Every nuclear power station in the UK today uses some variant of the same basic technology: a Pressurised Water Reactor (PWR). These reactors use water as both coolant and moderator, producing steam at roughly 285°C. That's fine for generating electricity. But it's physically incapable of doing what CFF needs.
Carbon Free Future is built around a different reactor: the HTGR — High-Temperature Gas-Cooled Reactor. And this single engineering choice is what makes the entire CFF concept possible.
An HTGR uses helium as its coolant instead of water. Helium is an inert noble gas — it doesn't react chemically with anything, doesn't become radioactive, and doesn't change phase (no boiling, no steam explosions). It's one of the safest coolants imaginable.
The key difference is temperature:
CFF uses HTSE — High-Temperature Steam Electrolysis — to split water into hydrogen and oxygen. HTSE needs steam at 700–850°C to work efficiently.
Here's the critical point:
Each CFF site has 48 HTGR modules arranged in 8 six-packs of 6:
This isn't theoretical. China's HTR-PM (High-Temperature Reactor — Pebble-bed Module) at Shidaowan is a working HTGR that connected to the grid in December 2021. It's the world's first commercial-scale HTGR and it proves the core technology works.
The HTR-PM uses pebble-bed fuel with helium coolant at 750°C — essentially the same temperature regime CFF proposes. China is already planning to scale this to larger multi-module configurations, validating the exact fleet approach CFF proposes for the UK.
| Feature | PWR (Hinkley) | HTGR (CFF) |
|---|---|---|
| Coolant | Water | Helium (inert gas) |
| Coolant exit temperature | ~285°C | 750°C |
| Steam temperature | ~280°C | ~700°C |
| HTSE-compatible? | No (400°C gap) | Yes (direct) |
| Hydrogen production | Impractical at scale | 2,072 t/day per site |
| Coolant phase change risk | Yes (steam explosions possible) | No (helium is always gas) |
| Modular potential | Limited (large custom vessels) | High (factory-built modules) |
| Passive safety | Requires active cooling | Walk-away safe (negative temp. coefficient) |
HTGRs have an inherent safety advantage. The fuel is encased in TRISO particles — tiny ceramic-coated spheres that can withstand temperatures over 1,600°C. The reactor has a negative temperature coefficient, meaning if it overheats, the nuclear reaction naturally slows down.
In a loss-of-coolant event, an HTGR doesn't melt down. It simply gets hot and then cools itself passively through radiation and conduction. No operator intervention required. No emergency cooling systems needed. This is "walk-away safe" — a term the nuclear industry uses specifically for this type of reactor.
CFF's original concept was based on PWRs. But engineering analysis revealed the fatal flaw: you simply cannot do industrial-scale hydrogen production with 285°C steam. The thermodynamics don't work.
The switch to HTGRs wasn't a preference. It was an engineering necessity. And it's what transforms CFF from a nuclear power programme into a complete industrial platform — producing hydrogen, electricity, water, heating, oxygen, and chemical feedstocks from a single integrated design.
That's not a power station. That's a national wealth engine.
Carbon Free Future is an independent proposal by DJ Waugh. It has no political or commercial affiliation.