- On October 1, 1997, the National Cancer Institute published a report on radioactive iodine (I- 131) in fallout following nuclear tests at the Nevada Test Site (NTS) during the 1950s and 60s. That report included estimated I-131 exposures and thyroid doses for populations in every county in the United States during the period of testing.rex.nci.nih.gov/massmedia/falloutcalculation.html