Nuclear energy

Nuclear energy

Secured storage

Breeder reactors

First nuclear reactor

Modern reactors

Safety concerns

Common elements

Uranium-238

LFTR

AHWR

Clean, renewable source

Fusion

Fusion reactor

Sustainable

Inertial confinement

Modular units

Market forces

Viable, alternative

Nuclear energy was developed first as a weapon of mass destruction.

Nuclear power station were primarily reactors, for producing weapons grade plutonium.

The accidents in Chernobyl and Fukushima highlighted the dangers of nuclear technology.

Since then nuclear energy is associated with destruction, and danger. 

The heart of the nuclear power station is the reactor.

In the reactor’s core, heat is generated by controlled nuclear fusion.

The conversion from nuclear to electrical energy takes place indirectly.

A coolant like water, is pumped through the reactor under pressure to draw off the heat generated.

The temperature involved is enormous.

Water is converted into pressurised steam.

This steam is fed into a multi stage turbine.

The turbine converts the heat into mechanical energy.

A generator converts the mechanical energy to electrical energy.

The steam cools down in a condenser, usually a water body, and the cycle begins again.

The process creates dangerous levels of radiation.

The reactor is surrounded by a protective shield, to prevent radiation from seeping out. 

The waste retains most of its energy potential and can be recycled as a new fuel.

Most reactors use a moderator to reduce the velocity of neutrons, 

and increase the probability of fission .

This allows lower concentration of fissionable material to be used, 

than used in nuclear weapons.

Fissionable material include uranium and plutonium.

Both of them can sustain a nuclear chain reaction.

A very small amount of material can produce a large amount of power.

A fissionable pellet, of the size of the little finger, can produce the same amount of energy,

as a tonne of coal.                                                                                                               

The best moderators are heavy water and graphite.

They are full of atoms, with light nuclei, which do not easily absorb neutrons.

Reactors using this materials can run using natural uranium.

Ordinary water is also used as a moderator, since it is cheap and plentiful.

This absorbs too many neutrons.

These reactors can be used only with uranium 235.

This is a rare isotope of uranium.

Ordinary uranium has to be enriched, to get uranium 235.

This adds to the cost of production.

The depleted uranium, after the enrichment process, is considerably less radioactive,

then natural uranium.

But it is still extremely dangerous, and has to be kept in secured storage.

During the nuclear reaction the fissile isotopes are consumed.

What remains is called nuclear fission product.

This is considered as radio active waste.

The spent fuel is hazardous, but very small amounts are produced.

Some reactors use fast neutrons.

They require higher concentration of fissile isotopes.

These breeder reactors, produce more fissile material than they consume.

Initially the effects of radio activity was completely misunderstood.

Since they produced their own energy, it was concluded that they have health giving properties.

Radium was added to toothpaste, bath salts, and even medicine.

Thousands of regular users died due to the radiation.

Harnessing atomic energy to generate electricity was regarded as quackery.

Even Rutherford dismissed the idea as moonshine.

Italian physicist Enrico Fermi carried out the first successful experiment, 

which signaled the start of the nuclear age.

He arranged pellets of uranium and blocks of graphite, in a carefully planned geometrical structure.

This set up called the Chicago pile one, was the world’s first nuclear reactor.

On 2nd December 1942, it created a nuclear reaction, and produced half a watt of electricity.

Generating electrical power was not the priority  for Fermi.

The aim of his team was to make a nuclear bomb.

This was the driving force, which later led to nuclear energy.

After the second world war, the civil use of nuclear energy was advocated.

The scientist Hyman, recognised the potential advantage, 

of nuclear over diesel as fuel for submarines.

Internal combustion engines required air delivered by a snorkel.

This severely limited dive times.

A nuclear powered submarine could stay submerged for years at a time.

The reactor created to power this new generation of submarines, was more compact.

It used light water as a coolant and a moderator, instead of the rarer heavy water.

Even under high pressure liquid water cannot be heated above 350 degree centigrade.

To makeup for this poor moderation, this reactor require enriched uranium fuel.

