Episode 8 Bang Goes the Theory

Her law and welcome to the show. Sadly, the last of the series. I am

in a blustery Hinkley Point in Somerset, home to three generations

of nuclear power station. Over there, you can see Hinkley Point be,

which is currently generating power and supplying 1 million homes in

the UK. Hinkley Point Bay is being decommissioned. In that empty space

behind that is the proposed Hinkley Point C, the new nuclear power

station, get to be built, that will generate power for 5 million homes.

In March, a group -- the reported on the tsunami which hit Japan

resulting in the loss of 15,000 lives, damaging the Fukushima

nuclear reactor. It is that incident which came to dominate the

headlines. But how much of the science behind those headlines do

we understand? Tonight's show, we're going to one of Britain's

oldest nuclear sites, to get to that on the issue of what to do

with nuclear radioactive waste, Liz looks at the effect of radiation on

us for help, and GM gets to the heart of the matter by showing us

how a nuclear power station actually works. I am about to do

something almost nobody ever gets to do. Goal inside a nuclear

reactor. Built inside -- in 1978, this one is almost identical to the

Fukushima reactor, except it was never switched on. You walk into a

nuclear power plant, you cannot help but be awestruck by the size

and apparent complexity of the place. But the truth is, when you

get to the heart of the operation it is all surprisingly simple. All

of this complex machinery is here to monitor and control the nuclear

reaction that he's water and turns it into steam. Once the steam

leaves the reactor, you're in the realms of conventional power. Hawke,

high-pressure steam comes down to write like this and gets fed into a

turbine. There, the technology is not so much nuclear but Victorian -

the pressure of the steam pursues the Blades of the turbine, causing

us to rotate. That turns a generator, which produces

electricity that this plant was built for in the first place. A big

problem I find with nuclear power- station as us that this year -- the

scale of them makes them confusing. But it boils down to this. You have

a nuclear reactor here, it is like a kettle, except the water is not

heated by electricity but by nuclear fuel rods. Oil and water

produces steam. Steam comes down a pipe and impacts on a turbine,

which is essentially a bunch of spoons, on a spindle. That reduces

electricity, and you have got yourself a happy town. The thing

that makes a nuclear power station different from a conventional one

is how the water is heated to form steam. To see that, I have to go

This is the heart of a nuclear reactor. Not many people get to

stand you, because, when active, all of this would be around 300

degrees Celsius. And under a similar pressure that you would

find half-a-mile below the ocean, pushing the walls apart with the

force of 40,000 tonnes. Where does the energy come from to do that? It

These are nuclear fuel assemblies. If operational, this small space

would be packed with 100 of these. Each giving out a vast amounts of

energy in the form of heat. That is because every one of these square

metal tubes would be packed with thousands of little pellets like

this, made of uranium oxide, and uranium is very special to us,

because it is an atom that we can split. When things break apart,

they release the energy stored in whatever was holding them together.

