Not too long ago, I spent some time with EDF Energy as part of my work experience week. As I am hoping to study STEM at university level, I hoped that this placement could help me better understand how the different disciplines within engineering are applied within power generation, and decide which aspect I would be best suited to and enjoy the most!
EDF Energy produce around 1/5 of the UK’s electricity through a mixture of energy sources, including coal, wind and gas power stations. I carried out my placement in the part of the business that focuses on the UK’s nuclear fleet of power stations. Aside from my limited knowledge about nuclear fission from GCSE Physics (!), I had very little idea as to how a nuclear power station operates. I now know more than I could ever have expected to, within the course of only four days!
I was also very aware of the scepticism surrounding the use of nuclear fuel because of concern over radioactive waste disposal and safe operation, which I expect was further heightened after large-scale nuclear disasters such as Fukushima. My stance on nuclear power at the start of the week was very neutral. However, I was interested to find out what is done to alleviate the risks that nuclear power generation poses and find out just how it compares to other forms of power generation. As I said earlier, I was keen to get an overview of the various elements of engineering involved as I wanted to keep my options open and find out what I find most compelling. My work experience host was kind enough to organise my week so that I was able to speak to people working across a number of departments, which I found both useful and informative.
On my first day, I found out more about the National Grid as it stands, and discovered that gas stations account for over 50% of the UK’s output. The majority of these are combined cycle generators, in which heat generated from turning turbines is reused to turn another turbine which increases overall efficiency. I also found out that coal power stations are being phased out because of the level of emissions they release.
I was then able to listen in to a conference call. Admittedly, there was a lot that I did not understand, but I did pick up some acronyms! One of the things discussed by the team was SPVs – single-point vulnerabilities – which are systems that do not have redundant components, and can therefore have a direct effect on output if something went wrong. These can (and should) be mitigated by using redundant parts and diversity within the system.
Following a tour of the site, I learnt more about how nuclear reactors actually work! Advanced Gas-cooled Reactors use graphite as a moderator and carbon dioxide as a coolant. They were developed from the Magnox reactors which was originally optimised for generating plutonium. We got to see the fuel assembly and pellets that are fed into the the reactor. The fuel used is generally Uranium (enriched to make the fission process easier), which is converted into pellets and fuel assemblies and coated with a non-corrosive material. The other type of reactor is the Pressurised Water Reactor, which uses water as both a coolant and as a moderator.
I found out more about the significance of graphite which forms the core within AGRs, and acts as a moderator to slow down neutrons and so allows for a sustainable chain reaction. Over time however, oxidation causes the graphite to lose weight which causes it to crack due to the build-up of stress and reduces its effectiveness, thus limiting the life of the reactor. It was amazing seeing the variety of work that goes on and I particularly enjoyed hearing about the specific projects each person I spoke to was working on!
(I’ve just realised how much I’ve written already so am going to attempt to summarise a bit more from now on…!)
The following day, I discovered how vibrations from rotating plant within a power station (eg. pressurisers, condensers etc.) can be used to infer their condition, alongside other signals. I found it fascinating that frequency spectra could be correlated to specific faults, and allow problems to be identified early on (preventative maintenance).
It was also interesting finding out more about how projects are chosen: by evaluating risks at power stations to determine their urgency. This includes consideration of the costs of the new system compared to the loss the risk could potentially cause. Again, it was great being able to see the contribution of each individual to a team, which then contributes to the company as a whole.
I spent my morning in the Materials Lab, where we looked at the different parts that are sent in for analysis, which ranged from bearings to turbine blades. I think this made me realise the huge breadth of work that is involved in maintaining a fleet of power stations, from design, development, testing and installation to maintenance and follow-up analysis! As someone who hasn’t done much practical design work, I feel as if I now recognise and am more appreciative of the time (and the level of care!) involved in working with materials. I also got to see an electron microscope in person for the first time! We were demonstrated how it can be used to analyse samples and discovered just how superior it is to light microscopes to the extent that substances can be analysed to identify changes in the chemical structure of the material.
I then found out more about the reactor protection side of things, and how a safety case must be made when any changes are made to a system. This is to justify why they are being made, as well as an explanation about why those changes will not cause any harm. One of the most noticeable things I picked up about EDF Energy as a company during my time there is just how much they value safety. The question I had in mind about the level of precaution that is enforced was definitely answered! I found out that EDF Energy are regulated both internally and externally, and employ a multitude of techniques, such as ensuring diversity within their systems and ensuring high standards are maintained. This all is key in helping keep us safe.
And they also have protocol in place in the event that something still manages to go wrong. I found out about the process that takes place following a radiation breach, which involves a team of people with specific roles. This includes plotters to map out the radiation levels across the country, health physicists to analyse the effects of this and take appropriate measures, engineers to find a solution and many more. I found out that EDF Energy regularly practice this in through mock situations, so that they are adequately prepared if anything ever does happen (which it hopefully won’t!)
On my final day, I learnt more about the chemistry side to nuclear engineering, and how it’s fundamentally important to nuclear power stations. I learnt many interesting facts about solutions to problems that I had not ever considered. For example, I found out that water is dosed with chlorine in order to prevent the growth of oysters and barnacles within the pipes!
Finally, I had the opportunity to have a go at using some of the equipment that is used to access radioactive environments which human beings cannot, such as the reactor itself. We learnt how the smallest cameras can be used to fit through tiny gaps, and even had a go at controlling a robot to see what it would retrieving debris from a reactor might be like – much harder than it sounds, as I discovered!
My week at EDF Energy was incredibly insightful and has certainly opened my eyes to the huge breadth and depth within engineering, as well as routes into STEM. I am grateful to everyone at EDF Energy who made my placement so enjoyable.