Two questions about new generation of nuclear power

I was asked about the new generation of nuclear power. I decided to publish the answers here so others can benefit from them too.

The new generation of nuclear power is widely accepted to be the same as the Small Modular Reactors, or SMR’s. So I will answer assuming this is the case.

Question one:

What is the stage of planning new generation nuclear power plants? Where the planning/building of them has been the most advanced?

The first SMR plant is almost ready. China has built FOAK (First of a Kind) helium cooled pebble bed reactor called HTR-PM (High Temperature Reactor – Pebble bed Modular). It was meant to start within 2018 but difficulties in manufacturing the steam generators have led to some delays. They are now ready and the startup should happen any time soon.

The first modular reactor in the USA is the design of NuScale. Licensing process with the local authorities is almost ready. Construction works of the first 12 module power plant in Idaho will start within a few years and it should achieve commercial operation in 2026. Relatively short construction time will be achieved by doing most of the manufacturing works in a factory instead of on the site as usual.

Canadian based Terrestrial energy is designing a molten salt reactor called IMSR, Integral Molten Salt Reactor. Terrestrial energy have told entering the markets within two years.

I gave here three examples of the recent stage of SMR technology. There are several more vendors aiming to enter the market within the next decade. Here are two links I recommend to read if you want to find more information about SMR’s.

World Nuclear Association: Small Nuclear Power Reactors

Wikipedia: Small modular reactor

Question two:

What are the risks of next generation nuclear power?

The most important thing to understand about advanced nuclear is the difference in safety principles compared with traditional nuclear power plants. A big nuclear power plant is safe. The safety has been achieved with many different safety systems which are all designed to cool down the core in a case of emergency. For example, the new Olkiluoto 3 has four different emergency cooling systems. One system out of four is enough to keep the core in a safe condition. So three out of four systems could fail and the plant will still remain in a safe condition.

Small SMR’s are inherently safe without any extra safety systems. They rely on passive systems to cool the core. For example, NuScale will place the reactor modules in a large pool of water. In a case of emergency, the water already in place is enough to keep reactor cores safe. This happens with no efforts from the plant personnel and even without electricity or any active safety systems.

At some point, the water in the pool starts to boil. Outgoing steam transfers the heat produced by decay heat of the core. When all of the water has boiled off, decay heat has reached a level low enough to be air-cooled for an indefinite amount of time.

Conclusion: Both traditional big nuclear power plants and SMR’s are safe. However, the small size of SMR’s makes it possible to design them to be inherently safe without any separate safety systems. This is better in a situation when all power at the plant is lost. For example, the Fukushima accident would not have happened with an inherently safe nuclear power plant. What happened was that electricity at the site was lost so cooling water pumps did not work and the reactor cores melted.

Inherently safe is often called ”walk away safe”. It means that the personnel could walk away from the plant and it remains safe by its own.

I think the biggest risk with next-generation nuclear power is, that it will not be built fast enough. That we don’t succeed to make people and politicians understand, that we really don’t have enough alternatives to produce low carbon electricity and heat in a reliable way without nuclear power. A total climate change is a far more serious risk than nuclear power could ever be.

  1. HTR-PM steam generator passes pressure tests
  2. Current status and technical description of Chinese 2 × 250 MW th HTR-PM demonstration plant
  3. NuScale
  5. Terrestrial energy


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