This was typically 3%, U-235.

The process of enrichment of uranium is the same that is required to produce nuclear bombs.

For several years the technology was locked into pressurised water reactors.

One of the alternative technologies discovered, which was not fully exploited, was the breeder reactor.

The breeder reactors burned and produced plutonium. 

This led to the widely held assumption that they would be able to produce their own fuel.

The first experimental breeder reactor was built in USA in 1951.

It generated enough electricity to power four light bulbs.

Light water reactors account for 359 of the world’s 430 operational nuclear power plants, in 2012.

Within the reactor nuclear fission occurs when a fissile nucleus is split by a neutron.

This releases for further neutrons, which go on to split further nuclei, in a chain reaction.

Modern reactors produce five gigawatts of electricity.

This is equivalent  to 5 Hiroshima bombs everyday.

The world’s first commercial nuclear reactor opened in 1956, in UK.

Since then nuclear energy grew rapidly.

It reached 300 gigawatts in the 1980’s.

It grew slower after that and reached 370 gigawatts in 2012.

Some countries heavily dependent on petroleum for electricity, 

significantly increased their nuclear energy capability.

For example, 30% of Japan’s energy, and 80% of France’s energy is nuclear.

Nuclear power plants have their own dangers.

During the Earthquake and Tsunami in 2011, 

there was a meltdown in the Fukushima nuclear reactor in Japan.

Following this accident many countries, scaled back their nuclear program.

Japan itself shutdown all but two of its nuclear reactors.

Accidents like Chernobyl and Fukushima, highlighted the dangers of nuclear energy.

20000 people died in the Tsunami, but not a single life was lost in Fukushima.

Yet the concerns persists. 

Modern nuclear reactors are much cleaner than the earlier ones.

In fact coal fired power stations produce more nuclear pollution.

Coal contains uranium which is released in the exhaust gases, and is concentrated in the ash.

There are inherent health and safety concerns  in nuclear power plants.

Reactors have to be continuously cooled. 

They can potentially overheat and even explode.

The buildings housing the reactor, have thick steel enforced concrete  shells.

But they are not fool proof.

To prevent runaway nuclear fission reactions control rods are used.

Boron or cadmium control rods are inserted into the core of the reactor.

They absorb the neutrons.

Such measures aim to make the reactors more safe.

In the case of an accident, the widespread dispersal of a large amount of radioactive substances,

can be a major hazard.

It can enter the food chain, cause illness or even death in humans.

If nuclear proliferation continues, it will place a great demand on limited supplies of fresh water.

Using sea water has the disadvantage, because of its highly corrosive nature.

Nuclear plants located in seismic zones, face the danger of earthquakes.

Atomic power cannot be made fully safe or infallible.

We are learning from past experience, to make nuclear reactors more safe.

Uranium is a fairly common element. 

It is as plentiful as tin, and 40 times plentiful more than silver.

Unfortunately, these are spread over evenly, rather than concentrated together.

This makes the recovery uneconomical in many cases.

Even then, the amount of economically recoverable Uranium is enough to provide us, 

with a century’s worth of fuel at the current rate of consumption.

Our current light water reactor technology uses this fuel inefficiently.

It is only able to function using the rear Uranium-235 isotope.

While recycling can make this fuel go further, there are much more efficient reactor designs,

than what is used now.

Fast breeder reactors use Uranium-238.

This makes up about 98% of natural resources.

The breeder process is so efficient that it is estimated, that we have enough fuel for 5 billion years.

The technology is not perceived to be economically viable.

The price of fuel is insignificant compared to the overall cost of a nuclear power plant.

The capital cost of a breeder reactor, is about 25% more than a water cooled reactor.

Reprocessing the fuel in a breeder reactor is very expensive.

The only such reactor producing electricity now is in Russia.

Another alternative would be to use Thorium as a fission fuel, to breed Uranium-233.

Thorium is 4 times more plentiful than Uranium. 

It is as common as Lead.

About 36% of the recoverable reserves are in India, Australia, and the U.S.A.

