S1E5 – Nuclear Power Plants Essentials – Different Types of Reactors Transcript

This is a transcript of the video S1E5 – Nuclear Power Plants Essentials – Different Types of Reactors

G’day and welcome back to the Engineering All Sorts Video Courses – professional development for teachers, helping you to Engineer your Expertise. My name is Daniel, and I’m your navigator of all things Engineering. I’m also the founder of Engineering All Sorts, where we’re all about Engineering for Educators – stem education to help you to be confident in the details – over at engineeringallsorts.com.au.

In this video we’ll be continuing our discovery of nuclear power plants and looking at the different types of reactors that are out there. We’ll also look at the pros and cons of each one so we can make the best engineering selection.

At the end of this video you’ll be able to:

Compare the different types of nuclear reactors
Identify the different components of each type of nuclear reactor in form and function
Describe the flow and conversion of energy through each type of nuclear reactor
Cite and quantify the key operating parameters of each type of nuclear reactor, such as operating temperature and pressure
Contrast key considerations in the creation and operation of each type of nuclear reactor, such as safety, cost, ease of construction and maintenance

For the full list of learning outcomes, transcripts and worksheets for this series, check out the downloads section of the series at engineeringallsorts.com.au

Compared to the last few videos, this video is pretty easy going, so let’s not dawdle – let’s take it apart!

So here we have the bare bones of 4 nuclear reactors. You may recognise some of the components from the previous videos, but some of the components will be new. Let’s start with the top one.

The first one is the one we are used to, the Pressurised Water Reactor or PWR. This type is the most common around the world with just under 300 installed. You will remember that there is a reactor on the left, which heats the water in circuit 1 to 300deg C and 150 atmospheres pressure, which then creates steam in circuit 2 in the steam generator. It also has a pump and a pressuriser on circuit 1.

The PWR uses slightly enriched uranium as fuel, with U-235 at 3.5% of the total, so there is a bit of fuel processing needed before use. This reactor also keeps the steam collecting radiation, so the turbine doesn’t need to be shielded, lowering operating costs. It uses normal water for coolant. Overall, it’s a bit more complicated, so it’s more expensive to set up.

The second reactor is a bit different. It’s called the Boiling Water Reactor or BWR. There are about 80 of these installed around the world. The BRW doesn’t have a first circuit and second circuit of water, it simply sends the steam generated in the reactor straight to the turbine. This simpler design reduces construction costs, but increases the maintenance difficulty as radioactive particles get into the turbine. The turbine needs to be shielded, and the staff protected during maintenance. The water is a bit cooler and lower pressure than in a PWR, at 285deg C, or 550 Fahrenheit, and only 75 atmospheres.

The next one is called a Pressurised Heavy Water Reactor or PHWR. There are about 50 installed around the world. The main difference here is that the moderator, which you will remember slows the neutrons down enough for a reaction, is tweaked to allow natural uranium to be used. The natural uranium, which only has 0.7% Uranium 235, doesn’t need to be enriched first, lowing processing costs.

The moderator is not normal water in this case, but something called ‘heavy water’. If we look back at the first two reactors, they use normal water, or ‘light’ water. This is a single oxygen atom with two hydrogen atoms. The hydrogen atoms have a proton each and are bonded to the Oxygen atom, which has 8 neutrons and 8 protons.

Heavy water on the other hand uses slightly tweaked hydrogen isotopes, which have an extra neutron each. This heavy water absorbs fewer neutrons, so a lower concentration of u-235 is needed to keep the reaction going.

In terms of construction, The PHWR has a steam generator like a PWR, but you will notice the reactor vessel is different. It’s not a big tank anymore, it’s a series of tubes. Each tube has a fuel rod inside, and the moderator flows from one end of the tubes to the other, gathering heat from the fuel rods as they pass through. This reactor vessel is not as durable as the tank version, but is less costly to build. It also allows the operators to shut down a portion of the reactor to replace fuel rods, whilst the rest of the reactor keeps going!

Lastly we have a very different style reactor called a Gas Cooled Reactor. There are only 15 of these installed around the world. In the centre you have the fuel rods, surrounded by the reactor vessel. The vessel is not filled with liquid water but carbon dioxide gas instead! The fans at the bottom keep the carbon dioxide flowing over the fuel rods to grab the heat, and then it passes over the water coils to create steam. The CO2 can reach up to 650degC, or 1100 Fahrenheit!

Let’s finish up with an activity. Grab a pen and paper or open up a text editor on your computer or phone, or download and print the worksheet for this episode from the download section at engineeringallsorts.com.au.

I’m going to present another scenario, and at the end I’ll ask you to make a choice and justify it based on what we have learnt so far. Ready? Here we go.

Your last shiny nuclear power plant went excellently, powering homes and industry across the land. It went so well that the local energy board want more, and all eyes will be on you this time!

It’s up to you to choose the best design to suit your second power plant. The energy board want to make sure you choose a technologically advanced design as a showpiece for their network, but also one that keeps the costs down.

What is your choice, and how do you justify the: Safety, Construction Cost, Operating Cost, Maintenance, and Technology of your decision?

Just pause the video to give yourself enough time, and then come back to us when you are done.

So how did you go? Did your proposal for your second nuclear power plant fly with the Energy Board? Reckon they’ll come around once they sleep on it? There is no right answer for this question, all answers are valid if justified well. Share your answers in the comments section below, and so we can share all the methods that we have come up with to justify our decisions.

In this video we’ve covered the four main types of nuclear reactors. We covered: the PWR, the most common reactor with the separated water and steam circuits for ease of maintenance. We looked at the BWR, which aims for simplicity in construction, but has trouble keeping radiation out of the turbine. We saw the PHWR, which uses heavy water to lower uranium processing costs, instead of normal water. And we looked at the rarer Gas Cooled Reactor, which uses air instead of water as a moderator.

Don’t forget you can check out the resources for this series and more professional development for teachers at engineeringallsorts.com.au, including learning outcomes, transcripts and worksheets.

If you haven’t left your comments below from the activity it would be great if you could also share that below, so we can all share our stem education.

Thanks for watching and I hope you’re looking forward to the next video, where we look the next major components of the nuclear power plant, the Turbine and Generator! I’ll see you there!

This is a transcript of the video S1E5 – Nuclear Power Plants Essentials – Different Types of Reactors