It does not matter if that is an atom or stretched elastic band. We

are going to come in, split it, and what I end up with, is two smaller,

high energy elements flying off in different directions. When that is

an atom, they smash into their surroundings, warming things up. No

matter how small the scissors, they are not the tool for splitting an

atom. To do that you need a small particle called neutrons. When this

hits the centre of a uranium atom, it gets absorbed, causing the atom

to become unstable, and to split. As well as releasing that energy,

you release two or three more neutrons that can fly off into the

surroundings, causing more trouble. That is still not really enough to

sustain a nuclear reaction. Uranium atoms do not absorb neutrons that

easily. Neutrons have to be going at just the right speed, and, for

that, this reactor needs one more thing. Just add water. The water

plays a pivotal role, because it slows down the neutrons, to a speed

where they are more likely to be absorbed by a near banning uranium

atoms, causing them to become unstable, releasing more energy and

more neutrons in a cascade. If you can keep the sustainable, you have

gone critical. Which is a good thing, because, then, you generate

heat sufficiently quickly to run a So, what was it that went wrong at

the Fukushima reactor? To find out, I headed back to the workshop, for

some experimentation. This is pretty much what created those very

dramatic explosions. An unfortunate mixture of hydrogen and oxygen

coming into contact with something hot. The big difference is, there's

involved about 1 million times more hydrogen, and risked splitting more

than my eardrums. But, what possible cause of events could have

resulted in a nuclear power station is up -- releasing one ton of

hydrogen? In the case of Booker shimmer, a massive air quicks

struck and all the main power went out. -- earthquake struck. These

reactors are fitted with an automatic brake, and in the case of

an emergency, neutron absorbing Broads are inserted between the

fuel rods, shutting down the main reaction. But the bad news is, you

cannot just totally switch of a nuclear reactor, because all the

time it had been working, to uranium would have been producing

several radioactive by-products which continues plotting and giving

of heat, long after the main reaction has been shut off. This is

known as decay heat. Even though it is 1.5% of the normal running power

of the reactor, it's still equates to about 20 megawatts. That is the

equivalent of having 10,000 kettles boiling away in there. Even 10,000

kettles were up of heat is not a problem, providing you have plenty

of water circulating through the reactor, taking that heat away.

Even after the earthquake, the pumps pumping the water were still

working fine, running off back-up generators, but then this tsunami

hit, wiping out the back-up generators, and the electrical

switchgear. This meant there was no water circulating through the

reactor, and, just like this cattle, it was beginning to boil dry. --

this careful. -- kettle. It just gets hotter and hotter. Soon, in

the reactor, the temperature reached 1200 degrees Celsius. At

1300 degrees Celsius, something even more serious started to happen.

Surrounding uranium fuel pellets is a metal called zirconium. And that

is then temperatures, it begins to chemically react with this steam

inside the reactor, producing an extremely flammable gas, hydrogen.

Now you have got fuel and hydrogen building inside the reactor vessel,

and the pressure is increasing dramatically, leaving the engineers

with an extremely difficult dilemma. Here is a model we have made to

demonstrate the problem. This is my reactor core. I am going to pot

that inside my nuclear plant. Inside the model, I have put some

reactive metal to simulate zirconium, and, if I add some acid,

it will produce hydrogen gas, in much the same way, and I recruited

their problem. Already, that is getting dangerously high, which

leaves me in a similar position to the Japanese, and I've got to

release the pressure now, because the worst-case scenario is, that

reactor vessel burst, because of the pressure building up inside it.

The workers at Fukushima avoided the worst case scenario, the huge

reactor core itself bursting under pressure, spring superheated

nuclear material at. But some of the gases released into the chamber

flowed back into the building, and created a new danger. That gas is

hydrogen, and when it mixes with air, and comes into contact with

any kind of spark, you have a Ooh! Dramatic and powerful as a

higher rate -- hydrogen explosion is, it is just rapidly burning gas,

and it is reassuring to know that even with an horrendous natural

disaster, the were enough control measures built into the plant that

engineers could stop the excess pressure Breaston the reactor would

sell up. The materials used in nuclear power mean that these

places can never become a nuclear bombs. This is the beautiful old

pink -- Hinkley Point is a control room. It is being closed than now.

