood cancers for children living less than 25km from a nuclear power plant. The report was published in 2005.
Download the report
here.
Waste from Nuclear Power
What is Nuclear Reactor Waste?
The generation of electricity in a Nuclear Power Plant is made by splitting uranium atoms. The uranium used as fuel in a nuclear plant is formed into ceramic pellets about the size of the tip of your little finger. The uranium atoms in these pellets are bombarded by atomic particles, they split (or fission) to release particles of their own. These particles, called neutrons, strike other uranium atoms, splitting them. When the atoms split, they also release heat. This heat is known as nuclear energy and is essentially responsible for creating electricity.
Other reactions also take place in the nuclear reactor such as neutron capture. Neutron capture is a term used for the scenario where a neutron comes close to a nucleus (in this case uranium) and the nucleus captures it and becomes a different nucleus. In this case when uranium-238 captures a neutron it becomes uranium-239. After uranium-239 emits a beta particle (electron) it becomes neptunium-239. Then neptunium-239 also emits a beta particle and becomes plutonium-239. The plutonium can also be used as nuclear fuel but it is less efficient than uranium.
Certain changes take place in the ceramic fuel pellets during their time in the reactor of the nuclear power plant. The particles left over after the atom has split are radioactive. During the life of the fuel, these radioactive particles collect within the fuel pellets. The fuel remains in the reactor until trapped fission fragments begin to reduce the efficiency of the chain reaction. Some of the fission products are various isotopes of barium, strontium, cesium, and iodine. The spent fuel also contains plutonium and uranium that was not used up. The fission products and the left over plutonium and uranium remain within the spent fuel when it is removed from the reactor and are called high level waste as they are extremely hot and very radioactive.
A Short Review of Radioactive Isotopes and Half-lives
In this subsection a review on radioactivity is provided so that the reader will have a better understanding of the nuclear waste issue.
An atom that is radioactive will decrease its radioactivity in time and eventually decay. How fast the radioactivity decreases depends on the half-life. The half-life is defined as the time it takes for half of the radioactivity to decay. Hence an isotope with a short half-life will decay quickly. The half-life is also inversely proportional to the intensity of radioactivity. Therefore the higher the intensity of radioactivity the shorter the half-life.
The approximate half-lives of some of the isotopes in the spent nuclear fuel are listed below:
| Isotope | Half-life |
|---|
| Strontium-90 | 28 years |
| Caesium-137 | 30 years |
| Plutonium-239 | 24,000 years |
| Caesium-135 | 2.3 million years |
| Iodine-129 | 15.7 million years |
It is clear from the table above that the left over nuclear isotopes from the generation of electricity through nuclear power are extremely long lived and therefore must be shielded from humans and the environment for a long time.
Storage and Disposal of High Level Nuclear Reactor Waste
Since the spent nuclear reactor (SNF) fuel is highly radioactive initially it is too dangerous to handle and thus it is very important to shield the radioactivity from humans and the environment. The radioactive material in the SNF generally falls into three categories: (1) un-reacted fuel, usually uranium, (2) fission products, and (3) activation products, most notably plutonium. Because of the nature of radioactivity, on a per-atom or by-weight basis the fission products are by far the most radioactive, and have the shortest half-life. The un-reacted uranium and the plutonium have vastly longer half-lives, but are correspondingly less radioactive. Once the SNF has been removed from the nuclear reactor it is placed in interim storage at the reactor site. Usually this consists of putting the nuclear waste into large pools of water. The water cools the radioactive isotopes and shields the environment from the radiation. Nuclear waste is typically stored in these supervised pools between 20-40 years. As the SNF ages the radioactivity decreases, reaching the point where it does not need to be water cooled and can be placed in dry storage facilities. Throughout this time there is a great reduction in heat and radioactivity and this makes handling of nuclear waste safer and easier.
After this “cooling off” period the high level waste can be handled in different ways. It can be reprocessed then disposed of permanently or directly disposed permanently in a geological repository.
1. Reprocessing
Recall that the spent nuclear fuel contains uranium and plutonium which are used as fuel in a nuclear reactor. It is possible to isolate much of the uranium and plutonium from the other fission products in spent nuclear fuel so that it can be recycled as fresh fuel to power the nuclear reactor. This is called reprocessing. After reprocessing the left over waste is largely liquid. It is then embedded into borosilicate glass and put into interim storage. Eventually it will be disposed of permanently deep underground.
2. Final Disposal
Eventually the nuclear waste will have to be stored indefinitely because of the long time it takes for some of the waste isotopes to decay to a safe level. The consensus of most waste management specialist for final disposal is to bury the waste deep underground. In doing so we must ensure that the radioactive waste does not move from its burial site or that it does not escape into the environment. If it does it could have dire consequences for future generations such as contamination of drinking water.
To ensure that the radioactive waste is contained the current consensus is to use a multi-barrier system to store the waste. The geological disposal system consists of firstly surrounding the conditioned and packaged solid waste by several human made barriers then placing this at a depth of several hundred meters in a stable geological environment. The geological formation is the most important of the isolation barriers. The barriers act in concert to initially completely isolate the radioactive particles so they can decay and then limit their release to the environment. The combination of man made and natural geological barriers is called a multibarrier system.
The solidification of nuclear waste (which is necessary for final disposal) usually consists of dispersal in a glass matrix. However, alternative techniques are being researched. One such technique consists of embedding the waste into a ceramic matrix such as Synroc.
Synroc is a “synthetic rock” invented in 1978 by Professor Ted Ringwood of the Australian National University. Synroc can incorporate nearly all the elements contained in high level waste.
The barriers surrounding the solid waste vary from country to country. However most countries believe that the barriers should be made of materials that occur naturally in the earth’s crust. In
Sweden, the barriers consist of
1. A copper canister with a cast iron insert. This barrier is closest to the waste and its function is to isolate the fuel from the environment.
2. The second layer consists of bentonite clay called a buffer. Its function is to protect the the canister against small movements in the rock and keep it in its place. The clay also acts as a filter in case any radioactive particles escape form the canister.
