Every conversation about nuclear energy in the UK starts and ends with Pressurised Water Reactors — PWRs. That's what Hinkley uses. That's what Sizewell proposes. It's what the industry knows.
But PWRs are a 1950s design. They were built for submarines, then scaled up for power stations. They work. But they have fundamental engineering limitations that no amount of iteration can overcome.
CFF chose differently. Here's why that choice determines everything.
At 700–850°C, you can do things that are physically impossible at 285°C:
1. High-Temperature Steam Electrolysis (HTSE) Splitting water into hydrogen and oxygen. HTSE at 700°C+ is ~30% more efficient than low-temperature electrolysis because the heat does part of the thermodynamic work. This is how CFF produces 2,072 tonnes of hydrogen per day per site.
2. Thermochemical Water Splitting Future potential to split water using heat alone — no electricity needed. The sulphur-iodine cycle operates at 850°C. HTGRs are the only commercial reactor type that can reach these temperatures.
3. Process Heat for Industry Steelmaking, cement production, glass manufacturing, and chemical synthesis all need high-temperature heat. An HTGR can supply this directly. A PWR cannot.
4. District Heating with Massive Range CFF's Heat Halo pipes hot water at 130°C up to 15 km from each site, serving ~280,000 homes for £500/year. The higher source temperature means greater range and efficiency.
| Feature | PWR | HTGR |
|---|---|---|
| Coolant | Water (boils, flashes to steam) | Helium (inert, never changes phase) |
| Coolant pressure | 155 bar (2,250 psi) | 70 bar |
| Loss-of-coolant risk | Steam explosion possible | No phase change — impossible |
| Fuel type | Ceramic pellets in zirconium tubes | TRISO particles (ceramic-coated microspheres) |
| Fuel failure temp | ~1,200°C (cladding fails) | >1,600°C (TRISO intact at 1,800°C) |
| Passive safety | Requires active emergency cooling | Walk-away safe (negative temp coefficient) |
| Meltdown possible? | Yes (Three Mile Island, Fukushima) | No — physically impossible |
PWRs like the EPR are enormous. Each Hinkley reactor vessel weighs over 500 tonnes and must be fabricated on-site. The containment building is a one-off concrete structure.
HTGR modules are compact — 80 MWe each — and designed for factory production. CFF arranges 48 modules in 8 six-packs per site. Any six-pack can be taken offline for maintenance without affecting the other seven.
This is why CFF gets ~66 MWe per hectare compared to Hinkley's 18.6. Smaller modules, tighter packing, better output.
Because HTGR modules are standardised:
PWRs produce electricity. HTGRs produce a national industrial platform — electricity, hydrogen, water, heating, and chemical feedstocks from a single integrated design.
The reactor choice isn't a technical preference. It determines whether you build a power station or a national wealth engine.
Carbon Free Future is an independent proposal by DJ Waugh, a retired engineer from the North East of England.