When problems such as greenhouse gases or the imminent energy crisis are brought up in conversation, nuclear energy is often cited as a solution. The advantages are apparently easy to quantify. According to many, nuclear energy is a near boundless source of energy and does not have the disadvantage of CO₂. emissions.

However, thorough research has shown that these common assumptions are not at all correct. The average nuclear power plant doesn’t start producing energy for 10 years. Over its lifetime it produces more than one million tons of CO₂. and ultimately very little in the way of net energy.

What Is Nuclear Energy?

What is commonly referred to as nuclear energy is more precisely known as nuclear fission. This process involves splitting heavy nuclei, usually uranium isotopes, which are split into new atomic nuclei together weighing somewhat less than the sum of the original material. The missing mass is converted into energy in accordance with the well-known formula penned by Einstein:

E = mc²

Because the term c² is so big – about 300,000,000 meters per second – a lot of energy is released in atomic fission even if only a very small portion (several percent) of the mass is converted. There are other atoms such as plutonium and thorium that are fissionable. Uranium is converted into plutonium during the nuclear reaction in the reactor core and is also partially split creating more energy. Spent nuclear fuel can be recycled for about 95%. The amount left after recycling and the material used to pack the fission material, also radioactive to a greater or lesser degree, together makes up the nuclear waste.[1]

The Nuclear Fuel Chain

In order to understand the whole process involved in generating nuclear energy, it is important to look at the entire nuclear fuel cycle. This chain is made up of the following parts:

• Uranium Extraction
• Conversion
• Enrichment
• Manufacturing the Fuel Rods
• Generation of Energy at the Nuclear Plant
• Temporary Storage of the Fuel Rods
• Cooling Nuclear Components
• Disassembling of the Nuclear Components
• Processing Nuclear Waste
• Storage of Nuclear Waste

The only energy produced in the whole operation is during the step “generation of energy at the nuclear plant”. The other steps merely cost energy. To understand how much net energy is produced at a nuclear plant is is important to look at the complete nuclear fuel chain. Below is a flowchart of the entire nuclear fuel chain.

The Nuclear Fuel Chain. Source: [5]

Uranium Extraction

Yellowcake, or ammonium diuranate, is a uranium ore that exists naturally on earth. By weight, it is made up of 70 to 80 percent uranium oxide (U₃O₈).

Uranate is another naturally occurring uranium ore. A lot of ore must be mined to extract U-235. For instance, at the Olympic Dam where ore is found with a uranium percentage of 0,05%, 2000 kilo grammes only contains one kilo gramme of this uranium isotope.[6]

Uranium Mine Rabbit Lake

Whereas there are more than 4000 oil fields in the world, there are only a handful of uranium mines.
At this time, more than 73% of uranium originates from only ten mines. The table below gives an overview of the ten largest mines.

Mine	Country	Stock (tU) *	Uranium grade **	Production 2005 (tU)	Percentage World Production
McArthur River	Canada	75.118	20,7%	7.200	17,3%
Ranger	Australia	22.073	0,165%	5.006	12,0%
Olympic Dam	Australia	58.512	0,051%	3.688	8,9%
Rossing	Namibia	4.255	0.029%	3.147	7,6%
krazbokamensk	Russia	–	–	3.000	7,5%
Rabbit Lake	Canada	1.192	0,68%	2.316	5,5%
McClean Lake	Canada	4.912	0.68%	2.112	5,1%
Akouta	Niger	7.909	0.46%	1.778	4,3%
Arlit	Niger	16.716	0,3%	1.315	3,2%
Beverley	Australia	17.800	0,15%	825	2,0%
Top 10 totaal				30.387	73,1%

* Sum of stored and proven reserves of uranium ore.

** Percentage is the weighed average of stored and proven reserves of uranium ore.

Sources: [7], [8]

Large amounts of radioactive and acidic mud is left behind at the mine in most cases. For instance: the Olympic Dam mine in Australia now uses 15.9 million gallons of water daily – managing the acidic mud and radioactive waste that results is a huge environmental problem. [9]

In the eighties, the waste of some mines was simply dumped in nature. It is not clear what is happening to that waste currently.

In the eighties millions of tons of mostly radioactive liquid and illiquid waste was dumped in Fookes Lake from the Beaverlodge uranium mine. Source: [18]

Conversion to UF₆

Before uranium can be enriched it must first be converted into gas. Uranium hexafluoride (UF₆) is the only suitable chemical composition because it has a high vapor pressure at room temperature.

Uranium hexafluoride is made by binding uranium to fluorine. This bond is converted to a gas at room temperature by lowering the pressure.

The chemical process involved in the production of UF₆ is called conversion. [17]

Enrichment

Enriched uranium is uranium contains more U-235 isotope than it has in its natural state. It is used in nuclear energy and nuclear weapons.