3. The geological rock. The rock also stops leaking of radioactive particles into the environment but its main function is to protect the canister and buffer from mechanical damage and to offer a stable environment for the isolation of the waste.
Current Programs for final disposal of nuclear waste
Currently, no country has a complete system for storing high level waste permanently but many have plans to do so in the next 10 years. There are a number of well-developed proposals from the
USA,
Sweden,
Finland and France for the disposal of long-lived radio-active waste.
All the proposed disposal techniques employ multiple barriers, as discussed above, to isolate the waste from the biosphere for at least 100,000 years. Nevertheless every one of the proposed disposal methods faces
strong opposition from environmental groups and it is true that humans have never attempted to do
anything on this sort of timescale. However nature has plenty of examples of systems that are stable for much longer periods. The most spectacular being the trans-uranic products of the Oklo natural nuclear reactors, which are discussed below, which have not appreciably moved in over 1.7 billion years.
The World Nuclear Industry appears to have reached a consensus to pursue Geologic disposal as final phase of Nuclear waste management. The US National Academies of Science, Engineering and Medicine also conclude that
deep Geologic Disposal can provide a safe means of disposing high level waste.
There are a number of programs that have seriously mishandled the issue of waste from Nuclear Power. The British decision to reprocess spent-fuel appears to have been both an
environmental and financial mistake. The Nuclear Weapons program at the
Hanford site in Eastern Washington State, U.S.A, created an enormous environmental impact that has so far cost 5.7 billion dollars to clean up.
Currently waste from Nuclear Power plants is being held in temporary storage facilities until such time as long-term disposal is decided. This is a feasible option because of the relatively small amount of material used to generate Nuclear Power.
New Technologies for Waste Disposal
Another option for disposal of long-lived (trans-Uranic) waste is to burn it via either
Accelerator Driven Systems or within
Fourth Generation reactors. However these technologies are not yet mature. Since the waste is stored in large tanks of water for 20-40 years first, it may be that by this time these new technologies will be sufficiently developed so that waste can be destroyed using these new methods.
Read an article on transmutation from
The Economist.
How much high level nuclear waste is produced in a nuclear reactor?
According to the
International Atomic Energy Agency a nuclear reactor which would supply the needs of a city the size of Amsterdam – a 1000MW(e) nuclear power station – produces approximately 30 tonnes of high level solid packed waster per year if the spent fuel is not reprocessed.
In comparison, a 1000MW(e) coal plant produces 300,000 tonnes of ash per year.
Currently, worldwide, nuclear power generation produces 10,000m3 of high-level waste per year.
Who is responsible for the nuclear waste?
In most countries it is the responsibility of the power companies to take care of the waste. They are responsible for all the cost of nuclear waste management. In fact most countries are obliged to set aside a certain amount of money each year for waste management. Furthermore there are strict guidelines imposed by governments and other bodies for safe and responsible nuclear waste management. For example the International Atomic Energy Agency runs frequent conferences on the science of nuclear waste disposal, setting and enforcing safety standards, monitoring safety and security of nuclear waste. Recent conferences can be found on the
IAEA website.
A natural nuclear reactor
Eventual final disposal of nuclear waste means that the radioactive isotopes will be buried (with appropriate barriers - see "Final disposal" above) in an appropriate disposal site for a very long time. One of the serious questions we should consider is are there going to be any problems far in the future associated with the burial of the waste. The system for final waste disposal is usually based on naturally occurring phenomena. One such natural analogue is naturally occurring nuclear reactors in Gabon, West Africa in the Oklo mine called the Oklo nuclear reactors.
About 1.7 billion years ago, deep underground in Africa, favorable natural conditions prompted nuclear reactions to take place. These natural conditions were sufficient amounts of Uranium-235 and the evolution of plants which subsequently caused rainwater to filter down through cracks in rocks. The water was necessary to slow down the neutrons emitted via uranium decay so that they could interact with other particles and produce nuclear chain reactions. The reactors operated for about 1 million years. The reactions stopped because the uranium depleted to amounts that were too small to keep the reactions going.
It has been shown that the Oklo reactors fissioned Uranium-238, Uranium-235 and Plutonium-239. This is exactly the elements that are fissioned in todays man-made nuclear reactors. Note also that there was no Plutonium-239 on earth when the Oklo reactors formed. This means that the reactors themselves must have produced this isotope. This is also the case for man-made nuclear reactors.
Once the natural reactors burned out they left radioactive nuclear waste. This waste is very similar to the waste generated by nuclear power stations. The nuclear waste was held in place deep underground by granite, sandstone and clays surrounding the reactors' site. The important point is that the waste has not moved much over approximately 2 billion years (see the
fact sheet from Office of Civilian Radioactive Waste Management, USA and the article by Walton and Cowan from the "Proceedings of a Symposium on the Oklo Phenomenon", 1975 listed in the bibliography at the end of this section).
The Oklo reactors give us an opportunity to observe the effects of storing waste deep underground for billions of years. By analyzing the remains of these ancient natural nuclear reactors and gaining an understanding of the conditions needed to secure and contain the nuclear waste, we can apply the same techniques to the final disposal of man-made nuclear reactor high level waste. The study of the Oklo nuclear reactors means that we can have reasonable confidence in final disposal.
Bibliography for Waste from Nuclear Power
The sources on man-made high level nuclear waste have been,
International Atomic Energy Agency Factsheet on Nuclear Waste
Nuclear Energy Agency
Swedish Nuclear Waste Management
Finland Nuclear Waste Management
French Nuclear Waste Management
USA Office of Civilian Radioactive Waste Mangagement
Synroc
Technical Report series no. 43, International Atomic Energy Agency, 2003, "Scientific and Technical Basis for the Geological Disposal of Radioactive Wastes"
The sources for the Oklo natural nuclear reactors have been,
R.D Walton Jr., G.A. Cowan, "Relevance of Nuclide Migration at Oklo to the Problem of Geologic Storage of Radioactive Waste", from the International Atomic Energy Agency, Vienna, 1975, "Proceeding of a Symposium on the Oklo Phenomenon".
