'You get more radiation flying than standing on our reactors': Secrets of a nuclear power station revealed during a tour of a plant where health and safety notices are NEVER ignored 

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When things go wrong at a nuclear power station, it can be a total disaster.

This has led to the perception with some that even popping into one is a risky endeavour. However, MailOnline was given exclusive access to EDF’s Torness nuclear power station on the east coast of Scotland – and didn’t come out glowing.

One of the lead engineers there pointed out that in fact flying exposes you to more radiation than standing on top of one of its two reactors.

Hot stuff: This is Torness's reactor No2 with a fuelling machine in the background. Inside both reactors nuclear fission occurs when uranium atoms split to produce heat

Risk-free: Inside the reactor is uranium dioxide fuel in stainless steel tins, carbon dioxide coolant, a graphite moderator and metal control rods. Standing on top of this reactor is totally safe

Nerve centre: This is the Reactor Two control desk in the Central Control Room. Those who work here go through a rigorous two-year training course on simulators first

Computer power: The Central Control Room is manned 24 hours, with operators there able to manually shut down reactors. The reactor desk engineer has a very important job and must not be distracted, hence you need special permission to enter this room

Complex: These two pictures show some of the buttons up-close in the Central Control Room, an area that requires the utmost concentration at all times

Sneak peek: MailOnline was given exclusive access to the Torness nuclear facility, which can be found on Scotland's east coast

Ian Cathro, Special Projects Manager at Torness, said: ‘My biggest dose last year was flying to Grenada. This is because on a flight you’ve got less atmosphere protecting you from cosmic rays. Spacemen get quite high doses.

‘Anyone living in East Lothian gets two and a half millisieverts of radiation [that’s a measure of the absorption of radiation by the body], just from background radiation. The national limit for workers is 20, we operate to a level of 10, but our action level for investigation is five.’

These facts certainly put the mind at rest, as does the sheer technological prowess of the plant and its team of highly skilled workers.

Mr Cathro said: ‘We get some students coming here with a slightly negative view of nuclear energy. But they invariably feel better about it once they’ve seen the technology, the sheer physical size of it. The people working in the control room in a totally cool, calm and collected manner. That puts their minds at rest.’

Visitors to the plant, which produces enough electricity for two million homes, are also reassured by its incredibly strict health and safety rules. For example, even walking down a set of stairs without holding a handrail is a no-no.

Mr Cathro, who has a degree in physics from Glasgow University, said: ‘If you see someone not doing it, you’ll politely coach them.’

Power house: Two maintenance technicians in the Turbine Hall, where the electricity is produced

Complicated: There are a lot of pipes in the Turbine Hall. The turbines are the light blue machines, the generator the darker blue machine next to them. The turbines, powered by superheated steam, rotate at 3000 revs a minute and in turn spin the rotor in the electrical generator which produces enough electricity for around two million homes ( one million per generator)

Cold facts: This is one of Torness's four cooling water pumps, which pulls seawater in through 'drum screens'. The water is driven through a condenser and back to the sea

Size matters: Two technicians study the huge fueling machine in the Charge Hall. The fuel is uranium dioxide pellets clad in stainless steel, which produce 1600 megawatts of heat in the reactor

Heavy metal: Technicians manoeuvre the huge fuelling machine into place. Pictured right is Keith MacLennan, an Operations Fuel Route Technician

Twins: Torness has two gas reactors. This is Reactor No1, which is identical to Reactor No2

Keeping a lid on it: The reactors are sealed by a 'pile cap', so called because the first ever nuclear reactor was built on a squash court in Chicago and it was referred to as a ‘pile’ by those who built it. It provides shielding and physical protection

EDF is keen to point out that the biggest risks to safety it has at its nuclear plants is slips, trips and falls.

Exposure to radiation does happen at Torness, but it’s normally very low level. Mr Cathro revealed that he’s never experienced dangerous levels in several decades of work with nuclear processes – though he did once have his trousers confiscated.

He said: ‘I’ve worked in the industry for 40 years and once in Hinkley Point, I had slight contamination on my trousers. So I went home in a boiler suit. But I got the trousers back the next day because it was natural radiation.’

The plant at Torness, which lies 33 miles from Edinburgh, is divided into two sections – a conventional area containing generators and pumps, and the nuclear side, where heat is produced from splitting uranium.

Safety measures are invariably stricter on the nuclear side, where, as Mr Cathro puts it, ‘there might be the slight possibility of airborne contamination or contamination on the floors or walls’.

