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Last month I had the pleasure of visiting Torness nuclear power station in Scotland – many thanks to EDF for hosting me and giving me a detailed tour. I got to both stand on top of one of the reactors and touch the side of it, close to the gas injection pipes. (I joked to an anti-nuclear friend that when I did so I could see all the bones in my hand…obviously I couldn’t!)
When I write my blogs I often go to Adobe Stock to buy the base images I use to make the pages look pretty (I then combine at least two in order to create an original artwork). I try to make these images relevant to the subject, but have noticed when I search for “nuclear” many of the results are scary looking men in hazmat suits, and gas masks, with an evil-looking green miasma swirling around. Clearly for use in anti-nuclear propaganda.
While I know a fair bit about how nuclear power works, reading about it is no substitute for seeing it in practice.
I arrived on site on a sunny but windy day in late February. I had been instructed to leave my phone and other electronic devices in my car, and bring photo ID to the security gate, where I was given my visitor’s pass, had my bag scanned and was subjected to an airport-style security search. I was then met by a nice lady wearing a “Responsible Escort” lanyard, which made me wonder if I would meet an “Irresponsible Escort” at some point in the day and what that might look like(!).
She took me to the office of station director, Paul Forrest, where I was met by Paul and Fiona McCall who is the Senior External Affairs Manager for the existing EDF nuclear fleet. After getting kitted up with PPE (I had my own steel toe-capped boots and safety glasses and was provided with a boiler suit, hard hat, ear defenders and work gloves although I ended up having to take the gloves off since I started getting an allergic reaction to them).
First of all we took a walk past the workshop where some of the 750 on-site staff repair parts or inspect new parts ready for installation, before heading directly to the nuclear part of the site.
Understandably, security was high, both personal and for the site. We crossed over a line which marked the point at which PPE was mandatory and went to collect our dosimeters (radiation detectors) which had to be electronically registered and associated to our security passes. Fiona then went through a full height turnstile to enter the nuclear controlled area and I was directed to enter through a heavy security door. When Paul tried to follow through the turnstile, he found he was unable to enter: his dosimeter and security pass had stopped talking to each other and he had to go away and get them re-connected. Not even the station director gets to by-pass security protocols.
Fiona took me to the charge hall where she explained what it is while we waited for Paul to re-join us. This is the tallest room on the site, named after the machine which loads and unloads fuel into the reactors – charging them up. At each end of the room, at floor level, is the top of the containment for each of the two Torness reactors.
The charge machine, painted a fetching shade of pale green, trundles up and down between the two reactors to carry out its functions (during my visit both reactors were in use, but the charge machine was on a maintenance outage). The machine (and room housing it) is tall enough to accommodate the 10m long fuel rods known as “stringers” – the crane is positioned above the reactor, extracts an old fuel rod, turns round, and inserts a new one, in a seamless motion. Obviously, this takes place during re-fuelling outages and not while the reactors are running!
Reactor 2 is about to go off-line for a re-fuelling outage, and then reactor 1 will go off for a statutory outage, a period of around 65 days when some 13,000 – 15,000 tasks that are completed in order to ensure that the plant remains compliant with all relevant regulations and maintains a safe operating environment. Each statutory outage involves a £20-25 million investment in the plant.
While the tasteful green colour of the charge machine has no particular significance, other colours used on site have more meaning, and not just the company logo! Plant painted pink represents a single point of vulnerability making them easy to identify. Also, in order to avoid removing the wrong kidney /amputating the wrong leg type of mishaps, all the paperwork for reactor 1 is on yellow paper and that for reactor 2 is on blue, so it is immediately obvious to which reactor any given piece documentation relates.
By now, Paul had re-joined us, and we went to stand on one of the reactors, 32 meters above ground (the bottom of the containment is 12m below ground level). Of course, we were not standing directly on the reactor – we’re not idiots – but on top of the containment, in this case, 18 inch thick steel blocks known as the “pile cap” which were designed at the time of initial construction (ie long before 9/11) to withstand an aircraft impact.
Paul explained that the biggest risk is not from a passenger jet, since although they are very large, they travel relatively slowly by aeroplane standards, but from Tornado fighter jets whose heavy, dense engine block could theoretically impact the reactor containment at very high speed. (There are some great pictures in this article, which I won’t reproduce for copyright reasons but are worth looking at, including of the pile cap.)
Reassuringly, there was no green miasma and none of us began to glow as you can see from the photo!
It was also quiet – the only noise was from fans required to cool the building, not from the reactor, but from the sun – the building has little insulation and large windows, meaning that even on cold sunny days, it can become quite warm inside. There were also no vibrations from the reactor. It’s cool, quiet and drama-free.
