Nuclear reactors a mile underground promise safe, cheap power
A proposal to place small nuclear reactors a mile underground in boreholes aims to cut costs by using rock as natural containment and passive water pressure instead of massive surface structures. Commenters debate whether deep drilling at the required diameter is truly economical, how such systems would handle cooling, maintenance and long‑term waste, and whether simply doing geothermal at similar depths would be better. Many argue that even if safety could be improved, nuclear still struggles to compete with rapidly falling costs for renewables plus storage, while others see underground siting as a way to reduce public opposition and geopolitical risks.
Cost and feasibility of deep drilling
- Multiple comments cite oil/gas well data: mile-deep, ~1 m diameter holes are routine; rough costs range from a few million dollars for a bare borehole to maybe tens of millions with casings and multiple shafts.
- Relative to multi‑billion‑dollar nuclear plants, drilling is seen by many as a small fraction of total capex, though mining engineers stress “digging is not cheap” and projects routinely overrun.
Comparison with geothermal
- Many ask: if you can drill a mile down, why not just do geothermal?
- Counterpoints: useful geothermal gradients aren’t available everywhere; some geothermal schemes need numerous wells, cool off in decades, or induce earthquakes; nuclear offers much higher power density per well and works in geologically “boring” regions.
- Others argue that if deep drilling became cheap, advanced geothermal might still be preferable because it avoids radioactivity.
Safety, groundwater, and waste
- Proponents: placing the reactor below any water table in solid rock provides natural containment; meltdowns would be isolated far from the biosphere; spent fuel could be “disposed” by backfilling the hole, similar to deep borehole disposal concepts.
- Skeptics: “solid rock” and “below any water table” are seen as hand‑wavey; deep groundwater exists and migration paths are poorly understood; long‑term stewardship and bankrupt operators are unresolved issues.
- Some note that an underground accident is likely less socially and physically disruptive than a surface plant accident, but want rigorous hydrogeological analysis.
Thermal and engineering challenges
- Concerns about heat loss and friction in a mile‑long heat exchanger, and the pumping energy needed to lift coolant against a 160‑bar water column.
- Questions about how to service the reactor and manage mile‑long high‑pressure pipes if the unit is hoisted to the surface.
- Some suggest putting turbines or secondary loops underground, but that increases complexity.
Nuclear vs renewables context
- Large side discussion: many argue new nuclear is too expensive and inflexible compared to rapidly improving wind/solar plus storage, and that “base load” is an outdated concept.
- Others argue nuclear’s safety record per kWh is strong, fossil fuels are far deadlier, storage is not yet sufficient, and political/regulatory barriers—rather than physics—drive nuclear costs.
Public perception and politics
- Some see burying reactors as a clever way to address fears and simplify containment/disposal.
- Others think it reinforces the idea that nuclear is uniquely dangerous and won’t sway entrenched opposition.