My curiosity was sparked by reports that Iran had enriched its uranium stockpile to 60%. What did it mean, I wondered? Natural Uranium Composition Natural uranium ore consists of approximately 0.7% uranium-235 (U-235) (the primary fissile isotope) and 99.3% uranium-238 (U-238) (a fertile isotope), plus trace uranium-234. U-235 sustains chain reactions directly, but the vast … Continue reading Uranium: Mark shares his newfound knowledge.