But that is not the end of the story. Ahead lie years of

decommissioning. The reactor core is set to remain on site for the

next 100 years. That raises the most contentious issue when we talk

about nuclear power, whether it is an ordinary operation like Hinkley

Point, or the result of a disaster like Fukushima or Chernobyl, what

can we do with the radioactive waste? I went up to the far north

of Scotland, to find out. After a tour to five years of service, doom

racer that -- nuclear power station was decommissioned in 1994 --

Dounreay. Nuclear reactors always produce radioactive waste. That can

range from the contents of the reactor core, to anything in the

plant that becomes contaminated with radiation. Current figures

show that in the UK, we have well over 160,000 tonnes of the staff,

and something needs to be done with it. At Boon Rae, at 2.2 billion pan

clean-up was under way. But after six years, they are still dealing

with the lowest level waste, contaminated paper, rags, and tools

which must be steeled -- sealed into steel drums and painstakingly

analysed. There is more low-level waste than anything else, and some

of it is barely radioactive. Inside the reactor core itself lies a more

serious challenge. Where I am walking here below my feet is the

reactor. Inside the reactor core, is some very hazardous radioactive

material, uranium and plutonium. The big challenge is to get it out

and make it said. This final stage of the clean-up is due to start

next year. Handling this waste will be so hazardous, they are

installing Roberts, ready to do the job run madly. -- robots. --

remotely. First, you remove the fuel from the reactor. This

sophisticated mast has 14 different tools on it which can cut free the

elements in the reactor. It is like a big Swiss Army knife. It is a

huge Swiss Army knife that is designed to work remotely and

reliably. That gets rid of all the fuel in the system. Once extracted,

the pure words are put into a cell containing an automated dismantling

robot. For now, the row was practising with pretend fuel rods,

but once active, it will handle the It is unlike lie we will put anyone

in here again. Another row Bott will transfer the fuel into stain

less steel drums. These drums will go into an underground area under

controlled conditions and be stored there forever. But at Dounreay the

clean up isn't the only challenge. In the 1960s things didn't go to

plan and in a series of accidents thousands of particles of waste

were flushed into the sea. The task now is to recover as many as

possible, one by one. It shouldn't have occurred. We have released

radioactive material into the environment and it is now

uncontrolled. The risk would be a fish ingesting a particle and

getting into the food chain. That was the concern. These particle

will be on the sea bed, in the sand. So the fish would have to eat the

sand. However there was a possibility that they could get

into the food chain and therefore some one could be exposed to it.

The parms are tiny fragments 06 spent fuel -- particles. The team

used a remotely operated vehicle. The challenge is to scan an area

the size of 500 football pitches. As soon as they detect something it

will stop and drill down. They will target it and then just drill down,

suck up a mixture of sand and water. So it is base clay big vacuum

cleaner. Yes. The robot returns to the surface and the canisters of

sand are unloaded for screening. So he is going through all the sands.

Spreading the sand out and monitoring it. You can hear from

that noise that they have found something there. So we divide the

sand down, and check each bit to find the particle. It is there!

So it is in there. You will monitor 60 hectares wrt of sand. Every

grain? Yes with the ROV and any sand that comes back here that

again will be monitored to make sure it is clean before it goes

back to the sea. The radiation given off by these particles can

penetrate human skin. But as the workers never touch it, they're

safe. We know about the particles that are out at sea, is there a

risk of getting particles here on the beach? In any two week survey

we may find two or three. So you are talking three or three

individual grains of sands from all of this sand. If somebody came into

contact with a particle, on the beach. What would happen to them sh

The most likely way come into contact with it is if you got it

stuck on your skin. A couple of days later, you would get a

reddening on the skin, like a burn and that would heal up. That would

be it. But long-term it gives you a risk of developing a cancer. Not

that you will, but there is a risk associated with with radiation

exposure and cancer. I suppose that is what it comes down how to,

however slight a link between cancer and radiation from a reactor

like this might be, it is enough understand tpwhroi generate a sense

of fear in all of us and of course the press. But we weren't always so

nervous of radiation. Once radioactivity was positively

celebrated. It was a fashionable label and radioactive water was

seen as a cure for all ills. But This footage was taken during the

aftermath of the atomic bomb-blast in Japan and the images are

unsettling. Not only because they're a reminder of thousands who

died, but also because these events started a fear of radioactivity.

