* All of the [[noble gas]]es, including [[krypton]] and [[xenon]], contained within the reactor were released immediately into the atmosphere by the first steam explosion.<ref name="OECD02-Ch2"/> The atmospheric release of [[xenon-133]], with a half-life of 5 days, is estimated at 5200 PBq.<ref name="OECD02-Ch2"/>
* 50 to 60% of all core [[radioiodine]] in the reactor, about 1760 [[becquerel|PBq]] ({{val|1760|e=15|u=becquerels}}), or about {{convert|0.4|kg|lb}}, was released, as a mixture of [[Sublimation (phase transition)|sublimed]] [[vapor|vapour]], solid particles, and [[Organoiodine compound|organic iodine]] [[Chemical compound|compounds]]. Iodine-131 has a half-life of 8 days.<ref name="OECD02-Ch2"/>
* 20 to 40% of all core [[caesium-137]] was released, with estimates ranginranging from 70 PBq<ref>{{Cite journal |last=Evangeliou |first=Nikolaos |last2=Hamburger |first2=Thomas |last3=Cozic |first3=Anne |last4=Balkanski |first4=Yves |last5=Stohl |first5=Andreas |date=2017-07-20 |title=Inverse modeling of the Chernobyl source term using atmospheric concentration and deposition measurements |url=https://acp.copernicus.org/articles/17/8805/2017/ |journal=Atmospheric Chemistry and Physics |language=English |volume=17 |issue=14 |pages=8805–8824 |doi=10.5194/acp-17-8805-2017 |issn=1680-7316}}</ref> to 85 PBq in all.<ref name="OECD02-Ch2"/><ref>{{cite web |url=http://www.zamg.ac.at/aktuell/index.php?seite=1&artikel=ZAMG_2011-03-24GMT11:24 |title=Unfall im japanischen Kernkraftwerk Fukushima |website=[[Central Institution for Meteorology and Geodynamics]] |language=de |date=24 March 2011 |access-date=20 August 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110819093109/http://www.zamg.ac.at/aktuell/index.php?seite=1&artikel=ZAMG_2011-03-24GMT11:24 |archive-date=19 August 2011 }}</ref> Caesium was released in [[particulate|aerosol]] form; caesium-137, along with [[isotopes of strontium]], are the two primary elements preventing the Chernobyl exclusion zone being re-inhabited.<ref name="stanford1">{{cite web |url=http://large.stanford.edu/courses/2012/ph241/wessells1/ |title=Cesium-137: A Deadly Hazard |last=Wessells |first=Colin |date=20 March 2012 |website=[[Stanford University]] |access-date=13 February 2013 |archive-url=https://web.archive.org/web/20131030013102/http://large.stanford.edu/courses/2012/ph241/wessells1/ |archive-date=30 October 2013 |url-status=live }}</ref> {{val|8.5|e=16|u=Bq}} equals 24 kilograms of caesium-137.<ref name="stanford1"/> Cs-137 has a half-life of 30 years.<ref name="OECD02-Ch2"/>
* [[Tellurium-132]], half-life 78 hours, an estimated 1150 PBq was released.<ref name="OECD02-Ch2"/>
* An early estimate for total [[nuclear fuel]] material released to the environment was {{val|3|1.5}}%; this was later revised to {{val|3.5|0.5}}%. This corresponds to the atmospheric emission of {{convert|6|t|LT ST}} of fragmented fuel.<ref name="OECD1995" />