The uranium found in nature consists mostly of U-238, a small fraction of U-235 and traces of U-234. Only U-235 is fissionable. Natural uranium has only an average of 0.7% U-235. To keep a chain reaction going a higher percentage of U-235 is required. Most nuclear reactors need uranium with at least three percent uranium-235. The process of attaining a higher percentage is referred to as enrichment.

Two methods are used to enrich uranium currently. The process exploits the fact that U-235 is lighter than U-238. The U-235 content can be raised using gas centrifuges or with gas diffusion.[10]

A row of centrifuges at the Urenco Factory

Making the Fuel Rods

The fuel for the power plant can then be made following the enrichment process. UF6 is converted into uranium oxide (UO₂). Ceramic pellets are the most common form of reactor fuel. These are made from compressed uranium oxide, which is derived from a sintering (baking) process at more than 1400 degrees centigrade. The pellets are then put in metal canisters and thus form fuel rods which are arranged as fission packages for use in a reactor.[17]

The Fuel Rods. Source [19]

Nuclear plant

The fuelrods with enriched uranium are used in the nuclear plant for the process of nuclear fission.

The uranium fuel rods are placed in the nuclear plant. Credits: Yann Arthus-Bertrand/Impact Photos

A tremendous amount of heat is generated when uranium is split. This fission process takes place in the core reactor of the plant. Water is heated into steam by the heat released through nuclear fission. The steam powers a turbine which drives a generator. This generator in turn supplies electricity to the electricity grid.[2]

The World’s Nuclear plants

At this moment, there are 442 nuclear plants. They together generate 2626 billion kWh annually. This is about 16% of the electricity generated in the world. A total of 65,478 tons of uranium are used by these plants.

Two large cooling towers in the background with two nuclear reactors up front.[2]

At this time 38 new nuclear reactors are in the planning phase and there are proposals for an additional 115. [3]

Types of Nuclear Plants

Many different nuclear plant types exist. Below is an overview of nuclear power types now in use

Reactor type	Main Countries	Number	GWe	Fuel	Coolant	Moderator
Pressurised Water Reactor (PWR)	US, France, Japan, Russia	265	251.6	enriched UO2	water	water
Boiling Water Reactor (BWR)	US, Japan, Sweden	94	86.4	enriched UO2	water	water
Gas-cooled Reactor (Magnox & AGR)	UK	18	10.8	natural U (metal), enriched UO2	CO2	graphite
Pressurised Heavy Water Reactor ‘CANDU’ (PHWR)	Canada	44	24.3	natural UO2	heavy water	heavy water
Light Water Graphite Reactor (RBMK)	Russia	12	12.3	enriched UO2	water	graphite
Fast Neutron Reactor (FBR)	Japan, France, Russia	2	1.0	PuO2 end UO2	liquid sodium	none
Other	Russia	4	0.05	enriched UO2	water	graphite
TOTAL		439	386.5

Bron: [4]

Temporary Storage

The core reactor is halted following its operation cycle to replace the fuel rods. The consumed fuel rods are highly radioactive and have been inside the reactor for an average of three to six years. These rods are then placed in a so-called spent fuel pool. The ruel rods must first cool down in these water basins. Water serves as coolant and as a cover for the highly radioactive radiation. This process takes ten to twenty years.[20][21].

Decommissioning

The nuclear plant must also be decommissioning in the final phase of its operation. This includes all organizational, administrative and technical activities required in closing down the plant and returning it to the green field situation.

The typical operational lifetime of a nuclear plant is considered to be 40 years. In rare cases the lifetime can be extended beyond the initial 40 years by 20 years at the most. However, the lifetime tends to be shorter due to economic, political and safety considerations. The average age of the 107 nuclear reactors shut down up to 2004 was 21 years. [12]

The costs of decommissioning a nuclear plant depend on the type of plant. The costs vary from $200/kWe to $2700/kWe.

Here is an overview of the costs associated with shutting down the various nuclear plants still in operation.

		Calculation decommissioning costs existing nuclear plants
Type	Cost per kW (Average)	Plant	Power (MW)	Cost ($)
PWR	$350	Daya Bay 1 (China)	984	344 million
VVER	$330	Balakovo (Rusland)	950	313 million
BWR	$425	Shika 2 (Japan)	1304	554 million
CANDU	$350	Bruce Power (Canada)	820	287 million
Gas-cooled	$2600	Wylfa Magnox (UK)	980	2,5 billion

Sources: [13],[14],[15],[16]

The price of uranium

The demand for uranium is currently larger than the quantity being mined. This shortage is currently filled by recycling uranium derived from the dismantling of nuclear weapens, primarily in Russia. Once all these weapons are recycled, analysts expect that despite higher production from new mines, a shortage of 22 million pounds will still exist in 2010. The current shortage is 25 million pounds. [11]

he price of uranium will rise substantially because of rising demand for uranium due to the construction of new nuclear plants.

The nominal price of uranium

Net Energy Output

Jan Willem Storm van Leeuwen and Philip Smith published very thorough research [5] of the net energy output that is actually produced if the entire nuclear fuel chain is taken into the calculations. The result of their calculations is shown in the graph below. The graph illustrates the energy cost and return of a nuclear plant. The sections of the lines in the white portion of the graph are the sections that return net energy.

