Imagine if you could harness the sun and power the entire world with its unlimited energy.
Since the 1920s, scientists have raced to recreate exactly that, a star on Earth.
Inside these walls, scientists have been trying for decades to create an unlimited source of energy.
Well, virtually unlimited. And that's energy that doesn't emit any carbon or long-life radioactive waste.
Scientists argue that fusion could replace coal, gas and nuclear fission in the energy
mix alongside renewable energy, which can prove to be unreliable.
This could help to significantly lessen our carbon footprint.
If we can learn to control it, nuclear fusion could change life as we know it.
But that's a big if.
Dozens of scientific projects have fought to make commercial nuclear fusion a reality.
But none have succeeded.
Now the biggest home is sitting in the UK in Oxfordshire. The project is called JET.
And there have been big hopes for JET since 1984.
In an energy-hungry world, the JET may be a step along the road
towards a virtually unlimited source of electric power.
JET is paving the way for a bigger nuclear fusion reactor experiment in the south of France.
It's called ITER and it's funded by 35 different countries.
The reactions happen inside a machine called a tokamak, an anagram from the Russian phrase,
meaning toroidal chamber with magnetic coils.
The doughnut-shaped, sci-fi looking machine heats up to be 10 times hotter than the sun.
To make the reaction on Earth, we need very high temperatures.
On the sun we have a temperature of only 15 million degrees,
but right here in the heart of the machine, it's 150 million degrees.
The walls look like metal, but in fact, are huge graphite magnets to keep this plasma contained.
In the heart of the machine, hydrogen atoms smash together at high speed,
releasing a huge amount of energy in the form of plasma.
5, 4, 3, 2, 1, 0.
Fusion does generate radioactive waste, but it can be recycled and reused within 100 years.
In fission, it takes between 1000 to 10,000 years to break down.
Humans can't enter a tokamak because it remains radioactive after fusion tests.
So, robots carry out upgrades and repairs.
I can feel the vibrations through the arm at the moment.
It's a really extraordinary feeling because it's almost as if my hand were exactly this pincer,
I can see it moving 100 to 200 meters away.
It takes years to train human operators to control these robotic arms under pressure.
This is just my second month in training.
Dropping anything could dent or damage the invaluable equipment.
It's the highest stake arcade game ever, and you need to win every time.
When you think about what can go wrong with nuclear energy,
your mind might go to explosions or weapons of mass destruction.
With fusion, the problem isn't containing the reactions, it's maintaining the reactions.
Conditions have to be just right for the hydrogen to fuse with each other.
And if anything goes wrong, the spark will simply extinguish.
Nuclear fusion is going very slowly for a number of reasons.
One is that is scientifically, it's very complicated.
But secondly, it's also politically, let's say... not very easy.
So each time we build a machine like JET or ITER,
the politicians are talking to each other for five, six years.
Each time that gives an additional delay.
The ultimate challenge for scientists at JET is to keep the reactor going for over five seconds,
beating their own world record.
Five seconds might seem like a ridiculously low figure, but it's not.
These five seconds could meet the electricity needs of 20,000 people.
In this room, there's a direct phone line to the electricity network
serving Great Britain, the National Grid.
And it's important JET and the National Grid keep in touch.
Anytime the UK needs a surge of energy to cope with high demand, JET simply can't run.
There are no tests during the Champions League Final.
No tests during the final episodes of EastEnders, that's how much energy JET uses.
For now, JET consumes far more energy than it produces.
And that's a problem. A nuclear fusion power plant will have to produce more energy than it uses.
Otherwise, it's not worth bothering.
DEMO, an even bigger experiment that will follow ITER,
will be the scale of a modern electric power station.
It will have to produce around 25 times more power than is needed to heat it.
The sheer amount of wasted energy on plasma testing alone is concerning.
Some may argue that nuclear fusion has missed its moment.
Twenty years ago, renewable energy was not as cheap or available as it is now.
In the near future, it could reasonably make up the majority of the UK's energy mix.
So, why bother building extremely expensive energy-guzzling machines,
when that money could be dedicated to something else?
The truth is experts have said time and time again that it's 20 years away from being a reality.
Some believe this is still too optimistic.
Afterall there have been no incidences of energy from a tokamak being fed back into the grid
and if it finally happens, it might have already been made redundant by other technology.
For now, the appetite for fusion has reached new heights.
And scientists at JET hope for a true breakthrough in their lifetimes.