Curtin University Information on Oklo
Office of Civilian Radioactive Waste Management, USA - Oklo Fact Sheet
Other information on natural nuclear waste storage can be found through the following link,
Natural Analogues of Nuclear Waste Storage
Transport of Nuclear Waste
The task of transporting the waste from a Nuclear Reactor to its eventual disposal destination is a problem that needs to be solved. The US Department of Energy currently proposes that a
dedicated train be used for this purpose. This is a matter of
great concern for many people, particularly those who live near the routes taken by the train. Sweden uses sea transport to move its Nuclear Power waste to disposal facilities. This appears far less controversial. There is continual research into the transport of radioactive materials. An overview of the current activities of the International Atomic Energy Agency
(IAEA) with regard to transport of materials is available
here.
Nuclear Weapons Proliferation
A connection between nuclear power and nuclear weapons exists because both require fissile materials. Some of the technology that can be used to produce or purify a fissile material for a nuclear power plant could also be applied to producing nuclear weapons. There are three main fissile materials that are used in nuclear reactions:
Uranium-233 (233U)
Uranium-235 (235U)
Plutonium-239 (239Pu)
In addition, Plutonium-240 (240Pu) and Plutonium-241 (241Pu) are produced and consumed in Nuclear Power production but neither can be used for Nuclear Weapons.
Out of these three materials only 235U exists naturally as an isotope of natural uranium with concentrations of 0.7%. Plutonium-239 and Uranium-233 are created by neutron capture on 238U and Thorium-232 (232Th) respectively.
Uranium-235
This is currently the most common fuel in nuclear reactors. Natural Uranium must be enriched to contain about 3-5% 235U before it can be used in most conventional reactors. The CANDU Heavy-Water reactor can use natural Uranium. To create a weapon Uranium must be enriched above 80%. Highly enriched Uranium (more than 20% enrichment) is also used for reactors in naval vessels and for research reactors.
Various techniques can be used to
enrich Uranium. Any of these techniques used to enrich Uranium for power plants could in theory be further used to produce 235U in pure enough quantities for nuclear weapons.
Plutonium-239
This is the preferred isotope for
Nuclear weapon design as it has a lower critical mass and is easier to produce in large quantities than 235U. 239Pu and 240Pu are produced in nearly all nuclear reactors by neutron capture on naturally occurring 238U, and can be easily separated from the Uranium. However, for the purposes of Nuclear Weapon's 240Pu is an unwanted component as it has a high rate of spontaneous fission which limits the a nuclear weapon from achieving critical mass for long enough to consume a large fraction of the fissile material. Weapons grade Plutonium is defined to contain no more than 7% 240Pu. That said, the USA exploded a nuclear weapon in 1962 with a 240Pu content in excess of 7%. The
World Nuclear Association estimates that the 240Pu concentration of the device was 10%.
Other people
estimate that the concentration of 240Pu in the test may have been much higher and that weapons with "reactor grade" plutonium are possible.
This has very important consequences for Nuclear Weapons proliferation. If a batch of Plutonium has more than 7% 240Pu, it is unlikely to used for a Nuclear Weapon. Firstly because of the difficulty is creating a useful weapon with this material and because the mass difference between 240Pu and 239Pu is too small to allow normal isotopic enrichment procedures to work satisfactorily so that the plutonium cannot be enriched in 239Pu.
Nuclear reactors must be operated in a special and easily detectable way in order to create 239Pu with a sufficiently low abundance of 240Pu to be used in a Nuclear Weapon. What happens is this: Starting from a fuel that consists solely of 238U and 235U, the 238U will capture a neutron and convert to 239U. Shortly there-after the 239U will decay to Neptuium-239 (239Nu). The 239Nu then
decays to 239Pu. Now 3 out of 4, neutron reactions on 239Pu initiates fission which destroys the 239Pu. However one in four neutron reactions are neutron captures which instead convert 239Pu into 240Pu. 240Pu does not undergo fission and so the relative abundance of 240Pu compared to 239Pu increases with the time the nuclear fuel spends in the reactor.
See the figure below.
Consequently in order to create weapons-grade plutonium, the fuel of the reactor must be removed before the concentration of 240Pu has a chance to exceed the 7% threshold. As is shown in the figure this means the fuel must be removed before it has spent 4 months in the reactor.
For this reason, Light Water reactors are what are called "proliferation resistant". In order to remove the fuel, the reactor must be shutdown. Shutting down a 1 GigaWatt reactor is very easy detect and is clearly not in the best interests of power production. When such events occur it is easy for the International Atomic Energy Agency
(IAEA) to inspect the fuel rods and verify that no weapons grade Plutonium has been created or diverted. A standard light-water reactor that has been operated continuously for more than 4 months is not capable of producing weapons grade plutonium.
However other types of reactors such as Heavy Water reactors and some types of Breeder reactors do not have this built-in safe-guard. In these reactors fuel can be removed without a power-down. They require much more serious monitoring to ensure that weapons-grade Plutonium is not being created.
Uranium-233
Uranium-233 is produced by neutron capture of Thorium-232 in much the same way as Plutonium-239 is produced. There is very little information on the use of Uranium-233 for constructing nuclear weapons. There are also no commercial Thorium breeder reactors.
Nuclear Non-Proliferation Treaty
The
Nuclear Non-Proliferation Treaty was designed to limit the spread of Nuclear Weapons. In exchange for full access to the most advanced Uranium fuels and nuclear technology, countries must agree to detailed inspections by the IAEA. In the past the IAEA has not always successfully detected non-compliance. For example in Iraq before the 1991 war. The IAEA has been recently successful detecting suspicious behavior, such in North Korea and Iran. The IAEA has also been forthright in declaring the absence of such behavior such as in Iraq in shortly before the second Iraq war. Director-General of the IAEA Dr. ElBaradei and the IAEA itself were awarded the
Nobel Peace prize in 2005.