Since the atom bomb-blast it has been difficult to make a

dispassionate assessment of the dangers. But that is what I want to

do and wipe the slate clean and find out the truth about the

effects of radiation. Jerry Thomas is an expert on the 1986 chorl

disaster. I have asked her to put the number of deaths into

perspective. -- Chernobyl. Everyone knows about the bombings in Japan.

A lot of people died, but most of the population died from the blast

injury. Actually only about 15 to 20% of the people who died as a

result of the bombs died because of radiation. You're talking about

20,000 deaths from radiation. So where do we go? Let's look at

something else. This is the figure of people that were killed as a

result of a dam burst in China in 1975. The dam was there to provide

Hydro Electric power. Does puts it into perspective. Now something

that we do to ourselves and this is cigarettes. This is the total death

toll for 2009 for lung cancer or the other smoking-related diseases

that result in death. Lower down the scale, Jerry says over 2,000

people died in road accidents in 2009. But perhaps most surprising

is her next figure. How about falling out of bed. 106 people each

year fall out of bed. Seriously? Yes. 106 people each year fall out

of bed and die as a result. That is desperate, I didn't mean to joke

about it. It serve serves to make you paranoid about everything.

that is the point, life is risky. So where does Chernobyl fit in?

think I might be shocked. I think it will be less than car crashes.

You're right. I think this is will be a surprise to you. Somewhere

between the number of people who die falling out of bed and the

number who die in car crashes. thought it would be closer to 2,000.

It is remarkable how much lower the death toll from radiation at

Chernobyl is than that in Japan. According to Jerry, that figure

includes both the short-term effects of acute radiation sickness

and most cancers. So the main thing is not to make the mistake of

associate Agnew clear accident to something like an atom bok. The

numbers illustrate. Figures suggest that radiation from accidents like

Chernobyl is not as worrying as a lot of the media coverage would

have us believe. But it can and does kill. And I want to understand

how. I'm meeting Dr Susan short to show me who radiation can do. Here

they grow human tissue cells and expose them to X-rays. This is the

machine. This is the X-ray machine. The beam has energy to irrate yaid

-- irradiate the cells. We switch the machine on for various lengths

of time. Using sum pls, Susan investigates how radiation damages

cells. We have got cells that we were growing in a dish and we have

two sets. This is a group of cells that have not had any radiation.

Each of the dots is a surviving group of cells. That is a group of

cells. Cells growing well. Yes. This is the same cells that have

had a dose of X-rays. Just one dose. It is a marked difference. A lot of

cells died. The reason X-rays can kill cells, because like the

radiation from a power plant, they cause a process called ir

yonisation. That is -- Ionisation. That is a lot of energy and it

producing electrons and free radicals that can damage other

proteins. And it can make its different for the cell to function

The X-ray beam comes out of the head 069 -- of the machine.

machine limits damage to healthy cells. All cells they touch are

affected. But because the machine rotates, healthy cells get just a

brief dose and the tumour is repeatedly exposed. So you build up

the dose and avoid that? Mind yourself. Chris is incredible. The

work of radiotherapists means we're learning more about the effects of

radiation on our health. And already lessons learned from

Chernobyl have had an astonishing effect on the human cost of Japan's

nuclear accident. In Fukushima, what was the death toll? There

won't be a death toll from radiation in Fukushima. Because

they have done all the right things, they read the book and acted as

they should have done. There won't be a death toll in Fukushima and I

would be surprised if anybody loses their life as a result of exposure

to anything from Fukushima. So I hope we have given you some food

for thought. But the bottom line is there are no real easy answers when

it comes to discussing nuclear energy. We have all got strong

opinions the Government is releasing a report into the future

of the UK policy in the next few weeks. We have come to tends of the

show and the series. Before we go, look online. Dr Yang has done a

film about carbon dates. There a lot about nuclear power and

Fukushima. Also the BBC is looking for amateur scientists. Look at

that competition. That is its for this series and thank you for

joining us. It has been fantastic. A treats before you go. If you're

one of the people who haven't seen Bang live, we record a show that we