Each time a worker comes out of the Radiological Controlled Area all small items, from tools to helmets, will be put into a 'SAM', or small article monitor to screen for potential contamination, however miniscule the level. The monitors will identify the smallest amount of radioactivity

Safety first: There are five machines like this at Torness - full body monitors that workers must stand inside before they leave the Radiological Controlled Area. Screenings are carried out every time someone leaves the RCA (RADOS is merely the brand name)

Taking no chances: Torness is festooned with warning messages and emergency kits. The bin marked 'spill kit' includes booms and absorbent materials which would be used in the case of a spill. The kit’s contents would vary depending on where it is situated on the plant

LCO stands for Limiting Condition of Operation (operation rules) and CCR is the Central Control Room. These doors are designed to contain a potential fire, hot gas or steam release within the reactor

Cooling Water Forebay: This area of the plant brings in seawater to cool down steam from the turbines

Pressurised job: Working at the plant inevitably involves getting to grips with pipes, valves and pressure read-outs

Some of this radiation comes from naturally occurring radon in the building materials, some from filters being changed. Either way, EDF takes no chances.

Mr Cathro said: ‘Whenever you go into the radiologically controlled area, you can’t get in until you get what’s called an epd – an electronic personal dosimitor – you carry that with you and it measures any radiation dose you get. I go in regularly, and routinely there’s zero on it.’

On the way back out of the nuclear area, workers must place any tools they’ve been using into a ‘SAM’, or small articles monitor, which checks for contamination.

Safety at Torness has been further improved by engineers studying what went wrong at the Fukushima plant in Japan in 2011, when three reactors went into meltdown after a tsunami struck.

Mr Cathro said: ‘We looked at what lessons could be learned, here, and at all our power stations. We didn’t, in actual fact, need to do anything.

‘All our safety cases were secure. But the company decided to go above and beyond, and we’ve got some back-up equipment, things like diesel generators and water pumps, at various locations around the country and I’ve been involved in making sure that when that equipment comes to the site it’s easily plugged in and usable.’

Torness is certainly an impressive operation – and should anything go wrong EDF has around 8,000 staff in the company it can call upon to rectify the situation.

‘There’s a lot of intellectual capability there,’ said Mr Cathro, who, trouser contamination aside, radiates nothing but total confidence in his power station.

Education: Opened in 2013, Torness's visitor centre features interactive games and displays that explain how nuclear energy is made. Visitors can test their strength by turning the handle to generate enough elecrtcity to power a toaster, a TV or other household devices. Pictured is tour guide Belinda Smith

Class act: A school group get to grips with how nuclear energy works in the visitor centre

ILLUMINATING FACTS: HOW TORNESS CREATES ELECTRICITY 

Expert: Ian Cathro is EDF's Special Projects Manager at Torness

Torness is an Advanced Gas Reactor nuclear power station, but as Special Projects Manager, Ian Cathro, explained, it produces electricity in much the same way as a coal-fired station.

He said: ‘Burned coal produces heat, from that heat pass the hot gases, over tubes. Inside the tubes, they pump water, the water turns to steam, and then steam is used to drive a turbine. And if you can picture the turbine – it’s like a windmill on a stick - the steam blowing across the blades makes its spin. And attached to the same axis, there’s what’s called the rotor, inside the generator. If you think of an alternator in your car, it’s the same principal – inside the generator, the rotor spins through a magnetic field, and that's where the electricity is created.

‘So the whole thing is about getting the rotor spinning. We do more or less the same, except the initial source of heat isn't chemical, like burning coal in air.

‘What we do, is we take biggest naturally occurring atom, which is uranium. In particular we use uranium 235, which is a particular size of uranium atom. And uranium 235 can spontaneously, or if it absorbs a neutron, become unstable and split. And it actually splits – this is originally alchemy – into new materials. So you might get iodine, you might get krypton. But in that splitting you produce a little bit of energy, it's at the atomic level, but happening millions of times of second in the reactor and it produces a significant amount of heat.

‘Also, when uranium splits, two or three neutrons come off, and we design the reactors to persuade at least one of those neutrons to react with another uranium 235 atom and make it split, and a neutron from that goes to another uranium 235 atom and it splits. That's the so-called chain reaction and is the way we control the reactor if we want to start it up. If we want to shut it down, we put in control rods, which absorb the neutrons. They’re essentially lumps of metal. And they don’t let the neutrons go to the uranium. That shuts it down.

‘If you want to start the reactor up – you pull the control rods out gradually. And that heat is made by tiny tiny atomic splits of uranium 235, but there’s so many of them that you get significant amounts of heat.

‘The fuel we use is about the diameter of a thumb. And about a centimetre long. It’s uranium dioxide – ceramic - and has a very very high melting point. And they are contained within stainless steel clad, about a metre long, and the diameter of your thumb, and we’ve got about a 100,000 of those in the reactor.

‘That’s where all the heat comes from. Just like a coal power station, all the heat is being formed in the fuel pins. We pass gas over the fuel pins, to take the heat away, and when the gas gets hot it comes down over boiler tubes, and when the gas is coming down, the water is going up, picking up the heat from the gas, turning to steam. The steam turns the turbine and the turbine turns the rotor. And that’s how we make electricity.’