Okloa: Earth's Own Reactor
Nuclear & Particle Physics arc, page 176 of 193. Back to The Pixelated Physics Universe
Who they are
Okloa sleeps in the Gabon uranium rock and wakes every few hours. She was a working nuclear reactor two billion years ago.
Okloa is a character of the Nuclear & Particle Physics arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.
The physics
About 2 billion years ago, uranium was richer in U-235 (about 3.7%), because U-235 decays faster than U-238. With groundwater slowing the neutrons, ore at Oklo sustained fission chain reactions, running about 30 minutes on and 2.5 hours off as the water boiled away and returned.
$$ \begin{gathered} \text{today: } 0.7202\%\ {}^{235}\mathrm{U}; \quad \text{Oklo (1972): } 0.7171\%; \quad \text{some zones: } 0.296\% \\ T_{1/2}({}^{235}\mathrm{U}) = 0.704\ \mathrm{Gyr}, \qquad T_{1/2}({}^{238}\mathrm{U}) = 4.468\ \mathrm{Gyr} \\ 2\ \text{billion years ago: } \approx 3.7\%\ {}^{235}\mathrm{U} \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| ${}^{235}\mathrm{U},\ {}^{238}\mathrm{U}$ | uranium isotopes | 1 |
| $\%$ | atom percent of U-235 in natural uranium | 1 |
| $T_{1/2}$ | half-life | s |
| $\mathrm{Gyr}$ | billion years, about 3.16 × 10¹⁶ s | s |
Honest caveat: It never exploded like a bomb, and Oklo was not the only natural reactor.
Sources
- Nature (1975) Nuclear reactor in the jungle, Nature 256, 264
- Meshik, Hohenberg & Pravdivtseva (2004) Record of Cycling Operation of the Natural Nuclear Reactor in the Oklo/Okelobondo Area in Gabon, Phys. Rev. Lett. 93, 182302
Crossovers
Okloa meets Corekeeper (Strong Nuclear Force / Nuclear Binding). Corekeeper's binding curve explains Okloa: splitting heavy uranium nuclei into medium ones releases energy, because the products are more tightly bound per nucleon.
Okloa meets Reinessa (Catching the Ghost 1956). Reinessa caught antineutrinos from a man-made reactor. Okloa was a natural reactor two billion years ago, and its fission products are still in the rock.
Okloa meets Roentgenor (X Marks the Unknown). Okloa's reactor ran on uranium. Roentgenor's X-rays opened the door to finding radioactivity: Becquerel's discovery in uranium came months later.
Wear the lore
- Okloa – Earth's Own Reactor Physics T-Shirt
- Related infographic poster: Chicago Pile-1 – Plate 049 Physics Poster
Concept keywords: Earth's Own Reactor, Okloa, Nuclear & Particle Physics, physics lore, Pixelated Physics