We then descended several floors to reach the reactor floor, where I got to touch the side of the reactor, next to one of the gas circulators. Also on Friday, the Guardian newspaper published some pictures of nuclear installations under the headline ‘A picture of hell’: inside the UK’s nuclear reactors – in pictures but going on to say the photographer found them “tranquil, beautiful and sinister”, one of which was taken at Torness, at the same spot on which I was standing.
At a basic level, nuclear reactions give off heat which is used to produce steam which turns the turbines which turn the generator which generates electricity. The way that the heat from the reaction is accessed is by passing gas through the reactor – it enters at 250oC (for a cold start this temperature is achieved through pressurising the gas, but otherwise it is warm from its previous passage through the reactor) and reaches 660oC by the time it exits. The big orange circle (in the Guardian picture) is the panel through which the gas (CO2) enters the reactor. You can also see the different phases of the three-phase supply used to power the reactor. A heat exchanger is used to heat water to produce steam.
Leaving the nuclear controlled area was even more involved than entering. This time we had to enter something similar to the full body scanners at airports to make sure we had not received any radiation contamination. The machine had a woman’s voice which initially kept telling me to “get closer” which was tricky since I was already pressed against the edge of the scanner. I had to place my hands and fore-arms inside special slots as well.
The voice then counted down from six (apparently the number is random either four, five, six or sometimes seven. It then comfortingly told me that the radiation detected was zero. In fact there were two such machines, and each time I had to stand facing into and then out of the scanner, and each time the result was the same: zero contamination. Luckily we had not been outside, since the cosmic rays to which we are exposed on a daily basis would result in a non-zero reading!
As we walked to the turbine hall, we discussed ramping and load following for nuclear. While the Torness reactor can be shut down in 4 seconds, it takes 12 hours from start-up to grid synchronisation, making it too slow for practical load following.
The reason for this length of time is the time needed to bring the plant up to temperature for steam production. Paul told me that while Torness could not sit at half-load for extended periods, newer reactors can, and of course, in France, reactors operate flexibly since as close to 80% of the electricity mix they need to be able to vary output in line with demand (load following).
So we then came to the turbine hall. Each reactor has its own dedicated turbine set, each in three parts operating with declining temperature and pressure until you reach the generator itself. The gas which circulates in each reactor heats water to create high temperature, high pressure steam which turns the high pressure turbine.
The steam is then re-cycled before passing through the intermediate pressure turbine, and is again re-cycled before passing into the low pressure turbine which then turns the generator to generate electricity. The casing of each of these turbines gets progressively less warm, as expected (yes, I touched all of them!)
Unlike the charge hall, the turbine hall was LOUD! Very LOUD! But this is conventional plant – turbines are not quiet, and you would not find the turbine halls of gas or coal power stations being any quieter (unless they were turned off!).
After lunch I visited the exhibition centre. The picture below is of a model of the plant, which shows all the different sections of the site and gives a sense of the scale of the operation (the little model people give an idea of how large the plant is).
I had an interesting discussion with the lady there about the control rods, as this was something I had forgotten to ask while I was inside the plant. The control rods are held by magnetic clasps which release instantaneously when needed to drop inside the reactor ending nuclear reactions in 4 seconds once inserted. Both the fuel rods and control rods pass through the core structure which is comprised of graphite bricks.
These bricks are the subject of much regulatory concern since the Office for Nuclear Regulation believes that they may become dislodged during an earthquake inhibiting the passage of control rods into the core. While this may be the case, it currently requires that 100% of the control rods be capable of entering the core in a 1-in-10,000 year earthquake – 10x larger than the largest ever recorded in the UK, despite the fact that only 15% are actually required to terminate the reaction and there are two other shut-down methods that could be engaged in the highly unlikely event that the control rods did not work. I discussed this in more detail in my report on nuclear power published last November.
In the exhibition centre I also learned that the fuel structures are profiled in order to allow the gases to move through the core more efficiently – everything is engineered down to the last detail. This schematic shows everything in greater detail – I suggest downloading it (click on the image) so it can be better magnified to see all of the detail.
People have all kinds of assumptions about nuclear power, most of which I think are mis-placed. The reality is that our nuclear power stations are extremely safe, and entirely drama free. The entire vibe is calm, and the plant was impressively clean for an industrial site.
It was clear that working to a high standard was embedded in the culture – in some organisations, safety rules are met will eye-rolling and a tick-box mentality, but at Torness it was clear that not only was basic industrial as well as nuclear safety taken very seriously, it is part of the operational DNA. There is a clear “take the time to do it right” mentality and a calm efficiency about the operations.
I had a really interesting and enjoyable day at Torness and would like to thank Paul and Fiona for showing me round what is a very impressive site.
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