Amount of Tritium Existing in Nature
Tritium (3H) is a radioisotope of hydrogen (with a half-life of about 12.3 years) and emits weak radiation (β-particles) (p.79 of Vol. 1, "Characteristics of Tritium"). In nature, about seventy quadrillion (7 × 1016) Bq of tritium is produced annually by cosmic rays, etc. on earth. In the past nuclear testing (1945 to 1963), tritium of 1.8 to 2.4 × 1020 Bq was released. In addition, tritium is discharged daily from facilities such as nuclear power stations around the world and the annual amount of tritium released from nuclear power stations around the world is 2 × 1016 Bq. Before the Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi NPS Accident, the annual amount of tritium released from nuclear power stations all over Japan was 380 × 1012 Bq (which is the average annual amount discharged into the ocean during the five years before the accident). The total amount of tritium existing in nature is estimated to be 1 to 1.3 × 1018 Bq. The released tritium exists mostly as hydrogen that makes up water molecules and it is also contained in water vapor in the atmosphere, rainwater, sea water and tap water. The annual amount of tritium contained in the precipitation in Japan is estimated to be about 223 × 1012 Bq.
- Included in this reference material on March 31, 2021