The Australian
Inquiry into developing Australia's non-fossil fuel energy industry has received submissions
critical of the IAEA and its ability to adequately implement the NPT.
Many of these
were refuted by a subsequent submission by the Australian Safeguards and Non-Proliferation Office (ASNO).
Availability of Usable Uranium
Uranium is present at an abundance 2 - 3 parts per million in the Earth's crust which is about 600 times greater than gold
and about the same as tin. The amount of Uranium that is available is mostly a measure of the price that we're willing to pay for it. At present the cost of Natural Uranium ($165 per kg) is a small component in the price of electricity generated by Nuclear Power. At a price of $US110 per kg the known reserves amount to about 85 years supply at the current level of consumption with an expected further 500 years supply in additional or speculative reserves. The price of Uranium would have to increase by over a factor of 3 before it would have an impact of the cost of electricity generated from Nuclear Power. Such a price rise would stimulate a substantial increase in exploration activities with a consequent increase in the size of the resource (as has been the case with every other mineral of value). The price of Uranium rose to a peak of over 300/kg in 2007 but has since declined to $165 by early 2008.. The world reserves of Uranium have increased by around 50% since the end of 2003.
However
advanced technologies are being developed which are far more efficient in their use of Uranium or which
utilize Thorium which is 3 times more abundant than Uranium. If perfected these technologies can make use of both the spent fuel from current nuclear reactors and the depleted Uranium stocks used for enrichment. Taken together these provide enough fuel for many centuries of energy production. This will mitigate the demand for newly mined Uranium.
Size of the Uranium Resource
Uranium is a dense metal found at an abundance of 2.8 parts per million in the Earth's crust.
It is a highly reactive metal that does not occur in a free state in nature,
commonly occurring as an oxide U
3O
8.
Prices for Uranium in the world market are quoted in $US per pound of U
3O
8.
The amount of Uranium commercially recoverable depends upon the market price of the metal.
The market price in early 2008 is around US$165/kg, after peaking at over $300/kg in 2007. In the early 1990's the spot price of Uranium reached historical lows of less than US$22/kg [1].
The cost of mining Uranium is a very small factor in the cost of running a nuclear power station and so movements in the price have little effect on the price of the power produced.
The sources of uranium are: mining, commercial inventories (from earlier periods of oversupply), reprocessing of spent full rods from nuclear power plants and down blending (mixing of enriched uranium with natural or
depleted uranium) of
highly enriched uranium from dismantled nuclear weapons. Consumption of uranium at the end of 1999 was 61600 tonnes of Uranium metal (tU) per annum [2] of which 56% is sourced from uranium mining.
The majority of the balance comes from stockpiles and down blending in former Soviet countries as they reduce or eliminate their stock of nuclear weapons.
The importance of this source and that of commercial inventories is expected to diminish over the next ten years.
Reasonably assured reserves (or proven reserves) refers to known commercial quantities of Uranium recoverable with current technology and for the specified price. As well there are estimates of
additional and
speculative reserves in extensions to well explored deposits or in new deposits that are thought to exist based on well defined geological data.
These are necessarily subject to a larger uncertainty, however, the historically low price of uranium over the past ten years has provided a disincentive to exploration.
This is beginning to be rectified as the price recovers.
Further exploration will reduce the uncertainty in the estimates of additional reserves.
There are around 4000 million tU in sea water at a concentration of approximately 3 parts per billion. Extracting this Uranium
is a significant challenge [3] but substantial progress has been demonstrated by
Seko et al. These researchers recovered approximately 1 kg of Uranium in a 16 square meter cage submerged for 240 days off the coast of Japan. A
patent related to these efforts has been granted. The cost of extracting Uranium from sea water using
methods of Seko et al. was estimated by
Tamada et al to be approximately $900/kg with the technology employed in the experiment reported above. Tamada et al. note that this may fall to $127/kg with improvements to the Uranium absorbent.
As of the beginning of 2003 World Uranium reserves were
- Reasonable Assured Reserves recoverable at less than $US130/kgU (or $US50/lb U3O8) [4] = 3.10 - 3.28 million tU [2,5].
- Additional reserves recoverable at less than $US130/kgU (or $US50/lb U3O8) = 10.690 million tU [2].
As of the beginning of 2005 World Uranium reserves were
- Reasonable Assured Reserves recoverable at less than $US130/kgU (or $US50/lb U3O8) = 4.7 million tU [6].
- Additional recoverable Uranium is estimated to be 35 million tU [6].
The substantial increase (almost 50%) from 2003 shows the results of the world-wide renewed exploration effort spurred by the increase in Uranium prices which commenced in 2004. This increase in activity has continued through to 2008.
Thus, the provable uranium reserves amount to approximately 85 years supply at the current level of consumption with current technology, with another 500 years of additional reserves. Around 24% of the proven reserves are in Australia.
With current technology,
235U is the only fuel for nuclear reactors. Uranium-235 represents 0.72% of natural uranium. Future technological developments could allow other elements to fuel nuclear reactors.
Thorium-232 is a possible nuclear fuel and has a similar abundance to uranium, though there are as yet no commercial reactors operating
or planned that would utilize thorium. Fast breeder reactors could utilize both
235U (Uranium-235) and
239Pu (Plutonium-239) as a fuel.
Plutonium-239 is created when
238U (99.27% of naturally occurring uranium) is bombarded with neutrons.
Plutonium-239 is a by product of nuclear power generation with the current mix of
235U and
238U.
It is currently a waste product of concern due to its extreme toxicity and link to nuclear weapons.
If reactors could be made to utilize
239Pu the potential of known reserves of uranium would be greatly extended since
238U could then be turned into a fuel.
The Super Phoenix fast breeder reactor in France has demonstrated the technology.
Currently electricity from such a plant would cost around three times the amount per kilowatt as that from conventional nuclear power plants. Fast breeder reactors have a higher risk profile due to the need to handle large quantities of Plutonium,
and so present a different balance between utility and risk than the other types of reactors.
