Question: 1 what is the approximate half-life of uranium-238?
Answer: Around 99.284% of natural uranium's mass is uranium-238, which has a half-life of 1.41×1017 seconds (4.468×109 years, or 4.468 billion years). Due to its natural abundance and half-life relative to other radioactive elements, 238U produces ~40% of the radioactive heat produced within the Earth.