What's inside a nuclear reactor?

IN the second part of our look at Sizewell A power station, PAUL GEATER gets a glimpse inside the reactor, to see how it is still making a contribution to the nation's electricity supply 40 years after it first entered service.

By Paul Geater

IN the second part of our look at Sizewell A power station, PAUL GEATER gets a glimpse inside the reactor, to see how it is still making a contribution to the nation's electricity supply 40 years after it first entered service.

STANDING on the top of the reactor pile cap, it is difficult to comprehend what is happening just a few metres under your feet.

There's no vibration. There's no hum. There's no need to wear white radiation suits.


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The only thing to indicate that there's something different about this area is a few radiation signs on the wall and warnings about taking care on your way out.

We were warned not to go on top of the other reactor because they were having a few problems with refuelling and the engineers wouldn't want us in the way - but generally the most astonishing thing about standing on top of the reactor is the normality of it.

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It's the getting into and out of the reactor building that is more of a challenge!

We had asked to go to Sizewell several weeks ago to look at the power station in the run-up to its coming off-line. By the time the visit was arranged, everything was put in place to get through the various security screens - but it was not an easy process.

To get on to the Sizewell A site, photographer Ashley Pickering and myself had to report to the security gate and wait there to be collected.

We were each given two security badges which we had to wear at all times. At one stage during our visit there was a fire drill - not for our benefit we were assured - which meant we had to present our badges to an electronic reader so our location could be established.

To get into the reactor building was tougher still.

We had to sign more forms and pass through a Geiger counter measuring the radiation we were taking into the building.

Once inside there were comparatively few restrictions - although we were accompanied by two senior members of staff wearing radiation monitors - but coming out again there was a more thorough check for radiation.

Ashley had to have his cameras checked manually because there was a risk that low levels of radiation in the materials used to coat modern camera lenses could set off alarms.

On the pile cap there are hundreds of tubes which go down into the heart of the reactor. It is into these tubes that fuel rods - uranium encased in magnesium oxide - are dropped to fuel the process, provide heat and ultimately to create electricity.

The speed and heat of the nuclear reaction - and ultimately the safety of the whole operation - is regulated by graphite control rods. In an emergency they can be dropped fully into the reactor which will make it unusable, but will stop the nuclear reaction in an instant.

The reaction heats gas which leaves the reactor and goes into one of the heat exchangers in the boiler.

This hot gas heats water into steam which drives the turbines to create electricity.

After turning the turbine, the steam is cooled by passing in pipes through cold water drawn from the North Sea. It then returns to the heat exchanger for the process to carry on.

Most people who visit the coast know that the power station uses seawater - but many are under the mistaken impression that it is used to power the turbines rather than just for cooling.

Before it can be used it has to be filtered to prevent fish, seaweed, or stones and gravel from getting into the system.

This is done by passing it over huge drums - and every so often these have to be stopped and cleared which can disrupt electricity generation at the station.

There are two pipes leading to and from the sea, finishing at outfalls that look like mini oil rigs just off the coast.

Water is sucked in from the far one and blown out from the nearer outfall. The seawater is warmer here and it has been a favourite place for bathing. It is certainly a good place for fish and seabirds - the nearer outfall is one of the best birdwatching sites on the coast as seabirds flock to catch the fish attracted by warmer water.

N

In the Star tomorrow: How do you switch off and dismantle a nuclear power station?

Operations manager Tom Pattinson, who has been at Sizewell A for 30 years, after a career as a television engineer.

After training at Cliff Quay in Ipswich, he arrived at Sizewell in the late 1970s and worked his way up the career ladder.

There are many links with the former Ipswich power station at Sizewell - many staff transferred up the A12 when Cliff Quay closed in the early 1970s. And there are few regrets among those who made the move. Andy Baker from Otley is a team leader overseeing the turbine operations, and has no regrets about moving up the coast.

He said: “It's a lot cleaner than it was at Cliff Quay, a much better place to work. It's said to be a lot safer - but in fairness safety was never much of problem on a day-to-day basis at Ipswich either. The CEGB was always pretty keen on that.”

People travel to work at Sizewell from a wide area - although about 48 per cent of staff do live in the nearby towns of Leiston and Aldeburgh.

“I live near Oulton Broad and there are many people who come in from Ipswich or even beyond every day,” said Mr Pattinson.

Sizewell A attracted workers from a large area - some were local and attracted by regular work in a modern plant, others moved from other parts of the country to find work.

Among these were Dick Billanie who may have been working at Sizewell since 1970 but the minute he starts speaking there's no mistaking his Geordie roots.

He explains: “I came down for a couple of years in 1970 and I'm still here! I live in Leiston. It's regular work and a good job. I don't regret things at all.”

Mr Billanie worked in a mine before moving to Suffolk, and his family remained in the north east working in the coalfields.

“This is very different to that. At one stage the miners came down here when they were on strike and some of us put them up, but this is a very different industry to that,” he said.

SAFETY is the key watchword at Sizewell A - whether on a large or a small scale.

Monitoring for radioactive contamination is constant - workers on the site wear small detectors whenever they are in the reactor building so the level of radioactivity they are exposed to can be recorded.

The level of exposure to a full-time power station worker is roughly the same as that of a hospital worker - and considerably less than that of airline flight crew.

Radiation detection equipment is used constantly to monitor levels and ensure they are not exposed to any danger - but in fact it is more likely to pick up increased radiation from outside sources than from the site itself.

Jim Benton recalled the Chernobyl incident of 20 years ago: “We detected something had happened here before there was any announcement from Russia.

“Our instruments were showing something had happened but we knew it wasn't from Sizewell. It was a totally different kind of radioactivity. You can spot where it has come from.”

His colleague Mick Butler recalled that one worker lost the clothes off his back - literally - after the Chernobyl disaster.

“His mother had washed his sweater and left it out on the line to dry. The wind was coming from the east and radioactive particles settled on the sweater.

“He managed to get into the reactor building to do his work, but on the way out the detectors went completely haywire.

“It took some time to realise it was the sweater that was setting them off and he had to take it off there and then.

“I don't think he ever got it back - it was treated as low-level radioactive waste!”

SIZEWELL A's control room has changed little since it started generating electricity in the 1960s. It is staffed 365 days a year 24 hours a day keeping power running into the national grid.

Kevin Oxford is a relatively new boy at Sizewell A - he arrived in 2002 and moved to Rendlesham.

He was monitoring one of the reactors in the control room under the watchful gaze of shift manager Dick Smith - another refugee from Cliff Quay.

Mr Oxford said: “At the moment everything we do is about generating electricity safely. That will all change at the end of the year with the end of generation.

“The job will change - but we will still have a job to do defuelling the power station and preparing for decommission.

“That will last three years and then, who knows? Maybe we'll be looking at Sizewell C by then!”

There are two reactors, producing a total of 440 megawatts of electricity - enough to power a third of East Anglia. The reactors use 26,500 fuel rods each.

Each fuel rod contains enough fuel to last an average 10 years - depending on where it is placed in the reactor. The used fuel rods are taken by train to Sellafield in Cumbria for reprocessing.

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