[1] The Market for Uranium: An overview of supply, demand and prices 2004--2025,
International Nuclear Inc., in Western Mining Corporations Ltd Target Statement (for the takeover by BHP),
December 2004.
[2]
Survey of Energy and Resources 2001, World Energy Council (WEC)
[3] See
van Leeuwen and Smith and references within.
[4] Though the cost of extraction could be more than twice the current spot price of Uranium, the spot price is a function of the current, and speculated future, supply and demand situation and is virtually independent of the price of electricity finally produced from nuclear power.
[5]
Supply of Uranium, World Nuclear Association, July 2005
[6]
Global Uranium Resources, IAEA, June 2006
Cost of Nuclear Power.
The cost of generating power via nuclear energy can be separated into the following components:
- The construction cost of building the plant.
- The operating cost of running the plant and generating energy.
- The cost of waste disposal from the plant.
- The cost of decommissioning the plant.
Quantifying some of these costs is difficult as it requires an extrapolation into the future.
Construction Costs
Construction costs are very difficult to quantify but dominate the cost of Nuclear Power. The main difficulty is that third generation power plants now proposed are claimed to be both substantially cheaper and faster to construct than the second generation power plants now in operation throughout the world. The Nuclear Industry says its learned the lessons of economy-of-volume demonstrated by the French Nuclear Program, and that these will be employed for the new power plants. Westinghouse
claims its Advanced PWR reactor, the
AP1000, will
cost USD $1400 per KW for the first reactor and fall to USD
$1000 per KW for subsequent reactors. They also claim these will be ready for electricity production 3 years after first pouring concrete. A more technical description is
here. Proponents of the
CANDU ACR and
Gas Cooled pebble bed reactors make similar or stronger claims. This should be compared to second generation plants which, in the U.S.A., had construction costs up to
$5000 per KW and generally took more than five years to complete.
The
General Electric ABWR was the first third generation power plant approved. The first two ABWR's were commissioned in Japan in 1996 and 1997. These took just over 3 years to construct and were completed on budget. Their construction costs were around
$2000 per KW. Two additional ABWR's are being constructed in Taiwan. However these have faced unexpected delays and are now at least 2 years behind schedule.
Meanwhile the Chinese Nuclear Power Industry has won contracts to build new plants of their own design at capital costs
reported to be $1500 per KW and $1300 per KW at sites in South-East and North-East China. If completed on budget these facilities will be formidable competitors to the Western Nuclear Power Industry.
Given the history of Nuclear Plant construction in the U.S.A., the financial industry sees the construction of the new generation of reactors as a risky investment and demands a premium on capital lent for the purpose. The
Energy Bill recently passed by the US Congress assumes this risk and provides production credits of 1.8 cents per KW-Hr for the first 3 years of operation. This subsidy is equivalent to what is paid to Wind Power companies and is designed to encourage new nuclear reactor construction in the USA.
If the AP1000 lives up to its promises of $1000 per KW construction cost and 3 year construction time, it will provide cheaper electricity than any other Fossil Fuel based generating facility, including Australian Coal power, even with no sequestration charges.
Construction Cost Over-Runs
There were
massive cost overruns for plants built in the USA in the 1970's and 1980's. There were several reasons for these.
- Design Flaws. There were significant design flaws which led to the reactor leak and operator confusion that caused the Three Mile Island accident. After these were exposed, the US Nuclear Regulatory Commission (NRC), undertook an extensive review of Nuclear Plant designs and in many cases ordered changes. These changes were both expensive and time consuming to fix. They led to extensive construction delays at a time of very high interest rates and so significantly increased the cost of the Capital required to build the plant.
- Two hurdle licensing. Up until the mid-1990's developers of nuclear power plants had to obtain both a license to build a Nuclear Power then a subsequent license to operate the plant. This also delayed the start of plant operation which significantly increased the cost of the plant. The worst situation was that of the Shoreham Plant which was completed on Long Island in New York State at a cost of 5 Billion dollars but was never allowed to operate.
- Non-uniform designs. The US Nuclear Power Industry never achieved economies of volume because every reactor design was different. Each developer put in their own tweaks and much of the equipment was custom built for each plant. This compounded the difficulties of obtaining NRC licensing approval since the NRC had to evaluate each individual design.
In contrast the French Nuclear Power program settled on a standard design which satisfied the French Regulatory Commission. Industry was able to achieve economies of volume in the production of plants and to complete construction on time.
Operating Costs
These costs are much easier to quantify and are independently verified as they relate directly to the profitability of the Utilities which operate them. Any discrepancies are soon discovered through accounting audits. Company's that operate the USA's nuclear power reactors have made excellent profits over the last
five years.
The US Nuclear Power industry has
at last lived up to its promise made in in 1970's to produce electricity reliably and cheaply. Since 1987 the cost of producing electricity from has decreased from
3.63 cents per KWHr to 1.68 cents per KWHr in 2004 and plant availability has increased from 67% to over 90%. The operating cost includes a charge of
0.2 cents per KW-Hr to fund the eventual disposal of waste from the reactor and for decommissioning the reactor. The price of Uranium Ore contributes approximately 0.05 cents per KWHr.
Management of Nuclear Plant Operations
It's clear from both the French and US experience that pro-active Industry organisations are vital in obtaining efficient plant utilisation and in minimising running costs. In the US in the late 1980's and early 1990's there was little pooling of knowledge and experience amongst Nuclear Power Operators. This was caused by a combination of industry inexperience, the lack of standardised designs and the fragmentation of the industry. Once again this was in contrast to the French experience where the uniform design and the single state-owned organisation allowed knowledge to be more easily shared.
The US industry has has since gone through several cycles of consolidation and the operation of the USA's fleet of Nuclear Reactors has mostly been taken over by specialist companies that specialize in this activity. In addition the industry has learned the benefits of pooling knowledge. This combination has demonstrably improved the performance of the US reactor fleet and is reflected in the
share price of the
nuclear operation companies.