Nuclear plant net energy production. Click on the graph for details. Source: [5]

The graph shows that even with the richest uranium ore available, it takes 10 years before a nuclear plant starts to produce more energy than it cost to build and run it up to that point. For uranium ore with a lower percentage of uranium the situation is worse still:

A nuclear plant no longer produces net energy for uranium ore with a uranium content of 0.05% or lower. The amount of energy required to run the plant is then greater than the energy that is produced.

CO₂ Emissions
The nuclear energy discussion usually involves the assumption that it is a good solution because no CO₂ is emitted. However, if you take the entire nuclear cycle into consideration a nuclear plant produces a significant amount of CO₂. The quantity of CO₂ production depends greatly on how rich the source of uranium is. The lower the percentage of uranium in the ore, the carbon dioxide emission you get.

The graph below illustrates the carbon dioxide emission of a nuclear plant as a percentage of that of a gas-fired plant against the grade of uranium in the uranium ore mined

CO₂ produced by nuclear power plant.Click on the graph for details. Source:[5]

The most favourable case in which uranium ore contains a very high uranium content the nuclear plant produces 33% of the volume produced by a gas plant, or 133 grams CO₂ / KWh.

That means that a 1000 MW PWR nuclear plant producing at a capacity of 90% (Cummins, 2004) produces 7.88 TWH of power and more than a million tonnes of CO₂.
If lower grades of uranium ore the carbon dioxide production increases accordingly.

If uranium ore contains 0.013% of uranium or less, the carbon dioxide production actually becomes greater than a gas plant, in other words, more than 3.15 million tonnes of carbon dioxide per year.

Longer term

Mines containing relatively high quality uranium ore are going to become fewer and fewer in the not too distant future. The average quality of ore being mined is almost certainly going to decrease. More and more mines with a relatively low percentage of uranium are going to enter production.

The result is that CO₂ production in the nuclear chain is going to increase and that nuclear plants are going to produce an ever decreasing amount of net energy.

The rising demand for uranium and the stop-gap recycling of nuclear weapons will eventually exacerbate the existing shortage and drive up the price of uranium further.

Safety (on paper)

A controlled form of nuclear fission is taking place continuously within a nuclear plant. This can take place thanks to continuous cooling and the use of a moderator. The moderator ensures that the neutrons that are released during nuclear are caught and or restrained. If this does not happen a chain reaction begins that can no longer be stopped. The reactor core then becomes so hot that it melts and leading to what is known as a meltdown. If that happens nothing can stop the process. The reactor core is exposed and nuclear material can escape. When the extremely hot reactor core comes into contact with ground water, an extremely powerful chemical explosion can occur that causes radioactive material to be flung out. This is known as a worst case scenario.

When a calamity happens a nuclear plant can be shut down. However, because of the extremely hot reactor core this shut down takes about 6 days. In this period it is still extremely important that the plant stays cooled and the moderator works. On paper most nuclear plants seem very safe. They are equipped with many sensors and safety systems. In addition to the primary cooling system there is always a back up system to cool the plant.

Safety in practice

In practice a lot can go wrong that is not taken into consideration beforehand.

Here are a few examples of very serious nuclear incidents:

March 11, 2011 – Fukushima Nuclear Powerplant Japan
An earthquake of 9.0 on the Richter scale and the ensuing tsunami damage the electrical systems in the plants. This causes the cooling systems to shut down. The diesel generators that the company also has for back up power are also rendered inoperable by the tsunami since the plant lies on water. Extremely hot steam leads to the formation of hydrogen gas. The reactor core is now so hot that there is a partial meltdown. More info: Fukushima I Nuclear Power Plan

April 26, 1986 — INES Level 7 – Prypiat (Chernobyl), Ukraine (then USSR)
Electricity shuts down, explosion and complete meltdown.

March 28, 1979 — INES Level 5 – Middletown (Three Mile Island), Dauphin County, Pennsylvania, United States
Partial meltdown.

May 1967 – Dumfries and Galloway, Chapelcross Scotland, United Kingdom
Partial meltdown.

The complete list of major nuclear incidents can be found here. List of civilian nuclear accidents.

Conclusion

All things considered, nuclear energy doesn’t seem like THE best option for our energy problem.

To summarize the above, nuclear energy is associated with the following problems:

• A nuclear plant starts producing net energy after 10 years of operation. In the case of low grade uranium ore a nuclear power plant will not even supply any net energy.
• The construction of a plant takes about 10 years, the lifetime is 21 years on average and it takes another 150 years before it is completely dismantled. All of this and a plant effectively only produces energy for 10 years.
• The average nuclear plant produces more than one million tons of CO₂.
• The price of uranium will rise significantly in the near future. This can only increase the cost price of nuclear energy further.
• A nuclear plant is safe on paper. However, practice shows that nuclear incidents cannot be avoided.