See inside a nuclear reactor - we take behind the scenes trip to Sizewell B

Buildings associated with Sizewell B will be moved to a woodland Picture: SARAH LUCY BROWN

Many people recognise Sizewell B's famous white dome - but what is inside? - Credit: Archant

Few people ever get to go inside Sizewell B's nuclear reactor - but today, we can give you rare, privileged access to a scientific marvel right here in Suffolk usually hidden from sight.

You will probably be very familiar with the power station's famous white dome, which can be seen from miles away along the Suffolk coastline.

But hardly anyone has seen what is inside the dome - until now.

There are many very good reasons why the inside of the 65metre high, 45metre diameter building is strictly out of bounds to all but the most highly-trained nuclear engineers.

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

Another view of the dome at Sizewell B - this time from the inside - Credit: CHARLOTTE BOND

The dome houses the beating heart of the 26-year-old plant - the pressurised water reactor (PWR), which splits uranium atoms in a process called fission to create nuclear energy.

The energy it creates is intense - enough to power two massive turbines with shafts rotating at 3,000rpm, which turn it into electricity for 2.5million homes.

The temperature the reactor inside is 260C and it is highly radioactive, meaning the shell of the dome is built to withstand the impact of a potential meltdown - however unlikely managers say such a catastrophe is.

Clearly, when the station is fully operational and pumping out 1,200MW of electricity, people will only enter the containment area - where the reactor is based - very infrequently to make the most necessary checks.

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At that time, the very few people who go inside must do so through an airlock with a double hatch to ensure no radioactive elements escape.

But the EDF Energy-run station is currently shut down for a total of six weeks for maintenance work to take place - the most crucial of which is the refuelling of the nuclear reactor, to ensure it can continue operating for another 18 months.

That process takes about a month and requires a high level of skill and expertise which takes years to learn, meaning that around 200 people can be in the containment area at any one time.

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

Inside the containment area at Sizewell B nuclear power station - Credit: Charlotte Bond

This newspaper was given an exclusive tour around the containment area, as workers also take the opportunity to check crucial parts and either replace or maintain components.

For scientists fascinated by nuclear technology, seeing a reactor up close is a dream - perhaps like seeing your favourite football team live.

Even though he has been into the containment area many times, Sizewell B station director Robert Gunn said: "I genuinely still feel excited when I go around the plant and see the technology - even after working for the company for 30 years.

Robert Gunn station director at Sizewell B Picture: CHARLOTTE BOND

Seeing the nuclear technology at Sizewell B still excites station director Robert Gunn - Credit: Charlotte Bond

"Just the fact that one reactor is producing so much power for the country is quite amazing. 

"It is great to see that one bit of the plant producing that amount of power for the country."

Yet the protection required to go inside a highly radioactive area, even during an outage, is a whole different level to wearing protective masks and washing your hands during the Covid pandemic.

The station does, of course, also take full Covid precautions - no-one is allowed onto the site without a negative Covid test, with workers also being tested at least once a week.

Face masks must also be worn at all times when moving around the station.

But as well as undergoing thorough security checks, those who go inside the containment area must wear hard hats, goggles, a full yellow coverall, overshoes and two sets of gloves - all on top of a face covering to protect against Covid.

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

Only a handful of people ever get to see inside the Sizewell B dome - Credit: Charlotte Bond

You also carry a pocket radiation monitor at all times and twice stand in a machine to check for signs of radiation on the way out.

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

No-one leaves Sizewell B's containment area without being checked for signs of radiation in one of these machines - Credit: Charlotte Bond

Even taking off your coveralls is a bit of an art form, as you have to remove your gloves from the inside and avoid your hands touching anything that might have been contaminated.

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

The containment area at Sizewell B boasts some of the most advanced nuclear technology - Credit: Charlotte Bond

Once you get inside though, it is hard not be impressed at the level of technology - whatever your views on the rights on wrongs of nuclear power.

Perhaps the most striking sight inside the dome is the water surrounding the nuclear reactor - which glows a stunning bright blue, like something out of a science-fiction movie.

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

This glowing blue water is one of the most impressive sights inside Sizewell B's nuclear reactor - Credit: Charlotte Bond

That is because, during refuelling, radiation particles are travelling faster than light through the water.

That causes a shockwave which produces a sparkling glow - or Cherenkov radiation, to give it its technical name.

Yet nuclear scientists are just as fascinated by the intricate workings of the equipment inside the reactor - such as a multi-stud tensioner, which lifts the top and bottom covers off the steam generator to allow for inspection and maintenance. 

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

The multi-stud tensioners lift the covers off the steam generator inside the reactor - Credit: Charlotte Bond

There are also four reactor coolant pumps, which may just look like a shiny tube to you and me but play a critical role - as they transfer the heat from the reactor core to steam generators.

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

Crucial equipment is housed in Sizewell B's containment area - Credit: Charlotte Bond

The steam produced in those is what drives the two massive turbines, which are also undergoing maintenance and inspection during the outage.

The Turbines at Sizewell B Picture: CHARLOTTE BOND

One of the large turbines at Sizewell B, which turn steam produced by the nuclear reactor into electricity - Credit: Charlotte Bond

Megan Hopkins, 25, is a radiation protection engineer working on the Sizewell C project to build a brand new nuclear power station next door.

But she has been getting experience at Sizewell B after graduating from Lancaster University and completing an industrial placement at Heysham nuclear power station, in Lancashire.

She recalled how she was amazed to see the intricate level of detail of the engineering in the turbine hall.

Of seeing the nuclear reactor from a viewing platform, she said: "It was crazy to think that was something I could do.

Megan. Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

Megan Hopkins, 25, is a radiation protection engineer working on the Sizewell C project - Credit: Charlotte Bond

"For me to get an idea of what containment is like and being in there, nothing beats that.

"You can feel like you're in an exclusive club, with access to all areas. You get to have a real look around."

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

The containment area at Sizewell B contains a pressurised water reactor (PWR) - Credit: Charlotte Bond

She added that it has also given her huge amounts of experience to take into other roles.

Sizewell B was shut down completely for a total of six weeks on April 16, with more than 1,000 workers currently on site at any one time.

The Turbines at Sizewell B Picture: CHARLOTTE BOND

Sizewell B's turbine hall during the 2021 outage - Credit: Charlotte Bond

Even though Sizewell B has reduced the number of contractors on site to ensure it is Covid secure, the outage still offers a huge financial boost to nearby firms.

That is on top of the £40million the station, which is looking to expand its lifespan by 20 years, already contributes to the area's economy.

Tom Reid, strategic outage manager at Sizewell B, said workers would be carrying out the refuelling over the majority of the shutdown.

However, he said: "There are lots of other things we do when we have got the opportunity.

Sizewell B Nuclear reactor Picture: CHARLOTTE BOND

Tom Reid is strategic outage manager at Sizewell B - Credit: Charlotte Bond

"There are numerous inspections of the plant. We also look at the condition of important components and do maintenance - it is a bit like servicing your car and changing the oil.

"After we've finished with all the maintenance work, we check everything is working as it is supposed to be."

Office for Nuclear Regulation inspectors also observe the outage to make sure the correct standards are being followed.

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