Vienna, 20 Feb. 2017

In response to multiple inquiries over the past 48 hours, the CTBTO reports that the radionuclide (RN) stations of the International Monitoring System (IMS) are working normally.  The radioactive isotope Iodine-131 is produced by nuclear fission in nuclear explosions, power reactors, and industrial and medical isotope facilities.  It has an half-life of 8.02 days.  It is one of the radioactive isotopes that the 80 planned stations of CTBTO’s IMS continuously monitor for indications of nuclear test explosions.  Because of its wide industrial and medical uses, the CTBTO compares I-131 measurements against local historical levels.  Although I-131 is frequently detected at trace levels by the stations of the IMS all over the world, no detections above typical local historical levels have been observed in the past several months.

If a nuclear test were to take place that releases I-131 it would also be expected to release many other radioactive isotopes.   Thus the CTBTO measures many isotopes.  No other nuclear fission isotopes have been measured at elevated levels in conjunction with I-131 in Europe so far.

https://newsroom.ctbto.org/2017/02/20/media-advisory/