Waste Disposal
In the USA, Nuclear Power operators are charged 0.1 cents per KW-Hr for the disposal of Nuclear Waste. In Sweden this cost is
0.13 US cents per KW-Hr. These Countries have utilized these funds to pursue research into Geologic disposal of waste and both now have mature proposals for the task. In France the cost of waste disposal and decommissioning is estimated to be 10% of the construction cost. So far provisions of 71 billion Euros have been acquired for this from the sale of electricity.
Decommissioning Costs
The US industry average cost for
decommissioning a power plant is
USD $300 million. The funds for this activity are accumulated in the operating cost of the plant. The French and Swedish Nuclear Industries expect decommissioning costs to be 10 -15 % of the construction costs and budget this into the price charged for electricity. On the other hand the British decommissioning costs have been projected to be around
1 Billion pounds per reactor. Cleaning up the Hanford Nuclear Weapons reactor is budgeted at 5.6 Billion dollars but may cost 2 to 3 times this much.
Model of Projected Costs
The following simple model gives a reasonable guideline to the cost in US cents of electricity per KW-Hr based on various assumptions for construction cost, interest rate and construction time. The model assumes that the capital for the entire
project is delivered up-front before construction commences. This is a conservative approach. A better financing deal would to acquire capital as it needs to spent during construction. A 40-year lifetime is assumed. The operating costs are assumed to be 1.3 cents per KW-Hr in line with the second best-quartile of the American Nuclear Plant average. The plant availability is assumed to be 90% in-line with the full American average since 2000. The plant is assumed to have a 1 GW capacity.
The current discount interest rate in the USA is about 5%. China appears to be taking the Nuclear Power industry
at its word that it can deliver generating power at USD$1500 per KW of capacity. As of August 30th, 2005, reports state that China expects to pay USD$6 Billion dollars for 4 GW worth of Nuclear Plant and that this will come on-line by 2010.
Reports from December, 2006 state that the Chinese have contracted to buy 4 Westinghouse
AP1000's with start up expected in 2013. The final price of the contract is unclear this time. If the Nuclear Power Industry delivers generating capacity at $1500 per kilowatt it will likely place the price of electricity produced at around
3 US cents per KWHr. This would be similar to the price of electricity generated by Eastern Australian Coal-Power which is in the range of
2.2 - 4.5 AUD cents per KWHr. It will be well worth watching to see if the Industry can deliver this outcome.
The construction costs expected by the Chinese are far lower than what the Nuclear Industry delivered in the 1980's. For example the ill-fated Shoreham facility, which was never allowed to operate, cost
5 Billion dollars for a plant rated at 1 GW. Case 5, shown below, shows the what our model predicts for this scenario.
Case 1, Construction Cost = $1 Billion. (Westinghouse claim for its AP1000 reactor after volume production.)
(The numbers in all the tables are the costs to generate electricity in US cents per KWHr for different interest rates and construction times)
Case 2, Construction Cost = $1.4 Billion. (Westinghouse claim for its first AP1000 reactor)
Case 3, Construction Cost = $2.0 Billion.
Case 4, Construction Cost = $2.5 Billion.
Case 5, Construction Cost = $5 Billion (Shoreham, Long Island, 1985).
Greenhouse Emissions of Nuclear Power
There is world-wide concern over the prospect of Global Warming primarily caused by the emission of Carbon Dioxide gas (CO2) from the burning of fossil fuels. Although the processes of running a Nuclear Power plant generates no CO2, some CO2 emissions
arise from the construction of the plant, the mining of the Uranium, the enrichment of the Uranium, its conversion into Nuclear Fuel, its final disposal and the final plant decommissioning. The amount of CO2 generated by these secondary processes primarily depends on the method used to
enrich the Uranium (the gaseous diffusion enrichment process uses about 50 times more electricity than the gaseous centrifuge method) and the source of electricity used for the enrichment process. It has been the subject of
some controversy. To estimate the total CO2 emissions from Nuclear Power we take the work of the Swedish Energy Utility,
Vattenfall, which produces electricity via Nuclear, Hydro, Coal, Gas, Solar Cell, Peat and Wind energy sources and has produced
credited Environment Product Declarations for all these processes.
Vattenfall finds that averaged over the entire lifecycle of their Nuclear Plant including Uranium mining, milling, enrichment, plant construction, operating, decommissioning and waste disposal, the total amount CO2 emitted per KW-Hr of electricity produced is
3.3 grams per KW-Hr of produced power. Vattenfall
measures its CO2 output from Natural Gas to be 400 grams per KW-Hr and from coal to be 700 grams per KW-Hr. Thus nuclear power generated by Vattenfall, which may constitute World's best practice, emits less than one hundredth the CO2 of Fossil-Fuel based generation. In fact Vattenfall finds its Nuclear Plants to emit
less CO2 than any of its other energy production mechanisms including Hydro, Wind, Solar and Biomass although all of these processes emit much less than fossil fuel generation of electricity.
Energy Lifecycle of Nuclear Power
The performance of Nuclear Power can also be measured by calculating the total energy required to build and run a Nuclear Power plant and comparing it to the total energy it produces. The following set of calculations is also taken from the independently audited, Vattenfall
Environmental Product Declaration for its 3090 MW Forsmark power plant.
A more detailed description is
here. Vattenfall have also made available the aggregated data set as a spreadsheet. You can download it
from here.
