Abstract: 7500-I A. Introduction
1. Occurrence and Significance
Radioiodine that results from testing nuclear devices or is released during the use and processing of reactor fuels is a major concern in radioactivity monitoring. Fission products may contain iodine-129 through iodine-135. Iodine-129 has a half-life of 1.6 × 107 years but a relatively low specific activity (1.73 × 10–4 Ci/g for 129I as compared to 1.24 × 105 Ci/g for 131I). The half-life of 131I is 8 d while for the other isotopes it is shorter (35 min to 21 h). At present, only 131I is likely to be found in water. When ingested or inhaled, it concentrates in the thyroid gland and may cause thyroid cancer.