Thorium based fuels have several attractive advantages over Uranium.

Thorium reactors are forecast to cost far less than light water reactors, 

because of the simplicity of their design.

One technology that has been tried is the liquid fluoride Thorium reactor, or LFTR.

An LFTR can be factory assembled, and scaled down, to fit into a truck.

They are much safer.

The core of the LFTR is unpressurised.

Any increase in temperature results in reduction in power, rather than a run away melt down.

If the reactor does overheat a salt plug at the bottom melts away.

This dumps the fuel in a storage container below the reactor.

LFTR produces thousand times less waste than Uranium.

About 83% of the waste is safe within 10 years.

The rest would require 300 years of storage.

This is much better than the 10000 years, required for nuclear waste, produced by light water reactors.

The Nuclear power corporation of India announced the setting up of,

 an Advanced Heavy Water Reactor, (AHWR).

It will produce electricity from Thorium.

The technology remains unproven as of now.

India has ample reserves of Thorium.

Once operational this will produce 300 MegaWatts of power.

The reactor is supposed to be so safe, that they claim that it could be built in the heart of a major city.

The potential of Thorium is great. 

The biggest barrier to its emergence is institutional inertia, and market economics.

It is far easier and cheaper to licence an existing inefficient, but proven design.

This is regardless of the safety and environmental shortcomings.

The AHWR in India will determine whether Thorium will  deliver on its promise.

The history of fission highlights the danger of engineering compromise.

Nuclear energy has been the preserve of the military.

Civil objectives are subordinate to weapon production.

Had the primary consideration at the outset had been mitigation of risk, 

then our nuclear reactors today would be completely different.

Nuclear energy might actually be a clean, green, renewable source of energy.

Thorium research is being driven by China and India, 

whose civil objectives are more important than the military objectives.

Fusion is the power generated when two light atomic nuclei, 

fused together to form a heavier nucleus.

It releases a huge amount of heat, previously locked into the binding energy of the strong nuclear force.

In our sun, fusion occurs when two super heated hydrogen nuclei, 

in plasma collide to form a nucleus of helium.

Fusion is the most sufficient means of producing energy.

There is so much energy locked in by the strong nuclear force, 

that despite the vast amount of heat produced, 

little actual mass or fuel is lost.

This is the reason, why the sun has continued to burn for 5 billion years,

and why it will burn for 5 more billion years.

The fundamental science behind fusion, is no more difficult to understand than fission.

Initial research into thermonuclear fusion was initiated by the U.S. military, 

with a view to producing more powerful weapons. 

The atomic bombs dropped on Hiroshima and Nagasaki were based on fission technology.

In a more advanced hydrogen bomb, the energy released by fission reaction, 

is used to compress and heat the fusion fuel to begin a fusion reaction.

This releases a huge number of neutrons, which in turn increases the rate of fission.

The energy produced in a fusion hydrogen bomb is 500 times greater, than in a fission atomic bomb.

To emulate stellar nucleosynthesis here on Earth, 

and produce a sufficient number of fusion reactions in plasma, 

we need to recreate both the massive solar gravitational pressures and temperatures,

which are 10000 times hotter than the centre of the sun.

Plasma is the fourth state of matter. 

Fusion requires 2 heavier isotopes of hydrogen, deuterium and tritium

Deuterium contains a neutron as well as a proton.

Tritium has a proton and 2 neutrons.

In the fusion reactor these atoms fused together to form a helium nucleus,

and release one of their neutrons.  

The energy released is used to heat steam and produce electricity.

This is the same as traditional power stations.

The helium nucleus transfers its energy to the plasma, which keeps it hot.

Confining this hot plasma is the biggest challenge.

The high temperatures preclude direct contact with any solid material.

This means that it has to be confined in a vacuum.

But  high temperatures come with high pressures.

To prevent the plasma from immediately expanding into the vacuum, an additional force is required.

The necessary gravitational force is found only in the heart of stars.

On Earth confinement can be provided by a very strong magnetic field.

This would be magnetic confinement fusion.