The following table displays the source and the amount of energy required to produce 1 KW-Hr of electricity from the Forsmark power plant. The table includes the energy used in construction of the plant, mining the Uranium, enriching it, converting it to fuel, disposing the waste and decommissioning the plant. The Forsmark plant is assumed to run for 40 years. There is an additional 0.026 grams of Uranium consumed in generating this one KW-Hr of electricity. This 0.026 grams includes the Uranium used to generate power at Forsmark and the Uranium consumed by the French Nuclear Power plants that produced the electricity that enriched the Forsmark Fuel.
| Energy Source | Contribution by mass | Conversion to Energy | Energy Contribution |
|---|
| Coal | 0.467 grams | 0.00676 KW-Hr/gram | 0.0031 KW-Hr |
| Crude Oil | 0.32 grams | 0.011 KW-Hr/gram | 0.0035 KW-Hr |
| Lignite | 0.234 grams | 0.0038 KW-Hr/gram | 0.00089 KW-Hr |
| Natural Gas | 0.115 grams | 0.015 KW-Hr/gram | 0.00173 KW-Hr |
| Hydro-Electricity | 0.00146 KW-Hr | 1 | 0.00146 KW-Hr |
| Wood | 0.041 grams | 0.0042 KW-Hr/gram | 0.00017 |
| Total | | | 0.0107 KW-Hr |
So the Forsmark Plant produces 93 times more energy than it consumes. Or put another way, the non-nuclear energy investment required to generate electricity for 40 years is repaid in 5 months. Normalized to 1 GigaWatt electrical capacity, the energy required to
construct and decommission the plant, which amounts to 4 Peta-Joules (PJ), which is repaid in 1.5 months. The energy required to
dispose of the waste is also 4 PJ and repaid in 1.5 months. In total this is
less than 0.8% of the all the electrical energy produced by the plant.
The calculations of the operating energy costs include the energy required to mine and mill the Uranium. In the case of the Forsmark power plant some of the Uranium is sourced from the Olympic Dam mine in South Australia. This mine has a rather low Uranium concentration (0.05% by weight). A detailed and audited environmental description of the Olympic Dam mine is available
here. A succinct description of the energy inputs of the mine is
here. These data show that the Olympic Dam mine supplies enough Uranium for the generation of 26 GigaWatt-years of electricity each year (including the Uranium needed to run the power plants for enrichment). The energy consumed by the the mine is equivalent to 22% of a GigaWatt-Year. The energy gain is over a factor of 100. The Olympic Dam mine energy cost includes the energy required for mining and smelting it's huge Copper production.
Another Uranium source for Forsmark is the Rossing Mine in Namibia. A description of the operations of the mine is available
here. The Rossing mine produced 3037 tonnes of
Uranium in 2004, which is sufficient for 15 GigaWatt-years of electricity with current reactors. The energy used to mine and mill this Uranium was about 3% of a GigaWatt-year. Thus the energy produced is about 500 times more than the energy required to operate the mine.
It is worth noting that the widely quoted paper by
Jan Willem Storm van Leeuwen and Philip Smith (SLS), which gives a rather pessimistic assessment of the Energy Lifecycle of Nuclear Power, assumes a far larger energy cost to construct and decommission a Nuclear Power plant (240 Peta-Joules versus 8 Peta-Joules(PJ)). The difference is that Vattenfall actually measured their energy inputs whereas Willem Storm van Leeuwen and Smith employed various theoretical relationships between dollar costs and energy consumed. This paper also grossly over-estimates the energy cost of mining low-grade Ores and also that the efficiency of extraction of Uranium from reserves would fall dramatically at ore concentrations below 0.05%. Employing their calculations predicts that the energy cost of extracting the Olympic Dam mine's yearly production of 4600 tonnes of Uranium would require energy equivalent to almost 2 one-GigaWatt power plants running for a full year (2 GigaWat-years). You can follow this calculation
here. This is larger than the entire electricity production of South Australia and an order of magnitude more than the measured energy inputs.
The Rossing mine has a lower Uranium concentration (0.03% vs 0.05% by weight) than Olympic Dam and the discrepancy is even larger in the case of Rossing. Here SLS
predict Rossing should require 2.6 Giga-Watt-Years of energy for mining and milling. The total consumption of all forms of energy in the country of Namibia is equivalent to 1.5 GigaWatt-Years, much less than the prediction for the mine alone. Furthermore, yearly cost of supplying this energy is over 1 billion dollars, yet the value of the Uranium sold by Rossing was, until recently, less than 100 million dollars per year. Since Rossing reports it's yearly energy usage to be 0.03 GigaWatt-years, SLS overestimates the energy cost of the Rossing mine by a factor of 80.
Additionally SLS predict that the yield of of Uranium extracted from low grade Ores will fall to 0 at concentrations of 0.0002% (2 ppm). The Olympic Dam mine extracts gold at high efficiency at concentrations of 0.0005% (5 ppm (parts per million)) and there are many other gold mines which produce gold profitably at this concentration. Given the huge Uranium reserves present at 5 ppm, it unlikely we will ever need mines that operate lower than this.
The energy cost of the Olympic Dam mine is the sum of all the operations for mining Copper, Uranium, Gold and other minerals. It is therefore the upper limit of the energy cost of extracting the Uranium alone. The Rossing mine which only produces Uranium, is a better measure of the energy cost future Uranium mines.
It is interesting to see what effect using the correct energy cost of 8 PJ for the construction, decommissioning and waste disposal of a power plants and the measured energy consumption of the Rossing mine has within the methodology of Willem Storm van Leeuwen and Smith. If we assume that the energy cost of extraction scales inversely with concentration and employ the Rossing experience as a benchmark, ore concentrations as low as 0.001% (10 ppm) provide an energy gain of 16. This also (and very unrealistically) assumes no further progress in mining technology or efficiency improvements in Nuclear Power operations over the course of hundreds of years. As shown
here there is an estimated 1 trillion tonnes of Uranium at concentrations of 10 ppm or higher within the Earth's crust. This provides a resource over a factor of 300 times greater than predicted by Willem Storm van Leeuwen and Smith to be recoverable. So once the correct energy cost for plant construction and mining operations are used, the work of Willem Storm van Leeuwen and Smith imply that resource exhastion will not be a problem for Nuclear Power for the foreseeable future.
Storm and Smith have released a rebuttal of this argument. You can find this rebuttal
here. We have responded in detail to the questions raised by Storm and Smith. You can find our reponse
here. Storm and Smith have issued a rebuttal to our response. It is
here. Our answer to this is
here.
Our additional investigations strengthen the conclusion that there is far more minable Uranium than predicted by Storm and Smith.
Comparison of Energy Sources
What sort of energy source is used for a particular purpose should in the end be reflected in the price of the energy generated by the source.
