According to the International Atomic Energy Agency there are at least 100 research reactors in the world fueled by highly enriched ( weapons-grade / 90 % enrichment uranium ).
According to the International Atomic Energy Agency, one kilogram of soil typically contains the following amounts of the following three natural radioisotopes 370 Bq < sup > 40 </ sup > K ( typical range 100-700 Bq ), 25 Bq < sup > 226 </ sup > Ra ( typical range 10-50 Bq ), 25 Bq < sup > 238 </ sup > U ( typical range 10-50 Bq ) and 25 Bq < sup > 232 </ sup > Th ( typical range 7-50 Bq ).
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