I Visited A Nuclear Power Plant - And Still Have Only Two Eyes!

Not Geography Geography Lesson 9

Weird and Wonderful Nuclear Power

A post actually on time - what has come over me... On Friday this week, I visited Heysham Nuclear power station in Lancashire, as part of one of my 3rd year modules. Specifically we visited Heysham 2, which is the second, larger and newer nuclear facility at the site, and my mind was genuinely blown by it. The scale and complexity of the whole thing was incredible, and I was in awe of the fact that people actually designed and built this thing - the millions of tiny buttons and bolts, and the back-up systems for back-up systems, and all the procedures, and that when they had designed everything they then had to start doing it without actually knowing for sure what was going to happen... I'm not a nuclear scientist, but I don't think trial and error is the approach you want to be taking to building a nuclear reactor. 

Unlike the normal style - where I just write generally about a topic - I'm going to describe what I saw and what we were told by the guides, and cut to all the interesting bits! And then you won't have to pay for a tour because you already know all the deets. 

We're Gonna Need A Bigger Crane... 

Construction of Heysham 2 began in 1980, 10 years after Heysham 1, and was completed in 1988. They chose Heysham for the site for a couple of reasons:

• It is in a relatively industrial area already.
• The parts that make up the site are so enormous that they could not be transported by road (lorries just aren't big enough) so arrived on ships to the port next door.
• One of the critical phases of the energy making process requires cooling and condensing very hot steam, and they use a lot of sea water to do this (and I mean A LOT - 30'000 litres per second!).

Construction actually worked around the reactor itself (the scary bit), so they put that in first and then built the rest around it. All will become clear why later on. 

There are also some clever bits of planning regarding where things are, with the focus always being safety (reassuring..?). There are four back up power supplies on site, in case the reactors stop producing power to control themselves, and these are located on the four corners of the site, so that one event (like a bomb or a fire) could not take them all out at once and prevent power reaching the controls of the reactors. Also the power cables which supply the control room are spread out as far as possible from one another for the same reason. There is also a train track running around the perimeter which is used for moving the waste fuel up the coast to Sellafield once a week, and only one pylon is needed to transfer all the power to the national grid. 

How It Works (From Someone Who Is Most Definitely Not A Nuclear Scientist)

The nice people at Heysham get their fuel in the form of little pellets of Uranium-235, from a company called Springfield (*insert Simpsons joke here*). The little pellets are placed inside metal tubes, of which about 20 are all held together inside a graphite shell; it looks kind of like honeycomb. When the tubes enter the reactor, there are lots of free neutrons knocking around in there, and when the neutrons hit the uranium atoms, they split them into more atoms, and release more neutrons. All this colliding and splitting and whizzing around generates an unbelievably enormous amount of heat, which is used as the driving force to turn turbines and generate electricity (just as regular coal or gas power stations do). Heysham uses ionized water to transfer the heat to the turbines, in the form of steam, by passing it through lots of pipes near the uranium where it evaporates into steam and then is forced over the turbines. They then use the cold seawater to condense it, and send it round again and again. 

How Do They Get The Fuel In (And Out)?

The reason the plant was built around the reactor is because a huge 90m tall machine is used to pull the old fuel rods out and put the new rods in. Like an arcade grabber and a Transformer had a baby. Across the lid of the reactor (which is many metres thick) is a grid of squares with numbers and letters, and under each one is a column of the fuel rods - 6 of those honeycomb shaped shells stacked on top of one another. Two tracks run down the entire length of each side of the room, so that the huge machine can run down the tracks and on top of the reactor, where it is programmed to know which grid square it needs to work on. It pulls out the old column of fuel, and stores it inside an empty barrel, and then rotates itself to position the new fuel column over the hole and fill it. Like a revolver with its movable chambers. 

The old fuel comes out still generating 400 Mega Watt Hours (MWh) of energy (hotter than the real life depths of Hell), and so is placed in a cooling storage area, and then a cooling tank for about 6 weeks until it is safe to put on the little train up to Sellafield. 

The rods need changing every 7 years, but because they are all at different times along that 7 years, at least one is changed every week, and the process takes 12 hours to complete. 

I've Seen 'Chernobyl Diaries' - Nuclear Power Is V. Dangerous!

I must admit, I had my reservations about entering what I had imagined as a huge human popcorn maker, but actually it is all very safe and is managed more carefully than Donald Trump's hair. Heysham 2 uses 250 cubic tons of carbon dioxide (CO2) a day to cool its reactor, and also has a series of 'control rods' which are made of neutron-absorbing graphite than can be plunged into the reactor in only a few seconds to completely stop all reactions going on in there. If the rods don't work for any reason, they can also released millions of graphite pellets into the reactor, or flood it with nitrogen which also absorbs the neutrons. Back-ups on back-ups on back-ups. The reactor itself is also encased in 6 meters of concrete.

Clever Stuff Indeed

Heysham 2 runs 24/7, 365 days a year. The design of the reactor is such that it does not need to turn off to refuel or to do maintenance, and just runs at lower outputs during those times. So, the amount of power it generates is pretty much constant and comes out at 1230 Mega Watts or enough to power 5% of UK homes. 

Miscellaneous Fun(?) Facts 

• The uranium that Springfield supplies is completely harmless before it enters the reactor because no neutrons are hitting it - all the workers even have one of the little pellets on their ID lanyards. 
• The control room looks like something from Star Trek Enterprise, but the first version! It is set below an observation deck, has no windows, and still uses the 1980's computers and technology that it first installed. There are only three desks - one for each reactor and one for the big manager - around which are 100's of buttons and screens with what looks like Teletext on them. They use this old school technology because it is harder to hack!
• There are nearly 600 staff who work at Heysham 2, but the vast majority are human resources and office workers - in fact the entire site could be run perfectly fine with only 40-50 people. 
• Before 9/11, people could very easily visit the site by just signing a register. Now you have to book weeks in advance, fill out many forms for security checks, bring your passport or drivers license, and go through three different checkpoints with scanners. 
• Contrary to common belief that nuclear power releases no greenhouse gases, Heysham 2 actually has a permit to release 1 cubic ton of CO2 per day, from the 250 tons they use to cool the reactor.
• Heysham 2 is currently set to close in 2030, but when I asked that will entail, they didn't really know because it has never happened before. Weird.

This has been quite a bit longer than regular posts, but I thought it was such an interesting subject and enjoyed my visit so much, it would be a waste to not write about it properly! Regardless of your moral stance on nuclear power, you can't deny the level of ingenuity and skill that goes into creating something so huge and powerful is very impressive. Thanks for reading, and I hope you have an electrifying week! I'll see myself out...