Another way is by getting the fusion reaction to occur before the plasma starts to expand.

This would be inertial confinement fusion.

Inertial confinement fusion is the process used in a hydrogen bomb.

A rapid pulse of energy is applied to the surface of a fuel pellet.

This causes it to implode to a very high pressure and temperature.

If the fuel is dense enough and hot enough, 

its inertia will keep it together, and fusion rate will be high enough, 

for a small fraction of it to burn, before it is dissipated. 

In an hydrogen bomb this pulse of energy is provided by X-rays,

released during the fission reaction.

In a controlled fusion reactor, the driver can be a laser, ion, or electron beam.

It can also be a Z-pinch, which uses an electric current in the plasma,

to generate a compressive magnetic field.

The sun’s longevity is testament to the fact, 

that fusion has the potential to provide a sustainable solution,

to the world’s energy needs.

The only raw material needed for fusion are water and lithium, in small quantities.

Fusion can provide a continuous power supply, with effectively limitless non-radioactive fuel.

It produces no green house gases, no pollutant and no long-lasting radioactive waste.

To get 7 billion kilowatt hours of power, from a coal fired power station,

would require 1.5 million tons of fuel.

To generate the same amount from a 1000 megawatt fusion power station, 

would consume only 3 tons of lithium, and 100 kg of deuterium.

The International Thermonuclear Experimental Reactor in France, 

is designed to produce 160 megawatt of power.

It uses magnetic confinement technology.

Inertial confinement is more difficult to achieve.

Some regard it as infeasible.

Optimistic reports suggest that a pilot plant could be producing 100s of megawatts, 

in the 2020s  or 2030s.

It is believed that commercial power production from fusion, 

would happen only in the second half of this century.

Nuclear energy is the only one that we can be certain, 

would be able to provide as the amount of power we require.

However, safety concerns has been significant enough, 

to deter public and private investment.

As of 2012 there were 439 operational nuclear power plants, in 31 countries.

60 more were under construction in 14 countries.

To get near 10 to 20 terawatt of power we need, we will require 11000 of them.

To provide nuclear power on this scale we will quickly exhaust all accessible supplies of uranium.

We could use plutonium as a raw material, which would require 10000 fast breeder reactors. 

They would have a life span of just 50 years.

It is unlikely that we will build so many reactors.

This does not mean to be the end of the nuclear story.

Rather than making large nuclear reactors, we might consider making them much smaller. 

Modular units producing 100 megawatts could be constructed in a factory, 

and shipped to wherever it is required.

It will bring down production costs.

It could also improve safety.

Fuel rods needs to be produced in different factories.

Modulation would bring numerous benefits.

It will be more flexible.

Small towns might require only one 100 megawatt plant.

A large city requiring 1 gigawatt, could install ten,  100 megawatt modules.

A more realistic target would be a 3 fold increase in global nuclear capacity in 50 years.

This would replace 700 GW of coal fired power.

It will reduce annual carbon emissions by 3.7 billion tonnes.

Germany is not alone in abandoning its nuclear program.

France and Japan are likely to scale down their nuclear program.

For many countries, the energy security offered by power stations, 

running on a cheap and plentiful fuel, will be a very attractive proposition.

We need to give up the idea, that one single low cost energy resource,

is going to replace fossil fuels in the next 3 to 4 decades.

Any substitutional fuel is going to be comparatively expensive in the short to medium term.

Market forces are not going to influence matters, 

till we have exhausted supplies of cheap fossil energy.

For this reason alone nuclear power is sure to remain in the domain of politics and government.

From the birth of civilisation to the turn of the 20th century, 

the dominant fuel was bio mass, wood, crop residues and charcoal.

On a global scale, coal became the primary energy source only in 1900’s.

Coal was in the top position, for 50 years before it was overtaken by gas and oil.

Oil itself will lose its prominence to natural gas.

Fracking technology will liberate pent-up supplies of natural gas.

It will take several decades to get solar power upto capacity.

In the mean time, nuclear fission energy remains our only viable large scale alternative to fossil fuels.