Fossil Fuels
The World's Fossil Fuels are a finite resource that will be consumed within 500 years at present and projected future rates of consumption. In addition these are often accompanied by substantial pollutants and of course their major waste by-product, carbon-dioxide gas, is the major Greenhouse emission of concern.
There is general consensus within the Scientific Community that a new phase of global warming induced by carbon-dioxide emissions is currently underway and that the World's temperature will rise significantly within the next century. There is still substantial debate about the climatic consequences of this temperature rise although there is little doubt that the world's climate will be different in 100 years time if we continue to increase our rate of consumption of fossil fuels. Given that there is no clear consensus on the outcome of the global warming and that some of the consequences are
very dire indeed, the safe course of action is to limit the amount of Global Warming and hence to limit the amount of Greenhouse gas emission.
To date the cost of the carbon-dioxide emissions from Fossil fuels has not been priced into to their use.
Recently
Carbon Dioxide Sequestration has emerged as potential solution to the global warming problem. This is the process of trapping Carbon in the bio-sphere instead distributing it within the atmosphere. There are now a number of methods proposed to achieve this which range from developing new
bio-masses (forests, algae) to injection of C02 into
Deep Oceans or storing in
underground reservoirs including
Natural gas and Petroleum fields. Many of these may be implemented within 20 years and could potentially be paid for via a carbon tax. A document providing an overview of various CO2 sequestration options is available
here. This study estimates that 80 years worth of current CO2 production could be stored at a cost of about 50 Euros (80 AUD) per tonne CO2 stored.
Oil
Oil is the most precious and least abundant of the world's fossil fuels. Never-the-less the amount of Oil on the Earth is likely at least the range of several trillion barrels of Oil once non-conventional sources of Oil are considered. These include the Heavy Oil deposits of South America, the Oil sands of Western Canada and shale Oil found through out the World. In addition as the price of Oil increases, previously abandoned fields become economic to re-extract. Consequently despite constantly increasing Oil production throughout the world, there is likely at least a century of usable Oil available in the world. A more useful question is: At what price will petroleum and gasoline be widely displaced as the fuel of choice for transport? It has already been largely displaced as a fuel for Electricity. It appears that world demand from Oil is such that OPEC can no longer
control its price and output from the most readily refined petroleum
has peaked. In July, 2006, the Australian Broadcasting Commission televised another an excellent documentary about high Oil prices. You can download it from
here. The Chicago tribune have produced an excellent series on Peak Oil in their July 29th edition. You can find it
here.
Coal
Coal is the most abundant fossil fuel. It is found throughout the world and current proven reserves are sufficient for at least 300 years of exploitation. Although coal is cheap, it is
dangerous to mine (thousands of miners die every year all over the world) and is bulky and expensive to transport. Because coal has relatively low energy content for its weight, a lot of it is required to produce a given amount of electricity. For example, A 1000 MW coal power station requires about 8,600,000 kg of coal per day, compared to 74 kg per day of uranium for the
equivalent sized nuclear power plant. In addition coal-based power plants produce vast amounts of pollutants, including radioactivity, in addition to the C02 emissions which contribute to global-warming.
Natural Gas
Natural Gas reserves are intermediate between Coal and Oil. It is currently the most favoured fuel source for new electricity production with the USA. Natural gas
combined-cycle generators can reach 60% efficiency for converting heat energy into electricity. Natural gas also produces 40 -50 % fewer CO2 emissions for the same amount of electricity generated as Coal. However the price of Natural Gas is steadily rising and the costs associated with sequestration of the generated CO2 are not yet included in the price of electricity passed on the consumer. The following table from
a comprehensive study of the cost of electricity production from coal and gas in the USA without sequestration charges or other pollution charges shows the price sensitivity of natural gas production. All prices for Natural Gas are shown in units of thousand Cubic Feet (MCF).
The following table shows the effects of a Carbon tax to pay for sequestration.
The price of Natural Gas delivered via long-term contracts as Liquified Natural Gas (LNG) is typically around $6 per MCF.
Within the USA, Natural Gas prices have been extremely
volatile over the past few years as production has not been able to keep pace with demand. As of March, 2006 the
spot price was around $7.50 per thousand Cubic Feet (MCF).
Nuclear Fission
The cost of Nuclear Fission Power is dominated by the capital cost of construction of the plant. Proponents of next generation, (3rd generation), Nuclear Power plants project construction costs of around $1000 - $1200 per KW (
Westinghouse AP1000,
Advanced Boiling Water Reactor,
Advanced CANDU Reactor,
South Africa HTGR), significant increases in Uranium efficiency and substantial increases in operating life of the plant (60 years). In addition the proponents claim a ten-fold increase in safety of operation over previous generation reactors. Electricity generated from such plants is projected to cost less than
3.5 US cents per KW-Hr which is substantially cheaper than current Gas and Coal fired Power Stations even without sequestration charges. Electricity produced at these rates would also be competitive with Eastern Australian coal powered
electricity prices of
2.3 - 4.0 US cents per KW-Hr.
Disposal of Nuclear Waste remains a topic of intense debate and controversy. However the USA, Sweden, Finland and France have well-developed programs for waste disposal funded from the sale of electricity.
Current Australian electricity prices do not include any sequestration charges. Although Australia has not signed any treaty requiring compliance with the reduction of carbon emissions, (citing National Interest reasons), we may be compelled by the international community to do so in the future.
Nuclear Fission is currently unique in that the costs of decommissioning and waste disposal are fully reflected in the price of the generated electricity.
The nuclear industry has longer-term plans to develop advanced reactors that are over 50 times more efficient in their use of Uranium and which consume a large fraction of the long-lived waste generated from current (2nd generation) reactors. In addition these plants may also be used to efficiently
produce Hydrogen for use as a transportation fuel and to
de-salinate sea water. These are the
Fourth Generation Nuclear Reactors and are not expected to be ready for deployment before 2020.
There is a
large and
very vocal opposition to Nuclear Fission power because of the radioactive material produced in the process of generating energy and from Nuclear Proliferation